key: cord-314422-u2elzgl8 authors: bothra, atul; das, seujee; singh, mehak; pawar, manoj; maheswari, anshu title: retroauricular dermatitis with vehement use of ear loop face masks during covid19 pandemic date: 2020-06-03 journal: j eur acad dermatol venereol doi: 10.1111/jdv.16692 sha: doc_id: 314422 cord_uid: u2elzgl8 the covid‐19 pandemic forged theexponential use of masks of various kinds, not just by health workers but also by general population as a personal protective equipment (ppe). although contact dermatitis due to ppe is well reported, mask induced dermatitis is a relatively unexplored phenomenon. in this article, we report a preliminary data of patients experiencing retroauricaular dermatitis due to ear loop face masks. this article is protected by copyright. all rights reserved to the editor: the covid-19 pandemic forged theexponential use of masks of various kinds, not just by health workers but also by general population as a personal protective equipment (ppe). although contact dermatitis due to ppe is well reported, mask induced dermatitis is a relatively unexplored this article is protected by copyright. all rights reserved phenomenon. in this article, we report a preliminary data of patients experiencing retroauricaular dermatitis due to ear loop face masks. documented. 4 komerickiet.al reported cocopropylenediamin-guanidium-diacetate , used to disinfect medical instruments and apparatus, responsible for acd to non-disposable face masks. 5 similar effects on the face by ppe in healthcare workers managing covid-19 cases has been documented, but no study has elaborated the retroauricular involvement. 6 frequent frictions due to the straps, this article is protected by copyright. all rights reserved trapping of sweat, use of disinfectant to reuse masks, application of dyes to colour homemade masks are frequent causes of dermatitis using ear loop face masks. the strap material including thermoelastic polymer, rubber, latex etc. further leads to contact dermatitis. moreover, the masks can cause exacerbation of pre-existing dermatoses. the authors would like to suggest the use of headband face masks for health care professionals using the mask for prolonged periods. the general population, using homemade face masks should use cotton cloth based masks with gaiters of appropriate elasticityand avoid any disinfectant application. persons with preexisting dermatoses including atopic dermatitis, seborrheic dermatitis and chronic urticaria need to take special precautions and use of disposable surgical masks should be encouraged. donning of masks should be done after proper absorption of the emollient to prevent leeching of strap polymers. adverse skin reactions to personal protective equipment against severe acute respiratory syndrome-a descriptive study in singapore skin reactionsfollowing use of n95 facial masks surgical mask contact dermatitis and epidemiology of contact dermatitis in healthcare workers. current allergy & clinical immunology accepted article this article is protected by copyright. all rights reserved occupational allergic contact dermatitis in an obstetrics and gynecology resident face dermatitis from contaminants on a mask for anaesthesia personal protective equipment induced facial dermatoses in healthcare workers managing covid-19 cases acknowledgement-the patients in this manuscript have given written informed consent to the publication of their case details. key: cord-304170-cmeiqvnp authors: van straten, b.; de man, p.; van den dobbelsteen, j.; koeleman, h.; van der eijk, a.; horeman, t. title: sterilization of disposable face masks by means of standardized dry and steam sterilization processes; an alternative in the fight against mask shortages due to covid-19 date: 2020-04-08 journal: j hosp infect doi: 10.1016/j.jhin.2020.04.001 sha: doc_id: 304170 cord_uid: cmeiqvnp nan b. van straten 1,3 , p. de man 2 , j. van den dobbelsteen 1 , h. koeleman 2 , a. van der eijk 4 , t. horeman 1 the covid-19 pandemic causes imminent shortages of face masks in hospitals globally. in preparation for that scarcity we performed a study to investigate the possibility of reprocessing disposable ffp2 face masks in order to verify their re-usability with a method that could be applied in practice using already available equipment. therefore single use ffp2 masks (type 1862+3mtm) were sterilized with a 15-minute procedure at 121 ⁰c, using a dry sterilization process as well as with a regular steam process with the masks in sterilization/laminate bags. the effectiveness of these processes are sufficient to inactivate the coronavirus based on knowledge of inactivation of such viruses. [1, 2] a blind comparison of unused sterilized masks was performed with respect to visual inspection, consistency, face fit and breathing resistance. the results of this comparison were that the investigators were unable to distinguish unused new (slightly curved and folded) masks from reprocessed sterilized masks. we then tested the functionality of the unused and sterilized masks in several ways. first of all permeability properties for bacteria were tested by spraying a bacteria solution of staphylococcus epidermidis (atcc 12228) on the masks while air was being drawn through the masks. unused and multiple sterilized masks showed no differences in the amount of passed bacteria (data not shown). in these experiments it was also observed that the reprocessing procedures of the masks did not appear to affect the water-repellent mask properties. we then assessed pressure/flow and performed particle tests. before sterilization, the batches were individually packed in laminate bags and sterilized with steam sterilization by means of 121 ⁰c in getinge autoclaves and in combination with permeable laminate bags, halyard type clfp150x300wi-s20. the autoclaves were activated on a 121 ⁰c program and validated accordingly. after sterilization, the samples were tested at delft university of technology and at reinier de graaf hospital, and benchmarked with new mouth masks. a custom test set-up was built to measure the pressure drop over the maskers and outflow with regard to the permeability of the masks. a direct comparison between new and sterilized masks did not show substantial differences. finally, the filtration capacity of the masks was evaluated using a calibrated lighthouse solair 3200 particle counter (lighthouse, san francisco). it was shown that the mask permeability of small particles did not change after multiple heat sterilization procedures (table i) . we openly shared our positive experiences with the steam sterilization process with other hospitals in the netherlands that are also preparing for the outbreak. we were informed that their attempts to steam sterilize mouth masks at 134⁰c gave poor results as masks started to deform and became sticky while the elastics lost its resilience. in addition, we tested gamma radiated masks this process did hamper the filter capacity (table i) . the results of our experiences and experiments indicate that our sterilization process did not influence the functionality of the masks tested. in case of an acute shortage of ffp2 masks, steam sterilization (e.g. in laminate sterilization wrappings) of used masks at 121 ⁰c in laminated bags, is a simple, useful cost-effective and quick procedure that can be used to make used masks available for safe reuse. the sterilization process of available standard autoclaves in hospitals may have to be adjusted in order to use this sterilization method. we also emphasise that we performed these experiments with 3m masks only. however, our method seems to be a potentially useful way to reuse mouth masks; other hospitals facing a shortage of masks may wish to test and validate this approach to reusing masks. coronavirus disinfection in histopathology inactivating porcine coronavirus before nuclei acid isolation with the temperature higher than 56 °c damages its genome integrity seriously key: cord-332532-419wnq7x authors: lam, stanley kam ki; hung, maria shuk yu; chien, wai tong title: uncertainty surrounding the use of face masks in the community amid the covid-19 pandemic date: 2020-05-16 journal: int j nurs stud doi: 10.1016/j.ijnurstu.2020.103651 sha: doc_id: 332532 cord_uid: 419wnq7x nan this article has not been published and is not under consideration for publication elsewhere. the authors declared no conflicts of interest with respect to the authorship and/or publication of this article. the authors received no financial support for the research and/or authorship of this article. the pandemic of the 2019 coronavirus disease , which was previously coined as "wuhan pneumonia", is wreaking havoc worldwide since the first reported case in china in december 2019 (zhu et al., 2020) . as of april 2020, there have been more than three million confirmed cases around the world, affecting the health of people in 210 countries and territories (centre for health protection, 2020). in addition to the public health impact of the disease, this large-scale public health crisis has inflicted immeasurable damage on the global economy due to the nationwide shutdown and home confinement directives that prohibit international and local economic activities. the world health organisation (who) has declared the outbreak of covid-19 a pandemic on 11 march 2020, following with advice on infection control measures for the public such as hand hygiene, respiratory etiquette, and the usage of protective equipment. however, there is lingering uncertainty among the general public worldwide about the use of face masks amid the pandemic. one of the vital areas of uncertainty that is still hanging over the public relates to whether face masks should be used in the community as a preventive measure. there is a consensus among governments and public health agencies that the use of medical masks, also known as surgical masks, is an effective measure for source control and is therefore recommended for symptomatic individuals and healthcare workers (chughtai et al., 2020) . however, whether the use of face masks could protect healthy individuals against the pathogen and reduce the risk of infection by covid-19 has remained unclear. on one hand, the who states that wearing medical masks is not considered necessary for healthy persons unless they are involved in taking care of people with suspected or confirmed covid-19 infection (who, 2020a). on the other hand, it proclaims that "potential advantages of the use of masks by healthy people in the community setting include reducing potential exposure risk from an infected person during the "pre-symptomatic" period or if an infected person is asymptomatic" (who, 2020b). while it is understandable that conserving the use of masks in the community could help to reserve masks for frontline healthcare workers, such inconsistent information provided by the who might exaggerate worries among the public and further exacerbate the shortage of essential goods and resources. indeed, panic buying behaviours in the community has been widely reported amid the covid-19 pandemic that people are stocking up on masks, hand sanitisers, and even toilet paper. since there is limited 3 empirical evidence for the effectiveness of universal community masking in protecting the health of the public during an outbreak of novel respiratory infectious diseases, further research in this area is imperative. another uncertainty among the public is about the selection of face masks. during the covid-19 pandemic, the quality of medical masks has been a subject of public concern. there are a variety of metrics used to evaluate face mask performances from different aspects. common metrics include particle filtration efficiency (pfe), bacteria filtration efficiency (bfe), virus filtration efficiency (vfe), and filtering face pieces (ffp). while even healthcare workers could be unfamiliar with these metrics, limited official information has been provided to assist the public in selecting the appropriate medical masks. also, there is a lack of consensus regarding the standards of medical masks. for instance, the american society for testing and materials (astm) f2100 grading (level 1, 2, and 3) is frequently used in the united states, while in europe the en14683 standard (type 1, 2, and 2r) is most common. there is a pressing need for health authorities and agencies to offer standardised guides to the general public on choosing suitable face masks. the above-mentioned issues regarding the use of face masks in the community have been a recurring problem during infectious disease outbreaks. indeed, these had been raised during the severe acute respiratory syndrome (sars) outbreak in the year 2003 (syed et al., 2003) . unfortunately, the issues are yet to be addressed 17 years afterwards. there is an urge to fill these gaps through coordinated research and administrative efforts among governments and healthcare organisations in combating the current covid-19 pandemic. funding sources: none. we declare no competing interests. countries/areas with reported cases of coronavirus disease-2019. retrieved from centre for health protection policies on the use of respiratory protection for hospital health workers to protect from coronavirus disease (covid-19) journey through an epidemic: some observations of contrasting public health responses to sars coronavirus disease (covid-19) advice for the public: when and how to use masks. retrieved from world health organisation advice on the use of masks in the context of covid-19. retrieved from world health organisation 2020) a novel coronavirus from patients with pneumonia in china key: cord-292201-e7k7gn9q authors: fodjo, joseph nelson siewe; pengpid, supa; villela, edlaine faria de moura; van, thang vo; ahmed, mohammed; ditekemena, john; crespo, bernardo vega; wanyenze, rhoda k; dula, janeth; watanabe, takashi; delgado-ratto, christopher; driessche, koen vanden; van den bergh, rafael; colebunders, robert title: mass masking as a way to contain covid-19 and exit lockdown in lowand middle-income countries date: 2020-07-17 journal: j infect doi: 10.1016/j.jinf.2020.07.015 sha: doc_id: 292201 cord_uid: e7k7gn9q in new guidelines published on june 5(th) 2020, the world health organization (who) recommends that in areas with ongoing covid-19 community transmission, governments should encourage the general public to wear face masks in specific situations and settings as part of a comprehensive approach to suppress covid-19 transmission. recent online surveys in 206,729 persons residing in nine lowand middle-income countries showed that 32.7%-99.7% of respondents used face masks with significantly differences across age groups and sexes. targeted health promotion strategies and government support are required to increase mask use by the general population. in new guidelines published on june 5 th 2020, the world health organization (who) recommends that in areas with ongoing covid-19 community transmission, governments should encourage the general public to wear face masks in specific situations and settings as part of a comprehensive approach to suppress covid-19 transmission. recent online surveys in 206,729 persons residing in nine low-and middle-income countries showed that 32.7%-99.7% of respondents used face masks with significantly differences across age groups and sexes. targeted health promotion strategies and government support are required to increase mask use by the general population. we read with interest the research work of cheng and collaborators on community-wide mask use for coronavirus disease 2019 (covid-19) control. 1 indeed, face masks are now recommended by the world health organization (who) to prevent covid-19 transmission, according to new guidelines published on june 5 th 2020. 2 the new recommendations state that in areas with ongoing covid-19 community transmission, governments should encourage the general public to wear masks in specific situations and settings where physical distancing cannot be achieved, as part of a comprehensive approach to suppress covid-19 transmission. 2 long before the issuance of these guidelines, many asian countries were already using face masks and this potentially contributed to the rapid containment of covid-19 in these countries. 1, 3 outside of asia, routine use of masks by the general population is rare. most european countries were applying previous who recommendations whereby face masks were reserved for covid-19 patients, carers or healthcare workers. moreover, there were fears that promoting mass masking could aggravate the shortage of face masks among healthcare workers, especially as cloth (fabric) masks were not initially considered useful for covid-19 prevention in europe. 3 the director-general of the chinese center for disease control and prevention went as far as warning europe and the united states of america (usa) regarding the risks of not enforcing routine wearing of face masks by the general public. 4 most low-and middle-income countries (lmic) outside of asia also initially deprioritised masks and focused on lockdown strategies in an attempt to "flatten the curve". however, lockdowns are associated with major socio-economic losses, which may further exacerbate the precarious conditions in resource-limited settings, and thus compliance to such strategies is implausible (particularly among populations who depend on daily labour for their income). furthermore, in highly congested settings such as urban slums or refugee camp settings, lockdowns and/or measures of physical distancing are not feasible. the benefits of isolation-based strategies are also limited, given that pre-and asymptomatic individuals are potentially contagious for covid-19. 5 we thus welcome the who recommendations to use face masks in the general population, as an important component of strategies to stop the epidemic and/or exit the lockdowns, particularly in lmic. recent evidence supports a predominantly airborne transmission route for covid-19, and strongly encourages face mask use in public to prevent inter-human transmission. 6 modelling studies estimate that the covid-19 pandemic can be brought to an end if 80% of the population would wear a surgical mask. 7 moreover, mass masking could also alleviate fears that prevent people from seeking medical care for non-covid-19 conditions, limiting the collateral damage of the covid-19 pandemic. on the downside, improper mask use may inadvertently increase covid-19 transmission via indirect contact routes with the mask serving as a fomite. mass making may also produce a false sense of security leading to reduced adherence to other preventive measures such as hand hygiene. 3 finally, surgical masks pose an environmental threat if discarded inappropriately due to their plastic content. 8 it is therefore paramount to monitor both compliance and user practices in ensuring the effectiveness of masks in covid-19 control. between march and june 2020, an international consortium (www.icpcovid.com) organised online surveys in lmic to monitor adherence to covid-19 preventive measures, including face mask use. only data of consenting respondents who were at least 18 years old and who self-identified as either male or female were analysed 8 in countries where masking was mandatory or highly encouraged by the government during the early phases of the covid-19 outbreak, adherence rates were >90%. in brazil, the initial low adherence to face mask use together in combination with little or no confinement measures may have contributed to the high covid-19 mortality in this country. where data were available on the type of mask used, reusable cloth masks (more cost-beneficial and environmentally friendly than surgical masks) were the most frequent accounting for 4,413/8,636 (51.1%) of all mask types. our study shows that even in countries where no pre-existing culture of mask use existed, high uptake of mass masking was feasible. the differential rate of uptake between sexes and age groups, as shown in table 2 , suggests that targeted health promotion strategies to (further) stimulate mask use may need to be developed, and that covid-19 prevention strategies need to be contextualized to each setting/population. as there is currently no effective vaccine or treatment against covid-19, the mass masking policy of the who is a prudent move for covid-19 prevention. we therefore urge the public health and scientific communities to invest in strategies to promote mask use among all tiers of the population, and to further build the evidence-base for optimal covid-19 prevention strategies. the authors declare no conflicts of interest. rc receives funding from the european research council (grant number 671055). all participants provided an informed e-consent (checkbox) before submitting their data anonymously. rc conceived the surveys and drafted the initial manuscript; jnsf cleaned and analysed the data, and edited the initial draft; all authors participated in data collection, critical review and approval of the final manuscript. the role of community-wide wearing of face mask for control of coronavirus disease 2019 (covid-19) epidemic due to sars-cov-2 advice on the use of masks in the context of covid-19: interim guidance rational use of face masks in the covid-19 pandemic. the lancet respiratory medicine not wearing masks to protect against coronavirus is a 'big mistake,' top chinese scientist says temporal dynamics in viral shedding and transmissibility of covid-19 identifying airborne transmission as the dominant route for the spread of covid-19 mathematical assessment of the impact of non-pharmaceutical interventions on curtailing the 2019 novel coronavirus discarded covid 19 gear: a looming threat hand hygiene, and influenza among young adults: a randomized intervention physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis. the lancet we thank the following icpcovid research team members in the different countries who were involved in the local organisation of the surveys: key: cord-354127-sb8tovy2 authors: de abreu, andrea pio; moura, josé andrade; delfino, vinicius daher alvares; palma, lilian monteiro pereira; do nascimento, marcelo mazza title: recommendations from the brazilian society of nephrology regarding the use of cloth face coverings, by chronic kidney patients in dialysis, during the new coronavirus pandemic (covid-19) date: 2020-08-26 journal: j bras nefrol doi: 10.1590/2175-8239-jbn-2020-s103 sha: doc_id: 354127 cord_uid: sb8tovy2 these recommendations were created after the publication of informative note 3/2020cggap/desf/saps/ms, of april 4, 2020, in which the brazilian ministry of health recommended the use of a cloth mask by the population, in public places. taking into account the necessary prioritization of the provision of personal protective equipment (ppe) for patients with suspected or confirmed disease, as well as for healthcare professionals, the sbn is favorable concerning the wear of cloth masks by chronic kidney patients in dialysis, in public settings, except in the dialysis setting. the present recommendations have eleven items, related to this rationale, the procedures, indications, contraindications, as well as appropriate fabrics for the mask, and hygiene care to be adopted. these recommendations may change, at any time, in the light of new evidence. as presentes recomendações foram elaboradas após a publicação da nota informativa nº 3/2020 cggap/desf/saps/ms, em 4 de abril de 2020, na qual o ministério da saúde recomenda o uso de máscara de pano por toda a população, em locais públicos. levando-se em consideração a necessária priorização do fornecimento de equipamentos de proteção individual (epis) para pacientes com suspeita ou confirmação da doença, assim como para profissionais de saúde, a sociedade brasileira de nefrologia (sbn) posicionou-se favoravelmente ao uso de máscaras de pano por pacientes renais crônicos em diálise, em ambientes públicos, exceto no ambiente da diálise. as presentes recomendações englobam onze itens relativos ao que é racional para posicionamento, procedimentos, indicações, contraindicações, assim como tecidos apropriados para confecção e os cuidados de higiene a serem adotados. essas recomendações poderão ser modificadas a qualquer momento, à luz de novas evidências. these recommendations were created after the publication of informative note 3/2020-cggap/desf/saps/ms, of april 4, 2020, in which the brazilian ministry of health recommended the use of a cloth mask by the population, in public places. taking into account the necessary prioritization of the provision of personal protective equipment (ppe) for patients with suspected or confirmed disease, as well as for healthcare professionals, the sbn is favorable concerning the wear of cloth masks by chronic kidney patients in dialysis, in public settings, except in the dialysis setting. the present recommendations have eleven items, related to this rationale, the procedures, indications, contraindications, as well as appropriate fabrics for the mask, and hygiene care to be adopted. these recommendations may change, at any time, in the light of new evidence. severe acute respiratory syndrome, coronavirus infection; covid-19. 2. the cloth mask can prevent the spread of droplets expelled from the nose or mouth of people in the environment, acting as a mechanical barrier, thus reducing spread of the disease by asymptomatic or pre-symptomatic infected people, who can transmit the virus, especially in places of community transmission, and where measures of social distance are difficult to follow. nonetheless, these masks do not protect healthy individuals from contracting the virus 1,2 . patients wearing masks during the pandemic 1. considering the scarcity of personal protective equipment (ppe), the sbn recommends that all asymptomatic chronic renal patients, as well as the general population, should wear protection masks, based on recommendations from the ministry of health (mh), through informative note 3/2020-cggap/desf/ saps/ms1. 3 . we recommend that all chronic kidney patients on dialysis wear a cloth mask when going out for essential activities and during transportation to the dialysis clinic. the use of the mask aims to reduce the spread of the virus by asymptomatic patients in these environments. 4. patients with covid-19 infection suspicion or confirmation should wear a surgical mask, as well as adopt other precautionary measures already described in the sbn good practice recommendations 3 . even though there is a shortage of ppe, there is no evidence to support the recommendation for the use of cloth masks within dialysis centers. there is a possibility of contamination at the site, favoring the spread of the virus; concurrently, we know understood that recommending the use of surgical masks by all asymptomatic patients while on dialysis may worsen the current situation of ppe scarcity. healthcare professionals, employees and patients with suspected or confirmed infection must have priority on having masks. this recommendation may change, depending on the effective supply of these materials in the country. 6. the fabrics recommended for making a mask are, in decreasing order of their ability to filter viral particles: a) vacuum cleaner bag fabrics; b) cotton (composed of 55% polyester and 45% cotton); c) cotton fabric (such as 100% cotton t-shirts); and d) pillowcases of antimicrobial tissue 1 . 7. according to guidelines from the mh, some precautions need to be taken regarding the use of the fabric masks. the instructions for making them and hygiene measures are included in the technical note from the mh, available at: <https: // www. saude.gov. br/images/pdf/2020/april/04/1586014047102-nota-informativa.pdf>. 8. hereby, we stress some recommendations provided by the mh link (item 6) regarding the use of cloth masks: 8.1 the mask should be changed whenever there is dirt or moisture. chronic kidney patients on hemodialysis should calculate the number of masks required, depending on the time spent traveling to the clinic, and the return home. it is estimated that each mask can be used for a period of two hours. 8.2 the use of the mask is for one individual only, so the patient should not share it, even if it is sanitized. 8.3 upon leaving the dialysis clinic, the patient must be able to put on the mask without assistance. healthcare professionals should not assist the patients in this, due to the risk of contamination. 8.4 when arriving at the clinic, the used mask must be removed and packed in a plastic bag exclusively for that purpose, and should not be kept in the same compartment (bag, backpack) as the plastic bag that houses the clean mask that will be used on the return home. 8.5 when arriving home, the patient must clean the masks according to the guidelines contained in the mh technical note: immerse the mask in a container with drinking water and bleach (2.0 to 2.5%) for 30 minutes. the dilution ratio is 1 part of bleach to 50 parts of water (for instance: 10 ml of bleach to 500 ml of drinking water). after the immersion time, rinse the mask under running water and wash it with soap and water. after washing the mask, wash your hands with soap and water. the mask must be dry for reuse. after drying the mask, iron it with a hot iron and put it in a plastic bag 1 . 9. it is important to maintain the other preventive measures already recommended, such as social distance on days when hemodialysis is not performed, avoid touching the eyes, nose and mouth, in addition to hand hygiene with water and soap or 70% alcohol gel. 1, 3 10. cloth masks should not be worn by people who have difficulty breathing, are unconscious and unable to remove the mask without assistance. based on clinical criteria, the nephrologist will be able to evaluate other possible contraindications. 11. these recommendations may change at any time, in the light of new evidence. in this sense, one should look for possible updates. nota informativa nº 3/2020-cggap/desf/saps/ms center for disease control and prevention. recommendation regarding the use of cloth face coverings, especially in areas of significant community-based transmission recomendações de boas práticas da sociedade brasileira de nefrologia às unidades de diálise em relação à pandemia do novo coronavírus (covid-19) infectologists and members of the brazilian society of infectious diseases josé david urbaéz brito and ana verena almeida mendes collaborated in the review of this recommendation. key: cord-326039-pnf2xjox authors: seale, holly; dwyer, dominic e.; cowling, benjamin j.; wang, quanyi; yang, peng; macintyre, c. raina title: a review of medical masks and respirators for use during an influenza pandemic date: 2009-08-18 journal: influenza other respir viruses doi: 10.1111/j.1750-2659.2009.00101.x sha: doc_id: 326039 cord_uid: pnf2xjox nan to the editor: on 11 june 2009, the world health organisation (who) raised the influenza pandemic alert to level 6 (defined as 'sustained community level outbreaks in at least one other country in another who region') because of the emergence of a novel influenza a ⁄ h1n1 subtype. 1 australia's first laboratory confirmed case of pandemic (h1n1) 2009 virus, a nsw woman who had visited los angeles, was reported in the second week of may 2009. within a month, 1336 laboratory confirmed cases had been identified, the majority of them in victoria, rising to nearly 20 000 australia-wide by the end of july. given the lack of a specific vaccine against the pandemic (h1n1) 2009 virus, mitigation measures in australia have so far focused on identifying, treating, and isolating people who have the disease, and educating the public about the steps that individuals can take to reduce transmission. antiviral medications have been deployed as both treatment and prophylaxis. clinical trials of the pandemic (h1n1) 2009 vaccine are currently underway; however, it is unclear when and to whom the vaccine will be made available. healthcare workers (hcws) and those on the 'front line' will be the first to be vaccinated; there will be a lag time for members of the general public. non-pharmacological public health interventions including use of face masks are therefore likely to play a vital role in mitigating disease spread, particularly in developing countries. medical masks are unfitted devices worn by an infected person, hcw or member of the public to reduce transfer of potentially infectious respiratory tract material between individuals. they are designed to be disposable. surgical masks are specifically designed to protect patients from contamination of wounds during surgical procedures. in contrast, a respirator is a fitted device that protects the wearer against inhalation of harmful contaminated material. respirators can be disposable or reusable and are recommended for use in high-risk activities (e.g. aerosolgenerating procedures) in healthcare settings. the national institute for occupational safety and health (niosh) regulates the testing and certification of respiratory protection equipment. 2 the niosh tests filters for the effects of loading (particle burden), temperature, and relative humidity and requires a minimum filtration efficiency of 95%, 99% or 99ae97% using neutralized 0ae075-mm count median diameter solid aerosols at 85 l ⁄ min. filters can be certified for a range of efficiency classes (e.g. 95%, 99% or 100%) as well as for their ability to withstand degradation as a result of loading or oil mist exposures. n95 filters are not permitted to have more than 5% of the challenge aerosol concentration penetrate the filter, and would be expected to have less aerosol penetration with either larger or smaller particles than the size used in certification testing. in 1973, a letter to the editor of the new england journal of medicine from jack resnick, md, 3 suggested '…perhaps the ancient oriental custom of wearing gauze or cloth, surgical-type masks during a cold has some merit? perhaps western society has another lesson to learn by observing the oriental customs besides acupuncture.' he proposed that this matter be studied in a rigorous manner. since then, there have been many studies on the filtration efficiency under controlled laboratory settings, but until recently there has been limited study as to whether masks or respirators will provide clinically relevant protection in healthcare settings. most data have been derived from at best observational settings and frequently has been based on anecdotal rather than controlled trials evidence. 4 focused specifically on n95 masks. 8, 9 although the authors concluded from the pooled estimate of effect that the intervention effectiveness was 91%, this evidence was thin as the studies included showed inconsistencies and failed to adequately describe the use of controls. jefferson and colleagues concluded that more experimental studies were needed to identify the effectiveness of wearing face masks or respirators in reducing exhaled infectious viral particles. 7 in 2009, we reported the first prospective cluster-randomized trial comparing surgical masks, non-fit-tested p2 masks (n95 equivalent) and no masks in prevention of influenza-like illness (ili) in households. 10 intention to treat analysis showed no significant difference in the relative risk of ili in the mask groups compared with the control group. however, less than half of the subjects wore masks 'most of the time'. adherence to mask use significantly reduced the risk of ili-associated infection, with a hazard ratio of 0ae26 (95% ci 0ae09-0ae77; p = 0ae015). a recently reported randomized trial showed a significant benefit of both hand hygiene and face masks (worn by the index case and contacts) in preventing influenza transmission in households, although adherence to the face mask intervention was low among household contacts. 11 surgical masks and n95 respirators have been recognized as an important non-invasive technology to use during this new pandemic period. however, there are many factors which may compromise the overall effectiveness of these measures. poor training, lack of guidance and consistency in the use of masks, improper use and for n95 respirators, the need for fit-testing, may limit their usefulness. data from the sars experience in toronto illustrated the need for training and monitoring; loeb and colleagues (2004) found that nine of 32 (28%) nurses entering a sars patient's room did not consistently wear appropriate respiratory protection. 12 there is also the problem of workplace acceptance. in a logistics exercise undertaken during the peak of seasonal influenza activity in 2007 in australia, compliance by emergency department staff, with n95 mask wearing was found to be low, with only 36ae1% of participants wearing the mask 'occasionally' in week one and only 18ae8% by week four. many staff reported that they found the mask hot and hard to breathe through, and others reported that they had problems both communicating with patients and storing the mask between uses. 13 much time and effort has been devoted to developing an optimal strategy for the use of pandemic vaccines and antivirals, in addition to non-pharmaceutical measures. however, comprehensive assessments of the literature to date recognize the generally poor quality of evidence on which to base non-pharmaceutical pandemic planning decisions. despite the lack of high level evidence, recommendations on the use of face masks and respirators for hcws are made by many health authorities. to ensure that hcws wear face masks to protect themselves during this time, cultural attitudes and the physical discomfort and mechanical issues associated with long-term respirator use must be addressed. other factors that affect the use of personal protective equipment, such as staff and management attitudes about the value of respirator use, fatigue and the availability of replacement masks, also need to be considered. director-general of the world health organization, editors national institute for occupational safety and health. respiratory protective devices; final rules and notice, 42 cfr part 84 rationale for chinese gauze masks? effect of hand hygiene on infectious disease risk in the community setting: a meta-analysis non-pharmaceutical public health interventions for pandemic influenza: an evaluation of the evidence base interventions for the interruption or reduction of the spread of respiratory viruses physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review sars transmission among hospital workers in hong kong effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (sars) face mask use and control of respiratory virus transmission in households facemasks and hand hygiene to prevent influenza transmission in households: a randomized trial sars among critical care nurses feasibility exercise to evaluate the use of particulate respirators by emergency department staff during the 2007 influenza season all authors contributed to the writing and revising of the text. there are no conflicts of interest. key: cord-305066-g042y51w authors: abd-elsayed, alaa; karri, jay title: utility of substandard face mask options for health care workers during the covid-19 pandemic date: 2020-04-20 journal: anesth analg doi: 10.1213/ane.0000000000004841 sha: doc_id: 305066 cord_uid: g042y51w nan w ith the emergence and exponential spread of coronavirus disease 2019 (covid-19), the utility and recommendations of face masks and respirators (ie, n95 masks) for various populations have come into question. [1] [2] [3] despite the world health organization (who) recommendation that the use of face masks is only for those caring for individuals with suspected covid-19, or for those with active coughing or sneezing, inappropriate purchasing and use by the general public have led to a critically diminishing supply of face masks and respirators. 3, 4 this limitation in supply is especially concerning, given the exponential increase in cases of disease from severe acute respiratory syndrome coronavirus 2 (sars-cov-2) worldwide. health care workers (hcws), notably those in more impoverished countries, continue to be at particular risk and are faced with using substandard options. [4] [5] [6] the us centers for disease control and prevention (cdc) has suggested that the use of substandard optionsincluding surgical masks, cloth masks, and extended use or reuse of respirators-can be considered, with exercised caution. in this commentary, we attempt to characterize the utility of and provide considerations for the use of these substandard face mask options by hcws during the covid-19 pandemic. the sars-cov-2 is a respiratory virus largely spread via droplet and possibly also airborne contact. 1-6 viral spread largely occurs via exposure of the nasopharyngeal or oropharyngeal mucosa to microdroplets expelled from coughing and/or sneezing by infected individuals. thus, those persons wearing standard surgical face masks are still at risk for droplet exposure via the lateral, unsealed portions of the face mask. 4-6 on the contrary, standard respirators approved by the national institute of occupational safety and health (niosh), namely n95 masks, are fit and seal tested to ensure filtration of at least 95% of airborne droplets. few studies characterizing efficacy of cloth masks exist. to a lesser extent, viral transmission occurs by spread of microdroplets from contaminated surfaces onto the face, nasopharyngeal, and oropharyngeal mucosa. therefore, most mask options are intended for single use only, and must be carefully doffed and disposed. in the setting of a pandemic, the reuse of respirators is also being entertained and warrants careful consideration. fit-and seal-tested respirators are considered the gold standard for personal protective equipment against droplet-transmitted infections. 5, 6 the filtration efficacy of these respirators varies by manufacturer, but is also largely dependent on the size of the penetrating particles. for context, the sars-cov-2 virion spherical diameter is reported to be approximately 125 nm, as estimated by cryo-electron tomography and cryo-electron microscopy. 7,8 qian et al 9 report an approximate 99.5% filtration efficacy of n95 respirators for particles 750 nm in size. this filtration efficacy decreases to 95% for particles 100-300 nm in size. n95 respirators are sold by manufacturers only when a 95% filtration efficacy standard per niosh requirement is met. similarly, n99 and n100 respirators correspond to 99% and 99.7% filtration efficacies for particles 100-300 nm in size, respectively. 10, 11 on the contrary, surgical face masks are not required to meet similar filtration efficacy standards to be sold. depending on manufacturers and the use of niosh filtration standards, surgical face masks have widely reported filtration efficacies ranging from <10% to ≤90%. aside from filtration efficacy, risk reduction associated with surgical masks is heavily reliant on good fit and facial seal. macintyre et al 12 previously reported that the adherent use of surgical face masks or respirators was superior to not using either form of protection in preventing adults from contracting influenza in affected households. there was no appreciable difference in risk reduction between surgical face masks and respirators (n95 face masks). interestingly, the benefit of either mask was significantly dependent on adherence of face mask use. moreover, aiello et al 13 observed that the risk reduction of viral contraction with surgical face mask use was significant with concomitant hand washing practices. such findings collectively suggest that the adherent use of even suboptimal face masks, along with recommended hand washing practices, may provide meaningful decrement in the risk of contracting respiratory viral illnesses. many resource-depleted settings are considering the utility of cloth masks, which are often reusable with washing. cloth masks have been used historically, with variable reports of benefit. 14, 15 the best evidence exploring cloth masks comes from a randomized trial in vietnam that compared the risk of hcws contracting respiratory viral illnesses using "medical face masks" (presumably equivalent to standard surgical masks) with cloth masks, which were described as 2-layer cotton masks. 14 briefly, they found that hcws in the cloth mask intervention arm had a relative risk of 13.0, in reference to those persons in the medical face mask group, for contracting influenza-like illnesses. the authors conclude that cloth masks should not be used when medical face masks are an option. it should be noted that cloth masks are widely varied and provide varying potential benefit dependent on fabric type, construction, number of layers, and reuse, and cleaning practices. 16 while cloth masks are often manufactured and used in asian countries, the utility of these cloth masks is also being considered for use in other resource-depleted settings. prototypes and benefit of cloth masks have been previously published. 1416 rengasamy et al 16 reported that pure cotton, pure polyester, and cotton/polyester blend cloth masks were all significantly inferior to respirators in filtering out aerosol particles in the 100-to 300-nm range. they were unable to report superiority of any given fabric, but suggested that cloth masks may be comparable to some standard surgical masks, and the efficacy of cloth masks can be improved with appropriate face seal and fit. in the covid-19 pandemic, the chinese state council reports that masks are not necessary for persons at very low risk of infection, but that nonmedical masks, such as cloth masks, may be used. 3 cdc reports that cloth masks may be a necessary last-resort option only when respirators and surgical masks are unavailable. 4 the us cdc defines extended use as the use of a single respirator across multiple, close-contact patient encounters without doffing and replacing in between patients. 5 it defines reuse as the repeat donning and doffing of the same respirator across multiple, closecontact patient encounters. both options are inherently substandard to the single-use indications for conventional respirators. 4, 5 the risks associated with these options are that of viral transmission via self-inoculation and direct contact after touching a contaminated respirator. infectious spread with repeat respirator use is not limited to respirator reuse, but also to extended use. one study found that nurses touched their respirators an average of 25 times during a shift. 17 . cdc suggests that while extended-use practices may not decrease respiratory protection, disposal of used respirators should be considered if they are structurally compromised, directly exposed to bodily fluids, in close contact with infected patients, or after scenarios of significant aerosol production (ie, intubations). 5 the use of face shields is recommended to reduce surface contamination of the respirator. in addition, cdc recommends proper doffing and donning protocol, including the use of clean gloves to ensure proper seal and fit after donning to ensure respirator integrity and respiratory prevention with reuse. with the exponential spread of covid-19, hcws are faced with a diminishing supply of respirators (n95 masks). hcws, especially those in more impoverished areas of the world, are faced with using substandard options such as surgical face masks, cloth masks, and even extended use or reuse of respirators. surgical masks afford varying degrees of respiratory protection, which can be optimized with proper face seal and fit and with proper handwashing techniques. cloth masks carry unclear and variable benefit, and may be a last-resort option only when respirators and surgical masks are unavailable. defining the epidemiology of covid-19-studies needed supporting the health care workforce during the covid-19 global epidemic rational use of face masks in the covid-19 pandemic coronavirus disease (covid-19) advice for the public: when and how to use masks strategies for optimizing the supply of n95 respirators: crisis/alternate strategies recommended guidance for extended use and limited reuse of n95 filtering facepiece respirators in healthcare settings cryo-electron tomography of mouse hepatitis virus: insights into the structure of the coronavirion supramolecular architecture of severe acute respiratory syndrome coronavirus revealed by electron cryomicroscopy performance of n95 respirators: filtration efficiency for airborne microbial and inert particles respiratory performance offered by n95 respirators and surgical masks: human subject evaluation with nacl aerosol representing bacterial and viral particle size range do n95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks? face mask use and control of respiratory virus transmission in households facemasks, hand hygiene, and influenza among young adults: a randomized intervention trial a cluster randomised trial of cloth masks compared with medical masks in healthcare workers use of cloth masks in the practice of infection control-evidence and policy gaps simple respiratory protection-evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles physiologic and other effects and compliance with long-term respirator use among medical intensive care unit nurses key: cord-318835-sd9hbocg authors: felfeli, tina; batawi, hatim; aldrees, sultan; hatch, wendy; mandelcorn, efrem d. title: utility of patient face masks to limit droplet spread from simulated coughs at the slit lamp date: 2020-07-27 journal: can j ophthalmol doi: 10.1016/j.jcjo.2020.06.010 sha: doc_id: 318835 cord_uid: sd9hbocg nan with the accelerated spread of the severe acute respiratory syndrome coronavirus 2 leading to coronavirus disease 2019 pandemic, there are unprecedented challenges on the medical community. of major concern are the high titres of virus in the oropharynx early in the disease course, and long incubation period (5à7 days) of asymptomatic shedding of severe acute respiratory syndrome coronavirus 2. 1 effective use of personal protective equipment (ppe) such as gloves, face masks, goggles, face shields, and gowns is critical to prevent the spread of infection to and from health care workers and patients. this is particularly important to clinicians who work in close proximity with the patient's face such as when performing slit-lamp examinations. accordingly, the american academy of ophthalmology has recommended that patients not speak during slit-lamp examinations as well as the use of commercially available slit-lamp barriers or breath shields as an added measure of protection. however, breath shields may not fully eliminate the spread of droplets. 2 the use of masks by patients has been shown to mitigate the emission of various viruses into the environment and is recommended by the centers for disease control and prevention. 3 herein, we aimed to investigate how various scenarios of masks worn by patients can reduce the spread of respiratory droplets onto the examiner during a slit-lamp examination using a simulated patient cough. in a simulation, an ophthalmologist donned in standard ppe including a face mask and eye protection was positioned looking through the oculars of the slit lamp (bm 900 haag-streit). the slit lamp had a commercially available breath shield hung on oculars measuring at 9.75 inches in width and 10.5 inches in height (carl zeiss meditec ag). a manikin (vera cardiopulmonary resuscitation model, canadian red cross) was placed at the chin rest of the slit lamp to simulate a patient under examination. to standardize the target distance, the slit lamp was focused on the manikin's right eye. a patient cough was simulated using a small latex balloon that was compressed with oxygen and 1.25 ml of washable fluorescent dye that was run through tubing inside the manikin and placed inside the oral cavity. the balloon was inflated until it burst at 5 pound-force per square inch, which has been previously reported as the force for a voluntary cough and laryngeal cough reflex. 4 the simulation was performed under ultraviolet light conditions (light-emitting diode 395nm ultraviolet flashlight, wjzxtek) in order to visualize emission of fluorescent small particles, which included a mixture of dry and wet particles measuring at 30à100 mm for varied particle-size distribution (uv neon fluorescent blacklight paint kit, paint glow). 5 a video of the simulation that is slowed down by a factor of 8 at 240 frames per second is available online (video 1, available online). these methods have been previously validated for visualization of cough droplets. 6, 7 the initial simulation was repeated for 10 rounds, and subsequent series of simulations were repeated twice each to confirm consistency of observed findings. a multistep process including use of different colour dyes, thorough cleaning of equipment and manikin, as well as switching the examiner's ppe was done to ensure that no cross-contamination between each simulation interfered with the findings. in the next stage of this initiative, we aimed to identify means of further reducing the droplet spread by focusing on the use of masks for the patient under examination. repeat simulations were conducted with (i) one of the most readily available cloth masks (black cotton face mouth mask); (ii) an ear loop surgical mask (american society for testing materials level 2, 3m) positioned incorrectly (loose and covering the mouth only to mimic a commonly encountered circumstance); (iii) an ear loop surgical mask with proper positioning (american society for testing materials level 2, 3m); and (iv) an n95 mask (model 8210, 3m, not fitted to the manikin). the spread of droplets onto the field of the examiner and the slit lamp was identified under ultraviolet light conditions in each simulation as described above. this simulation demonstrates that the use of slit-lamp breath shields and standard ppe for the examiner may reduce but does not eliminate the projection of droplets onto the examiner's field, chest, shoulders, and arms (fig. 1) . the spread of smaller droplets was also identified on the bouffant cap, gloves, and shoes of the examiner. further contamination of the floor, walls, and window covers were identified within the room. in the simulation with a cloth mask, droplets were identified on gloves of the examiner, and on the slit lamp. an inspection of the inside of the mask demonstrated the spread of droplets beyond the outer borders of the mask on the superior, inferior, and lateral edges (fig. 2) . in the simulation involving the improperly positioned surgical mask, droplets were identified on the shoulders, arms, and gloves of the examiner as well as the slit lamp, floor, and walls. with the surgical mask properly positioned, the examiner was clear of droplets; however, some droplets were noted on the side bars close to the chin rest of the slit lamp. no droplets were identified on the examiner or the slit lamp in the repeat simulation with the use of the n95 mask. a view of the inside of the mask also revealed that droplets were contained within the mask. this simulation aimed to visualize the spread of respiratory droplets onto the examiner at the slit lamp. our findings suggest that the use of a properly fitted mask on the patient as an adjunct to the current standard ppe used by the examiner, and the breath shield is essential for limiting droplet dissemination during slit-lamp examinations. cloth masks decrease the spread of respiratory droplets onto the examiner and can be even more effective than a surgical mask that is worn incorrectly. however, spread of some droplets was noted on the hands of the examiner during the slit-lamp examination with cloth masks. this may be owing to the poor design and poor flexibility of the material used to make cloth masks, which can lead to gaps through which respiratory droplets can disseminate easily. if worn correctly, surgical masks greatly reduce the spread of droplets onto the examiner. although shown to be effective in this simulation, the current limited resources q1 x x of n95 masks that have not been professionally fitted, for routine clinical encounters is not supported. these findings are consistent with other studies that have demonstrated reduced droplet transmission when wearing a face mask. 8 in addition to decreasing the spread of droplets, surgical masks worn by patients have been found to decrease the emission of different viruses into the environment, including influenza virus and coronavirus. 3 it is important to note that this simulation does not identify the spread of very small particles and droplets. although the bursting pressure for the balloon was adjusted to simulate a voluntary cough, the volume of the cough was overproduced beyond what would be expected in a natural cough in order to account for the potential extent and multidirectional spread of a true cough in various scenarios under one simulated setting. no means of accounting for turbulence of mucosalivary filaments in a simulated cough have been previously reported and thus were not accounted for in this simulation. given that the goal of this simulation was to provide effective means of protecting the examiner, we did not assess the spread of droplets beyond the slit lamp and the examiner with the use of various masks. furthermore, some variations may be noted in repeat simulations. lastly, appropriate ppe for the examiner should be selected on a case-by-case basis for patients who are low risk, suspect, or confirmed positive for coronavirus disease 2019 and based on the recommendation of the local health authority. overall, this simulation demonstrates the potential spread of droplets during a slit-lamp examination from a patient cough onto the examiner, equipment, and room. based on this, our recommendations for the use of masks for patients include the following: (i) patients should wear a mask during slit-lamp examinations (including a well-fitted cloth mask if it is the only available option); (ii) correct positioning of the mask is critical, and an improperly fitted mask may provide a false reassurance of protection; (iii) slit lamps should be disinfected between patients to prevent cross-contamination. conflict of interest: no conflicting relationship exists for any author. supplementary material associated with this article can be found in the online version at doi:10.1016/j. jcjo.2020.06.010. x x each of the masks used in repeat simulations, spread of droplets, and droplets within the inside of the masks visualized with ultraviolet light. with the properly positioned cloth mask (a1), the examiner had spread of droplets onto gloves (a2). droplets spread beyond the outer borders of the mask (a3). with the improperly positioned surgical mask (b1), the examiner had droplets on the gloves, arm, chest, and shoulders (b2). droplets spread beyond the outer borders of the mask (b3). with a properly positioned surgical mask (c1), the examiner was clear of droplets, but droplets were detected on the side bar of the slit lamp (c2). no droplets spread beyond the outer borders of the mask (c3). with a properly positioned n95 mask (d1), no droplets were detected on examiner or the slit lamp (d2). no droplets spread beyond the outer borders of the mask (d3). early transmission dynamics in wuhan, china, of novel coronavirusàinfected pneumonia efficacy of slit lamp breath shields respiratory virus shedding in exhaled breath and efficacy of face masks intra-abdominal pressures during voluntary and reflex cough cough aerosol in healthy participants: fundamental knowledge to optimize droplet-spread infectious respiratory disease management coughing and aerosols barrier enclosure during endotracheal intubation visualizing speech-generated oral fluid droplets with laser light scattering footnotes and disclosure quality improvement grant, department of ophthalmology and vision sciences key: cord-305867-i7wdwjph authors: macintyre, c raina; chughtai, abrar a. title: masks in the community are an effective strategy: author's response to haslam et al (2020) date: 2020-09-09 journal: int j nurs stud doi: 10.1016/j.ijnurstu.2020.103751 sha: doc_id: 305867 cord_uid: i7wdwjph nan we write in response to the letter from a haslam (haslam, 2020) about our paper (macintyre, chughtai 2020). haslam presents a range of arguments as to why community mask use is ineffective. we note that in doing so, haslam gives more weight to sub-analysis data on unvalidated clinical case definitions than data on laboratory confirmed infections to support her statements. the sum of the evidence cited in our review shows that face masks are protective in the community and consistent with the findings of the individual studies. most of the studies only examined influenza or clinical case definitions of influenza as outcomes. influenza is a seasonal disease, and varies from year to year, with high incidence in some years and extremely low incidence in others (lipsitch and viboud 2009) . further, the short incubation period of influenza and the possibility of pre-symptomatic transmission make it complex to study. this makes it important to consider the findings of the rcts in the sub-analyses such as by timing (36 hours) and compliance. haslam suggests we have misinterpreted the data. the macintyre 2009 rct (macintyre, cauchemez et al. 2009 ) showed that adherence to mask use was associated with a significantly reduced risk of ili-associated infection (macintyre, cauchemez et al. 2009 ). most community mask trials demonstrated low adherence, including this one (25-30% by day 5) (macintyre, cauchemez et al. 2009 ) which likely explains the non-significant results in the intention-to-treat analysis. adherence has been shown to be related to risk-perception, and would likely increase during the covid-19 pandemic compared to seasonal influenza. as such analysis of adherent participants is justified and valid evidence. cowling et al conclude that "hand hygiene and facemasks seemed to prevent household transmission of influenza virus when implemented within 36 hours of index patient symptom onset." this is consistent with our interpretation. we agree that the intention-to-treat analysis were not significantly different between the two intervention arms. however, haslam is incorrect in concluding that ili was higher (and she extrapolates form this that influenza transmission is higher) in the mask group based on single digit outcomesthese are not statistically significant differences. the statistically significant findings were on early use of interventions (within 36 hours) (cowling, chan et al. 2009 ). the authors show that for rt-pcr confirmed influenza, which is the most important and validated outcome, there were "fewer infections among participants using facemasks plus hand hygiene (adjusted odds ratio, 0.33 [95% ci, 0.13 to 0.87])". this is shown in table 5 , and the only significant outcome. hand hygiene alone is not significant in protecting against this validated outcome. the authors final conclusion is consistent with ours -that "our results suggest that hand hygiene and facemasks can reduce influenza virus transmission if implemented early after symptom onset in an index patient." this probably relates to the relatively short latent period and incubation period of influenza (cowling, chan et al. 2009 ). aeillo 2010 and 2012: the aiello 2010 trial compared masks, masks + hand hygiene and control. the 2010 trial found that the mask only arm and the mask plus hand hygiene arm had significant protection during the later weeks of the trial (table 4) , (aiello, murray et al. 2010) probably reflecting a larger sample size, as recruitment continued and a there was a late influenza season that year (see discussion of the 2010 paper) (aiello, murray et al. 2010 ). the results state, "after the participant enrolment ended (ie, week 3 onward), significant reductions in ili incidence were observed in the mask and hand hygiene group (weeks 4-6) and in the face mask-only group (weeks 3-5) compared with the control group. after covariate adjustment, ili incidence was significantly lower among the mask and hand hygiene group compared with the control group from week 4 onward" (aiello, murray et al. 2010) . the authors further state that the study year was a mild influenza season, which would reduce statistical power. the final conclusion of the authors is consistent with ours -that masks and handwashing were protective. they also state: "it is important to note that handwashing habits were the same in both the face mask-only and control groups at baseline and over the study period, which suggests that mask use alone may provide a reduction in respiratory illnesses regardless of handwashing practices" (aiello, murray et al. 2010 ). regarding aiello et al., 2012 , the authors conclude:"face masks and hand hygiene combined may reduce the rate of ili and confirmed influenza in community settings. these non-pharmaceutical measures should be recommended in crowded settings at the start of an influenza pandemic." table 3 shows significant reduction of ili from weeks 3-5 of the study. the results states, "at week 3 and onward, significantly reduced ili rates were observed in the face mask and hand hygiene group compared to the control in adjusted models (see table 3 ) (aiello, perez et al. 2012) . larson et al., 2010: while the rates of uri were not significantly different between groups, the larson trial showed lower rates of more specific outcomes, confirmed influenza and ili in the masks + hand hygiene group (larson, ferng et al. 2010) . regarding hand hygiene, table 4 of the 2010 paper shows the secondary attack rate was lowest for masks + hand hygiene. for confirmed influenza, the mask + hand hygiene group had the lowest number of confirmed influenza cases and the lowest secondary attack rate (table 4) (larson, ferng et al. 2010 ). there is no statistical significance of the hand hygiene finding, and the authors conclude: "consistent with our findings, cowling et al. found a modest but nonsignificant impact of hand hygiene on viral respiratory transmission" (larson, ferng et al. 2010) . table 5 in larson et al shows that the only statistically significant protection was the hand sanitizer and face mask group (or 0.82, 95% confidence intervals 0.70, 0.97). hand hygiene alone was not significant -or 1.01 95% confidence intervals 0.85 -1.2 (larson, ferng et al. 2010 ). suess et al., 2012 . the conclusions of suess et al (abstract) are: "when analysing only households where intervention was implemented within 36 h after symptom onset of the index case, secondary infection in the pooled m and mh groups was significantly lower compared to the control group (adjusted odds ratio 0.16, 95% ci, 0.03-0.92)" (suess, remschmidt et al. 2012) . this is what is reflected in our table 1 and is in agreement with the author"s conclusions. please see table 4 of the suess paper as well (suess, remschmidt et al. 2012) . in summary, it remains true as stated in our review (macintyre, chughtai 2020) that there are more, and larger, rcts of mask use in the community for well people than there are for use by sick people. the conclusion of our review (that there is evidence that masks protect well people in the community) does not differ from the authors of the included papers, as shown by direct quotes from the relevant papers, above. whilst intention-to-treat analysis did not show significance in many of these trials, the sum of the evidence shows effectiveness of mask use in community settings when accounting for early use (reflecting the short incubation period and latent period of influenza, which is the outcome of interest in most studies) and adherence (which was low in many studies). it is important to note that the available rct evidence on community mask use has been interpreted very inconsistently by different expert groups, with the us recommending universal face mask use in the community, and the who, uk and others, not recommending it (greenhalgh, schmid et al. 2020) . during the covid-19 pandemic, the general community are often left to fend for themselves, especially in cities or countries where the incidence is high. the use of cheap devices like masks has very low risk and possible public health benefits in slowing transmission (greenhalgh, schmid et al.) . it is therefore important to evaluate the available evidence, allowing for factors such as adherence and timing, to inform potential use of masks in the community. finally, a who-commissioned study has shown that masks reduce the risk of infection with beta-coronaviruses by 85%, and are equally protective in community and healthcare settings (chu, akl, et al 2020) . on this basis, the who changed its position in june 2020 to also recommend face masks in the community. mask use, hand hygiene, and seasonal influenza-like illness among young adults: a randomized intervention trial facemasks, hand hygiene, and influenza among young adults: a randomized intervention trial physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis. the lancet facemasks and hand hygiene to prevent influenza transmission in households: a cluster randomized trial preliminary findings of a randomized trial of non-pharmaceutical interventions to prevent influenza transmission in households -face masks for the public during the covid-19 crisis 2020: a rapid systematic review of the efficacy of face masks and respirators against coronaviruses and other respiratory transmissible viruses for the community, healthcare workers and sick patient impact of non-pharmaceutical interventions on uris and influenza in crowded, urban households influenza seasonality: lifting the fog a rapid systematic review of the efficacy of face masks and respirators against coronaviruses and other respiratory transmissible viruses for the community, healthcare workers and sick patients face mask use and control of respiratory virus transmission in households a rapid systematic review of the efficacy of face masks and respirators against coronaviruses and other respiratory transmissible viruses for the community, healthcare workers and sick patients the role of facemasks and hand hygiene in the prevention of influenza key: cord-333379-wtdhdcjz authors: rajagopaian, sanjay; huang, sui; brook, robert d title: flattening the curve in covid-19 using personalised protective equipment: lessons from air pollution date: 2020-05-11 journal: heart doi: 10.1136/heartjnl-2020-317104 sha: doc_id: 333379 cord_uid: wtdhdcjz nan flattening the curve in covid-19 using personalised protective equipment: lessons from air pollution sanjay rajagopaian , 1 sui huang, 2 introduction covid-19 is a massive global economic and health calamity causing social and economic disruption at an unprecedented scale. ironically, this large-scale disruption in anthropogenic activity has also fueled a massive downturn in consumption of fossil fuels and global reduction in air pollution. indeed, it is widely speculated that current reductions in acute coronary syndrome admissions noted globally may relate to reduction in air pollution level, given the well-known relationship between reductions in air pollution levels and cardiovascular events. the ominously opposing trajectories, decrease in air pollutionrelated mortality and surge in covid-19 deaths also reveal the eerie similarities in the flurry of public discourse regarding the utility of personalised protective equipment (ppe) to prevent exposure among the public. prior to the covid-19 epidemic, there has been a vigorous debate about the efficacy of ppes, including n95 respirators and masks, in protecting the public against air pollution risk (which is for the most part cardiovascular) and 'flattening' the shape of the air pollution exposure response curve. 1 unfortunately for air pollution, there has been limited guidance for the public in terms of efficacious personal interventions. given the large burden of disease attributable to both air pollution and now covid-19, the public deserves rapid dissemination and adoption of personal-level strategies to prevent untoward health outcomes. central to a public health approach in minimising spread among the general public is to mitigate risk of exposures, not only to covid-19 cases but also to asymptomatic carriers who may harbour the virus and thus pose a significant health risk to others. this at the moment seems to be a larger problem, given the fact that widespread testing is unavailable. while the efficacy of governmental lockdowns to minimise widespread dissemination of the virus to protect the public is highly effective in preventing spread at least in the short term, emerging data from countries such as china, japan and south korea suggest that other measures could also have contributed in reducing the spread. for instance, in many of these countries, the use of masks of all types was widespread prior to severe acute respiratory syndrome (sars)-cov2, and it is culturally and socially acceptable for the public to wear masks. citing lack of evidence, the centers for disease control and prevention (cdc) initially did not recommend the use of any face mask in any out of workplace setting. on 3 april 2020, citing 'new evidence', the cdc recommended wearing cloth face coverings in public settings. this is ironic because many cdc-recommended activities such as social distancing and handwashing also completely lack high levels of evidence to prevent pandemics. they were promoted because they are logical and are low/no-cost measures. while wearing a mask may not necessarily eliminate healthy people on the street from getting sick and does not replace important measures such as handwashing or social distancing, it may be considerably better than doing nothing. while studies reveal the challenge of establishing a clear benefit for handwashing, surface desensitisation, social distancing or of wearing masks, the absence of evidence is indeed not equivalent to evidence of absence. human corona viruses are typically about 125 nm but are often expelled as part of droplets that range from hundreds of microns down to about 10 microns. the critical size of the so-called large 'droplets' is a function of many physical parameters, such as relative humidity, the ambient air velocity and air temperature, while the trajectory and deposition of these droplets depend on the size and velocity of these particles when discharged from a patient or carrier. previous modelling studies have suggested that large particles of >100 micron can reach distances as far as 6 ft (the recommended gap for social distancing), when ejected via coughing or sneezing, but simple face masks could be effective with these larger particles (figure 1). in contrast, smaller particles of <10 micron can be carried for longer distances. the droplets of a typical cough expulsion have a wide size distribution, but recent studies using laser particle size analysers seem to suggest that the majority of particles are actually substantially larger than 50 microns with evidence of both unimodal and bimodal distribution of particles. 2 3 however, many studies have shown that there are substantial numbers of particles less than 2.5 micron (pm 2.5 ) which contribute very little to the overall mass but could potentially contribute to viral dissemination. this situation is analogous to air pollution where the pm 2.5 and ultrafine particles contribute significantly to particle number but only to a small fraction of the overall mass, but, owing to their deposition into the distal airway/alveoli, may exert systemic effects, including on the cardiovascular system. 1 in the case of sars-cov2, although a number of aspects of biology are unknown, a closer examination of several issues may convince most that it may be targetable using a simple mask intervention. n95 respirators, widely touted as likely highly effective in reducing exposure to sars-cov2, have only been validated for usage during occupational settings, with very few specifically validated to provide protection even against ambient pm 2.5 , let alone infectious agents like sars-cov2. moreover, it is widely recognised that n95 respirators made by different manufacturers have different performance efficiencies below the 0.3 micron range that are dependent on user fit and other ambient conditions. n95 respirators are uncomfortable and cannot be worn for more than a few hours at a time and are not going to be available for use by the lay public, given current supply chain issues and cost. in contrast, inexpensive face masks, such as procedural (surgical masks) or others made from cloth, cotton or gauze, are widely available, can be worn for long periods successfully, and have been historically dismissed both for protection against pm 2.5 and viral infections as they are presumed to be ineffective in reducing exposure to particles of 2.5 micron. while it is true that the number of studies that have compared n95 masks with surgical or cloth masks in the context of air pollution and viral infections is limited, it is untrue that there is no evidence. 4 5 in a study in mannequins, disposable surgical masks were 2 rajagopaian s, et al. heart month 2020 vol 0 no 0 editorial more effective than cloth masks, but n95 respirators were the most effective in removing air particles. cloth mask performance, although unpredictable in some cases, reduced particles by 57%. 6 in a study in indonesia, nine different masks were compared. surgical masks were the only class of mask to significantly decrease pm 2.5 , although they had a large performance range and did not improve pm 2.5 exposure in all subjects. 7 this is to be expected, as a number of factors including facial seal are important determinants of efficacy of surgical masks. in another study from europe comparing homemade cloth masks and surgical masks with n95 respirators in volunteers exposed mostly to particles in the ultrafine range (<0.1 micron), generated by lit candles, both inward protection and outward protection (protection from transmitting to the environment) were tested during both short term (few minutes) and over several hours. 5 the results confirmed the superior efficacy of n95 respirators, but what was striking was the efficacy of surgical masks and homemade masks in reducing particle concentrations by 4-fold and 3-fold, respectively (compared with 100-fold by the n95 mask). 5 it is well known that the efficacy of masks for larger particles, particularly in the droplet range, likely the most important societal transmission mode of covid, is substantially higher. thus, the evidence supports the efficacy for a simple mask type intervention that may be particularly apt for the protection of caregivers not involved with direct patient care and also for the public at large, particularly in social situations that brings them in close proximity to others such as in grocery stores and restaurants. technically, one could quantify by how much the threefold to fourfold reduction of droplets achieved by masks may contribute to a reduction in sars-cov2 payload and reproduction rates, but unfortunately, this type of mathematical exercise would require a priori knowledge of a number of factors starting with the infectious load and the distribution of viral particles in large versus smaller particles, which are currently unavailable. however, a number of aspects relevant to sars-cov2 biology could be helpful in circumventing these limitations in understanding. current testing for sars-cov2 suggests that the virus is present in large numbers in the upper respiratory tract. the receptor for sars-cov2 (ace-2) is also highly expressed in the nasal epithelium and upper respiratory tract (figure 1). 8 given that the upper respiratory tract is the major site for sars-cov-2 replication and likely entry, wearing simple face masks which exert a barrier function in blocking not only large projectile droplets but also, to a lesser extent, smaller aerosols of <10 micron, may substantially reduce the replication rate. thus, used in combination with other measures, a simple face mask intervention may result in further flattening of the 'curve'. the lessons learnt from covid-19 could be leveraged to reduce air pollution-related cardiovascular mortality and morbidity once this current impasse from the virus lifts, the inevitable resumption of anthropogenic activity and related fossil fuel consumption at least in the short term. no commercial re-use. see rights and permissions orcid id air pollution and cardiovascular disease: jacc state-of-the-art review toward understanding the risk of secondary airborne infection: emission of respirable pathogens cough aerosol in healthy participants: fundamental knowledge to optimize droplet-spread infectious respiratory disease management the use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence professional and home-made face masks reduce exposure to respiratory infections among the general population evaluating the efficacy of cloth facemasks in reducing particulate matter exposure challenges in evaluating pm concentration levels, commuting exposure, and mask efficacy in reducing pm exposure in growing, urban communities in a developing country sars-cov-2 entry genes are most highly expressed in nasal goblet and iliated cells within human airways contributors sr drafted the manuscript. sh and rdb provided critical revisions.funding the authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.competing interests none declared. patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research. provenance and peer review not commissioned; externally peer reviewed. attribution non commercial (cc by-nc 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. see: http:// creativecommons. org/ licenses/ by-nc/ 4. 0/. key: cord-317047-86rb6hov authors: ippolito, mariachiara; vitale, filippo; accurso, giuseppe; iozzo, pasquale; gregoretti, cesare; giarratano, antonino; cortegiani, andrea title: medical masks and respirators for the protection of healthcare workers from sars-cov-2 and other viruses date: 2020-04-27 journal: pulmonology doi: 10.1016/j.pulmoe.2020.04.009 sha: doc_id: 317047 cord_uid: 86rb6hov abstract the use of medical masks and respirators as personal protective equipment is pivotal to reducing the level of biological hazard to which healthcare workers are exposed during the outbreak of highly diffusible pathogens, such as the recent novel coronavirus sars-cov-2. unfortunately, during this pandemic, supplies are rapidly running out worldwide, with potential consequences for the rate of occupational infections. also, knowledge about specific characteristics of respirators is of utmost importance to select the proper type according to the clinical setting. a wide variety of literature is available on the topic, but mostly based on influenza viruses infection models. clinical evidence on the use of respirators is poor and interest in the topic has not been constant over time. a better understanding of sars-cov-2 transmission is needed, together with high-quality clinical data on the use of respirators or alternative devices. moreover, healthcare workers, regardless of their level of experience, should receive specific training. this review aims to summarize the available evidence on the use of medical masks and respirators in the context of viral infections, especially the current coronavirus disease 2019 (covid-19). the outbreak of highly diffusible pathogens, such as the recent pandemic of 81 sars-cov-2 infection, can increase the level of biological hazard to which 82 healthcare workers are exposed thus requiring the use of personal protective 83 equipment (ppe). healthcare institutions should also plan the early isolation of 84 sources and provide training program on the appropriate use of ppe. [1] ppe, 85 defined as 'equipment worn to minimize exposure to hazards that cause serious 86 workplace injuries and illnesses', includes masks and respirators. [2] the use of ppe 87 and the application of other safety measures, especially in the context of a public 88 health emergency of international concern, is regulated by international and national 89 authorities that issue indications for healthcare workers and general population, 90 according to the characteristics of transmission and the different levels of exposure to 91 risk. [3] unfortunately, in the case of a pandemic, the supply of ppe can be 92 insufficient or heterogeneously distributed around the world, due to centralized 93 production hubs, transport difficulties, lack of stockpiles, panic buying and 94 appropriate heavy use. [7] with a rising demand for incontrovertible and clear data. the term 'respirators', in the context of personal protective equipment, should 126 be intended as filtering media, usually in the form of half-face or full-face masks, 127 used as protection for healthcare workers exposed to pathogens. 128 the main performance characteristics of medical masks and respirators are 130 summarized in table 1 . 131 medical masks are loose-fitting and disposable. they are meant to reduce the 132 spread of the wearers' respiratory droplets to other people and the environment and 133 to provide a general protection of the wearer from large droplets, usually generated 134 by cough or sneezing, and body fluid splashes. type i medical masks are generally 135 used for patients with the aim of controlling the source, and type ii or type iir by 136 healthcare workers in operatory room or procedural settings. the main difference 137 among the types is according to their bacterial filtration efficiency, i.e. the efficiency 138 as a barrier to bacteria penetration. the protection from splashes is only provided by 139 and size. inhalation and exhalation seal checks will be then performed before every 160 use, to tighten the device properly and confirm that it was put on properly. filtering 161 facepiece respirators are also available in versions with an expiratory valve, which 162 make them more comfortable for long-time wearing. the valve, in fact, opens during 163 the expiratory phase of the wearer's breathing, allowing the exhaled air to flow-out. 164 the protection from body fluids and splashes is rarely guaranteed by valved ffr, 165 and has to be confirmed by the label "type iir", as for medical masks. the presence 166 of an expiratory valve also reduces goggles fogging. [10,11] the nominal protection 167 factor is an important index of a respirator performance. it is measured as the ratio 168 between external concentration of contaminant and its concentration measured on 169 the inner side of the device (cout/cin). if we assume cout to be 1, with cin = (1 -170 filtration performance), we can easily calculate the nominal protection factor. as an 171 example, a respirator with a 94% filtration performance, will have a nominal 172 protection factor of 16. in this case, the value means that the contaminant is 16 times less concentrated inside the device than in the external environment. another 174 parameter to be known is the threshold limit value, a threshold level of concentration, 175 specific for each contaminant, which must not be exceeded if the safety of the wearer 176 is to be guaranteed. the real-life protection given by a respirator, in fact, depends on 177 its assigned protection factor, an index that depends on the protection factor provided 178 by the respirator, but also by the ratio between the concentration of the contaminant 179 and its threshold limit value. [11] in the case of some biological contaminants, such 180 as the case of sars-cov-2, a threshold limit value is not known, and so the 181 an interesting pilot study has evaluated n95 respirator and medical masks in 288 the setting of home care [30] . the participants were three nurses, involved in 289 healthcare assistance at a patient 's home. the workplace protection factor was the 290 primary outcome of the study, defined as cout/cin, i.e. the ratio between the aerosol 291 concentrations inside (cin) and outside (cout) the device. the measurement of workplace protection factor was repeated twice for each participant, one with n95 293 respirator and one with medical mask. n95 respirators provided higher respiratory 294 protection in comparison to medical masks, but the protection factors varied on an 295 individual basis, also depending on the activity performed, with a greater risk in 296 specific tasks like tracheal suctioning or nebulizer treatments. [30] bench study, they found that applying a medical mask on the source could 312 significantly reduce the exposure of the receiver to a radiolabeled aerosol, providing 313 a higher protection than a n95 respirator worn by the receiver. the study was 314 conducted in a chamber designed with 6 air exchanges per hour to permit both 315 dilution and deflection of exhaled particles, and the effect was lost at 0 air exchange per hour. since the effectiveness of respirators is strongly dependent on their 317 capacity to seal to the face, a more recent bench study has used modern and more steam, and moist heat) on two models of n95 respirators, previously contaminated 354 with h5n1. [36] post decontamination viral load results decreased with all the 355 methods. filter performance was also tested, and no alterations were registered. 356 these findings were in line with data on six respirators with h1n1 contamination [37] . 357 other studies have observed physical degradation of respirator materials such as the 358 fibers composing the body material, which is probably less resistant than the filters. 359 [38] thus, the decontamination should balance the need for inactivation of the 360 specific pathogen, even from the interior layers of the respirator, and the need to 361 preserve the filtering performance, the structure of the respirator and its fitting 362 characteristics. further studies are needed to clarify the safety profiles of re-using 363 procedures of disposable ppe. meanwhile, if re-use is needed, the user should check that the decontamination tests have already been performed on the specific 365 model of ffr. 366 the use of cloth-masks in comparison with medical mask and usual 367 protection, has also been investigated by a multicentre cluster randomized trial, 368 including 1607 healthcare workers. the trialshowed a significantly higher rate of ili in 369 the cloth-mask intervention group (rr=13.00, 95% ci 1.69 to 100.07) compared with 370 the medical mask intervention group and with the entire control group, where 371 healthcare workers wore their usual protection (including n95 respirator, no mask, 372 medical mask, cloth mask or a combination of medical and cloth mask). [39] 373 although necessary, the use of ppe can also influence the performance of 375 healthcare workers, as observed in studies on cadaveric models, where a higher 376 difficulty rate and a lower success rate of tracheal intubations were registered. available; n-: tested with nacl filter loading; r-: tested with dioctylphthalate filter loading; p-: tested clinical features of patients 428 infected with 2019 novel coronavirus in wuhan, china occupational safety and health administration. personal protective equipment center for disease control and prevention. interim infection prevention and 434 control recommendations for patients with suspected or confirmed covid-19: protecting health-care workers. the lancet safe use of personal protective equipment in the 462 treatment of infectious diseases of high consequence. a tutorial for trainers in 463 healthcare settings version 2: 2 assigned protection factors for the revised respiratory protection 467 medical face masks -requirements and test 470 methods natural ventilation for infection control in health-care settings cdc-niosh. 42 cfr part 84 respiratory protective devices to papr or not to papr? can a systematic 479 review on the efficacy and safety of chloroquine for the treatment of covid-19 and now for something completely different: from 2019-ncov and 482 covid-19 to 2020-nman viral infections acquired indoors through airborne, 486 droplet or contact transmission respiratory virus shedding in exhaled 489 breath and efficacy of face masks is the coronavirus airborne? experts can't agree rational use of personal protective equipment (ppe) for coronavirus 494 disease (covid-19), interim guidance ipcppe_use-2020.2-eng.pdf?sequence=1&isallowed=y aerosol generating 498 procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review expert consensus on respiratory therapy related to new coronavirus infection in 502 severe and critical patients two respiratory protective devices used by home-attending health-care workers (a pilot study) professional and home-made face masks reduce exposure to respiratory infections among the general 534 population quantifying exposure risk: surgical masks and 537 respirators respiratory source control versus receiver 540 protection: impact of facemask fit effectiveness of surgical and cotton masks in 543 cov-2: a controlled comparison in 4 patients decontamination and reuse of filtering facepiece respirators three decontamination treatments against influenza virus applied to filtering 550 facepiece respirators a 553 pandemic influenza preparedness study: use of energetic methods to 554 decontaminate filtering facepiece respirators contaminated with h1n1 aerosols 555 and droplets effects of ultraviolet germicidal irradiation (uvgi) on n95 respirator filtration 558 performance and structural integrity a cluster randomised trial of cloth 561 masks compared with medical masks in healthcare workers comparison 564 of intubation using personal protective equipment and standard uniform in 565 simulated cadaveric models the effect of severe acute respiratory syndrome (sars) on 568 emergency airway management respirator 571 tolerance in health care workers effect of surgical masks worn concurrently over n95 filtering 574 extended service life versus increased user burden recommended guidance for extended use and limited reuse of n95 filtering facepiece respirators in healthcare settings consensus guidelines for managing the airway in patients with covid-19 self-585 contamination during doffing of personal protective equipment by healthcare 586 workers to prevent ebola transmission guidance for wearing and removing personal 589 protective equipment in healthcare settings for the care of patients with 590 suspected or confirmed covid-19 none 602 funding: this research did not receive any specific grant from funding agencies in 609 the public, commercial, or not-for-profit sectors. 610 key: cord-354111-rj6te7fz authors: stone, teresa e.; kunaviktikul, wipada; omura, mieko; petrini, marcia title: editorial: facemasks and the covid 19 pandemic: what advice should health professionals be giving the general public about the wearing of facemasks? date: 2020-04-12 journal: nurs health sci doi: 10.1111/nhs.12724 sha: doc_id: 354111 cord_uid: rj6te7fz nan and a lack of personal protective gear. hospitals resorted to pleading on social media for more protective equipment (gan, thomas, & culver, 2020) . medical staff during the height of the crisis in wuhan, had only one protective suit per day and were forced to wear diapers as they could not change their protective gear for as long as 12 hours. the numbers of health professionals falling ill have obviously led to further shortages and one wuhan doctor was quoted as saying, "just a very rough estimate, 100 nurses and doctors can look after 100 ordinary beds and 16 icu beds. if they are sick, not only do they occupy 100 beds, but the staff taking care of 100 beds are gone. that means a hospital loses the capacity of 200 beds." (ma et al., 2020) . in the light of this, china's national health commission's warning to health professionals to make "reasonable use" of protection gear warning against "excessive and disorderly use" (frias, 2020) seems unreasonably harsh. the same issues are being seen across the globe as the pandemic spreads: over 2000 italian health workers contracted the disease and there have been many deaths partly as a result of a lack of availablity of personal protective equipment (international council of nurses, 2020) . it is a similar story in spain with over 5400 health workers infected as of the end of march 2020nearly 14% of the total infections in that country (minder & peltier, 2020) . panic buying of masks has resulted in shortages across the world. over 10,000 people queued up for masks in hong kong, with one woman waiting for over 18 hours, and another reported that she had used the same mask for over five days (huang & tong, 2020) . a shipment to hong kong was deemed so valuable it had an armed escort (woodhouse, kuchler, & liu, 2020) . the world health organization's director general, dr. tedros adhanom ghebreyesus, said that, as a result of the covid-19 outbreak, demand for personal protective equipment was 100 times higher than average, and prices had risen to 20 times higher resulting in global stocks of masks and respirators being insufficient to meet supply (boseley, 2020) . he went on to say that there were delays of four to six months in supply and that the shortage was due to "widespread inappropriate use" by those who were not ill or not medical staff. one consequence is that the second-worst hit city in hubei province faces a shortfall of 24,000 of protective gear, 60,000 masks, as well as 15,000 this article is protected by copyright. all rights reserved. accepted article goggles and face shields (frias, 2020) and there are people in the streets wearing the n95 mask and other professional masks that healthcare workers need. videos have emerged from wuhan, the epicenter of covid-19, of the chinese government using drones to admonish people for not wearing masks (pietsch, 2020) and villagers have taken to the same tactics: this clip shows a woman being scolded by a man operating a drone in an inner mongolian village https://www.youtube.com/watch?v=--nn7k0rc9u. ironically the wearing of masks has hindered efforts to trace suspected carriers because the surveillance technology cannot recognize faces (chen, 2020) . despite the advice from the world health organization (who) (2020) that frequent handwashing with soap and water or use of an alcohol-based hand rub is the primary means of prevention along with respiratory hygiene, maintaining social distance and avoiding touching the eyes, nose and mouth many organizations outside of health are advising mask use. for example, across japan, hotels, transport, and retail staff wear masks and frequently, this is a company directive. for instance, all nippon airways (ana), japan airlines (jal) and japan railways (jr) have explained that staff wears masks "to provide safe services for customers," among other reasons. in some other cases the request to wear masks has come from employees, for example, the association of flight attendants-cwa, which represents flight attendants from hawaiian and more than a dozen other airlines, is asking airline to allow flight attendants to wear masks on flights to and from asia (oliver & thompson, 2020) . to date, there has been mounting anger as the airlines have refused this request citing the centers for disease control and prevention (2019) policy that that face masks should only be used by airline crew members when they "are helping sick travelers with respiratory symptoms such as coughing or sneezing." facemasks are also advised for sick travelers and those sitting near passengers with respiratory conditions. more concerningly, some health professionals and government organizations have misconceptions about mask efficacy: for example, the thai health minister is strongly this article is protected by copyright. all rights reserved. accepted article advocating the use of face masks contrary to who advice and health officials in many asian countries have required the general public to wear masks (boonbandit, 2020; tufekci, 2020) . so, is wearing a mask likely to be preventive? experts tell us that it is less useful than frequently washing hands. the world health organization's director general recently pointed out that masks were not always beneficial for the healthy general public, "masks don't necessarily protect you, but they doif you have the diseasestop you from giving it to anybody else" (boseley, 2020) . authors of a recent systematic review of ten randomized control trials found limited evidence for face mask effectiveness in preventing influenza virus transmission either when worn by the infected person to avoid transmission or when worn by uninfected people to reduce exposure (xiao et al., 2020) summing up evidence pawlowski (2020) notes that surgical masks are designed for surgeons to wear to prevent the transmission of pathogens from their nose and mouth to the surgical field; they are not intended to avoid viruses being inhaled through the mask. neither are they designed to be worn for extended periods as many of the general public do. the shortage of masks has led to a range of inappropriate and potentially dangerous ways of covering the nose and mouth. children and adults in china have used plastic bags to cover themselves and resorted to other desperate measures such as wearing plastic bottles over their heads, ski masks and even sanitary towels. more frequently seen are cloth masks or scarves used as a mask, and there is no compelling evidence to suggest that these are effective. knowledge about the sars-cov-2 virus is rapidly evolving, but it is thought that the virus is transmitted through droplets, direct contact, and by coming into contact with contaminated surfaces and it is not known to be airborne and cannot circulate through the air (united nations, 2020). the respiratory droplets may travel up to six feet from someone who is sneezing or coughing. bai (2020) cites chiu an infectious disease expert who states that "if you have an infected person in the front of the plane, for instance, and you're in the back of the plane, your risk is close to zero simply because the area of exposure is thought to be roughly six feet from the infected person." authors of a recent systematic review concluded that most viruses from the respiratory tract, such as corona, influenza, or sars can persist on surfaces for a few days and can thereby be a continuous source of transmission if no regular preventive surface disinfection is performed (kramer, schwebke, & kampf, 2006) . the sars-cov-2 virus resembles other human coronaviruses, such as those that cause sars and mers and can stay on surfacessuch as metal, glass or plastic this article is protected by copyright. all rights reserved. accepted article for as long as nine days but can be efficiently inactivated by surface disinfection procedures with 62-71% ethanol, 0.5% hydrogen peroxide or 0.1% sodium hypochlorite within 1 minute (kampf, todt, pfaender, & steinmann, 2020) . the extensive media reporting and frequent use of pictures of people wearing masks may have had a role in fueling the mask-wearing frenzy, but there have been many articles with sensible, evidence-based advice cautioning against a reliance on masks and instead washing hands frequently in soapy water, using correct etiquette when coughing and sneezing and avoiding touching the face and referencing reliable sources for the information they give (boseley, 2020; secon, 2020) . the director general of the centers for disease (cdc) control said: "i think this virus is probably with us beyond this season, beyond this year, and i think the virus eventually will find a foothold and we'll get community-based transmission and you can start to think about it like seasonal flu. the only difference is we don't understand this virus" (moreno, 2020) . we need to respond appropriately to the threat from this threat knowing that climate change, global interconnectedness, antivaccine sentiment and a myriad of other factors leave us vulnerable to global pandemics and increasing infectious disease outbreaks (global preparedness monitoring, 2019). along with unknown viruses, we also need to manage the ones we know. in the 2019-2020 season, there have been at least 15 million cases of influenza and 8,200 deaths including 54 children in the united states alone (guzman, 2020) . as health professionals, we need to be clear about what preventative measures we should take and about the advice we give the public. the primary advice for prevention is effective handwashing with soap and water for at least 20 seconds, rubbing the hands together and avoid touching the mouth, nose and eyes (world health organization, 2009). the inappropriate use of masks has become a moral issue leaving frontline health workers without the necessary protective equipment. as health professionals, we have an obligation to model appropriate health behaviors and disseminate accurate health information based on current evidence that the use of surgical facemasks by the general public is not recommended unless they are looking after a sick person in a household setting or are themselves suffering an illness. far more effective is through handwashing and maintaining a safe distance from other people. how-to-use-masks how to choose and wear a mask safely how the new coronavirus spreads and progresses -and why one test may not be enough anutin: farangs who don't wear masks 'should be kicked out who warns of global shortage of face masks and protective suits coronavirus outbreak tests china's surveillance technology thousands of chinese doctors volunteered for the frontline of the coronavirus outbreak. they are overwhelmed, under-equipped, exhausted, and even dying over 1,700 frontline medics infected with coronavirus in china a world at risk: annual report on global preparedness for health emergencies coronavirus is spreading -but the flu is a greater threat to americans coronavirus outbreak: hong kong mask shortage reveals failings of a free market high proportion of healthcare workers with covid-19 in italy is a stark warning to the world: protecting nurses and their colleagues must be the number one priority persistence of coronaviruses on inanimate surfaces and its inactivation with biocidal agents how long do nosocomial pathogens persist on inanimate surfaces? a systematic review hundreds of chinese medical staff infected with coronavirus face mask use and control of respiratory virus transmission in households virus knocks thousands of health workers out of action in europe cdc director says coronavirus could stay in us through this year and beyond flight attendants ask hawaiian airlines to permit expanded mask usage amid coronavirus concerns coronavirus outbreak leads stores to sell out of face masks china is using drones to scold people for going outside and not wearing masks amid the coronavirus outbreak people are racing to buy face masks amid the coronavirus outbreak, but they probably won't protect you from illness preventing spread of disease on commercial aircraft: guidance for cabin crew why telling people they don't need masks backfired coronavirus: un health agency moves fast to tackle 'infodemic'; guterres warns against stigmatization masks and n95 respirators clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in exploring the reasons for healthcare workers infected with novel coronavirus disease 2019 (covid-19) in china mask mania: coronavirus sparks global scramble for face covers advice on the use of masks in the community setting in influenza a (h1n1) outbreaks basic protective measures against the new coronavirus nonpharmaceutical measures for pandemic influenza in nonhealthcare settings-international travel-related measures key: cord-316266-6m9g3bdr authors: jones, peter; roberts, sally; hotu, cheri; kamona, sinan title: what proportion of healthcare worker masks carry virus? a systematic review date: 2020-06-24 journal: emerg med australas doi: 10.1111/1742-6723.13581 sha: doc_id: 316266 cord_uid: 6m9g3bdr background: concerns have been raised by healthcare organisations in new zealand that routine mask use by healthcare workers (hcw) may increase the risk of transmission of sars‐cov‐2 through increased face touching. routine mask use by frontline hcw was not recommended when seeing ‘low risk’ patients. the aim of this review was to determine the carriage of respiratory viruses on facemasks used by hcw. methods: a systematic review was conducted with structured searches of medical and allied health databases. two authors independently screened articles for inclusion, with substantial agreement (k=0.66, 95%ci 0.54 to 0.79). studies that at least one author recommended for full text review were reviewed in full for inclusion. two authors independently extracted data from included studies including the setting, method of analysis and results. there was exact agreement on the proportion of virus detected on masks. results: 1233 titles were retrieved, 47 underwent full text review and five studies reported in four articles were included. the studies were limited by small numbers and failure to test all eligible masks in some studies. the proportion in each study ranged from 0 (95% ci 0‐10) to 25% (95%ci 8‐54). no study reported clinical respiratory illness as a result of virus on the masks. conclusions: although limited, current evidence suggests that viral carriage on the outer surface of surgical masks worn by hcw treating patients with clinical respiratory illness is low and there was not strong evidence to support the assumption that mask use may increase the risk of viral transmission. this article is protected by copyright. all rights reserved. during the current novel coronavirus disease 2019 (sars-cov-2, covid-19) pandemic, the ministry of health (moh) and district health boards (dhb) have not recommended routine use of surgical masks for healthcare workers (hcw) in emergency departments (ed) in new zealand (nz). such advice was contrary to the experience of countries that had faced similar pandemics previously who recommended use of masks for ed staff within days of the first cases presenting. 1 2 the initial drivers for this were a belief that the risk to hcw from patients without epidemiological (travel/known contact) risk factors and clinical respiratory illness (cri) and fever was very low and that overuse of masks could jeopardise the available supply later in the pandemic when the prevalence of cri in the population presenting to ed would be higher. this advice was consistent with the contemporaneous world health organisation (who) guidelines on rational use of personal protective equipment (ppe) for coronavirus disease 2019, based on droplets being the most likely mode of virus transmission. 3 however, emerging evidence from the current sars cov-2 pandemic suggests that aerosol and asymptomatic spread are both possible. [4] [5] [6] the case definition in nz subsequently changed to include any respiratory illness regardless of fever or epidemiological risk. evidence has also emerged that as many of 50% of infected people are asymptomatic. 6 7 this prompted a change in advice such that currently mask use is permitted, with warnings that incorrect use of masks may be harmful, including concerns that mask use may "actually increase your risk of covid-19". 8 the aim of this review was to determine the carriage of respiratory viruses on facemasks used by hcw in acute care settings, to inform a recommendation on mask usage in the ed in the setting of an emerging viral pandemic. the primary outcome is the proportion of masks positive for any respiratory viruses. the secondary aim was to determine whether viral carriage on masks used by hcw increased or decreased the risk of cri for staff. structured searches were conducted in medline, embase and cinahl using free text and mesh terms for 'mask'; 'touch'; 'nosocomial infection'; 'contamination' and 'virus' (supplementary file). the final search was run on 23/4/20. these were supplemented by a citation search of included articles. there was no restriction on year or language. two authors independently screened titles and abstracts for relevance and selected articles for full text review. articles were included if they were clinical studies that reported virus detection on masks worn by hcw. experimental studies and computer simulation studies were excluded, as were letters to the editor or opinion pieces. agreement between authors on study selection was substantial, 10 with 97.6% exact agreement (k=0.66, 95%ci 0.54 to 0.79). all studies that at least one author recommended for full text review were reviewed in full for inclusion. two authors independently extracted data from included studies into a table including the setting, type of study, method of analysis and results. there was exact agreement on the proportion of virus detected on masks from the included studies. accepted article 6 data from included studies was shown using descriptive statistics: n, proportion, 95% confidence interval (calculated using graphpad https://www.graphpad.com/quickcalcs/confinterval1/), san diego ca, usa. when it was unclear whether studies reported virus detection on multiple sites on the same mask, we reported the highest and lowest possible proportions. risk of bias was assessed in the studies based on mask selection, method of sampling and detection, and reporting and rated as high, low or unclear. as a secondary analysis of published aggregate data, ethical approval was not required. this review was not registered in a review registry. patients and the public were not involved in this study. the searches retrieved 1233 titles and abstracts, 1186 were either irrelevant or duplicates and 47 underwent full text review (figure 1). forty studies did not report viral presence on masks and three were simulation or theoretical modelling studies 11-13 so were excluded. five studies reported in four articles met the inclusion criteria and were included. [14] [15] [16] [17] the settings, methods, proportion positive and types of viruses are presented in table 1 . the risk of bias for each study is also shown in this table. the proportion in each study ranged from 0 (95% ci 0-10) to 25% (95% ci 8-54). for the largest study with 148 participants, the proportion was 10.1% (95% ci 6-16), shown in figure 2 . none of the included studies reported whether any staff subsequently developed cri related to detectable virus on their masks. this is the first systematic review of viral detection on masks worn by hcw to our knowledge. no studies were conducted in the ed setting in the context of an emerging viral pandemic, which means the evidence relating to ed is indirect. the available evidence suggests that between 0 and 25% of masks worn by staff seeing patients with symptomatic viral illness had a detectable virus and few had virus detected on their faces after doffing masks. where reported, the viral loads on masks were small, and infectivity was not reported. without a control group not wearing masks (which may be considered unethical) it is not possible to say whether this was better or worse than not wearing a mask. the studies ranged in quality, with the main methodological concern being lack of testing of all eligible masks in several studies. there was a tendency for more testing in higher risk settings and masks that were more likely to be contaminated, which would bias towards finding a higher proportion of viral carriage on the tested masks. whilst all five studies used molecular methods to detect viral particles, the method of sampling differed with two studies reported in one article removing the outer layer of the mask, 15 two punching full-thickness 25 mm coupons from the mask 14 17 and one swabbing the surface of the outer layer. 16 three studies reported the level of detection (lod) for the polymerase chain reaction (pcr) assay. 14 16 17 this limits the comparison between studies. with respect to whether wearing masks increases facial touching by hcw, one study found that hcw wearing masks touched their faces during 29% and heads in 8% of care episodes for patients with cri. the median number of mask contacts ranged from one per hour in the near patient zone and five per hour in the far patient zone. 18 in this study, there was no control group to see how often staff touched their faces or heads when not wearing masks. in comparison, a study of medical students in a lecture found the rate of face touching to be 23 times per hour per student (without accepted article 9 masks). 19 another study found that gloves (31%) and gowns (21%) of hcw had more detectable virus than masks after single use caring for a patient with cri (12%). 16 wearing masks for more than six hours continuously and seeing more than 25 patients per shift were associated with a higher chance of mask contamination in one study. 15 none of the included studies reported cri in the staff studied, so it is not possible to say whether detecting virus on the mask leads to a higher risk of contracting cri. systematic review evidence from a previous coronavirus pandemic suggests that general use of masks may be protective for hcw in this setting, 20 21 with a number needed to treat (nnt) of six to prevent one hcw infection (meta-analysis of case control studies). 22 in contrast, there is one case report of a hcw who contracted middle eastern respiratory syndrome-related coronavirus (mers-cov) after performing cpr for one hour in full ppe on a patient with cardiac arrest due to mers-cov pneumonia with gross haemoptysis. 23 during the resuscitation the staff member was seen to adjust their mask and goggles with a heavily soiled glove. general use of masks by staff early in the course of the current 1 and previous 2 the current who advice on use of surgical masks emphasises that these should be prioritised for hcw rather than for general public use in the community. the advice for hcw is to wear a surgical mask when entering rooms "where patients with suspected or confirmed covid-19 are admitted" but does not address the use of surgical masks by hcw in ed who are seeing other patients. 25 26 given the low proportion of virus detection on masks and lack of evidence that this is linked to cri, it may be prudent for hcw in the ed to wear masks routinely in clinical areas as part of a comprehensive bundle of measures to prevent nosocomial infection. this is especially so when this article is protected by copyright. all rights reserved. although limited, current evidence suggests that viral carriage on the outer surface of surgical masks worn by hcw treating patients with cri is between 0 and 25%. no funding was sought or received for this study. the author has no financial or other relationships of interest with any manufacturer of medical masks. accepted article accepted article this article is protected by copyright. all rights reserved. escalating infection control response to the rapidly evolving epidemiology of the coronavirus disease 2019 (covid-19) due to sars-cov-2 in hong kong risk of transmission via medical employees and importance of routine infection-prevention policy in a nosocomial outbreak of middle east respiratory syndrome (mers): a descriptive analysis from a tertiary care hospital in south korea who rational use of personal protective equipment for coronavirus disease 2019 (covid-19) aerosol and surface distribution of severe acute respiratory syndrome coronavirus 2 in hospital wards an early warning system for overcrowding in the emergency department suppression of covid-19 outbreak in the municipality of covid-19: what proportion are asymptomatic? development of simulation optimization methods for solving patient referral problems in the hospital-collaboration environment information-specific-audiences/covid-19-advice-essential-workers-including-personalprotective-equipment/personal-protective-equipment-use-health-care the measurement of observer agreement for categorical data assessment of influenza virus exposure and recovery from contaminated surgical masks and n95 respirators what transmission precautions best control influenza spread in a hospital? transmission of influenza a in a student office based on realistic person-to-person contact and surface touch behaviour assessment of environmental and surgical mask contamination at a student health center --2012-2013 influenza season contamination by respiratory viruses on outer surface of medical masks used by hospital healthcare workers respiratory viruses on personal protective equipment and bodies of healthcare workers healthcare personnel exposure in an emergency department during influenza season environmental contact and self-contact patterns of healthcare workers: implications for infection prevention and control face touching: a frequent habit that has implications for hand hygiene effectiveness of masks and respirators against respiratory infections in healthcare workers: a systematic review and meta-analysis the use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review healthcare worker infected with middle east respiratory syndrome during cardiopulmonary resuscitation in korea taiwan's traffic control bundle and the elimination of nosocomial severe acute respiratory syndrome among healthcare workers infectionprevention-and-control-during-health-care-when-novel-coronavirus-(ncov)-infection-issuspected-20200125 who advice on the use of masks in the context of covid-19. interim guidance 6 covid-19: infection prevention and control guidance accepted article this article is protected by copyright. all rights reserved. this article is protected by copyright. all rights reserved. accepted articlethis article is protected by copyright. all rights reserved. key: cord-317915-0javg3m8 authors: kumar, jagdesh; katto, muhammad soughat; siddiqui, adeel a; sahito, badaruddin; jamil, muhammad; rasheed, nusrat; ali, maratib title: knowledge, attitude, and practices of healthcare workers regarding the use of face mask to limit the spread of the new coronavirus disease (covid-19) date: 2020-04-20 journal: cureus doi: 10.7759/cureus.7737 sha: doc_id: 317915 cord_uid: 0javg3m8 introduction many countries including pakistan are currently using face masks in their pandemic control plans. being highly prevalent, the correct use of these masks is particularly important, as an incorrect use and disposal may actually increase the rate of transmission. the purpose of this study was to investigate the knowledge, attitude, and practices of healthcare workers (hcws) in wearing a surgical face mask to limit the spread of the new coronavirus disease 2019 (covid-19). materials and methods this survey was conducted by interviewing hcws using a questionnaire consisting of the basic demographic characteristics, and the knowledge, attitude, and practices regarding the use of surgical face mask to limit the new covid-19 exposure. each correct answer was scored 1 and each incorrect answer scored 0. the total number of questions was 16, and the final score was calculated and then labeled according to the percentage (out of 16) of correct responses as good (>80%), moderate (60-80%), and poor (<60%). results a total of 392 participants with a mean age of 42.37 ± 13.34 years (341 males and 51 females) were included in the study. the overall final results were good in 138 (35.2%), moderate in 178 (45.4%), and poor in 76 (19.3%). around 43.6% of participants knew about the correct method of wearing the masks, 68.9% knew that there are three layers, 53% stated that the middle layer act as a filter media barrier, and 75.5% knew the recommended maximum duration of wearing it. the majority (88.2%) of participants knew that a cloth face mask is not much effective, around 79.8% knew that used face mask cannot be re-used, and 44.8% knew about the yellow-coded bag for disposal. conclusions knowledge, attitude, and practice of hcws regarding the use of face masks were found to be inadequate. studied hcws had a positive attitude but moderate-to-poor level of knowledge and practice regarding the use of face mask. hcws and general public awareness campaigns regarding the proper use of face mask by utilizing all social media available resources would be helpful during this pandemic. coronavirus disease 2019 (covid-19) is a respiratory illness caused by severe acute respiratory syndrome coronavirus 2 (sars-cov-2), which first emerged in china in december 2019, and has since spread to most countries around the world, resulting in the 2019-2020 coronavirus pandemic [1] [2] [3] . the virus primarily spreads between people through respiratory droplets, which are produced when an infected person coughs or sneezes, or by touching contaminated surfaces or objects and then touching their own mouth, nose, or possibly their eyes. the risk of getting severe covid-19 is higher in health care workers (hcws) who are in close contact with confirmed covid-19 cases. the latest figures show thousands of hcws getting infected with a large percentage of them dying [4] . in order to minimize risk, hcws are required to follow accepted infection control practices. aside from hand hygiene, one of the infection control measures is the routine use of a face mask. many countries including pakistan are currently using face masks in their pandemic plans. face mask works by providing a physical barrier between the mouth and nose of the wearer and potential contaminants in the immediate environment [5] . in resource-limited settings, where the incidence of infectious disease is high and the environmental conditions of hospitals are often poor, hospitals may rely heavily on a face mask to protect medical staff against covid-19 and to prevent cross-contamination among patients and hcws. the use of a face mask among hcws is strongly recommended by the world health organization (who) and the centers for disease control and prevention (cdc) as a standard for transmission-based precaution [6, 7] . moreover, the correct use of these masks is particularly important especially during this time when its use is becoming highly prevalent [8] . the who states that incorrect use and disposal of this mask may actually increase the rate of transmission. if you wear a mask, then you must know how to use it and discard it properly [7] . there is evidence that the hcws have inadequate knowledge and poor practice regarding the use of surgical mask [9] . the purpose of this study was to investigate the knowledge, attitude, and practices of hcws in wearing a face mask particularly a standard surgical face mask to limit the spread of covid-19. this cross-sectional community-based survey was conducted at the department of orthopedic surgery, dr. ruth k. m. pfau civil hospital, affiliated to dow university of health sciences, karachi, pakistan, in march 2020 (one month). the study participants were hcws, that is, consultant, medical officer, postgraduate trainee, house officer, and paramedical staff. a convenient sampling method was used and a sample size of 384 was calculated, considering 5% precision, 95% confidence interval, and 52% as the correct practice of using face masks [5] . keeping a minimum sample size of 384 in mind, a total of 392 patients were registered in the study duration. the study was conducted by interview using a semi-structured questionnaire. the questionnaire was developed with the help of previous literature on the proper use of surgical face mask and the guidelines of the centre for health protection and the cdc and consisted of two parts:(1) basic demographic characteristics (age, gender, job designation), and (2) knowledge, attitude, and practices regarding the use of a face mask to limit covid-19 exposure [5, 10, 11] . prior to the inception of the study, the nature and purpose of the study were explained to each respondent, and informed consent was obtained. for the convenience of analyses, each correct response in the knowledge category, good practice, or positive attitude was scored 1, and each incorrect response, bad practice, or negative attitude was scored 0. the total number of questions was 16, and the final score was calculated and then labeled according to the percentage (out of 16) of correct responses as good (>80%), moderate (60-80%), and poor (<60%). the information obtained from the participants was entered and analyzed using statistical package for the social sciences (sdss) statistics for windows, version 22.0 (ibm corp., armonk, ny, usa). mean with standard deviations were calculated for age and frequency with percentages for categorical variables. face masks are used as a protective barrier to reduce the risk of transmission of microorganisms between patients, hcws, and the environment [12] . however, in order for face masks to provide effective protection, the hcws must have an intimate knowledge of wearing and disposing of those. in this study, 88.5% of participants thought that they knew the proper steps of wearing a surgical face mask; however, only 35% obtained a good score by answering the procedural questions correctly. these results may be because of its simplest design, which leads many participants to mistakenly assume that they know the proper steps of wearing it. there was higher male participation in our study (86.9%) compared with female participation (13%). this finding can be attributed to the higher male enrolment in our institution. in this study, 64.7% of participants obtained an overall moderate-to-poor score regarding the correct usage of a surgical face mask. this low knowledge and practice may be because of recently circulating messages on social media claiming the proper way to wear the threelayered surgical mask, like "colored side facing out if you are sick, and the white side facing out if you want to 'stop the germs from getting in'". this is, however, false and misleading, according to nawhen, a columnist for medical mythbusters malaysia, a non-governmental organization that works to counter myths and inaccurate facts on medical matters; the correct way to wear a surgical mask is by wearing the colored side facing out independent of your health status. the outer colored layer is hydrophobic or is a fluid-repelling layer and its main function is to prevent germs from sticking to it, whereas the inner one is a hydrophilic layer that absorbs moisture from the air we breathe out. if you wear it the other way round, the moisture from the air will stick onto it, thus making it easier for germs to stay there. there is a middle layer that actually filters the microorganism [13] . cloth mask, re-use of a surgical mask, and its extended use are commonly seen in pakistan during the extended outbreak of the covid-19 pandemic. it is highly unlikely for low-income countries that they will be able to provide disposable face masks for that extended period of time and may have to ration the use of these products. in this study, around 88.2% hcws agreed that cloth mask is not as effective as a regular surgical mask and about 79.8% knew that used surgical face mask cannot be re-used. around 75.6% knew the correct maximum duration of using it. other studies also highlighted similar findings concluding that cloth mask, re-use, and extended use of mask makes it ineffective, still hcws are sometimes forced to do it due to the increasing shortage of these masks. we observed that wearing the same mask without removing it between patient encounters and disposing it properly at the end of the day is better than re-using it. still if re-using it due to shortage, it is better to fold the mask in such a way that the outer contaminated surface is held inward followed by storing it in a clean sealable paper bag or container [14] [15] [16] . there is not enough evidence to prove that wearing a surgical mask protects every person from covid-19. the who currently recommended that only hcws and people who are ill and those who are caring for the ill need to wear a mask to protect themselves from covid-19. however, in low-income countries like pakistan, where the incidence of infectious disease is high and the hospital environmental conditions are often poor, our hcws rely almost entirely on a face mask to limit the spread of covid-19 [17] . the who established a color-coded bin system for proper disposal of biomedical waste in hospitals [18] . however, when it was asked from our participants, 44.9% disposed it in the yellow-coded bag for disposal of face mask; this shows poor knowledge of hcws regarding the safe disposal of biomedical waste. some of the limitations of this study include the cross-sectional nature of study design limited to a single governmental hospital. further longitudinal studies should be carried out on a larger sample size, and both private and government hospitals should be included before the results could be generalized. moreover, different types of masks can be compared. knowledge, attitude, and practice of hcws regarding the use of surgical face masks were found to be inadequate. studied hcws had a positive attitude but moderate-to-poor level of knowledge and practice regarding the use of surgical face mask. hcws and general public awareness campaigns regarding the proper use of face mask by utilizing all social media available resources would be helpful during this pandemic. rd: features, evaluation and treatment coronavirus (covid-19). statpearls. statpearls publishing epidemiology, causes, clinical manifestation and diagnosis, prevention and control of coronavirus disease (covid-19) during the early outbreak period: a scoping review world health organization declares global emergency: a review of the 2019 novel coronavirus (covid-19) clinical course and risk factors for mortality of adult inpatients with covid-19 in wuhan, china: a retrospective cohort study use of face masks in a primary care outpatient setting in hong kong: knowledge, attitudes and practices. public health guideline for isolation precautions: preventing transmission of infectious agents in health care settings advice on the use of masks in the community, during home care and in healthcare settings in the context of the novel coronavirus ( 2019-ncov) outbreak: interim guidance wearing face masks in public during the influenza season may reflect other positive hygiene practices in japan how effective are face masks in operation theatre? a time frame analysis and recommendations use mask properly knowledge, perceptions and practices of healthcare workers regarding the use of respiratory protection equipment at iran hospitals show your colours: only one way to wear surgical masks correctly, with the coloured side out use of cloth masks in the practice of infection controlevidence and policy gaps a cluster randomised trial of cloth masks compared 2020 kumar et al. cureus 12(4): e7737. doi 10healthcare workers contamination by respiratory viruses on outer surface of medical masks used by hospital healthcare workers covid-19) advice for the public: when and how to use masks safe management of wastes from health-care activities human subjects: consent was obtained by all participants in this study. dow university of health sciences and dr. ruth k. m. pfau civil hospital issued approval ortho/duhs/020/2020. animal subjects: all authors have confirmed that this study did not involve animal subjects or tissue. conflicts of interest: in compliance with the icmje uniform disclosure form, all authors declare the following: payment/services info: all authors have declared that no financial support was received from any organization for the submitted work. financial relationships: all authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. other relationships: all authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work. key: cord-342666-7el8o6qq authors: mahmood, syed uzair; crimbly, faine; khan, sheharyar; choudry, erum; mehwish, syeda title: strategies for rational use of personal protective equipment (ppe) among healthcare providers during the covid-19 crisis date: 2020-05-23 journal: cureus doi: 10.7759/cureus.8248 sha: doc_id: 342666 cord_uid: 7el8o6qq as the coronavirus 2019 (covid-19) began spreading globally with no clear treatment in sight, prevention became a major part of controlling the disease and its effects. covid-19 spreads from the aerosols of an infected individual whether they are showing any symptoms or not. therefore, it becomes nearly impossible to point exactly where the patient is. this is where personal protective equipment (ppe) comes in. these are masks, respirators, gloves, and in hospitals where the contact with the infected and confirmed patient is direct, also gowns or body covers. the ppes play a major role in the prevention and control of the covid-19. the ppe is able to prevent any invasion of the virus particles into the system of an individual which is why it is an essential item to have for healthcare workers. due to the high demand for ppes all around the world, it is important to optimize the use of protective gear and ration the supplies so that the demand are met. however, there are guidelines recommended by the world health organization (who) and the centers for disease control and prevention (cdc) to maintain the supply in the wake of this increased demand of ppe, how the manufacturers should track their supplies, and how the recipients should manage them. various strategies can be used to increase the re-use of ppes during the covid-19 pandemic that has modified the donning and doffing procedure. personal protective equipment (ppe) is an article used to prevent the wearer from coming in contact with hazardous, infectious, chemical, radiological, electrical, and physical agents. it contains components illustrated in figure 1 [1] . the surge in demand and misuse of ppe has led to an acute shortage of protective gear, endangering the lives of healthcare workers [2] . more than 9,000 healthcare workers (hcw) in the united states (us) and more than 17,000 in italy have been infected with covid-19 [3] [4] . a total of 444 hcw in pakistan have been exposed to covid-19 as of april 29, 2020 [5] . many doctors are performing their duty without any ppe and are at high risk of becoming infected [6] . there have been peaceful protests all over the world by doctors, nurses, and other healthcare professionals demanding ppe. 1 2 3 4 5 in the wake of the covid-19 pandemic, ppe plays a significant role, with face masks and gloves being the most essential. doctors, nurses, and other frontline healthcare responders are using them to minimize the risk of contaminated contact or droplet exposure. some studies suggest that the psychological impact of ppe is such that individuals using them might feel more protected than they actually are in reality [7] . it should be ensured that the wearer practices hand hygiene before wearing and after removing the protective gear. also, an appropriate method for its disposal should be considered. the primary mode of transmission of coronavirus is known to be droplet or contact-based. infected individuals are prone to spread the virus while coughing, sneezing, or speaking. this micro virus, when ejected, can travel up to a distance of six feet. wearing a face mask, along with other precautionary measures like hand hygiene and self-isolation, limits the transmission of infectious agents [8] [9] . initially, the usage of masks among the general public was highly controversial. experts discouraged healthy people from wearing masks due to the scarce supply. this equipment was reserved for those in direct contact with infected patients [10] . however, the rapid rise in the degree of local transmission has caused many countries to allow their citizens to wear nonmedical/cloth masks, along with practicing social distancing [9, 11] . evidence-based studies reveal that the concomitant use of household (non-medical) face masks, as well as using a proper handwashing regimen, reduces the probability of local transmission, thereby decreasing the death toll [12] . it should be noted that according to the world health organization (who) guidelines, medical masks and respirators should only be reserved for healthcare workers [10] . factors that determine the efficiency of face masks are listed in table 1 [13]. the shape of the mask the main types of masks being used are respirators, medical masks, and non-medical/cloth masks. these are protective equipment which provides an almost accurate facial fit and effective filtration of airborne particles. they provide a proper seal around the mouth and nose, providing optimal protection. according to the recent who, cdc, and fda guidelines, such masks are only reserved for healthcare providers [10, [13] [14] . the fda has labeled these masks as single-use, disposable devices; however, in cases of shortage in supplies, these can be sterilized and reused [14] . while the respirator masks are highly efficient, they still do not provide complete protection. improper and misuse of these masks can lead to the spread of infection in the user [15] . these are thin, pleated, and disposable masks that protect the user from inhaling dust particles, contaminated liquid droplets, and bacteria. they are usually two layers thick and made from unwoven fabric. these masks only act as a physical barrier between the user's nose and mouth and the infected environment. they do not possess a proper seal and are less effective than respirators. these are loose masks, which allow comfortable breathing and reduce transmission probability [14] . according to recent studies, asymptomatic and pre-symptomatic carriers of the novel coronavirus have been detected and can transmit the virus. in the face of this discovery, cdc experts recommend that the general public uses non-medical/cloth coverings to shield their mouth and nose. these textile masks are made up of layers of cloth. some of them also possess a paper towel layer, which increases the filtration capability. they do not offer full protection but, along with other precautionary measures, are useful to slow down the spread of coronavirus [16] . as a general safety precaution, every frontline healthcare worker (hcw) should know which ppe needs to be used in different clinical settings [17] [18] . 1) under any clinical setting where there is a risk of getting infected, the individual should don (put on) a medical face mask, gloves, gown, and eye protection, 2) if the hcw is more than 2 meters away from the patient, he/she should use a fluid-resistant medical face mask with or without eye and face protection, depending on whether there is exposure to flashes or droplets. 3) in case of an ongoing aerosol-generating procedure (agp), all individuals present should wear a respirator, face and eye protection, gloves, and long-sleeved fluid-repellent gown. it is essential that every hcw should know the proper way to put on (donning) and remove (doffing) ppe. any mistake in doing so can render the individual exposed to infections agents. according to standard infection prevention and control (ipc) guidelines, ppe is a single-use, disposable item. however, due to the current shortage of ppe, health care providers are challenged to rationally use the limited supplies by decontaminating and reprocessing them. it should be noted that there is no proven effectiveness of these practices and priority is given to the rapid manufacture of protective items [21] . improper or inadequate decontamination of equipment before reuse is unsafe and can pose serious threats [22] . when disinfecting ppe, it is important to keep in mind the efficacy of the method used, check for any residual toxicity, and make sure that the functional integrity of the material is maintained. general strategies include following the manufacturer's guidelines to disinfect and reprocess the ppe. routine inspection of protective material should be carried out, along with the replacement of the equipment if the integrity is not maintained or it is damaged. 1) usually cleaning prior to disinfection is required. respirators and medical masks lose their protective property when they undergo cleaning. 2) considering the current conditions, these items can be worn by a single hcw for multiple shifts. factors, such as humidity and shelf-life, limit their use. 3) medical masks can be reprocessed using the environment protection agency (epa)registered disinfectants. filtering facepiece respirators can be decontaminated using vaporous hydrogen peroxide, moist heat, and bleach solution. gowns 1) submerge in hot water and detergent, then thoroughly scrub the gown. 2) afterward, soak in 0.05% chlorine solution for about 30 minutes. 3) rinse in clean water and ideally allow drying in the sun. 4 ) gowns having small holes and tears could be mended whereas worn out gowns should be discarded. 1) clean first the inside and then the outside surface of the visor using a detergent-soaked clean cloth. 2) clean the outside of the visor with a clean cloth saturated with disinfectant. 3) wipe the outside of the visor with clean water. 4) use towels or dry air to completely dry the visor. 1) immerse in warm water and neutral detergent solution. 2) rinse with clean water. 3) wipe with disinfectant and then again rinse with clean water. 4) dry completely using towels or dry air. potentially infectious medical waste (pimw), such as covid 19 testing kits and ppe, have a serious risk of coming in contact with infectious bodily fluids. these materials should be kept safely on site (hospitals, testing centers) in secure containers. they should then transferred to storage facilities, where they are disinfected and disposed of off to landfill sites [23] . individuals responsible for waste management should take caution and should wear appropriate gear. it is extremely critical to properly decontaminate and dispose of any waste material that could infect people who come in contact with it. the escalating demand for ppe has given rise to new state and local strategies to ensure the careful optimization of available resources. this policy helps reserve the reduced amount of ppe for the most critical conditions. as the situation improves and the ppe supply is sufficient again, the state can return to its conventional ppe guidelines. the following strategies should be observed to overcome the shortage of ppe [24] . there is a difference in the demand and supply of ppe, with severe shortages in supply on all fronts. it is crucial that all the equipment is used with care to prevent wastage, to ensure a continuous supply of protective equipment despite limited production [1, 22] . 1) the healthcare professionals who are working with patients of covid-19 and are in direct contact should have ppe consisting of gloves, gowns, masks, face shields, and goggles. 2) the same respirator can be used while examining multiple patients at a time. since the shortage of supply is a fact in most places, it is recommended to keep wearing a single one for multiple patients than to not have any respirator on. 3) hcw performing or assisting with invasive procedures should be wearing respirators, eye protection (like goggles), and a face shield aligned with the gown and gloves. if the gowns allow fluid to pass through, an additional layer of protective coverage like an apron should be worn. 4) people who are taking care of the sick at home should be provided with medical masks at home for their own protection and to limit the spread of the disease. 5) individuals who remain asymptomatic or do not show any signs of illness can use nonmedical masks and should not opt for medical masks. inappropriate use of medical masks may increase the demand and can also impede the supply to professionals who need them the most. the need for ppe can be minimized by the following interventions [25] : 1) limit patient contact and use alternate tools, such as telemedicine, for non-emergency cases. 2) make sure that no personnel who is not immediately needed for the patients' care should enter the premise of the covid-19 ward that should be a separated and isolated area. the visitors should either not be allowed at all or should have minimal contact with the patients. 3) all non-urgent procedures/appointments should be postponed. 5) ppe should be used beyond their shelf life making sure they are not worn out or damaged. 6) in the case of the absolute absence of ppe, alternate methods for barrier control (e.g., glass shields) should be employed. these practices do not guarantee the absolute safety of healthcare professionals, and their effectiveness is questionable. however, under the present circumstances, these crisis strategies given by the cdc should be duly addressed. the supply should be monitored and demand adjusted [21, 26] . this can be done using the following methods: 1) use of rational quantification-based forecasts regarding ppe. this helps in rationing available supplies to meet the demand. 2) the request for ppe from countries, as well as major responders, should be monitored and controlled. the distribution of ppe to healthcare institutions should be controlled and monitored. 3) to avoid stock duplication, a centralized request management system should be applied that takes notice of whether the stock management rules are being followed or not. this helps in controlling the wastage and overstock. 4) keep a check on the end-to-end distribution of ppe. due to the recent ease in lockdown measures and the commencement of the holy month of ramadan in the muslim world, an abrupt rise in public gatherings is feared. therefore, it is highly critical that ppe's should be used in all clinical and non-clinical settings. citizens should use a cloth barrier while stepping out of the house and public gatherings should be strictly avoided. the proper protocol should be followed when healthcare professionals consider reusing ppe. as pakistan is one of the major distributors of ppe throughout the world, it has set an exemplary approach during this pandemic. the pakistani government and national disaster management authority (ndma) have made tireless efforts to increase the manufacturing and distribution of ppe. moreover, many non-governmental organizations (ngos) and medical students have come forward to combat this deadly disaster and distribute ppe to those fighting on the frontline. disclosures risk at work -personal protective equipment (ppe) shortage of personal protective equipment endangering health workers worldwide health-care workers have been infected with the coronavirus 000 italian health workers infected with virus: study infections amongst healthcare workers increase by 75pc in a week uk doctors finding it harder to get ppe kit to treat covid-19 patients use of ppe in response of coronavirus (covid-19): a smart solution to global economic challenges rational use of face masks in the covid-19 pandemic keep your distance to slow the spread advice on the use of masks in the context of covid-19 recommends people wear cloth masks to block the spread of covid-19. surgical masks and n95 respirators should be reserved for health care workers face masks against covid-19: an evidence review 13. n95 respirators and surgical masks n95 respirators and surgical masks (face masks improper use of medical masks can cause infections use of cloth face coverings to help slow the spread of covid-19 accessed updated guidance on personal protective equipment (ppe) for clinicians personal protective equipment use in health care use personal protective equipment (ppe) when caring for patients with confirmed or suspected covid-19 operational considerations for personal protective equipment in the context of global supply shortages for coronavirus disease 2019 (covid-19) pandemic: non-us healthcare settings rational use of personal protective equipment ( ppe) for coronavirus disease ( covid-19) : interim guidance water, sanitation, hygiene and waste management for covid-19 strategies to optimize the supply of ppe and equipment sourcing personal protective equipment during the covid-19 pandemic critical preparedness, readiness and response actions for covid-19: interim guidance in compliance with the icmje uniform disclosure form, all authors declare the following: payment/services info: all authors have declared that no financial support was received from any organization for the submitted work. financial relationships: all authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. other relationships: all authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work. key: cord-347390-xz5a99cr authors: ray, saikat sinha; park, you-in; park, hosik; nam, seung-eun; kim, in-chul; kwon, young-nam title: surface innovation to enhance anti-droplet and hydrophobic behavior of breathable compressed-polyurethane masks date: 2020-08-07 journal: environ technol innov doi: 10.1016/j.eti.2020.101093 sha: doc_id: 347390 cord_uid: xz5a99cr with the emergence of the coronavirus disease (covid-19), it is essential that face masks demonstrating significant anti-droplet and hydrophobic characteristics are developed and distributed. in this study, a commercial compressed-polyurethane (c-pu) mask was modified by applying a hydrophobic and anti-droplet coating using a silica sol, which was formed by the hydrolysis of tetraethoxysilane (teos) under alkaline conditions and hydrolyzed hexadecyltrimethoxysilane (hdtms) to achieve hydrophobization. the modified mask (c-pu/si/hdtms) demonstrated good water repellency resulting in high water contact angle (132°) and low sliding angle (17°). unmodified and modified masks were characterized using attenuated total reflection-fourier transform infrared (atr-ftir) spectroscopy, scanning electron microscopy (sem), energy-dispersive x-ray spectroscopy (eds), and x-ray photoelectron spectroscopy (xps). a drainage test confirmed the strong interaction between the mask surface and coating. moreover, the coating had negligible effect on the average pore size of the c-pu mask, which retained its high breathability after modification. the application of this coating is a facile approach to impart anti-droplet, hydrophobic, and self-cleaning characteristics to c-pu masks. this mask is based on porous filter technology which controls the pores to form the ideal 74 density and size for trapping pollen sized particles. in addition to that, it can be reused even 75 after 2-3 washes. above all, it is highly cheap and commercially available that delivers 76 overwhelming air permeability. nonetheless, due to high water absorbency as a result of the 77 hydrophilicity of the masks diminishes their water-repelling properties but may be solved by a 78 coating that imparts hydrophobic as well as anti-droplet features. in this study, a simple 79 fabrication approach was demonstrated wherein tetraethyl orthosilicate (teos) is hydrolyzed 80 in a h2o/ethanol solution mixture to form silane sol and hexadecyltrimethoxysilane (hdtms) 81 is hydrolyzed in ethanol solution to form an alkylsilanol. until now, fluorinated based material 82 or coating has been used as one of the effective agents for lowering the surface free energy. 83 but recent research suggests that, fluorinated materials are expensive as well as not 84 environmentally friendly [11] . in this study, a non-fluoro compound, 85 hexadecyltrimethoxysilane (hdtms), an organosilane with a c-16 hydrocarbon tail, has been 86 utilized to modify the surface of silica. typically, hdtms is an amphiphilic molecule 87 consisting of hydrophilic head where a central silicon atom is attached to three -och3 groups, 88 and its hydrophobic tail is composed of an alkyl chain formed by a straight succession of fifteen 89 ch2 groups and one ch3 group at its end. the results in long-chain alkylsilane with low surface 90 free energy has been introduced onto sio2 grafted surfaces, hence, generating the modified 91 hydrophobic surface [12] . the c-pu mask sample was first treated with the silica sol and then the same sample was as far as the structural aspect is concerned, the inner spongy layer is kept unchanged and was 117 found to be hydrophilic in nature that helps in absorbing moisture. in addition to that, the 118 compressed polyurethane masks are non-allergic in nature that are comfortable with face/skin. however, the outer layer has been chemically modified that was observed to be hydrophobic 120 for droplet/ splash resistance application. moreover, the porous structure demonstrates the 121 capability of high air permeability. thus, this dual layer concept has been applied in the present 122 study to reduce the chance of contamination from water droplets or splashes. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 was constantly stirred for one and half hour to produce the silica sol. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 the methodology for fabricating a stable hydrophobic coating on a mask surface utilizing silica 202 sol as well as hdtms is discussed in materials and methods section and summarized in 203 scheme 1. silica sol specimens (si-1 and si-2) with different particle sizes were synthesized 204 by adjusting the content of nh4oh while generation of the silica sol as indicated in table 1 . the polydispersity index (pdi) value can be used to evaluate the average uniformity of a 206 particle or nanoparticle dispersion [20, 21] . interestingly, values greater than 0.8 indicate low 207 stability for a drug delivery/nano-delivery/colloidal system. 208 si-2 6 ml 100 ml 6 ml 0.5 the particle size distribution of the silica samples (si-1 and si-2) is shown in figure 3 . it is 211 evident that the average particle size of the silica sol escalates as the content of nh4oh is 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 water contact angle, even after 15 min. it is worth noting that the c-pu/si-2/hdtms mask 252 records a higher water contact angle than the c-pu/si-1/hdtms mask, which is ascribed to 253 the increased aggregation and average particle size of the si-2 sol (figure 3) . the c-pu/si254 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 j o u r n a l p r e -p r o o f journal pre-proof to base produced from the liquid and the surface. as per table 2 , droplet volume was kept 263 consistent and droplet height has been investigated to examine the degree of wetting state of 264 pristine and modified mask. interestingly, higher droplet height indicates higher contact angle 265 while keeping the droplet water volume (10 µl) same. this outcome has been found to be 266 consistent as indicated in figure 6 . 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 the morphology of unmodified and modified masks was investigated using sem, refer to concluded that the air permeability or breathability of these masks aren't significantly changed. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 indicates higher air permeability that leads to high breathability. in order to examine the 302 internal structure, the cross-sectional morphology has been thoroughly studied that indicates 303 same internal structure for both masks. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 the thickness of the masks was evaluated using a digital thickness gauge at ten different 327 locations and averaged for further calculations. typically, face masks are made in various 328 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 "mechanical" collection mechanism that involves inertial impaction, interception and 335 diffusion. this mechanism helps in trapping particles without increasing breathing resistance 336 [32]. hence, thicker the filter, the better the protection from foreign particles. however, it 337 shouldn't be too thick as it may resist air permeability if the filter is too dense. but, in this 338 study, polyurethane material was found to be extremely porous. material. this crucial factor is influenced by the porosity of the material, that in turn impacts 343 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 j o u r n a l p r e -p r o o f therefore, air permeability can also be correlated based on porosity value. material permeability is often evaluated with respect to the porosity of the fabric. the porosity 346 of the material (ε) has been evaluated as follows [34] : where wwet and wdry represent the weights of the wet and dried material (g); ρwater represents 349 water density in g/cm 3 ; whereas; a and h indicate the area (cm 2 ) and thickness (cm), 350 respectively, of the material. figure 12 shows the measured porosity of various mask materials. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 the durability of the surface coating was qualitatively investigated by conducting a water jet 403 impact test. in this study, the water jet was quickly repelled by the modified mask and the 404 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 features, evaluation and treatment 440 coronavirus (covid-19), statpearls coronavirus disease 2019 (covid-19): situation report the epidemiology and pathogenesis of coronavirus disease (covid-448 19) outbreak face mask use and control of respiratory virus transmission in households, emerging 451 infectious diseases to 453 mask or not to mask: modeling the potential for face mask use by the general public to curtail the 454 covid-19 pandemic a flexible nanoporous template 456 for the design and development of reusable anti-covid-19 hydrophobic face masks how to safely wear and take off a cloth face covering an 460 efficient ethanol-vacuum method for the decontamination and preparation of hexadecyltrimethoxysilane-modified silica 463 nanocomposite hydrosol and superhydrophobic cotton coating superhydrophobic cotton fabrics prepared by one-step water-466 based sol-gel coating silica nanocomposite based hydrophobic functionality 468 on jute textiles inorganic micro-and nanostructured implants for 470 tissue engineering emerging developments in the use of electrospun fibers and 472 membranes for protective clothing applications the environmental dangers of employing single-use face 475 masks as part of a covid-19 exit strategy mask-induced contact dermatitis in handling covid-19 outbreak a thermodynamic model of contact angle hysteresis polymer-based multifunctional nanocomposites and their applications physical characterization of 483 nanoparticle size and surface modification using particle scattering diffusometry eco-friendly curcumin-loaded 486 nanostructured lipid carrier as an efficient antibacterial for hospital wastewater treatment size, volume fraction, and 489 nucleation of stober silica nanoparticles porous biodegradable polyurethane 491 nanocomposites: preparation, characterization, and biocompatibility tests comparison between sioc thin film by plasma enhance chemical vapor deposition and 494 sio 2 thin film by fourier transform infrared spectroscopy review on blueprint of designing anti-wetting polymeric 497 membrane surfaces for enhanced membrane distillation performance synthesis and characterization of nanocomposite ultrafiltration membrane (psf/pvp/sio2) and performance 500 evaluation for the removal of amoxicillin from aqueous solutions durable, self-healing, 503 superhydrophobic fabrics from fluorine-free, waterborne, polydopamine/alkyl silane coatings hydrophobic/hydrophilic patterned surfaces for 506 directed evaporative preconcentration design of super-hydrophobic microporous 508 polytetrafluoroethylene membranes morphological and structural 510 developments in nanoparticles polyurethane foam nanocomposite's synthesis and their effects on 511 mechanical properties performance of fabrics for home-made masks against spread 513 of respiratory infection through droplets: a quantitative mechanistic study, medrxiv a short review on the development of novel face masks during 515 covid-19 pandemic nanotechnology in textiles: theory and application air permeability & porosity in spun-laced fabrics, fibres and textiles in eastern 519 contact angles and wettability: 521 towards common and accurate terminology typically, facets of real surfaces such as surface roughness and chemical heterogeneity, may key: cord-266173-gmz6oxf6 authors: tino, rance; moore, ryan; antoline, sam; ravi, prashanth; wake, nicole; ionita, ciprian n.; morris, jonathan m.; decker, summer j.; sheikh, adnan; rybicki, frank j.; chepelev, leonid l. title: covid-19 and the role of 3d printing in medicine date: 2020-04-27 journal: 3d print med doi: 10.1186/s41205-020-00064-7 sha: doc_id: 266173 cord_uid: gmz6oxf6 nan as of march 12, 2020, the world health organization classified coronavirus disease 2019 (covid-19) as a pandemic, at the time of writing affecting nearly every country and territory across the globe [1] . during this time of social and economic despair, global healthcare systems are under critical strain due to severe shortages of hospital beds and medical equipment. patients with covid-19, the disease caused by severe acute respiratory syndrome coronavirus 2 ( fig. 1) , are at risk for acute respiratory distress syndrome (ards) and a fraction will require high-level respiratory support to survive [2] . additionally, significant strain has been placed on personal protective equipment (ppe) supplies required to protect the healthcare workers helping to treat critically ill patients during this pandemic. at the time of writing, there are active disruptions of medical supply chains throughout europe and in the united states at the hospital level, particularly in the states of new york and washington. the purpose of this editorial is to highlight recent (as of april 1, 2020) initiatives and collaborations performed by companies, hospitals, and researchers in utilising 3d printing during the covid-19 pandemic and to support local 3d printing efforts that can be lifesaving. the 3d printing community can refocus its medical attention internationally, capitalizing on centralized large-scale manufacturing facilities as well as locally distributed manufacturing of verified and tested cad files. in addition, there are multiple medical, engineering, and other societies and groups that can pull together to work on common needs, many of which are outlined in this editorial. while models discussed here are primarily opensource necessities available at the time of writing, the cad file resources referred to in this editorial are intended for a discussion of an evolving collection of ready-to-print models and links to the relevant resources to aid in supporting urgent medical response. an example collection can be found at the nih 3d print exchange. we must acknowledge that at the time of writing, the clinical effectiveness of many of the devices manufactured according to the cad files described in this editorial has not been tested and many of these devices have not been approved for frontline clinical use by relevant regulatory bodies. the authors of this editorial cannot guarantee clinical effectiveness of the presented devices and would urge consideration of these resources at the users' discretion and only where no medically cleared alternatives are available. the recent impact of covid-19 in italy has caused regional shortages of key equipment, including masks and hoods for non-invasive ventilation in cpap/peep respiratory support. crucially, venturi valves, key components of such respiratory support equipment [3] proved difficult to reproduce or substitute in the setting of these shortages. while venturi valve design is subject to copyright and patent covers, certain emergencies resulting in life-or-death decisions may justify full use regardless of intellectual property, in the appropriate clinical setting. this critical demand has resulted in the 3d printing community of physicians and engineers at a local italian startup isinnova successfully developing methods for manufacturing these valves to bolster local supply [4] . additional methods of bolstering local ventilator supply include the use of a single ventilator for multiple patients with a 3d printed ventilator splitter. fortunately, the us fda does not object to the creation and use of certain devices such as the t-connector that meet specifications described in the instructions provided to the fda for use in placing more than one patient on mechanical ventilation when the number of patients who need invasive mechanical ventilation exceeds the supply of available ventilators and the usual medical standards of care have been changed to crisis care in the interest of preserving life. the fda's "no objection" policy in this regard applies during the duration of the declared covid-19 emergency. access to such models is still limited for many local 3d printing community members and will require close collaboration between companies and hospitals to ensure adequate manufacturing approaches and appropriate clinical use. the reverse-engineered 3d printable model of the isinnova valve is not widely available at the time of writing, with the authors maintaining the position that such resources should be adequately evaluated and used only when such equipment is not available from the original manufacturers. ongoing efforts by the engineers at isinnova are focusing on developing creative adaptations of existing products for respiratory support, for example by adapting a snorkelling mask into a non-invasive ventilator [5] . most recently, non-adjustable venturi valve designs were developed and made available by the grabcad user filip kober [6]. these valve designs achieve specific levels of inspired oxygen (fio 2 ) at set rates of supplemental oxygen supply (fig. 2) . model porosity may inadvertently alter intended fio 2 levels, requiring the use of printing technologies that ensure airtight parts. automated ventilators with flow-driven, pressurecontrolled respiratory support systems featuring safety valves, spontaneous respiration valves, and flexible membranes present an ongoing open source design challenge with some promising results, including the illinois rapid-vent design. while sourcing ventilators and ventilator parts from existing manufacturers is the clearly preferred option when feasible, the supply of these crucial devices is inadequate in many areas. a solution currently being applied to this challenge in europe and the united states is the creation of 3d printed ventilator splitters and adjustable flow control valves, such as the no2covid-one valve, to be able to adapt a single ventilator for use with multiple patients who have different oxygen requirements [7]. we anticipate new creative solutions for such increasingly complex challenges from emerging international open source design efforts such as the montreal general hospital foundation code life ventilator challenge [8] as the covid-19 health crisis emerges. quarantine measures in the setting of this pandemic have sparked tension and fear among the lay public. an unfortunate consequence of this is unnecessary panic buying, leaving those who need these products, such as health care workers, in limited supply. members of the global 3d printing community have designed a plethora of reusable personal protective equipment devices with insertable filters, primarily manufactured using low-cost desktop filament extrusion printers. to our best knowledge, ppe items in need at the time of writing include splash-proof face shields, surgical masks, n95 masks, n90 masks, powered air-purifying respirator (papr) hoods, and controlled air purifying respirator hoods (capr). many of the ppe designs highlighted here are works in progress, and the effectiveness of locally manufactured derivatives of these devices should be carefully evaluated locally. additionally, these ppes are intended to be reusable, and therefore local manufacturing efforts should carefully consider compatibility with the available sterilization techniques and the condition of all ppe devices should be monitored following sterilization on an ongoing basis. to ensure the best fit, personalizing these masks may be achieved by printing in several sizes, experimenting with flexible materials, or surface scanning intended users' faces and carrying out additional cad to virtually fit these masks on an individual basis [9] . while this individualized approach may limit manufacturing throughput, the improved functionality may justify this impact on throughput. in general, throughput may be the most challenging factor to address in developing 3d printed ppe in smaller-scale local 3d printing laboratories. many of the models highlighted here require several hours to print on conventional desktop printers. while many 3d printing laboratories can parallelize this process with multiple printers, throughput will likely remain limited to dozens of masks per printer and 3d printing resources should therefore be assigned judiciously. this section refers to ppe used to protect the wearer from airborne particles and liquid contaminants on the face. for the purpose of this article these are referred to as "face masks" and there are several 3d printed solutions. the fda, nih 3d print exchange, and the united states veterans' association are working together in this regard, including developing a prototype n95 mask currently being tested. in the meantime, numerous face mask designs have been proposed and tested by individual users, researchers, physicians, and commercial entities alike with variable degrees of success. in all cases, the end users must clearly understand that only prototypes are available at this point and local testing procedures, potentially modified from established routine n95 fit testing, are crucial to assess the quality of ppe. the copper3d nanohack mask [10] demonstrates the limitations of the community-generated designs and the need for design improvements based on local testing and available technical base. this mask can be printed with polyactic acid (pla) filament as a flat piece, and is intended to be subsequently manually assembled into its final three-dimensional configuration after heating to a temperature of 55-60°c (131-140°f) via forced hot air (e.g. a hairdryer) or by submerging it in hot water (fig. 3) . crucially, all seams must be manually sealed to ensure an airtight fit. the mask includes a simple air intake port into which two reusable filters may be inserted, with a screw-in cover to hold the filters in place. this design fig. 2 open-source non-adjustable venturi valve design for an fio2 of 33% at supplemental oxygen flow rate of 10 l per minute. the cross-sectional view (above) demonstrates the inner structure of this device with a small oxygen port (light blue) and a larger air intake (left) has several drawbacks. due to the flat design, only one mask can be printed at a time on most desktop printers, limiting throughput. practically, our initial tests demonstrate difficulties folding these masks created using conventional pla filament, with significant gaps along the seams that are difficult to mitigate. if successfully sealed, the mask may provide limited airflow for some users and a second breathing port, achievable by mirrorimaging the port-bearing half of the mask, may need to be added. as a result of multiple limitations, this mask is currently undergoing revisions by the original designer. the hepa mask designed by the thingiverse user kvatthro [11] may be manufactured using most desktop printers. pla filament is suggested due to the possibility of fitting the mask to the individual user after heat exposure, which is important to ensure the best possible air seal in field conditions. the mask comes in male and female variants and allows space for an exchangeable hepa filter insert within a port at the front of the mask (fig. 4) . a similar design has been proposed by the chinese company creality [12], with a different configuration of the filter holder, intended for insertion of layers of folded fabric or filters (fig. 5) . the creality goggles require separately sourcing transparent plastic inserts, which may be obtained from repurposed household items. as with all masks, judicious testing for seal adequacy and experimentation with sizing and materials are required for implementation. the lowell makes mask is a variant of the replaceable front filter design which offers the benefit of printing without supports or adhesion [13] (fig. 6) . the mask is intended to be lined with a foam padding on the inside. while addition of elements such as foam padding to reusable ppe like the lowell makes mask improves user comfort, this may impact the selection of sterilization approaches and must be considered carefully. finally, additional creative designs, such as the "flexible mask valvy" by the thingiverse user iczfirz [14] have demonstrated the feasibility of printing pla masks on a cloth bed platform. this design allows for reusability with dedicated filter inserts. additional variations on personal protective equipment include protective face shields, such as those designed by prusa [15] . these simple devices feature a reusable printable headpiece to which a separately sourced transparent sheet of plastic can be attached to create a face shield, protecting the user's eyes and mouth (fig. 7) . face shield designs completely bypassing 3d printing have also emerged. covid-19 requires meticulous precautions in limiting person-to-person spread via direct contact with objects or surfaces such as door handles. simple interventions limiting such transmission can have far-reaching consequences. transmission from door handles may be problematic in public and in medical centers which usually have a large number of doors designed for patient privacy or ward control, especially during periods of isolation during pandemics. while meticulous and regular surface cleaning partially addresses this issue, modifications of a range of handles to allow alternative mechanisms for opening doors without direct skin-to-surface contact have been recently developed at materialise. these ready to print door handle accessories [16] can be manufactured on most 3d printing platforms (fig. 8) . current cdc guidelines for disinfection and sterilization in healthcare facilities define three major levels of pathogen eradication: cleaning, disinfection, and sterilization [17] . cleaning is defined as removing visible soil and organic material. the definition of disinfection varies based on whether it is low or high level, and refers to removing many or all microorganisms respectively, under optimal conditions. sterilization is defined as assured complete eradication of all microbial life on a given piece of equipment. based on analogy with the established operational parameters for reusable respirators [18], high-level disinfection is likely the most appropriate modality when dealing with reusable 3d printed personal protective equipment. recommended disinfection agents range from concentrated alcohol to quaternary ammonium compounds, and the precise agent selection would likely vary depending on the utilized material and printing technology. initial testing of the preferred/available disinfection mode may be conducted prior to scaling up manufacture, in consultation with local hospital policies and consideration of disinfection material availability. ensuring compatibility with widely available common household chlorine-based or hydrogen peroxide-based compounds may be prudent for individual users. in all cases, consultation with local hospital guidelines regarding the frequency, nature, and acceptability of disinfection and sterilization of reusable equipment should be followed. for devices requiring sterilization, manufacturer specifications for printing materials should be consulted. for example, 3d printed nasal swabs needed to expand testing in the us must not only be safe and provide adequate sample, but also must be sterilized and packaged appropriately for testing and eventual clinical use. where available, limited physical impact methods such as hydrogen peroxide gas plasma or ionizing radiation may be the preferred means of sterilization, since alternative methods such as autoclaving may deform the printed parts. we recommend that 3d printing experts communicate with their local hospital supply chain and potentially with national strategic stockpile holders. a centralized strategic local response to this crisis requires open forms of organized communication. in the united states and canada, local and state/province supply chain experts should relay best information of what is in stock, in transit, or on backorder. medical devices are highly regulated for safety. while dedicated people are responding in unprecedented ways, the 3d printing community must work in parallel to ensure that emergency parts are safe, or at a minimum safer than the alternative of not using them during a pandemic. even with the urgency of the growing covid-19 crisis, standard safety and quality measures of 3d printing labs should continue to be followed. for larger academic medical centers that have partnerships between university-based 3d printing resources and hospitals, this is often already in place; however, appropriate safety protocols should always be reviewed. safe implementation of unregulated parts is essential, and risk/benefit ratios can change very rapidly as medical supplies become unavailable. companies and regulatory bodies are strongly urged to work with the 3d printing community rapidly and efficiently. for hospital systems using internal 3d printing provided by medical or research/biomedical engineering personnel only, there is a concern for liability with 3d printing materials without safety and quality measures in place and these systems should address this concern immediately if not done already. intellectual property remains a concern, particularly for potentially reverse-engineering medical parts that cannot be purchased in a timely fashion during a pandemic. given the gravity of the situation at the time of writing, it is hoped that regulators, legal experts, and policy makers can rapidly come to agreements or allowances to save human lives using the goodwill of established and needed academic-industry partnerships. the concept of 3d printing in medicine started with the goal of improving patient education, diagnosis, and treatment [19] . we hope that this pandemic will inspire global creativity, learning and innovation through collaborative interactions of health professionals and engineers. we hope that 3d printing will be a force for a positive impact on morbidity and mortality in these trying times. going forward, the 3d printable medical model resources described here will likely be expanded in numerous centralized model repositories with new creative open source models, descriptions of intended use, assembly instructions, and target material/printer descriptions. we hope that the readers of 3d printing in medicine will find this discussion useful in addressing the covid-19 challenge and making a positive impact in patients' lives using this transformative technology. covid-19) pandemic planning and provision of ecmo services for severe ards during the covid-19 pandemic and other outbreaks of emerging infectious diseases acute oxygen therapy italian hospital saves covid-19 patients lives by 3d printing valves for reanimation devices respirator-free reanimation venturi's valve (rev. 4) wasp shares open source processes for production of personalized ppe masks and helmets makers guide prusa protective face shield -rc2 guideline for disinfection and sterilization in healthcare facilities cleaning reusable respirators and powered air purifying respirator assemblies stereolithographic (sl) biomodelling in craniofacial surgery publisher's note springer nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations authors' contributions rt, fjr, and lc wrote the manuscript. all authors provided text contributions to the manuscript. jmm contributed fig. 1 . lc generated figs. 2, 3, 4, 5, 6 and 8. nw contributed to fig. 3 . the authors read and approved the final manuscript. the authors declare that they have no competing interests. key: cord-298793-9vq3bogn authors: bunyan, d.; ritchie, l.; jenkins, d.; coia, j. e. title: respiratory and facial protection: a critical review of recent literature date: 2013-11-30 journal: journal of hospital infection doi: 10.1016/j.jhin.2013.07.011 sha: doc_id: 298793 cord_uid: 9vq3bogn summary infectious micro-organisms may be transmitted by a variety of routes. this is dependent on the particular pathogen and includes bloodborne, droplet, airborne, and contact transmission. some micro-organisms are spread by more than one route. respiratory and facial protection is required for those organisms which are usually transmitted via the droplet and/or airborne routes or when airborne particles have been created during ‘aerosol-generating procedures’. this article presents a critical review of the recently published literature in this area that was undertaken by health protection scotland and the healthcare infection society and which informed the development of guidance on the use of respiratory and facial protection equipment by healthcare workers. infection is caused by a range of micro-organisms including bacteria, viruses and fungi. the route of transmission is dependent on the particular pathogen and the range covers bloodborne, droplet, airborne and contact (direct and indirect) transmission. droplet transmission is generally accepted as the transfer of large particle droplets (>5 mm) from an infected respiratory tract over a short distance (<1 m). 1e4 airborne transmission refers to small particles (5 mm) which can spread over greater distances and can result in infection without close contact with the source. some micro-organisms are spread by more than one route. those that require the use of respiratory and facial protection are usually transmitted via the droplet and/or airborne route by breathing, coughing, sneezing, talking, laughing (particularly if the individual is suffering from respiratory symptoms), or when airborne particles have been artificially created, such as during 'aerosol-generating procedures'. 2, 4 healthcare procedures which generate aerosols include bronchoscopy, respiratory/airway suctioning, and intubation, and there is some evidence of a hierarchy of risk within these categories. 2,4e10 clearance of aerosols is dependent on ventilation. the greater the number of air changes per hour the faster any aerosols will be diluted, with a single air change removing 63% of particles and each subsequent air change removing a further 63%. it can be estimated therefore that five air changes reduce contamination to <1% of its former level, assuming dispersion has ceased. due to their ability to access the respiratory tracts of individuals exposed without necessarily having close contact with the source, the use of respiratory and facial protection (as well as other control measures) by healthcare workers may be employed to attempt to reduce the risk of infection transmission. 2 filtering of inhaled air to protect against influenza has often been regarded as a self-evident tenet of infection prevention philosophy. the 2009 h1n1 influenza pandemic was a significant spur to research in the field of influenza transmission and infection prevention; however, the evidence is still limited. 11 although it is certain that influenza is transmitted from infected to susceptible people through contaminated exhaled air, the relative importance of droplet and aerosol spread is still debated. a review by tellier presents evidence to support the role of aerosols in influenza transmission, at least over short distances. 12 if true, an important consequence of this may be the need for effective respiratory protection devices to provide defence against aerosols, not just droplets. in this case, surgical masks are not sufficient since they can only offer protection against droplets. instead, aerosol-filtering respirators are necessary. however, respiratory protection alone may not be sufficient. 11 a study looking at the ability of facemasks alone, versus facemasks and eye protection combined, to prevent infection from aerosols of live attenuated influenza virus, concluded that trans-ocular transmission was a sufficient and effective route of infection and that eye protection is a necessary adjunct to respiratory protection. 13 although this observation is significant, it must be remembered that direct splash or splatter contamination, rather than exposure to smaller and lighter respirable particles, remains a primary consideration in the assessment of the requirement for eye protection as a component of respiratory and facial protection. there is little good quality evidence to support surgical masks as an effective respiratory infection protection measure, even though they have been used for this purpose since the flu pandemic of 1919. belkin gives a history of surgical masks from this date to recent years and details us food and drug administration (fda) standards for surgical masks. 14 he points out that these standards are meant to support the use of masks for their original intended purpose e prevention of surgical infections e not to protect the wearer from respiratory infection. the rationale for the use of surgical face masks is twofold: to protect the wearer from sources of infection, e.g. splashing or spraying of blood, and to protect others from the wearer as a source of infection. 15, 16 it has also been recommended that a surgical face mask with attached face shield or a surgical facemask and goggles should be used for the protection of the wearer during aerosol-generating procedures in patients who are not suspected of being infected with an agent for which respiratory protection is otherwise recommended. 2 the use of surgical masks as part of the transmission based precautions (tbps) is designed to protect healthcare workers from exposure to potentially infective respiratory droplets. otherwise, mucosal surfaces of the nose and mouth are exposed, providing an easy route of entry to the body for pathogenic micro-organisms. 2 no standard definition of a surgical facemask was identified in the literature. there appears to be a wide variation in design and quality of masks in use. in terms of design, it is recommended that masks should fully cover the nose and mouth of the wearer. 17e19 medical devices designed to protect the wearer from airborne infectious aerosols transmitted directly from the patient or when artificially created such as during aerosolgenerating procedures (e.g. bronchoscopy) are termed respirators. 2, 4, 6, 7 many different respirators are available including half-face (mouth and nose both covered) and full-face (eyes are covered in addition to mouth and nose) respirators and they vary in their nominal ability to resist penetration by aerosols. the respirators most frequently used in healthcare settings are filtering face piece (ffp) respirators. inhaled air is drawn through a split polypropylene fibre filter enhanced with a static electric charge to increase their filtering capabilities. there are different grades of ffp respirator distinguished by labels such as ffp2 (uk designation, equivalent to north american n95 respirators) and ffp3 (n99). healthcare workers in the uk are required to wear a respirator complying with the european standard en149:2001 ffp3. 20e22 however, there is a dearth of studies focusing on the use of the ffp3 respirator, the majority being centred on the n95 respirator. although vaguely comparable, due to the n95 having a lower particulate efficacy rating, it would be helpful (especially for healthcare workers in the uk) for researchers to use ffp3 respirators in future studies. powered air-purifying respirators (paprs) use a power source to drive ambient air through a high-efficiency particulate air (hepa) filter prior to inhalation by the wearer, increasing the filtration performance over ffp respirators. however, papr devices are expensive, cumbersome, noisy and require the wearer to be specially trained in their use. a summary of the properties of masks and respirators, including paprs, is given by tompkins and kerchberger. 23 ultimately the effectiveness of both surgical masks and respirators is liable to be associated with their consistent and correct usage. 11 while the preceding arguments may suggest it is reasonable to assume that respirators should give greater protection than surgical masks against influenza infection, there are only two recent studies that test this assumption. neither demonstrated the superiority of n95 respirators over surgical masks. loeb et al. looked at rates of influenza infection in nurses in ontario, canada, who were randomized to wear either n95 respirators or surgical masks when providing care to patients with febrile respiratory illnesses during the 2008e2009 influenza season. 24 there was no significant difference in influenza infection rates between the two groups e both were close to 23%. similarly, macintyre et al. compared n95 respirators to surgical masks for their ability to protect nurses in beijing, china, against respiratory viral infections. 25 in contrast to the loeb study, subjects in the macintyre et al. trial were required to wear their respiratory protection throughout their shifts for four weeks. the results of this study were more suggestive that n95 respirators provided protection against respiratory viral infections, achieving significance for the group of illnesses broadly classed as clinical respiratory illness, but failing to demonstrate significant protection against influenza infection. while neither study included a formal 'no-masks' group, because of ethical concerns, macintyre et al. compared their subjects to a convenience no-masks group of nurses working in hospitals where mask use was not routine; they concluded that rates of respiratory infection were higher in this no-mask group compared with either the mask or respirator study arms. the report by loeb et al. drew a number of comments and criticisms including questions relating to variations in the filtering efficiencies of different makes of respirators and masks, training in n95 respirator use, poor compliance with respirator use, problems in ensuring a proper respirator fit, and infection with influenza in settings outside the workplace. 26e28 the fitting of n95 respirators has been the subject of many publications. the effective functioning of n95 respirators requires a seal between the mask and the face of the wearer. variation in face size and shape and different respirator designs mean that a proper fit is only possible in a minority of healthcare workers for any particular mask. winter et al. reported that, for any one of three widely used respirators, a satisfactory fit could be achieved by fewer than half of the healthcare workers tested, and for 28% of the participants none of the masks gave a satisfactory fit. 29 fit-testing is a laborious task, taking around 30 min to do properly and comprises qualitative fit-testing (testing whether the respirator-wearing healthcare worker can taste an intensely bitter or sweet substance sprayed into the ambient air around the outside of the mask) or quantitative fit testing (measuring the ratio of particles in the air inside and outside the breathing zone when wearing the respirator). attempts have been made to circumvent the requirement for fit testing, and it has been suggested that self-testing for a seal by the respirator wearer (see http://youtu.be/pgxiuyaoed8a for a video demonstration) is a sufficient substitute for fit-testing. however, self-checking for a seal has been demonstrated to be a highly unreliable technique in two separate studies so that full fit-testing remains a necessary preliminary requirement before respirators can be used in the healthcare setting. 30, 31 operationally, this presents significant challenges to organizations with many healthcare workers who require fit-testing. chakladar et al. pointed out that, in addition to the routine need for repeat testing over time to ensure that changes in weight or facial hair have not compromised a good fit, movements of healthcare workers between organizations using different makes of respirators would necessitate additional repeat fittesting. 32 fit-testing is likely to remain problematic to healthcare organizations for the foreseeable future. in addition to the requirement for fit-testing, 'fit-checking' is also required each time the respirator is donned to ensure there are no air leaks. 33 finding a respirator that fits a healthcare worker is not the only challenge. many healthcare workers find that respirators are uncomfortably hot and interfere with breathing and communication. 34 female healthcare workers were found to be more likely to complain than males. 35 however, objective studies of the impact of respirators on performance and communication show few significant effects, although hearing clarity was impaired in users of paprs. 36e38 physiological measurements during simulations of clinical workloads in subjects wearing n95 respirators recorded some deviation from normal values in transcutaneously measured carbon dioxide levels, possibly linked to the measured increases and decreases in respirator dead space of carbon dioxide and oxygen levels respectively. 39 the possible consequences of these changes are unknown, although probably clinically insignificant. an additional operational challenge is ensuring sufficient stock of respirators. while surgical masks are used in large numbers in surgical procedures outside flu outbreak seasons, n95 respirators have very few indications other than respiratory protection against influenza and tuberculosis. consequently, there is an element of feast or famine in their use. outside a flu outbreak, the need for respirators is small. during an outbreak, the numbers of respirators used may soar. as an illustration, during the severe acute respiratory syndrome (sars) outbreak in 2003, 18,000 n95 respirators were used in one toronto hospital alone every day. manufacturers are unable to ramp up respirator production quickly enough to meet such sudden demand and so a number of countries have built up national stockpiles of respirators. the possibility that these may not be used for several years has prompted investigations of performance after prolonged storage. happily, it appears that filtration performance is not significantly degraded by storage of up to 10 years in warehouse conditions, although this general conclusion may not be true for all makes of respirators or for attachments such as face straps. 40 a few reports have focused on putting the mask on the infected patient, rather than a healthcare worker. this copies the common practice of placing masks on patients with respiratory tuberculosis when they need to leave their isolation room. diaz and smaldone developed a bench model to explore the relative importance of dilution, deflection and filtration of infectious particles by respiratory protection when worn either by healthcare workers or patients. they concluded that deflection of exhaled particles by a mask placed over the nose and mouth of a patient, coupled with sufficient air exchanges (around six per hour) was an effective protective mechanism, providing greater protection to healthcare workers than wearing masks themselves. 41 clinical support for this approach was provided by johnson et al., who investigated how surgical masks and n95 respirators, worn by patients with confirmed influenza, would prevent the generation of infectious airborne particles. surgical masks and n95 respirators appeared to be equally and highly effective in filtering out influenza-contaminated particles when worn by infected patients. 42 this small study did not investigate whether masks or respirators worn by patients reduced the numbers of cross-infection events in a real clinical setting, which would be the decisive test for this approach. the use of a mask by visitors is a contentious issue and should be decided by the level of interaction between them and the patient, i.e. during contact with a patient with known or suspected infection with a micro-organism spread wholly or partly by the droplet route while the patient is considered infectious. 2 finally, the possibility that removal and disposal of used, potentially contaminated, respirators may be an infection risk was addressed in a pair of papers looking at particle release from respirators during removal and when dropped from height during disposal. taking off a mask causes it to be temporally stressed but these tensions do not appear to cause significant particle release from respirators, whereas dropping used respirators into a bin seems to release only very small numbers of particles. 43, 44 however, it is important that respirators are taken off using a procedure to avoid self-contamination and disposed of appropriately. 2, 33 conclusion the lack of clear superiority of respirators over facemasks in the studies of loeb et al. and macintyre et al. may result from poor respirator face seals, poor compliance due to discomfort, lack of recognition of infectious patients and consequent inappropriate non-use of respirators, infection arising from infectious co-workers, trans-ocular infection despite appropriate respirator use but no eye protection, or infection from sources outside the healthcare setting. 24, 25 regardless of the reason for failure, the high rate of infection in both of the groups in the loeb study is impressive and reinforces the need to consider how protection can be strengthened. in relation to aerosol-generating procedures the results of a recent review concluded that, although there are a number of these procedures listed under this heading, few have sufficient evidence to confirm they actually do produce aerosols e therefore further research in this area is warranted. 4 the view that cross-infection may be reduced by placing masks on potentially infectious patients, supported by bench and clinical studies, opens up an additional approach to protection. the demonstration of trans-ocular infection by aerosols needs further investigation and suggests that eye protection may be required as a component of respiratory and facial protection, not only to mitigate risks associated with direct splash or splatter contamination, but also to prevent aerosol exposure. finally, as pointed out by srinivasan and perl, and also by a recent department of health scientific review, the use of masks and respirators should be considered as the last line of defence in the hierarchy of infection prevention measures. 11, 45 these include vaccination (when available), hand hygiene (always), environmental measures including sufficient ambient ventilation, the provision of single occupancy rooms, and administrative practices that emphasize early recognition of infectious patients and their removal from others. aerobiology and its role in the transmission of infectious diseases guideline for isolation precautions: preventing transmission of infectious agents in healthcare settings 2007. atlanta: centres for disease control and prevention exposure to influenza virus aerosols during routine patient care a review of the risks and disease transmission associated with aerosol generating medical procedures epic2: national evidencebased guidelines for preventing healthcare-associated infections in nhs hospitals in england infection control in mass respiratory failure: preparing to respond to h1n1 exhaled air and aerosolized droplet dispersion during application of a jet nebulizer physical interventions to interrupt or reduce the spread of respiratory viruses: a cochrane review infection control strategies for specific procedures in health-care facilities e epidemic-prone and pandemic-prone acute respiratory diseases world health organization. who policy on tb infection control in health-care facilities, congregate settings and households pandemic influenza preparedness team. the use of facemasks and respirators in an influenza pandemic e scientific evidence base review. london: department of health aerosol transmission of influenza a virus: a review of new studies transocular entry of seasonal influenza-attenuated virus aerosols and the efficacy of n95 respirators, surgical masks, and eye protection in humans the surgical mask has its first performance standard e a century after it was introduced disposable surgical face masks for preventing surgical wound infection in clean surgery do anaesthetists need to wear surgical masks in the operating theatre? a literature review with evidence-based recommendations aorn recommended practices committee. recommended practices for surgical attire sacred rituals in the operating theatre behaviours and rituals in the operating theatre. a report from the hospital infection society working party on infection control in operating theatres biological agents: managing the risks in laboratories and healthcare premises. london: health and safety executive respiratory protective equipment at work: a practical guide filtering face piece (ffp3) masks. london: hse special article: personal protective equipment for care of pandemic influenza patients: a training workshop for the powered air purifying respirator surgical mask vs n95 respirator for preventing influenza among health care workers: a randomized trial a cluster randomized clinical trial comparing fit-tested and non-fit-tested n95 respirators to medical masks to prevent respiratory virus infection in health care workers surgical masks vs n95 respirators for preventing influenza surgical masks vs n95 respirators for preventing influenza surgical masks vs n95 respirators for preventing influenza particulate face masks for protection against airborne pathogens e one size does not fit all: an observational study health care workers and respiratory protection: is the user seal check a surrogate for respirator fit-testing? respiratory protection by respirators: the predictive value of user seal check for the fit determination in healthcare settings respirator fit-testing e will we pass the test? department of health. respirator fit testing leaflet and posters. london: doh health care workers' views about respirator use and features that should be included in the next generation of respirators respirator tolerance in health care workers diminished speech intelligibility associated with certain types of respirators worn by healthcare workers does wearing a surgical facemask or n95-respirator impair radio communication? physiological impact of the n95 filtering facepiece respirator on healthcare workers evaluation of the filtration performance of 21 n95 filtering face piece respirators after prolonged storage quantifying exposure risk: surgical masks and respirators a quantitative assessment of the efficacy of surgical and n95 masks to filter influenza virus in patients with acute influenza infection particle release from respirators, part ii: determination of the effect of tension applied in simulation of removal particle release from respirators, part i: determination of the effect of particle size, drop height, and load respiratory protection against influenza none declared. none. key: cord-326519-1r3jdffu authors: orlova, galina; morris, jeremy title: city archipelago: mapping (post)lockdown moscow through its heterogeneities date: 2020-07-11 journal: city soc (wash) doi: 10.1111/ciso.12331 sha: doc_id: 326519 cord_uid: 1r3jdffu nan online, people responded to the "fall of self-isolation" sarcastically, with an untranslatable pun on the words 'get well' (after the coronavirus) and 'amend' (the russian constitution): ("strana poshla na popravki"). public health concerns were replaced by a grim focus on the political regime's diseased mutation. in fact, moscow's hybrid practices of biopolitical care -the domestication of "the great imprisonment", with biosecurity testing, buggy digital technologies augmented by direct police control, and interventions into urban rationalities in the spirit of soviet nonconformist art -were abruptly curtailed by an autocrat's whim for his plebecite. epidemiologists and political experts agreed that the end of self-isolation in moscow was due to vladimir putin's desire to push ahead a national vote on july 1. the willed suspension of the pandemic in moscow provides a moment for reflection on the (dis)appearing city in quarantine. jeremy writes from afar; galina from close-up, from an apartment in the "quiet center" of moscow, which has shrunk for an inhabitant in lockdown to an island-quarter. covid-19 is an urban disease. in china, wuhan put on the crown, in the usa -new york, in spain -barcelona, then in russia, with its internal colonization and centripetal geography, predictably it was moscow. in a metropolis where around 10% of the population lives, 40% of russians with a diagnosis were infected at the end point of self-isolation. whereas people arriving in the capital from at-risk countries faced 14-day quarantine, in the russian regions those who arrived from moscow were put in isolation. to avoid an official 'state of emergency' which would have meant taking on a massive financial burden, city hall adopted various heuristics to manage quarantine. from march 5, the moscow had a high-alert mode, from the 26 th -self-isolation for those 65+, from the 30 th -self-isolation for all. the delegation of responsibility for their own health and well-being to citizens, after recent restrictions on freedoms, looked neoliberal. at the same time, the scope of quarantine education addressed to ignorant citizens and belief in its effectiveness, suggested the return of soviet sanitary propaganda (shok, beliakova, 2020) . in conditions of lockdown uncertainty, the boundaries of self-isolation were delineated by rituals of taking out garbage, buying food and medicine, dog walking. from april 1, fines of 4,000-5,000 rubles were imposed for each violation. on april 15, quarantine met the control society with digital codes for trips around the city. since may 12, wearing masks and gloves became mandatory in stores. minister asked the moscow mayor "organizationally and methodically" to help colleagues "on the ground", sobyanin became the face of the "virus federalism" and the capital's protocol "counteracting the spread of coronavirus infection" became a model to follow. while the self-isolation regime is gone, the "glove-mask system" remains. entering public transport or shops without ppe is prohibited. disposable masks -medical blue, three-layeredare found far beyond pharmacies: at newspaper stands, at the ice cream kiosks, in cheap and expensive grocery chains. at the reopened farmfoods store, half-empty due to supply disruptions, masks are at a discount. in may, they cost from 29 to 70 rubles, in march-april -up to an extraorbitant 150 and you could buy them only on the internet from resellers, thirty-times more expensive than in 2019. prices began to rise in february. at the peak, the government tried to mandate them, but immediately abandoned this measure. the rhytym of the pandemic in moscow was not only the appearance or absence of masks, but their price in(de)flation. in the russia that imported the bulk of masks from china before covid-19 there were three domestic manufacturers. city hall not only took ownership of the largest factory but removed its facilities from the city of vladimir to the capital, turning the pandemic into a "moscow state business". two thirds of masks from the moscow government (about 4 million items a week) were sold at cost to hospitals and communal services, 500,000 -for a "standardised price" of 30 rubles in the metro. the rest were put into a city administration reserve. compared to the free distribution of mask not only in the paris metro, but on buses in russia's far east, moscow's choices provoked discussion of the political economy of ppe. vladimirites were disgusted by the capital's betrayal leaving them not only without protection, but one profitable business less. their objections to internal colonialism were tempered with racist suggestions that the masks from moscow -now produced by "immigrants from disadvantaged countries of the near abroad" -were now "less hygienic". muscovites discussed the superprofit extracted by city hall, and supposed that "since they bought the plant, the mask-regime will never end." stuck between epidemiological citizenship and city-state paternalism, they claimed that the government had no moral right to demand wearing masks without free distribution. citizens made a hopeless diagnosis -"it's all capitalism and they don't give a shit" -and continued to buy masks. the case reveals the complex nature of state-capital conjunctions in the russian capital. appropriating profitable ppe businesses, strategically significant in an epidemic, city hall enters the order of state capitalism. obliging citizens to wear masks and offering them at commercial prices, they interpret civic responsibility in a neoliberal mode as a personal transaction according to the logic of capitalist realism that anathemizes any alternative to marketised relations (fisher 2009 ). nonetheless the virus' acceleration of neoliberalism does not completely destroy the legacy of the soviet social state, instead weakening and transforming it beyond recognition. by sending masks to hospitals at cost price, moscow combines the logic of minimal profitability and sluggish paternalism. opting to create a reserve fund instead of free distribution of masks, it reproduces a pattern of deformed care without expenditure, developed by the federal government via the russian reserve fund. state capital accumulation has a perverse obsession with curtailing the circulation -of money, of civic potential, -we call this the political economy of "the untouchable reserve". after the virus transformed the city into a host of hostile surfaces, the sanitary service enlightened muscovites that the infection "can stay in the air for 3 hours, on copper -for 4 hours, up to 24 hours on pulp and paper surfaces (documents, envelopes, folders), for 3-4 days on plastic and metal." the developing corona-market offers a "cold fog" method of disinfection from 8 roubles per m 2 . an invitation to the wake of a neighbour dead from covid, now includes: "everything is disinfected." public spaces -sidewalks, underpasses, entry-ways -are treated at city expense. the deputy mayor first earmarked 3,500 units of tractor-street sprayers, deploys 4,500. the air hangs with a bleach smell from the long-forgotten soviet sanitary aromascape while the yellow sanitisers in the metro whiff of the society of consumption and bananas. muscovites happily use them and discuss whether the big disinfection is comparable to urban beautification programs famous for exorbitant expenses and corruption. and if there isn't much point in treating open surfaces, as epidemiologists say, should this be recognized as an urban antiviral ritual? our entrance-way, which according sanitary doctors remains the most "forgotten place in terms of anti-epidemic measures", is disinfected twice daily. bumping into disinfectors in chemical protection suits with spray guns and getting coated by a dose, you realise the danger, and no longer go out without a mask. someone repeatedly adds in pencil: "unsatisfactory" to the assessment in the disinfection schedule posted by the elevator. the repairman -tired, in a cotton mask slipping down -is also unhappy: the chemicals have damaged electrical contacts, and now the elevator serves only four floors out of twelve. this metonymizes the city in quarantine as an assemblage of relative safety, partial functionality, attempts to reprogram and restore lost connectivity. maintaining moscow's reputation as a 'smart city', city hall placed its bets on the rapid development of digital control over self-isolation. from april any non-hospitalized infected were obliged to stay at home and install a special mobile app -social monitoring, developed by the city it department. from april 15, muscovites needed sixteen-digit qr codes to make daily work trips, single emergency trips, and twice-weekly trips for personal and private needs. police, taxi-drivers and transit workers mobilized to check codes using the transit department's moscow assistant app. regimented timetables of walks were dictated via infographics interfaces. drones and quadcopters for tracking social distancing in re-opened restaurants were moscow's moment to jump the shark. jung won sonn and colleagues, analyzing the effective use of technology to reduce the risks of a pandemic in south korea with smart city technologies, conclude that covid-19 is the first epidemic in history for which humanity living in cities has come up with a ready-made response system. aggregating mobile operator data, geolocations of bank transactions and transport cards allows the precise contact tracing, avoiding major quarantine. the researchers regret that countries with developed digital infrastructure -with the exception of south korea and taiwanhave not made use of this advantage. (sonn et al. 2020) . russia, where during crisis the development of a new platform and apps was preferred, entailing large upfront costs, is a special case. while yandex -russia's google and the co-owner of popular taxi, delivery and mapping apps, -published a "self-isolation index" using its own digital infrastructure and aggregating big data, city hall chose to develop apps from scratch. work requiring months was implemented in weeks with many bugs and inefficient decisions. lacking auto-verification, qr codes turned moscow assistants into nurses for an infirm technology. massive queues formed at metro entrances as policemen were forced to manually input codes to their devices. technical faults were accompanied by social de(trans)formations, compensatory improvisations, and abuses. when moscow assistant could not cope with the flood of requests, qr encounters simulated governing. the cancelling of drivers' codes without explanation led to the use of "service position" and informal connections to obtain permissions. ordinary muscovites with covid-19 paid for geolocation failures, non-stop selfie requirements, multiple disconnections of the social monitoring, developed from fragments of code written in ten days for a pilot project to monitor the transport of domestic waste. heavy fines, the denial of technical errors by city hall forced the victims of smart lockdown to unite in the fb-community fined for getting sick and to complain about the app in court and to google play. techno-political failures of moscow lockdown are full of heterogeneities. repressive social monitoring is the first manifestation of a biosecurity regime replacing biopolitics. while biopolitics featured authorities' concern with the life of population, biosecurity is built on the responsibility -including legal -of citizens for their health (agamben 2020) . for muscovites, fined for getting sick, buggy mobile apps became the real punishment. the incoherence of urban mobility monitoring destroyed the technological continuity of the society of control (deleuze 1992 ). to check a qr-code through moscow assistant, you need a policeman or a taxi driver in person with a mobile citizen. taxi drivers tell of the discomfort that arose performing these police duties. the mayor's office sees voluntary assistance and civic duty in them, but just in case, offers numerous sanctions for those who refuse to help. in a country where civil society is supposedly weak, the prosthetics of digital technologies during lockdown risk not so much strengthening the police state but accelerating the emergence of a "police society". a booklet from ritual, the moscow funeral service and operator of moscow cemeteries, dropped into our postboxes on the eve of self-isolation for 65+. the use by a commercial firm of the state services' design suggests a newly cozy relationship between the traditionally shady funeral business and russian stateness. last summer, this convergence took the form of a corruption scandal, linked to the high-profile case of journalist ivan golunov, framed for his investigation of murky dealings between moscow undertakers and state security organs. this spring ritual prepared inhabitants for death and loss, warned against contacts with "black agents", informed about prices and social subsidies, also offering people something that in the extreme circumstances of pandemic they expected but did not receive from the state -care. care, which remains for russians one of the most important regimes of affective expectations in political communication with authorities, masks hierarchies and injustice (bogdanova 2005) . care certificates from ritual guarantee the owners, if they died within a year of purchase, burial at the operator's expense. this offer had the side effect of interpellating tenants as potential victims of the virus. yandex informed muscovites about the preparedness of ritual, that "will come in handy", for the pandemic: protective equipment and coffins in ready supply. the ministry of health published temporary recommendations -later rescinded -including a prescription to bury infected bodies in sealed coffins. who and russian virologists confirmed that the virus is not transmitted from the dead to the living. funeral services are not under the authority of the health ministry. nonetheless, the protocol was entrenched: coronavirus victims are sealed in bags, and not released to relatives. ritual posted a "viral" instagram burial video: a hazmatsuited funeral team, disinfectant poured into the grave, a clutch of relatives frozen in the distance, the pit fill with fir branches as a natural disinfectant and only completed. the union of ritual workers has spoken out against the use of garbage bags as destructive to the social order and turns funerals from care into disposal. refusing large-scale support for population and business, the authorities compiled lists for selective state aid. the presidential one featured a child allowance. moscow -supported the newly unemployed. the government made two lists -for 642 system-critical firms (including bookmakers!) along with a dozen industries extremely vulnerable to the effects of the epidemic. the chair of the chamber of commerce proposed including outdoor ads, which would lose up to 70% of revenue in deserted cities, in the second list. simultaneously, he emphasized the critical role of billboards in informing people about virus protection, the wwii anniversary, and the upcoming plebiscite. was this transition from the affected to having critical significance a transition from commercial advertising to propaganda? did this discursive merging tell us more about saving the industry at the expense of state orders? even in the small section of my selfisolation route, billboard changes perform the symbolic dynamics of quarantine. when le village magazine asked sergeant kurakin, who was checking qr codes at the metro, why people disobey quarantine -the answer was 'to work'. closure and opening of quarantine both draw a labor division. mobilized doctors, taxi drivers, grocery and utility workers, couriers, bus drivers -these high-risk occupations, deemed essential, were never locked down. 'partisan' hairdressers worked clandestinely. switching to 'distance working', people were faced with the hardships of endless digital labor and its invasion of privacy, small and medium business -with the need to pay salaries in the absence of revenue and state support. moscow closed more comprehensively than other russian cities. reopening, formally based on the topological 'safety' ranking of occupations, was multi-step. 12 may -the same time as mandating obligatory masks in shops -construction sites and industry restarted. may 26 government service centres (by appointment) and car-sharing services (partially) returned. other services were divided into three stages in june, visualized in infographics: first hairdressers and cemeteries, then cafã© verandas and dental clinics, and finally, kindergartens, fitness clubs and restaurants. the city reopening was asynchronous and incomplete, in turn affecting the political and economic in complex and unpredictable ways. but we learn nothing from them about changes in the life of the city or its inhabitants. to think of a large city in quarantine as archipelago is to problematize the qualitative changes in urban life during self-isolation, mapping the diffusion of sociality and following heterogeneities of (non)actualized presence. the implosion of urban imagination, the narrowing of vision and atrophied habitus -all of what creates so much discomfort and inconvenience for city-dwellerscan open new analytical perspectives in how to deal with impoverished forms of dwelling and not be afraid of attending to its fragmentation. the playground taped off. footpaths along which friends walk their puppy. i wave to them from my balcony. rubbish containers next to the dovecote "love and doves" that emptied during quarantine. 2. wine island, where the store consultant week to week talks about wine from more and more distance. 3. the island of a closed house museum of pushkin's uncle and food, delivered from may with no charge by taxi firm. 4. island with more cheap food, water and hardcore disinfection. here i bought my second pack of masks (the first were from the internet at a crazy price). here my friends live. all springtime we would have drinks and read poetry on fridays in whatsapp.5. the far post-office island, 600 meters from home. i went there a couple of times at the end of selfisolation. 6. the far bank island at a distance of 1km from home. 7. the phantom island of work. humanities campus of "vyshka", where i have not been since the middle of march, working at a distance. colleagues in fb don't believe in its existence. i see the building every day from my window and do not believe either. 8. billboards from our photos. 9. the island-building of ailments, visible from my window, where all april ambulances -the dominant vehicle in the empty city -came time after time. 10. moscow city, a group of skyscrapers on the horizon, visible with unprecedented sharpness. usually -and now once again -they are smoggy. image by galina orlova. sovetskaya traditsiya pravovoj zashhity, ili v ozhidanii zaboty [the soviet tradition of legal protection or awaiting care postscript on the societies of control capitalist realism: is there no alternative? kartografirovanie ostryx socialnyx problem trebuet ostorozhnosti [mapping acute social issues requires caution how soviet legacies shape russia's response to the pandemic: ethical consequences of a culture of non-disclosure smart city technologies for pandemic control without lockdown at the end of march, the dismantling of outdoor ads from the frozen centre of moscow gave way to mobilization. from billboards, placed every 15-20 meters, well-known moscow doctors urged muscovites to stay home, wear masks and not touch their faces. after april, this template was adapted to enhance affective solidarity and the formation of quarantine communities. doctors are no longer given voice, they are thanked. and young people are hailed as volunteers. closer to the garden ring sanitary enlightenment is interspersed with posters for victory day. in early summer, commercial advertising has returned as a (post)quarantine hybrid -mcdonald's with both hands voting for hand washing. the epidemiological safety and the upcoming voting in this austere carnival of signs do not leave room for bigmacs yet.the moscow government justified priority reopening of industry as 'least dangerous' because of the absence of direct contact between producers and consumers. however, no one hid that the resumption of construction work -masked, with a reduction in shift and brigade work -was due to the shared economic interest of lobbying developers and city hall, and the problems of labour migrants. according to mobile operator data, up to 2.5 million people from russian regions left moscow during quarantine. but citizens from the cis countries, mainly engaged in construction, were locked up in the capital without a livelihood. moscow officials saw criminal risk in migrants without work, reifying care about them as an interface of profit and biopolitical inequalities.if the resumption of construction strengthened socio-economic marginalizations existing before quarantine, the partial opening of car sharing produced new inequalities. at the end of may, the renewed service only allowed five-day-plus leases, unaffordable to most. as for mandatory disinfection of the cabin before returning the car, this was another materialization of sharing as a "new dangerous". several years ago, 'le monde diplomatique' published an imaginary palestine map. the occupied territories were represented as the sea; the authority-controlled ones -as islands of an archipelago. numerous maps of the pandemic, regularly described in military metaphors, depict the covid-19 occupation in a different way -not framed through absent space but as more or less filling it, and pushing out of frame alternatives of resistance, coping and co-existence. from maps of pandemic moscow we can see how the concentration of the virus shifts from the prosperous centre and south-west, where the epidemic began, to the northern, eastern and southkey: cord-337372-y43prnko authors: bin‐reza, faisal; lopez chavarrias, vicente; nicoll, angus; chamberland, mary e. title: the use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence date: 2011-12-21 journal: influenza other respir viruses doi: 10.1111/j.1750-2659.2011.00307.x sha: doc_id: 337372 cord_uid: y43prnko please cite this paper as: bin‐reza et al. (2012) the use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence. influenza and other respiratory viruses 6(4), 257–267. there are limited data on the use of masks and respirators to reduce transmission of influenza. a systematic review was undertaken to help inform pandemic influenza guidance in the united kingdom. the initial review was performed in november 2009 and updated in june 2010 and january 2011. inclusion criteria included randomised controlled trials and quasi‐experimental and observational studies of humans published in english with an outcome of laboratory‐confirmed or clinically‐diagnosed influenza and other viral respiratory infections. there were 17 eligible studies. six of eight randomised controlled trials found no significant differences between control and intervention groups (masks with or without hand hygiene; n95/p2 respirators). one household trial found that mask wearing coupled with hand sanitiser use reduced secondary transmission of upper respiratory infection/influenza‐like illness/laboratory‐confirmed influenza compared with education; hand sanitiser alone resulted in no reduction. one hospital‐based trial found a lower rate of clinical respiratory illness associated with non‐fit‐tested n95 respirator use compared with medical masks. eight of nine retrospective observational studies found that mask and/or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome (sars). findings, however, may not be applicable to influenza and many studies were suboptimal. none of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection. some evidence suggests that mask use is best undertaken as part of a package of personal protection especially hand hygiene. the effectiveness of masks and respirators is likely linked to early, consistent and correct usage. personal protective equipment to help reduce transmission of influenza is generally advised according to the risk of exposure to the influenza virus and the degree of infectivity and human pathogenicity of the virus. the paucity of scientific evidence upon which to base guidance for the use of masks and respirators in healthcare and community settings has been a particularly vexing issue for policymakers. the health protection agency (hpa) undertook a scientific evidence-based review of the use of masks and respirators in an influenza pandemic to inform relevant guidance following the emergence of pandemic a (h1n1) 2009 influenza. the department of health commissioned the hpa to update the review in support of the revision of the united kingdom (uk) influenza pandemic preparedness strategy. 1 the review was published on-line at: http:// www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/ documents/digitalasset/dh_125425.pdf. a further update of the evidence base subsequently was performed in january 2011 and described herein. we generally followed the approach detailed in the university of york's systematic reviews: crd's guidance for undertaking reviews in health care. the original search of the pubmed database was conducted on 7 november 2009; subsequent updates of the pubmed database search were undertaken on 23 june 2010 and 12 january 2011. 1 the november 2009 search also included the following scientific databases: bandolier, the cochrane library database of systematic reviews, the database of abstracts of reviews of effects, the health technology assessment database, the national health service (nhs) economic evaluation database, the uk database of uncertainties about the effects of treatments, the nhs centre for reviews and dissemination and the cumulative index to nursing and allied health literature. 2 no additional publications resulted from these databases. the initial search in november 2009 had no time period restrictions. a limited effort was made to identify additional studies: reference lists of review articles were examined; the european centre for disease prevention and control's (ecdc) antimicrobial resistance and health care associated infection programme was consulted; and mec's and an's hardcopy literature files were hand-searched. we included the following types of studies listed in the hierarchical order of study design quality: randomised controlled trials (i.e. randomised cross-over trial and cluster randomised trial); quasi-experimental studies (i.e. non-randomised controlled study, before-and-after study and interrupted time series); and observational studies (cohort study and case-control study). only human studies published in english which had an abstract were included (table 1) . infection with pandemic strains, seasonal influenza a or b viruses and zoonotic viruses such as swine or avian influenza were included because mask ⁄ respirator guidance is needed for all types of influenza. studies that evaluated the effect of masks ⁄ respirators on transmission of other respiratory viruses were included as a proxy for influenza. a two-stage selection process was used to identify studies that appeared to meet the inclusion criteria. firstly, fb-r or vlc scanned and excluded papers on the basis of the 'title' for relevance; in the second and third searches, some relevant titles were excluded because they had been selected for review during a prior search. secondly, to enhance the reliability of the selection process, fb-r, vlc, mec and an independently reviewed the abstracts for the remaining papers. fb-r or vlc used a pre-designed form to perform an initial data extraction of the full article and make an initial determination regarding its eligibility. mec or an subsequently reviewed all of the papers, supplemented fb-r's and vlc's initial abstraction as necessary and re-assessed each paper for inclusion in the review. any differences were resolved by mutual agreement. mec and an assessed the quality of the eligible studies using the critical appraisal skills programme tools 3 for randomised controlled trials, case-control studies and cohort studies. the three separate database searches yielded a total of 6015 titles; five articles were identified by scanning the reference lists of review articles and three articles were from mec's hard copy collection ( figure 1 ). full papers were obtained for 76 articles; of these, 17 studies were eligible for inclusion. descriptions, findings and comments for these studies are detailed in tables 2-4. three of the randomised trials were hospital-based studies, 4-6 and five were conducted in community settings. [7] [8] [9] [10] [11] two of these studies compared n95 respirators (designed to seal tightly to the wearer's face and filter out very small particles or aerosols that may contain viruses) and surgical masks (used to block large droplets from coming into contact with the wearer's mouth or nose) amongst healthcare workers; one trial found a lower rate of clinical respiratory illness associated with the use of non-fit-tested n95 respirators compared with medical masks, 6 whilst a non-inferiority trial found that masks and respirators offered similar protection to nurses against laboratory-confirmed influenza infection. 5 a trial conducted amongst crowded, urban households found that, despite poor compliance, mask wearing coupled with hand sanitiser use, reduced secondary transmission of upper respiratory infection ⁄ influenza-like illness ⁄ laboratory-confirmed influenza compared with education; hand sanitiser alone resulted in no reduction in this aggregated outcome. 11 although the remaining five trials found no significant differences between control and intervention groups, there were some notable findings. household contacts who wore a p2 respirator (considered to have an equivalent rating to an n95 respirator) 'all' or 'most' of the time for the first 5 days were less likely to develop an influenza-like illness compared with less frequent users in one study. 9 another study found a significant reduction in laboratory-confirmed influenza amongst household contacts that began hand hygiene or hand hygiene plus a mask within 36 hours of the index case's illness. 8 a trial conducted amongst resident university students detected significant reductions in influenza-like illness during weeks 4-6 in the mask and hand hygiene group after adjusting for vaccine receipt and other potential confounders. 10 the requirements for mask ⁄ respirator wearing and subsequent compliance varied by study ( table 2) ; for example, in macintyre's study of healthcare workers in china in december 2008 through january 2009 6 'participants wore the mask or respirator on every shift for 4 consecutive weeks after being shown when to wear it', whilst nurses in canada wore a mask or respirator during the 2008 ⁄ 09 influenza season when caring for patients with febrile respiratory illness and during aerosol-generating procedures. 5 observational studies all of the observational studies evaluated mask and respirator use following the outbreaks of severe acute respiratory syndrome (sars) in 2003; [12] [13] [14] [15] [16] [17] [18] [19] [20] seven studies were conducted amongst healthcare workers and two were community-based. all but two 12,13 of the case-control studies in healthcare workers reported that wearing masks and ⁄ or respirators appeared to protect workers from acquiring sars. 14-17 a retrospective cohort study of nurses who worked in two toronto hospital intensive care units found that the relative risk of sars for nurses who consistently wore a n95 respirator was half that for nurses who consistently wore a surgical mask; however, the difference was not significant because of a small sample size. 18 none of the studies we reviewed established a conclusive relationship between mask ⁄ respirator use and protection against influenza infection. some useful clues, however, could be gleaned. subanalyses performed for one of the larger randomised controlled studies in a household setting found evidence of reduced rates of influenza-like illness if household contacts consistently wore the mask or respirator. 9 the authors of a randomised trial of mask plus alcohol-based sanitiser and mask-only group amongst u.s. university students living in residence halls noted that their study may have been better positioned to identify a protective effect because participants initiated the interventions at the beginning of the influenza season. 10 cowling's 8 finding that there was a significant reduction in the secondary attack ratio if the hand hygiene and mask plus hand hygiene interventions were begun within 36 hours of the index case lends support to this hypothesis. anticipating the paucity of studies that focused solely on influenza, we included the effect of masks ⁄ respirators on respiratory viruses other than influenza. such studies have often been used to support infection control guidance for influenza. however, the difficulties in interpreting the observational studies of sars suggest that they are of limited use for guiding policy on influenza. firstly, sars is an unusual acute viral respiratory infection with a very different epidemiology to almost all other respiratory viral infections. it is fundamentally different from human influenza: it rarely infects children, has a long incubation period, transmits little early on, mostly transmits in cannot distinguish relative contributions of hand hygiene and mask as they were combined. bin-reza et al. masks and respirators to prevent influenza ª 2011 blackwell publishing ltd healthcare settings, is not prone to extensive global spread and has only appeared once. secondly, the studies were poorly designed, had many weaknesses and so were very difficult to interpret. issues of concern include the use of a non-specific definition for exposure to a sars patient (e.g. coming within one metre of a patient), inconsistency in providing information about the comparability of cases and controls and collection of data after a lengthy period following the outbreak. several lacked microbiological confirmation of cases or controls and it would seem likely that a number of the sars cases were not cases at all. because all the cases knew they were cases, recall bias was highly likely. the single case-control study that tried to address some of these limitations did not find that inconsistent use of masks or respirators was associated with sars infection. 13 it is important to note three considerations when assessing the practical implications of the review's findings. firstly, development of evidence-based guidance about mask ⁄ respirator use is inextricably linked to what is known about how influenza is spread and specific risk factors that can affect transmissibility (e.g. host factors, pathogen factors, environmental factors and particle size). however, this is an area equally fraught with uncertainty; there are limited and conflicting evidence regarding the relative importance and frequency of direct contact, indirect contact, droplet and aerosol modes of transmission. 21, 22 historically, transmission has been thought to occur principally through respiratory droplets and masks have been used as a barrier against droplets emitted by coughing and sneezing. in the last decade, there has been increasing interest in a possible role for aerosol transmission of influenza and the advisability of filtering respirators to block such transmission. for example, studies have found that infected patients can produce aerosol particles containing influenza virus 23 and that hospital airflow patterns can influence influenza transmission via aerosols. 24 secondly, although the focus of this review has been on masks and respirators, limiting transmission of influenza in both healthcare and community settings requires a multifaceted approach, of which masks and respirators are but one component. in the healthcare setting, this 'hierarchy of controls' includes administrative controls help to reduce the introduction and spread of infection (e.g. policies to restrict entrance of ill visitors and workers, vaccination of healthcare workers); environmental ⁄ engineering controls (e.g. adequate ventilation); and lastly, use of personal protective equipment and hand hygiene. 25 in the community setting, a similarly structured approach is advised. however, during both the planning for an eventual pandemic and the subsequent public health response to the h1n1 pandemic, concern over policy and guidance related to mask ⁄ respirator use has at times seemed to overshadow almost all hcws wore n95 respirator or surgical mask in all patient settings. unadjusted univariate analysis found inconsistent use of masks or respirators not associated with higher risk of sars in any of the 3 contact settings; multivariate analysis found inconsistent use of >1 type of ppe during direct contact independent risk for sars. no serological testing of controls; reporting bias possible. nishiura ⁄ viet nam (14) period 1: time from admission of index case to occurrence of secondary cases in one hospital: 25 laboratory-confirmed sars cases compared with 90 controls (hcws and relatives of patients). period 2: during a nosocomial outbreak in the hospital with strict isolation procedures, quarantine of hcws and increased use of ppe: 4 laboratory-confirmed sars cases compared with 26 controls with only physicians and nurses in both groups. period 1: univariate analysis found masks (or 0ae3, 95%ci 0ae1-0ae7) and gowns (or 0ae2, 95%ci 0ae0-0ae8) protective; in logistic regression analyses, only masks protective (or = 0ae29, 95% ci 0ae11-0ae73) period 2: use of masks (or < 0ae1, 95% ci 0ae0-0ae3) and gowns (p = 0ae010, or and ci not calculable) associated with non-infection for doctors and nurses. possible recall bias; exposures imprecisely quantified; no serological testing of controls. nishiyama ⁄ viet nam (15) risk factors for serologicallyconfirmed sars infection assessed for 85 case and control hcws who had direct contact with sars patients. multivariate logistic regression analysis found significant risk for sars amongst hcws who never wore mask compared with those who always wore a mask (or 12ae6, 95% ci 2ae0-80ae0, p < 0ae01) possible reporting bias as interview conducted 7 months after outbreak; nature of exposures to sars not specified; community exposures not assessed. seto ⁄ china -hong kong (16) 13 sars-infected hcws with no community exposures compared with 241 hcws without clinical sars; all reported direct contact with 11 sars patients in 5 hospitals. univariate analysis found hcws who used surgical masks or n95 respirators, gowns or hand washing less likely to develop sars; logistic regression analysis found use of any mask significant (or 13, 95% ci 3-60). no serological testing of controls; reporting bias possible as interviews conducted a month after cases identified; community exposures not assessed. teleman ⁄ singapore (17) evaluated risk factors for serologically-confirmed sars amongst 36 ill case-hcws exposed to 3 highly infectious source patients and 50 well control-hcws that came within 1 m of serologically-confirmed sars patients. adjusted logistic regression analyses found that wearing n95 respirator during each patient contact (adj or 0ae1, 95% ci 0ae02-0ae86, p = 0ae04) and hand washing after patient contact (adj or 0ae07, 95% ci 0ae008-0ae66, p = 0ae02) protective. small sample size; no serological testing of the controls; limited recall of precise exposure data; no assessment of community ⁄ household exposures. masks and respirators to prevent influenza ª 2011 blackwell publishing ltd other important controls. 26 it is somewhat paradoxical that whilst continued effort and resources are needed to assess the independent effect of masks and respirators on influenza transmission, their use would always be recommended in combination with other control measures. thirdly the practical implications of policy, guidance and recommendations on mask ⁄ respirator use and other infection control measures must be considered. the only two studies that compared mask and respirators to protect healthcare workers from influenza infection essentially reached different conclusions 5, 6 illustrating the difficulties facing policymakers. 27 further, a simulation study found that strict adherence to guidance about personal protective equipment (which included masks and respirators) compromised normal ward functioning in a uk hospital setting. 28 this review had a prescribed narrow focus that permitted us to examine a relatively small number of studies. we considered employing quantitative techniques, but on analysis found the studies comprised a range of study designs, pathogens, participants, interventions and opportunities for bias and confounding would render any metaanalysis findings open to criticism. a review that included interventions other than mask ⁄ respirator use, experimental laboratory and ⁄ animal-human studies on mask ⁄ respirator efficacy, cost-effectiveness studies and the occurrence of adverse events would present a more comprehensive picture. several systematic reviews of interventions to limit the transmission of respiratory viral infections and ⁄ or specifically influenza have been undertaken. most have considered a range of interventions; 29-33 one focused specifically on respiratory protection. 34 within the boundaries established by our inclusion criteria, our search strategy captured essentially the same studies on masks and respirators that others have identified. jefferson et al derived pooled estimates of the effectiveness of wearing an n95 respirator (91%) and wearing a mask (68%) for any respiratory viral infection; 29 however, these estimates were derived from the analyses of six sars studies whose methodology was problematic. we carefully noted how well exposures in various studies were detailed and if cases and controls were laboratory-confirmed to avoid misclassification bias. we did not feel that such a heterogeneous group of studies could be combined even for sars. in conclusion, there is a limited evidence base to support the use of masks and ⁄ or respirators in healthcare or community settings. mask use is best undertaken as part of a package of personal protection, especially including hand hygiene in both home and healthcare settings. early initiation and correct and consistent wearing of masks ⁄ respirators may improve their effectiveness. however, this remains a major challenge -both in the context of a formal study and in everyday practice. continued research on the effectiveness masks ⁄ respirators use and other closely associated considerations remains an urgent priority with emphasis being on carefully designed observational studies and trials best conducted titles and abstracts identified and screened n = 5351 (1st search) n = 317 (2nd search) n = 347 (3rd search) figure 1 . diagram of search strategy results and article selection for three searches. 1 includes 3 papers that were sought for review and abstraction in the first search. 2 includes 6 papers that were sought for review and abstraction in the second search. 3 one of these papers (reference no. 6) became available on-line on 27 january 2011. 4 reasons for exclusion included an inability to distinguish the effect of mask use from other personal protective equipment or lack of quantitative data. masks and respirators to prevent influenza ª 2011 blackwell publishing ltd outside a crisis situation. 35 however, examination of the literature has highlighted that well-designed studies in this field are challenging. 27 studies need to be adequately powered to assess potentially small differences between interventions and the independent effect of mask ⁄ respirator wearing when a second intervention (e.g. hand hygiene) is employed; an appropriate control group must be identified (e.g. no use of masks ⁄ respirators). most of the studies we examined were too small to reliably detect what would be anticipated to be moderate effects. perhaps, one solution is to fund large multi-centre trials with similar protocols in different sites for multiple years to achieve sufficient power. protocols should include the collection of detailed exposure data, objective monitoring of compliance and assessment of potential confounders. it may be difficult to design studies employing a control group that does not use any protective equipment (including masks ⁄ respirators), particularly in healthcare settings, as such precautions are routinely recommended. finally, there is a striking paucity of published studies with microbiologically proven influenza infection as an outcome; inclusion of laboratory outcomes is essential in any future study of masks ⁄ respirators on transmission of influenza. uk influenza pandemic preparedness strategy 2011: strategy for consultation crd's guidance for undertaking reviews in health care use of surgical face masks to reduce the incidence of the common cold among health care workers in japan: a randomized controlled trial surgical mask vs n95 respirator for preventing influenza among health care workers: a randomized trial a cluster randomized clinical trial comparing fit-tested and non-fit-tested n95 respirators to medical masks to prevent respiratory virus infection in health care workers preliminary findings of a randomized trial of non-pharmaceutical interventions to prevent influenza transmission in households facemasks and hand hygiene to prevent influenza transmission in households: a cluster randomized trial face mask use and control of respiratory virus transmission in households mask use, hand hygiene, and seasonal influenza-like illness among young adults: a randomized intervention trial impact of non-pharmaceutical interventions on uris and influenza in crowded, urban households which preventive measures might protect health care workers from sars? sars transmission among hospital workers in hong kong rapid awareness and transmission of severe acute respiratory syndrome in hanoi french hospital, vietnam risk factors for sars infection within hospitals in hanoi, vietnam effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (sars) factors associated with transmission of severe acute respiratory syndrome among health-care workers in singapore sars among critical care nurses sars transmission, risk factors, and prevention in hong kong risk factors for sars among persons without known contact with sars patients transmission of influenza a in human beings aerosol transmission of influenza a virus: a review of new studies measurements of airborne influenza virus in aerosol particles from human coughs possible role of aerosol transmission in a hospital outbreak of influenza pandemic (h1n1) 2009 influenza -a summary of guidance for infection control in healthcare settings respiratory protection against influenza (editorial) respirators versus medical masks: evidence accumulates but the jury remains out (editorial) personal protective equipment in an influenza pandemic: a uk simulation exercise physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review physical interventions to interrupt or reduce the spread of respiratory viruses non-pharmaceutical public health interventions for pandemic influenza: an evaluation of the evidence base protecting health care workers from sars and other respiratory pathogens: a review of the infection control literature face masks to prevent transmission of influenza virus: a systematic review research findings from nonpharmaceutical intervention studies for pandemic influenza and current gaps in the research we gratefully acknowledge the librarians at the health pro mary e chamberland provided assistance to the health protection agency, u.s. centers for disease control and prevention and the world health organization in the development of infection control recommendations for pandemic influenza. angus nicoll helped develop the ecdc infection control guidance for pandemic, seasonal and avian influenza. fb-r, vlc, an and mec analysed the data. fb-r and mec were the principal writers of the manuscript with contributions from an and vlc. key: cord-295806-imuk73xa authors: ramirez-moreno, j. m.; ceberino, d.; gonzalez, a.; rebollo, b.; macias, p.; hariramani, r.; roa, a. m.; constantino, a. b. title: mask-associated de novo headache in healthcare workers during the covid-19 pandemic. date: 2020-08-11 journal: nan doi: 10.1101/2020.08.07.20167957 sha: doc_id: 295806 cord_uid: imuk73xa introduction: the pandemic caused by the new coronavirus (covid-19) has led to changes in the development of health care activities by health professionals. we analysed whether there is an association between the appearance of de novo headache according to the type of mask used, the related factors, as well as the impact of the headache on health professionals. method: cross-sectional study in a tertiary hospital in extremadura, spain. we administered an online questionnaire to healthcare workers during the period of maximum incidence of covid-19 in our setting. results: n=306, 244 women (79.7%), with an average age of 43 years (range 23-65). of the total, 129 (42.2%) were physicians, 112 (36.6%) nurses and 65 (21.2%) other health workers. 208 (79.7%) used surgical masks and 53 (20.3%) used filtering masks. of all those surveyed, 158 (51.6%) presented de novo headache. the occurrence of headache was independently associated with the use of a filtering mask, or 2.14 (ic95% 1.07-4.32), being a nurse or 2.09 (ic95% 1.18-3.72) or another health worker or 6.94 (ic95% 3.01-16.04) or having a history of asthma or 0.29 (ic95% 0.09-0.89). depending on the type of mask used there were differences in headache intensity. and the impact of headache in the subjects who used a filtering mask was worse in the all aspects evaluated. conclusions: the appearance of de novo headache is associated with the use of filtering masks and is more frequent in certain health care workers, causing a greater occupational, family, personal and social impact. in december 2019, a new coronavirus, sars-cov-2, started an outbreak in the chinese city of wuhan. in january 2020 its clinical picture was defined as a disease associated with coronavirus-2019 (covid-19) [1, 2] . this outbreak has evolved into a pandemic and as of may 24, 2020, 216 countries have been affected, 5,206,614 cases have been confirmed worldwide, and 337,736 deaths have occurred [3] . in spain, 233,037 cases have been documented and 27,940 patients have lost their lives [4] . in the region of extremadura, 3,047 cases and 506 deaths have been reported [5] . during the increase in cases of covid-19 in our environment, the national and local authorities established the mandatory use of personal protective equipment (ppe) by health professionals. this ppe consists of a protective suit, surgical gloves, protective goggles, shield and face mask. in the case of face masks, they must be highly effective, with type fpp2 (in europe), n95 (usa) and kn95 (china) recommended [6] . there are other types of masks (surgical masks or fpp1 among others), of lesser effectiveness, which are used by healthcare personnel who are not in direct contact with covid-19 [7] . the use of protective material in a strict manner is crucial, as it can reduce transmission to highly exposed populations such as healthcare workers, as well as reduce the spread of infection from healthcare workers to healthy patients. in "frontline" work, the use of masks can be very prolonged [8] . although, in general, highly effective masks are well tolerated, some problems have been reported, such as: general discomfort, decreased visual, auditory or vocal capacity; excessive heat or humidity, facial pressure, skin lesions, itching, fatigue, anxiety and claustrophobia [9] . another effect, already described in the 2003 sars epidemic, was headache, whose prevalence reached 37.3% of the health personnel studied [10] . headache associated with mask use could be related to mechanical factors, the presence of hypoxemia and hypercapnia or to the stress associated with mask use [11, 12] . our aim is to demonstrate whether there is an association between the appearance of "de novo" headache with the type of mask and its time of use, as well as the impact of this headache on health professionals. the study was conducted in the health area of a tertiary hospital, where our health system in the covid period was mandated to use ppe during contact with patients. these protective systems were mandatory among health workers, both in high-risk areas (intensive care units, isolation rooms for infected patients, emergency rooms or operating theatres), and in general medical wards, central hospital radiology and diagnostic imaging areas or outpatient clinics. this involved the use of different types of more or less tight-fitting masks, and sometimes glasses or screens. using a self-administered questionnaire addressed to health workers in our health area, we carried out a cross-sectional study during the first week of may 2020. in the previous month, the number of admissions for covid-19 was very high and attendance protocols required the use of these devices by all workers. the questionnaire collected the following information: (1) demographics (gender, age, profession, shifts); (2) medical history, including sars-cov2 infection; (3) type and pattern of mask use (surgical masks vs. self-filtering masks of particles and liquid aerosols (ffp), average number of hours of use per day) and use of other protective devices (glasses or screens); (4) frequency and characteristics of pre-existing primary headache (changes in headache frequency, attack duration and frequency, as well as drug use and response), (5) the main variable of the study was personal opinion about the presence of new headache in the period in which these protective systems were mandatory (duration of headache episode, intensity and frequency, as well as drug use and response); (6) presence of other symptoms potentially associated with the use of facial protection equipment (fatigue, sleep disorder, lack of concentration, irritability, nausea or vomiting or others); (7) we evaluated the selfperceived impact of the presence of new-onset headache using the likert scale on social, occupational, family and personal aspects; (8) we also evaluated the self-perceived impact that headache conditions have on the performance of work activities and (9) lastly, we analyzed self-perceived work stress by means of the psychosomatic problems questionnaire (ppq) [13] . the questionnaire was written after an analysis of the literature and a thorough reflection on the problem to be investigated. it included a request for voluntary collaboration, information on the reason for the survey, instructions for completing the questionnaire and consent. the average time taken to complete the questionnaire was about 20 minutes. the information collection procedure chosen was the online survey. the survey was scheduled to be conducted over five consecutive days, between 1 and 6 may 2020, with the data collected referring to the previous month. the data collected in the study respects the anonymity of the subject and there is no possibility of access to any personal information of the individual. the data analysed is restricted to the study investigators, health authorities and the clinical research ethics committee, when required, in accordance with current legislation. prior to the analysis of relationships between variables, descriptive analyses of the different areas that make up the study have been carried out. these descriptive analyses include percentage distributions of the different categories of the analysed variables and, in the case of quantitative variables, average and standard deviation. these same analyses, shown as a cross between variables by means of contingency tables or comparison of averages, have also been elaborated as a preamble to the statistical tests that have been carried out to corroborate if there is a relationship between different variables, thus showing the hypotheses to be contrasted. depending on the nature of the variable (qualitative or quantitative) and the distribution of the sample (normal, admitting parametric contrasts, or non-normal, needing non-parametric contrasts), different tests have been used. we used the chi-square test to contrast whether there is independence between two categorical variables using a contingency table when the data are not paired. for the analysis of the predictive factors with the appearance of a "de novo" headache, we used binary logistic regression methods by steps backwards, to maximize sensitivity, variables with a univariate association of p <0.200 were included as candidates in the multivariate model. to measure the relationship between the different variables in the study, statistical tests with a 95% significance level were used as an acceptance threshold for the hypotheses to be tested, of the 306 persons surveyed, 158 (51.6%) reported the appearance of a new headache during the period of study, of whom 65 (41.1%) had previously had a headache (migraine: 27 (17.1%), tension: 26 (16.5%) and others: 11 (6.9%)). there were 103 (33.7%) subjects who did not observe the appearance of new headache. a 14.7% were undecided on the answer ("i don't know") or the answer was "maybe"; these 45 subjects were eliminated from the analysis. they were also asked about the presence of other symptoms such as sleep disturbance, loss of concentration, irritability, photophobia, sonophobia, nausea or vomiting. table 1 shows the characteristics of the population according to the appearance or not of headache. during april, the month immediately prior to the survey, participants with "de novo" headache presented a median of 12 (iqr 13) days of headache, median of 4 days (iqr 3) in the week prior to the survey and the pain presented an average intensity on the visual analogue scale of 6 (sd 1.5). in 74 (47.4%) subjects the duration was from 1 to 4 hours, in 46 (29.5%) from 4 to 8 hours, in 21 (13.5%) from 8 to 12 hours and in 15 (9.6%) more than 12 hours. in subjects with previous headache the duration of episodes was significantly higher (p=0.008). the response to analgesics was good or very good in 61.4% of the cases. only 2 (1.3%) subjects had to consult the emergency department for headache, and no subject had been admitted to hospital for headache. with respect to the impact of headache in the work setting, lack of concentration on tasks was the main complaint (105 (66.5%) subjects). table 2 shows the main characteristics of "de novo" headache. in the univariant analysis, the factors associated with the appearance of "de novo" headache were: age, female sex, type of professional, use of filter mask (kn95 or ffp2), work shift, being a tobacco user, suffering from anxiety or asthma. in the multivariant analysis, the use of filter masks and the type of professional behaved as independent predictors of headache risk, while being asthmatic behaved as a protective factor. the occurrence of headache is associated with the use of a filtering mask (ffp2 or kn95), or 2.14 (ic95% 1.07-4.32), being a health worker or 6.94 (ic95% 3.01-16.04) or a nurse or 2.09 (ic95% 1.18-3.72). table 3 . according to the type of mask used there was no difference in the number of days with headache in the month prior to the survey 13.4 (sd 7.4) vs 12.6 (sd 6.9), nor in the previous week 3.9 (sd 1.6) vs 3.6 (sd 1.7), but in the intensity according to vas 5.7 (sd 1.5) vs 6.5 regarding the evaluation of self-perceived work stress by means of the 12 items of the ppq, individuals with "de novo" headache versus those without headache have significantly worse scores in all aspects evaluated, except for the decrease in appetite where no significant differences are observed. figure 2 shows graphically the evaluation of occupational stress according to the presence of headache or not. the use of a filtering mask compared with surgical mask only implies a significantly worse score in two aspects: gastrointestinal discomfort (p=0.047) and greater sensation of extreme tiredness (p=0.004). the current situation experienced by the covid-19 pandemic has led to a substantial change in the work flows of health professionals. one of the most important features has been the use of ppe for the care of patients with suspected or infected sars-cov2. according to the data obtained, we demonstrate a statistically significant association between the use of filtering masks and the appearance of headache. in the physiopathology of new-onset headache, the exact mechanisms may be multiple, complex and not always well known. peripheral nociceptive structures and central sensitization mechanisms may be involved in their development [14, 15] . the current international headache classification proposes, generically for secondary headaches, that the diagnostic criteria do not require remission or improvement of the underlying causal disorder before the diagnosis is formalized. there is criterion a (presence of the headache), criterion b (presence of the causal disorder) and criterion c (evidence of the etiopathogenesis). and for acute processes, a close temporal relationship between the onset of the headache and the onset of the suspected causal disorder is usually sufficient [11] . following this classification, mask-associated headache would probably be a multifactorial disorder with unknown etiopathogenesis at present. hypothetically, a number of factors may explain the association with filtering mask use, including hypoxia, hypercapnia, local compression and mechanical phenomena, as well as anxiety about wearing the device [10] . in the scientific literature there are not many studies that relate the use of face masks to changes in the concentration of oxygen and/or carbon dioxide but it seems a plausible hypothesis due to the barrier element that is interposed in the physiological ventilation mechanism. in a taiwanese cohort of 39 patients with end-stage renal disease who wore n95 masks during the 2002 sars outbreak, they measured, among other variables, the level of pa02 before and after a 4-hour hemodialysis session. the study concluded that there was a significant reduction in pao2 from baseline and an increase in other respiratory adverse effects [16] . another study conducted in a cohort of 130 astronauts subjected to high co2 pressures during controlled training showed a significantly higher incidence of headache in the exposed group, in addition to respiratory symptoms and difficulty in concentrating [17] . at the university of wollongong (australia), a study on the effects of co2 inhalation on workers wearing respiratory protection devices showed that high levels of carbon dioxide were associated with feelings of discomfort and significantly reduced tolerance and time of device use [18] . in the world of sport, the effect on respiratory physiology and muscle performance of wearing training masks designed to simulate a variable altitude situation has been studied. the results are mixed in terms of objective performance parameters, however, it does seem common that mask use reduces working speed and negatively influences levels of alertness and task focus [19] . in 2014, a pilot study evaluated the consequences on respiratory physiology of surgical mask and n-95 face mask use in a sample of 87 patients and the extent to which nasal inspiratory and expiratory resistance and discomfort were altered in the individuals. physiological changes such as increased respiratory resistances were observed after three hours of use [20] . headache associated with filtering mask use could be included according to in the section on headaches due to homeostatic disorders where those related to alteration of oxygen and carbon dioxide partial pressure parameters are included. another phenomenon probably related to the physiopathology of headache after ppe use is the external compression that it generates, as recently reflected by the group of ong jj et al [21] . in most cases there is a temporal relationship between the use of devices and the headache, as well as the topographical location of the headache. as with homeostatic changes, ichd-3 typifies a type of headache attributable to uninterrupted compression or traction of pericranial soft tissues [11] . in this situation there is more room for the external compression subtype where the elements of the ppe (glasses or protective shields and masks, mainly n95) produce compression over several hours on different facial regions. kymchatowski et al. analysed a cohort of 82 military police in rio de janeiro exposed to the regulatory helmet, and reported headache occurrence in all cases after wearing the helmet for at least 1 hour, with 92.7% disappearing after the removal. in addition, they reported that headache was clearly different from other headaches suffered in 64.6% of the cases. one third of the sample presented migraine, referring to the fact that the new headache was more intense and completely limited the development of their activity. it was also observed in all subjects of the cohort that the headache did not reproduce after removing the stimulus for five weeks [22] . finally, a study of 212 health professionals assessing demographic factors, time of n-95 mask use and the existence of previous headaches showed a relatively high prevalence of mask headache among health workers who worked in high-risk areas during the 2003 sars epidemic [10] . the last factor to be mentioned is the level of anxiety or stress. multiple ways of relating the level of stress to the occurrence of headache have been described, either as "de novo" occurrence or as exacerbation in an individual with primary headache [23] . in the case of the sars-cov-2 pandemic, health care workers may be affected by critical incident stress (cis). critical incidents are events in which people witness or experience tragedy, death, serious injury or threatening situations, which can have a strong emotional impact. the signs and symptoms of cis can be physical, cognitive, emotional and behavioural [24] . in our work, we observed that the level of stress in headache subjects is significantly worse in all aspects measured by ppq. we also showed that the risk of developing headache is higher among nurses and other health professionals than among physicians. the explanation for this result is complex, but there are three plausible hypotheses. as a general rule, doctors live with a higher level of stress in the course of their work, and therefore, situations considered conflicting do not increase their usual stress threshold excessively [25] . it could also be explained by the use of negative coping strategies in some professional groups as opposed to others [26] , these strategies, which we have not measured in our work, would be related to professional level. the third potential explanation, in line with some published studies, is that the higher risk of headache among nurses and other health professionals than in the medical group, is due to the differential characteristics of the workers' occupation, which would involve the use of other devices, cleaning materials, activities with greater energy expenditure or changing work shifts [27] . different factors or comorbidities that may influence the development of headache have been described in the literature [28] . if we look at risk markers, age and sex deserve special attention. the female sex is closely related to the development of "de novo" headache [29] . age is a determining factor in the classification of headache according to the international headache society [11] . several studies have shown that pain intensity [30] , the degree of headache disability, and the possibility of secondary headache occurrence are age-related factors [31] . in terms of other individually modifiable risk factors, the relationship between blood pressure changes and primary headache should be highlighted, as they share mechanisms of action such as vascular endothelial dysfunction or poor cardiovascular autonomic regulation [32] . however, in our study we did not find a clear association between different comorbidities of the individual and the appearance of headache, except for tobacco consumption in the univariant analysis. in a review of the relationship between smoking, its different components and the occurrence of headache, controversial data were obtained. the studies conducted in this regard are mostly retrospective and limited, and there is no definite evidence that tobacco is an independent cause of headache occurrence. however, most migraine patients define it as a trigger [33] . headache is one of the most pronounced symptoms in patients suffering from asthma, a fact that has been described in a few studies so far. in a study of 93 patients, a statistically significant difference was found in this area, as 62.4% of asthmatics had headache (migraine or tension), whereas in the control group the percentage was only 32.8%. other factors such as the use of steroid inhalers, the presence of rhinitis, conjunctivitis or respiratory parameters such as fev1 were studied and characterized [34] . in our study, being asthmatic would act as a protective factor against headache associated with mask use, perhaps because of a greater tolerance to hypoxia, and therefore a higher threshold for developing headache for this reason. our study has some limitations that should be noted: the sample is one of convenience and there has been no previous probability sampling. we could not include or under-represent some professional groups. the study is cross-sectional, which helps us to formulate hypotheses, but we cannot prove causality. we have not taken into account the temporal evolution of the headache in the health professionals who present it. nor have we taken into account other external factors that may influence the headache, such as the exact conditions of the site and type of work. in our study, we described the occurrence of "de novo" headache with the use of filtering masks and its negative impact on multiple dimensions of the life of healthcare professionals. we propose headache associated with the use of this type of mask as a new subtype of headache, of a multifactorial nature and complex etiopathogenesis. and since the use of these devices will tend to become more widespread due to the implications of the pandemic, we believe it is important to promote prevention and protection strategies that guarantee the safety of workers, without undermining their quality of life. none. a novel coronavirus from patients with pneumonia in china clinical features of patients infected with 2019 novel coronavirus in wuhan world health organization. coronavirus disease (covid-19) pandemic. geneva: who of health of the regional government of extremadura. health and social services. communication facial protection for healthcare workers during pandemics: a scoping review professional and home-made face masks reduce exposure to respiratory infections among the general population use of face masks in covid-19 discomfort and exertion associated with prolonged wear of respiratory protection in a health care setting headache classification subcommittee of the international headache society. the international classification of headache disorders headache and the influence of stress. a personal view professional burnout among public school teachers. public personnel management new daily persistant headache classification of daily and near daily headaches: proposed revisions to the ihs classification the physiological impact of wearing an n95 mask during hemodialysis as a precaution against sars in patients with end-stage renal disease acute effects of the elevation training mask on strength performance in recreational weight lifters effects of long-duration wearing of n95 respirator and surgical facemask: a pilot study headaches associated with personal protective equipment -a cross-sectional study among frontline healthcare workers during covid-19 headaches due to external compression understanding psychological stress, its biological processes, and impact on primary headache posttraumatic stress and depression in the aftermath of environmental disasters: a review of quantitative studies published stress and headache chronification stressors and coping strategies of nurses and emergency department doctors: a crosssectional study prevalence of primary headache realted to work activity in a group of hospital workers undergoing periodic visits epidemiology and comorbidity of headache prevalence of headache in europe: a review for the eurolight project characteristics of elderly-onset (â�¥65 years) headache diagnosed using the international classification of headache disorders, third edition beta version pain rates in general population for the period 1991-2015 and 10-years prediction: results from a multi-continent age-period-cohort analysis the effects of facemasks on airway inflammation and endothelial dysfunction in healthy young adults: a double-blind, randomized, controlled crossover study assessment of headache in asthma patients we want to thank juan rodrigo ross for his invaluable help in the preparation of this paper.also to all colleagues, health workers who have responded with great rigor to the questionnaire. josã© m ramã­rez-moreno reports no disclosures.david ceberino reports no disclosures.alberto gonzã¡lez-plata reports no disclosures.belen rebollo reports no disclosures.pablo macã­as-sedas reports no disclosures.roshu hariranami ramchandani reports no disclosures.ana m roa reports no disclosures.ana b constantino reports no disclosures. key: cord-318660-47dqa1dd authors: jain, mehr; kim, sonya t; xu, chenchen; li, heidi; rose, greg title: efficacy and use of cloth masks: a scoping review date: 2020-09-13 journal: cureus doi: 10.7759/cureus.10423 sha: doc_id: 318660 cord_uid: 47dqa1dd during the coronavirus disease 2019 (covid-19) pandemic, there has been a global shortage of personal protective equipment (ppe). in this setting, cloth masks may play an important role in limiting disease transmission; however, current literature on the use of cloth masks remains inconclusive. this review aims to integrate current studies and guidelines to determine the efficacy and use of cloth masks in healthcare settings and/or the community. evidence-based suggestions on the most effective use of cloth masks during a pandemic are presented. embase, medline, and google scholar were searched on march 31, 2020, and updated on april 6, 2020. studies reporting on the efficacy, usability, and accessibility of cloth masks were included. additionally, a search of guidelines and recommendations on cloth mask usage was conducted through published material by international and national public health agencies. nine articles were included in this review after full-text screening. the clinical efficacy of a face mask is determined by the filtration efficacy of the material, fit of the mask, and compliance to wearing the mask. household fabrics such as cotton t-shirts and towels have some filtration efficacy and therefore potential for droplet retention and protection against virus-containing particles. however, the percentage of penetration in cloth masks is higher than surgical masks or n95 respirators. cloth masks have limited inward protection in healthcare settings where viral exposure is high but may be beneficial for outward protection in low-risk settings and use by the general public where no other alternatives to medical masks are available. disposable surgical face masks (also termed procedure masks) and respirators are essential components of personal protective equipment (ppe) for preventing the transmission of infectious diseases. both the canadian and international guidelines highlight the importance of proper usage of ppe among frontline healthcare workers (hcws) during the current coronavirus disease 2019 (covid-19) pandemic [1] [2] [3] [4] . the shortage of ppe observed worldwide as a result of this pandemic places both hcws and patients at risk [5, 6] . although guidelines from the world health organization (who) and centre for disease control and prevention (cdc) suggest various strategies to optimize the supply of ppe in healthcare settings [4, 7] , there are limited data on alternatives to surgical masks. in these situations, 3d-printed respirators or community-sourced homemade cloth masks may be potential sources to meet demand in healthcare and community settings. cloth masks are defined as masks made of cloth or any other fabric that has been previously used to make masks, such as cotton, gauze, silk, or muslin [8] . surgical masks are certified/rated medical ppe that are fluid-resistant and are effective to protect the wearer from large particles of respiratory secretions known as droplets. comparatively, respirators, which are also certified medical ppe and have a variety of ratings (of which n95 is the most commonly used in north america), are useful for user protection against small respiratory particles known as aerosols or droplet nuclei [9] . in both cases, the primary reason these ppe are used in healthcare is the protection of the wearer or inward protection. however, there is an additional role of both surgical masks and respirators to retain respiratory particles in order to avoid spread to others, also known as outward protection. prior to the covid-19 pandemic, the usage of cloth masks in healthcare and the community is commonly observed in many asian countries, including china and vietnam [10, 11] . during the severe acute respiratory syndrome (sars) outbreak in 2002, there were reports of the usage of cotton cloth masks among hcws in china [12] . in the current covid-19 pandemic, chinese recommendations on face mask use in community settings suggest that cloth masks could be used in a very low-risk population to prevent the spread of disease [13] . in the western world, the use of cloth masks is rarely witnessed in healthcare settings due to the availability of surgical masks and respirators. in times of a global pandemic with limited resources, cloth masks may be useful in protecting hcws and retaining fluids and droplets in infected patients. however, there is a lack of comprehensive literature that summarizes the latest findings on the extended use and reusability of cloth masks [9] along with limited guidance on its use during the covid-19 pandemic. this review aims to integrate current studies and guidelines to determine the efficacy of cloth masks as both inward and outward protective equipment and whether they can be used in healthcare settings and/or the community in light of the ppe shortage. furthermore, evidence-based suggestions are made on the most effective use of cloth masks during the times of pandemic. the search strategy was conducted on march 31, 2020, using an open date search strategy. the search terms used were "masks", "respiratory protective device", "facemask" to capture articles studying face masks. the terms "cotton", "cloth", "homemade", "home made", "diy", "do it yourself", "t-shirt", "muslin", "gauze", "cheese cloth", "towel", "fabric", "tight woven" and "tight weave" were used to find articles related to cloth masks. the search strategy was employed on embase, medline, and google scholar. the search strategy was updated on april 6, 2020. the titles and abstracts obtained from search strategies were screened by three reviewers (c.x., s.k., m.j.). discrepancies were resolved by discussion between the three reviewers. the same reviewers also completed the full-text review. the reference list of studies selected for the review was screened by one reviewer to gather additional articles. the study population comprised hcws and healthy volunteers. two studies, one observational and one rct, were conducted on hcw participants [10, 14] . another three studies were conducted on healthy volunteers [18, 20, 21] . of the nine studies, four used cotton cloth masks [10, 14, 17, 18] , one used polyester masks [19] , and four [15, 16, 20, 21] compared different types of materials commonly found in a home as possible materials for homemade masks. the characteristics and results of each study are summarized in table 1 three studies measured inward protection of cloth masks in human subjects [10, 14, 21] . out of three studies, one rct showed that the cloth mask group had the highest rate of influenza-like illness compared to the medical mask group and control group and cautioned that cloth masks should not be recommended for hcws in high-risk settings [14] . however, the results from this study are difficult to interpret as the control group was "standard practice", comprising individuals using both medical and cloth masks. one other study showed that homemade masks made of tea cloth provided protection during short-and long-term activities compared to no mask [21] . ma et al. showed that while n95 respirators blocked 99.98% avian influenza virus, cloth homemade masks and surgical masks were comparable (95.15% and 97.14%, respectively). these homemade masks used in the experiment were made from polyester and kitchen towels [19] . three articles showed that cloth masks resulted in higher rates of infection or particle exposure as compared to surgical masks [10, 14, 21] . three studies specifically measured outward protection either with human subjects [18, 20] or by simulating expiration with an artificial head [21] . in human subjects, both surgical and cloth masks were effective in controlling the number of microorganisms released into the environment when coughing, though surgical masks were more effective, especially with smaller particles [20] . in an older study, quesnel showed that a cotton mask, which was not homemade, provided equivalent outward protection as two other surgical masks [18] . in an experimental setup with an artificial head, cloth masks provided marginal outward protection [21] . a few studies compared the filtration efficacy of various household materials [16, 20] . one such study assessed pressure drop across different household materials to assess comfort of material when used in the masks along with filtration efficiency against microbial aerosols. davies et al. used both bacillus atrophaeus (0.95-1.25 um) and bacteriophage ms2 (23 nm) to generate microbial aerosols for the simulation of particle challenge. they found pillowcases and 100% cotton t-shirts to be most suitable to construct more efficacious cloth masks compared to tea towels, vacuum cleaner bags, silk, and so on [20] . another laboratory study evaluated the penetration of monodispersed nacl aerosol particles through cloth masks made of various materials (sweatshirts, t-shirts, towels, or scarves). the penetration of these masks was 35-68% at 20 nm in diameter and 73-82% at 100-400 nm [16] . assuming that sars-cov2 particles are of a similar size as sars-cov particles from the 2002-2004 outbreak (80-140 nm), these nanoparticles are in the relevant size range [22] . studies that compared filtration efficacy of cloth masks to surgical masks or n95 respirators found that particle penetration was consistently higher in cloth masks [14, 15] . another study showed no significant difference in the efficacy of surgical masks compared to wellconstructed reusable four-ply cotton muslin masks when testing micro-and nanoparticles together [18] . higher compliance with cloth masks is seen in low-to middle-income countries and during pandemics due to the overall lack of ppe [10, 15, 20] . during the h1n1 pandemic, the majority of doctors and nurses used cloth masks (self-reported: 59.8%) over medical masks across eight hospitals in beijing, china [10] . another study reported that hcws showed equal compliance when wearing cloth as compared to medical masks (57%), where compliance was defined as wearing the mask more than 70% of the time [14] . the main adverse events that decreased compliance were general discomfort and difficulty breathing, though adverse events were reported in both medical and cloth mask groups (40.4% and 42.6%, respectively) [14] . in kathmandu, nepal, 31% of the general population surveyed were found to wear cloth masks on the streets to protect themselves against pollution [15] . the fit of a mask is an important variable in determining its efficacy. it is considered an area of weakness for cloth masks. davies et al. used the wilcoxon sign rank test to assess the fit of surgical and cotton cloth masks. the participants underwent a variety of head and body movements while wearing the masks, and fit testing was also performed at rest. they determined the fit of surgical masks to be significantly superior (p < 0.001) than cotton cloth masks in all activities and at rest [20] . some studies reported reusability and resulting contamination of cloth face masks; however, only one study quantified this. this study showed a negative linear trend between washing and drying cycles and filtration efficacy (r 2 = 0.99). after the fourth wash and dry cycle, the efficacy of the mask had decreased by 20%. microscopic imaging of these masks after wash and dry cycles showed an increase in pore size, change in pore shape, and decrease in the number of microfibers in each pore after these cycles [15] . there are no current guidelines or standardized protocols on the use or creation of cloth masks. the who presented interim guidelines in march 2020 in the context of the covid-19 pandemic stating that they do not recommend the use of cloth masks in healthcare settings, in the community, or at home [23] . another set of recommendations from who published on april 6, 2020, also stated that cloth masks are not appropriate for hcws. if cloth masks are used locally, the who highly encourages local authorities to assess the masks [24] . the cdc suggests that hcws use homemade masks if certified face masks are not available. however, they state that these masks are not considered ppe. the cdc also recommends that homemade masks should be used with a face shield covering the entire face [25] . furthermore, on april 3, 2020, the cdc released recommendations asking the general population to wear cloth masks in areas where socially distancing is not possible [26] . they also released tutorials on how to create these masks [27] . to our knowledge, this is the first review to descriptively synthesize and evaluate the best available evidence on the efficacy of cloth masks, providing relevant and useful information that can guide public health guidelines during the current covid-19 pandemic. to date, there are little data to make definite recommendations as only one rct [14] and a few observational studies [10, 20, 21] have been conducted on this topic. when assessing the overall clinical efficacy of cloth masks compared to surgical masks, two factors must be considered: inward and outward protection. the general consensus of the included studies is that cloth masks confer some degree of inward and outward protection, but are less effective than surgical masks and n95 respirators [10, 14, 20, 21] . the clinical efficacy of a face mask is determined by the filtration efficacy of the material, fit of the mask, and compliance to wearing the mask [21] . filtration efficacy of a material is the ability to function in both inward and outward protective gear. in general, household fabrics such as cotton t-shirts and towels [16, 20] have some filtration efficacy and were shown to have some protection against virus-containing particles. however, the percentage of penetration in cloth masks was higher than surgical masks or n95 respirators. one study, however, suggested that a reusable cloth mask can have the same filtration efficacy as a surgical mask (98.8%) [18] . surgical and cloth masks provide less outward protection partly due to the weaker seal around these masks. when pressurized droplets or aerosolized particles are released from the user (e.g., during a cough or sneeze), these particles have a higher likelihood of escaping from the sides than the front of the mask due to the mask's fit. cloth masks are inferior to surgical masks or n95 respirators when assessing the fit of the mask [20] . there is greater opportunity for air leakage around the sides of a cloth mask than the other two mask types, which decreases its ability to contain particles released by the user. however, dato et al. showed a reasonable fit of their homemade mask in a letter to the editor of emerging infectious disease. they presented a protocol for homemade 100% cotton masks that yielded a fit factor up to 67 (n95 respirators must have a fit factor of at least 100). their homemade mask provided significant protection in an aerosol challenge. the recommended use of these masks was in situations where n95 respirators were unavailable [27] . compliance of cloth masks does not differ from that of medical masks, indicating that homemade masks or masks of varying household fabrics are not any less comfortable. the main side effects were difficulty breathing and general discomfort, which were not unique to cloth masks [14] . in fact, in low-to middle-income countries, compliance may be higher due to a lack of availability of surgical masks. a study was conducted on focus groups of doctors and nurses in vietnam to assess their compliance and opinions of face masks. the groups reported both cloth and medical masks to be comfortable to breathe through. surgical masks were found to be associated with words such as "safe" and "effective", whereas cloth masks were associated with "dirty" [28] . given the variety of options available for different types of cloth masks, all that have shown comparable efficiency [15] while also allowing users to exert their preference and pick a material more comfortable to them. of the various sources searched, guidelines on the use and efficacy of cloth masks were limited to the who and cdc's commentary on cloth masks not qualifying as ppe and the cdc's suggestion of the general population using homemade masks [23, 25, 26] . the who and earlier cdc [23, 24] guidelines focused on the usage of cloth masks as ppe to protect the user from the environment (inward protection) and did not address the use of cloth masks to contain droplets and secretions produced by infected individuals (outward protection). cloth masks showed some evidence of outward protection [20] and filtration against microbial aerosols and nanoparticles [15] [16] [17] 19, 20] , albeit in varying degrees, depending on the material. as a result, the potential for outward protection of cloth masks in healthcare settings should be better assessed and addressed in international guidelines. there have been other guidelines posted on the websites of the who, cdc, and canadian government, which suggest that cloth masks can aid in covering the mouth and nose when coughing [23, 25, 29] . wearing a mask as prophylactic protection against a cough serves as better source control compared to finding mouth coverings spontaneously as needed. it should be noted that cdc recommended disposing of materials sneezed into [26] . cloth masks can be cleaned to address this point in the guidelines. the government of canada also recommended the use of cloth masks by the public in situations where social distancing is not possible and stated that homemade cloth masks are not a replacement for surgical masks [30] . moreover, british columbia centre for disease control (bccdc) guidelines state that contaminated cloth can be cleaned with other pieces of clothing in a laundry machine. hot water (60-90â°c) with soap should be used to clean the laundry machine [26] . many low-and middle-income use cloth masks in healthcare settings due to a lack of financial resources to support the wide use of surgical masks. recommendations regarding cloth mask use in vietnam, pakistan, and china include wearing them during low-risk activity (e.g., slashes of fluid or blood, bacterial infection) in the situation of the influenza season and a pandemic [31] . therefore, cloth masks that are regulated may provide some protection against viruses and bacteria. another benefit of using cloth masks in healthcare or community settings is that the production of these masks can be outsourced to freelancers or volunteers in the community if a stringent and tested protocol is developed. for example, in the covid-19 pandemic, the lack of face masks and other ppe has been a global concern. michael garron hospital in toronto, canada, asked volunteers to create cloth masks at home for use in healthcare due to lack of face masks. the project has provided volunteers with a protocol to follow when making the mask, but whether this protocol has been studied is unknown [32] . there is a tested protocol available through davies et al.'s research study. this group designed and studied a protocol for cotton cloth masks; however, this protocol was not widely implemented as an effort to standardize or certify commercially available cloth masks [20] . moreover, the cdc has also released a tutorial on creating homemade cloth masks; however, the web article does not state if this protocol or recommended materials to make the mask have been tested [33] . there are several strengths to this review. this review provides a unique detailed analysis of the various characteristics that contribute to droplet retention and mask efficacy, including the filtration efficacy of the material, fit of the mask, and compliance of the user. the strength of this review lies in its systematic search of multiple databases and search strategies developed and conducted in conjunction with a research librarian. moreover, international and national guidelines were collected to present the real-world implementation of existing research on cloth masks. there are also several limitations to consider. firstly, the scope of the recommendations presented in this review was limited by the lack of data available on cloth masks. only one rct has been conducted to date and few observational studies exist. included studies did not present a quantitative analysis of the filtration efficacy and penetration of materials commonly used in cloth masks or report on the number of layers of cloth material required for maximized benefit and comfort. this highlights important research questions that future high-quality studies should explore to increase our understanding of the efficacy and use of cloth masks. secondly, the heterogeneity of the included studies notably precluded a meta-analysis. future studies should focus on defining comparable outcomes. another limitation includes the fact that our search criteria limited our review to focus only on published studies. by not including grey literature, the review potentially misses out on other perspectives and information about the usage of cloth masks. future studies should investigate the effectiveness of masks in reducing travel velocities and distances of droplets and aerosols during expiration and coughing, which may reduce the transmission of covid-19. secondly, studies should also investigate the ability of cloth masks to reduce virus transmission by preventing the user from touching their face or droplets from landing on naso-oral surfaces. lastly, to support the cdc recommendation of only using homemade masks in a healthcare setting if a face shield is worn [25] , studies should investigate the efficacy of cloth masks used with 3d-printed face shields. both are easily producible in situations of ppe shortage such as the covid-19 pandemic, and if proven to provide adequate protection for hcw, they can be easily be produced in bulk by the general public. results from these studies may be used to guide recommendations on the use of cloth masks for the general public when social distancing measures are in place. to better understand the role that cloth masks play in pandemics and infectious control generally, further rcts must be conducted. however, a study by macintyre et al. highlights the ethical challenge in designing a rct for mask use, as hcws in the control group cannot be asked to wear a mask when working in high-risk situations [14] . as this rct did not address outward protection, future studies should look at whether cloth masks worn by infected patients can protect the transmission of infection among hcws by retaining droplets and fluids. future studies should make evident whether they are studying inward or outward protection as this discrepancy was unclear in some studies. cloth masks are shown to have limited inward protection in healthcare settings where viral exposure is high but may be beneficial for outward protection in low-risk settings and use by the general public where no other alternatives to medical masks are available. during unprecedented times, such as the covid-19 pandemic, when some organizations like the cdc are suggesting the general population to use cloth masks in public settings, further studies on cloth masks are imperative. the current data are not enough to guide clinical decision-making. given that cloth masks are used when the supply of surgical masks is low, it is important to assess the true efficacy of cloth masks compared to not wearing any masks. in compliance with the icmje uniform disclosure form, all authors declare the following: payment/services info: all authors have declared that no financial support was received from any organization for the submitted work. financial relationships: all authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. other relationships: all authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work. care of the adult critically ill covid-19 patient covid-19 guidance: independent health facilities using personal protective equipment (ppe) rational use of personal protective equipment ( ppe) for coronavirus disease ( covid-19) : interim covid-19: doctors still at "considerable risk" from lack of ppe, bma warns challenges to the system of reserve medical supplies for public health emergencies: reflections on the outbreak of the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) epidemic in china optimizing supply of ppe and other equipment during shortages use of cloth masks in the practice of infection controlevidence and policy gaps understanding the difference mask-wearing and respiratory infection in healthcare workers in beijing, china health care worker practices around face mask use in hospitals in hanoi, vietnam evaluation of control measures implemented in the severe acute respiratory syndrome outbreak in beijing rational use of face masks in the covid-19 pandemic covid-19, shortages of masks and the use of cloth masks as a last resort optical microscopic study of surface morphology and filtering efficiency of face masks simple respiratory protection-evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles a study on the microbial filtration efficiency of surgical face masks--with special reference to the non-woven fabric mask the efficiency of surgical masks of varying design and composition potential utilities of mask-wearing and instant hand hygiene for fighting sars-cov-2 testing the efficacy of homemade masks: would they protect in an influenza pandemic? professional and home-made face masks reduce exposure to respiratory infections among the general population a novel coronavirus associated with severe acute respiratory syndrome advice on the use of masks in the context of covid-19 strategies for optimizing the supply of facemasks accessed simple respiratory mask: simple respiratory mask maclntyre cr 2015: current practices and barriers to the use of facemasks and respirators among hospital-based health care workers in vietnam communication resources accessed examining the policies and guidelines around the use of masks and respirators by healthcare workers in china, pakistan and vietnam we need 1000 masks every week! use of masks to help slow the spread of covid-19 key: cord-303034-w72oeoxq authors: haischer, michael h.; beilfuss, rachel; hart, meggie rose; opielinski, lauren; wrucke, david; zirgaitis, gretchen; uhrich, toni d.; hunter, sandra k. title: who is wearing a mask? gender-, age-, and location-related differences during the covid-19 pandemic date: 2020-10-15 journal: plos one doi: 10.1371/journal.pone.0240785 sha: doc_id: 303034 cord_uid: w72oeoxq masks are an effective tool in combatting the spread of covid-19, but some people still resist wearing them and mask-wearing behavior has not been experimentally studied in the united states. to understand the demographics of mask wearers and resistors, and the impact of mandates on mask-wearing behavior, we observed shoppers (n = 9935) entering retail stores during periods of june, july, and august 2020. approximately 41% of the june sample wore a mask. at that time, the odds of an individual wearing a mask increased significantly with age and was also 1.5x greater for females than males. additionally, the odds of observing a mask on an urban or suburban shopper were ~4x that for rural areas. mask mandates enacted in late july and august increased mask-wearing compliance to over 90% in all groups, but a small percentage of resistors remained. thus, gender, age, and location factor into whether shoppers in the united states wear a mask or face covering voluntarily. additionally, mask mandates are necessary to increase mask wearing among the public to a level required to mitigate the spread of covid-19. wearing a mask in public is currently a controversial and politicized issue in the united states, even with case evidence from other countries that face coverings help to control the spread of coronavirus disease 2019 (covid-19) [1] . as taiwan, hong kong, south korea, and other countries with almost universal masking have been some of the most successful at reducing daily case and death rates [2, 3] , the united states has largely trended in the other direction, setting national and state records for daily new cases of covid-19 at the end of june 2020. as of september 2020, the united states had recorded more than seven million confirmed cases and over 200,000 deaths [4] . despite the controversy around masking, transmission of covid-19 (caused by the virus sars-cov-2) occurs primarily through respiratory particles from infected individuals and even asymptomatic cases can be contagious [5] . experts in aerosol science, virology, infectious diseases, and epidemiology acknowledge the potential for a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 airborne transmission of the virus [6] . thus, without a vaccine in distribution, masks are one of the few control measures available for protection against the virus because they serve as a physical barrier between people [7, 8] . not only do masks protect the wearer from droplets and some smaller airborne particles, but they also provide source control, stopping particles coming from a wearer. study of the filtration efficiency of different fabrics has shown that even cotton weaves and blends can block viral transmission [9] , so masks can be made virtually cost-free with household materials. while up to 50% of person-to-person transmission of the virus may occur through asymptomatic individuals [10] , many people who have been infected with covid-19 experience significant functional complications within their organ systems. in children and young adults, the disease appears to be mild, but even among previously infected collegiate athletes, potentially life-altering inflammation within the cardiovascular system was detected [11] . thus, even fit young adults are not immune to the harm that the virus can cause within the human body. systemically, cardiovascular [12] , neurological [13] , hepatic [14] , renal [15] , and respiratory [16] complications of the virus have been reported across most age groups. older adults however are the most likely to experience severe outcomes, with one study showing that 86% of hospitalized individuals were at least 50 years old [17] . furthermore, 60% of hospitalized cases were men in this study, and consistent with a meta-analysis showing that males are at greater risk for severe outcomes from covid-19 [18] . overall, death rate increases drastically with age and comorbid conditions, and mortality among hospitalized cases may be as high as 20% [19] . new data is also emerging that suggests previously asymptomatic or "mild" cases are experiencing debilitating negative effects months after infection [20] [21] [22] [23] . given the easy transmission of this debilitating virus from person-to-person and the lifechanging complications across populations, mask wearing is demonstrated to be a very effective and proactive public health tool that will save lives and lessen future public health burden. though the evidence of the efficacy and importance of masks is clear, store policies and public mandates requiring masks in america have been met with protests [24] and, in rare cases, violence [25, 26] . public health research shows these measures may already have reduced cases in the united states by 450,000 through may 22 nd [27] , but the messaging from top-level government officials has been inconsistent [28] and polling suggests that a sizeable portion of the general population are still going out in public without masks [29, 30] , though self-reported behavior is not always reliable. a previous meta-analysis concluded that women were 50% more likely than men to engage in nonpharmaceutical protective behaviors (e.g. mask wearing) during epidemics and pandemics [31] , and in the covid-19 pandemic women report wearing masks more often than men [30] , despite the fact that male sex may be a risk factor for more severe outcomes of the disease [18] . older adults are at higher risk for more severe cases of covid-19 [17, 32] , so it is reasonable to expect that this demographic may wear masks more than younger individuals. mask wearing by retail shoppers may also vary by location, in that groups that report greater resistance to mask wearing may be more concentrated outside of urban areas [33] . specifically, rural areas tend to have higher concentrations of conservative-leaning voters [34] who are reported to be more resistant to wearing a mask [33] . while the initial outbreak in the united states was primarily in cities, rural counties have also some of the highest case rates in the united states per capita [35] . this geographical spread is particularly concerning given that populations that live in non-metropolitan areas are more vulnerable to covid-19 [36] and highlights the need to study pandemic-related health behaviors like masking in rural locations. learning what demographic groups are wearing masks and how mask mandates impact behavior among these groups will help officials to better target public health messaging that promotes the practice among groups with lower usage. to facilitate greater understanding and reliable experimental data on whether gender, age, location, and the presence of mask mandates influence mask wearing in the united states, we conducted a direct observational study at retail stores in wisconsin. observations occurred between june and august 2020. from june 9 th to august 3 rd , 2020, the 7-day average case rate in wisconsin more than doubled (341 to 844 cases) and the percentage of positive cases had increased from 3.5% to 7.4% [37] . thus, during this period, many major retail chain [38] and wisconsin state [39] mask mandates were enacted, allowing for study of mask wearing before and after these regulations went into effect. the primary aim of our study was to determine mask use by gender expression, estimated age, and location. we hypothesized that, without a mandate, mask use among females would be greater than males across all age groups and locations. additionally, that mask use would be greater among older adults (>65 years old) than middle-age (30-65 years old) and young individuals (2-30 years old) and would be less in rural than in urban or suburban areas. a secondary aim of this project was to revisit stores on dates near the implementation of store and state mask mandates to characterize how mask-wearing behavior changes in response to these requirements. we addressed our primary aim by visiting 36 different retail locations across five different counties in southeastern wisconsin. retail stores selected for observation were based largely on geographical spread across milwaukee and the surrounding areas. in the interest of exploring mask wearing among urban, suburban, and rural stores, we designated a center point of the city (united states postal service main office; 345 w st. paul ave, milwaukee, wi, usa) and recorded the linear distance of each store to the city center. based on distance, stores were then placed into urban (<6.1 km from city center; n = 15, 3.2 ± 1.8 km to city center), suburban (11.5-32.1 km; n = 13, 20.5 ± 7.2 km), and rural (>36.9 km; n = 10, 55.8 ± 21.4 km) store groups. visits to stores (n = 38) occurred at various times between 9am and 8pm (june 3 rd -9 th , 2020) and lasted at least 15 minutes (average = 43 min), with observers recording data with writing utensil and paper or mobile device. to address our secondary aim, stores were revisited and data was collected in the same manner on dates shortly before store or state mandates were implemented (n = 7; july 24 th -31 st , 2020), when there was a store mandate but not a state mandate (n = 20; july 22 nd -july 31 st , 2020), and after the wisconsin state mandate began (n = 10; august 1 st -3 rd , 2020). note that the overlap in the secondary visit dates is related to corporate differences in the dates mask mandates began at various stores. stores consisted of grocery and other large big-box retail stores and shoppers were not aware they were being observed. children under the estimated age of two were not recorded and estimated age categories were defined as young = 2-30 years old, middle age = 30-65 years old, older: >65 years old. these ranges reflect the substantial increase in stratified death rates for individuals 30-39 and 65-74 years old when compared to prior age groups (19) . for all observations that were collected, summary sheets were crosschecked by other observers. all procedures involved public observation or accessed public information and did not require review by an institutional review board. to determine the impact of gender, age, location, and their interactions on mask wearing during the initial visit period (june 3 rd -9 th , 2020), multiple logistic regression analysis was performed. sixty individuals who were wearing their mask or face covering improperly (not over nose and mouth) were recorded but excluded from this analysis as they could not be grouped into a dichotomous outcome (mask/no mask). after excluding these individuals, 5517 observations remained for the analysis, and gender expression, age, and location independent variables were dummy coded and entered into a backward elimination procedure with their associated interactions (gender-age, gender-location, age-location, and gender-age-location). limit for variable removal and test classification cutoff were set at 0.025 and 0.5, respectively. adjusted odds ratios (aor) are expressed with respect to reference groups (gender: male, age: young, location: rural) with 95% confidence intervals and significance was determined at p < 0.05. percentage data including incorrect mask wearers from the initial visit (june 3 rd -9 th , 2020) was used to compare to later data (july 24 th -aug 3 rd , 2020) and evaluate the changes in maskwearing behavior in response to mask mandates. all analyses were performed with either microsoft excel (microsoft, redmond, wa, usa) or ibm statistical package for social sciences version 26 (ibm, armonk, ny, usa). over the course of 75 visits, 9935 individuals were observed entering retail stores. of the 5517 individuals we observed during the first round of data collection that could be grouped into a dichotomous outcome (mask/no mask) (fig 1) , 41.5% were wearing a mask or face covering with the general trend across gender, age, and location largely aligning with our original hypotheses (table 1) . females wore masks 7.6% more than males (fig 2a) . additionally, masks were seen at a higher percentage in older than middle-age (+16.1%) and young (+19.8%) individuals (fig 2b) . urban and suburban mask wearing was similar but was much lower at rural stores (suburban: -28.7%; urban: -26.4%; 55.81 ± 21.37 km) (fig 2c) . regression analysis revealed that gender, age, and location all significantly impact the odds of an individual being observed to wear a mask (p < 0.001; fig 3) . results indicate the odds of a female wearing a mask are significantly greater than males (aor = 1.470, 95% ci = 1.313-1.646). odds are also greater for middle age (aor = 1.597, 95% ci = 1.359-1.877) and older adults (aor = 3.434, 95% ci = 2.811-4.195) than younger individuals. the odds of observing someone in urban (aor = 3.847, 95% ci = 3.157-4.689) or suburban (aor = 4.124, 95% ci = 3.418-4.975) areas wearing a mask is also much higher than in rural locations, reflecting the much lower prevalence of masks seen at rural stores. the significant age-location interaction effect (p < 0.001) is largely driven by differential changes in mask-wearing behavior between older adults and the other age groups (fig 2d) . while estimating age and gender is an obvious limitation of this study, the sample was large (~10,000 observations) increasing the study power to offset the effect of variability from the estimations. currently, no peer-reviewed and direct-observational studies of mask wearing are available for comparison to our study findings. preprint study akin to ours also reflects alarming and similarly low percentages of mask wearing in wisconsin [40] . additionally, our data can be discussed in relation to national polls and surveys that addressed mask wearing at about the same time. a may-to-june survey of adults in wisconsin and four other surrounding states indicated 45.1% always wear a mask when they leave home [29] , and data in our study lends credibility to this number. notably, other regions of the united states surveyed reported different habits (33.5-64% mask usage) so direct observational studies in other parts of the country would be beneficial to confirm national variability when mask mandates are not in place. another poll conducted in mid-april indicated that only 36% of adults always wear a mask or face covering when outside the home [30] , so perhaps usage nation-wide has gradually improved even when masks are not required. women also reported wearing a mask more often than men. so why are men wearing masks in public places less than women? perhaps masks are viewed as a sign of fragility or weakness among some men in the usa, as suggested in previous preprint work [41] . in this case, public health messaging that focuses on aligning masks with masculinity would likely be beneficial to improve usage among males in the united states. alternatively, women may be more likely to protect themselves and others by wearing a mask because they handle the majority of caregiving within families [42] , or because of awareness of the preexisting gender inequalities in social, political, and economic systems that have been further amplified due to the pandemic [43] . it is not surprising that our june data showed that older individuals wear masks more than middle-age and young people because older adults are at higher risk for more severe cases of covid-19. however, the low percentage of young individuals wearing a mask combined with their potential to be asymptomatic [44] creates problems for case containment. a key and underreported benefit of masks is source control, so mask wearing is important across all age groups. lower-risk individuals put older adults and those with preexisting conditions of all ages at risk of severe illness by not wearing a mask due to the potential for asymptomatic viral transmission. one of the most interesting findings of the current study is the evidence of drastically different mask-wearing behavior in rural areas compared with urban and suburban shoppers when mask requirements are not in place. the odds of urban and suburban shoppers wearing a mask was about 4x greater than for rural store-goers during our june data collection period, possibly reflecting the fact that individuals shopping in rural areas perceive lower risk. however, it has been previously reported that mask-wearing habits do not appreciably differ between counties with low and high numbers of covid-related deaths [30] . further, while living population density may be lower in rural regions, the size of retail stores is relatively uniform. thus, differences in the density of shoppers in stores across regions is likely far less than the actual population density differences reflect. understanding why rural shoppers may resist the use of masks more than shoppers in other areas is an important issue because the health care system in these areas of the united states may be less equipped to handle large spikes in cases. rural residents may also need to travel further for emergency care, putting them at greater risk for severe consequences of infection. for these reasons, public health messaging that promotes masks in rural communities is critically important. by the last week of july 2020, for stores with no mask mandate, wearing increased to about 80% overall (fig 4) . this may reflect some improvement in voluntary compliance, as many stores had announced mandates to be enforced at later dates. thus, some individuals may have been moved to comply due to the prospect of needing to wear a mask for future shopping trips. within these data there were no discernable age-related differences, but it was still evident that more females (82.2%) were wearing masks than males (77.8%). data after store and the wisconsin state mask mandates began shows mask wearing increased to over 90% overall (fig 4) . modeling studies suggest mask usage needs to be to nearly universal to have a significant effect on the epidemiological curve [45, 46] , and our results emphasize that mask mandates are necessary to approach this goal. if public officials do not enact these mandates the welfare of shoppers will continue to be left to retail corporations. while retail store mandates obviously improve mask-wearing compliance among shoppers, our data may indicate that that store regulations could be slightly less effective than mandates enacted by government as a slightly higher percentage of individuals were observed correctly wearing masks after a state mandate began (96% vs 93% with store mandate only). mask mandates obviously improve usage, but it deserves mention that a small percentage of the population still resist masks even with retail store and government regulations in place. though it may be argued that some shoppers might have a health condition that precludes wearing a mask, the centers for disease control and prevention only recommend against mask wearing if an individual has trouble breathing or is unable to remove a face covering without assistance [47] so it is improbable that this is a valid explanation for all of the mask resistors observed with a state mandate (2%; fig 4) . mask-wearing mandates are necessary to reduce person-to-person transmission of covid-19 and save lives as a portion of the general public will resist wearing masks in retail stores without them. even with mandates in place, some individuals still resist or wear them incorrectly, putting employees, other shoppers, and themselves at risk due to the potential for viral transmission from asymptomatic carriers [5, 10] . encouraging voluntary compliance to mask wearing is critical so that retail employees do not have to play the role of "mask police", risking verbal or physical abuse from resistant shoppers. close encounters (within six feet) are a great risk to adjusted odds ratios (aor) and 95% confidence interval plots of mask usage for gender expression, age, and location during the initial data collection period from june 3 rd -9 th , 2020. odds ratios are expressed in relation to reference groups (gender: male; age: young; location: rural). https://doi.org/10.1371/journal.pone.0240785.g003 who is wearing a mask? employees if the resistor without a mask is infected. though some stores provide masks to shoppers after entering, there is still a short period that these individuals are inside of the store without masks on. as the possibility of aerosolized transmission of covid-19 was recently confirmed [48] , every breath and word spoken without a mask on (or without one covering mouth and nose) and especially indoors, increases risk of aerosolized virus spread. thus, it is critical to wear a mask from entrance to exit of any public indoor space. to further reduce the number of individuals entering without a mask, stores may benefit from providing masks to shoppers that need them outside of the entrance, where possible. averting cases of covid-19 will save lives so wearing a mask is a public health service and should not be viewed as a symbol of fragility of the individual. wearing a mask is not about stopping transmission of all cases but minimizing case rates and lessening the public health burden. importantly, the long-term effects of covid-19 are still unknown so mask wearing is also vital to reduce burden from future comorbidities that may result within individuals who were infected. masks are an essential public health intervention for combatting the pandemic, and only 41% of individuals observed in our june sample were wearing a mask when entering a retail store. this is less than half the percentage needed to have a significant effect on the reducing the mask-wearing compliance was poor in june but had improved immediately before mandates began. compliance rose to > 90% with a mandate in place across all demographics, but a small percentage of the population still resisted. the overlap in "before" and "with store mandates" dates is related to corporate differences in the dates mask mandates began. https://doi.org/10.1371/journal.pone.0240785.g004 spread of covid-19 [45, 46] . males, younger individuals, and shoppers in rural communities were observed wearing masks less than other groups. however, with store mandates and a state-wide mandate to wear a mask, we showed that mask-wearing compliance rose to over 90% in all groups, including those that resisted mask wearing in june. as officials around the united states continue to debate mask mandates at local and state levels, our data indicated that mandates are necessary to ensure mask-wearing compliance among the public meets the minimum threshold to take control of the covid-19 pandemic. our data also highlights that a portion of the general population does not follow public health recommendations without them. furthermore, even with mandates in place a portion of shoppers (~4%) still resist or wear masks ineffectively. individual shoppers may consider this information to evaluate the potential risks of in-person shopping based on store and local mask policies, location, and the age and gender of the store's clientele. our findings are also important to inform policy makers that mask mandates are necessary to improve compliance to a level that can help flatten the epidemiological curve, saving lives and decreasing burden on the united states health care system. supporting information s1 file. june observations raw data. its contains raw data for the initial data collection period in june. (xlsx) s2 file. july and august observations raw data. its contains raw data for the second data collection period in july and august. the species severe acute respiratory syndrome-related coronavirus: classifying 2019-ncov and naming it sars-cov-2 reducing transmission of sars-cov-2 a modelling framework to assess the likely effectiveness of facemasks in combination with 'lock-down' in managing the covid-19 pandemic united states coronavirus info; c2020 temporal dynamics in viral shedding and transmissibility of covid-19 enviromental health matters initiative face coverings for the public: laying straw men to rest face masks for the public during the covid-19 crisis physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis. the lancet estimating the generation interval for coronavirus disease (covid-19) based on symptom onset data cardiovascular magnetic resonance findings in competitive athletes recovering from covid-19 infection cardiovascular complications in covid-19 neurologic manifestations of hospitalized patients with coronavirus disease manifestations and prognosis of gastrointestinal and liver involvement in patients with covid-19: a systematic review and meta-analysis incidence of acute kidney injury in covid-19 infection: a systematic review and meta-analysis. crit care coronavirus in china features of 20,133 uk patients in hospital with covid-19 using the isaric who clinical characterisation protocol: prospective observational cohort study risk factors of critical & mortal covid-19 cases: a systematic literature review and meta-analysis pathophysiology, transmission, diagnosis, and treatment of coronavirus disease 2019 (covid-19) gemelli against covid-19 post-acute care study group. persistent symptoms in patients after acute covid-19 from 'brain fog' to heart damage, covid-19's lingering problems alarm scientists covid-19: what do we know about "long covid the lasting misery of coronavirus long-haulers. nature anti-vaccine activists, mask opponents target public health officials-at their homes. los angeles times black mayor of kansas city says he was called n-word, received death threat over mask rule. nbc news mcdonald's customer attacks drive-through worker over safety rule community use of face masks and covid-19: evidence from a natural experiment of state mandates in the us mixed messaging on masks set u.s. public health response back. npr the northeast leads the country in mask-wearing. cnn new april guidelines boost perceived efficacy of face masks a meta-analysis of the association between gender and protective behaviors in response to respiratory epidemics and pandemics older adults and covid-19 republicans, democrats move even further apart in coronavirus concerns how the rural-urban divide became america's political fault line latest map and case count rural america is more vulnerable to covid-19 than cities are, and it's starting to show. the conversation wisconsin department of health services covid-19: wisconsin summary data mcdonald's joins walmart and dozens of other chains with mask mandates emergency order #1: relating to preventing the spread of covid-19 by requiring face coverings in certain situations. the state of wisconsin office of the governor use of face coverings by the public during the covid-19 pandemic: an observational study the effect of messaging and gender on intentions to wear a face covering to slow down covid-19 transmission geographies of care and responsibility united nations secretariat. the impact of covid-19 on women age-dependent effects in the transmission and control of covid-19 epidemics bidirectional impact of imperfect mask use on reproduction number of covid-19: a next generation matrix approach. infectious disease modeling this simple model shows the importance of wearing masks and social distancing. the conversation considerations for wearing masks viable sars-cov-2 in the air of a hospital room with covid-19 patients key: cord-351506-ubaoxxg0 authors: nestor, mark s.; fischer, daniel; arnold, david title: “masking” our emotions: botulinum toxin, facial expression, and well‐being in the age of covid‐19 date: 2020-07-12 journal: j cosmet dermatol doi: 10.1111/jocd.13569 sha: doc_id: 351506 cord_uid: ubaoxxg0 background: the globally devastating effects of covid‐19 breach not only the realm of public health, but of psychosocial interaction and communication as well, particularly with the advent of mask‐wearing. methods: a review of the literature and understanding of facial anatomy and expressions as well as the effect of botulinum toxin on emotions and nonverbal communication. results: today, the mask has become a semi‐permanent accessory to the face, blocking our ability to express and perceive each other’s facial expressions by dividing it into a visible top half and invisible bottom half. this significantly restricts our ability to accurately interpret emotions based on facial expressions and strengthens our perceptions of negative emotions produced by frowning. the addition of botulinum toxin (btx)–induced facial muscle paralysis to target the muscles of the top (visible) half of the face, especially the corrugator and procerus muscles, may act as a therapeutic solution by its suppression of glabellar lines and our ability to frown. the treatment of the glabella complex not only has been shown to inhibit the negative emotions of the treated individual but also can reduce the negative emotions in those who come in contact with the treated individual. conclusions: mask‐wearing in the wake of covid‐19 brings new challenges to our ability to communicate and perceive emotion through full facial expression, our most effective and universally shared form of communication, and btx may offer a positive solution to decrease negative emotions and promote well‐being for both the mask‐wearer and all who come in contact with that individual. to recognize a mask-wearer's positive emotions such as happiness or friendliness which are largely communicated by a smile. a true or genuine smile, also known as a duchenne smile, employs both the bottom half of the face and the top half of the face. in order to form a duchenne smile, one must smile with both mouth (by showing their teeth) and eyes (through squinting). 4 the average standardized mask typically only allows us to view the squinting half of a smile, which diminishes its genuineness. botulinum toxin (btx) injections are one of the many services deemed "nonessential" that have largely been put on hold during the wide-scale quarantine and social distancing measures taken abroad in order to minimize the spread of covid-19. 5 with these restrictions now being slowly lifted, patients are once again receiving this most common and valued aesthetic procedure for its desired effect of facial muscle paralysis to diminish or eliminate unwanted frown lines and "crow's feet." 6 today however, these effects are now complemented by a mask that hides the lower half of the face, interfering with emotional processing and our ability to interpret each other's emotions through facial expression. how btx acts as a therapeutic alleviator to these mask-induced inhibitions of emotional perception and communication via its visually pleasing effect is the topic of this paper. at this point, covid-19 needs no introduction, but to summarize, it is the infectious respiratory illness caused by the novel coronaprogress to acute respiratory distress syndrome (ards) and multiorgan system failure. 9 the novel coronavirus can be easily spread from person to person via respiratory droplets released by coughing or sneezing and remains infectious in aerosolized airborne form. the virus may also be transmitted from contaminated surfaces and, depending on the type of surface, the virus may remain contagious from less than 24 hours to several days. after exposure to the virus, onset of symptoms may occur from 2 to 14 days with a mean incubation period of 4-5 days. 10 in the absence of an effective treatment, there are three possible outcomes: avoidance of infection, acquired immunity, and death. the highly contagious nature of the virus has contributed to its rapid transmission and a prevalence of infection that has reached a pandemic level. the lack of effective, clinically proven therapy for the coronavirus, which causes a respiratory illness that can lead to respiratory failure and has a comparatively high mortality rate for a viral infection, has forced the population to rely on disease prevention measures. [11] [12] [13] efforts to reduce the rate of disease transmission are essentially behavioral modifications, both self-imposed and government-mandated. these social countermeasures include such behaviors as frequent hand-washing, more vigilant disinfection of surfaces, social distancing, crowd avoidance, self-quarantine, and, most notably, mask-wearing. [14] [15] [16] paul ekman performed a series of experiments around the world in the early 1970s, arguing that there exist six universally recognized facial expressions of emotion regardless of culture: surprise, fear, disgust, anger, happiness, and sadness. 17 while his findings have been hotly debated in the field for decades, and numerous studies examining the topic have subsequently been performed, a common finding is that reading the eyes provides the most information about an emotional expression. 18 however, the mouth is also very informative and helps to distinguish between several emotions such as fear and surprise or between sadness and disgust. wearing a mask has been shown to make the discernment of emotions much more difficult largely in part because it hides the mouth. 19 the social consequences of mask-wearing due to covid-19 cannot be understated, particularly with regard to its interference in the way in which we communicate through facial expression. as research shows that observers tend to reconstruct an average face when viewing faces that are partly masked in order to form an interpretation. when doing so, some areas of the face tend to have more influence on the observer's ability to correctly interpret the corresponding emotion than other areas do. 21, 22 a recent study highlights the importance of the eyes and mouth in allowing observers to correctly interpret an emotion. the study presented individual faces expressing basic emotions behind a mask of 48 tiles that were sequentially uncovered to observers (or subjects). the subjects in the study were instructed to halt the progression of the sequence as soon as they recognized the emotion that was being revealed to them and to assign it the correct label. each revealed tile which was equivalent to each of the 48 parts of the face was given a value of importance based on its ability to contribute to the observer's recognition of the facial expression being revealed. results showed that observers relied mostly on tiles that revealed the mouth and eyes when correctly identifying the emotion being displayed. subjects identified fear and sadness largely by focusing on the eyes, whereas disgust and happiness were more successfully identified when subjects focused on the mouth region. 20 if applied to today's social environment, these results would suggest that happiness and disgust are not as likely recognized in those wearing masks that hide the mouth. fear and sadness, on the other hand, may overshadow the emotion of happiness since the eyes which produce these emotions are visible while the mouth is occluded. occlusion of the mouth and the eyes has also been shown to decrease the accuracy and speed of recognition of emotions in both children and adults. 23 mouth occlusion has been shown to cause a greater decrease in facial expression recognition than occlusion of the eyes which makes the interpretation of anger, fear, happiness, and sadness much more difficult to detect than expressions more solely dependent on the eyes such as disgust. 24 the importance of the eyes and mouth in facial emotional perception has allowed us to group emotions systematically into "upper-face" and "lower-face" expressions. focusing on one half without the other makes us prone to confuse certain emotions for other ones. when viewing the upper half of a face such as one hidden behind an n-95 mask, we tend to confuse anger with disgust. when viewing a face displaying only the bottom half, such as one wearing a blindfold, we are prone to confusing fear with surprise. 20 what may even further weaken the observer's perception of the mask-wearer's facial emotion is the potential lack of incentive to form a particular emotion among the mask-wearer. making facial expressions is largely used for the purpose of communicating with an observer, and if the mask-wearer is not able to communicate his or her facial expression to an observer as it is blocked by a barrier, then one may ask why he or she would expend the energy to form a full facial expression to begin with or even a facial expression at all. this brings the added inhibitory effect by the expressor themselves in addition to the mask barrier. the potential lack of incentive among mask-wearers to form facial expressions while wearing a mask may not only be a detriment to the observer's ability to detect the mask-wearer's emotions but to the mask-wearer's ability to perceive the emotions of others and even their own. this idea stems from the theory of embodied emotion or the facial feedback hypothesis (ffh) which suggest that feedback from facial muscles influences emotion of the expressors themselves. 25 electromyography (emg) studies have demonstrated the correlation of activity of facial musculature with self-reported mood. subjects that viewed unhappy imagery exhibited increased activity of frown muscles on emg and depressed mood simultaneously. [26] [27] [28] while interpretation of emotions is compromised by mask-wearing, so too is reciprocation. facial mimicry is the activation of specific facial muscles to create congruence in response to an emotional facial expression. 29 for example, individuals react with a smile in response to seeing a happy face and react with a frown in response to a sad face. the emotions of the viewer also follow the expressions and that individual feels happy or sad. these reactions are often of very low intensity and have been measured to occur within the first 500 milliseconds of stimulus onset, typically outside of conscious awareness. 30 it appears these reactions occur automatically as a reflex, and they cannot be suppressed, even when instructed to do so. 31 covering half the face with a mask reduces the subconscious ability to properly interpret and mimic the expressions of those with whom we interact. recognition of and response to the outward emotional displays of one's peers is a critical and necessary component of social interaction as it helps individuals to modify their behavior in order to align with social communication and behavioral norms. 32 when these emotional displays are inhibited by physical barriers such as masks, our ability to communicate effectively with one another is drastically limited and we are primarily left with mimicking negative (frown) emotions. with the lifting of covid-19-inspired restrictions, the negative psychosocial effects of masks are becoming a reality. the therapeutic potential of btx in alleviating these effects will be discussed further. the effects of btx on displays of facial emotion in the setting of mask-wearing, let alone its effect on facial expression alone, cannot be demonstrated without first understanding the anatomy of facial expression, particularly the formation of frowning and smiling. the frown is principally formed by activation of the glabellar complex, a group of muscles that make up the medial brown depressors: the procerus, corrugator supercilii, and depressor supercilii. 33 the dynamic lines formed by activation of the glabellar complex are called glabellar lines (gl), frown lines, or angry elevens, and they become static and gain permanence with muscular contraction over time just as the lcls do. the glabellar complex muscles are responsible for the outward display of negative emotions such as anger, fear, suffering, and sadness. 34 the treatment of the gls prevents frowning and has been shown to positively impact the emotional perception of the patient by observers and by the patients themselves. 35 the top half of the smile is controlled by the orbicularis oculi which squints the eyes and creates lateral canthal lines (lcl), also known as crow's feet or laughter lines. the crow's feet are one of the most commonly treated targets of botulinum toxin. 36 the combined contraction of the zygomaticus major and orbicularis oculi creates the true, full, or duchenne smile-the showing of teeth with squinting of the eyes. 4 this type of smile is generally interpreted as genuine and friendly compared with a smile that utilizes the zygomaticus major only. 37 when the zygomaticus major is contracted alone, without the accompanying eye squinting, it forms the false, pan am, or botox smile. 38 the muscles that produce the smile are ultimately responsible for the physical display of positive emotions such as happiness, joy, and friendliness. treatment of the lcls by botulinum toxin prevents the display of a duchenne smile which may negatively impact both the observer's emotional perception of the patient and the emotional feedback among patients themselves. 38 as the first coronavirus cases were confirmed in the united states and talk of quarantine became seriously considered, grocery stores were not the only in-demand spots leading up to the stay-at-home orders. across the country, many dermatologists reported large influxes of patients seeking last-minute botulinum toxin injections. one physician in new york city estimated his aesthetic patient load quadrupled in the 2 weeks prior to the quarantine. 39 demand increased both from patients seeking touch-ups and from those seeking first-time treatments. as the quarantine continued, reports surfaced of clinics and spas opening and performing house calls for those willing to pay extra in spite of mandated closures, including a number of celebrities, influencers, and internet stars. [40] [41] [42] still others have reportedly sought injections from less-qualified hands only to end up with undesired results such as drooping eyebrows or asymmetric cheekbones. 39 clearly, the drive to seek a youthful and attractive appearance remains high for many despite the reduction in in-person interaction. june has allowed for elective procedures to resume in many places so long as certain health guidelines are met. 43 many dermatology offices have begun reopening for medical and aesthetic visits with precautions in place such as spaced appointments, extensive personal protective equipment use, temperature checks, and vigorous sanitization of equipment between appointments and at the end of the day. 44 other physicians have forged a more creative route to resuming operations such as one dermatologist in miami, florida, who has been conducting drive-through botulinum toxin injections in his building's garage. 45 time will tell whether these heightened precautions in patient interaction, or some variation of them, will become a permanent fixture of outpatient medicine. apart from the business of botulinum toxin, the psychological impacts of its use during this time of mask-wearing and social distancing should be considered. as discussed above, the ability to interpret the emotional state of others and reciprocate via facial mimicry is ingrained in our dna and highly important in our day-today interactions with our peers. 29, 46 social interactions are dynamic exchanges of information. the observer subconsciously and continuously infers the meaning behind the words, tone, and body language used by the speaker throughout a conversation and also experiences affective emotional reactions to them. in turn, the observer's subsequent effective emotional state as displayed by body language, facial expressions, and verbal responses has a direct effect on the original speaker's emotions. it is a dynamic process, and direct adjustments to unfolding physical characteristics of the other person's movements are made throughout the conversation on both sides. 47, 48 the utilization of a mask hinders that subconscious connection by covering the bottom half of the face such that the eye region alone must be used to gauge and respond to emotions. the problem with this is that we are not conditioned to communicate or express our emotions in this manner. this leads to significant emotional misperceptions and negative facial feedback from our facial expressions that directly impact our moods. the action of frowning gives off the perception of a bad mood. moods are contagious, and this emotional contagion occurs unconsciously. a person's feelings, whether positive or negative, can actually be transferred to another during an interaction. 49, 50 much of this transfer has been shown to occur through unconscious mimicry. 29 in other words, a frown displayed on a patient's face may influence an observer to unconsciously frown as well and a smile can do just the same. the contagious nature of emotions can become even more amplified when individuals are in frequent contact with one another. 51 if this is the case, masks have the potential to amplify the transfer of bad moods by highlighting the glabellar region while it is contracted and forming the most dominant part of the frown. by redirecting our eyes to the glabella while hiding the mouth, masks may intercept the perception of non-negative facial expressions (ie surprise or confidence) that often require both glabella and mouth regions to be seen to fully interpret that particular expression. 52 negative emotions such as anger or sadness are much more pronounced and dependent via glabella only. 34 this is where btx may play an incredibly effective role in diminishing negative emotional perceptions and negative facial feedback that may otherwise lead to the contagious spread of a bad mood. patients with btx-induced paralysis to glabellar muscles have been shown to feel more attractive, exhibit higher self-esteem, confidence, and increased comfort and sociability with others, and report overall increased happiness. 53, 54 these effects are likely attributed to patients' improved self-perceptions as they view themselves in a mirror, but also due to embodied emotion via direct afferent feedback. in the setting of a mask, btx may help to offset the negative emotions that frowning would otherwise add to a maskwearer that may not feel obligated to smile, as discussed previously, and that regularly finds him or herself in public settings that today often bring out emotions of fear and caution which produce negative facial expressions as a result. if btx can bring about positive emotions and prevent the formation or severity of negative emotions among patients, due to the contagious nature of facial expressions, btx's positive effects should be mirrored by the people they come in contact with. in an analysis of 1000 survey responses, on average, the public perceived patients treated with btx to some of the most commonly treated sites including the glabella, as significantly more attractive, trustworthy, intelligent, youthful, naturally beautiful, and likeable than prior to treatment. these patients were also more likely to be invited to social events and asked out on a date following treatment with btx. 55 this demonstrates that btx-induced paralysis to the muscles of the glabella positively impacts the way in which observers emotionally perceive treated patients. overall, public perception of negative emotions in btx-treated patients may be diminished after gl treatment. [56] [57] [58] with prolonged societal use of mask-wearing and the contagious nature of frowning, society may experience an increase in the expression of negative emotions among the general population and in the incidence of depression and depression-related disorders. if the cause is in fact due to mask-wearing and visual misinterpretation of facial expressions, then this is an issue that aesthetics may be able to one's peers is typically interpreted as disingenuous and may result in fewer genuine smiles being directed back at the patient. 37, 67 while wearing a mask, this effect may be even more pronounced. when the lower half of the face is completely covered, it leaves only the eyes to communicate the positive emotive gesture of smiling. in this setting, treating the lcls then makes the display of any smile virtually impossible. while masked individuals can still form the half of a smile that utilizes the mouth, these individuals will likely experience inhibited internalization of the positive emotion attempting to be expressed when they are additionally treated with btx to the lcls. the mask likely inhibits this afferent feedback even further by decreasing a patient's motivation to form the bottom half of a particular facial expression when interacting with others since this half is blocked from sight anyway. thus, with regard to emotional processing, treating the glabella may have largely positive effects while treating the lateral canthal area may have principally negative effects that are likely only heightened with mask-wearing. 38 covid-19 brought to the world more than just widespread disease but also a radical change in human psychosocial dynamics and communication. just as cell phones function as a semi-permanent accessory to our hands or pockets, masks now function in the same manner on our faces. by cutting the visual surface area of our faces in half, masks make it incredibly challenging to display and perceive each other's facial expressions which are critical and necessary components of social interaction as they help individuals to modify their behavior in order to align with social communication and behavioral norms. as the widespread societal adoption of masks continues, it bears the question of what the long-term effects on facial recognition and nonverbal communication will be. as emotional expressions are intercepted, so too may be our ability to practice facial mimicry and recognize or describe one's own emotions and the emotions of others, which is referred to as alexithymia. 68 in an alexithymic society, we would expect our emotions to be flatter, less intense, and less reactionary to the emotional facial expressions communicated to each other on a daily basis. if this is the case, covid-19 brings with it not only a pandemic of global health but a pandemic of emotional communication as well. in a society in which communication has historically been 55% facial, it becomes crucial to find solutions to our diminished ability to communicate in a positive manor via facial expressions that are hidden under a mask barrier. botulinum toxin injection offers a very realistic and practical solution. 69 fortunately, the half of the face that is still exposed even with a mask happens to include the most common target of btx, the glabella, which is responsible for the production of negative emotions by forming the frown. although one of the key players in the formation of a smile and the display of positive emotions, the mouth, is hidden behind a mask, we can still eliminate the display of negative emotions with btx by targeting the glabella. treatment of frown lines offers a significant advantage over the treatment of crow's feet in this day and age because it inhibits the display of negative emotions while treatment of lcls inhibits the only half of a duchenne (or full) smile that is able to be displayed since the mouth is blocked by a mask. research has shown that btx-induced paralysis of the glabella has increased the feeling of positive emotions among patients themselves both by improving patient mood and inhibition of depression. these effects are attributed not only to aesthetic effect, but through direct afferent feedback to the brain as well. since the display of emotions through facial expression including frowning is contagious, btx seems to show promise for improving the emotional perception of patients with btx-induced glabellar paralysis by observers as well. society may need to continue to adapt to the advent of mask-wearing in ways that minimize the psychosocial impact it induces. companies like clearmask ™ may offer a novel solution through the development of the first transparent mask that provides full-face visibility. 70 if widespread daily use of masks continue, the hope is that new innovations such as this one will allow us to no longer hide our faces behind a mask and to once again be able to appreciate the full aesthetic effects that btx offers to millions of patients nation-wide. 71 for now, btx seems to offer a promising role as a powerful psychosocial therapeutic, a function that, while often overlooked, has long-accompanied its use as a classic aesthetic since its inception. https://orcid.org/0000-0002-8978-7932 reduction of head and face pain by challenging lateralization and basic emotions: a proposal for future assessment and rehabilitation strategies nonverbal communication in humans facial expressions of pain and pleasure are highly distinct the duchenne smile: emotional expression and brain physiology: ii factsheet: state action related to delay and resumption of "elective" procedures during covid-19 pandemic state directives ordering a delay patient perceived benefit in facial aesthetic procedures: face-q as a tool to study botulinum toxin injection outcomes searc h?q=globa l+cases +of+covid +19&rlz=1c1ch bf_enus7 79us7 79&oq=globa l+cases +&aqs=chrome.0.0j69i 57j0l6.2899j 0j7&sourc eid=chrom e&ie=utf-8 perspectives for the use of therapeutic botulinum toxin as a multifaceted candidate drug to attenuate covid-19 the incubation period of coronavirus disease 2019 (covid-19) from publicly reported confirmed cases: estimation and application clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in wuhan, china clinical features of patients infected with 2019 novel coronavirus in wuhan covid-19 -navigating the uncharted wearing face masks in the community during the covid-19 pandemic: altruism and solidarity the psychology of wearing face masks in times of the covid-19 masks and coronavirus disease 2019 (covid-19) constants across cultures in the face and emotion holistic gaze strategy to categorize facial expression of varying intensities masking the face: recognition of emotional facial expressions as a function of the parameters of backward masking mapping the emotional face. how individual face parts contribute to successful emotion recognition bubbles: a technique to reveal the use of information in recognition tasks show me the features! understanding recognition from the use of visual information shades of emotion: what the addition of sunglasses or masks to faces reveals about the development of facial expression processing an analysis of facial expression recognition under partial facial image occlusion the principles of psychology facial efference and the experience of emotion vicarious instigation and conditioning of facial expressive and autonomic responses to a model's expressive display of pain manipulation of thought content as a determinant of mood and corrugator electromyographic activity in depressed patients facial mimicry in its social setting rapid facial reactions to emotional facial expressions timing and voluntary suppression of facial mimicry to smiling faces in a go/nogo task-an emg study the social neuroscience of interpersonal emotions. social behavior from rodents to humans advanced techniques for the use of neurotoxins in non-surgical facial rejuvenation facing depression with botulinum toxin: a randomized controlled trial double or bifid zygomaticus major muscle: anatomy, incidence, and clinical correlation onabotulinumtoxina for treatment of moderate to severe crow's feet lines: a review perceptions of duchenne and non-duchenne smiles: a meta-analysis the interactions between botulinum-toxin-based facial treatments and embodied emotions the big droop: what's happening with botox in quarantine? evening standard the ultra-rich are begging for plastic surgery in isolation. the cut rolling stone there's a pandemic happening, so why are people still requesting botox appointments at their homes? allure covid-19) how doctor's offices have weathered the covid-19 pandemic. commercial observer florida offers drive-through botox to quarantined residents. reuters the role of second-person information in the development of social understanding guilt in response to blame from others how emotions regulate social life: the emotions as social information (easi) model why are smiles contagious? an fmri study of the interaction between perception of facial affect and facial movements fashioning the face: sensorimotor simulation contributes to facial expression recognition is a bad mood contagious? scientific american what emotions really are: the problem of psychological categories why do females use botulinum toxin injections? satisfaction of patients after treatment with botulinum toxin for dynamic facial lines does the public perceive a patient after treatment with minimally invasive cosmetics? plastic and reconstructive surgery-global botulinum toxin for glabellar lines: a review of the efficacy and safety of currently available products selection and preference for botulinum toxins in the management of photoaging and facial lines: patient and physician considerations social implications of hyperfunctional facial lines treatment of depression with onabotuli-numtoxina: a randomized, double-blind, placebo controlled trial botulinum toxin for depression: does patient appearance matter? treating depression with botulinum toxin: a pooled analysis of randomized controlled trials evaluation of self-esteem and depression symptoms in depressed and nondepressed subjects treated with onabotulinumtoxina for glabellar lines role of botulinum toxin in depression how your facial expressions affect your business relationships who is approachable? leadership development lessons from positive organizational studies duchenne smile, emotional experience, and autonomic reactivity: a test of the facial feedback hypothesis specific brain processing of facial expressions in people with alexithymia: an h2 15o-pet study communication is 93% nonverbal: an urban legend proliferates news/press -relea ses/ameri cans-spent -more-than-16-billi on-on-cosme tic-plast ic-surge ry-in-2018 key: cord-298433-tev33cjh authors: mardimae, alexandra; slessarev, marat; han, jay; sasano, hiroshi; sasano, nobuko; azami, takafumi; fedorko, ludwik; savage, tim; fowler, rob; fisher, joseph a. title: modified n95 mask delivers high inspired oxygen concentrations while effectively filtering aerosolized microparticles date: 2006-09-22 journal: ann emerg med doi: 10.1016/j.annemergmed.2006.06.039 sha: doc_id: 298433 cord_uid: tev33cjh study objective: in a pandemic, hypoxic patients will require an effective oxygen (o(2)) delivery mask that protects them from inhaling aerosolized particles produced by others, as well as protecting the health care provider from exposure from the patient. we modified an existing n95 mask to optimize o(2) supplementation while maintaining respiratory isolation. methods: an n95 mask was modified to deliver o(2) by inserting a plastic manifold consisting of a 1-way inspiratory valve, an o(2) inlet and a gas reservoir. in a prospective repeated-measures study, we studied 10 healthy volunteers in each of 3 phases, investigating (1) the fractional inspiratory concentrations of o(2) (f(i)o(2)) delivered by the n95 o(2) mask, the hi-ox(80) o(2) mask, and the nonrebreathing mask during resting ventilation and hyperventilation, each at 3 o(2) flow rates; (2) the ability of the n95 mask, the n95 o(2) mask, and the nonrebreathing mask to filter microparticles from ambient air; and (3) to contain microparticles generated inside the mask. results: the f(i)o(2)s (median [range]) delivered by the hi-ox(80) o(2) mask, the n95 o(2) mask, and the nonrebreathing mask during resting ventilation, at 8 l/minute o(2) flow, were 0.90 (0.79 to 0.96), 0.68 (0.60 to 0.85), and 0.59 (0.52 to 0.68), respectively. during hyperventilation, the fio(2)s of all 3 masks were clinically equivalent. the n95 o(2) mask, but not the nonrebreathing mask, provided the same efficiency of filtration of internal and external particles as the original n95, regardless of o(2) flow into the mask. conclusion: an n95 mask can be modified to administer a clinically equivalent fio(2) to a nonrebreathing mask while maintaining its filtration and isolation capabilities. there is worldwide concern about an imminent influenza pandemic. in this event, affected patients will back up in emergency departments (eds) 1 and ambulances, 2 placing their staff at increased risk of infection. these considerations highlight the importance of transmission prevention strategies in the protection of ambulance and ed personnel. currently, their personal protective devices include gloves, gowns, shoe covers, appropriate filter masks, and positive-pressure isolation hoods. 3 these barriers are sometimes ineffective because they are overwhelmed by prolonged exposure and large viral loads 4 or because they are not used properly, in time, or at all. [5] [6] [7] reducing the shedding of infectious particles from contagious patients may provide additional protection for ambulance or ed personnel. although it is commonly recommended that surgical masks be used on potentially infectious patients during periods of patient triage or transportation, it is readily acknowledged that such masks do not provide full protection from infection transmission. 3 standard n95 masks may be more effective in containing potentially infectious particles but will not be suitable for most influenza patients ill enough to seek medical care, because these patients will require oxygen (o 2 ) therapy. o 2 therapy is commonly administered with the nonrebreathing o 2 mask, which is not designed to contain any respiratory droplets. in fact, these masks may actually increase the dispersal of respiratory droplets by jetting them through the mask's open side vents. 8, 9 somogyi et al 8 reported that the use of the hi-ox 80 mask, which is designed specifically to deliver high fractional inspired o 2 concentrations (fio 2 ), can provide respiratory isolation if a bacterial-viral filter is placed on its outlet port. however, the mask is expensive, unfamiliar to many, and not likely to be widely available in numbers sufficient for use as a first-line o 2 mask in the case of a pandemic. the implementation and routine use of an entry-level isolation o 2 mask during initial patient contact could provide an extra measure of protection to front-line health care workers from potentially contagious patients. our approach in designing such a mask was to add a nonrebreathing o 2 manifold to the familiar n95 mask, which provides excellent viral and bacterial filtration and is already widely distributed. we tested the effectiveness of this "n95 o 2 mask" in providing supplemental o 2 and compared it to the nonrebreathing mask and to the hi-ox 80 mask. we then tested the effectiveness of the n95 o 2 mask in protecting the wearer from microparticles in the environment and compared it to the criterion standard in this regard, the n95 mask. we also tested how well the n95 and the n95 o 2 masks retained microparticles originating from inside the mask. finally, although the nonrebreathing mask is not designed to provide respiratory protection or isolation, we included it in particle testing because it is common, at least in our institutions, to find health care workers who believe it confers some level of protection to the wearer or the health care provider. this study is a prospective repeated-measures design. we divided the study into 3 phases. in phase 1, we tested the o 2 delivery characteristics of the n95 o 2 mask, the hi-ox 80 mask, and the nonrebreathing mask at resting ventilation and hyperventilation, each at 3 o 2 flow rates (to view photographs of the masks, see figure e1 , available online at http://www.annemergmed.com). in phase 2, we tested the protection function (ie, the ability of the mask to filter microparticles from ambient air) of the n95 mask, the n95 o 2 mask, and the nonrebreathing mask. in phase 3, we tested the masks' isolation function (ie, the effectiveness of each mask in containing microparticles generated inside the mask). we did not include the hi-ox 80 in particle testing, because its protective and isolation function would be that of the particular filter placed on its expiratory port, and this information is already well documented (eg, see dellamonica et al 10 ) . neither subjects nor investigators were blinded to the type of mask being used for any of the test phases. all tests were conducted in a well-ventilated patient room at a university teaching hospital, with the door closed. after receiving institutional ethics research board approval, we obtained signed informed consent from 10 volunteers for each of the 3 phases of the study. subjects were recruited by posted advertisement. inclusion criteria were healthy nonsmoking men (without facial hair) or women between the ages of 18 and 60 years, with no active respiratory disease. we tested the o 2 delivery characteristics of 3 masks as characterized by the fio 2 that they supplied. the we protect health care workers from communicable disease by giving them protective equipment and using devices that decrease emission of infectious agents from the source patient. this study shows that an n95 mask can be modified to deliver oxygen to a person in a manner similar to a nonrebreathing mask while providing significant emissions reduction. what this study adds to our knowledge it is possible to practically increase protection for clinicians treating infectious patients with airbornetransmissible diseases, without compromising oxygen therapy for the patient. if faced with an influenza pandemic, another severe acute respiratory syndrome-like outbreak, or patients with a dangerous communicable illness, clinicians may be afforded another level of protection through use of a similar device without compromising patient care. healthcare, yorba linda, ca) and the nonrebreathing mask (airlife adult oxygen mask; cardinal health, mcgaw park, il). we modified the n95 mask to allow for o 2 administration by adding an o 2 delivery manifold similar to that of a standard nonrebreathing mask. the manifold consisted of a 1-way valve, an o 2 inlet port, and an o 2 reservoir ( figure 1 ). the hi-ox 80 mask was modified by placing a bacterial-viral filter (dar sterivent mini; mallinckrodt dar, mirandola, italy) on its expiratory port. 8 subjects were fitted with the hi-ox 80 and initially asked to breathe normally (resting condition). an o 2 flow of 2, 4, or 8 l/minute was selected randomly by draw. we chose these o 2 flow rates for 2 reasons. first, the hi-ox 80 is rated to provide clinically useful fio 2 at these flows. 11 second, using lower flows with o 2 masks may be necessary in case o 2 supplies become limited, as when treating mass casualties (eg, during a pandemic). subjects were not told of the o 2 flow being administered. once end-tidal pco 2 (petco 2 ) and end-tidal po 2 (peto 2 ) reached a steady state (defined as less than a 2 mm hg change in petco 2 during 2 minutes), minute ventilation, petco 2 , and peto 2 were recorded for 2 minutes. subjects were then asked to increase their minute ventilation sufficiently to reduce their petco 2 by 10 mm hg below their resting values (hyperventilation) and maintain that level of petco 2 . once steady state was achieved at the target petco 2 , minute ventilation, petco 2 , and peto 2 were again recorded for 2 minutes. subjects then reestablished steady-state resting ventilation, after which the test was repeated for the other 2 o 2 flow rates. after testing the hi-ox 80 at all 3 flow rates, the other 2 masks were tested (in random order) using the same protocol. the hi-ox 80 mask was tested first because it is the only mask that permits measurement of minute ventilation. we were then able to use the petco 2 to match the minute ventilation when testing the other masks. we tested the protective function of the masks by measuring the extent to which particles originating from ambient air leaked into the mask during normal breathing. we tested the n95 mask (3m model 1870, 3m, for 9 subjects; aero mask, aero co, southbridge, ma, for 1 subject), the n95 o 2 mask (constructed from the same models of n95 mask stated previously), and the nonrebreathing mask. six of the subjects were hospital employees who had been previously fit-tested with n95 masks. we therefore used the same model of n95 mask for their tests. the remaining 4 subjects who were not previously fit-tested were arbitrarily supplied with the 3m model 1870. although there is a possibility this may have introduced variability in our data, the arbitrary use of masks simulates cases in which this mask would be applied to a patient as an infectious barrier. each mask was prepared in advance by inserting a gas sampling port into the mask material ( figure 2 ). the particle generator was turned on and infused microparticles freely into the closed room for 20 minutes before subject testing to increase the atmospheric particle concentration in the room to more than 200/cm 3 . the test mask was placed on the subject's face, and subjects were instructed to breathe normally. after at least 2 minutes, we recorded particle concentrations outside the mask and then from inside the mask for 30 seconds each. we tested the isolation function of the same 3 masks by measuring the extent to which particles originating from inside the mask leaked out into the surrounding air. masks were prepared in advance by inserting sampling and particle infusion ports into the mask. subjects were instructed to breathe figure 2 . particle testing setup. the n95 oxygen mask contains an internal gas sampling port and a separate port used for microparticle infusion. normally. background particle concentrations were measured 6 cm in front of the mask during 30 seconds with the particle generator off. the particle generator was then turned on and the particles directed into the mask through a plastic tube attached to one of the ports. after an equilibration period of at least 60 seconds, we recorded particle concentrations for 30-second periods from inside the mask, 6 cm in front of the mask and 50 cm to the side of the mask. the latter location simulates the location of a health care worker's face while attending a patient. both protective and isolation tests were performed once for the n95 mask. for the n95 o 2 mask and the nonrebreathing mask, the tests were performed with o 2 flow rates of 2 and 10 l/minute. o 2 flow to the masks was controlled by a calibrated flow meter (voltek enterprises, toronto, ontario, canada). gas was sampled continuously from the oropharynx and analyzed for co 2 (ir1507; servomex fairfax, ca) and o 2 (ufo130-2; teledyne-ai, city of industry, ca) partial pressures (pco 2 and po 2 , respectively). tidal gas was sampled from the oropharynx by a catheter inserted through a sealed port in the mask, which allowed accurate sampling of end-tidal gases without dilution from the high flows of o 2 . a particle generator, model 8026 (tsi inc, shoreview, mn), was used to generate a steady flow of ultrafine (approximately 0.2 m) sodium chloride particles that are easily suspended in air. particle concentrations were measured with portacount plus, model 8020 (version 2003 rev k; tsi inc), which is rated for detecting the concentration of particles as small as 0.02 m. 12 pco 2 and po 2 signals were digitized and recorded continuously by a data acquisition and analysis program (labview; national instruments, austin, tx). petco 2 and peto 2 were identified using a custom peak detection algorithm and converted to fractional concentrations (fetco 2 and feto 2 ). for each o 2 mask, ventilation, and flow combination, average fetco 2 and minute ventilation (where applicable) were calculated during 2-minute steady states for each subject. fio 2 was calculated for each breath from fetco 2 and feto 2 using the alveolar gas equation 13 (fio 2 is a flowaveraged value of the o 2 concentration during inspiration and is reflected in the exhaled concentrations of co 2 and o 2 ). for each o 2 mask, ventilation, and flow combination, average fio 2 s were calculated during 2-minute steady states for each subject. during particle testing, on average, 15 to 20 discrete measurements were recorded for each 30-second sampling period and entered manually into a spreadsheet for analysis. for each subject, background concentrations recorded outside the mask were averaged. we used fio 2 as the marker of effectiveness of o 2 delivery. we assumed the n95 mask to be the criterion standard for particle filtration; clinical equivalence was assumed for masks whose performances were comparable to that of the n95. the protective function of each mask was quantified by measuring the concentrations of particles inside the mask and expressing each discrete measurement as a percentage of average external concentrations. the isolation function of each mask was quantified by measuring the external particle concentrations while infusing particles into the mask and expressing each discrete measurement as a percentage of change from the average background concentrations measured before the particle generator was started. descriptive statistics and graphical methods were used to display our results. we used bar graphs to display average fio 2 values for all subjects. box plots were used to display data points obtained during particle testing to illustrate the variability in particle concentrations that we observed over time. all quantitative results are expressed as median (range). with the hi-ox 80 mask, subjects' minute ventilation and petco 2 (pooled for all o 2 flow rates) were 5.8 l/minute (2.3 to 9.5 l/minute) and 39.9 mm hg (34.9 to 44.5 mm hg), respectively, at rest and 14.9 l/minute (9.0 to 23.1 l/minute) and 29.2 mm hg (24.7 to 33.9 mm hg), respectively, during hyperventilation. the petco 2 (our marker for ventilation) for the n95 o 2 mask and the nonrebreathing mask (also pooled for all o 2 flow rates) was equivalent to that obtained by testing the hi-ox 80 (39. 6 the hi-ox 80 consistently delivered a higher fio 2 than the other masks, with greater margins at higher o 2 flow rates ( figure 3 ). the fio 2 obtained from the n95 o 2 mask was clinically equivalent to that from the nonrebreathing mask for both resting ventilation and hyperventilation. during resting ventilation and at 8 l/minute o 2 flow, the fio 2 delivered by the hi-ox 80 was 0.90 (0.79 to 0.96), consistent with that predicted by the package insert. under these conditions, the fio 2 with the n95 o 2 mask and nonrebreathing mask was 0.68 (0.60 to 0.85) and 0.59 (0.52 to 0.68), respectively. for protective function, the n95 o 2 mask provided the same efficiency of filtration of outside particles as the n95 mask at o 2 flow rates of 2 and 10 l/minute (figure 4 ). median particle concentrations inside the n95 and n95 o 2 masks at 2 and 10 l/minute were less than 1% of those outside the mask (0.0% to 3.0%). in contrast, high particle concentrations were found inside the nonrebreathing mask, with o 2 flow at 2 l/minute (53% [37% to 87%]) and with o 2 flow at 10 l/minute (17% [3% to 37%]). for isolation function, the n95 o 2 mask provided the same efficiency of filtration of inside particles as the n95 mask. there was no increase in external particle concentrations above background values measured outside either mask, regardless of distance from the mask or o 2 flow into the n95 o 2 mask ( figure 5a , b). in contrast, particle concentrations measured outside the nonrebreathing mask were markedly higher than background values at 6 cm and 50 cm from the mask: 800% (62% to 3100%) and 450% (100% to 12,000%), respectively, when o 2 flow rates were 2 l/minute and 330% (15% to 1300%) and 95% (33% to 3000%) when flows were 10 l/minute. we studied the o 2 delivery characteristics of the 3 masks in healthy volunteers, not patients. the justification for this method is that the marker of effectiveness of o 2 delivery we studied-fio 2 -depends only on the characteristics of the mask, the o 2 flow, and the minute ventilation of the subject. the latter 2 were controlled in this study. moreover, arterial partial pressure of o 2 and oxyhemoglobin saturation depend not just on the fio 2 but also on such individual patient factors as the ventilation-to-perfusion ratio and shunt. therefore, arterial blood gases and oxyhemoglobin saturation measurements in patients with pulmonary and other pathology are not required for evaluation of mask-specific o 2 administration efficiency. we tested a group of 10 subjects for each phase of the protocol, but several subjects did not participate in all 3 phases of the study. however, for the phase of the study in which an individual subject did participate, he or she tested all 3 masks. furthermore, the measured parameters of each phase of the study are totally independent of each other. we studied the ability of the masks to filter microparticles, and we attempt to make inferences on their performance with other sized particles, such as respiratory droplets. nevertheless, the 0.2-m microparticles generated by the tsi particle generator are widely used to test for effectiveness of mask fit and filtration and are reasonable surrogates for such infectious particles as viruses (which are 20 to 300 nm), bacteria (tubercle bacillus; 0.2 to 0.6 by 1.0 to 10 m), 14 and aerosolized respiratory droplets (ï¾10 m). in vitro testing has shown that n95 material prevents the penetration of approximately 95% of ms2 viruses (approximately 27.5 nm in diameter). 15 the isolation function of the hi-ox 80 mask with filter was not compared directly with that of the n-95 o 2 mask for 2 reasons. first, its isolation function would reflect the type of filter used, of which a large variety is available. second, if the fio 2 of the hi-ox 80 is clinically necessary, the n95 o 2 mask is not a suitable alternative. we propose that the n95 o 2 mask provides an fio 2 similar to, and therefore is a suitable alternative for, that of the nonrebreathing mask. still, under some circumstances when isolation function is the critical issue, a direct comparison may be necessary. because of the nature of our study setup, it was not possible to blind subjects or investigators to the type of mask being used. there are 2 main findings of our study. the first is that an n95 o 2 mask can deliver o 2 at least as effectively as a nonrebreathing mask. the second is that an n95 o 2 mask retains its filtration function for small particles in both directions. although it is accepted that a properly fitted n95 mask provides the wearer with a high level of protection from inhaling external particles, our study is the first to demonstrate that the n95 filter material is also effective in preventing particles originating inside the mask from escaping into the surroundings in vivo. this could not be assumed from its proven protective function, because the inside of the mask is exposed to moisture, higher gas flows and pressures, and much higher concentrations of particles than those present on the outside. an implication of these findings is that the n95 o 2 mask may be effective in respiratory "isolation" by restricting the spread of similarly sized infectious particles from an infected patient. in contrast, whereas people are frequently admonished to cover their mouths with their hands when they cough or sneeze to protect others (a practice popularized during the 1918 influenza pandemic), we found that covering the mouth with the nonrebreathing mask provides no reduction in particle concentrations at 6 or 50 cm from the subject breathing at rest. furthermore, persistence of high particle concentrations inside the nonrebreathing mask casts doubt on any assumption that o 2 flow into a nonrebreathing mask will in any way protect a patient from inhaling others' respiratory droplets. because no controlled studies outlining the full mechanisms of person-to-person transmission of influenza have been published, 16 we must make certain inferences from animal studies and observational and inoculation studies in humans. it appears that influenza is transmitted by droplets (ï¾10 m), aerosolized droplet nuclei (ï½10 m), and by direct and indirect contact (see bridges et al 16 and salgado et al 17 for reviews). during the severe acute respiratory syndrome (sars) outbreaks, it was assumed that reducing the dispersal of respiratory droplets from infected patients would help control the spread of infection. to this end, the world health organization guidelines state: "suspected cases should wear surgical masks until sars is excluded." 3 health canada guidelines similarly recommend that a surgical mask be placed on the patient "until sars is excluded or the patient is admitted into the room." 18 however, it is also recognized that a surgical mask "does not provide adequate respiratory protection to the wearer [ie, health care worker] if the infection is airborne." recent studies in vitro have demonstrated that surgical masks can allow the penetration of more than 80% of virions 27.5 nm in diameter 15 -besides those that escape from the gaps in the mask seal to the face. the same would obviously apply to the isolation function of a surgical mask when worn by a contagious patient. although quarantine of the patient may be effective in limiting contacts, it does not reduce the infectious load on those who enter the room and approach the patient or who participate in direct patient care. 19 when o 2 is administered to a patient, respiratory isolation is even more problematic. our study confirms earlier work demonstrating that standard o 2 masks do not provide effective containment of droplet or nuclei-sized particles and, furthermore, may even contribute to the pattern and extent of spread. 8, 9 these considerations would be of greatest concern to such front-line health care workers as emergency medical services (ems) and ed personnel who are required to attend symptomatic patients before any definitive diagnosis is made. the intensity of exposure is increased for these personnel for 2 reasons. first, they may have to provide high-risk interventions such as o 2 administration 9 and endotracheal intubation. 6 second, the duration of exposure will likely be prolonged because filling of inpatient and critical care areas will result in table e1 (available online at http://www.annemergmed.com). "boarding" of patients in the ed and ambulances. 20 the risk to ems workers appears to be particularly great when ems are placed on hospital bypass because it leaves these workers in close quarters with sick patients for prolonged periods. a number of limitations to the use of the n95 o 2 mask may arise in actual clinical practice. one would still have to rely exclusively on health care worker-worn barrier devices when patient isolation is impossible (as during endotracheal intubation or bronchoscopy 6 ), as well as for patients for whom a good mask seal is difficult to obtain (for example, edentulous patients or patients with full beards). the n95 o 2 mask will also not be suitable for patients requiring an fio 2 greater than 0.7, nebulized medication, invasive or noninvasive ventilatory assistance, or airway protection. one would also expect that the limitations of the original n95 mask (eg, deterioration of filtration function with prolonged use, excessive handling, and accumulation of moisture) may also apply to the n95 o 2 mask. indeed, increased airflow resistance and the perception of increased work of breathing were commonly experienced by health care workers after prolonged n95 mask use during the sars outbreak in toronto. the increased resistance to breathing is likely due to moisture obstructing the pores in the mask material. increased breathing resistance would reduce the ability of breathless patients to tolerate long-term use of the n95 mask. although no detailed studies evaluating the duration of effectiveness of the n95 mask have been done, 21 these considerations indicate that the n95 o 2 mask may be best suited for short-term use, such as during ambulance transport, hospital triage, and transport from one hospital ward to another (eg from the patient room to the diagnostic imaging department). on the other hand, the inspiratory flow resistance may actually be less than that of the original n95 because the n95 o 2 mask includes an o 2 reservoir that provides the major part of the inspiratory volume, leaving only small volumes at low flows at end inspiration to be inhaled through the mask filter material. we tested the masks for only a short period because they were intended to provide a short-term solution to o 2 delivery and respiratory isolation at initial patient contact. extrapolation of these results to more prolonged use should be made with caution. in conclusion, our study indicates that the n95 o 2 mask we constructed can deliver an fio 2 clinically equivalent to that provided by a nonrebreathing mask, although neither is as efficient as the hi-ox 80 . furthermore, the modification of the n95 mask for o 2 delivery retains the same filtration function as the n95 mask. this is the first study to confirm that the n95 mask, as well as our modified version of the mask, is effective in retaining microparticles originating inside the mask in vivo. assuming that the kinetics of microparticle distribution studied in humans is a suitable model to study the risk of transfer of infection in humans, we conclude that for o 2 -requiring patients, the n95 o 2 mask appears to provide protection and isolation performance equivalent to that of the n95 mask, whereas the nonrebreathing mask would provide none at all. additional clinical studies are needed to confirm that o 2 administration through this n95 o 2 mask is well tolerated by patients and that its use actually reduces the risk of disease transmission from infectious patients to health care workers. nrm, nonrebreathing mask. *the protection function of each mask was quantified by measuring the concentrations of particles inside the mask and expressing each discrete measurement as a percentage of average external concentrations. *the isolation function of each mask was quantified by measuring the external particle concentrations while infusing particles into the mask and expressing each discrete measurement as a percentage of change from the average background concentrations. once upon a time in the emergency department: a cautionary tale the effect of emergency department crowding on paramedic ambulance availability world health organization. world health organization hospital infection control guidelines critically ill patients with severe acute respiratory syndrome sars among critical care nurses transmission of severe acute respiratory syndrome during intubation and mechanical ventilation effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (sars) dispersal of respiratory droplets with open vs closed oxygen delivery masks: implications for the transmission of severe acute respiratory syndrome evidence of airborne transmission of sars comparison of manufacturers' specifications for 44 types of heat and moisture exchanging filters efficiency of oxygen administration: sequential gas delivery versus "flow into a cone" methods comparison of n95 disposable filtering facepiece fits using bitrex qualitative and tsi portacount quantitative fit testing evaluation of five oxygen delivery devices in spontaneously breathing subjects by oxygraphy manual of clinical microbiology do n95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks? transmission of influenza: implications for control in health care settings influenza in the acute hospital setting public health agency of canada. severe acute respiratory syndrome (sars) identification and containment of an outbreak of sars in a community hospital medical care capacity for influenza outbreaks infection control guidance for respirators (masks) worn by health care workers: frequently asked questions: severe acute respiratory syndrome (sars) key: cord-310948-nt378esz authors: edwards, n. j.; widrick, r.; potember, r.; gerschefske, m. title: quantifying respiratory airborne particle dispersion control through improvised reusable masks date: 2020-07-14 journal: nan doi: 10.1101/2020.07.12.20152157 sha: doc_id: 310948 cord_uid: nt378esz objective: to determine the effectiveness of non-medical grade washable masks or face coverings in controlling airborne dispersion from exhalation (both droplet and aerosol), and to aid in establishing public health strategies on the wearing of masks to reduce covid-19 transmission. design: this comparative effectiveness study using an exhalation simulator to conduct 94 experiment runs with combinations of 8 different fabrics, 5 mask designs, and airflows for both talking and coughing. setting: non-airtight fume hood and multiple laser scattering particle sensors. participants: no human participants. exposure: 10% nacl nebulized solution delivered by an exhalation simulator through various masks and fabrics with exhalation airflows representative of "coughing" and "talking or singing." main outcomes and measures: the primary outcome was reduction in aerosol dispersion velocity, quantity of particles, and change in dispersion direction. measurements used in this study included peak expiratory flow (pef), aerosol velocity, concentration area under curve (auc), and two novel metrics of expiratory flow dispersion factor (edf) and filtration efficiency indicator (fei). results: three-way multivariate analysis of variance establishes that factors of fabric, mask design, and exhalation breath level have a statistically significant effect on changing direction, reducing velocity or concentration (fabric: p = < .001, wilks' {lambda} = .000; mask design: p = < .001, wilks' {lambda} = .000; breath level: p = < .001, wilks' {lambda} = .004). there were also statistically significant interaction effects between combinations of all primary factors. conclusions and relevance: the application of facial coverings or masks can significantly reduce the airborne dispersion of aerosolized particles from exhalation. the results show that wearing of non-medical grade washable masks or face coverings can help increase the effectiveness of non-pharmaceutical interventions (npi) especially where infectious contaminants may exist in shared air spaces. however, the effectiveness varies greatly between the specific fabrics and mask designs used.  the strength of this study is that it offers quantitative evidence on the effectiveness of wearing non-medical improvised masks in controlling airborne dispersion of particles from exhalation.  study can aid in establishing public health strategy that encourage the wearing of masks or face coverings for reducing airborne transmission of infectious disease in shared air spaces.  a limitation of this study is that is uses an exhalation simulator with the ppe industry standard nacl test solution for particle generation rather than a clinical study with exhalation of biomaterial particles.  the particle sensors used had a limited ability to detect fast moving aerosol clouds from coughing or talking with no-mask applied. in light of the current pandemic from rapid transmission of the severe acute respiratory syndrome coronavirus 2 (sars-cov-2 or covid-19) and significant morbidity, there has been inconsistent medical guidance given to the public regarding the wearing of non-medical improvised fabric masks or face coverings to reduce the transmission of covid-19. if the sars-cov-2 aerosol is considered with an ability to infect for more than 3 hours with tcid50 of greater than 10 2 as noted in a recent laboratory study [1] then the understanding the effectiveness of non-medical masks and face coverings to control human exhalation aerosol dispersion has significant importance for broad public health infectious disease strategy, especially with asymptomatic or pre-symptomatic populations. of concern, recent studies show that bio-droplets of all sizes are generated from normal exhalation [2] [3] [4] [5] with 80-90% of droplets from human exhalation in the size range of 0.1-1µm, [6, 7] those from a cough can travel 23 to 27 feet (7-8 m) which is well beyond the recommended social distances of six feet or two meters, and smaller aerosols (≤5µm) stay aloft in the air and pose a greater risk for severe infection. [8, 9] in addition, social distancing is difficult to accomplish since many essential locations like grocery stores have aisles are narrow and result in the proximity of patrons being closer than 1 meter; reduced distance correlates to increased transmission of covid-19. [10, 11] a lack of definitive data on establishing the effectiveness of using non-medical masks or face coverings has resulted in medical practitioners giving broad public health guidance based on professional judgement only. existing guidance includes statements that facial coverings may offer minimal protection from small infectious particles, may only reduce large particulate matter, or only remind users to not touch their face considering infectious disease transmission from hand to face. a number of previous studies have been conducted to understand if wearing of masks reduce community infections of common diseases such as influenza, however most are inconclusive due to the application of masks post-exposure or lack of strict wearing compliance by study participants. [12] [13] [14] only a few well-executed studies conclude the prophylactic wearing of medical grade masks reduce community transmission of influenza or rsv. [15, 16] to make matters worse, the lack of definitive guidance has also led to social and political debates on the wearing of masks or face coverings [17] [18] [19] and deters the acceptance of any new public health strategy for reducing airborne transmission of infectious diseases. prior studies have established the filtration efficiency of a variety of fabrics but do not consider reducing covid-19 transmission by controlling airborne dispersion of human exhalation. [20] [21] [22] [23] [24] [25] [26] [27] other research investigates only forward dispersion of particles from coughing or sneezing by measuring a on a single optical plane, [8, 28] or on the aerodynamics of exhalation particles inside various rooms. [29] [30] [31] [32] several clinical studies showing reductions in virus shedding when wearing face masks,[2,3,5,33-35] but neither the clinical nor experimental studies have fully characterized the effectiveness of non-medical grade reusable masks in controlling aerosol dispersion of human exhalation particles in terms of three-dimensional direction, velocity, and particle concentration of various diameters in real world environments. the goal of this research is to determine the statistically significant factors and effectiveness of non-medical grade washable masks or face coverings in the control of aerosol dispersion of human exhalation, and to aid in establishing public health strategies or policies on the wearing of masks. [36] although broad clinical studies on the use of non-medical masks would offer results directly correlated to the community reduction of infectious diseases, this original research offers the experimental results that establish a basis for conducting such a study along with a more comprehensive set of effectiveness measurements for mask designs. we conducted a comparative effectiveness study using a randomized full factorial design of experiments with 10% nacl nebulized solution and an exhalation simulator to conduct 94 experiment runs with combinations of 8 different fabrics, 5 mask designs, no-mask as a control, and exhalation airflows (pef and fev1) that represent both talking and coughing. the experiment also included randomized runs of no-mask applied as the control and a preliminary comparison with the performance of a merv13 air filter media which has similar electrostatic filtration properties to the niosh n95 standard (95% filtration efficiency of 0.3µm particles). the exhalation simulator was constructed similar to previous research, [37, 38] but with some differences. the exhalation simulator was driven by a dry compressed air expansion chamber and timing-controlled relay, with a port for the small volume jet nebulizer, in-line spirometer, and a corrugated tube to emulate a trachea before exiting the mouth of the cpr manikin. details on the simulator equipment are in (online supplementary figure 1 ). the exhalation airflows were calibrated to simulate peak expiratory flow (pef) of coughing with a range 507l/min to 650l/min and pef for talking of approximately 120l/min as established by previous research. [37] [38] [39] [40] the typical air flows for talking are similar to that of singing. [40] four laser scattering particle concentration sensors (plantower pms5003) were placed at specific locations inside a non-airtight fume hood (online supplementary figure 2) to detect aerosol dispersion directly downward, laterally from the mid-line, and 1 meter forward of the mouth. preliminary testing of the configuration identified that the optimal position when used with various masks in this fume hood was 43 cm below the level of the mouth for all sensors. the frontal sensor represents an approximate halfway point of a 2 meter or 6 feet social distance. a nacl aqueous solution was selected as a polydisperse test aerosol which is also used as the exposure for niosh n95 respirator test methods. 10% nacl was used to generate a sufficient quantity of particles for the open-air fume hood environment and also to stay beneath the pms sensor maximum (65,535 particle count per 0.1l for any given size). the aerosol was produced by nebulizing the solution at 103 kpa (15 psi) for 5 seconds into the aerosol chamber of the exhalation simulator followed by a 3 ms delay before exhalation from the manikin through the applied masks. the simulated exhalations were driven by timing controlled compressed air at 827 kpa (120 psi) for "coughing" and 206 kpa (30 psi) for "talking". the intervention was provided by non-medical grade washable masks sourced from local materials that were available during the covid-19 supply chain interruptions. the fabrics were selected are shown in (online supplementary table 1) (fabric bolts were unavailable) which all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted july 14, 2020. . https://doi.org/10.1101/2020.07.12.20152157 doi: medrxiv preprint included natural fibers, polyesters, and other materials. the mask designs were selected from variety of community-based designs which included a bandana style, surgical mask style, folded no-sew, a simple mask with earloops, and a stylistic mask that had more coverage of the nose. microscopic images of the fabric weave and fibers were taken (keyence vhx-s660e) to further understand and explain the results. more details regarding the fabrics and masks designs and the basic test procedure are also included in the (online supplementary appendix). the primary outcome was to measure any significant reduction in aerosol dispersion velocity, quantity of particles, and change in dispersion direction. measurements used in this study included peak expiratory flow (pef), forced expiratory volume (fev1), as well as aerosol arrival time, time to peak concentration, aerosol velocity, area under curve (auc) for first minute and last minute as shown in figure 1 . a change in direction from sensor 5, reduction in velocity, or auc are considered a positive effect. two novel metrics of filtration efficiency indicator (fei) and expiratory flow dispersion factor (edf) are established in this study to present quantitative values that give relative indicators to the dispersion control performance of non-medical masks using simple and repeatable measurement techniques of the research. a description of all measurements and outcomes are presented in table 1 . indicates general filtration of mask design / fabric by comparing residual particle concentration with mask applied to nomask (control) after system has equalized. max value of the control is used to give ratio of particle conc. all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted july 14, 2020. . https://doi.org/10.1101/2020.07.12.20152157 doi: medrxiv preprint worst case scenario. this is a unitless ratio. quantifies the overall reduction in aerosol velocity and direction from a mask application. this is a unitless ratio of the air velocity from exhalation and velocity of the first arriving aerosol coupled with direction. pef velocity is calculated from a standard volumetric flow formula. = 1 − , a since the data collected is a series of discrete measurements, the auc calculation is similar to a summation of trapezoidal areas but accounts for the ascending and descending edges. fei is a ratio of the particle concentration remaining after exhalation through a mask compared to no-mask and provides a quantitative indicator that aids in the filtration performance characterization. it is a ratio of remaining particle concentration (auc4 to 5 min) with a mask applied compared to the worst-case auc of no-mask applied. since this experiment does not lend itself to directly measure the particle concentration in the aerosol chamber prior to exhalation nor does it use the same calibrated equipment, test orifice and tube size, airflow dynamics, and other equipment from the niosh n95 test standard, [41] the filtration efficiency indicator values are relative to this experiment. similarly, many other recent studies seeking to establish the filtration efficiencies of non-medical grade masks or fabrics have the same constraint on relativity of results. however, while the actual values are relative to this study the fei measurement technique is broadly applicable to all exhalation dispersion studies. we also present edf as a measurement of the reduction in particle velocity and change in direction when a mask is applied. as shown in table 1 , it is the ratio of cloud velocity at the first arriving sensor to that of the exhalation airflow velocity derived from the pef measurement. the theory of edf is based on the airflow from exhalation simulator (bounded volume) and aerosol velocity in fume hood (unbounded turbulent airflow) which are correlated by bernoulli's ideal-gas law and further described in the field of kinetic theory of gases. full derivation of the volumetric flow formula is provided in literature; [42] in this study the airflow of pef equals the cross-sectional area of the spirometer multiplied by the average velocity of the air stream shown in equation (1) = ̅ (1) where: the inside diameter of the mir smartone spirometer was measured to be 28.67 mm which allows for an area calculation. using algebraic relationships, the formula for calculating the velocity of the exhalation using pef measurement is shown in equation (2) along with the unit conversion to meters per second. • . × (2) all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted july 14, 2020. . https://doi.org/10.1101/2020.07.12.20152157 doi: medrxiv preprint sample size: the overall sample size from the full factorial combination of 40 distinct masks, several randomly inserted test runs of no-mask as the control, and 2 exhalation levels resulted in 94 experiment runs. the overall experiment with four sensors and average sampling rate of 1 second, generated over 1.694 million time-series sensor data measurements for this study. the sample size of n=94 resulted in 2,496 measurements for each dependent response variable across all particle diameters. multivariable and multivariate analysis was conducted from the perspective of a null hypothesis that non-medical improvised masks do not affect the dispersion or offer source control. this study determines if the three independent variables (mask designs, fabrics and breathing levels) have a statistically significant effect on any of the dependent responses (direction, auc0 to 1 min, fei, and edf) at various sensor locations. three-way multivariate analysis of variance (manova) is used to simultaneously understand the significance of multiple effects from the independent variables and their correlations while minimizing type i statistical errors (false positives). details on the use of manova and validation against the assumptions of the data, including homogeneity of covariance, normality, independence of observations and multicollinearity [43] [44] [45] [46] [47] are provided in (online supplementary description of statistical methods). matlab version r2019a was used to import the raw data files, compute the response variable values, and calculate summary statistics. spss version 1.0.0.1327 was used to perform manova. to additionally validate the statistical results and measured outcomes, graphical analysis of the data was also performed to identify any anomalies that were not expected in the response variables. the mean (sd) pef for simulated coughing was 532.08 (75.65) l/min and fev1 of 5.92 (0.1) l. likewise, the mean (sd) pef for simulated talking was 148.35 (43.29) l/min and fev1 of 1.79 (0.07) l. both simulated exhalation levels are within range of previous studies. [37] [38] [39] [40] the aerosol particle concentration was measured at the one-meter frontal sensor during the last minute of all no-mask (control) runs and resulted in concentration levels and distribution that indicates good polydisperse particle generation (online supplementary figure 3 ). the mean (sd) concentrations for simulated talking generated peak concentrations of 32,199 (3,683) for 0.3µm particle diameters representing aerosols, and 201(42) for 10µm particle diameters representing droplets. likewise, simulated coughing generated peak concentrations of 27,731 (9,837) for 0.3µm particle diameters, and 131(27) for 10µm particle diameters. table 2 shows descriptive summary statistics of variables with respect to the primary dispersion direction and gives some insight into the generalized responses. the best overall performing mask is the surgical style with internal non-woven layers [auc0 to 1 min = 7.721x10 5 (6.606x10 5 ), fei = .468(.158), edf = .993(.005)]. the best overall fabric depends on a desired characteristic of reduced velocity and direction or increased filtration performance, a general comparison of edf across mask designs is shown in figure 2 . the velocity-ratio related performance for nomask applied, edf = .984(.009), indicates the overall slowdown of particles due to turbulence all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted july 14, 2020. . https://doi.org/10.1101/2020.07.12.20152157 doi: medrxiv preprint and aerodynamics in an open air system. the large standard deviations represent the divergence between the responses for each exhalation breath level (visible in (online supplementary figures 6 -13 ) and also indicate that the interactions between multiple factors and the multivariate responses. in addition, the mean velocities for no-mask are, in some cases, lower than certain masks or fabrics which is related to a pms sensor's sampling rate limitation. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted july 14, 2020. the results from manova on the complete data set are reported in table 3 table 3 shows that the results using pillai's trace are also significant (in case the manova assumptions of homogeneity of variance-covariance were violated). therefore, the null hypothesis that masks or face coverings have no effect on exhalation dispersion or source control is rejected. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted july 14, 2020. the statistics of wilks lambda and pillai's trace (table 3) converge at η 2 = .996 and indicate that 99.6% of the variance of dependent variables are associated with exhalation breath levels of talking or coughing. it should also be noted that there were statistically significant interaction effects between fabric, mask design, breath levels and the combination of all three independent variables also reported in table 3 (fabric*mask design, fabric*breath level, mask design*breath level, fabric*mask design*breath level). in some cases, the between-subject effects were marginally significant (p-value closer to .05), however the vast majority of individual between-subject effects 30/35 (85.7%) are significant. a full multivariate analysis of variance and multivariate tests of between-subject effects and interactions are provided in (online supplementary table 2 and 3) . conclusively, this quantitative comparative effectiveness study establishes that the application of improvised non-medical grade mask designs or fabric combinations were statistically significant in reducing airborne dispersion of particles from exhalation as defined by direction, velocity, auc0 to 1 min, fei and edf. the statistically significant interaction effects between combinations of all primary factors and partial η 2 values further establish the strong correlation of outcomes to fabrics used, mask design, and exhalation breath levels. this foundational research offers an orthogonal but complimentary result to previous research on respiratory protection and personal protective equipment which exclusively looks at inhalation filtration and airflow pressure gradients that support respiration. when considering airborne dispersion control (also known as source control in some literature) it is important to understand the primary mechanisms that affect the dispersion. the field of filtration theory offers significant understanding with the primary mechanisms for the respiratory use case: interception, brownian diffusion, inertial impaction, and sieving or blocking filtration. [48] [49] [50] [51] since the fibers and fabric meshes are typically larger than small aerosols or infectious particles at 5µm diameters or smaller, the first three filtration mechanisms are most applicable to this study and other studies in the field of personal protective equipment (ppe). special emphasis is placed on inertial impaction and brownian diffusion to disrupt the velocity and direction of airborne dispersion. further discussion on filtration mechanisms is provided in (online supplementary appendix). all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted july 14, 2020. . https://doi.org/10.1101/2020.07.12.20152157 doi: medrxiv preprint one observation from this study is that the effectiveness in dispersion varies greatly between the specific fabrics and mask design combinations. for example, the factors of fabric, mask design, and the interaction of fabric and exhalation breath level that have significant effect on fei, while other factors and interactions are not significant (online supplementary table 3) . this suggests that a fabric's dynamic characteristics such as pliability (i.e. conforms to the face for fit and coverage) and dynamic response to airflow force (i.e. stretch characteristics) have an effect on the overall filtration of exhaled particles. ad hoc test data of a stretch fabric commercially available mask is consistent with this statement (online supplementary table 5). further materials analysis and characterization is justified to fully understand this observation however it does emphasize that proper wearing of masks [52] [53] [54] is important for ppe usage as well as dispersion control. characterization of fabric thickness, fiber density and weave, as well as layering will also aid in establishing accurate predictor coefficients of a dispersion control linear regression model for specific fabrics and masks. the strength of this study is that it offers quantitative evidence on the effectiveness of nonmedical improvised masks for helping to establishing public health strategies or policies that encourage the wearing of masks or face coverings. fundamentally the effectiveness of nonpharmaceutical interventions (npi) can be increased by reducing exhalation particle dispersion and is especially important where infectious contaminants may exist in shared air spaces. an overall public health strategy must consider the additive effect of wearing masks and face coverings for inhalation filtration (ppe) and that of dispersion and source control. however, the strategy would need to account for the non-ideal performance of various fabrics and masks, where the ideal particle dispersion performance would offer 95% filtration efficiencies and dispersion contained to the user's body. combining this research with recent community sir modeling [55] can help provide significant insights to the public health strategy. to summarize, it would be of most benefit for all people in community settings to wear masks and get full effect of controlling exhalation particle dispersion to reduce transmission of highly infectious respiratory diseases such as covid-19. one limitation of this study is that it provides approximations of human exhalation using polydisperse nacl solution rather than actual exhalation. real human exhalation adds additional compositions of particles that can be smaller than 0.3µm in diameters, moisture, proteins, gases, and other bio material[56] so the longer term effectiveness of masks for source or dispersion control cannot be directly established from this data, however this study utilizes industry and niosh accepted proxy for testing respiratory barriers of nacl. another limitation was the pms sensor performance: measurement minimum of 0.3µm particles and a slower intake fan speed limited its ability to accurately measure all characteristics of fast moving particle clouds from that of no-mask applied. regardless, the sensor data and experiment design were sufficient to determine statistical conclusions on the effects of wearing masks and face coverings of different fabrics and designs. future works should consider using a large test chamber and more sensors to result in more accurate measurement of airborne dispersion and turbulent airflows. all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted july 14, 2020. . https://doi.org/10.1101/2020.07. 12.20152157 doi: medrxiv preprint the results show that the application of various non-medical grade mask designs or fabric combinations were statistically significant in reducing airborne dispersion of particles from exhalation during coughing and talking as well as singing. however, the effectiveness varies greatly between the specific fabrics and mask designs used. the best overall performing mask design is a surgical style with internal non-woven layers, while the best overall fabric depends on a desired characteristic of reduced velocity, change in direction, or increased filtration performance. conclusively this study can aid in establishing public health strategies or policies that encourage the wearing of masks or face coverings to increase the effectiveness of nonpharmaceutical interventions (npi) especially where infectious contaminants may exist in shared air spaces. mr. edwards was the principal investigator and primary author, ms. widrick created the design of experiment and conducted the mathematical analysis, dr. potember assisted in conducting background research and guided the approach to experimentation and rigor of analysis, mr. gerschefske assisted in the laboratory configuration and testing. we extend our appreciation to the american red cross of southeastern colorado and el paso county public health for allowing the use of cpr training equipment and manikin to rapidly conduct this study. we also acknowledge mr. asher edwards for his contributions to the early code development for the data acquisition system, and ms. lydia edwards for providing continuous awareness of open news research and public vetting of concepts. 56 popov ta. human exhaled breath analysis. ann allergy asthma immunol 2011;106:451-6. doi:10.1016/j.anai.2011.02.016 figure 1 : examples of the measurements performed on the time-series data from all experiment runs for each of the four sensors and particle sizes of 0.3µm, 0.5µm. 1µm, 2.5µm, 5µm, 10µm maskdesign all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted july 14, 2020. . https://doi.org/10.1101/2020.07.12.20152157 doi: medrxiv preprint aerosol emission and superemission during human speech increase with voice loudness the airborne lifetime of small speech droplets and their potential importance in sars-cov-2 transmission the size distribution of droplets in the exhaled breath of healthy human subjects size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of covid-19 collection, particle sizing and detection of airborne viruses physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis natural ventilation for infection control in health-care settings face mask use and control of respiratory virus transmission in households review of economic evaluations of mask and respirator use for protection against respiratory infection transmission national academies of sciences e. rapid expert consultation on the effectiveness of fabric masks for the covid-19 pandemic mask use, hand hygiene, and seasonal influenza-like illness among young adults: a randomized intervention trial respiratory syncytial virus (rsv) infection rate in personnel caring for children with rsv infections: routine isolation procedure vs routine procedure supplemented by use of masks and goggles trump shares tweet that says masks represent 'slavery and social death' -business insider mandatory masks aren't about safety, they're about social control the mask wearing debate is dividing america. and the messaging isn't getting any clearer assessment of fabric masks as alternatives to standard surgical masks in terms of particle filtration efficiency multilayer nonwoven fabrics for filtration of micron and submicron particles simple respiratory protection--evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles aerosol filtration efficiency of common fabrics used in respiratory cloth masks evaluating the efficacy of cloth facemasks in reducing particulate matter exposure the ultimate guide to homemade face masks for coronavirus. smart air filters effectiveness of common fabrics to block aqueous aerosols of virus-like nanoparticles visualizing the effectiveness of face masks in obstructing respiratory jets covid-19 outbreak associated with air conditioning in restaurant no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity novel coronavirus (covid-19) pandemic: built environment considerations to reduce transmission towards aerodynamically equivalent covid19 1.5 m social distancing for walking and running how sneeze particles travel inside an airplane | popular science testing the efficacy of homemade masks: would they protect in an influenza pandemic respiratory source control using a surgical mask: an in vitro study utility of substandard face mask options for health care workers during the covid-19 pandemic to mask or not to mask: modeling the potential for face mask use by the general public to curtail the covid-19 pandemic dispersion and exposure to a cough-generated aerosol in a simulated medical examination room a cough aerosol simulator for the study of disease transmission by human cough-generated aerosols exhaled air dispersion during coughing with and without wearing a surgical or n95 mask the control of air flow during loud soprano singing national institute for occupational safety and health. teb-apr-stp-0059: determination of particulate filter efficiency level for n95 series filters against solid particulates for non-powered a primer on multivariate analysis of variance (manova) for behavioral scientists 7 robustness of anova and manova test procedures handbook of applied multivariate statistics and mathematical modeling 7 -multivariate analysis of variance and covariance information point: wilks' lambda filtration theory for granular beds determining impaction efficiencies of mist collection equipment ullmann's encyclopedia of industrial chemistry masks and coronavirus disease 2019 (covid-19) recommendation regarding the use of cloth face coverings, especially in areas of significant community-based transmission use of cloth face coverings to help slow the spread of covid-19 a modelling framework to assess the likely effectiveness of facemasks in combination with 'lock-down' in managing the covid-19 pandemic key: cord-305419-l68ewxar authors: smart, hiske; opinion, francis byron; darwich, issam; elnawasany, manal aly; kodange, chaitanya title: preventing facial pressure injury for health care providers adhering to covid-19 personal protective equipment requirements date: 2020-06-11 journal: adv skin wound care doi: 10.1097/01.asw.0000669920.94084.c1 sha: doc_id: 305419 cord_uid: l68ewxar objective: to determine if a repurposed silicone-based dressing used underneath a n95 mask is a safe and beneficial option for facial skin injury prevention without compromising the mask’s seal. methods: since february 21, 2020, staff in high risk areas such as the ed and icu of king hamad university hospital have worn n95 masks when doing aerosol-generating procedures to protect against the novel coronavirus 2019. at that time, without education enablers or resources that could be directly translated into practice, the hospital’s pressure injury prevention committee explored and created a stepwise process to protect the skin under these masks. this procedure was developed over time and tested to make sure that it did not interfere with the effectiveness of the n95 mask seal. results: skin protection was achieved by repurposing a readily available silicone border dressing cut into strips. this was tested on 10 volunteer staff members of various skin types and both sexes who became part of this evidence generation project. oxygen saturation values taken before and after the 4-hour wear test confirmed that well-fitted facial protection did not compromise the mask seal, but rather improved it. an added advantage was increased comfort with less friction as self-reported by the staff. an educational enabler to prevent mdrpi from n95 mask wear was an important additional resource for the staff. conclusions: this creative and novel stepwise process of developing a safe skin protection method by which staff could apply a repurposed silicone border dressing beneath an n95 mask was largely effective and aided by the creation of the enabler. the global impact of the novel coronavirus 2019 (covid19) has had severe implications for frontline health care providers (hcps). the safety of hcps requires consistent and adequate use of personal protective equipment (ppe). in particular, the use of facial protective equipment against aerosolized transfer of covid-19 droplets is a key recommendation worldwide. 1 it requires the use of a protective filtering respirator such as a n95 mask, eye protection such as glasses, fitted facial shields, and/or specially designed protective suits. facilities have noted an attendant increase in medical device-related pressure injuries (mdrpi) among frontline hcp wearing facial ppe protection that requires risk mitigation. guidelines are being rapidly developed all over the world to ensure that the best solution for each setting can be implemented. the staff of the king hamad university hospital (khuh) includes many ethnicities and various skin types. as in many other facilities, these hcps have been wearing ppe with n95 masks in high risk areas since february 2020 as protection against covid-19 (first confirmed case, february 21, 2020). 2 early on, the pressure injury prevention and nursing quality committees of the khuh agreed that ppe-related pressure and skin injury protection of all staff fell under their purview. bundled pressure injury prevention interventions 3 such as the intact skin bundle are supported by the best evidence for patient pressure injury prevention; the use of these bundles is well documented in high-risk settings. accordingly, the nursing quality committee advised the pressure injury prevention committee to follow this approach in developing and testing a skin care bundle specifically applicable to the work environment of khuh for those hcps providing acute covid-19 care. a mnemonic-based approach 4 was used to enhance knowledge retention, with a one-word reminder of the importance of self-care: help. this mnemonic was designed to help hcps remember the new rules and procedures that had been implemented in a very short time. this led to the creation of the help enabler, which emphasizes 10 evidence-based points to improve hcp prevention of facial mask injuries ( figure 1 ). the key message is to help yourself first, before helping others. elements such as sufficient hydration 5 and nutrition 6 to support a 4-hour shift, emptying bladders before donning ppe, 7 keeping an eye on the amount of time spent in ppe, 1, 3, 8 good skin hygiene, 9 and the importance of mask leak tests 1 form the basis of this care bundle. additional recommendations include using an acrylate lotion 10 or a protective dressing 11 for facial protection under ppe. because adhesives increase the risk of skin stripping and subsequent skin tear injuries, 12 the use of an atraumatic silicone dressing on the face also was proposed. the pressure injury prevention committee repurposed a readily available dressing for facial pressure injury prevention in the absence of existing evidence. however, the team had to establish that this use would not compromise the n95 seal efficacy and facial skin would remain intact under the dressing. further, because this study had to address skin safety for all staff, skin type variation had to be taken into account; for this, researchers used the fitzpatrick skin type classification. the fitzpatrick skin type classification 13 was developed in the 1980s to measure the impact of sunburn injury on different skin types, and is deemed the criterion standard for skin type classification. the classification comprises six skin types ranging from light skin (type 1, which burns easily and never tans, and type 2, that usually burns and figure 1 . help enabler tans slightly) to olive/medium brown skin (type 3, that initially burns and tans well, and type 4, that usually tans) and finally to dark brown and black skin (types 5 and 6). 13 in this study no hcp with type 1 (extremely light caucasian skin) could be included because there are no nursing staff with that skin type at khuh. this prospective observational cohort study was divided into five steps to establish the appropriateness, efficacy, and safety of each phase. it involved wear-time tests culminating in a final 4-hour crossover experiment. developing the protocol and assembling key departments (nursing, infection control, quality assurance representatives, covid-19 hospital committee) to discuss and approve the proposed skin protection protocol took time; this practice innovation began in march 2020 and was tested in the first 2 weeks of april 2020. institutional review board approval was received because the study involved human participants (reference #20-334). because n95 mask wear is mandatory for covid-19 frontline care provider safety, any facial injuries sustained as a result were not deemed an ethical objection for this experiment. essentially, facial injury was the real-life risk this study tried to mitigate. participants signed an informed consent form to take part in the study and for all photos to be used in subsequent publication with no parts of faces obscured. phase 1. ascertain how to repurpose an atraumatic silicone border dressing (mepilex border sacrum, mölnlycke, norcross, georgia) to cover bony facial prominences without compromising the n95 particulate respirator and surgical mask fit (3m type 1860, minneapolis, minnesota) using only one small dressing per day for the duration of a shift (this allows for the most stringent interpretation of infection control practice). phase 2. fit eight participating staff members with various skin types who volunteered for this project with a protective dressing layer. have infection control staff conduct a n95 fit test according to international best practice. phase 3. continue the use of facial protection for 1 hour after the fit test and examine the condition of the facial skin thereafter. phase 4. determine the efficacy and stability of the dressing underneath a fitted n95 mask after 3 hours and examine facial quality thereafter. (only one participant was included in this phase.) phase 5. compare the difference in facial skin quality and metabolic oxygen saturation values (spo 2 ) as determined by a fingertip applied pulse oximeter with and without facial protection applied in a 4-hour shift period on a normal working day among five participants. this test took place over 2 days in a work environment not actively caring for patients who were covid-19 positive. facial skin evaluation and spo 2 values before and after removal of the mask were repeated. during the study development period (march 2020), relevant guidelines on this topic were scarce. a process of creative problem solving was therefore followed to determine how facial skin injuries in health care providers in the authors' setting could be addressed in the most efficient and cost-effective manner. because staff would have to remove the protective dressing at the end of each shift, it was clear that any product with aggressive adhesion would soon strip the outer layer of the skin 12 and that the additional pressure exerted by the n95 mask on the barrier would enhance adhesion. pain on removal and skin injury over time would be likely. 12 therefore, an atraumatic dressing was required. at the khuh, an atraumatic silicone sacrum dressing is routinely used for pressure injury prevention of high-risk hospitalized patients 11 as part of the standard pressure injury prevention skin care bundle. 3 it is the only type of atraumatic silicone dressing available in the authors' setting; each dressing is similar in cost to a take-away coffee. the aim was to repurpose a single 10 x 10 dressing for frontline hcps during each shift to provide facial protection and limit cost for the institution. earlier testing revealed that the dressing edge could catch on to the n95 mask sponge and create an interlocking mechanism to position two offloading areas next to each other rather than on top of each other. this enhances the distribution of pressure over a larger area and prevents additional pressure on any given area by stacking multiple layers. the rationale was that if pressure was equally distributed over the nose with the interlocking fit of the n95 mask sponge on the dressing edge, the cheekbones were only in need of friction control (maintaining mask integrity without adding bulk). further, this placement was successful even with some small facial hair stubble present on the cheeks and chins of male staff members; the dressing sat snugly despite being applied over chin hair, and removal was painless. there was a square piece left for the forehead that could be used as pressure relief underneath protective eye shields or goggles resting on the forehead. two additional small pieces remained to offset the pressure from the elastic band of the n95 mask touching the sides of the face close to the ears ( figure 3 ). to ensure each person uses the correct n95 mask size, a standardized initial fit test in accordance with international guidelines is required. the khuh infection control team conducted the leak tests in late january and early february using the hood method. 14, 15 the method involves placing a see-through polymer hood with an applicator window in front of the face and a tight-fitting seal around the hcp's neck. to determine a participant's individual sensitivity, a distinct smell (denatonium benzoate) is serially sprayed into the hood to determine at what point (after how many sprays) a smell is observed. next, the hood is removed, and the participant is instructed to rinse his/her mouth and wait 15 minutes. then a n95 mask is donned and the procedure repeated. the mask fit is deemed effective when no smell is observed if half of the sprays required during the sensitivity test are applied. the infection control team documents each time a person passes the fit test (smell only observed after more than the threshold number of sprays). a person who fails the fit test is fitted with a different sized mask and the spray test is repeated until passing; however, it only needs to be completed once per person. 14 leak testing is the responsibility of each staff member and involves positioning the n95 mask on the head and fitting it around the nose by applying two fingers on either side of the nose and pressing the mask tight while breathing in. next, hands are placed over the middle of the mask (without adjusting its position) and the staff member exhales sharply. if air escapes from the sides of the mask, the mask should be adjusted and all of the steps repeated until exhaled air exits only through the middle of the mask and no leaks occur on inhalation or exhalation. this process is repeated twice every single time an n95 mask is applied. 16 where limited reuse of n95 masks is practiced, it is done in accordance with the khuh infection control protocols governing mask functionality/ cross-contamination prevention and not to exceed five uses per person. 17 eight volunteer staff members (four males and four females) with various fitzpatrick skin types were included in this phase. two work in the ed, two in icu, one in a male surgical ward, and three in the wound care unit. all participants had previously passed the official n95 fit test. all staff previously wore n95 masks without skin protection. participants applied the repurposed, separated atraumatic dressing segments on their own faces after an initial demonstration. the application took less than 5 minutes, inclusive of the time required to cut up the dressing. they then donned n95 masks and conducted manual leak tests. 16 all eight participants achieved the same mask positioning with the applied dressing beneath their mask as without. infection control then conducted another fit test. staff all reported only a slight smell after 4 sprays, and this was consistent up to 6 sprays. therefore, 95% blockage was achieved with this mask configuration. this outcome was certified by infection control as conforming to international standards-that is, all eight participants passed the fit test while using the atraumatic dressing. staff were instructed to maintain that exact ppe configuration for the next hour without repositioning or removal. once the hour was over, they had to remove the mask and the facial dressing themselves, take a photograph of their face, and present it to the research team. all photos were time stamped to ensure masks were not removed before the period was completed. staff also had to report on this experience compared with their previous experience/original fit tests. there were no negative comments from the staff, despite application over hair in some men. in fact, some staff noticed that the nose dressing prevented mask movement they had previously experienced when looking up or down. this interlock also helped to minimize the perpendicular pressure of the n95 mask exerted on the nasal crest; all participants commented on improved nose comfort, as well as the absence of facial irritation caused by the direct contact of mask fibers to the cheeks. comfort underneath the chin was also noted; itching and moisture vapor build-up appeared to be absent in this configuration. when asked if the dressing was worth the application time, the answer was a unanimous yes. the immediate facial condition of all staff with protective dressings can be seen in figure 4 . those with fitzpatrick skin types 2 and 3 (lighter skin tone, n = 2) showed a bit of visible erythema over the bony cheek area. no marked erythema or pressure was visible on any of the other participants (n = 6). no erythema or pressure marks were visible on any staff member on the sides of their faces where the top applied elastic band of the n95 mask is placed. one staff member with fitzpatrick type 2 skin was willing to test the mask without facial protection for 2 hours on a different day, before the leak tests were conducted. researchers believed that this skin type would show visible injury most quickly. the next day, this participant wore the mask for 3 hours with facial protection applied. the results of this trial are depicted in figure 5 . mask wear without skin protection resulted in friction and chafing with erythema visible over and along the bony prominences of the cheekbones. a blanchable area was visible on the bridge of the nose after the 2-hour test. this finding is consistent with extant literature reporting that pressure injury can occur in as little as 2 hours. 8, 11 after testing with facial protection, slight erythema was again present over the bony prominences of the check bones with only a little redness on the left lateral side of the nose. however, these changes were much less noticeable than before, without additional friction or chafing areas present, signifying good mask fit with minimal movement during the 3-hour period. all erythema visibly diminished after 1 hour. this experimental test took place over 2 consecutive days with five volunteer staff members (one male, four female) with skin types from fair to dark brown on the fitzpatrick scale. researchers theorized that skin damage or injury would be easier to observe in females, who have thinner skin than males. 18 if female skin was protected by the selected method, it could reasonably be assumed that males would be protected as well. female nurses also outnumber male nurses in this setting and are therefore more likely to participate in direct care and require protection. on the first day of this phase, the n95 mask was worn for 4 hours (no eating, drinking, or bathroom breaks allowed) with protection prepared and applied by each participant. comfort was self-assessed by participants. at the end of the 4 hours, three participants felt that they could have continued for an hour or two more. slight sweating was present, with indentations visible on all of the participants' faces. only one (fitzpatrick type 2) presented with slight erythema; the least damage was visible on the darkest skin. pulse oximetry saturation levels of each participant were also taken before and after the test. all participants lost between 1% and 3% spo 2 in this test, with a mean loss of 2% metabolic spo 2 (table 1 ). this is in line with extant studies on n95 mask use that confirms overall oxygen intake is diminished during wear, even with a perfectly fitting mask. 19, 20 on the next day, the n95 mask was worn without any protection ( table 2) . each participant positioned their own mask and it was again worn for 4 hours without any eating, drinking, or bathroom breaks. all four female participants battled with discomfort; pruritus on the mask edges was noted after the first hour. all participants reported that they were relieved when the mask could be removed; none wished to continue wearing the mask for a longer time. less moisture build-up was visible compared with the day before, but skin indentations were present on all five faces. the lighter skin tones appeared to have more pressure-related impact than those with darker skin tones. all four females had various levels of skin erythema, with the fair skin most damaged of all. the participant with the darkest skin had the least visible damage; one small darkened area was visible that fully recovered in 1 hour. of the female participants, three continued to have signs of indentation and erythema an hour after the test, with the fair-skinned participant least recovered compared with results from the day before. with regards to metabolic spo 2 on the second day, three participants retained the exact same starting value, and one gained 1%. the remaining participant had a 2% spo 2 loss. the mean loss was 0.2% metabolic spo 2 . figure 6 depicts spo 2 readings taken from the same participant before and after both 4-hour tests. this article describes a holistic approach to facial skin injury prevention for hcps to "help" staff to embrace a longer periods of ppe use (with each participant serving as their own control) produced a distinct difference between mask wear with and without protection, including improved facial condition and comfort without compromising mask seal. three possible mechanisms of injury were identified in this experiment. the first was associated with direct high pressure causing skin indentations (ie, from mask edges, nose fitting device, and straps); the second a diffuse erythema in a linear pattern associated with lower pressure with or without friction (ie, mask edges moving). both were more pronounced when no facial protection was present. the third was related to sweating: slight localized sweating underneath the mask was more pronounced when skin protection was used, attributable to the better integrity of the acquired seal. associated moisture build-up from sweat is therefore a risk with this ppe configuration; accordingly, the use of a skin-protective acrylate 10 followed by meticulous facial care 9 is recommended for off-duty hcps. all participants cut up the dressing into segments with ease and could easily apply the dressing to their faces with the use of a mirror. after donning this protective layer, the integrity of the n95 mask was also easily established, with all staff passing both the leak and the fit tests. the most crucial safety consideration for frontline providers during the pandemic lies in the order of ppe removal; it must be doffed in the exact reverse order it was donned. 1 bathroom and eating breaks cannot be factored into shifts because the proper reverse removal of layers of ppe takes more time than application to prevent contamination and risk to others in the facility. 1, 7 all body ppe must be removed first, followed by a thorough handwashing, 21 after which the n95 masks are removed by touching only the elastic bands, 1 and the handwashing procedure is repeated before the facial protective dressings can be removed. essentially, staff can greatly increase the risk for covid-19 self-contamination if they touch their faces before all contaminated ppe is safely removed. 1 this stringent ppe process requires heightened staff awareness of this vital safety precaution, reinforcing the help enabler's focus on adequate nutrition and hydration in off duty times and recommendations to limit excessive amounts of fluids immediately before a shift. given these self-care strategies, a 4-hour fasting period is feasible. the key is to plan and shift nutrition and hydration activities to directly after and/or no less than an hour before a shift. staff with medical conditions who cannot adhere to a 4-hour fasting or bathroom break-free shift should be deemed at high risk for contagion not only to themselves, but also others using the same facilities. at least one facility has already trialed this approach with success. for each 4-hour shift of frontline staff in full ppe in wuhan, china, 7 touching masks, eating, drinking, and bathroom breaks were prohibited. this simple process ensured zero staff contracted covid-19. 7 their experience provided the rationale for the 4-hour wear test conducted in this study. a different cross-sectional study 22 (n = 4,306) from china on facial injuries sustained by hcps when using ppe also identified this 4-hour cut-off time. researchers found a statistically significant difference in the number of injuries sustained if hcps exceeded this time frame in ppe. 22 skin protection under masks is therefore a necessity because shift lengths can be unpredictable based on ppe supplies 23 but also because facial injuries have been noted in shorter shift periods 22 and within 2 hours in this study. it is of vital importance that hours of ppe wear (regardless of facial protection applied) be documented 3 to prevent prolonged exposure, excessive moisture build-up, and skin breakdown. based on the experience of aggressive frontline covid-19 care in wuhan, 7, 22 it is recommended that each 8-hour shift be divided between two teams where one team does the work requiring n95 mask wear (in the dirty/infected area) while the rest works in the clean area. after 4 hours inside without eating, drinking, or a bathroom break in full ppe, the two teams switch. this prevents exhaustion, mask hypoxia, 19 and protects the skin of hcps 7,22 with minimal impact on staffing. the most interesting finding of this study was the drop in participant spo 2 values by 2% on average when using the protective dressing underneath the n95 mask. this corresponds with tight-fitting mask wear studies conducted during flu outbreaks. 19, 20 it is possible that the protective dressing increases the mask's seal stability while mitigating pressure-related skin damage. critically, extended periods of n95 mask wear may be related to mask-induced hypoxia in hcps; 19, 20 hypoxia is an established major risk factor for pressure-related skin breakdown. 3 mitigation of this concern can be achieved by the split-shift approach previously described. 7,22 the reduced spo 2 finding was not the case with n95 mask use alone. this may indicate that despite passing the fit and leak tests, the discomfort from mask wear results in participants occasionally moving their faces to relieve pressure and facial irritation, which could result in small leaks. the participant with type 2 skin most likely had a leak present during the test where the protective layer was not applied that was sustained during the test by mouth, chin, and facial movements. this participant had a 1% increase in spo 2 and the most pronounced skin damage present after the test. mask discomfort may therefore add to the iatrogenic risk of contracting covid-19 infection. the same risk applies to staff with any facial injury resulting in a skin breach, because pain may compromise proper n95 mask seal. adding repeated pressure to an existing facial injury has the potential to exacerbate minor injuries and lead to deeper dermal injuries; this is why patients are carefully positioned to displace pressure to other body parts once a stage 1 pressure injury is present. 3 this small sample was recruited to serve in a pilot project to determine if the application of a facial protective layer could mitigate facial injury risk among n95 mask wearers. more research using different border dressings would be beneficial to expand the evidence base on this topic and give providers more options. the staff at khuh is also mainly of west and east asian descent, hence the lack of a nurse with a fitzpatrick skin type 1. this is a major limitation because this skin type is usually the most sensitive to injury and skin insults. further, although the fitzpatrick scale is the criterion standard for sun-related skin damage, it may not fully predict pressure and shear damage on skin because deeper injuries may not be immediately visible. further testing in institutions that have hcps with fitzpatrick type 1 skin is warranted. further work is also needed on n95 mask wear and the impact of reduced spo 2 on fatigue, headache, and concentration to determine the optimal safety balance between skin risk, metabolic stress, and personal protection. early on in the covid-19 health crisis, the need to protect the skin of hcps was prioritized at the khuh. at that time, there were no educational resources available to guide practice. (some enablers have since been released, beginning in april 2020. 24, 25 ) the creative stepwise process of skin protection described in this article was developed with readily available products and participants who volunteered to help develop a safe solution for skin injury prevention. at roughly the same cost as a daily take-away coffee, a repurposed atraumatic silicone border dressing can support skin health underneath a tight-fitting mask. by cutting it into segments and carefully applying it without creases over the nose, cheekbones, and sides of the face, hcps can achieve pressure redistribution and facial skin protection. this method does not appear to interfere with n95 mask integrity and in fact may provide additional leak protection by securing the mask more firmly in position, ultimately protecting against accidental viral transfer to the face. 1 accordingly, these authors recommend that hcps add an atraumatic silicone border dressing as a safe and beneficial option to protect facial skin under ppe. however, no dressing by itself (regardless of testing) can provide complete care of facial skin underneath n95 masks. it is critical that hcps implement a comprehensive skin care approach. frontline staff who "help" themselves by taking responsibility for their own skin care, who are well prepared, well rested, fed, and hydrated can more safely take care of others. it is the authors' hope that this creative evidence-based clinical facial protection solution and help enabler will be of assistance to their global colleagues in the fight against covid-19. • supplemental table. application of the protective dressing step 1: hand preparation handwashing according to correct technique, 40 to 60 seconds step 2: prepare dressing by cutting it in required segments 1-7 step 3: apply dressing segments in this order: 1) on the nose 2, 3) sides of face 4) under chin step 4: apply the rest of the dressing on areas in need of added relief: 5) forehead (thicker or thinner as needed) 6, 7) sides of ears step 5: apply n95 mask and other protective equipment over dressing step 6: removal handwashing for 40 to 60 seconds remove the mask using elastics only and discard properly wash hands again, 40 to 60 seconds remove all protective dressings in reverse order (7 through 1) wash hands and face and apply moisturizer on both follow the help enabler for total self-and skincare rational use of personal protective equipment (ppe) for coronavirus disease (covid-19). interim guidance public awareness campaign to combat coronavirus. coronavirus (covid 19) latest updates. 2020. www.moh.gov.bh/?lang=en. last accessed european pressure ulcer advisory panel, national pressure injury advisory panel, pan pacific pressure injury advisory panel. prevention and treatment of pressure ulcers/injuries: clinical practice guideline the impact of a mnemonic acronym on learning and performing a procedural task and its resilience toward interruptions facial skin mapping: from single point bio-instrumental evaluation to continuous visualization of skin hydration, barrier function, skin surface ph, and sebum in different ethnic skin types nutrition and skin ulcers protection of medical team in wuhan using multi-layer foam dressing to prevent pressure injury in a long-term care setting enhancing skin health: by oral administration of natural compounds and minerals with implications to the dermal microbiome impact of water exposure on skin barrier permeability and ultrastructure a randomized controlled trial of the clinical effectiveness of multi-layer silicone foam dressings for the prevention of pressure injuries in high-risk aged care residents: the border iii trial skin tears and risk factors assessment: a systematic review on evidence-based medicine the validity and practicality of sun-reactive skin types i through vi particle size-selective assessment of protection of european standard ffp respirators and surgical masks against particles-tested with human subjects kansas department of health and environment. fit testing procedures for n95 respirators (using 3m ft-30, bitter fit test equipment) singapore general hospital. n95 3m mask fit: how to wear and remove unmc heroes, n95 respirator limited reuse -health care professionals providing clinical care male versus female skin: what dermatologists and cosmeticians should know preliminary report on surgical mask induced deoxygenation during major surgery respiratory consequences of n95-type mask usage in pregnant healthcare workers-a controlled clinical study van den wymelenberg k. 2019 novel coronavirus (covid-19) pandemic: built environment considerations to reduce transmission the prevalence, characteristics, and prevention status of skin injury caused by personal protective equipment among medical staff in fighting covid-19: a multicenter, cross-sectional study rational use of personal protective equipment for coronavirus disease (covid-19) and considerations during severe shortage. interim guidance prevention and management of skin damage related to personal protective equipment (ppe) national pressure injury advisory panel. npiap position statements on preventing injury with n95 masks key: cord-311795-kvv3fx2n authors: barratt, ruth; shaban, ramon z.; gilbert, gwendoline l. title: clinician perceptions of respiratory infection risk; a rationale for research into mask use in routine practice date: 2019-08-31 journal: infection, disease & health doi: 10.1016/j.idh.2019.01.003 sha: doc_id: 311795 cord_uid: kvv3fx2n abstract outbreaks of emerging and re-emerging infectious diseases are global threats to society. planning for, and responses to, such events must include healthcare and other measures based on current evidence. an important area of infection prevention and control (ipc) is the optimal use of personal protective equipment (ppe) by healthcare workers (hcws), including masks for protection against respiratory pathogens. appropriate mask use during routine care is a forerunner to best practice in the event of an outbreak. however, little is known about the influences on decisions and behaviours of hcws with respect to protective mask use when providing routine care. in this paper we argue that there is a need for more research to provide a better understanding of the decision-making and risk-taking behaviours of hcws in respect of their use of masks for infectious disease prevention. our argument is based on the ongoing threat of emerging infectious diseases; a need to strengthen workforce capability, capacity and education; the financial costs of healthcare and outbreaks; and the importance of social responsibility and supportive legislation in planning for global security. future research should examine hcws' practices and constructs of risk to provide new information to inform policy and pandemic planning. abstract outbreaks of emerging and re-emerging infectious diseases are global threats to society. planning for, and responses to, such events must include healthcare and other measures based on current evidence. an important area of infection prevention and control (ipc) is the optimal use of personal protective equipment (ppe) by healthcare workers (hcws), including masks for protection against respiratory pathogens. appropriate mask use during routine care is a forerunner to best practice in the event of an outbreak. however, little is known about the influences on decisions and behaviours of hcws with respect to protective mask use when providing routine care. in this paper we argue that there is a need for more research to provide a better understanding of the decision-making and risk-taking behaviours of hcws in respect of their use of masks for infectious disease prevention. our argument is based on the ongoing threat of emerging infectious diseases; a need to strengthen workforce capability, capacity and education; the financial costs of healthcare and outbreaks; and the importance of social responsibility and supportive legislation in planning for global security. future research should examine hcws' practices and constructs of risk to provide new information to inform policy and pandemic planning. preventing the transmission of infectious diseases in healthcare settings, and in society more broadly, is a core goal of contemporary public health and infection prevention and control (ipc). in recent years outbreaks of emerging infectious diseases caused by respiratory viruses have drawn considerable global attention, in particular severe acute respiratory syndrome (sars), middle east respiratory syndrome (mers) and pandemic influenza a, h1n1 2009 (table 1) . consequently, global and national planning for pandemic diseases is grounded in the expectation that a novel respiratory infection is most likely to be responsible for the next pandemic or infectious disease emergency [1] . respiratory infectious diseases are transmitted via contact, droplet and/or airborne modes, necessitating healthcare worker (hcw) use of surgical masks or respirators and other personal protective equipment (ppe) together with appropriate hand hygiene. hospital-based transmission of respiratory infectious diseases of high consequence, such as influenza, can be minimised by limiting the part hcws play as vectors or victims of disease. hcws may continue to work with mild respiratory illness (presenteeism), which can be serious or life-threatening if transmitted to vulnerable patients, but they also may suffer serious effects from occupationally-acquired respiratory infections, leading to increased staff absenteeism, which will compromise patient care during epidemics. while policies and protocols for optimal use of ppe and other transmission-based precautions exist in the majority of healthcare facilities, hcw compliance with them is typically limited, particularly in non-outbreak situations or in the early stages before an outbreak is recognised [2, 3] . in particular, hcws' use of protective masks when caring for patients with respiratory infections is an important and well-documented ipc measure [4] . yet hcw use of protective masks, and ppe in general, during routine care is often suboptimal and can result in healthcare-associated acquisition of infection [5] (table 2) . while hcw compliance with the use of protective masks during infectious disease outbreaks has been well reported [6] , there has been limited examination of hcw behaviours with respect to protective mask use during routine clinical care [3] . consistent routine use of protective masks, based on relevant clinical indications, is important in preventing or delaying transmission from an unrecognised initial/index case [7] . the appropriate use of ppe, including respiratory protection, and hand hygiene in routine care is critical to minimising pathogen transmission to staff and other patients; sub-optimal use exposes both hcws and patients to infection. compliance of hcws with wearing a protective mask may be related to their perception of risk and their risk-taking behaviours. the existing ipc literature primarily focuses on this topic in the context of sars or other pandemic respiratory diseases, with few papers investigating risk constructs for healthcare workers in routine care. the first and classic response to suboptimal behaviour is educative, with the provision of in-service and other training. we argue that the factors that lead to suboptimal use go far beyond knowledge and education, as well a subsequent national outbreak resulted in 186 healthcare associated cases within the first month with over one fifth of these cases being hcws. one reason for so many hais has been attributed to sub-optimal use of routine protective equipment by hcws and the potential for infected hcws to act as vectors of infection [13] . documented in other behaviours such as hand hygiene [8] . interventions, and the research efforts used to generate evidence to support them, must take account of individuals' constructs and perceptions of risk and risk-taking behaviour. these perceptions are necessarily heterogeneous and vary between individuals and clinical settings. therefore, an understanding of the perceptions and behaviours regarding ppe use in different contexts is needed to inform successful behaviour change interventions [9] . the importance and urgency of addressing suboptimal mask use by hcws is, in our view, based on a range of interconnected reasons all of which are critical to global health and security. these are as follows: the continuing burden of emerging infectious diseases for many centuries, since the age of the plague and smallpox epidemics to the 20th century outbreak of hiv/ aids, human infectious diseases of high consequence have presented a significant global public health challenge. these pandemics have resulted in deaths and disability of millions of people across the world, as well as causing social and economic disruption. despite improvements in communicable disease prevention and control, including effective sanitation, vector control, vaccines, and the international health regulations developed by the world health organization (who) [10] , the new, emerging infectious diseases continue to threaten the well-being and economic stability of society and impose a significant burden on healthcare. although some infectious diseases, such as plague or smallpox, no longer present an active global pandemic threat, this century has seen both new and re-emerging infectious diseases give rise to widespread outbreaks. of particular current concern is re-assortment of rna in viruses such as influenza a which contributes to emerging pandemic influenza strains [11] . furthermore, several zoonotic viral diseases that have infected humans through animal-to-human contact have also demonstrated human-to-human transmission, such as nipah virus [12] . antecedents for the increasing burden of infectious diseases include a global population boom, changes in the use of land and environment, loss of wild life habitat, increased contact between wild and domestic animals and humans, the expansion in travel, an ageing population and developments in medical interventions. the latter two have led to an increase in the number of immunecompromised people who are susceptible to significant disease from emerging infections. many of these people attend, or are frequent inpatients of, healthcare facilities and therefore are at risk of healthcare-associated infections (hais). cheaper, easier and faster modes of travel, particularly by air, have enabled emerging infectious diseases to disperse more widely in short periods of time, than ever before. a clear example of this was sars, which spread from one "super-spreader" in a hotel in hong kong to numerous other countries via international guests who were infected, by contact, while staying in the same hotel [13] . similarly a large outbreak of mers involving 186 cases resulted from a single traveller returning to south korea from the middle east and attending several hospital emergency departments after he became unwell [14] . the number of active outbreaks that are present around the world will vary on any given day; however at time of writing there were traveller alert notices for at least twelve different infectious diseases in more than 50 countries [15] and, on average, 90 global infectious diseases emergencies are notified via the who each day [16] . the use of protective respiratory masks has a human resource impact in healthcare organisations. clinicians are at a higher risk of acquiring influenza and other respiratory diseases than adults working in non-healthcare settings [17] . sub-optimal protective mask use can increase this risk, which is exacerbated during high-risk periods such as the winter respiratory virus season. staff illness from respiratory infections has a direct impact on the workforce resulting in loss of productivity and associated economic burden within the healthcare setting, particularly with influenza [18] . other respiratory viral diseases, such as the common cold, also contribute to a reduced work output [19e21] . productivity is affected if workers take leave to care for family members who are ill or children, because schools have been closed. although annual influenza vaccination is widely promoted as a means to reduce staff illness, average uptake by hcws is poor, unless is it mandatory. seasonal vaccine efficacy varies from year to year because of variable matching between vaccine and circulating strains, but is generally less than 50e60% [22] . even when hcw flu vaccine uptake is high the risk remains, because of vaccine mismatch with circulating strain, limited vaccine efficacy and/or mild or subclinical (but transmissible) infection in vaccinated subjects [23] . consequently, hcws should still use respiratory protection when caring for patients with respiratory symptoms and/or patients at high risk of infection during outbreaks or high levels of respiratory infections in the community. not wearing a protective mask increases the risk of occupationally-acquired respiratory disease. hcw absenteeism due to influenza increases on average by two days per hcw, both during pandemic and a seasonal virus outbreaks [24] . ip et al. [25] examined overall sickness absences including sick leave due to acute respiratory infection (ari) for four distinct influenza periods between 2004 and including the 2009 influenza a(h1n1)pdm09 pandemic in hong kong. results showed that the daily hcw absenteeism rate for ari increased from the pre-pandemic in september 2018 a uk healthcare worker contracted monkeypox after caring for a patient with the disease prior to diagnosis. in a eurosurveillance report (add in ref) about the case, public health officials said that some hcws had been exposed as they were not wearing optimal personal protective equipment. baseline by 26.5% and 90.9% during the epidemic and pandemic periods respectively [24] . similarly in canada, researchers demonstrated a significant increase in the rate of sick hours between the pre-influenza and 2012/2013 influenza period with only 14% of staff having zero sick hours productivity losses related to the common cold [26] . a study examining the effect of influenza vaccination on emergency department workers' absentee rates reported that 30% of vaccinated and 55% of non-vaccinated workers required sick leave for influenza-like illness [27] , although significant absenteeism during the h1n1 influenza pandemic was not noted in the australian emergency workforce [28] . staff illness compromises the quality and safety of patient care by loss of continuity of care through the requirement to employ agency staff in place of regular staff, who may be unfamiliar with the specialism of the clinical setting [28] . staff absenteeism during outbreaks of emerging or high consequence infectious diseases, may also be due to hcws fear of acquiring the infection [29] . similarly, presenteeism, or coming to work when ill, also results in a loss of productivity due to staff not working at full capacity [30] . the health and safety of other staff are put at risk by hcws who continue to work while ill, while patient safety may be compromised through impaired clinical judgement. in a study undertaken in a children's hospital in philadelphia, 299 (55%) of medical staff who were surveyed, reported that they would work with significant respiratory symptoms, despite acknowledging the infection risk to their co-workers and patients [31] . in another study over 40% of us hcws who were surveyed worked with symptoms of influenza-like illness [32] . whilst it is important to avoid presenteeism, it may be occasionally unavoidable e.g. because of significant or specialised staff shortages. if so, the risk may be mitigated by appropriate mask use. the hcws work capability may also be impaired by any physical and psychological consequences of wearing a mask, such as claustrophobia, respiratory distress, discomfort and skin irritation. the financial costs to society for respiratory infectious diseases can be significant. a us study estimated the annual economic burden of influenza, in 2003, to be around us$90 billion [31] , while lost productivity due to influenza in france and germany was estimated at us$10e15 billion per year [33] . sub-optimal mask use is likely to be associated with an increase in financial costs for individuals, the healthcare system and subsequently the wider society. although existing research has not examined the direct costs of not wearing a protective mask, van buynder et al. (2015) estimated the financial cost of hcws absenteeism due to influenza-like-illness to be greater than can$1 million during the 2012/2013 winter season in a health district in british columbia [26] . in addition, there are sick leave payments for staff and the costs incurred to replace them with casual staff. workers compensation fees may be driven up by hcws who take risks by not wearing masks. furthermore, there are significant monetary costs associated with patients acquiring a healthcare associated respiratory infection. the probability of a patient acquiring an influenza-like-illness increases when exposed to an infectious hcw, with one study reporting a relative risk of 5.48 when compared to no documented exposure [34] . expenses for a hai include the overall cost of care for any additional inpatient bed days as a result of the infection, antiviral medication, other supportive therapy, radiology, laboratory and direct costs associated with the use of isolation and ppe measures. a korean study reported an average medical cost for a patient hospitalised with influenza in 2013/2014 was us$ 3104.3 ae 4638.1 [35] . when a higher level of ipc measures is required e.g. mers or other emerging infectious disease, these costs can be excessive. veater et al. (2017) calculated an additional cost of 119 pounds sterling per person per day, mainly due to staff time and ppe costs [36] . third, sub-optimal mask use is associated with reductions in cost effectiveness of training methods in the use of ppe. effective training in ppe use is resource intensive and thus expensive to execute, whether delivered as demonstration learning by experts or technology-based education. inadequate training in ppe protocols is cited as one of the causes for poor compliance with ppe [37] . these findings question the cost-effectiveness of current training methods. there is also a financial cost attached to the incorrect choice or unnecessary use of a mask, particularly in the case of the more expensive particulate respirator mask, or during a global outbreak event where stocks may be limited. the knowledge and skills of hcws are factors that affect protective mask use, therefore investigating how knowledge and cognition impacts on the hcw decision-making for mask use can inform the delivery of education and how policies are implemented. some of the aspects of knowledge related to mask use that may influence hcw behaviour include the source of knowledge, the indications for mask use, which type of mask to choose, how the mask functions to provide protection and how to put on and remove the mask safely. in the context of an emerging infection and limited available information, personal experience can influence hcws' perceptions of risk and behaviours related to protective mask use [38, 39] . in contrast, a study undertaken in an outpatient paediatric setting, demonstrated that the use of ppe was not influenced by infectious risk perception [40] . prior education and training will provide some of the essential information and skills required for optimal mask use but, in practice, routine training in the use of ppe is often cursory or non-existent. in a survey of healthcare workers in the us, 43% of doctors reported having received ppe training only as students (including clinical rotations) or not at all (c.f. 8% of nurses) [41] . despite prior education, hcws may not apply their knowledge to the workplace [42] . the method of training is therefore an important consideration for effective retention of knowledge and skills over time. several studies argue for improving the evaluation and training of hcws using ppe for infectious diseases and examining the effectiveness of various teaching approaches [43, 44] . the recent ebola virus disease (evd) outbreak instigated intensive ppe training around the world, with a focus on donning and doffing protocols to maximise hcw safety. unsafe use of ppe has been blamed for some hcws becoming infected with evd or sars; subsequently several research studies have reviewed the effectiveness of different training techniques for the safe donning and doffing of ppe [45] . these have included interactive online courses, and classroom teaching that incorporates fluorescent dye or harmless bacteriophages as surrogate markers of contamination [46] . video-reflexive ethnography (vre) has been used as an interventional methodology to improve ipc practices [47] . this method allows the hcw to view video footage of themselves making decisions around and subsequently using protective masks in every-day complex work. the clinicians can then reflect on their behaviour and suggest ways in which their own and colleagues' mask use can be optimised. although the techniques taught for donning and doffing protective masks as part of routine ppe are generally heterogeneous around the world, there are variations in mask design which may affect skills. there is also a lack of standardisation between and within institutions as to which clinical indications warrant a n95 or surgical mask. within society in general, individuals are not only motivated to protect themselves from infectious disease but often demonstrate a moral responsibility to protect others if they themselves are infectious [48] . during periods of high-risk for respiratory infectious disease, such as the annual influenza season or a novel influenza pandemic, health departments have, and may, encourage or mandate the use of a protective respiratory mask by the general public to minimise the transmission from symptomatic people to others [49] . in healthcare facility waiting rooms it is recommended that symptomatic patients be given a respiratory mask to wear to protect others as part of respiratory hygiene [49] . this social behaviour may alter the perception of risk for staff towards mask use in two ways, particularly in the emergency department. firstly, hcws may take a view that it is the patient's, not their own, responsibility to abide by these infection prevention measures and purposefully choose not to wear a mask on the basis of responsibility. secondly, they may not perceive a risk of becoming infected if a patient is wearing a mask and so will not use one. there are several risks for hcws adopting this behaviour. the patient may not wear the mask correctly or remove it at any time, especially if they are kept waiting for long periods, thus exposing other patients and hcws. additionally, the patient may not be able to tolerate a mask for long if unwell and will then remove it. clinical examination may put the hcw at higher risk of exposure, even if the patient is wearing the mask correctly when they enter the room or cubicle and certain procedures, such as taking a swab for influenza testing, collection of an induced sputum specimen or intubation, require removal of the patient's mask. if an hcw fails to adequately explain why they are wearing a mask it can erect a social barrier between the hcw and patient. patients may feel stigmatised if staff wear a mask to care for them [50] while staff may feel that wearing a mask in the ed can inhibit empathy and rapport with a sick patient [51] . hcws working in paediatric units have expressed concern that ppe may frighten their patients [52] . social interactions within the workplace can influence the health-related behaviour of workers. the safety climate and group norms at hospital unit level have been shown to influence the risk-taking behaviour associated with facial protective equipment [53] . the use of protective masks in the healthcare setting is governed locally by policies in health and safety and ipc. as indicated earlier, adherence to such policies and guidelines is often poor. similar to other types of ppe and ipc measures, there is no strong culture of enforcement of policy relating to protective masks in the healthcare setting. this raises questions about the efficacy of mask policies, their awareness by hcws and how they are judged by clinical staff. in some countries, state-wide legislation mandates the use of a protective mask for various categories of clinical staff during the annual influenza season, if they have not received the influenza vaccination [49] . this enforced measure has been resisted by some clinical staff because of its impact on personal choice [54] and by others as illogical when considering the risk from all respiratory pathogens [55] . although many countries provide national occupational safety and health policy direction, few enforce protective mask use in healthcare settings. nevertheless, sub-optimal mask use reinforces poor behaviour in the workplace and contravenes workforce health and safety responsibilities of employees [56] . the behaviours of hcws towards protective mask use can affect the progression of a respiratory infectious disease outbreak and, if inappropriate, facilitate a pandemic. the consequences of a pandemic on a global scale are significant, with substantial negative societal effects. ease of access to international travel has been a significant factor in the worldwide spread of recent pandemics such as pandemic influenza a h1n1 2009 , sars and mers, therefore international travel and trade are often restricted [57] . personal freedom of movement is also affected by public health quarantine measures and the prohibition of public gatherings. education is disrupted through school closures which results in parents taking time off work as a consequence. in addition to the consequences described above, the provision of healthcare to the general population can be disrupted. in 2009, the influenza a h1n1 2009 pandemic impacted severely on the normal functioning of emergency departments in australia [58] . more than three times the number of patients were seen, most with non-serious influenza symptoms. staff reported that heavy workloads, lack of infection control facilities and distraction from their core business compromised the care of non-flu patients. large numbers of patients requiring care will lead to bed shortages and hospital admission gridlock, probable loss of critical care beds which are blocked with long stay respiratory patients and the cancellation of routine surgical lists [59] . furthermore, there will be fewer hcws available to provide the care due to their own illness or having to look after family members. in this paper we detail why we need to know more about hcws' decision-making and risk-taking behaviour in relation the use of masks for protection against infectious respiratory diseases. we argue that the value of such research would be its potential impact on the ongoing threat of emerging infectious diseases, workforce capability, capacity and educational needs, the financial costs of healthcare and outbreaks and the importance of social responsibility and appropriate legislation in planning for global security. specifically, research is required to determine whether hcws' perception of risk as it relates to the protection of themselves and others against transmission of infection influences their behaviour towards the use of a protective mask. there is also a need to determine the personal, professional and contextual factors that impact on hcws' perceptions of risk and their use of protective masks for infectious diseases. an exploration of the practices and constructs of risk by hcws will therefore provide valuable information to inform policy and pandemic planning. the sub-optimal use by hcws of protective masks for respiratory diseases has a significant impact at individual, organisational, societal and global levels. furthermore, the consequences of poor mask use will be exacerbated during a widespread outbreak or pandemic of a novel infectious respiratory disease, when pharmacological agents or vaccination are unavailable. minimising the transmission of respiratory disease through protective mask use leads to better outcomes for healthcare, workforce capability and economic stability. this paper has presented the background and justification for research into the attitudes and behaviour of hcws towards protective mask use for respiratory infectious diseases during non-outbreak situations so as to optimise the use of masks when indicated in every day practice. the research can provide insight into perceptions of risk and risk-taking behaviour in respect of mask use for respiratory infectious diseases and help to bridge the gap between theory and practice (see table 3 ). rb and rs originated the concept for the paper and rb drafted the manuscript. glg and rs had critical review and input into the preparation of the manuscript. all authors approved the final version of the manuscript. rzs is a senior editor and glg a section editor of infection, disease and health but neither had a role in peer review or editorial decision-making of the manuscript. the authors declare no other conflict of interest. this work is supported by the australian partnership for preparedness research on infectious diseases emergencies (apprise) of which author glg is a chief investigator and author rb is recipient of a doctoral scholarship. this research presented in this article is solely the responsibility of the authors and does not reflect the views of apprise. not commissioned; externally peer reviewed. ethics approval is not required as this is a discussion paper. table 3 tribute to the mask. there was a sick traveller in bed who had an airborne infection to spread the staff did their tasks, but didn't wear masks, and now many people are dead! development of framework for assessing influenza virus pandemic risk standard precautions but no standard adherence health care workers' perceptions predicts uptake of personal protective equipment australian guidelines for the prevention and control of infection in healthcare. national health and medical research council middle east respiratory syndrome coronavirus transmission among health care workers: implication for infection control evaluation of respiratory protection programs and practices in california hospitals during the 2009e2010 h1n1 influenza pandemic scope and extent of healthcare-associated middle east respiratory syndrome coronavirus transmission during two contemporaneous outbreaks in riyadh, saudi arabia applying psychological frameworks of behaviour change to improve healthcare worker hand hygiene: a systematic review the behaviour change wheel: a new method for characterising and designing behaviour change interventions world health organisation. international health regulations rna virus reassortment: an evolutionary mechanism for host jumps and immune evasion in-depth assessment of an outbreak of nipah encephalitis with person-to-person transmission in bangladesh: implications for prevention and control strategies responding to global infectious disease outbreaks: lessons from sars on the role of risk perception, communication and management mers-cov outbreak following a single patient exposure in an emergency room in south korea: an epidemiological outbreak study travel health notices j travelers' health j cdc flu and ebola map j virus and contagious disease surveillance incidence of influenza in healthy adults and healthcare workers: a systematic review and meta-analysis annual burden of occupationally-acquired influenza infections in hospitals and emergency departments in the united states productivity losses related to the common cold more than a cold: hospital-acquired respiratory viral infections, sick leave policy, and a need for culture change effects of upper respiratory tract illnesses on mood and performance over the working day seasonal influenza vaccine effectiveness chasing seasonal influenzadthe need for a universal influenza vaccine estimation of sickness absenteeism among italian healthcare workers during seasonal influenza epidemics increases in absenteeism among health care workers in hong kong during influenza epidemics healthcare worker influenza immunization vaccinate or mask policy: strategies for cost effective implementation and subsequent reductions in staff absenteeism due to illness does vaccinating ed health care workers against influenza reduce sickness absenteeism? pandemic (h1n1) 2009 influenza in australia: absenteeism and redeployment of emergency medicine and nursing staff factors influencing emergency nurses' ethical problems during the outbreak of mers-cov assessing workplace infectious illness management in australian workplaces reasons why physicians and advanced practice clinicians work while sick: a mixed-methods analysis working with influenza-like illness: presenteeism among us health care personnel during the 2014e2015 influenza season the annual impact of seasonal influenza in the us: measuring disease burden and costs mandatory influenza vaccination of healthcare personnel disease burden of 2013e2014 seasonal influenza in adults in korea resource impact of managing suspected middle east respiratory syndrome patients in a uk teaching hospital behind the mask: determinants of nurse's adherence to facial protective equipment risk perception and compliance with quarantine during the sars outbreak compliance with recommended protective actions during an h7n9 emergency: a risk perception perspective barriers to the use of ppe to prevent pertussis exposures in a pediatric primary care network are health care personnel trained in correct use of personal protective equipment? healthcare workers' decision-making about transmission-based infection control precautions is improved by a guidance summary card personal protective equipment processes and rationale for the nebraska biocontainment unit during the 2014 activations for ebola virus disease the individual, environmental, and organizational factors that influence nurses' use of facial protection to prevent occupational transmission of communicable respiratory illness in acute care hospitals risk of self-contamination during doffing of personal protective equipment human factors risk analyses of a doffing protocol for ebola-level personal protective equipment: mapping errors to contamination beyond hand hygiene: a qualitative study of the everyday work of preventing cross-contamination on hospital wards prevalence of preventive behaviors and associated factors during early phase of the h1n1 influenza epidemic clinical excellence commission. infection prevention and control practice handbook. principles for nsw public health organisations behind barriers: patients' perceptions of source isolation for methicillin-resistant staphylococcus aureus (mrsa) perceived barriers to adherence to tuberculosis infection control measures among health care workers in the dominican republic the cookie monster muffler": perceptions and behaviours of hospital healthcare workers around the use of masks and respirators in the hospital setting hospital unit safety climate: relationship with nurses' adherence to recommended use of facial protective equipment nurses' attitudes towards enforced measures to increase influenza vaccination: a qualitative study influenza vaccination of healthcare workers: critical analysis of the evidence for patient benefit underpinning policies of enforcement australian government. workplace health and safety domestic politics and the who's international health regulations: explaining the use of trade and travel barriers during disease outbreaks pandemic (h1n1) influenza 2009 and australian emergency departments: implications for policy, practice and pandemic preparedness the practical experience of managing the h1n1 2009 influenza pandemic in australian and new zealand intensive care units key: cord-307167-mj2vrxdj authors: patel, viren; mazzaferro, daniel m.; sarwer, david b.; bartlett, scott p. title: beauty and the mask date: 2020-08-10 journal: plast reconstr surg glob open doi: 10.1097/gox.0000000000003048 sha: doc_id: 307167 cord_uid: mj2vrxdj nan coronavirus disease 2019 has profoundly changed society, culture, commerce, and perhaps most importantly, human interaction. as the citizens of the world followed government-imposed stay-at-home orders, and as the phrase "social distancing" became part of the daily lexicon in a matter of weeks, the public largely adopted the use of face coverings in public places to reduce potential transmission of the virus. the practice of using face coverings for the nose and mouth, whether with homemade fabrics or with surgical masks, undoubtedly has effects on facial perception. although emotions such as intense fear can be communicated with contraction of the muscles of the brow and those around the eyes, communication of genuine happiness requires contraction of the muscles around the mouth, which is unlikely to be seen behind a face covering. 1 additionally, the lower half of the face, and specifically the perioral area, has been shown to be vital for determinations of attractiveness. in the 1980s, dr. leslie farkas, widely recognized as the father of craniofacial anthropometry, sought to define the facial measurements and proportions associated with attractive faces. 2 when comparing attractive and unattractive faces, dr. farkas found that the greatest differences in facial measurements and proportions were centered around the perioral area, including but not limited to a narrow philtrum, a wider oral commissure distance, and a greater protrusion of the upper vermilion. 3 with this in mind, it is interesting to consider how masks concealing the lower half of the face would affect perceived attractiveness, which has been shown to influence judgments of a range of interpersonal characteristics, such as competence and trustworthiness. 1, 4, 5 the present study was undertaken to assess whether judgments of attractiveness differ when the lower face is covered by a surgical mask. we anticipated that faces covered with surgical masks would be judged as more attractive than faces not covered by a mask. a racially heterogeneous set of 30 male and 30 female faces was obtained from the chicago face database. 6 the chicago face database is a set of high-resolution images of subjects' faces aged between 18 and 40 years, which is available to researchers as a free resource. the faces were altered to simulate the appearance of wearing a surgical mask, using microsoft powerpoint (microsoft corporation, redmond, wash.) (figs. 1-3) . the photographs of faces were evaluated by users recruited and compensated through amazon's mechanical turk (mturk) (amazon corp, seattle, wash.), a crowdsourcing platform. samples generated from mturk have been shown to be of superior quality than that of traditional convenience samples, and mturk has been used in both the social science and plastic surgery literatures. [7] [8] [9] raters were randomly assigned to a set of male or female faces. a series of 60 masked and unmasked faces were then randomly presented, and the raters were asked to rate the attractiveness of each face on a scale of 1 (least attractive) to 10 (most attractive). raters were excluded from the study based on built-in attention checks and by the minimum time limit for completion to ensure data validity. the study was determined to be exempt from review by the children's hospital of philadelphia's institutional review board. ratings of unmasked photographs were used to define 3 categories of attractiveness for men and women: "unattractive" (bottom 33%), "average" (33%-66%), and "attractive" (above 66%). the average of an individual face's unmasked ratings was used to place each face into 1 of these categories. percent improvement of attractiveness from baseline was calculated for each face after application of the mask, and analysis of normal variance was used to compare this between categories. a post hoc analysis was then conducted using scheffe pairwise comparisons. paired t tests were used to determine whether ratings of faces changed significantly after application of a mask. stata version 14 (college station, tex.) was used for data analysis, and standard descriptive statistics were conducted. a total of 496 raters' responses were analyzed. there were significant differences in the average percent improvement for faces in the unattractive, average, and attractive cohorts for both women and men (p < 0.001, p < 0.001, respectively) ( table 1) . interestingly, the largest percentage improvements were seen in the unattractive groups, with an approximately 42% increase in ratings for women and men after the application of a mask. furthermore, in post hoc pairwise comparisons, the unattractive group showed a significantly higher percentage improvement when compared with the average and attractive groups, for both women and men. in contrast, there was no difference in the percentage improvement between the average and the attractive groups, for both genders. when looking at changes in ratings for faces, we found that 100% of the faces in the unattractive group were rated significantly higher after application of a mask, compared with approximately 70% of the average faces, for both women and men. interestingly, in the attractive group, 1 male face (25%) and 1 female face (12.5%) were rated significantly lower after application of a mask. the present study provides novel information about judgments of attractiveness of persons wearing surgical patel et al. • beauty and the mask masks. individuals who were thought to be average or unattractive at baseline were judged as more attractive when wearing masks, which hid their lower face. this effect was the strongest for faces in the lower third strata of attractiveness. although the eyes and the periorbital region are often cited as the facial regions that define beauty, the results from the study suggest that other facial features also contribute to judgments of attractiveness, corroborating the long-held ideal that beauty is a result of the harmony of various facial aspects. 10, 11 symmetry of facial features across the midline of the face, as well as the "averageness" in size and shape of discrete features, has been shown to be reliable markers of facial attractiveness. 12, 13 if disharmonious parts, such as the nose, lips, jaw, and neck, are hidden from view, then perceptions of attractiveness increase. from the perspective of evolutionary biology, symmetry, averageness, and youthfulness of facial features (and bodily features) are markers of physical attractiveness and reproductive potential. 12, 13 in contrast, individuals who have asymmetrical, nonaverage, or non-youthful features are seen as less attractive. the most profound example of this is seen in persons with facial disfigurement, who are not only seen as less attractive, but also assumed to have less positive personality traits than those who are less or non-disfigured. 14 unfortunately, there is recent evidence to suggest that these responses are truly hardwired into the occipitotemporal cortex and anterior cingulate cortex of the brain. 14 it would be interesting to see whether these areas also respond when the lower half of the face is obscured with a face covering or mask. this study has important implications for medical practice. communication of the 7 universal face expressions-anger, disgust, fear, surprise, happiness, sadness, and contempt-involves the entire face. if the lower face is obscured by a surgical mask or face covering, there is potential for the misinterpretation of the information being conveyed in a conversation. in clinical practice, both providers and patients wearing face coverings or masks run the risk of being misunderstood or misunderstanding one another. as we move to a return to normalcy in health care, as well as daily life, we may wish to consider that the physical distancing that has come with the delivery of health care via electronic platforms may enhance patient-provider communication beyond what can occur in person but with faces partially covered by masks. the results of this study also have important implications for society. first, with facial cues being limited, it is interesting to consider where the gaze will turn to make these judgments of attractiveness. will there be increased emphasis on the orbital complex and the upper face or will the gaze then turn to other body parts like the torso? if the practice of wearing masks endures, it would not be surprising for plastic surgeons to see a rise in patients seeking alterations to the body parts that are still visible, as these will be the only ways to express one's attractiveness. conversely, will the use of fillers and neuromodulators in and around the perioral region decline in popularity, and will surgical procedures such as rhytidectomy and genioplasty be sought less frequently? what will happen to the sales of lipstick and tooth whiteners as well as other applied enhancers and cosmetics? additionally, the mask itself could affect perceptions of an individual's attractiveness. will certain colors, patterns, and designs of masks be viewed as more acceptable than others and will we move to the development of a "see-through" mask that allows some emotions visually based in the perioral region to be expressed? the results of this study bring all these questions to the forefront. regardless, it is clear that there are far greater implications for this practice than meets the eye. universal and cultural differences in facial expressions of emotions anthropometric facial proportions in medicine more than skin deep: judgments of individual with facial disfigurement explaining financial and prosocial biases in favor of attractive people: interdisciplinary perspectives from economics, social psychology, and evolutionary psychology the chicago face database: a free stimulus set of faces and norming data evaluating online labor markets experimental research: amazon.com's mechanical turk public perception of helical rim deformities and their correction with ear molding orthognathic surgery has a significant effect on perceived personality traits and emotional expressions ideal facial relationships and goals judgments of facial attractiveness as a combination of facial parts information over time: social and aesthetic factors body image, cosmetic surgery, and minimally invasive treatments psychology of facial aesthetics behavioural and neural responses to facial disfigurement key: cord-329945-p5hljkkm authors: zhou, zhi‐guo; yue, dong‐sheng; mu, chen‐lu; zhang, lei title: mask is the possible key for self‐isolation in covid‐19 pandemic date: 2020-04-08 journal: j med virol doi: 10.1002/jmv.25846 sha: doc_id: 329945 cord_uid: p5hljkkm ma's research shows n95 masks, medical masks, even homemade masks could block at least 90% of the virus in aerosols(1). this study puts the debate on whether the public wear masks back on the table. recently science interviewed dr. gao, director‐general of chinese center for disease control and prevention (cdc). this article is protected by copyright. all rights reserved. states mainly adopt the method of social distance between people to reach 6 feet to prevent infection, but for the covid-19 pandemic, it may not be effective as we supposed. first of all, the disease is highly contagious, and whether a virus with a reproduction number of more than 2 can achieve true isolation through the so-called social distance by feet is a matter of probability rather than mathematics. a recent mit study published in jama found that social distance requires 27 feet to be guaranteed not to be infected, which is not operational in real life 3 . in addition, there are a large number of asymptomatic infections in this outbreak. they look as asymptomatic as ordinary people, but these groups are as infectious as symptomatic patients 4 . as "normal people", the surrounding population will lose their vigilance. in fact, in high-risk areas with a large number of patients, without sufficient testing to confirm clean, everyone can only be seen as potential infected, including themselves. under such circumstances, wearing a mask is the default solution. finally, the issue of propagation in confined spaces is a very important issue which was often ignored. tests have shown that covid-19 can exist for several hours in the state of the smallest of these droplets, sometimes called aerosols 5 . in fact, there have been cases of concentrated infection by a large number of people in confined spaces 6 . when we perform so-called "necessary activities" in a closed environment in supermarkets, banks, or public this article is protected by copyright. all rights reserved. covert coronavirus infections could be seeding new outbreaks aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 like a zombie apocalypse': residents on edge as coronavirus cases surge in south korea key: cord-322923-zxraxgl1 authors: bayersdorfer, jennifer; giboney, sue; martin, rosemary; moore, andria; bartles, rebecca title: novel manufacturing of simple masks in response to international shortages: bacterial and particulate filtration efficiency testing date: 2020-07-16 journal: am j infect control doi: 10.1016/j.ajic.2020.07.019 sha: doc_id: 322923 cord_uid: zxraxgl1 many healthcare systems have been forced to outsource simple mask production due to international shortages caused by the covid-19 pandemic. providence created simple masks using surgical wrap and submitted samples to an environmental lab for bacterial filtration efficiency testing. bacterial filtration efficiency (bfe) rates ranged from 83.0 – 98.1% depending on specific material and ply, and particular filtration efficiency (pfe) rates ranged from 92.3-97.7%. based on mask configuration, specific surgical wrap selected, and ply, the recommended filtration efficiency for isolation and surgical masks of 95% and 98%, respectively can be achieved. these alternative masks can allow for similar coverage and safety when hospital-grade isolation masks are in short supply. many healthcare systems have been forced to outsource simple mask production due to international shortages caused by the covid-19 pandemic. providence created simple masks using surgical wrap and submitted samples to an environmental lab for bacterial filtration efficiency testing. bacterial filtration efficiency (bfe) rates ranged from 83.0 -98.1% depending on specific material and ply, and particular filtration efficiency (pfe) rates ranged from 92.3-97.7%. based on mask configuration, specific surgical wrap selected, and ply, the recommended filtration efficiency for isolation and surgical masks of 95% and 98%, respectively can be achieved. these alternative masks can allow for similar coverage and safety when hospital-grade isolation masks are in short supply. in january of 2020, the first covid-19 case in the united states was identified. the patient was cared for at providence regional medical center everett (prmce) in everett, wa, near seattle. prmce is part of providence, a much larger integrated care network, including 51 hospitals, over 1000 ambulatory care settings, and many long-term and home care programs. as covid-19 spread in the puget sound area, many providence facilities were required to quickly respond to an exceptionally rapid increase in covid-19 cases and reports of patients under investigation. at the same time, personal protective resources became scarce, following many interruptions along the complex network that makes up the healthcare supply chain. healthcare facilities rely on personal protective equipment (ppe) in order to protect their staff from disease transmission. ppe is often manufactured outside of the united states in order to reduce cost, and much of the ppe used in the u.s. is produced in asia. during the covid-19 pandemic, a perfect storm interrupted the supply chain at multiple points -reduced manufacture, shipping, and distribution, alongside significantly increased demand. when it became apparent that some facilities were at risk of running out of masks within days and that replacement stock was unavailable throughout the u.s., providence leaders partnered with local manufacturers to quickly convert their production lines to produce simple masks. healthcare quality masks are rated based on bacterial and particulate filtration efficiency as well as fluid resistance, differential pressure, and flammability. astm standards are widely accepted as the routine standards for production and testing of healthcare quality face masks. astm f2100-e1 1 groups masks into three performance levels (level 1, 2, and 3) based on bacterial filtration efficiencies (bfe) of ≥95%, ≥98%, and 98%, respectively and sub-micron particulate filtration efficiency (pfe) of ≥95%, ≥98%, and 98%, respectively. inclusion in each performance level also requires specific rankings in differential pressure, resistance to penetration by synthetic blood, and flammability which were not considered as part of this study. astm level 1 masks are considered appropriate for low barrier precautions in short procedures and exams that don't involve aerosols, sprays or fluids. astm level 2 masks are considered appropriate for moderate barrier protection for low to moderate levels of aerosols, spray and/or fluids. rates. four different surgical wraps, all from the medline gem series, were used due to availability. eight mask prototypes were constructed in a consistent tri-fold design from each type of gem wrap and single or double material layers (see figure 1 ). all eight prototypes were sent to an environmental lab for bacterial filtration efficiency testing, latex particle filtration efficiency testing, and delta p testing. due to communication issues at the environmental laboratory, bfe/delta p was tested on only four prototypes and pfe was tested on the other four. bfe results ranged from 96.3% to 98.1% in two ply masks produced with medline gem 1, 2, and 3 materials (see table 1 ). bfe results ranged from 83.0% to 97.7% in one ply masks produced with medline gem 1, 2, and 3 (materials are distributed as single ply and were separated prior to mask manufacture). pfe results were similar to bfe results and ranged from 92.3% to 97.7% for one and two ply masks produced with medline gem 2 and gem 3. of note gem 3 one ply mask (prototype h) had a pfe rating of 97.7% which is the only 1 ply mask that demonstrating filtration efficiency >95%. the massive global shortages of ppe supply that arose in early 2020 during the covid-19 pandemic clarified the need for larger strategic caches and back-up methods for generating ppe during a future event. the rapid creation and manufacture of simple surgical masks with similar bacterial filtration efficiency as astm 1 rated masks illustrates one method for future planning in the event that mask shortages arise again. although the masks distributed to staff at providence were created using an assembly line and professional seamstresses, the same product outcome could be achieved using a simple sewing machine. although not ideal, the use of surgical wrap to quickly produce a high quality isolation mask does offer a feasible solution when mask supplies are critically low to ensure healthcare services can continue to be provided while keeping healthcare workers safe. user feedback was gathered regarding original design and comfort by direct caregiver application and trial. prototypes were hand-delivered to hospital units where nursing staff donned the masks and provided specific feedback for consideration and adoption, directly to the designer, who inturn influenced future patterns and manufacturing.healthcare worker reception was very positive to the novel manufactured masks. feedback was received regarding design and breathability, and users felt that both aspects were equal to or better than traditional masks. ppe supply is critical to the health and safety of healthcare workers. investments in growing adequate and appropriate caches of materials are critical, as are investments in identifying methods for quickly generating ppe locally during times of low supply. the method described in this paper could be easily replicated at other sites for use when supplies are critically low and use of locally manufactured masks with known bfe ratings are logically superior to alternatives (like cloth masks or scarves). limitations of this study include assessment of other astm criteria, including flammability and fluid permeability. although some data is likely available regarding these characteristics of surgical wrap, that information was not explored as part of this study due to the urgency of need for rapid production. utilizing a full face shield over the surgical wrap mask can reduce the risk of fluid exposure. masks produced outside of normal distribution processes also lack necessary regulatory approvals. these masks were not labeled as healthcare quality and were only used for limited periods of time while astm rated masks were unavailable. standard specification for performance of materials used in medical face masks. world trade organization technical barriers to trade committee testing the efficacy of homemade masks: would they protect in an influenza pandemic sincere thank you to the team from kaas upholstered for their support with rapid mask production during a time of great need.none of the authors report conflicts of interest. face mask key: cord-309575-7orflz20 authors: vuolo, mike; kelly, brian c.; roscigno, vincent title: covid-19 mask requirements as a workers’ rights issue: parallels to smoking bans date: 2020-07-16 journal: am j prev med doi: 10.1016/j.amepre.2020.07.001 sha: doc_id: 309575 cord_uid: 7orflz20 nan considerable public debate has emerged regarding the importance of wearing masks to prevent the spread of coronavirus disease 2019 (covid19) , and thus whether they should be required in workplaces. recognizing precedents for constraining individual behavior within workplaces, this article draws parallels to smoking bans and argues that mask requirements should be considered fundamental occupational health protections. as with smoking in confined spaces dispersing environmental tobacco smoke, mask-less patrons exacerbate risks for workers via the diffusion of respiratory droplets. the context of indoor environments matters for the prevention of these potential health hazards. smoke particulates diffuse in confined spaces to those nearby, accumulating to levels that can result in or aggravate health conditions. 1,2 for covid-19, confined indoor spaces facilitate the diffusion of respiratory droplets containing the virus-diffusion that can be reduced by masks. 3 although valid reasons exist to require masks outdoors where individuals congregate, this article focuses on indoor requirements because delays in addressing this issue, especially as states reopen with varying degrees of rapidity, will very likely be detrimental to public health and particularly the well-being of frontline workers. the sources of implementation of workplace mask requirements vary. like smoke-free environments, private businesses are free to implement mask requirements for customers and employees even absent public policy. some, however, choose not to implement requirements owing to fears of alienating customers, some of whom, as protests have revealed, view the imposition of health guidelines as an infringement on individual liberties. for the sake of occupational health, state and local governments should take an active stance to promote mask wearing in workplaces for the enhancement of population health in general, but the health of frontline workers in public-facing industries in particular. responding to images of mask-less crowds patronizing recent business re-openings, u.s. health secretary azar said, "that's part of the freedom we have here in america." 4 this encapsulates the main argument against mask requirements, as something akin to infringement on individual liberties. notably, similar arguments have been expressed regarding smoking in workplaces. 1 individual liberties should not be taken lightly, of course, but such liberties do not extend to the imposition of risk to others. even political philosophies emphasizing personal liberties over state intervention, such as libertarianism and liberalism, recognize the limits of rights to the point of harm to others. [5] [6] [7] yet, as demonstrated by viral videos showing confrontations between employees and customers, 8 many individual liberty proponents are defensive even with precedents for restricting certain liberties for the sake of reducing hazards to others. indeed, this point was summarized well by craig jelinek, president and ceo of costco, who stated, "this is not simply a matter of personal choice; a face covering protects not just the wearer, but others too… and our employees are on the front lines." 9 similar to smoking inside retail shops, restaurants, or public transportation, today's mask-less patron impedes workers' rights to safe and healthy occupational environments in addition to posing risks to other patrons. although a mask refuser or smoker might argue that other patrons could simply frequent mask-wearing/smoke-free establishments, or even not go out at all, such logic neglects workplace rights and risks to workers' health. this point is all the more pressing considering that: (1) the primary rationale against stay-at-home orders was to return workers to their jobs and (2) many states have indicated that workers who refuse would forego unemployment benefits. this creates a difficult choice, as workers cannot simply change jobs in the face of emergent health risks, especially given difficulties finding employment in another field for which one is qualified. moreover, because health policies and job options are geographically determined, workers will likely face the same environment if reemployed elsewhere. there is little reason why debates about indoor mask wearing should not consider the same standards that undergirded original arguments for indoor smoking bans-those grounded in concerns for workplace safety and health, and executed and monitored by local and state agencies. 1,10 indeed, decades of research have shown that smoking bans led to measurable improvements in working conditions and worker health. 2, [11] [12] [13] although the literature on covid-19 and occupational health is only just developing, studies on mask wearing released thus far 3 imply that frontline workers will spend long hours with potential exposure to covid-19 and its harms without similar protections or oversight. although some (e.g., individual rights proponents) will cry foul about uniform protections being an attack on individual liberty or business functioning and profit, it is important to recognize that smoking bans were originally contested for the same reasons 10 but now are less often viewed as such. extending mask requirements to the types of workplaces that have long been smoke-free, including those in which workers interface with the public-such as retail and transportation/travel-is essential for the health and safety of workers. although smoke-free policies are not universal in restaurants and bars (contested locations for mask wearing as well), existing smoking bans offer a clear precedent-a precedent wherein worker's rights to a healthy work environment ultimately take precedence over patrons' preferences. private business owners may resist, viewing any government intervention as an affront to a free market and business rights. such tensions, however, are hardly new. there is a long history of pitting business interests against labor generally and the rights of workers to security, fair compensation, and safety and health in the u.s. 14 although workers have tended to be on the losing end of these battles for the last several decades, federal and state governments are more inclined to intervene during times of economic instability in a manner that is simultaneously good for workers and business. 14 here too, there are parallels to smoking bans. many service-industry owners initially argued that they would lose revenue if they obeyed smoking bans, yet such revenue disruptions did not materialize. 15 this was due, in part, to the fact that the geographic nature of bans restricts customer alternatives. indoor mask requirements for the sake of employees, and other patrons as well, would work similarly if federal, state, and local governments take a stronger stance for their citizenry and those workers most at risk. intimately tied to the question of workers' rights to a healthy workplace and potential oversight/protections are concerns about inequality. the particular flashpoints for both smoking bans and mask requirements are public-facing workplaces, particularly in service and retail industries. these sectors are disproportionately composed of lower wage and racial/ethnic minority workers. 16 in this manner, mask requirements within public-facing workplaces may be a key means to reduce covid-19 inequalities. lower wage and minority workers already experience health disparities, 16 including sicknesses linked to both smoking 17 and covid-19. 18 they are also simultaneously disadvantaged when it comes to healthcare access. 17 by urging a return to work without mask requirements, states are essentially requiring vulnerable populations to risk their health for the benefit of patrons. from health and inequality research, 17 including on smoking bans, 19 it is relatively easy to anticipate that not requiring masks in workplaces open to the public will exacerbate inequalities in covid-19 for already vulnerable segments of the lower-wage and racial/ethnic minority workforce, which will have broader inequitable impact on their families and communities. second, consistent and monitored legal requirements for mask wearing, particularly indoors, will be especially essential for workers' rights to safety and well-being until the pandemic is resolved. as states reopen, some more rapidly than others, the immediate health benefits of mask-centered policy cannot be overstated given current evidence on the role of respiratory particulates in viral transmission and the ability of masks to reduce these particulates. 3 further, for smoking bans and other tobacco control policies, a key behavioral mechanism for change was denormalization 1 ; that is, the process of identifying and defining a behavior as non-normative with the aim of benefitting public health. by emphasizing workers' rights to a healthy working environment, the same mechanisms may be applied to masks. denormalizing mask refusal may lead to wider substantive changes that promote public health, and potentially extend mask wearing more broadly, including to outdoor spaces where people congregate and even beyond the covid-19 pandemic. mask wearing is ubiquitous in countries in east asia, which some have credited to the normalization of mask-wearing behavior resulting from past epidemics in the region. 3, 20 thus, if mask wearing can be normalized now through policies targeting covid-19, workers may experience reduced risk not only from covid-19, but also future airborne epidemics and common illnesses such as influenza. thus, even though mask-wearing requirements can eventually be lifted when the pandemic subsides, there may be long-term benefits to normalizing mask wearing, such that voluntary adoption during influenza season occurs. third, many business owners enforce a smoking ban even when not required by law. in the interests of their workers, businesses should implement mask-wearing policies in locales lacking such laws. as an additional incentive to business owners, the perception of a healthy and safe working climate is associated with increased worker productivity, along with the health benefits to employees. 21 finally, smoking ban enforcement often occurs informally, via business owners, employees, and other patrons, with state authorities stepping in only when violations are consistent. although smoking and mask-wearing violations are both easy to identify, the risk from the smoker is clear from the behavior. it is much more difficult, on the other hand, short of a test, to detect whether an individual is infected with covid-19 and putting workers at risk. if anything, however, this discrepancy makes indoor mask requirement policies all the more important, as it remains unknown who may pose a risk to workers, especially given the possibility of asymptomatic transmission. given the mortal threat of covid-19 to some and the possibility of a second wave of the pandemic, clear and consistent policies for mask wearing and enforcement by state and local governments is warranted. having such policies will enable employers to do what is right for patrons while simultaneously conferring on employees the dignity and protections they deserve. much as indoor smoke-free policies do not eliminate all threats to impaired pulmonary and cardiovascular health, indoor mask requirements are unlikely to eliminate all covid-19 risks to workers. other actions are necessary as well, such as the centers for disease control and prevention's recommendations for businesses: distancing where possible, reducing the need to touch surfaces and disinfecting frequently touched surfaces, and handwashing breaks and proper sanitary practices. 22 nonetheless, as smoking bans greatly reduced exposure to environmental tobacco smoke for workers, mask requirements would greatly reduce exposure to respiratory droplets that enable viral transmission. 3 ultimately, much like stepping outside to smoke, wearing a mask until the pandemic is resolved may feel like a nuisance; however, both pose a relatively small inconvenience when compared with workers' rights to a healthy, safe work environment. science, politics, and ideology in the campaign against environmental tobacco smoke change in indoor particle levels after a smoking ban in minnesota bars and restaurants physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and metaanalysis so far, no spike in coronavirus in places reopening, u.s. health secretary says. reuters second treatise of government: an essay concerning the true original, extent and end of civil government on liberty and other essays a full vindication of the measures of congress video shows costco worker calmly handle customer berating him over mask policy. nbc news do smoking ordinances protect non-smokers from environmental tobacco smoke at work? effects of a smoke-free law on hair nicotine and respiratory symptoms of restaurant and bar workers effects of smoking restrictions in the workplace workplace smoke-free policies and cessation programs among us working adults the achievement of american liberalism: the new deal and its legacies the effect of ordinances requiring smoke-free restaurants and bars on revenues: a follow-up race, gender, and new essential workers during understanding sociodemographic differences in health--the role of fundamental social causes disparities in the population at risk of severe illness from covid-19 by race/ethnicity and income moving upstream: the effect of tobacco clean air restrictions on educational inequalities in smoking among young adults covid-19: should the public wear face masks? perceived workplace health and safety climates: associations with worker outcomes and productivity covid-19): general business frequently asked questions the authors have no conflicts of interest, grant support, or financial disclosures to report. key: cord-332577-2z5pchyq authors: adolph, c.; amano, k.; bang-jensen, b.; fullman, n.; magistro, b.; reinke, g.; wilkerson, j. title: governor partisanship explains the adoption of statewide mandates to wear face coverings date: 2020-09-02 journal: nan doi: 10.1101/2020.08.31.20185371 sha: doc_id: 332577 cord_uid: 2z5pchyq public mask use has emerged as a key tool in response to covid-19. we develop and document a classification of statewide mask mandates that reveals variation in their scope and timing. some u.s. states quickly mandated the wearing of face coverings in most public spaces, whereas others issued narrow mandates or no mandate at all. we consider how differences in covid-19 epidemiological indicators, state capacity, and partisan politics affect when states adopted broad mask mandates. the most important predictor is whether a state is led by a republican governor. these states were much slower to adopt mandates, if they did so at all. covid-19 indicators such as confirmed cases or deaths per million are much less important predictors of statewide mask mandates. this finding highlights a key challenge to public efforts to increase mask-wearing, widely believed to be one of the most effective tools for preventing the spread of sars-cov-2 while restoring economic activity. public mask wearing is now widely viewed as a low-cost and effective means for reducing sars-cov-2 virus transmission (1; 2; 3). however, it was not until april 3, more than a month after the first reported case of the novel coronavirus in the us, that the cdc formally recommended mask wearing to the general public (4) . across the u.s., voluntary adherence to the cdc's mask recommendation has been uneven. unlike some other societies, mask wearing in response to contagion is not a cultural norm in the u.s. (5) . the absence of such a norm or a national mask mandate has resulted in considerable policy variation across states (6) . as with other non-pharmaceutical interventions (npis), such as business and school closings and stay-at-home directives (7), many u.s. states did not broadly require that citizens wear masks across a range of indoor public spaces, even as the scientific and public heath case for mask wearing grew stronger. there was also considerable variation in how quickly states adopted mandates, among those that did. at first glance, this variation appears to fall sharply along political party lines. for example, sixteen of the 17 states that have not adopted broad mandates are led by republican governors. it is also the case that most of the early-adopting states were led by democratic governors. but it is possible that first impressions fail to account for other factors. the mounting scientific evidence that masks are an effective means for slowing the spread of sars-cov-2 makes it more important to understand the most important drivers of state covid-19 responses. using originally collected data on mask mandates across states, we examine how differences in covid-19 indicators, state capacity, and partisan politics may have affected the speed of mask mandate adoption. specifically, we recorded when a state issued a mask mandate (if it did), developed a three-point scale to classify the breadth of each mandate, and performed an event history analysis to explore variations in the timing of the broadest mandates that require individuals to wear masks while indoors in public spaces. controlling for the seven-day moving average of reported covid-19 deaths and state citizen ideology, we find the governor's party affiliation is the most important predictor of state differences in the timing of indoor public mask mandates. the marginal effect of a having republican governor instead of a democrat was a 29.9 day (95% ci: 24.6 to 35.2) delay in the announcement of broad state-wide mask mandates. this effect is far larger than the effect of any other variables examined and is robust to many different sensitivity analyses testing a large number of possible confounders. we collected data on all statewide directives mandating masks issued over the period april 1 to august 13. we consider a public mask mandate to be any policy that requires individuals to wear masks or other mouth and nose coverings when they are outside their places of residence. we include only mandates which apply to all individuals within a given setting, allowing exceptions for individuals with certain medical conditions or for young children. our data thus do not include mandates which only require the use of masks or other personal protective equipment by specific employees as part of business operations. to further capture variation across mask mandates applying to the general public, we create a typology with three ordered categories that encompass all state-wide public mask mandates issued over this period: limited mandate (level 1). policies in this category involve limited mask mandates applying only to specific public settings. for example, mask mandates at this level might apply only to transportation services (e.g., issued by vermont on may 1, augmented to a level 3 policy on july 24) (8; 9), to retail establishments (e.g., issued by alaska on april 22 and ended on may 22) (10), or to large gatherings where social distancing is not possible (e.g., issued by new hampshire on august 11)(11). a common example of a limited mandate is one which applies only to people visiting government buildings (e.g., issued by utah on june 26 and south carolina on august 3) (12; 13). broad indoor mandate (level 2). policies in this category constitute broad mask mandates requiring the use of masks or cloth face coverings by the public across most or all sectors of public activity indoors or in enclosed spaces. mandates in this category may also include requirements that members of the public wear masks while waiting in line to enter an indoor space, or while using or waiting for shared transportation. for example, minnesota's mask mandate (issued july 22) requires people over five years of age who are medically able to wear facial coverings or masks "in an indoor business or public indoor space, including when waiting outdoors to enter an indoor business or public indoor space, and when riding on public transportation, in a taxi, in a ridesharing vehicle, or in a vehicle that is being used for business purposes" (14) . broad indoor and outdoor mandate (level 3). policies in this most comprehensive category mandate the use of face coverings by the public across all public indoor spaces and in outdoor settings, though exceptions may be made for outdoor mask wearing where 3 . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint social distancing is possible. for instance, new york issued a mask policy on april 15 mandating all individuals who are medically able and over two years of age to wear a mask when in a public place and unable to maintain social distancing (15) . washington state's mask mandate, issued june 24, requires that "every person. . . wear a face covering that covers their nose and mouth when in any indoor or outdoor setting" (16) . because level 1 reflects a very limited mask mandate from the perspective of preventing transmission of the novel coronavirus, we concentrate our analysis on adoption of mandates at level 2 or 3: mandates that at a minimum include a broad requirement to wear masks indoors in public spaces. for these policies, we coded both the dates on which statewide policies were issued in each state at each level, as well as the date of enactment of each policy. because our objective is to better understand the factors that influenced governors' decisions to implement mask mandates, we focus on the dates the policies were issued. (if our objective were instead to study the effects of mask mandates, the date of enactment might be more appropriate. notably, we include a sensitivity analysis using dates of enactment that does not find substantive or statistical differences in the factors predicting mask mandate adoption.) the top panel of figure 1 shows when broad statewide mandates requiring masks in indoor public spaces (level 2 or higher mandates) were adopted across the us, starting in april 2020. the bottom panel shows when the broadest dual indoor-outdoor mandates were adopted (level 3). these adoptions occurred in two phases: from the middle of april to the end of may, eleven states adopted level 2 or higher mandates; most (8) were level 3 mandates. the second phase began in mid-to late-june, and continued into early august. in this later phase, an additional 22 states adopted mask mandates of at least level 2 or higher, bringing the total number of states with broad mandates to 33. most of these (17) were also level 3 mandates (for a total of 25 level 3 mandates). four of these 17 (maryland, michigan, new jersey, and oregon) had already adopted level 2 mandates in april. thus, by 12 august 2020, two-thirds of states, containing at least 76% of the u.s. population, had a statewide mask mandate requiring masks in indoor settings. half of states, containing 63% of the population, further required masks to be worn outdoors statewide. we use cox proportional hazards models to explore how different factors influenced the timing of broad statewide mask mandates across the fifty u.s. states. these factors 4 . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. alaska and hawaii adopted limited mask mandates (level 1) but later ended those mandates. sources: authors' original data collection (17) . data available at http://covid19statepolicy. org. . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint include covid-19 indicators, state capacity, and partisan politics. figure 2 reports the results from our baseline model, which controls for the log of covid-19 deaths per million population reported in the state as seven-day moving averages, the ideological orientation of each state's citizenry, and the party of the governor (18; 19; 20) . these results are reported both using traditional hazard ratios (top panel of figure 2 ) and as average marginal effects across all fifty states, expressed as the average expected days of delay associated with each factor (bottom panel of figure 2 ). by far, the most powerful predictor of broad mask mandate adoption and timing is the political party of the governor. holding constant state ideology and the rate of deaths per million, at any given time democratic governors are 7.33 times (95% ci: 2.68 to 16.17 times) more likely to adopt a mask mandate than are republican governors. we can also use the estimated cox model to predict the total expected delay hypothetically associated with having a republican governor (rather than a democratic governor) in each state, while leaving state ideology and daily deaths per million at their observed values for each state-day. we find that averaged across the fifty states, the marginal effect of having a republican governor is a 29.9 day delay in adopting a broad indoor mask mandate (95% ci: 24.6 to 35.2 days). the party of the governor is not the only political variable that influences the likelihood of adoption. holding constant the party of the governor, states with more liberal citizens adopt mandates earlier than states with more conservative citizens. for example, states at the 75th percentile of citizen ideology (more liberal) are 1.72 times more likely to adopt mask mandates at a given time than more conservative states at the 25th percentile of citizen ideology (95% ci: 1.18 to 2.40 times). the marginal effect of this inter-quartile difference in citizen ideology is a 7.2 day delay of indoor mask mandates in more conservative states (95% ci: 5.8 to 8.7 days). researchers and policy-makers use several metrics to track sars-cov-2 transmission, and governors have access to daily data on covid-19 measures including confirmed cases, deaths, and positive test result rates. in our models, daily deaths per million consistently dominates measures of new cases per million and test positivity rates as a factor associated with the timing of broad statewide mask mandates. nevertheless, the effect of daily deaths is much weaker than the effect of governors' party affiliation. we find that a state at the 75th percentile for daily covid-19 deaths per million population is 2.19 times more likely to adopt a mask mandate than a state at the 25th percentile (95% ci: 1.45 to 3.19). our model suggests a state with a lower rate of daily covid-19 deaths will adopt mask mandates 10.5 days later than a state with a higher daily death rate (95% ci: 8.5 to 12.5 days). . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. as republican governors and conservative citizens often go together, the relative importance of politics on mask mandate adoption is even greater. when combined, the expected delay in adopting at least an indoor mask mandate for a state with both a republican governor and a conservative citizenry is 38.1 days (95% ci: 31.1 to 45.1 days) when compared to a democratic governor in a liberal state. the majority of this delay is attributable to the party of the executive, highlighting the importance of state-level political leadership in fighting the virus. . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint we conducted several additional analyses to test the robustness of these findings. first, we considered the possibility that our results were sensitive to either the source of daily covid-19 data used in the model or the set of covid-19 indicators used for each state-day. our baseline model used data reported by the new york times on daily covid-19 deaths for each state (18) . figure 3 reports results from a series of models that use alternative sources of daily death counts (21; 22) . as the top of the figure makes clear, the gap between the effect of governor partisanship and the effect of deaths per million remains at least as large as in the baseline model across the alternative indicators. while deaths are perhaps the most politically salient consequence of the pandemic, they are the least timely indicator of the severity of transmission in a given place and time, operating at a lag of approximately two or more weeks from the time of infection (23; 24). we therefore consider models adding controls for more timely indicators of the spread of sars-cov-2: the number of confirmed covid-19 cases per million reported in each state each day and the rate of test positivity (in both cases, as sevenday moving averages). states taking prompt action to stem the spread of the virus should arguably be responsive to these indicators. although the effect of higher rates of case growth is in the expected direction of possibly encouraging mask mandates, the relationship is not statistically significant in a model that controls for the count of deaths. (this pattern holds regardless of the data source used for confirmed cases.) the rate of positive tests in a state had no relationship with mandate timing once deaths per million is controlled. in all models, the partisan effect was unchanged. in addition to alternative measures of public health indicators, we consider a series of additional control variables, none of which alter our findings regarding the effect of partisan governors ( figure 4 ). first, we add a third measure of partisan politics, either trump's vote share in the state in the 2016 presidential election or the percentage of people in the state who watch fox news regularly (25; 26) . neither helps explain mask mandate timing in models that also control for governor party and citizen ideology. this may indicate that direct effects of these factors cannot be isolated, or that their impact on timing is mediated through governors and through their conservative audiences. next, we consider the possibility that states adopt mask mandates either in imitation of policies adopted by other states or in reaction to the spread of the virus in neighboring states. we find that, controlling for governor party, citizen ideology, and the daily death rate within a state, neither the adoption of mask mandates by neighboring states nor the average death rate in neighboring states is associated with the timing of mandates. we also control for the rate of mask mandate adoption in "peer states": cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint other states (often not neighbors) identified using network analysis as the innovators which a given state most often imitates across a variety of policy areas (27) . somewhat puzzlingly, whether peer states have adopted mandates is negatively associated with mandate adoption once our baseline controls are included, a result we suspect is spurious (and which does not alter our main findings). other controls which fail to explain mandate timing when added to the model include the percentage of state residents above the age of 70 or in possession of a college degree (28) , as well as the log of population density (29) and the log of gross state product per capita (a reasonable non-finding given the minimal economic consequences of a mask mandate, in contrast to many other non-pharmaceutical interventions) (30) . we consider one last control: the (pre-epidemic) count of icu beds in each state per capita, which if low might add urgency to state policies to combat the pandemic (31) . we find the opposite: states with more icu beds per capita are more likely to adopt mask mandates. it may be that states that are more generally prepared to address health care needs are also more likely to implement preventive services such as mandates. in any event, inclusion of this control does not alter our main findings. finally, we consider changes to the model outcome and scope. the first change is simple: instead of measuring time to the issuance of mask mandates, we model the time to the enactment dates contained in those mandates; our results are unchanged. the second modification is more noteworthy and divides the data into two periods. in the first period, the months of april and may, states that adopted mask mandates did so either before they eased social distancing mandates, or concurrent with efforts to ease social distancing and re-open business sectors. for most states, the second period, june and july, followed substantial easing of social distancing policies and saw rising numbers of cases starting in mid-june (32) . in the first period, states may have issued mask mandates as a preventative policy layer to mitigate transmission risks associated with easing social distancing restrictions (33) . by the second period, the benefits of wearing non-medical masks against sars-cov-2 transmission were better understood (34; 35). despite partisan resistance to mask mandates on the part of republican voters and president trump, one could imagine governors of both parties coalescing in june and july around mask mandates as the least costly intervention to protect fragile state economies and create a path to normal social interactions (1; 2). yet when we restrict our analysis to start on june 1 instead of april 1, we find substantively similar relationships -and an even stronger partisan governor effect (hazard ratio of 13.08, 95%ci: 4.18 to 31.34), suggesting mask mandates became more partisan in the summer of 2020. . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint masks are an important tool in the strategies of countries that have slowed the spread of covid19 (35; 34) . near-universal mask wearing reduces the risk implicit in returning to aspects of normal life, and may be especially important for protecting essential workers who are not able to limit their exposure (35; 36; 34) . in some countries, mask wearing is a well-established cultural norm (5). this was not the case in the u.s. prior to covid-19. by early summer 2020, governors of both parties surely recognized the pandemic's threat to their states and were also well aware that it was transmitted via aerosols. one might therefore expect these leaders to be eager to encourage mask wearing as an alternative to the steep social and economic costs implicit in prolonged social distancing measures such as stay-at-home orders. the rapid progression of the pandemic also suggests that mandates, rather than public education campaigns, would be the preferred approach to ensuring mask compliance. why, then, were so many republican governors reluctant to promote a relatively low-cost and effective intervention? our event history analysis cannot speak to motives. the most likely explanation, we believe, is that the absence of a mask wearing norm in the u.s. opened the door to reactionary responses. from the beginning of the pandemic, president trump has seemed more concerned about the pandemic's threat to the economy than to public health, and may see mask wearing as a prominent public reminder of a problem that he was consistently trying to minimize. the president remains opposed to a national mandate (37) and has mocked those who do wear masks (38) . his behavior promoted partisan division on mask wearing. republican identifiers are now much less likely than democratic identifiers to say that they wear masks all or most of the time (53% vs. 76% in august 2020) (39) . in addition, many americans, and especially republicans, resisted mask wearing as a sign of weakness or "unmanly" behavior (40; 41; 42) , perhaps based on the mistaken assumption that self-protection is the primary objective of mask wearing. this political dynamic may help to explain why president trump steadfastly refused to wear a mask despite widespread urging that he set a public example (43) , and why he publicly mocked democratic presidential nominee joe biden for wearing one. the u.s. is as polarized politically as it has ever been, including across and within state governments (44; 45; 46) . a plausible hypothesis is that many republican governors delayed imposing mask mandates, not because they believed them to be ineffective or unnecessary, but because they were unpopular with republican voters, who continue to support trump by wide margins (47) . a republican governor who man-12 . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint dated masks risked being portrayed as weak, threatening their base of support and possibly the support of their party's national leader. democratic antipathy toward trump and his cavalier rejection of the recommendations of his own government, a generally positive view of mask wearing among constituents (48; 49; 39) , and widespread mask wearing by democratic leaders (including biden) made it much easier politically for democratic governors to support mask mandates. although republican governors were generally more resistant to mandates, some eventually succumbed to the reality of rising cases and deaths in their states (including greg abbott of texas, kay ivey of alabama, and tate reeves of mississippi). others, however, continued to reject the recommendations of public health officials in the face of rampant cases and deaths in their states (including brian kemp in georgia, ron desantis in florida, and doug ducey in arizona). by the end of our study period, 33 states required masks indoors (level 2 or higher), so that three-quarters of americans now live under state-wide indoor mask mandates. the remaining resistance is highly partisan: thirteen of the 14 states that have yet to adopt broad mandates are led by republican governors. mask wearing can help to reduce transmission of the coronavirus. widespread compliance with mask mandates in many localities across the u.s. suggests that a valuable norm may be developing that will have longer term positive consequences for pandemic response (50) . however, at the state-level, the politicization of this important intervention has delayed the adoption of broad, consistent mandates on an affordable and effective behavior to reduce coronavirus spread. we estimate an event history model to predict the timing of announced mask mandates across u.s. states from april 1, 2020 to august 12, 2020. specifically, we model the likelihood that a state will implement a mask mandate of at least level 2 (broadly requiring face coverings indoors) as a function of time in days with a cox proportional hazards model, clustering standard errors by state. all states are at risk of adopting a mandate starting on april 1, and remain at risk until they adopt a mandate at either level 2 or level 3. in this model, the baseline hazard rate non-parametrically captures the effects of purely national trends -such as the common tendency of states to adopt mask mandates due to the national resurgence of new covid-19 cases and deaths, or as a result of new scientific findings regarding the effectiveness of masks in reducing 13 . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint coronavirus transmission. this leaves only cross-state variation in the timing of mask mandates to be explained by covariates. our primary specification, reported in table 1 , includes two time-invariant covariates -the ideological orientation of each state's citizenry and the party of the governor (19; 20) . we also control for a time-varying covariate, the daily reported covid-19 deaths per million population in each state using data from the new york times (on covid-19 deaths) (18) and the us census (on population) (28) . deaths per million enter the model as a seven-day average (to smooth over differential rates of reporting over weekends and weekdays) and logged (to allow for diminishing marginal effects of rising covid-19 deaths and to mitigate the influence of outliers, which in some cases likely reflect idiosyncratic reporting delays). logging this term improves model fit (concordance increases from 0.821 to 0.833), but poses the problem of how to deal with seven-day averages over periods with no reported deaths. a common but flawed solution is to add a small "fudge" factor (e.g., 0.01, or 1, etc.) to cases of zero deaths to ensure the log of deaths per million is always defined; however, this technique produces different results depending on the (arbitrary) amount added. this is an underappreciated but unsurprising problem, as the range of plausible adjustments covers several orders of magnitude. while differences across plausible "fudge" factors do not affect our substantive or statistical conclusions enough to change our findings, a non-arbitrary solution is preferable. instead, we rely on the data to suggest the appropriate treatment of zeros by including an additional covariate indicating cases of exact zero values of the moving average of deaths. in turn, before logging the moving average of deaths, we replace zeros with ones, ensuring (without loss of generality) that the zero cases drop out of the log term. the results from this zero-adjusted log specification are similar to those from models that use a "fudge" factor, but arguably less arbitrary and more data-driven. the hazard ratios associated with each covariate in our primary model are reported in table 1 . the schoenfeld residuals for each covariate shows no evidence of violation of proportionality, supporting the proportional hazard assumption. for continuous covariates, we show the hazard ratio associated with an interquartile shift in the covariate, as recommended by harrell (51) . these are the hazard ratios reported in the top panel of figure 2 in the main text. following the approach of adolph et al. (7), we contextualize these findings by computing the average marginal effect of each covariate averaged across the fifty states (52) , expressed as the expected days of delay associated with each covariate, averaged across the fifty states with all other covariates taking on their observed values day by day for each state. these quantities are shown in the bot. cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. tom of figure 2 in the main text. analyses were performed in r (version 4.0.2) using the survival and coxed (52) packages. all visualizations were constructed using the tile package (53) . in addition to the primary model reported in the table 1 and figure 2 , we consider a series of sensitivity analyses. throughout these analyses, we attempt to keep each estimated model parsimonious, as including too many covariates is a particular concern for event history models with small numbers of observed events (54) . the first sensitivity analyses reported in figure 3 simply replace the new york times death data used in the primary model with data from alternative sources (the covid tracking project or johns hopkins university) (21; 22) . however, most of the sensitivity analyses retain the covariates of the primary model and serially add a single additional covariate. as a final robustness check, we report a complementary analysis focusing on the time to adoption of mandates requiring masks both indoors and outdoors (level 3 mandates). the results of this analysis are reported in table 2 and figure 5 . only half of the states had adopted so broad a mask directive by august 12, and while the hazard ratio associated with a higher moving-average of deaths per million was little changed from the more inclusive model of both level 2 and level 3 mandates (2.03 versus 2.19), the haz. cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint ard rate associated with the party of the governor shrank (from 7.33 to 3.11) and the hazard rate associated with conservative citizen ideology grew (from 1.72 to 2.52). in all cases, these results remained significant at the 0.05 level and associated with substantively noteworthy average marginal effects. states with higher rates of daily deaths per million could be expected to adopt combined indoor-outdoor mask mandates 8.7 (95% ci: 6.8 to 10.7) days later than states with low rates of daily deaths. the expected delay associated with republican governors was 13.9 days (95% ci: 10.7 to 17.0), while more states with more conservative citizens could be expected to adopt level 3 mandates 11.2 (95% ci: 8.2 to 10.7) days later than states with liberal citizens. the combined delay for states with republican governors and conservative citizens was 26.0 days (95% ci 19.5 to 32.6). . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. . cc-by-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not certified by peer review) the copyright holder for this preprint 2020. this version posted september 2, . https://doi.org/10.1101/2020.08.31.20185371 doi: medrxiv preprint physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis community use of face masks and covid-19: evidence from a natural experiment of state mandates in the us face masks against covid-19: an evidence review. preprints recommendation regarding the use of cloth face coverings, especially in areas of significant community-based transmission face masks are in. the atlantic what countries have mask laws? pandemic politics: timing state-level social distancing responses to covid-19 addendum 12 to executive order 01-20 archived at http://covid19statepolicy.org as state policy source vermont0022 archived at http:// covid19statepolicy.org as state policy source alaska0014 emergency order 63 pursuant to executive order 2020-04. august 11 archived at http:// covid19statepolicy.org as state policy source southcarolina0031 archived at http:// covid19statepolicy.org as state policy source utah0029 archived at http:// covid19statepolicy.org as state policy source minnesota0023 archived at http:// covid19statepolicy.org as state policy source newyork0012 archived at http://covid19statepolicy.org as state policy source washington0046 state-level social distancing policies in response to covid-19 in the us. version 1.78 covid-19) data in the united states updated measures of citizen and government ideology. data file the national conference of state legislators. state partisan composition. data file the covid tracking project. states current and historical data. data file novel coronavirus covid-19 (2019-ncov) data repository. data file visualizing the lagged connection between covid-19 cases and deaths in the united states: an animation using per capita state-level data case-fatality risk estimates for covid-19 calculated by using a lag time for fatality presidential election results: donald j. trump wins cable news viewership: fox news persistent policy pathways: inferring diffusion networks in the american states global burden of disease study 2017 population estimates 1950-2017. data file us census. population density. data file gross state product. data file harvard global health institute. hospital capacity by state. data file as virus surges, younger people account for disturbing number of cases absence of apparent transmission of sars-cov-2 from two stylists after exposure at a hair salon with a universal face covering policy a modelling framework to assess the likely effectiveness of facemasks in combination with 'lock-down' in managing the covid-19 pandemic impact of population mask wearing on covid-19 post lockdown. medrxiv donald trump vows not to order americans to wear masks biden, seizing on masks as a campaign issue, calls for a mandate. the new york times most americans say they regularly wore a mask in stores in the past month; fewer see others doing it the effect of messaging and gender on intentions to wear a face covering to slow down covid-19 transmission development and validation of the masculinity contest culture scale masks and emasculation: why some men refuse to take safety precautions trump wears mask in public for first time during visit to walter reed interest group activists and the polarization of state legislatures no middle ground: how informal party organizations control nominations and polarize legislatures the ideological mapping of american legislatures presidential approval ratings -donald trump partisan pandemic: how partisanship and public health concerns affect individuals' social distancing during covid-19. ssrn, 2020 a detailed map of who is wearing masks in the u.s. the new york times face coverings for covid-19: from medical intervention to social practice regression modeling strategies: with applications to linear models, logistic and ordinal regression, and survival analysis simulating duration data for the cox model importance of events per independent variable in proportional hazards regression analysis. ii. accuracy and precision of regression estimates key: cord-342357-g8m57t67 authors: cumbo, enzo; alessandro scardina, giuseppe title: management and use of filter masks in the “none-medical” population during the covid-19 period date: 2020-09-21 journal: saf sci doi: 10.1016/j.ssci.2020.104997 sha: doc_id: 342357 cord_uid: g8m57t67 sars-cov-2 has become a pandemic disease declared by the world health organization, consequently each nation has taken a series of actions managed by the government in order to prevent the spread of this dangerous virus. the most common countermeasure is the use of a mask that should cover the mouth and nose to filter the inhaled and exhaled air. those masks are medical devices that should be handled properly; unfortunately in our study, observation of the population during the so-called “phase 2” has very often shown an inappropriate use of any type of mask which reduces its effectiveness. the correct dissemination of adequate information on how to use the mask and the strict control by the government not only on staying on the street wearing masks but above all on how they should be worn, could have further reduced the spread of covid-19. in december 2019, new epidemic disease was reported in china, caused by a virus that belongs to the coronavidae called covid-19. this novel disease is nowadays well known as sars-cov-2 capable to cause a severe acute respiratory syndrome which is easily spread among people thanks to its human-to-human transmissibility. (1, 21, 1, 2) in the beginning, this disease represented a huge danger only for the entire china but very soon, because of the great amount of movement of people from china to other countries and vice versa sars-cov-2 have become a pandemic disease as declared from the world health organization (who). (27, 3) in an attempt to limit, as much as possible, the spread of this terrible disease, each nation has taken a number of government-run actions based on several factors. (18, 19, 4, 5) this includes a physical separation between citizens who, for example, in italy have been confined to their homes for a certain period with the possibility of going out only for mandatory reasons. (20, 6) after this period, a second phase emerged, during which it was possible to go out but following particular conditions such as the use of masks that would have limited the spread of covid-19 through the microdroplets emitted during breathing, coughing or phonation. (2, 3, 4, 5, 6, 26, 7, 8, 9, 10, 11, 12) the use of masks, which are medical devices, requires correct use, based on medical principles unfortunately not known by the whole population. (24, 25, 13, 14) this cultural deficiency, linked to the breathing difficulties caused by the use of this filter, has led to incorrect management of these important medical devices, facilitating the commission of errors that can make the masks ineffective or even dangerous because they can become a vehicle for the spread of the disease itself. (7, 8, 9, 10, 15, 16, 17, 18) in this study, conducted in italy during the so-called phase 2, the behavior of the population outside their homes was observed, focusing on how the mask was worn and managed. (11, 12, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 25) all data were collected in a period of 12 days from 9 am to 8 pm; children and people with special needs were excluded as well as citizen observed while they were inside their cars. the study was conducted on a sample of 1036 subjects observed in the street for 60 seconds each. most of the people observed were out of the shops waiting for their turn to enter and this facilitated the observation of the subjects who acted naturally not knowing they were being observed. the parameters examined were the following: the type of mask (surgical mask, filtering mask with valve like ffp2/ffp3 type, filtering mask like ffp2/ffp3 type without valve, self-built mask or replaced by cloth), correctness in wearing it (covering nose and chin), and management (touching or not the mask on the external surface). (23, 30, 26, 27) (see table 1 ) . all collected data were statistically analyzed by chi square test. out of a total of 1034 subjects observed, the following results were noted: 12 subjects were on the street without any mask, therefore the citizens who wore one were 1022; 622 people wore a surgical mask; 118 people wore a ffp2/ffp3 type filter mask without the valve, 129 people wore a ffp2/ffp3 type filter mask with valve, 153 people wore a clearly self-made mask with fabric or had fabrics such as scarves fitted in front of the mouth and/or nose. only 264 showed an exemplary behavior by wearing the mask correctly, covering the nose and chin, and only 336 people during the entire period of observation (60 seconds) did not touch it. (see table 2 ) the data collected show important results that indicate how citizens' behavior may not be perfectly correct; the use of a medical device, such as a mask, which has an extremely important role in preventing the spread of infections in the air, must comply with very precise principles. the filtering mask must be worn and managed very carefully, otherwise it completely loses its effectiveness, even if the filtering power is particularly high as on those ffp2 and ffp3. any type of mask must adhere perfectly to the nose and along its internal circumference, preventing air from passing sideways without any filtration. (28,31>>28,29) at the same time, the air emitted from the lungs should pass through the mask in order not to pollute the surrounding air. wearing a mask that does not adhere well to the face or even with the nose or mouth not covered properly, even makes the best device totally useless. data from this study showed that only 25.83% of subjects (264 out of 1022), observed for 60 seconds, had exemplary behavior. certainly the respiratory difficulty induced by the masks and the lack of the habit of wearing them regularly have contributed to this trend of the phenomenon. among the most noticed errors, regardless of the type of mask, the incorrectly covered nose was the most recorded, in fact 40.70% of the subjects belonging to the whole sample made this error. on the other hand, 20.74% of the total did not cover the chin well and 12.72% wore masks that left the nose and chin unsealed. by analyzing all the results in detail, taking into account the type of mask, the following data were recorded: surgical masks were the most observed in our study (60.86%) probably because they are the cheapest and easiest to find at just a certain moment like this unexpected pandemic which created a much higher demand for these devices than normal production and market presence. in addition, surgical masks are the lightest and therefore least annoying, especially for their lightness and the reduced impediment to the passage of inhaled and exhaled air. precisely because of their shape and manufacture, surgical masks seem to lend themselves very much to an incorrect way of wearing them with their noses exposed making them totally ineffective. in fact, only 31.18% wore them correctly and 224 subjects (36.01%) out of a total of 622 committed this behavioral error; 21.70% of the subjects with surgical mask instead did not cover the chin letting the unfiltered air pass at this point; 11.09% did not adequately cover their nose or chin. ffp2 / ffp3 masks without valve, i.e. those that require greater sacrifice both during inspiration and expiration, were noted on 118 subjects (11.54%) but only 13.55% of those who wore them he did it correctly; once again, the most common mistake was to leave the nose uncovered (41.52%) probably to resolve breathing difficulties. severe acute respiratory syndrome-related coronavirus the species and its viruses, a statement of the coronavirus study group or mascks safe practice or habit mask use, hand hygiene, and seasonal influenza like illness among young adults: a randomized intervention trial face mask use and control of respiratory virus transmission in households physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review respiratory protection against bioaerosols: literature review and research needs advice on the use of masks in the community setting in influenza a (h1n1) outbreaks. interim guidance airborne viruses, and how adequate are surgical masks? filter and leak penetration characteristics of a dust and mist filtering face piece performance of an n95 filtering facepiece particulate respirator and a surgical mask during human breathing: two pathways for particle penetration surgical mask filter and fit performance characteristics of face seal leakage in filtering facepieces effect of particle size on assessment of faceseal leakage national institute for occupational safety and health. us dhhs, public health service face seal leakage of half masks and surgical masks aerosol penetration and leakage characteristics of masks used in the health care industry isolation, quarantine, social distancing and community containment: pivotal role for old-style public health measures in the novel coronavirus (2019-ncov) outbreak public health and ethical considerations in planning for quarantine modelling strategies for controlling sars outbreaks public health measures to control the spread of the severe acute respiratory syndrome during the outbreak in toronto a novel coronavirus outbreak of global health concern australian government releases face masks to protect against coronavirus facemasks for the prevention of infection in healthcare and community settings respiratory virus shedding in exhaled breath and efficacy of face masks the severe acute respiratory syndrome: impact on travel and tourism a rapid systematic review of the efficacy of face masks and respirators against coronaviruses and other respiratory transmissible viruses for the community, healthcare workers and sick patients testing the efficacy of homemade masks: would they protect in an influenza pandemic? disaster medicine and public health preparedness simple respiratory protection-evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles. the annals of occupational hygiene use of cloth masks in the practice of infection control evidence and policy gaps a cluster randomised trial of cloth masks compared with medical masks in healthcare workers key: cord-322521-by0e6h7s authors: imbrie-moore, annabel m.; park, matthew h.; zhu, yuanjia; paulsen, michael j.; wang, hanjay; woo, y. joseph title: quadrupling the n95 supply during the covid-19 crisis with an innovative 3d-printed mask adaptor date: 2020-07-23 journal: healthcare (basel) doi: 10.3390/healthcare8030225 sha: doc_id: 322521 cord_uid: by0e6h7s the need for personal protective equipment during the covid-19 pandemic is far outstripping our ability to manufacture and distribute these supplies to hospitals. in particular, the medical n95 mask shortage is resulting in healthcare providers reusing masks or utilizing masks with filtration properties that do not meet medical n95 standards. we developed a solution for immediate use: a mask adaptor, outfitted with a quarter section of an n95 respirator that maintains the n95 seal standard, thereby quadrupling the n95 supply. a variety of designs were 3d-printed and optimized based on the following criteria: seal efficacy, filter surface area and n95 respirator multiplicity. the final design is reusable and features a 3d-printed soft silicone base as well as a rigid 3d-printed cartridge to seal one-quarter of a 3m 1860 n95 mask. our mask passed the computerized n95 fit test for six individuals. all files are publicly available with this publication. our design can provide immediate support for healthcare professionals in dire need of medical n95 masks by extending the current supply by a factor of four. in late 2019, an outbreak of severe pneumonia associated with influenza-like symptoms and an alarming mortality rate was discovered to be caused by the novel coronavirus, sars-cov-2 [1] . the resulting disease was termed covid-19. personal protective equipment (ppe), especially n95 respirators, are now in critically short supply in many parts of the world [2, 3] . the pandemic has become a major healthcare burden in many countries, and innovative solutions are required to mitigate the shortage of ppe in order to minimize disease spread and loss of life [4] . manufacturers are increasing production to meet demand for ppe but are limited by significant lead times. n95 respirators are a specialized type of fit-tested respiratory ppe designed to exclude over 95% of 0.3 µm particles [5] and are considered essential protection for healthcare workers against airborne viral particles [6] . although there are ongoing sterilization efforts for used n95 masks, more research is needed to confirm the efficacy of sterilization without affecting the filtration quality of n95 masks [7, 8] . additionally, there is ongoing work to alleviate ppe shortage using homemade masks and 3d-printed mask adaptors [9, 10] . previous 3d-printed mask adaptors feature reusable designs with a frame to secure a filter material. however, due to the use of low-filtration efficacy materials as well as imperfect seals around the filter material and/or the face, these previous solutions do not achieve a medical grade n95 standard. we aimed to develop an immediate solution to mitigate this shortage: healthcare 2020, 8, 225 2 of 6 a 3d-printed mask adaptor, outfitted with a sectioned portion of an n95 respirator, that maintains the n95 filtration standard and thereby multiplies the available number of masks. maintaining the n95 standard requires a novel mask adaptor design that conforms to the face and seals around each component of the mask and filter. the mask adaptor design was developed with a carbon m2 3d-printer (carbon, redwood city, ca, usa) using biocompatible silicone (sil 30, carbon, redwood city, ca, usa) and multipurpose polyurethane (mpu 100, carbon, redwood city, ca, usa) resins. only 1860 3m n95 masks (3m, saint paul, mn, usa) that could not be donated to the hospital were used for design development. at each iteration, the design was evaluated based on the following criteria: filter efficacy, filter surface area, and respirator multiplicity. in particular, our design goals were to properly seal all components to the n95 standard and to optimize filter surface area such that the mask maintains breathability while extending the multiplicative factor of a standard n95 respirator. filter efficacy was quantitatively evaluated using a computerized n95 fit test machine (portacount respirator fit tester, tsi inc., shoreview, mn, usa) that measures the concentration of particles leaking into the mask, either through the filter itself or through gaps around the mask components and in the face seal. respirator multiplicity-calculated as the number of masks produced from a single n95 mask-was balanced with the need for sufficient filter surface area for comfortable breathability. breathability was qualitatively evaluated as the number of hours a user could comfortably wear the mask; we qualitatively observed that with a cartridge design that enables a filter surface area of approximately one-quarter of the 1860 3m n95 mask, the breathability was such that a user could still wear the mask for a full workday. a sufficient seal of our mask to the user's face requires the mask to conform to a range of facial shapes, even while talking and moving. we selected the soft biocompatible silicone material for the base of the mask to perform this function. additionally, we utilized a teardrop shape rather than the 1860 n95 dome shape to conserve material and weight. the final silicone base design was also molded as a proof-of-concept to pursue alternative large-scale manufacturing solutions. for a manufacturing alternative, we used a three-part mold design with 30a shore hardness urethane (vytaflex 30, smooth-on, macungie, pa, usa). this molding alternative was a validation to confirm that our mask base geometry was compatible with traditional molding methodologies; if molding is desired for the final product, we recommend biocompatible silicones or urethanes with material properties similar to that of sil 30 (approximately 35a shore hardness). a 3d-printed rigid cartridge was developed to allow for a larger filter surface area and to facilitate single-use filter loading and unloading with the cutting and sealing process of the n95 mask sections performed separately. we designed the cartridges to follow the contour of the sectioned quarters of an n95 mask. non-toxic thermoplastic adhesive (all purpose glue, arrow fastener co., saddle brook, nj, usa) was used to seal the filter section to the cartridge on both sides. additionally, the cartridge features a flange that fits into an undersized slot in the silicone mask base, thus sealing the cartridge to the base without the need for adhesive. to validate that it is possible to maintain the n95 filter efficacy standard with our novel mask adaptor, the final prototype was tested on six individuals using the portacount computerized n95 fit test machine. the fit test was performed by affixing a probe to the filter section of the mask through which the machine measured the concentration of particles leaking into the mask. the fit tester machine quantitatively evaluates the preservation of mask functionality, including its ability to filter particles as well as the presence of any leaks in the mask adaptor components connecting the n95 filter section to the face. for each individual, a new filter and cleaned mask was provided. each test individual completed all four exercises: bending over, talking, and horizontal and vertical head motion. the final design features a rigid 3d-printed cartridge with an inner ridge used to seal one-quarter of a 3m 1860 n95 mask with non-toxic adhesive ( figure 1) . additionally, the design includes a 3d-printed soft silicone base with a slot that seals around the cartridge. the silicone base was successfully molded as a dimensionally accurate proof-of-concept mask produced using a conventional two-part molding resin. the full assembly of the mask is detailed in figure 2 . the first step is to carefully remove the metal nose strip and elastic straps from the original n95 mask, followed by cutting the mask along its horizontal and vertical axes; a 3d-printed stencil (file provided in the supplementary materials) can be used to assist this cutting. each mask quarter is placed in a cartridge face down and any asymmetries can be trimmed such that the filter section sits snug within the allotted grove of the cartridge. a non-toxic thermoplastic adhesive is then applied along the entirety of the ridge, sealing all gaps between the edge of the filter and the ridge of the cartridge. the filter assembly is then flipped face up and adhesive is again used to seal the mask section to the inner edge of the cartridge for a robust seal. to assemble the reusable silicone mask base, elastic straps are attached through the four fixation points. to insert a cartridge for use, all sides of the assembled cartridge slide into the slot in the mask base. quarter is placed in a cartridge face down and any asymmetries can be trimmed such that the filter section sits snug within the allotted grove of the cartridge. a non-toxic thermoplastic adhesive is then applied along the entirety of the ridge, sealing all gaps between the edge of the filter and the ridge of the cartridge. the filter assembly is then flipped face up and adhesive is again used to seal the mask section to the inner edge of the cartridge for a robust seal. to assemble the reusable silicone mask base, elastic straps are attached through the four fixation points. to insert a cartridge for use, all sides of the assembled cartridge slide into the slot in the mask base. figure 3 shows a user wearing the final mask. for testing, the quarter filter section of the mask was outfitted with the standard n95 fit test probe. the six individuals passed the computerized fit test wearing the mask. the portacount respirator fit tester measures the concentration of microscopic particles outside the mask and then measures the concentration that leaks inside the mask. the ratio of these two numbers is the fit factor, which is the standard for assessing a proper mask seal and is used annually to test for n95 mask fitness for healthcare workers at our institution. the overall fit factor measured was 148 ± 29, with 100 set as the standard pass level for an 1860 n95 mask. the respective scores for bending over, talking, horizontal and vertical head movements were 154 ± 49, 132 ± 38, 161 ± 38 and 169 ± 32. note that the scores outputted on the fit test machine as "200+" were counted as 200 for this test. is assembled separately with one-quarter of a 3m 1860 n95 mask and adhesive to ensure a seal on the edges of the filter. (d) back view of the final mask assembly. figure 3 shows a user wearing the final mask. for testing, the quarter filter section of the mask was outfitted with the standard n95 fit test probe. the six individuals passed the computerized fit test wearing the mask. the portacount respirator fit tester measures the concentration of microscopic particles outside the mask and then measures the concentration that leaks inside the mask. the ratio of these two numbers is the fit factor, which is the standard for assessing a proper mask seal and is used annually to test for n95 mask fitness for healthcare workers at our institution. the overall fit factor measured was 148 ± 29, with 100 set as the standard pass level for an 1860 n95 mask. the respective scores for bending over, talking, horizontal and vertical head movements were 154 ± 49, 132 ± 38, 161 ± 38 and 169 ± 32. note that the scores outputted on the fit test machine as "200+" were counted as 200 for this test. our novel 3d-printed mask adaptor and cartridge is designed to extend the supply of n95 masks in a cost-effective and scalable manner by dividing each n95 mask into four sections, thus quadrupling the supply. filter efficacy of the mask was quantitatively evaluated using a computerized n95 fit test machine, confirming the use of this mask adaptor design as a valid means of extending the mask supply while maintaining the n95 standard. each component of the mask can be produced through 3d-printing or molding modalities for large-scale production, and, if necessary, edited or scaled to help accommodate a wider range of faces. the filter cartridges can be separately assembled by adhering quartered sections of an n95 mask to the filter holder, which can then be supplied to the users. before each high-risk exposure, the cartridges have been designed to quickly assemble with the mask base, while properly maintaining its seal. the filter sections can be peeled from the cartridge, and the cartridges and mask base can both be sanitized for reuse; note that the mask components should be discarded if any warping occurs. the exact protocol of cartridge and mask reuse should be decided upon on an institutional basis. due to the immediacy of this ppe shortage, our primary goal was to rapidly develop a mask that satisfied n95 functional criteria while extending the existing mask supply. with the submission of this study, we will have included the files of our mask components so that individuals can use this work to alleviate mask shortages while making modifications to improve the fit, comfort and weight. just as healthcare workers must go through the fit test process with standard n95 masks to find the most appropriate mask shape that can properly seal to their face, the fit test would be necessary for users to confirm proper fit with our mask. in particular, fit factors for individuals vary across different n95 respirators [11] , and a follow-up study should be performed to optimize mask shape based on the fit factors measured across a random sampling of all healthcare workers. nonetheless, by including all 3d-printing files, institutions can make adjustments for individuals to customize the mask fit. we additionally intend to adjust our design for use with the 3m 1870 n95 mask, and we will continue to explore alternative designs to improve the speed and cost of manufacturing. in conclusion, to alleviate ppe shortage due to covid-19, we developed a mask adaptor system that can be outfitted with one-quarter of a section of an n95 mask while maintaining the standard level of seal. with this mask adaptor, we can effectively multiply the existing n95 supply to provide protection for frontline healthcare workers during this pandemic. china novel coronavirus investigating and research team a novel coronavirus from patients with pneumonia in china critical supply shortages-the need for ventilators and personal protective equipment during the covid-19 pandemic facemask shortage and the novel coronavirus disease (covid-19) outbreak: reflections on public health measures conserving supply of personal protective equipment-a call for ideas personal-protective-equipment-infection-control/n95-respirators-and-surgical-masks-face-masks association between 2019-ncov transmission and n95 respirator use hydrogen peroxide vapor sterilization of n95 respirators for reuse ultraviolet germicidal irradiation of influenza-contaminated n95 filtering facepiece respirators 3d printed surgical mask covid-19 digital manufacturing and 3d printing response: face mask application comparison of fit factors among healthcare providers working in the emergency department center before and after training with three types of n95 and higher filter respirators the authors declare no conflicts of interest.healthcare 2020, 8, 225 key: cord-334166-vll4s0xq authors: jones, huw as; salib, rami j; harries, philip g title: reducing aerosolised particles and droplet spread in endoscopic sinus surgery during covid‐19 date: 2020-08-15 journal: laryngoscope doi: 10.1002/lary.29065 sha: doc_id: 334166 cord_uid: vll4s0xq objectives: the presence of high sars‐cov‐2 viral loads in the upper airway, including the potential for aerosolised transmission of viral particles, has generated significant concern amongst otolaryngologists worldwide, particularly those performing endoscopic sinus surgery (ess). we evaluated a simple negative pressure mask technique to reduce viral exposure. methods: two models simulating respiratory droplets >5‐10 μm and fine respiratory nuclei <5 μm using fluorescein dye and wood smoke respectively were utilised in a fixed cadaveric study in a controlled environment. using ultra‐violet light, fluorescein droplet spread was assessed during simulated ess with powered microdebrider and powered drilling. wood smoke ejection was used to evaluate fine particulate escape from a negative pressure mask using digital subtraction image processing. results: the use of a negative pressure mask technique resulted in a 98% reduction in the fine particulate aerosol simulation, and eliminated larger respiratory droplet spread during simulated ess, including during external drill activation. conclusions: as global ent services resume routine elective operating, we demonstrate the potential use of a simple negative pressure mask technique to reduce the risk of viral exposure for the operator and theatre staff during ess. the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) responsible for the coronavirus disease 2019 was first reported in wuhan, china in december 2019 and has since a spread globally in a few short months 1 . at the time of writing, it has claimed nearly 500,000 lives 2 . thought to primarily spread via respiratory droplets from the upper respiratory tract 3, 4 , the nose and throat have consistently reported high viral loads 5, 6 . additionally, van doremalen et al demonstrated aerosolised sars-cov-2 remained viable for at least 3 hours 7 . the who defines respiratory droplets as particles >5-10µm, and respiratory nuclei <5µm 4 . although the primary route of spread is thought to be larger droplets, airborne transmission may be possible during procedures that generate large quantities of aerosolised viral particles 8 . although evidence of transmission to health care workers via aerosolised virus is difficult to prove, and evidence of aerosol transmission still debatable 9 , it would seem prudent for otolaryngologists to take steps to reduce exposure for theatre staff. [10] [11] [12] concern has thus been raised regarding the safety of otolaryngologists and theatre staff performing surgery within the upper airway, particularly when using powered instrumentation. both ent-uk and the american academy of otolaryngology-head and neck surgery recommended restriction of aerosol generating procedures (agp) for this reason 13, 14 . a few studies have sought to investigate this concern in a simulated setting and have demonstrated significant droplet spread during endoscopic sinus surgery, particularly when using powered drills 15, 16 . there is therefore an urgent need to develop interventions in order to mitigate these risks. using simulations of both aerosols and larger droplets in a cadaveric model, this study investigates the potential for a simple negative pressure mask technique to reduce the risk of intra-operative aerosol and droplet exposure for theatre staff. this article is protected by copyright. all rights reserved. the fixed specimen used in this study had prior consent for research photography. formal ethical approval for this study was not required as no living specimens were used. two models were utilised: smoke to simulate fine particle aerosolization, and fluorescein staining to simulate respiratory droplet spread. the study was conducted in university hospital southampton's anatomy laboratory on the same cadaveric specimen. we utilised a modified endoscopy mask (vbm medizintechnik gmbh ref 30-40-777, unit cost £31) originally designed for bronchoscopy, connected to a standard operating theatre suction unit operating at 200 mmhg ( figure 1 ). the membrane over the instrumentation port was widened to 3cm diameter allow the passage of a 4mm rigid endoscope and powered instruments). a wood smoker was used to generate high volumes of smoke expediently (sage bm600) utilising hickory wood chips. particle sizes produced during wood burning peak at 0.1-0.2µm and thus simulated respiratory nuclei 17 . the smoke was collected and siphoned into a bag-valve-mask respirator (bvm) (intersurgical uk). a size 7.5 endotracheal tube was inserted into the cadaver head's trachea in reverse and the cuff inflated. the mouth was occluded with gauze so that the only point of egress was the nose. the bvm bag was squeezed over 3 seconds until empty. five scenarios were tested: 1) a control with no mask, 2) mask fitted without suction, 3) mask fitted with suction, 4) mask fitted with suction, and instrument valve removed, 5) mask fitted with suction, instrument valve removed, and rigid endoscope in position. a digital camera with a cmos sensor of 24.1 megapixels yielded 6 images of 2.4 x 10 7 pixels during each scenario against a black background, with a noise reference image captured before each scenario. the images were processed in adobe photoshop 2020. a threshold filter was applied to each reference image to eliminate background noise and create an image of only black or white pixels. the image sequence in each scenario was stacked, a threshold filter applied to the same level, and the reference image subtracted to remove any confounding noise. white pixels were counted using imagej (imagej.nih.gov). this article is protected by copyright. all rights reserved. to simulate intra-operative droplet spread, a 1 litre solution of 1mg/ml fluorescein (alcon eye care uk ltd) was prepared. 100mls of this was instilled both into the nasal cavity, and via mini frontal trephines into the frontal sinuses. saturation was confirmed endoscopically using a blue filter 18 . the remaining 900mls was used for microdebrider and drill irrigation. the cadaver was placed in a standard supine operating position and the anatomy lab set up as a simulated operating theatre. the cadaver was covered in a blue, washable, drape and illuminated with an ultra violet led strip (wavelength 395-405nm). the drape was marked 10cm from the edge of the mask with tape for reference and was washed down between each scenario. a total of three scenarios were tested; 1) endoscopic sinus surgery (ess) (uncinectomy, middle meatal antrostomy, anterior & posterior ethmoidectomy, sphenoidotomy) using powered suction 4mm microdebrider (4 minute duration) with suction mask and repeated without, 2) powered drilling of the frontal recess and beak using a 12000 rpm 55 degree integrated suction cutting burr with suction mask and repeated without, 3) drill activation outside cadaver, within the mask aperture for 20 seconds with and without suction applied. all surgical simulations were performed by the same author (pgh). after each scenario the blue drape was inspected under uv light for droplet spread and photographed. in line with results from previous work by khoury 19 , we demonstrated a significant emission of aerosolised particles without a mask. table 1 summarises the white pixel count for the final subtraction image in each scenario. figure 2 demonstrates the image processing involved, with figure 3 depicting each subtraction image. scenario 2 demonstrated a good mask seal with no visible leak around the edge of the mask. applying a suction circuit to the mask resulted in a 98% reduction in the white pixel count. removal of the instrument valve entirely did not result in elevated aerosolised particles. the image for scenario 4 does demonstrate more smoke at the instrument valve aperture, but these particles were captured by the suction circuit and did not escape into the room. addition of an endoscope to the setup did not alter this. the residual white pixels in scenarios 3-5 were produced by motion artefact between image captures as evidenced by a fine white outline around the cadaver/mask. visual inspection of the images confirms no escaped particles. no fluorescein droplets were observed with or without the negative pressure mask during the simulation of powered microdebrider assisted ess. this comprised continuous microdebrider activation for 4 minutes whilst performing uncinectomy, middle meatal antrostomy, anterior and posterior ethmoidectomy, and sphenoidotomy. external droplet spread was observed up to the 10cm mark during the powered drilling simulation, despite the use of a cutting burr with integrated suction (figure 4) . however, when the procedure was repeated with the negative pressure mask, no contamination was observed. accidental external drill activation has been shown to cause gross contamination 20 . in the authors' experience, this most commonly occurs in close proximity to the nares during instrument insertion/removal. to simulate this we this article is protected by copyright. all rights reserved. activated the drill external to the cadaver, but within the mask instrument aperture, both with and without negative pressure. significant contamination was observed within the mask, but none was evident externally. table 2 summarises the results. this article is protected by copyright. all rights reserved. as our understanding of sars-cov-2 transmission evolves, adequate protection of hospital staff from both contracting the virus, and unwittingly acting as asymptomatic vectors, has become paramount. this is particularly so as the uk resumes elective ent services 21 including aerosol generating endoscopic procedures. this proof of concept study demonstrates that a negative pressure mask can effectively reduce both fine droplet nuclei aerosol and larger droplet spread during endoscopic sinus surgery using powered instruments. additionally we suggest that sealing the mask around the instruments may not be necessary which vastly improves the surgeon's range of movement. the use of a mask with a soft face seal also allows for the accommodation of multiple face shapes without needing to manufacture individualised systems. in recent months, several studies have sought to evaluate droplet spread during endoscopic sinus surgery 16, 19, 20, [22] [23] [24] [25] , but this model is the first to examine the performance of a negative pressure mask with both respiratory droplet and droplet nuclei simulations. in the only other study to use a smoke simulation of droplet nuclei, khoury et al. 19 used incense joss sticks to generate aerosol particles of diameter of 0.28 µm 26 . they also demonstrated that their negative airway pressure respirator (napr) was able to prevent aerosol escape. however, their image analysis differed in that they selected one image two thirds of the way through their scenarios for threshold analysis. in an effort to capture all of the particles emitted over each scenario, we stacked all of the captured images to form a composite. this allowed for greater sensitivity and analysis for any leaks that would be potentially missed by assessing only a single time point. despite this we demonstrated effective capture of aerosolised particles with a similar mask provided a suction circuit was in use. workman et al demonstrated significant fluorescein droplet spread in ess, particularly when using powered drills on the sphenoid rostrum and frontal beak for 10 second intervals 20 . they did not demonstrate external spread with the powered microdebrider and our experience concords with this. in a similar cadaveric study, sharma et al. again showed droplet spread with powered drill use, but also up to 6cm using a microdebrider for 10 minutes. gross this article is protected by copyright. all rights reserved. contamination up to 13cm was shown on external burr activation for 10 seconds 16 . we did not feel it necessary to repeat this scenario but were able to demonstrate that drill activation external to the nares, but within the mask instrument aperture, did not result in droplet spread beyond the confines of the mask, regardless of whether the suction circuit was activated. furthermore, helman et al. constructed a bespoke 3d printed mask using a cut surgical glove placed over the aperture as an instrument port, which successfully reduced fluorescein droplet spread by 86% when drilling in the anterior nasal cavity 22 . depending on the size of the mask aperture, this study suggests that covering it may not be necessary as no smoke or fluorescein spread were observed when the instrument valve was removed. this study has some limitations. it proved difficult to fully eliminate camera movement in our setup during each smoke scenario resulting in minor motion artefact (manifest as a fine white outline around the cadaver/mask in the subtraction images). this could be reduced with more robust equipment. the mask tested was not sterile, although it could easily be sterilised pre-operatively. we only tested a 4 minute period of powered instrument activation rather than a full duration ess. the smoke model did not allow for real time assessment of droplet nuclei generation during surgical instrumentation with the mask. repeating the experiment using an optical particle sizer would allow assessment of sub 10 µm particles generated during ess, and as such analysis of mask effectiveness at preventing external spread. this article is protected by copyright. all rights reserved. as global elective otolaryngology services resume, managing the risk of aerosolised coronavirus is paramount. this study demonstrates the effectiveness of a simple negative pressure mask in reducing droplets and respiratory nuclei generated during endoscopic sinus surgery, thus reducing potential exposure for both operator and theatre staff. this article is protected by copyright. all rights reserved. a novel coronavirus from patients with pneumonia in china coronavirus disease 2019 an overview of their replication and pathogenesis modes of transmission of virus causing covid-19: implications for ipc precaution recommendations viral load of sars-cov-2 in clinical samples. the lancet infectious diseases sars-cov-2 viral load in upper respiratory specimens of infected patients aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 world health organization. natural ventilation for infection control in health-care settings aerosol generating procedures and infective risk to healthcare workers: sars-cov-2 -the limits of the evidence. the journal of hospital infection personal protection and delivery of rhinologic and endoscopic skull base procedures during the covid-19 outbreak rhinologic procedures in the era of covid-19: health-care provider protection protocol rhinologic practice special considerations during covid-19: visit planning, personal protective equipment, testing, and environmental controls new recommendations regarding urgent and nonurgent patient care | american academy of otolaryngology-head and neck surgery airborne aerosol generation during endonasal procedures in the era of covid-19: risks and recommendations. otolaryngology -head and neck surgery (united states) cadaveric simulation of endoscopic endonasal procedures: analysis of droplet splatter patterns during the covid-19 pandemic size and composition distribution of fine particulate matter emitted from wood burning, meat charbroiling, and cigarettes. environmental science and technology an inexpensive blue filter for fluorescein-assisted repair of cerebrospinal fluid rhinorrhea aerosolized particle reduction: a novel cadaveric model and a negative airway pressure respirator (napr) system to protect health care workers from covid-19 endonasal instrumentation and aerosolization risk in the era of covid-19: simulation, literature review, and proposed mitigation strategies. international forum of allergy and rhinology exiting the pandemic 3: a graduated return to elective ent within the covid-19 pandemic ventilated upper airway endoscopic endonasal procedure mask: surgical safety in the covid-19 era. operative neurosurgery endoscopic skull base and transoral surgery during the covid-19 pandemic: minimizing droplet spread with a negative-pressure otolaryngology viral isolation drape (novid). head and neck endoscopic skull base surgery protocol from the frontlines: transnasal surgery during the covid-19 pandemic application of a modified endoscopy face mask for flexible laryngoscopy during the covid-19 pandemic incense smoke: characterization and dynamics in indoor environments the authors wish to thank dr david walker & ellen adams of the centre for learning anatomical sciences at university of southampton for their support and specimen preparation. simon charters of the medical photography department at queen alexandra hospital, portsmouth photography dept for his post processing advice. richard towler, hospital sales director freelance surgical ltd for supplying the vbm mask samples. key: cord-326565-s62inw07 authors: shacham, e.; scroggins, s.; ellis, m.; garza, a. title: association of county-wide mask ordinances with reductions in daily covid-19 incident case growth in a midwestern region over 12 weeks date: 2020-10-30 journal: nan doi: 10.1101/2020.10.28.20221705 sha: doc_id: 326565 cord_uid: s62inw07 importance: this study assessed the longitudinal impact of new covid-19 cases when a mask ordinance was implemented in 2 of a 5-county midwestern u.s. metropolitan region over a 3-month period of time. reduction in case growth was significant and reduced infection inequities by race and population density. objective: the objective of this study was to assess the impact that a mandatory mask wearing requirement had on the rate of covid-19 infections by comparing counties with a mandatory policy with those neighboring counties without a mandatory masking policy. design: this was a quasi-experimental longitudinal study conducted over the period of june 12-september 25, 2020. setting: this study was a population-based study. data were abstracted from local health department reports of covid-19 cases. participants: raw cases reported to the county health departments and abstracted for this study; census-level data were synthesized to address county-level population, income and race. intervention(s) (for clinical trials) or exposure(s) (for observational studies): the essential features of this intervention was an instituted mask mandate that occurred in st. louis city and st. louis county over a 12 week period. main outcome(s) and measure(s): the primary study outcome measurement was daily covid-19 infection growth rate. the mask mandate was hypothesized to lower daily infection growth rate. results: over the 15-week period, the average daily percent growth of reported covid-19 cases across all five counties was 1.81% (sd 1.62%). the average daily percent growth in incident covid-19 cases was similar between m+ and mcounties in the 3 weeks prior to implementation of mandatory mask policies (0.90% [sd 0.68] vs. 1.27% [sd 1.23%], respectively, p=0.269). crude modeling with a difference-in-difference indicator showed that after 3 weeks of mask mandate implementation, m+ counties had a daily percent covid-19 growth rate that was 1.32 times lower, or a 32% decrease. at 12 weeks post-mask policy implementation, the average daily covid-19 case growth among mwas 2.42% (sd 1.92), and was significantly higher than the average daily covid case growth among m+ counties (1.36% (sd 0.96%)) (p<0.001). a significant negative association was identified among counties between percent growth of covid-19 cases and percent racial minorities per county (p<0.001), as well as population density (p<0.001). conclusions and relevance: these data demonstrate that county-level mask mandates were associated with significantly lower incident covid-19 case growth over time, compared to neighboring counties that did not implement a mask mandate. the results highlight the swiftness of how a mask ordinance can impact the trajectory of infection rate growth. another notable finding was that following implementation of mask mandates, the disparity of infection rate by race and population density was no longer significant, suggesting that regional-level policies can not only slow the spread of covid-19, but simultaneously create more equal environment. covid-19 has claimed over 210,000 lives in the u.s. 1 while urgent policies have been implemented to reduce covid-19 infections throughout the pandemic, there has been significant variability across state and local governments. in particular, due to the difficulty in maintaining social distancing guidelines and in an attempt to allow the economy to recover by opening businesses, some elected officials have issued mask mandates for the public to reduce covid-19 transmission. research has demonstrated the effectiveness of masks in preventing the spread of infectious diseases through airborne droplets, 2 yet the majority of a community would need to be masked in order to reduce infection rates. several governors have avoided state-level mandates by rationalizing that within-state variations of covid-19 infection rates call for more localized public health policymaking than state-wide orders. 3 while studies found mask policies to be effective in reducing infection growth rates early in the pandemic, there is an urgent need to know how the impact of such policy persists over time; in addition, the impact on unequal infection rates such as higher rates reported among african-american/black and hispanic/latinx populations. 1 mask wearing has transitioned to a politically nuanced behavior, and this has been particularly true in the region surrounding the midwestern city of st. louis, providing a natural experiment to understand the longitudinal impact of a variable mask mandate policies has on county-level changes in incident covid-19 rates over a 12-week period. this ecological study evaluated the effects of a public mask mandate on the daily cumulative case growth of covid-19 infections among five neighboring counties within the metropolitan statistical area of saint louis, missouri: city of st. louis, st. louis county, jefferson county, saint charles county, and franklin county. the study period included a three-week period prior all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted october 30, 2020. ; https://doi.org/10.1101/2020.10.28.20221705 doi: medrxiv preprint to the implementation of a mandatory mask order in st. louis city and county on july 3, 2020, and a 12-week post-implementation period, for a total of 15 weeks. the primary outcome of interest was the cumulative daily percent change of reported covid-19 cases by county. daily incident covid-19 cases were sourced from publicly available data provided by the missouri department of health and senior services. presence of a mask ordinance was the primary predictor of interest. among the five counties, two implemented a mask ordinance during the study period for individuals entering public indoor spaces; the city and county of saint louis 4 (m+), with three counties having no such mandate during the study period (m-). as covid-19 infections occur more often among areas with higher county-level population density per square mile, higher proportion of residents identifying as non-white, and lower median annual household income, 25,6 these variables were included from the 2018, 5-year american community survey to control for variations in covid-19 case growth. data were constructed with daily percent changes in covid-19 cases as a function of time (daily) and location (county), with 530 unique observations from june 12, 2020 to september 25, 2020. the average percent change in cases per day was calculated across m+ and mcounties to understand the pattern of covid-19 growth throughout the study period. kendal's tau-b rank correlation test was employed to identify associations among county-level demographics and percent daily growth of covid-19 cases. all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted october 30, 2020. ; https://doi.org/10.1101/2020.10.28.20221705 doi: medrxiv preprint a difference-in-difference (did) framework was employed to evaluate the effect of mask ordinances on percent daily growth in covid-19 prevalence. specific to this study, a did estimator (δ) was calculated using binary dummy variables for both treatment (m+ or m-) at time (prior to mask ordinance implementation and after implementation). the calculated did estimator was then applied to a linear probability model to determine the effects of a mask ordinance on covid-19 case growth. four adjusted models were constructed, accounting for county-level characteristics, each at 3 week intervals past the implementation date. statistical analyses were completed using r 4.0 software with significance determined at α = 0.05. over the 15-week period, the average daily percent growth of reported covid-19 cases across all five counties was 1.81%(±1.62%). a total of 44,294 cases were reported throughout this period among a total estimated population of just over 2,000,000 residents, which is approximately one-third of the population within the state of missouri. in adjusted linear probability models (table 1) , the mask mandate was found to be significantly associated with slowing the reported growth of daily covid-19 cases across the study period. all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted october 30, 2020. ; https://doi.org/10.1101/2020.10.28.20221705 doi: medrxiv preprint from 3 weeks pre-policy to 3 weeks post-policy, m+ counties had a daily average covid-19 growth rate of 44% less than m-counties (1.08/2.44). at week 6, 9, and 12 assessments, modeling revealed a continuing significant reduction in covid-19 cases in counties with mask mandates. from pre-policy to 12 weeks post-policy (figure 2) , m+ counties had a daily average covid-19 growth rate of 40% less than of m-counties (0.47/1.16). using the did linear probability equation, a counterfactual line is estimated, indicating probable growth of counties with mask mandate had a mask mandate not been implemented. within the adjusted models, accounting for the did estimator, proportion non-white population and population density were negatively associated with increased daily growth rate, yet median income did not contribute significantly to any of the calculated models. this longitudinal study demonstrates that the implementation of county-level mask mandates lowered incident covid-19 case growth over time, compared to neighboring counties with no such mask mandate. importantly, the results highlight the swiftness of such impact, with significant effects seen at just 3 weeks post-implementation. as time progressed, this impact was slightly reduced, possibly due to the arbitrary political borders of counties and states, which do not necessarily constrain transmission as mobility across mask mandate and non-mandated regions occurs. although broader state or national mandatory mask ordinances would likely have a significant reduction in covid-19 infections, in their absence, support for governors and elected officials to minimize the interactions across these borders may be beneficial. furthermore, implementation of a mask mandate may have reduced the unequal burden on african american/black and hispanic/latinx individuals, as well as areas with higher population density. covid-19 has highlighted the impact and swiftness of racial and ethnic inequities through higher rates of covid-19 morbidity and mortality among non-white communities. in particular, many individuals were unable to abide by stay-at-home orders that protected middle all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted october 30, 2020. ; https://doi.org/10.1101/2020.10.28.20221705 doi: medrxiv preprint and high-income communities as a result of "essential" employment in grocery stores, health care support positions, and public transportation. these jobs, often lacking ppe and paid sick leave, are more often filled by people of color, living in higher population density and lower socioeconomic areas. 7 the mask policy that was enacted in many communities may have provided a more equal approach to reducing covid-19 infections, as it occurred in st. louis, all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. use of facemasks to limit covid-19 transmission community use of face masks and covid-19: evidence from a natural experiment of state mandates in the us. health aff (millwood) covid-19 and the us response: accelerating health inequities covid-19 exacerbating inequalities in the us association of mobile phone location data indications of travel and stay-at-home mandates with covid-19 infection rates in the us key: cord-345883-ncot7tvn authors: hansstein, francesca valeria; echegaray, fabián title: exploring motivations behind pollution-mask use in a sample of young adults in urban china date: 2018-12-04 journal: global health doi: 10.1186/s12992-018-0441-y sha: doc_id: 345883 cord_uid: ncot7tvn background: wearing a pollution mask is an effective, practical, and economic way to prevent the inhalation of dangerous particulate matter (pm). however, it is not uncommon to observe negligence in adopting such behaviour, and this especially among young segments of the population. using the theory of planned behaviour (tpb) as conceptual framework, this study explores the role of socio-cognitive factors that affect the decision of wearing a pollution mask in the context of young educated people. this is done by selecting a sample of college students in urban china, a country that has seen air quality as one of the major challenges in the last decades. while young urban college students might be expected to be receptive to standard attempts to be influenced through reason-based cognitive stimuli, it is often found that this is not the case. the empirical analysis was articulated it in two steps. structural equation modelling (sem) was first used to examine the relationships among the conceptual constructs derived from the tpb conceptual model, and second step-wise ordinary least squares regressions (swols) were employed to observe the partial effect played by each item on the decision to wear a mask. results: results show that, while reason-based stimuli play a role, attitude, social norm, and self-efficacy were the most important predictors of the behavioural intention (p < 0.01). the role of past behaviour was also acknowledged as strongly associated with the dependent variable (p < 0.01). overall, the likelihood of wearing a pollution mask increases with the importance of others socio-cognitive and psychological factors, which could help understand behavioural biases, and explain the relative role of several mechanisms behind the decision to wear a mask. conclusions: while tackling pollution requires multiple and synergic approaches, encouraging self-prevention using pollution mask is a simple and effective action, implementable at negligible costs. resistance among younger, well-educated cohorts to wear masks can be overcome by stressing the social desirability of action and the sense of empowerment derived from its usage. this study has the potential to inform policies aimed at changing suboptimal behavioural attitudes by identifying triggers for change, and it could serve in improving the tailoring of health promotion messages aimed at nudging healthy behaviour. electronic supplementary material: the online version of this article (10.1186/s12992-018-0441-y) contains supplementary material, which is available to authorized users. since the beginning of its rapid economic development, china started experiencing one of the worst air pollution emergencies in the world's history, affecting especially urban areas and that has become one of the leading threats to public health [1, 2] . according to the yale and columbia university's environmental performance index, and with the exception of a handful of poor nations, china's pollution trails all developed and developing countries, and ranked second to last in air quality [3] . particulate matter of inhalable and respirable size fractions (i.e. pm10 and pm2.5) represents the air pollutant of greatest health concern in urban china [4, 5] due to their microscopic size particles of this nature easily enter the human respiratory system, contributing to respiratory illnesses.. moreover, prolonged exposure to air pollution has negative effects on cognitive abilities later in life [6] , whereas expecting mothers can experience a higher frequency of pregnancy complications related to excessive exposure to pm [7] . in terms of tangible health effects caused by pollution, low-educated and elderly females are the most vulnerable population segment [8] . in addition to the negative effects on individual health, air pollution represents a direct drag on public resources by rising costs for the health system, and an indirect hindrance to the economic and social order by incentivizing mass emigration. in 2016, the chinese government has launched a five-year plan to radically tighten air pollution and initiated a process of green growth and development. during the asia-pacific economic cooperation in 2014, the chinese government successfully implemented rigorous emission reduction initiatives to lower air pollution levels in the city of beijing [9, 10] . the experiment achieved excellent results, demonstrating that pollution can be tackled with adequate policy measures. however, the positive effects of these measures on health are likely to emerge in the long-run. far less clear is government success in redressing pollution effects upon individuals and in affecting individuals to responsibly handle preventive health measures when dealing with pollution. the chinese government took in fact several initiatives and leveraged on mass media dissemination to encourage prevention against pollution. these included, for example, the daily reporting of environmental conditions, the dissemination of scientific knowledge about the adverse effects of pollution exposure, advising sensitive groups like the elderly, children, or people with respiratory diseases against spending long periods outdoors and several others. among the solutions to reduce exposure to air pollution are: (a) staying indoors with air purifiers, (b) avoiding physical activity during severely polluted days, and (c) reducing frying of food and smoking at home. one of the most effective alternatives to reducing personal exposure to particulate matter, specifically outdoors, is also wearing a pollution mask. the promotion of pollution mask wearing has been one of the core government-initiated programs to guide individual responses to pollution exposures. however, in spite of public promotion, being a practical and straightforward form of self-prevention, as well as one of the cheapest, it is found that a large number of individuals do not wear a pollution mask during polluted days. this resistance is stronger among the youngest and best educated people of big cities in the country, who interestingly are also the ones more easily targeted by those initiatives of government officials aiming at a wide dissemination of information, warnings, and best practices to protect against pollution [11] . this is puzzling to some extent, and suggests that, because of the extreme cost effectiveness and accessibility to masks, most of the impediments to adopt such a healthy habit are likely to be found in behaviours informed and conditioned by individual attitudes and social pressure. moreover, the efficacy of facemasks in preventing the inhalation of pm has been successfully tested, and previous research has shown that there are immediate positive outcomes on blood pressure and heart rate [12] . finally, masks are a useful tool to protect individuals from the transmission of acute respiratory infections and pandemic influenza [13] . however, to our knowledge, there is no study documenting the reasons for the lack of adherence to mask-wearing registered especially among the youngest population. this paper aims at filling this gap, and provides empirical evidence gauging the relative contribution of extra-cognition stimuli in driving accurate preventive behaviours regarding pollution facemask use among young, well-educated, and urban chinese population. this is the population segment with the greatest resistance to adopt risk-averse health practices when dealing with pollution. to conduct the empirical investigation, the theory of planned behaviour (tpb) was applied to determine the role that socio-cognitive factors play on the decision of wearing a pollution mask among a sample of chinese students. at this scope, two quantitative analyses were employed. the first is based on structural equation modelling (sem); this methodology was used to examine the relationships among conceptual constructs measuring the intention to wear a mask. the second model used step-wise ordinary least squares regressions (swols) to estimate the marginal effect of each item, identified at the sem stage, on mask wearing intention. beyond simple utility-based rational models of behaviours, the literature acknowledges a diversity of reasons behind the use of facemasks. awareness of adverse consequences towards future health, as well as raw fears for personal wellbeing, are among the more emotional forces reported by the literature [14, 15] to trigger the use of facemasks. likewise, environmental conditions also seem to drive behaviours, given that a 100-point increase in the air quality index (aqi) has been linked to an increase in the purchase of facemasks by 54.5% and anti-pm2.5 masks by 70.6%; in fact, the search of the word "mask" (口罩 in chinese) on internet search engines escalated in days with a high the aqi [16] . emotional reactions are fed by perceived effects of air pollution which implies that individuals first and foremost develop attitudes based on perceptions and assess the extent to which the target behaviour is within their reach. additionally, the elasticity of demand for face mask suggests that affordability issues do not impair individuals from adopting the behaviour if they want so, in other words, they don't feel disempowered to perform the action. given the shortcomings of cognitive modelling of action for facemask use, socio-psychological stimuli should be recognized as influential like how individuals perceive the legitimacy of performing the target behaviour, their ability and capacity to do so, and how this target behaviour is associated with positive feelings. the theory of planned behaviour (tpb) [17] assumes that individuals make choices based on weighting the possibilities and obstacles to enact the expected action, and thus building a sense of confidence in actually achieving desired results, their broader feelings towards the action at stake, and their surrounding social context. other forces may be at play as well such as their past reactions to similar situations. previous research had proven the validity of the theory-based psychological models in explaining the intention to take preventive measure for limiting the health effects of air pollution [18, 19] . our hypothesis is that other influences like the prevailing social norms, inertial reactions replicating past behaviours, and the perceived feasibility of implementing new behaviours have also a role in making sense of unhealthy personal choices. tpb proposes that behavioural intention is determined by attitude towards the behaviour, subjective or social norm, and perceived behavioural control (pbc). three types of perceptions influence involvement with the target action: (a) the perceptions of how socially acceptable or mandatory the intended behaviour among individual's salient reference groups is (i.e., social norms); (b) the perceptions of how easy or hard it is to set such behaviour in motion, in other words, the perceived capacity of overcoming barriersor to take advantage of facilitatorsto engage the behaviour (i.e., pbc); (c) and lastly the perceptions of how likeable or unwanted the intended behaviour pictured in people's minds is, mostly based on the perceived relevance and payoffs of the consequences of enacting such behaviour (attitudes) [20, 21] . tpb is one of the most widely applied theories for health prevention, while also contributing to the understanding and overcoming of behavioural-change resistance [22] (fig. 1 ). this study employed an exploratory sequential mixed methods research design. a preliminary qualitative phase on a small sample of the target population -to elicit the salient beliefs towards the behaviour and to build the questionnaire -was followed by data collection and the quantitative analysis. qualitative research also enabled the validation of how expressions of social norms, perceived behavioural control and attitudes towards mask use actually play a role in students' calculus of mask use, together with the recognition of other forces influencing choice such as past behaviours, that is, the influence of inertial behaviour. to evaluate the appropriateness of the questionnaire items, a principal component factor analysis was first performed, and, as a second step, the model constructs were built using the mean score method. in particular, for each respondent, one score was calculated as the mean of the answers to the items. the main difference between factor-score and mean-score method is that mean score assumes that each item is equally important to the concept being measured, while factor score does not. in our analysis, the assumption was met so constructs were calculated using the mean score method. in addition, the interpretation of the mean score is straightforward because each construct has the original scale used for the items. secondly, the mean score manages missing values more efficiently [23] . the dependent variable of this study was measured based on respondents' degree of agreement towards seven different behavioural reactions all connected to wearing a pollution mask when confronted with a very specific situation which is "if the aqi is higher than 200 and i have to stay outdoors for more than one hour". it is fair to acknowledge that the average aqi during fieldwork did not reach 200. those seven reactions related to 1) expecting, 2) wanting, 3) choosing, 4) intending, 5) preferring, 6) suitability, and 7) future commitment to use a mask. a seven-point likert scale was used to identify the level of agreement with each reaction. to account for the nominal heterogeneity behind construct's content, the measure included a variety of states which demand different intensity of individual commitment to action. all reactions cluster together yielding a high cronbach's alpha reliability index of 0.94. accordingly, the intention to behave construct is thereby robustly measured. the need for specifying in greater detail the exact context of performing the action (that is, reaching aqi higher than 200) derived from the former round of qualitative research which clearly suggested that a context-free assessment of pollution-related preventive behaviours would have led to a problematic unbinding of the action, which in turn stimulated overstatements about individual unwillingness to adopt health-conscious practices. the other measures of the standard tpb model also followed a multi-item construct composition. attitudes towards the behaviour aims to measure the perceived consequences and value of performing the action and thus was measured using a seven-point likert scale that grasped the agreement with the idea of wearing a mask as 1) necessary, 2) effective, 3) beneficial, and 4) useful. except for the latter item which loads at 0.57, all other items have a high correlation to the latent trait, and therefore contribute to yielding a valid and reliable construct. cronbach's alpha for the construct was 0.76. social norms capture the surrounding environment of pressures and conformity to other people's expectations with regards to using a facemask against pollution, thus it was measured as the perceived reaction of four groups: 1) parents, 2) friends, 3) schoolmates, and 4) roommates to that behaviour, using a seven-point likert agreement scale. the inter-item correlation was sufficiently high to yield a highly satisfactory cronbach alpha coefficient of 0.80. our study also included questions for perceived behavioural control (pbc) and self-efficacy. pbc relates to the possibilities that action could be performed in practical terms and the degree of confidence that initiatives taken will amount to the desired behaviour and the expected outcomes from it. self -efficacy is a key factor in explaining the adoption of health-related behaviours and is in fact always included in many health behavioural models [24] . although there are criticisms in the literature towards the measurement redundancy of pbc and self-efficacy [25] constructs were kept separated in this research following the approach of similar studies examining health behaviours or college students [26, 27] . these studies effectively demonstrated the separability of the two concepts: one side there is the perceived confidence in individual ability to achieve the behavioural outcome, on the other the belief that the outcome can successfully be influenced by one's own effort. from an empirical point of view, in our study, while pbc measured the role of objective obstacles (like accessibility and affordability), the question on self-efficacy was intended to measure the general subjective evaluation on oneself capacity to succeed in performing the specific task, which is not just simply wearing a mask, but also adopting self-preventive behaviours. buying an anti-pollution mask on campus is a relatively easy task -therefore unrelated to individual self-efficacy. it seems reasonable to acknowledge that a simple task like buying a mask cannot necessarily affect the target behaviour whereas the belief that wearing a mask can successfully protect ones' health may drive the behavioural intention. this was also confirmed by the low correlation between the pbc and self-efficacy items (r = 0.32). lastly, in order to better specify the model and given its weight in shaping health prevention choices past behaviour was also included in the analysis. this choice integrates the role of habits and, mainly, prior experience. a meta-analysis research on health behavioural determinants has shown how the addition of past behaviour increased by 19% the variance explained by the core constructs. when possible, the inclusion of past behaviour is recommended for a better model's specification and more precision in coefficient estimation. it captures the essential role of habit in shaping the behavioural intention and it has also found to attenuate the role of other attitude [28] . past behaviour was measured asking first: in the last year (s), did you wear a pollution mask during high polluted days? and then for those who answered positively, the variable's frequency was recoded to be consistent with the other constructs (how often, from never to always). the questionnaire was administered in chinese and was translated into english for dataset building and data analysis purposes (see additional file 1 for more information). survey data were collected between nov 27 and nov 30, 2015, and a total of 407 respondents participated in the study. of these, 386 completed the questionnaire, thus leading to a completion rate of 95%. during the days of data collection, the average aqi was 121.5 (respectively 85, 112, 110 and 179). for this average aqi level government indicates that slight irritations may occur; individuals with breathing or heart problems should reduce outdoor activities. this study employed a convenient sample, and participants were recruited among students living on campus in shanghai. although this choice can introduce a bias in the generalization of the results, the primary goal of this study is to study the factors affecting the behaviour within an educated and urban sample of chinese young individuals. a more detailed discussion about the use of convenience samples can be found in the discussion. informed consent was obtained from all participants included in the study. interviewers were properly trained on how to conduct the survey and responses were collected via self-administered questionnaires. also, the interviewers were reachable anytime in case the respondents needed some clarification. this procedure left respondents the privacy to reflect and answer the questions, and, at the same time, guaranteed the comprehension of the items in case they needed clarifications. table 1 reports a detailed description of the variables used to calculate the model constructs, together with the cronbach's alpha and factor loadings for each item. cronbach's alpha is a measure of internal consistency and indicates whether a measure is one-dimensional. the minimum standard accepted threshold is 0.7. similarly, factor loadings indicate how much variability of each item is correlated to the latent construct (in this case, factor 1), with values above 0.63 it is considered very good [29] . descriptive statistics were first calculated to determine the distributions of the core model constructs. structural equation models in the form of path analyses were performed to evaluate the relative impact of each construct on the intention to wear a pollution mask. the fit of the model was assessed through the examination of these fit indices: chi2 test, the comparative fix index (cfi) and the root mean square error of approximation (rmsea). table 2 presents the descriptive statistics of the core variables. overall, 53% of respondents were females, and 47% males; 77% came from urban areas, and 33% had a rural origin. respondents were on average 22 years old. although the mean value of the construct intention was quite high (5.13), the average of the frequency with which respondents used a facemask in the past was quite low (3.46). subjective norm, attitude, self-efficacy, and pbc were also relatively high. the next step was to estimate the structural equation model in the form of path analysis using maximum likelihood method. the model with standardized coefficients and p-values is reported in fig. 2 . except for pbc, attitude, social norm, and self-efficacy were all statistically associated with behavioural intention (their coefficients were, respectively β a➔i = 0.2, β sn➔i = .21, and β se➔i = 0.47, p < 0.01). in the model' s structure, past behaviour was employed as a proxy for actual behaviour. the path connecting intention to behaviour was units, as in our case, it is very common to obtain a significant chi-square, even when the model is accurate [30] . therefore, other fit indices should be considered. the cfi is above 0.90 indicates that our model does 92% better than a null model that assumes that all the coefficients are unrelated to each other, but the ramsea not below the recommended 0.1. in order to observe how each model factor affected intention, ols stepwise regression models were successively run. as reported in table 3 , each model adds a new predictor in the specification. as long as more constructs were included in the model, the r-squared substantially improved, going from r 2 = 0.119 in model 1 where only attitude was included, to r 2 = 0.416 in model 4 were all the predictors were added. attitude, social norm, self-efficacy, and past behaviour were all positively related to the intention of wearing a pollution mask and also highly significant (specifically, β a = 0.23, p < 0.01, β sn = 0.37, p < 0.01, β sn = 0.32, p < 0.01, β pb = 0.12, p < 0.01). pbc was instead not significantly correlated with intention. with the worsening of the air quality, the chinese population' s awareness of both the issue itself and its health consequences has rapidly increased [31] . underperformance of risk-averse behaviour seems more acute among a human asset of crucial importance for the country: its college-level generation. this paper was intended to describe the effects of a wider set of influences beyond information exposure to understand the actual triggers which are more likely to favor the intention of wearing a pollution mask. highly educated individuals, i.e., young college students, a segment of the population which is plausibly quite able to understand and assimilate cost-benefit analysis and efficiently conduct the rational processing of scientific information would be expected to respond positively to reason-based cognitive stimuli. yet, social norms, self-efficacy, attitudes, and past behaviour, all clearly played a critically important role in the decision of wearing a mask. our findings suggest that young chinese college students condition their use of pollution mask to what their social circle think of it, in particular friends and roommates. the social legitimacy of this action is a critical shaper of their intentions. accordingly a language and approach that reinforces social adequacy and "coolness" of the target behaviour may prove effective in mobilizing facemask use through peer-pressure. this finding falls in line with studies showing how social pressure critically influenced mask wearing during the outbreak of sars [32] as well as for favouring other health prevention measures especially among youngest cohorts [33] and during quarantine times [34] . an individual's perception of his/her competence to enact the action is also critical, as epitomized by the high loading of the self-efficacy variable. interestingly, this effect runs independently of individual perception of external obstacles or facilitators to attain the ultimate result. this finding echoes other studies analysing the role of self-efficacy in following preventive behaviours [35, 36] . accordingly, appealing to this sense of impact of one' s confidence in implementing the behaviur is critical to scaling up facemask use. conversely, given that wearing a pollution mask requires little volitional control, behaviour control-related barriers like price, quality, and brand recommendation hardly determines the odds of performing the target behaviour. naturally, the practical irrelevance of tpb for facemask use cannot be extended to other health prevention behaviors. in fact, tpb has proved greatly effective in shaping early cancer screenings and use of seat-belts [37] . our study also confirmed the importance of past behaviour which, in this case, strengthens the relationship between intention and behaviour by acting as an intention stabilizer. in general, the inclusion of past behaviour had been shown to improve the prediction of future behaviour and, also, had sometimes been found to be the only significant predictor [28] . this validates the analytical gains of putting behavioural change into a broader and more realistic context than merely knowledge exposure. it also signals the potential advantages of identifying a more effective mobilizational language to encourage a wider embracement of the proposed action. in the health promotion literature, there are several examples on how by slightly changing behavioural triggers, or by adding almost-invisible nudges, individuals are more likely going to adopt healthier behaviours [38] . past evidence has proven how public health programs aimed at increasing the adoption of preventive behaviour are more successful when the health intervention design includes the understanding of the complexity of the behavioural determinants [36] . the variations in individual responses to smog are also critical to the development of adequate public policies, as well as interventions to promote changes in behaviours [39, 40] . besides government and universities' actions aimed at reducing pollution levels by rackling the sources of it, self-protection measures are taken at the individual level, and are not homogenous among different echelons of the society. a recent study from zhang et al. [16] found for example that richer and urban chinese are much more likely willing to invest in anti-pollution masks and air-filters. our study suggests that knowledge-intensive approaches to mobilize individuals towards new health-preventive behaviours do not warrant successful results. to succeed, government and institutional programs are required to support the adoption of new habits by framing them in a language of social legitimacy, that is, by building a narrative of the expected behaviour that socially relevant references (peers) demand from the individual or in terms of levelling up with the socially acceptable behaviour already set in practice by relevant personal references (legitimacy). communication approaches that motivate mask-wearing in social neighbours or convoke to champion one's social circle by meeting loved ones' expectations to take care of one's health may prove effective. a language around social comparisons may thus prove effective. consequently, given the salience of social norms (particularly among educated youngsters) using celebrities, key opinion leaders, or authoritative spoke-persons to highlight the reputation gains of adopting new behaviours (or the embarrassment of not doing so) can help overcome resistance or indifference. conversely, our results suggest that it might be pointless to emphasize exclusively accessibility of affordability issues, or execute any action on those table 3 step-wise ols regression, beta and standard errors in parenthesis controls for gender, residency, and age were also included notes: beta and se; *** p-values < 0.01 domains, as these are not recognized as obstacles or barriers towards higher pollution mask use among students. in other terms, as these conditions are necessary, they might be confused as sufficient factors leading to the straight adoption of the intended behaviour. on the other hand, interventions aimed at altering the opportunity costs of maintaining forms of social status and self-image, as acquired from adopting or omitting the advocated behaviour, might reveal themselves more effective and successful. this has to work both on the side of self-perception and peer-effect. this study has one limitation that needs to be acknowledged. it relates to the sample which is composed of students, not a representative cross-section of population, therefore it is not possible to stretch inferences to urban china as a whole. having said that, given that young, highly educated urban chinese seem to compose one of the groups more resistant to adopt this health prevention measure, it makes sense to prioritize motivations for mask use among this social segment. arguments for and against the use of college students as research subjects have tended to focus on whether results obtained from such subjects are generalizable to non-student populations. in our case, and for the reasons reported above, this research is less subject to this critique, as it is already studying the population of interest, and is less in need to justify the external validity of our effort. researchers such as kardes [41] and lucas [42] have argued that college students are appropriate research subjects when the research emphasis is on basic psychological processes or the theory tested links to human behaviours independent of sample characteristics. according to berkowitz and donnerstein [43] , the "meaning the subjects assign to the situation they are in and the behaviour they are carrying out plays a greater part in determining the generalizability of an experiment's outcome than does the sample's demographic representativeness." however, other researchers, such as sears [44] and gallander, north, and sugar [45] , have expressed unease about the use of a narrow database of college students in behavioural research. in particular, sears suggests that what is apparently "known" about humans is biased because college students tend to have stronger cognitive skills, less crystallized attitudes, more compliant behaviour, and less stable peer group relationships than older adults. it cannot be denied that such characteristics can endanger the external validity of survey studies. however, in our case, these are all factors that help understanding better the main mechanisms, as these underlying characteristics have at least been found to be salient when talking about healthy behaviour in this framework. while the risks of over response cannot be denied, selecting individuals possessing on average stronger cognitive skills would certainly bias our findings, but in the sense that responses are stronger not weaker in the whole population, given that non-rational drivers would presumably be amplified in this second case. this might at least in part mitigate our bias. despite the low cost, accessibility, and easiness of using pollution masks, and notwithstanding the public campaigns and media coverage stressing the associated benefits of their usage, numerous individuals struggle to adopt this kind of healthy behaviour [46] . so, if information dissemination and knowledge-based mobilization has occupied a central place in the governmental strategy to redress the negative outcomes of air pollution among individuals, net results of such attempts in terms of pollution mask use have frustrated expectations, and this happened in particular among one of the most valuable human resource assets of the nation: its college-level youth. this evidence challenges reason-based preventive medicine approaches, which are centred on pure cognitive-appraising stimuli or straightforward cost-benefit propositions which should more or less automatically lead to the adoption of the healthy behaviour. our results depict a more complex picture of cognitive behaviour, one that encourages to go beyond awareness-raising or cognitive enticement models to explain behavioural outcomes. the role of social norms suggest the usage of social cues enhancing the behaviour acceptability and desirability, thus helping to revise perceptions of the targeted action as positively aligned with aspirational life-styles. by placing pollution mask wearing in a less defensive narrative (e.g. avoiding risk) and connecting its usage to positive traits associated with social inclusiveness or emulation of valued social references' behaviors, young-well educated chinese may begin to change, first, perceptions and, then, actions. the findings of this paper could help both health operators and facemask producers to improve the design of environmental health intervention campaigns, although further evidence is needed to generalize the results to a broader population. health impact of outdoor air pollution in china: current knowledge and future research needs associations of short-term exposure to traffic-related air pollution with cardiovascular and respiratory hospital admissions in london environmental performance index exposure-response functions for health effects of ambient air pollution applicable for china-a meta-analysis effects of particulate air pollution on blood pressure in a highly exposed population in beijing, china: a repeated-measure study smog in our brains: gender differences in the impact of exposure to air pollution on cognitive performance air pollution exposure and gestational diabetes mellitus among pregnant women in massachusetts: a cohort study season, sex, age, and education as modifiers of the effects of outdoor air pollution on daily mortality in shanghai, china: the public health and air pollution in asia (papa) study. environ health perspect public awareness and willingness to pay for tackling smog pollution in china: a case study time to harmonize national ambient air quality standards beijingers don masks to defend themselves against dirty air -and to make a fashion statement interventions to reduce individual exposure of elderly individuals and children to haze: a review effectiveness of n95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis a meta-analysis of fear appeals: implications for effective public health campaigns protection motivation and self-efficacy: a revised theory of fear appeals and attitude change air pollution and defensive expenditures: evidence from particulate-filtering facemasks the theory of planned behavior predicting intention to take protective measures during haze: the roles of efficacy, threat, media trust, and affective attitude avoiding exposure to air pollution by using filtering facemask respirators: an application of the health action process approach using the theory of planned behavior to understand cervical cancer screening among latinas hpv vaccination and the effect of information framing on intentions and behaviour: an application of the theory of planned behaviour and moral norm health behavior and health education: theory, research, and practice discovering structural equation modeling using stata the role of selfefficacy in achieving health behavior change self-efficacy, controllability and intention in the theory of planned behavior: measurement redundancy or causal independence? psychol health distinguishing between perceived behavioral control and self-efficacy in the domain of academic achievement intentions and behaviors application of the theory of planned behaviour to two dietary behaviours: roles of perceived control and self-efficacy prospective prediction of health-related behaviours with the theory of planned behaviour: a metaanalysis interpretation and application of factor analytic results structural equation modelling: adjudging model fit. personal individ differ relationship between air quality and outdoor exercise behavior in china: a novel mobilebased study factors influencing the wearing of facemasks to prevent the severe acute respiratory syndrome among adult chinese in hong kong practice of habitual and volitional health behaviors to prevent severe acute respiratory syndrome among chinese adolescents in hong kong risk perception and compliance with quarantine during the sars outbreak demographic and attitudinal determinants of protective behaviours during a pandemic: a review the role of behavioral science theory in development and implementation of public health interventions seat belt and child restraint use in a developing country metropolitan city the theory of reasoned action and the theory of planned behavior the health policy implications of individual adaptive behavior responses to smog pollution in urban china understanding individual-level protective responses to air pollution warning: a case study of beijing, china self-protection investment exacerbates air pollution exposure inequality in urban china sex differences in video game play: a communicationbased explanation external validity is more than skin deep: some answers to criticisms of laboratory experiments the person-positivity bias sugar lorne a. psychologists' response to criticisms about research based on undergraduate participants: a developmental perspective social psychology of seat belt use: a comparison of theory of planned behavior and health belief model the authors would like to thank their two research assistants, ms. sherry when and ms. liang yuqi, for their excellent support in data collection, database building, and data cleaning. thanks also to ms. marilyn fisher for her help in editing the manuscript. we also would like to thank the participants to the conference environmental pollution and public health (epph, suzhou 2016) for their helpful insights, and professor alberto batinti, for his useful and thoughtful comments. this study was supported by the individual research funding from shanghai university of finance and economics. all data generated or analysed during this study are included in this published article [and its additional file 1].authors' contributions fh was responsible for the research design, data collection, statistical analysis and part of manuscript writing. fe was in charge of manuscript writing, especially concerning the theoretical implications. both authors read and approved the final manuscript.ethics approval and consent to participate participants were given both oral and written information regarding the aim of the study, purpose of the interview, research methods as well as methods for ensuring confidentiality. participation was voluntary and data anonymous. the research design and questionnaire was in compliance with the ethical standards of the shanghai university of finance and economics. formal approval of the study with a reference number is not applicable / required. not applicable. questionnaires were anonymous and all data are presented in an aggregated form. the authors declare that they have no competing interests. key: cord-324444-t697xw4y authors: rodriguez-palacios, alexander; cominelli, fabio; basson, abigail; pizarro, theresa; ilic, sanja title: textile masks and surface covers a 'universal droplet reduction model' against respiratory pandemics date: 2020-04-10 journal: nan doi: 10.1101/2020.04.07.20045617 sha: doc_id: 324444 cord_uid: t697xw4y the main form of covid-19 transmission is via oral-respiratory droplet contamination (droplet; very small drop of liquid) produced when individuals talk, sneeze or cough. in hospitals, health-care workers wear facemasks as a minimum medical droplet precaution to protect themselves. due to the shortage of masks during the pandemic, priority is given to hospitals for their distribution. as a result, the availability/use of medical masks is discouraged for the public. however, given that asymptomatic individuals, not wearing masks within the public, can be highly contagious for covid-19, prevention of environmental droplet contamination (endc) from coughing/sneezing/speech is fundamental to reducing transmission. as an immediate solution to promote public droplet safety, we assessed household textiles to quantify their potential as effective environmental droplet barriers (edbs). the synchronized implementation of a universal community droplet reduction solution is discussed as a model against covid-19. using a bacterial-suspension spray simulation model of droplet ejection (mimicking a sneeze), we quantified the extent by which widely available clothing fabrics reduce the dispersion of droplets onto surfaces within 1.8m, the minimum distance recommended for covid-19 social distancing. all textiles reduced the number of droplets reaching surfaces, restricting their dispersion to <30cm, when used as single layers. when used as double-layers, textiles were as effective as medical mask/surgical-cloth materials, reducing droplet dispersion to <10cm, and the area of circumferential contamination to ~0.3%. the synchronized implementation of edbs as a community droplet reduction solution (i.e., face covers/scarfs/masks & surface covers) could reduce endc and the risk of transmitting or acquiring infectious respiratory pathogens, including covid-19. lactis, streptococcus diacetylactis, and saccharomyces florentinus, 75ml; 3x10 6-7 cfu/ml) in 1000ml 79 pbs (fisher bp-399-1) to simulate a cloud of droplets produced by a sneeze. probiotics are bsl-80 1/'generally recognized as safe' by the fda and all experiments were conducted in bsl-2 81 hepa-filtered microbiology laboratories. no animal/human subjects were used for 82 experimentation. before testing, spray bottle nozzles were adjusted to produce cloud and jet-83 propelled droplets that match the visual architecture of droplet formation described by bourouiba el 84 at. 23 . quantification of droplets landing over a surface was performed at the time of spray using 85 seven 10mm-petri dishes containing tryptic soy agar (56.75cm 2 surface area/dish) with 5% 86 defibrinated sheep blood, placed on a need droplets to facilitate their expulsion, transmission and endc 12 , we first validated a rapid 116 spray-simulation model of droplets (mimicking a sneeze) using a bacterial-suspension to quantify 117 the extent by which widely-available household textiles reduced the ejection/long-distance flight of 118 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https://doi.org/10.1101/2020.04.07.20045617 doi: medrxiv preprint droplets. to facilitate the enumeration of macro-droplets and invisible micro-droplets, spray-119 simulations were conducted over nutritious-media agar surfaces, incubated for 24h to enable 120 colony-forming-droplet-unit (cfdu) formation. 121 based on simulations conducted in two institutions, a cloud of bacteria-carrying droplets 122 travel distances reaching >180cm, particularly for large droplets (figure 1a) , consistent with 123 reported dynamics during sneezing 23 . of relevance to sneezing behavior, simulations illustrate that 124 upward inclination of the central-spray angle allows macro-droplets to reach longer distances 125 (simulation 4/dispersion equations; figure 1b -e). although macro-droplets frequently reached 126 180cm, most micro-droplets landed on surfaces within 120cm, with spray air-turbulence carrying 127 micro-droplets into areas not reached due to gravity alone. thus, social distancing of 1.8m, without 128 edb-mask protection, as currently recommended, is insufficient to prevent droplet exposure, 129 particularly where essential-service workers congregate during pandemics (transportation, 130 supermarkets/food displays). therein, wearing edb-masks together with inclining downward the 131 head/body during sneezing could minimize the spatial range of endc. household textiles retain liquid droplets, particularly if double layered 134 to quantify the droplet retention potential of textiles as edbs, we next used the same 135 bacterial-spray-simulation model to quantify non-visualizable micro-droplets that could 136 cross/escape the textile-edb and cause microbial-surface agar contamination (textile/thread details 137 in remarkably, spray experiments with 'two-layers' (of 100%-combed cotton, common in t-144 shirts; and 100% polyester, in sports jerseys) completely prevented the ejection of large macro-145 droplets (100% endc prevention), and drastically reduced the ejection of micro-droplets by a 146 factor of 5.16log2, which is equivalent to a 97.2% droplet reduction (p<0.020 vs. single-layers, 147 figure 2c and supplementary figures 4-5) . importantly, the least-effective textile as single-layer 148 (most-'breathable', 100%-cotton homespun-115 material) achieved a 90-99.998% droplet retention 149 improvement when used as two-layers (95%ci=3.74-15.39log2). lastly, all textiles were equally 150 effective at absorbing the humidity from 3-sprays compared to medical mask/surgical cloth 151 materials, which condensate after 1-spray ( figure 2d ). together, experiments indicate that two-152 layers of household textiles are as effective as medical masks preventing endc, and that more 153 breathable materials in ≥2-layers could be effectively used if individuals deem two-layer, 'denser' 154 textiles too air-restrictive. 155 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint increase daily, and the fabrication of edb by centralized organizations could take weeks to reach 167 entire 'lockdown' communities, we suggest, based on the cotton/polyester endc effectiveness, and 168 a homemade edb-mask fabrication trial (supplementary figure 6) , that, from one piece of 169 clothing, every individual could make (without sewing machine) two 2-layer-edb masks as an 170 immediate, synchronized contribution to reduce covid-19 endc. from a surface perspective, if everyone were encouraged to wear edbs, the collective area 172 contaminated with droplets would be miniaturized to 0.3-2.77% (two-layers/single-layers), 173 compared to the potential contamination within 180cm (10.2 m 2 ). even suboptimal edbs, effective 174 for 90cm radius, could mathematically reduce the endc area by 75.1% (figure 2e ). our findings 175 and surface estimations are conservative as they are based on simulations using a (non-viscous) 176 liquid solution, assuming stationary individuals. however, the impact of edb is predictably greater 177 since real/large viscous secretions (figure 3a) , which also travel long distances (>180cm) 23 would 178 be easier to contain by edb, as communities mobilize. to further lower the risk of fomite 179 (plastic/metal surface) transmission from/by non-edb-wearers, edb-textiles used as covers, when 180 relevant, could reduce endc by 90-98% (t-test p=0.003, figure 3b ). 181 finally, to illustrate, in volumetric terms, that edbs are even more effective preventing 182 endc, we conducted a scoping review of literature to conduct analyses of droplet fluid-carrying 183 capacity. although published droplet sizes vary with study method (supplementary will also prevent small-size droplet aerosolization by trapping such droplets immediately after 192 production. an overview of a 'universal textile droplet reduction action-model' against pandemics 193 is illustrated in figure 3c . . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https://doi.org/10.1101/2020.04.07.20045617 doi: medrxiv preprint despite widespread dissemination of information to curtail the rapid spread of covid-19 197 outside of china (which affects 20-54-year-old adults, 40% of hospitalizations in the usa 27 ), little 198 attention has been devoted to endc and prevention strategies for droplet movement from infected 199 to non-infected individuals within the same community. more concerningly, is that following 200 mandatory 'stay-in-home' quarantine orders, people may return to work unprotected, unaware if 201 they are infected/shedders. this is particularly critical for 'essential pandemic workers', who face 202 different levels of risk (health-care vs. electric/transport/food services), and who can contaminate 203 environmental surfaces as they transit through the community between work (i.e., hospitals) and 204 home, or within their households 28 , without wearing masks. because mass testing is not always 205 possible 6 , especially for novel organisms like covid-19, there are growing concerns that 206 asymptomatic and mildly symptomatic citizens will continue to spread and reintroduce the virus to 207 new areas, creating waves of cases, contributing to further economic burden from the outbreak 29 . 208 nonpharmaceutical interventions (npis), also known as community mitigation strategies, 209 are actions that individuals and communities can take in order to slow the spread of illnesses. for 210 pandemics, when medical approaches (hospitalization/treatments) are limited, npis are a critical 211 component to achieve resolution. although ppe, including masks, are scientifically-effective to 212 prevent infectious disease transmission, the use of masks for the general public has not been 213 encouraged by governments 5,7 , possibly because demand will deepen the current crisis of mask 214 unavailability for medical staff, or alternatively, because the use of masks to prevent respiratory 215 infections has been misleadingly deemed ineffective, despite earlier clinical studies indicating that 216 masks could be beneficial in households during pandemics 28,30,31 . 217 although masks have been extensively studied to determine whether individuals are 218 clinically protected from infections 32,33 , and to confirm that wearing a mask promotes desirable 219 hygiene practices (handwashing, 'avoiding crowds') 5,31,34 , masks have not been examined for their 220 potential to prevent environmental contamination. masks work, if worn properly; however, 221 individuals (~50%) often fail to wear masks regularly, and properly 30,35 . despite low compliance, 222 meta-analyses indicate that masks lower the odds of having (sars)-respiratory infections by 87% 223 (or=0.13), compared to the odds of having an infection 'not wearing a mask' 36 . 224 herein, we propose, that in addition to seeking the classical/clinical 'prevention of 225 infection', npis could be universally based on 'droplet reduction models' such as edb to mitigate 226 endc. not only for the prevention of respiratory diseases, but also to prevent widespread 227 environmental dispersion of the virus, which could reach water sources or affect domestic animals, 228 as has been shown for other viruses, including pandemic influenza 37 . 229 the world is in short supply of masks since the international 'lockdown' affected 230 production 38 , with health-care workers experiencing high morbidity/mortality due to reduced 231 protection 39 . governments are seeking private support to increase mask supplies; however, such 232 strategy could take weeks/months, and infection rates would not improve if supplies were still not 233 available to 'lockdown' communities. increased community transmission leads to higher demand 234 for medical services, unless transmission is halted. using household textiles is a potentially life-235 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint cfdus on agar plates illustrating ability of cloud micro-droplets to move around spaces driven by 267 cloud turbulence (left images, agar plates were partially covered with lid at moment of spray), 268 concurrent contamination with macro-and micro-droplets. e) number of cfdu/plate (56.75 cm 2 ) 269 for 6 simulations over distance. 270 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. edbs in reducing circumferential endc. 282 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https://doi.org/10.1101/2020.04.07.20045617 doi: medrxiv preprint health experts are telling healthy people not to wear face masks for 12 human coronaviruses: insights into environmental 337 resistance and its influence on the development of new antiseptic strategies history and recent advances in coronavirus discovery the first case of 2019 novel coronavirus pneumonia imported into korea 343 from wuhan, china: implication for infection prevention and control measures acton: new symptoms of covid-19 include gi issues, 346 fatigue, no fever aerosol and surface stability of sars-cov-2 as compared with 350 sars-cov-1 detection of sars-cov and rna on aerosol samples from sars-352 patients admitted to hospital controversy around airborne versus 354 droplet transmission of respiratory viruses: implication for infection prevention aerodynamic characteristics and rna concentration of sars-cov-2 357 aerosol in wuhan hospitals during covid-19 outbreak recognition of aerosol transmission of 360 infectious agents: a commentary the infection evidence of sars-cov-2 in ocular surface. a single-center 363 cross-sectional study indirect virus transmission in cluster of covid-19 cases natural ventilation for infection control in health-care settings. annex c 371 respiratory droplets. geneva: world health organization characterizations of particle size distribution of 374 the droplets exhaled by sneeze exhaled droplets due to talking and coughing severe outcomes among patients with coronavirus disease united states a familial cluster of pneumonia associated with the 2019 novel 382 coronavirus indicating person-to-person transmission: a study of a family cluster the state of california on thursday issued a mandatory, stay-at-home order face mask use and control of respiratory virus transmission in 389 households understanding the factors involved in determining the bioburdens of surgical 391 masks cluster randomised controlled trial to examine medical mask use as 393 source control for people with respiratory illness a cluster randomised trial of cloth masks compared with medical 396 masks in healthcare workers wearing face masks in public during the influenza 399 season may reflect other positive hygiene practices in japan facemasks for the prevention of infection in healthcare 402 and community settings respirators against respiratory infections in healthcare workers: a systematic review 405 and meta-analysis pandemic and seasonal human influenza virus infections in domestic cats: 407 prevalence, association with respiratory disease, and seasonality patterns the world needs masks. china makes them but has been 410 hoarding them italy's lombardy asks retired health workers to join coronavirus 414 fight key: cord-308638-lrgvwjti authors: chalikonda, sricharan; waltenbaugh, hope; angelilli, sara; dumont, tiffany; kvasager, curt; sauber, timothy; servello, nino; singh, anil; diaz-garcia, rafael title: implementation of an elastomeric mask program as a strategy to eliminate disposable n95 mask use and resterilization: results from a large academic medical center date: 2020-06-11 journal: j am coll surg doi: 10.1016/j.jamcollsurg.2020.05.022 sha: doc_id: 308638 cord_uid: lrgvwjti background: the covd-19 global pandemic has placed a large demand on personal protective equipment for healthcare workers. n-95 respirators, required to perform aerosolizing procedures, are in short supply and have increased significantly in cost. the lack of a clear end to the pandemic requires that hospitals need to create a long-term, cost effective solution to the n95 shortage. we initially used previously described methods to reuse and resterilize n95 masks however we found they did not solve the issues related to just in time fit-testing and cost. methods: we initiated a program with the aim to reduce our dependence on n95 masks by initiating a phased program to acquire industrial style elastomeric p100 masks as a substitute for reuse and resterilization of disposable n95s. we created an allocation strategy based on availability of the masks, as well as an operational plan to fit test, educate, and disinfect the masks. results: within 1 month we were able to reduce the number of n95s needed by our network by 95%. we also found due that the cost was conservatively 10 times less per month than purchasing disposable n95s and the cost benefit increases the longer that they are needed. conclusion: establishing an elastomeric mask program is feasible and less expensive than programs focused on reusing and disinfecting disposable n95 masks. a well thought out elastomeric distribution and disinfection program does not pose greater operational challenges than an n95 reuse and resterilization program. in addition, elastomeric masks can be stored for future surges and should be considered an essential part of all healthcare facilities’ supply of personal protective equipment. implementation of the program has eliminated our dependence on disposable n95s to maintain normal operations during the global pandemic. the covd-19 global pandemic has placed a large demand on personal protective equipment for healthcare workers. n-95 respirators, required to perform aerosolizing procedures, are in short supply and have increased significantly in cost. the lack of a clear end to the pandemic requires that hospitals need to create a long-term, cost effective solution to the n95 shortage. we initially used previously described methods to reuse and resterilize n95 masks however we found they did not solve the issues related to just in time fit-testing and cost. we initiated a program with the aim to reduce our dependence on n95 masks by initiating a phased program to acquire industrial style elastomeric p100 masks as a substitute for reuse and resterilization of disposable n95s. we created an allocation strategy based on availability of the masks, as well as an operational plan to fit test, educate, and disinfect the masks. results: within 1 month we were able to reduce the number of n95s needed by our network by 95%. we also found due that the cost was conservatively 10 times less per month than purchasing disposable n95s and the cost benefit increases the longer that they are needed. the worldwide covid-19 crisis has brought to light the importance of having a reliable supply of respirators for our healthcare providers. the n95 shortage has led the centers for disease control (cdc) to create guidelines for extending the use of n95 beyond what is conventionally recommended by the manufacturer. in addition, the cdc has also recommended that fit testing of n95s be suspended to help reduce the number of n95s normally used during this process. [1] the cost of n95 masks has skyrocketed related to the increase in worldwide demand combined with the limited availability due to supply chain constraints. the unknown duration of the current pandemic requires healthcare organizations to create a long term solution to disposable n95s that can be achieved in a cost effective manner and scalable across large organizations. many innovative methods for reusing and sterilizing masks have been introduced with early success in reducing the amount of n95s that are required for an organization to source. [2] [3] . we, like other healthcare networks operationalized a mask reuse and sterilization protocol. however, implementing a sterilization and reuse program created an equally intensive operational plan and does not allow for use beyond a set number of resterilizations. [4] the introduction of numerous types and brands of n95 and n95 equivalents also poses challenges related to fit testing and supply availability. for clinical efficacy, there must be consistency of the types of masks available in order to ensure that individuals have access to the masks for which they were fit tested. we implemented a widespread program to replace the majority of our n95 usage with reusable p100 elastomeric half mask respirators ( figure 1 ) and paprs to help alleviate the issues with n95 reusage and resterilization. the allegheny health network is 9 hospital system comprising approximately 2200 licensed beds with sites in pennsylvania and western ny, employing 21000 individuals. the distribution of a limited protective resource within a 9-hospital network can be a controversial and stressful process. every new patient contact brings some risk to the individual provider, and thus all providers can argue that they should be given priority to the limited resource. we felt that a utilitarian approach towards distribution was best suited to weigh risks and benefits to both our staff and patients. a panel of clinical personnel was assembled, with participation from institutional leadership amongst nursing, anesthesia, critical care medicine, surgery and supply chain. we prioritized clinical units and personnel based on their inherent risk to covid-19 exposure. greatest priority was given to those clinical staff with direct airway manipulation and those dealing with high acuity covid-19 patients. (table 1) initially, emergency rooms, intensive care units and anesthesia providers were targeted for conversion of disposable n95 usage to reusable p100 half-mask respirators. [1] staffing per shift was broken down across the 9 hospitals, and a sufficient number of respirators were assigned to each unit for a 24hr period to provide protection for physicians, physician-extenders, nursing, and respiratory therapy in the first wave of distribution. those devices were assigned to the specific clinical units rather than providers, with the assumption that they would be turned in for cleaning and processing after shift completion. system-wide fit testing was scheduled by nursing leadership. as additional shipments were made available, that initial disbursement was supplemented to expand device availability to phase 2 and 3 caregivers. proceduralist physicians were included based on practice exposure to the airway or lung tissue. [5] [6] [7] finally, as more devices were delivered from the manufacturer, we transitioned from a high turnover unit-assigned, shared-device model to assigning devices to specific providers to use and maintain. this transition was necessary to maintain efficiency as we utilized individuals from our central sterile processing to disinfect the masks. we wanted to ensure that this was sustainable when those individuals would be redeployed for elective operative case volume once it returned. to prepare for the launch and distribution of the masks, we engaged the director of education and the chief certified registered nurse anesthetist (crna) for each network hospital. each site identified 1-2 site coordinators and multiple super users to perform the real time education, fit testing, and return demonstration with distribution of each mask. super users were trained via an electronic module from the manufacturer and an in person demonstration session. a multimodal approach to staff education was selected. this included electronic/ printed directions, in person demonstration, and video support. super users completed one on one mask demonstrations with each staff member to ensure user safety and create a record of training activities. we filmed a real time video demonstration of mask donning, seal checks, and doffing accessible through qr codes to provide staff with access to directions at all times. during the time period when the supply of masks did not allow for individuals to have their own masks, we initiated a system of collection and disinfection. (figure 2) the sterile processing departments were trained in a similar fashion for the disassembly, disinfection and reassembly of the masks. a super user completed an onsite overview at each facility. the site managers signed each staff member off on their knowledge of the disinfectant solution, cleaning process, and return demonstration of mask disassembly and reassembly. in the first wave of distribution, 1,962 staff members were fit tested with 1,840 staff members passing. staff members were required to remove make-up and report for fit testing clean shaven as applicable. fit testing was performed via hood and sensitivity solution testing or using quantitative methods only after the staff member successfully donned the mask and passed positive and negative seal checks. if the staff member did not initially pass the seal checks, the mask would be adjusted or a different size would be selected. if the staff member could not successfully pass the seal checks, we did not proceed to fit testing. staff members that failed p100 fit testing were offered an n95 mask if applicable or a powered air purifying respirator (papr) to use in clinical situations. we measured n95 usage in the medical intensive care unit (micu). the micu is an 18 bed negative pressure icu where the majority of covid-19 patients were cared for. we recorded the number of individuals caring for the patients in a 24hour period. we also measured the number of room entries per individual/day. this would correlate with the number of n95 masks that would be used without extended reuse interventions. room entries (individuals multiplied by number of room entries) ranged from 41-133 entries in one patient room in a 24 hour period; with a mean room entry of 87 times per patient in a 24 hour period. (table 2 ). at the beginning of the study we had not employed a policy to re-use n-95s, therefore 87 n-95 masks were being used per patient per 24-hour time period. approximately 1,566 n-95 would be used per day in the micu. we re-structured who could enter the room, as well to further decrease the usage of ppe. this eliminated consultants, dietary, environmental health services, and nursing assistants from entering the room. following institution of the elastomeric n-100 masks our usage of n-95s masks has decreased to 0. those staff members that failed fit testing for the elastomeric n-100 masks were allocated paprs effectively reducing our disposable n95 usage to zero. after greater than one month of utilization no healthcare workers chose to return to n95 usage. we utilized a cost ratio methodology to evaluate the economics of the program. we found that 116 p100 respirator and cartridges replaced 2088 disposable n95s/day. after more than one month of usage we have found that filters have not needed to be changed more frequently than once a month. given that the cartridges are able to be used until they are visibly soiled and/or there is difficulty with airflow we set a time period of one month of use for routine replacement. part of the education included proper replacement of the filter cartridges to prevent inadvertent soilage and contamination. we included the replacement of the filter monthly in the cost analysis. in order to calculate the current savings we utilized a price paid of approximately $3.00/ n95 which is well below the current market rate compared to approximately $20 for an elastomeric mask and $10 per cartridge. we also reduced the usage of disposable n95 masks by 75% to take in to account the aggressive reuse and sterilization programs that would have been employed had we not purchased the elastomeric. the cost of an elastomeric mask programs is conservatively 10 times cheaper per month and the cost benefit continues to increase the longer they are in use. (figure 3 ) the global impact of covid 19 has revealed several weaknesses in our ability to secure critical ppe such as respirators. the utilization of disposable n95s during a global pandemic has several key limitations including supply, cost and the inability to adequately fit test healthcare workers without utilizing masks in the process. resuming elective procedures requires that facilities demonstrate and adequate amount of resources including ppe. in order for hospitals to protect staff and patients in our procedural areas, the ability to provide respiratory protection is paramount. the implementation of elastomeric masks has allowed us to create an environment where universal respiratory precautions for all intubations and other aerosolizing procedures can be adopted without any noticeable impact on our supply of disposable n95 respirators. in addition, the advantage of implementing an elastomeric respirator program is that it does not require any additional hospital resources as compared to an n95 reuse and resterilization programs. the ability to disinfect and store these devices in healthcare has proven to be feasible. [8] the elastomeric masks have also been found to be well tolerated for use by healthcare workers during long periods of patient care. [9] in addition, the utilization of standardized type of mask eliminates the need for multiple fit testings related to the different brands and styles of masks that are acquired during a pandemic. [10] conclusion elastomeric masks with disposable p100 filters were found to be superior to disposable n95s for protection of healthcare workers at a large academic medical center. they do not have the waste associated with fit testing disposable n95s so there is no barrier to fit testing all front line caregivers. a return and disinfection program does not pose a greater operational challenge than previously described disposable n95 resterilization programs. the nature of the elastomerics and their ability to be disinfected allows for multiple caregivers to share the same mask. the one time cost and storage aspects related to the program lend to a significant cost benefit when compared to disposable n95s. the financial impact that many hospitals are facing related to the pandemic requires long-term cost effective solutions and the implementation of an elastomeric respirator program will obviate many of the current issues that are being faced with disposable mask usage and allow for health systems to eliminate their dependence on a continual supply of disposable n95s. in order to resume operations, hospitals would benefit by using the time between surges to create and operationalize a reusable elastomeric mask program. strategies for optimizing the supply of n95 respirators how to decontaminate n95 masks for reuse | rt. rt decis makers respir care hydrogen peroxide vapor sterilization of n95 respirators for reuse institution of a novel process for n95 respirator disinfection with vaporized hydrogen peroxide in the setting of the covid-19 pandemic at a large academic medical center infection control in dental health care during and after the sars-cov-2 outbreak management of the airway and lung isolation for thoracic surgery during covid-19 pandemic high-risk aerosol-generating procedures in covid-19:respiratory protective equipment considerations. otolaryngol head, neck disinfection of reusable elastomeric respirators by health care workers: a feasibility study and development of standard operating procedures reusable elastomeric air-purifying respirators: physiologic impact on health care workers selection and use of respiratory protection by healthcare workers to protect from infectious diseases in hospital settings key: cord-291392-19vj647z authors: poostchi, ali; kuet, mong-loon; richardson, patrick s.; patel, moneesh k. title: comment on: “controversies regarding mask usage in ophthalmic units in the united kingdom during the covid-19 pandemic” date: 2020-06-03 journal: eye (lond) doi: 10.1038/s41433-020-1005-y sha: doc_id: 291392 cord_uid: 19vj647z nan we read with interest the article by naveed et al. [1] on controversies regarding mask usage in ophthalmic units during the covid-19 pandemic. we agree that offering patients a surgical face mask will lower the risk of them transmitting infection. we found that placing a mask in front of a breathing simulator led to a tenfold reduction in particle transmission [2] . we would, however, question their assertions that uk guidance for personal protective equipment (ppe) falls short and that ffp3 respirators should be mandated for dealing with symptomatic individuals. the who, cdc and ecdc recommend that respirators should be prioritised for use in high risk aerosol generating procedures and that surgical face masks are acceptable in other situations when treating individuals with suspected or confirmed covid-19 [3] . in addition, there is robust evidence from a large randomised control trial showing that in outpatients, there is no benefit from using n95 (ffp2) respirators compared with surgical face masks to reduce influenza and other respiratory viral illnesses in health care workers [4] . subsequent meta-analyses have shown similar results with the benefits of respirators likely offset by discomfort with prolonged use leading to more frequent manipulation or reduced compliance [5] . there is an added danger that using these respirators will lead to a false sense of security when in reality, ppe is only one part of an integrated approach to infection control. attention should also be given to measures such as streamlined patient flow and scrupulous disinfection which are further up in the 'hierarchy of control'. conflict of interest the authors declare that they have no conflict of interest. publisher's note springer nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. controversies regarding mask usage in ophthalmic units in the united kingdom during the covid-19 pandemic efficacy of slit lamp breath shields airborne or droplet precautions for health workers treating covid-19? j infectious dis n95 respirators vs medical masks for preventing influenza among health care personnel: a randomized clinical trial effectiveness of n95 respirators versus surgical masks against influenza: a systematic review and meta-analysis key: cord-341695-9l2lmzyr authors: he, w.; guo, y.; liu, j.; yue, y.; wang, j. title: filtration performance degradation of in-use masks by vapors from alcohol-based hand sanitizers and the mitigation solutions date: 2020-11-04 journal: nan doi: 10.1101/2020.11.01.20223982 sha: doc_id: 341695 cord_uid: 9l2lmzyr how often does one perform hand disinfection while wearing a mask? in the current covid-19 pandemic, wearing masks and hand disinfection are widely adopted hygiene practices. however, our study indicated that exposure to the vapors from alcohol-based sanitizers during hand disinfection might degrade the filtration performance of the in-use masks, and the degradation worsened with the increasing number of hand disinfection. after five times of hand disinfection, the filtration efficiencies of surgical masks decreased by >8% for 400 and 500nm particles and by 3.68{+/-}1.83% for 1m particles. this was attributed to the dissipation of electrostatic charges on the masks when exposed to the alcohol vapor generated during hand disinfection. simple practice of vapor-avoiding hand disinfection could mitigate the effects of alcohol vapor, which was demonstrated on two brands of surgical masks. the vapor-avoiding hand disinfection is recommended to be included in the hygiene guide to maintain the mask performance. the covid-19 pandemic is raging and many countries are suffering the second wave. compared with the early stage of the pandemic outbreak, more comprehensive approaches, including contact tracing, quarantine, physical distancing, hand hygiene, and masks, have been proposed to slow down the spread of covid-19. 1 nevertheless, the number of new infections per day has constantly increased since october 2020. 2 in order to contain the second wave of the pandemic and keep businesses open, regular hand disinfection and mandatory face masks in public places have been ordered or recommended in the latest anti-covid measures by most countries. [3] [4] [5] a number of studies showed that wearing masks in public could prevent interhuman transmission effectively. 6, 7 in order to solve the mask shortage, various works related to mask regeneration and alternative materials for masks were carried out. 8, 9 simultaneously, it is confirmed that alcohol-based sanitizers can inactivate the sars-cov-2 virus, and they are recommended by the world health organization (who). 10, 11 regular hand disinfection and wearing masks in public places will be a necessary part of our life in the foreseeable future. however, using the alcohol-based sanitizers for hand disinfection may degrade the filtration performance of masks. organic solvents including alcohol-based agents degraded the filtration efficiencies of electrostatic filters by dissipating the electrostatic charges. 12, 13 ethanol was not recommended for mask regeneration, although it was capable of efficient microbial inactivation. 8 many hand sanitizers on the market are alcohol-based. although the alcohol-based sanitizers would not directly contact the masks worn by the users during the hand disinfection, the vapors of alcohol-based sanitizers could dissipate the charges on the masks, finally leading to insufficient protection for the mask wearers. in the present work, the effects of hand disinfection using alcohol-based sanitizers on . cc-by-nc-nd 4.0 international license it is made available under a perpetuity. is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint filtration performances of cotton masks, surgical masks, and n95 respirators worn by the users were investigated. the selected masks were shown in figure s1 . both the electrostatic potentials and filtration efficiencies for 50 nm to 3 μm particles of the masks were measured to evaluate the filtration performance of masks by the setups showed in figure s2 and figure s3 . the particle sizes were selected according to the report that sars-cov-2 aerosols were found in the size range of 250-1000 nm, 14 and the test standard (en 14683) for surgical masks is at 3 μm particles. the size distributions of monodisperse particles used for the filtration test could be found in figure s4 . the dependence of the degradation effect on the number of performed hand disinfection was investigated. in addition, we proposed a simple practice for vaporavoiding hand disinfection to mitigate the effects of alcohol-based sanitizers on mask filtration performance. who published a guide for the detailed hand disinfection steps, but the position of hands during hand rubbing was not mentioned. 15 herein, the who recommended hand disinfection steps were employed. the duration of the entire procedure was 20-30 seconds. meanwhile two types of practices featuring different hand and face positions were studied. in one type of practice illustrated on the left of figure 1 , the volunteers placed hands between the abdomen and chest, which was named as the common hand disinfection in the present study. in the other type of practice, to avoid inhaling the sanitizer vapor, the volunteers placed hands on one side of the body and turned the head to the opposite side, as shown on the right in figure 1 is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint inhaled airflow was most concentrated was cut out for the performance test. in the figures, "no hd" indicates the mask was worn 5 hours without hand disinfection; "hd x n" indicates that n times of hand disinfection were performed during the 5 hours when the mask was worn. fig. 1 using alcohol-based sanitizer for common and vapor-avoiding hand disinfection. a type of cotton mask on the swiss market was selected to be evaluated (photo in figure s1 ). because the filtration efficiencies of the selected cotton mask for 50-800 nm particles were very low (about 10-20%, figure s5 ), we only used the total filtration efficiency of the cotton mask for the polydisperse nacl particles ( figure s6 ) to evaluate the effect of exposure to sanitizer vapor. the cotton mask consisted of textile fabric, and its particle capture function only depended on the physical structure instead of electrostatic property. both the filtration efficiencies and electrostatic potential of the cotton mask had no change after 5 times of common hand disinfection ( figure 2 and is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint for a type of selected surgical masks (brand 1), the average electrostatic potential decreased as the number of common hand disinfection increased (figure 3a) . a statistically significant degradation of the electrostatic potential occurred when the number of hand disinfection increased to 4 times or more (table s1 ). the electrostatic potential of all tested n95 respirators had no statistically significant difference after common hand disinfection up to 10 times, which indicated that using alcohol-based is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint filtration efficiencies of the surgical masks decreased as the number of common hand disinfection increased (figure 3b ). after 5 times of common hand disinfection, the degradation of filtration efficiency for 300 nm particles exceeded 3%, and more than 8% filtration efficiency degradation for 400 and 500 nm particles was observed. after 4 and 5 times of common hand disinfection, the filtration efficiency for 1 μm particles decreased from 98.61±0.57% to 95.96±1.49% and 94.93±1.83%, respectively (fig. 3c) . the filtration efficiency for 3 μm particles was not affected (fig. 3d) . the different alcohol vapor effects for various particle sizes were attributed to the underlying filtration mechanisms: electrostatic capture plays a significant role for small particles in the sub-micron range, whereas interception and inertial impaction dominate for particles above several micrometers. 16 sars-cov-2 aerosols were found in the size range of 250-1000 nm. 14 therefore, the filtration efficiency degradation of surgical masks after common hand disinfection for several times would diminish the protection for the mask wearers who are exposed to airborne sars-cov-2 aerosols. common hand disinfection up to 10 times had no obvious influence on the filtration efficiencies of the n95 respirator for particles in the range of 80-500 nm (figure 3f ). the filtration efficiency of the n95 respirator for 50 nm particles dropped with the increasing number of common hand disinfection. after 10 times of common hand disinfection, the filtration efficiency of the n95 respirator for 50 nm particles decreased slightly from 99.98±0.003% to 99.78±0.01%, which could still provide high level protection. the charge de-trapping of electrostatic filters induced by alcohol vapor was the main reason of the filtration efficiency degradation, which was shown in our previous study. 12 actually, alcohol vapor treatment is a standard method in iso/dis 16890-1 to discharge electret filters and has been widely used in previous studies. 17, 18 it has been noticed that the same common hand disinfection exhibited different influences on is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint surgical masks and n95 respirators, which might be attributed to the different structures of these two types of masks ( figure s8 ). the particle capture function of both the surgical mask and n95 respirator depends on the inner layer which usually consists of charged pp (polypropylene) melt-blown nonwoven. first, the outermost layer of the n95 respirator was thicker than that of the surgical mask. it is more difficult for the alcohol vapor to penetrate into the inner layer of the n95 respirator. second, the surgical mask had a single charged pp melt-blown nonwoven inner layer, whereas the n95 respirator possessed multiple nonwoven layers. although the original electrostatic potentials of two types of masks were similar, the charge amount throughout the entire n95 respirator was higher than the surgical mask. in other words, the alcohol vapor dose from hand disinfection in the present study only dissipated a small percentage of the charges on the n95 respirator, and was not enough to induce notable degradation of the electrostatic potential or filtration efficiency. the vapors from alcohol-based sanitizers during hand disinfection presented more influence on the surgical mask than the n95 respirator. since surgical masks are widely used by general public now, appropriate mitigation strategies are therefore needed. is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint brand 2 were tested to evaluate the vapor-avoiding hand disinfection method. for surgical mask-brand 1, only ~1% degradation of filtration efficiency for 400 nm particles was observed after 5 times of vapor-avoiding hand disinfection (figure 4a ). the filtration efficiency for 1 μm particles was also maintained when applying vaporavoiding hand disinfection (figure 4c ). in comparison, the degradation of filtration efficiencies for both 400 and 500 nm particles exceeded 8% after 5 times of common hand disinfection. similar results were obtained for surgical mask-brand 2 (figure 4b and figure 4d ). other methods such as putting hands behind the body can also provide adequate protection of the mask during hand disinfection using alcohol-based sanitizers. the key point is to avoid inhaling alcohol vapor. is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint disinfection; a) and c) surgical mask-brand 1; b) and d) surgical mask-brand 2. in summary, the potential risk of applying alcohol-based sanitizers while wearing masks has been ignored. using alcohol-based sanitizers for hand disinfection may degrade the filtration efficiencies of the in-use masks, and thereby weaken the protection for the mask wearers when they are exposed to virus-laden aerosols. for a widely used brand of surgical mask, the degradation of the filtration efficiency for 300 nm particles was observed after one time of common hand disinfection. when the number of common hand disinfection increased to five, the filtration efficiencies for 400 and 500 nm particles degraded by more than 8%. in contrast, the alcohol vapor had little influence on the filtration performance of a brand of n95 respirator. only 0.20±0.01% of filtration efficiency degradation for 50 nm particles was observed after ten times of common hand disinfection. compared to the surgical mask, the stronger resistance of the n95 respirator to alcohol vapor was attributed to its thicker outermost layer and multiple charged inner layers. n95 respirators are mainly used by medical staffs in the current situation and surgical masks are widely employed in healthcare settings. high dose of alcohol-based sanitizers is used for not only hand disinfection but also medical device disinfection in hospitals. by applying the precautionary principle in the case of highly dangerous viruses, the influence of alcohol vapor generated during disinfection processes on n95 respirators and surgical masks should be considered, especially in healthcare settings. cotton masks are not electrostatic filters and their filtration performance is not influenced by alcohol vapor. however, cotton masks may have low efficiencies and are not commonly used by medical personnel. the common hand disinfection used in the present study followed the standard hand is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint disinfection steps recommended by who, and the position of the hands was intentionally kept consistent. the individual differences in the hand disinfection steps and body position may cause different effects on the mask performance than those shown here. there are no shortcuts and only a comprehensive approach can slow down the spread of the current pandemic. wearing masks is a critical part of the comprehensive prevention measures, therefore more attention should be paid to the reliability of masks. using alcohol-based sanitizers for hand disinfection may degrade the filtration performance of masks by dissipating the charges. vapor-avoiding hand disinfection is a simple and efficient practice to mitigate such risks. we recommend adding the vaporavoiding hand disinfection in the guide of hand hygiene. the details of particle filtration and electrostatic potential tests, and additional figures. is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 4, 2020. ; https://doi.org/10.1101/2020.11.01.20223982 doi: medrxiv preprint who. covid-19 strategy update director-general's opening remarks at the media briefing on covid-19 -12 cdc. considerations for wearing masks new coronavirus: masks to mask or not to mask: modeling the potential for face mask use by the general public to curtail the covid-19 pandemic identifying airborne transmission as the dominant route for the spread of covid-19 evaluation of regeneration processes for filtering facepiece respirators in terms of the bacteria inactivation efficiency and influences on filtration performance household materials selection for homemade cloth face coverings and their filtration efficiency enhancement with triboelectric charging survival of sars-cov-2 and influenza virus on the human skin: importance of hand hygiene in covid-19 guide to local production: who-recommended handrub formulation s investigation of surface potential discharge mechanism and kinetics in dielectrics exposed to different organic solvents electret mechanisms and kinetics of electrospun nanofiber membranes and lifetime in filtration applications in comparison with corona-charged membranes aerodynamic analysis of sars-cov-2 in two wuhan hospitals air filtration manuscripts. ‡ w.h. and ‡ y.g. contributed equally. the authors declare no competing financial interest. the work was partially supported by innosuisse project 46668.1 ip-eng "remask: key: cord-297295-lsewt5t2 authors: matusiak, łukasz; szepietowska, marta; krajewski, piotr; białynicki‐birula, rafał; szepietowski, jacek c title: inconveniences due to the use of face masks during the covid‐19 pandemic: a survey study of 876 young people date: 2020-05-14 journal: dermatol ther doi: 10.1111/dth.13567 sha: doc_id: 297295 cord_uid: lsewt5t2 nan the use of face masks by general population became ubiquitous during the covid-19 pandemic (1) . personal protective equipment (ppe) can cause harm to the skin (2) (3) (4) (5) , however, little is known on inconveniences of face masks wearing (4) (5) (6) (7) . this study was undertaken to analyze the most bothersome issues reported by young people using face protection during current viral pandemic. the survey was created with google® forms and posted on facebook® groups for students in poland. the recall period was the last 7 days. the data were collected in 48 hours (12 th -14 th , april 2020). at that time wearing face masks in poland was not mandatory. 2315 answers were received, 8 questionnaires were removed (incompleteness of data). out of 2307 responders 1393 (60.4%) declared face masks wearing. as 517 (37.1%) participants used several types of face masks they were excluded and finally, 876 questionnaires were considered. the age of the group was 18-27 years. the responses were downloaded for statistical analysis (statistica 13; statsoft, tulsa, ok, usa). out of 876 participants only 27 people (3.1%) did not complain of any problems related to face mask wearing. out of all reported inconveniences, difficulty in breathing appeared to the most common one (35.9%), followed by warming/sweating (21.3%), misting up of the glasses (21.3%) and slurred speech (12.3%). interestingly, other skin bothersome reactions related to wearing of face masks were reported less often (itch -7.7%, skin irritation -0.9%). difficulties in wearing the glasses and limited visibility were rarely reported (0.3% each). in the model of logistic regression analysis we found that wearing surgical masks among the other types of masks showed significantly lower risk for the development of most common bothersome issues, as difficulty in breathing, warming/sweating, glasses misting up, slurred this article is protected by copyright. all rights reserved. speech and itch (or=0.42, or=0.60, or=0.10, or=0.17 and or=0.04, respectively). in contrast, cloth masks use was related to higher risk of difficulty in breathing (or=1.56), warming/sweating (or=1.31), glasses misting up (or=1.92), slurred speech (or=1.86) and itch (or=2.99). respirators were found to be at increased risk only for glasses misting up (or=1.65) ( table 1) . adverse reactions to ppe were mostly reported in health care workers (hcw) (2-5). to the best of our knowledge we presented for the first time a real life data on the most bothersome aspects of face mask use within general public. we documented that wearing surgical masks was linked to significantly lower risk of adverse reactions. this is supported by roberge et al. (7) who postulated that surgical mask use at low-moderate work rate was not associated with clinically significant physiological impact. however, some participants complained on skin irritation (11%), moisture build up (11%), sticking to the skin (11%), significant face warmth (26%) and pinching (7%). during the viral pandemics due to shortage of medically graded masks, cloth masks became more popular (8) . although there is no enough strong evidence the cloth masks may be only slightly less effective than surgical masks in blocking emission of particles. they are thought to be fivefold more effective than not wearing face protection (9) . this article is protected by copyright. all rights reserved. this article is protected by copyright. all rights reserved. rational use of face masks in the covid-19 pandemic skin damage among healthcare workers managing coronavirus disease-2019 adverse skin reactions among healthcare workers during the coronavirus disease 2019 autbreak: a survey in wuhan and its surrounding regions skin reactions to n95 masks and medical masks among health care personel: a self-reported questionnaire survey in china adverse skin reactions to personal protective equipment against severe acute respiratory syndrome--a descriptive study in singapore this article is protected by copyright. all rights reserved wear n95 mask with plastic handle reduce pressure injury absence of consequential changes physiological, thermal and subjected responses from wearing a surgical mask covid-19: should the public wear face masks? testing the efficacy of homemade masks: would they protect in an influenza pandemic this article is protected by copyright. all rights reserved key: cord-343535-r8rsbfs3 authors: chowdhury, mohammad asaduzzaman; ahmed shuvho, md bengir; shahid, md abdus; haque, a.k.m. monjurul; kashem, mohammod abul; lam, su shiung; ong, hwai chyuan; uddin, md. alhaz; mofijur, m. title: prospect of biobased antiviral face mask to limit the coronavirus outbreak date: 2020-10-03 journal: environ res doi: 10.1016/j.envres.2020.110294 sha: doc_id: 343535 cord_uid: r8rsbfs3 the rapid spread of covid-19 has led to nationwide lockdowns in many countries. the covid-19 pandemic has played serious havoc on economic activities throughout the world. researchers are immensely curious about how to give the best protection to people before a vaccine becomes available. the coronavirus spreads principally through saliva droplets. thus, it would be a great opportunity if the virus spread could be controlled at an early stage. the face mask can limit virus spread from both inside and outside the mask. this is the first study that has endeavoured to explore the design and fabrication of an antiviral face mask using licorice root extract, which has antimicrobial properties due to glycyrrhetinic acid (ga) and glycyrrhizin (gl). an electrospinning process was utilized to fabricate nanofibrous membrane and virus deactivation mechanisms discussed. the nanofiber mask material was characterized by sem and airflow rate testing. sem results indicated that the nanofibers from electrospinning are about 15-30 μm in diameter with random porosity and orientation which have the potential to capture and kill the virus. theoretical estimation signifies that an 85 l/min rate of airflow through the face mask is possible which ensures good breathability over an extensive range of pressure drops and pore sizes. finally, it can be concluded that licorice root membrane may be used to produce a biobased face mask to control covid-19 spread. the emergence of coronavirus and its rapid spread across the globe has led to a large epidemic and pandemic. in response, many countries have initiated prodigious non-pharmaceutical activities like lockdowns, social distancing, and closure of educational institutions. it will be beneficial for people if an appropriate face mask can be designed that can inactivate the virus itself. during coronavirus (sars-cov-2) infections, the face mask is crucial in preventing transmission [1] . it has been reported that face masks are effective in lowering the spread of the virus. [2] [3] [4] [5] . sars-cov-2 is spread through airborne droplets and, in some cases, aerosols containing the virus. respiratory droplets transmission is a serious concern due to the rapid spread and circulation of sars-cov-2 in humans [6] . face masks can filter droplets containing the virus. many countries are not yet fully prepared for disease control at this magnitude and may not be able to prevent transmission efficiently. in this regard, a vaccine can comprehensively reduce mortality. however, potential vaccines are still in the trial stage. in this situation, masks can significantly prevent any microbes. thus, the use of personal respiratory masks may be an effective way to reduce transmission of covid-19 however, face masks that are currently available in the market may not reduce the transmission of the virus in the community because they are not used correctly. it would be better and advantageous to reduce the transmission of the virus if the face mask itself could damage the virus. in addition, most current face masks have a pore size which is larger than the virus. it is a major challenge for researchers to inactivate the virus, thus, they are trying to develop a universal virus capturing system. nevertheless, face masks become an important global healthcare measure amid the coronavirus pandemic. it is a challenging task during the pandemic to balance the supply of and demand for masks during disease outbreaks. currently available masks, which are made of non-renewables, are environmentally hazardous and non-biodegradable. the processing of single-use masks made of synthetic polymers produces environmentally damaging microplastics. therefore, the efficacy of mask disposal must be improved urgently by integrating raw materials that are intrinsically j o u r n a l p r e -p r o o f environmentally friendly, lightweight, and disposable and provide a high standard of efficiency at a low cost. in this circumstance, plants with antimicrobials properties such as oregano, sage, basil, fennel, garlic, and licorice can significantly reduce the spread of coronavirus [7] . among these plants, licorice has potentially very powerful antiviral properties [8] . it is a common herb traditionally used in the asia-pacific region. researchers have demonstrated that licorice is effective against rsv, hiv, and sars-cov, all of which causes serious pneumonia [9] [10] [11] . researchers have found that different elements of licorice are responsible for antimicrobial and antiviral activities through various mechanisms. licorice contains around 300 flavonoids and more than 20 triterpenoids. among them, two triterpenes, 18-β glycyrrhetinic acid (ga) and glycyrrhizin (gl) have been shown to have antiviral properties and the potential to weaken virus activities [8] . the recent study discloses that the polymeric form of glycyrrhetinic acid leads to excellent antiviral effects [12] . therefore, this study aims to develop and assess the porosity of a fibrous threelayered filtration mask made from licorice root membrane. no study on the development of biobased face masks using licorice root membrane was found in the literature. therefore, it is expected that the outcome of this research will guide researchers, scientists and policymakers to develop biobased antiviral face masks to reduce the spread of covid-19. in this study, licorice root was used to fabricate the nanofibers due to its viral inactivation compounds including gl and ga, which possess an antimicrobial capacity. nanofibers destroy the virus by releasing gl and ga via contact inhibition or immobilization. plants have been utilized for drug development, thus, it would be expedient to investigate and characterize the possible fusion of the active elements of these plants for anti-viral applications. licorice nanofibers can be assembled for increased protection against covid-19. polyvinyl alcohol (pva) is a biocompatible nontoxic, highly hydrophilic semi-crystalline polymer with remarkable properties such as water solubility, strength, gas permeability, and thermal characteristics [13] . pva solution has been used broadly in the electrospinning process because of its ability to produce biodegradable mats and ultrafine separation filters. pva solution helps the formation of excellent quality nanofibers in electrospinning. j o u r n a l p r e -p r o o f licorice roots were washed thoroughly with mineral water, ground and then immersed into methanol from sigma-aldrich (ns: m=1:2) for 8 hours for extraction. the extracts were filtered twice through a quadruple layer of nylon mesh fabric and then evaporated at 70℃ while being magnetically stirred until a jelly of ns polymer formed. in addition, 10g polyvinyl alcohol (pva) with a molecular weight (mw) of 115,000 dp of 1700-1800, viscosity: 26-32cps, 99% hydrolyzed granules were sourced from loba chemical (india). pva was mixed with 90ml deionized water to obtain 10wt % (w/v) solution. this mixture was stirred and heated to 80°c to attain a clear, highly soluble and transparent solution. next, 14g of licorice extract was mixed with 30ml pva solution to prepare the final solution for electrospinning. an electrospinning machine (model tl-01, tong li tech) produced the nanofibrous membrane using pva and licorice root extract under optimized processing parameters. figure 1 depicts the process from licorice root extract to mask design. the prepared solution was transferred to a plastic syringe attached to a capillary tip with an inner diameter of 22 gauge (0.64 mm). the plastic syringe was placed at a 45° angle and the distance between the collector and capillary tip was maintained at 15 cm. the copper wire attached to a positive electrode at 23 kv was inserted into the solution and a negative electrode at 12 kv was connected to a metallic collector. the solution pumping rate was fixed at 4 mm/h. the measurement of airflow through the pores of the mask is important to determine the functionality of the mask. the airflow rate q (m 3 /s) has been calculated using equation 1 while the air mean velocity ܷ (m/s) has been determined using equation 2 [19] . where, ∆ܲ is the pressure drop across the face mask, ݀ is the diameter of the mask pore, η is the air dynamic viscosity (pa.s), h is the pore length (m), a is the mask area (m 2 ), and m is the number of the pores. the air dynamic viscosity was taken at 30°c. the ∆ܲ is maintained at 340 pa and the thickness of the face mask is maintained at 2µm. to simplify the estimation, the shape of the pore is considered circular due to the nanoscale range. additionally, it has been assumed that the airflow is laminar and the effects of friction is negligible. the mechanism of virus deactivation is shown in figure 2 . the topography of fabricated nanofibrous membrane shows that sneezed microdroplets can be easily captured and inhibited. cinatl et al. [9] report that the most active compound of licorice root in inhibiting the sars related virus is glycyrrhizin. glycyrrhizinic acid (glr), a triterpenoid saponin, is mainly isolated from licorice root, which is effective against a variety of human viruses [14] . the study by the researcher [15] shows clear evidence that glycyrrhizinic acid isolated from licorice has antiviral properties that can deactivate the virus and stop replication. droplet microbes are locked on the agent and infectious droplets are rapidly opened by hydrophilic action leading to exposure of viruses. the trapping and inhibiting properties of the licorice root inactivates the virus quickly. gl and ga are capable of damaging biomolecules such as portions, lipids and dna [16] . j o u r n a l p r e -p r o o f shows that a licorice root particle density of about 0.021 particles/mm 2 was detected, which signifies that a maximum amount of the licorice roots was formed to nanofibers. figure 4 (a) shows that the airflow rate is increased with an increasing pore size, which signifies that the breathability of the mask membrane is improved because of the improved porosity of the mask membrane. it is also worth mentioning that the pore size of 75 nm, which is smaller than the size of covid-19, is needed to maintain a good breathability of 85 l/min [17] . moreover, the fabricated membrane allows good breathability across an extensive range of pressure drops as shown in figure 4 (b). a higher airflow resistance signifies a higher pressure drop that reduces the breathability of the face mask [18] . in this situation, an increasing airflow rate would not influence the filtration efficiency if the pore size of the mask membrane were maintained at a size smaller than the size of covid-19 as a consequence of the straining mechanism [20] . increasing the airflow rate affects the filtration efficiency if the pore size is larger than the particle size as for an n95 face mask with a pore size of 300 nm. most countries in the world have taken many precautionary measures against covid-19. government officials have been continuing to make efforts to reduce crowds in public places and many steps have been taken to ensure people's safety such as social distancing, reducing public transport, and the shutdown of offices and factories. this may reduce covid-19 cases, but the economic crisis is still going to worsen. to avoid the spread of covid-19 and ensure a sense of protection and wellbeing for all, personal hygiene must be preserved until an effective vaccine is produced. the face mask is one safety measure and there is a significant rise in the use of face masks every day, numbering in the millions, resulting in a high demand for materials. in this paper, we have proposed the potential of the licorice root membrane as a nanofiber that can be used in the production of a face mask. the porosity of the proposed mask is less than the size of covid19, thus, it is believed that this mask can help to prevent the spread of the virus. despite significant findings on the potential of licorice root membrane as a raw material for face masks, some limitations remain. for example, the performance of a mask depends on the fluidresistant, bacterial filtration and particulate filtration capacities. therefore, further comprehensive research is still necessary to explore these variables and give a clearer picture of their virus-resistant capacity. a quantitative assessment of the efficacy of surgical and n95 masks to filter the influenza virus in patients with acute influenza infection wearing face masks-the simple and effective way to block the infection source of covid-19 covid-19: face masks and human-to-human transmission efficacy of face mask in preventing respiratory virus transmission: a systematic review and meta-analysis airborne sars-cov-2 and the use of masks for protection against its spread in wuhan influenza viruses are transmitted via the air from the nasal respiratory epithelium of ferrets traditional chinese medicine treatment of covid-19 commentary: the antiviral and antimicrobial activities of licorice, a widely-used chinese herb glycyrrhizin, an active component of liquorice roots, and replication of sars-associated coronavirus water extract of licorice had anti-viral activity against the human respiratory syncytial virus in human respiratory tract cell lines antiviral and antitumor activity of licorice root extracts glycyrrhizic-acid-based carbon dots with high antiviral activity by multisite inhibition mechanisms electrospun poly (vinyl alcohol) nanofibers: effects of degree of hydrolysis and enhanced water stability glycyrrhizin as an antiviral agent against hepatitis c virus glycyrrhizin: an alternative drug for the treatment of covid-19 infection and the associated respiratory syndrome scope of natural plant extract to deactivate covid-19 pressure drop of filtering facepiece respirators: how low should we go a flexible nanoporous template for the design and development of reusable anti-covid-19 hydrophobic face masks testing of air permeability of distant knitted fabrics in the direction of their plane efficient and reusable polyamide-56 nanofiber/nets membrane with bimodal structures for air filtration key: cord-274201-9qsqj91d authors: matuschek, christiane; moll, friedrich; fangerau, heiner; fischer, johannes c.; zänker, kurt; van griensven, martijn; schneider, marion; kindgen-milles, detlef; knoefel, wolfram trudo; lichtenberg, artur; tamaskovics, bálint; djiepmo-njanang, freddy joel; budach, wilfried; corradini, stefanie; häussinger, dieter; feldt, torsten; jensen, björn; pelka, rainer; orth, klaus; peiper, matthias; grebe, olaf; maas, kitti; bölke, edwin; haussmann, jan title: the history and value of face masks date: 2020-06-23 journal: eur j med res doi: 10.1186/s40001-020-00423-4 sha: doc_id: 274201 cord_uid: 9qsqj91d in the human population, social contacts are a key for transmission of bacteria and viruses. the use of face masks seems to be critical to prevent the transmission of sars-cov-2 for the period, in which therapeutic interventions are lacking. in this review, we describe the history of masks from the middle age to modern times. in last few months, many communications were brought to the public that face masks are ineffective during a pandemic crisis. since april 27, 2020 face masks have become mandatory for shopping and in public transportation in germany. in the netherlands, it became mandatory only for public transportation, from june 1, 2020 onwards. however, in asian countries people have been wearing masks in public for ages. although new york and hong kong are both metropolitan areas, the corona virus pandemia was devastating in the us and not in hongkong. this fact alone implies a necessary, and a more distinguished view of the normative application of facemasks. in two manuscripts, we are now describing the use of masks during this viral pandemic. this first review describes the history of facemasks. the second will concentrate on benefits and risks by wearing facemasks in modern times. on march 17, 2020, this headline appeared in the new york times on an article regarding the role of face masks in times of the covid-19 outbreak. this is the most recent expression of the use of face masks. however, face masks have been used since the middle ages. there are pictures of medical professionals from the early modern age treating patients suffering from the bubonic plague wearing beak-like masks. these masks were supposedly filled with herbs such as clove or cinnamon as well as liquids and led to the term 'beak-doctors' [2] (fig. 1) . the doctors were dressed in black cloaks and dark hats and were considered the symbol of the deathly epidemic of the middle ages. their masks were meant to protect from the 'blight' , the miasma, which was considered the cause of the plague back then. it was proclaimed that spoiled air from the east had caused the epidemic. nevertheless, there is no proof that these 'plague-doctors with beak-like masks' really existed. there are two masks displayed in german museums that are suspected to be forgeries from a younger date. that indicates that the beak-doctors were in retrospect awarded a meaning they apparently did not have in reality [3] . heroic stories of the introduction of antisepsis by joseph lister (1827-1912) and the corresponding preliminary works by louis pasteur (1822-1895) or ignaz semmelweis (1818-1865) [4] have inspired movie productions for decades and had an impact on our culture of remembrance. in contrast, the bacteriologic era that influenced the development of surgery has only recently been analyzed for the german area by schlich et al. [5] . ever since the works of lister and pasteur, the surgical ward and its developing special disciplines were confronted with a trend-setting discourse about wound infections and their prohibition and containment. this began in 1870, as the 'hospital gangrene' was limiting the outcomes of operations, especially those concerning abdominal procedures and those involving bones. the introduction of mouth and nose coverage (mouth protection, face veils, face masks, mouth bandages) can be followed back to the turn-of-the-20 th -century. in 1897, the hygienist carl friedrich flügge (1847 flügge ( -1923 working in breslau at this time published his works on the development of droplet infections [6] [7] [8] as part of his research on the genesis of tuberculosis [7] . at that time, the respiratory system as a transmitter of germs came into focus of research and already mandated instructions to keep distance [7, 9] . in the same year, 1897, a cooperation work between flügge and theodor billroth's (1829-1894) disciple johannes von mikulicz (1850 mikulicz ( -1905 , who also worked in breslau since 1890, was published. their publication dealt with performing operations wearing a 'mouth bandage' . in here, mikulicz described a one-layered mask made of gauze [10] . mikulicz, who had already been responsible for the introduction of sterile gloves made from cloth, noted concerning the applicability of surgical masks: '…we breathed through it as easily as a lady wearing a veil in the streets… ' mikulicz' assistant hübner resumed the topic and described a two-layered mouth protection made of gauze that should prevent driblet spread. more studies regarding the germ content in the operating room air followed [11, 12] . until 1910, the application of face covers was not common in surgery and the general hospitals. nevertheless, an earlier illustration of a multilayer face mask made of gauze can be found in the surgical operating teachings of the british surgeon b.g.a. moynihan (1865-1936) (fig. 2) . in 1914, the surgeon fritz könig (1866 könig ( -1952 noted in a handbook on surgery for general practitioners: "…due to our experience of many years we consider their (mouth masks) -by the way quite irritatinguse altogether unnecessary. only those afflicted with a catarrh or angina should wear a mouth bandage when operating that is to be sterilised in steam. speaking should be limited and the direction of the operative field avoided…" [13] the surgical mask was used first in the operating rooms of germany and the usa in the 1920s. especially in endoscopic procedures or 'small surgery' , the mask was renounced for a long time. there was still no hint for a facemask in the book 'assistance for operating staff ' , that was widely read in german-speaking areas in 1926, while the processing of cystoscopies for instance, also taking place in the clinical use around 1900, was described extensively on several pages [14, 15] . one year later, martin kirschner (1879 kirschner ( -1942 , who held the chair for surgery in heidelberg, elaborately described the necessity of wearing a facemask in his multi-volume operational theory in the chapter 'measures to combat infections' [16] . in the following edition of the book 'assistance for operating staff ' published in 1935, facemasks were then mentioned [17] , which can probably be related to the increased number of studies on the reduction of germs [18, 19] . a similar situation applies for the united states. in that country, following the first world war, more and more research addressed facemasks with varying thickness [20] [21] [22] [23] . still, masks were not generally accepted, which can be seen in contemporary photographs [24] or paintings (figs. 3, 4 and 5) . while interns and nurses were already wearing facemasks made of cloth or gauze, the generation of head physicians rejected them, as well as rubber gloves, in all phases of an operation, as they were considered "irritating". in the middle of the 1930s, the research on the role of facemasks was continued in germany and the usa [25, 26] . only in the 1940s, washable and sterilizable masks gained acceptance in german and international surgery with only the number of gauze layers varying (2) (3) (3) (4) [27, 28] . beginning in the mid-1960s, the use of disposable items made of paper and fleece was introduced all over the world after this was started in the usa. still in the 1990s, there were only uncertain data available. therefore, an unresolved discussion was present between surgery and hospital hygiene, if wound infections could be reduced by the use of surgical mouth and nose protection [29, 30] . today, following the recommendations of the rki (german robert koch-institute for hygiene), the available data indicate that surgical facemasks lower the contamination of indoor air [31] . during the covid-19 pandemic, the use of facemasks seems to be an accepted procedure worldwide although a scientific discussion is going on up to now, which has its roots in the history of medicine and science. future research on efficiency and efficacy of long-term mask wearing outside of hospital settings is warranted and will allow for insights that are more detailed. daily life during the black death die pestarztmaske im deutschen medizinhistorischen museum ingolstadt die aetiologie, der begriff und die prophylaxis des kindbettfiebers the palgrave handbook of the history of surgery palgrave die verbreitung der phthise durch staubförmiges sputum und durch beim husten verspritzte tröpfchen zshr hyg infkrkh. 1899 ueber luftinfection durch beim husten, niesen und sprechen verspritzte tröpfchen zshr hyg infkrkh 1899 die uebertragung von infectionskrankheiten durch die luft das operieren in sterilisierten zwirnhandschuhen und mit mundbinde über die möglichkeit der wundinfektion vom munde aus und ihre verhütung durch operationsmasken contributo alla studio della flora bacteria nell die therapie des praktischen arztes erster band therapeutische fortbildung handreichungen für den operationssaal ratgeber für die vorbereitung chirurgischer operationen und das instrumentieren für schwestern, ärzte und studierende history of cystoscopy allgemeine und spezielle chirurgische operationslehre bd 1; 1927. s. 213-279 insb postoperative haemolytic streptococcus wound infections and their relation to haemolytic streptococcus carriers among operating personnel the protective qualities of the gauze face mask the value of the face mask and other measures droplet infection and its prevention by the face mask a bacteriological study of the efficiency of face masks the myths, the masks, and the men and women behind them uncovering the history of operating room attire through photographs untersuchungen über operationsschleier grundriß der gesamten chirurgie allgemeine chirurgie 1. abschnitt aseptik operative chirurgie new routines for prevention of postoperative infections. a review postoperative wound infections and surgical face masks: a controlled study publisher's note springer nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations this work is dedicated to dr. med. ewald matuschek and ruth matuschek. there was no funding for this investigation. all data and materials can be accessed via cm and fm. there was no ethics approval necessary because this is a review of the literature. all authors gave consent for the publication. all authors declare that they have no conflict of interest. heinrich-heine-university, duesseldorf, germany. 3 institute for transplant key: cord-324585-2rx84imv authors: konda, abhiteja; prakash, abhinav; moss, gregory a.; schmoldt, michael; grant, gregory d.; guha, supratik title: aerosol filtration efficiency of common fabrics used in respiratory cloth masks date: 2020-04-24 journal: acs nano doi: 10.1021/acsnano.0c03252 sha: doc_id: 324585 cord_uid: 2rx84imv [image: see text] the emergence of a pandemic affecting the respiratory system can result in a significant demand for face masks. this includes the use of cloth masks by large sections of the public, as can be seen during the current global spread of covid-19. however, there is limited knowledge available on the performance of various commonly available fabrics used in cloth masks. importantly, there is a need to evaluate filtration efficiencies as a function of aerosol particulate sizes in the 10 nm to 10 μm range, which is particularly relevant for respiratory virus transmission. we have carried out these studies for several common fabrics including cotton, silk, chiffon, flannel, various synthetics, and their combinations. although the filtration efficiencies for various fabrics when a single layer was used ranged from 5 to 80% and 5 to 95% for particle sizes of <300 nm and >300 nm, respectively, the efficiencies improved when multiple layers were used and when using a specific combination of different fabrics. filtration efficiencies of the hybrids (such as cotton–silk, cotton–chiffon, cotton–flannel) was >80% (for particles <300 nm) and >90% (for particles >300 nm). we speculate that the enhanced performance of the hybrids is likely due to the combined effect of mechanical and electrostatic-based filtration. cotton, the most widely used material for cloth masks performs better at higher weave densities (i.e., thread count) and can make a significant difference in filtration efficiencies. our studies also imply that gaps (as caused by an improper fit of the mask) can result in over a 60% decrease in the filtration efficiency, implying the need for future cloth mask design studies to take into account issues of “fit” and leakage, while allowing the exhaled air to vent efficiently. overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles. t he use of cloth masks, many of them homemade, 1,2 has become widely prevalent in response to the 2019− 2020 sars-cov-2 outbreak, where the virus can be transmitted via respiratory droplets. 3−6 the use of such masks is also an anticipated response of the public in the face of future pandemics related to the respiratory tract. however, there is limited data available today on the performance of common cloth materials used in such cloth masks, 7−12 particularly their filtration efficiencies as a function of different aerosol sizes ranging from ∼10 nm to ∼10 μm scale sizes. this is also of current significance as the relative effectiveness of different droplet sizes in transmitting the sars-cov-2 virus is not clear, and understanding the filtration response across a large bracketed size distribution is therefore important. 13 −16 in this paper, we report the results of experiments where we measure the filtration efficiencies of a number of common fabrics, as well as selective combinations for use as hybrid cloth masks, as a function of aerosol sizes ranging from ∼10 nm to 6 μm. these include cotton, the most widely used fabric in cloth masks, as well as fabric fibers that can be electrostatically charged, such as natural silk. respiratory droplets can be of various sizes 17, 18 and are commonly classified as aerosols (made of droplets that are <5 μm) and droplets that are greater than 5 μm. 3 although the fate of these droplets largely depends on environmental factors such as humidity, temperature, etc., in general, the larger droplets settle due to gravity and do not travel distances more than 1−2 m. 19 however, aerosols remain suspended in the air for longer durations due to their small size and play a key role in spreading infection. 14−16 the use of physical barriers such as respiratory masks can be highly effective in mitigating this spread via respiratory droplets. 20−22 filtration of aerosols follows five basic mechanisms: gravity sedimentation, inertial impaction, interception, diffusion, and electrostatic attraction. 23, 24 for aerosols larger than ∼1 μm to 10 μm, the first two mechanisms play a role, where ballistic energy or gravity forces are the primary influence on the large exhaled droplets. as the aerosol size decreases, diffusion by brownian motion and mechanical interception of particles by the filter fibers is a predominant mechanism in the 100 nm to 1 μm range. for nanometer-sized particles, which can easily slip between the openings in the network of filter fibers, electrostatic attraction predominates the removal of low mass particles which are attracted to and bind to the fibers. electrostatic filters are generally most efficient at low velocities such as the velocity encountered by breathing through a face mask. 25 there have been a few studies reported on the use of cloth face masks mainly during or after the influenza pandemic in 2009; [8] [9] [10] [11] [12] 26 however, there is still a lack of information that includes (i) the performance of various fabrics as a function of particle size from the nanoscale to the micron sized (particularly important because this covers the ∼10 nm to ∼5 μm size scale for aerosols) and (ii) the effect of hybrid multilayer approaches for masks that can combine the benefits of different filtering mechanisms across different aerosol size ranges. 9, 26 these have been the objectives of the experimental work described in this paper. in addition, we also point out the importance of fit (that leads to gaps) while using the face mask. 27, 28 the experimental apparatus (see figure 1 ) consists of an aerosol generation and mixing chamber and a downstream collection chamber. the air flows from the generation chamber to the collection chamber through the cloth sample that is mounted on a tube connecting the two chambers. the aerosol particles are generated using a commercial sodium chloride (nacl) aerosol generator (tsi particle generator, model #8026), producing particles in the range of a few tens of nanometers to approximately 10 μm. the nacl aerosol based testing is widely used for testing face respirators in compliance with the niosh 42 cfr part 84 test protocol. 29,30 two different particle analyzers are used to determine particle size dimensions and concentrations: a tsi nanoscan smps nanoparticle sizer (nanoscan, model #3910) and a tsi optical particle sizer (ops, model #3330) for measurements in the range of 10 to 300 nm and 300 nm to 6 μm, respectively. particles are generated upstream of the cloth sample, whose filtration properties are to be tested, and the air is drawn through the cloth using a blower fan which can be controlled in order to vary the airflow rate. effective area of the cloth sample during the tests was ∼59 cm 2 . measurements of particle size and distribution were made by sampling air at a distance of 7.5 cm upstream and 15 cm downstream of the cloth sample. the differential pressures and air velocities were measured using a tsi digital manometer (model #axd620) and a tsi hot wire anemometer (model #avm410). the differential pressure (δp) across the sample material is an indicator of the comfort and breathability of the material when used as a face mask. 31 tests were carried out at two different airflows: 1.2 and 3.2 cfm, representative of respiration rates at rest (∼35 l/min) and during moderate exertion (∼90 l/min), respectively. 32 the effect of gaps between the contour of the face and the mask as caused by an improper fit will affect the efficiency of any face mask. 21, 27, 28, 33 this is of particular relevance to cloth and surgical masks that are used by the public and which are generally not "fitted", unlike n95 masks or elastomeric respirators. a preliminary study of this effect was explored by drilling holes (symmetrically) in the connecting tube onto which the fabric (or a n95 or surgical mask) is mounted. the holes, in proximity to the sample (figure 1 ), resulted in openings of area ∼0.5−2% of the active sample area. this, therefore, represented "leakage" of the air around the mask. although the detailed transmission specifics of sars-cov-2 virus are not well understood yet, droplets that are below 5 μm are considered the primary source of transmission in a respiratory infection, 13,15,34 and droplets that are smaller than figure 1 . schematic of the experimental setup. a polydisperse nacl aerosol is introduced into the mixing chamber, where it is mixed and passed through the material being tested ("test specimen"). the test specimen is held in place using a clamp for a better seal. the aerosol is sampled before (upstream, c u ) and after (downstream, c d ) it passes through the specimen. the pressure difference is measured using a manometer, and the aerosol flow velocity is measured using a velocity meter. we use two circular holes with a diameter of 0.635 cm to simulate the effect of gaps on the filtration efficiency. the sampled aerosols are analyzed using particle analyzers (ops and nanoscan), and the resultant particle concentrations are used to determine filter efficiencies. www.acsnano.org article 1 μm tend to stay in the environment as aerosols for longer durations of up to 8 h. 19 aerosol droplets containing the sars-cov-2 virus have been shown to remain suspended in air for ∼3 h. 13, 35 we have therefore targeted our experimental measurements in the important particle size range between ∼10 nm and 6 μm. we tested the performance of over 15 natural and synthetic fabrics that included materials such as cotton with different thread counts, silk, flannel, and chiffon. the complete list is provided in the materials and methods section. for comparison, we also tested a n95 respirator and surgical masks. additionally, as appropriate, we tested the efficiency of multiple layers of a single fabric or a combination of multiple fabrics for hybrid cloth masks in order to explore combinations of physical filtering as well as electrostatic filtering. we determine the filtration efficiency of a particular cloth as a function of particle size ( figure 2 ) by measuring the concentration of the particles upstream, c u (figure 2a ,b) and the concentration of the particle downstream, c d (figure 2c ,d). concentrations were measured in the size ranges of 10−178 nm (using the nanoscan tool) and 300 nm to 6 μm (using the optical particle sizer tool). the representative example in figure 2 shows the case for a single layer of silk fabric, where the measurements of c u and c d were carried out at a flow rate of 1.2 cfm. following the procedure detailed in the materials and methods section, we then estimated the filtration efficiency of a cloth from c u and c d as a function of aerosol particle size. the results plotted in figure 3a are the filtration efficiencies for cotton (the most common material used in cloth masks) with different thread counts (rated in threads per inchtpi and representative of the coarseness or fineness of the fabric). we compare a moderate (80 tpi) thread count quilter's cotton (often used in do-it-yourself masks) with a high (600 tpi) cotton fabric sample. additionally, we also measured the transmission through a traditional cotton quilt where two 120 tpi quilter's cotton sheets sandwich a ∼0.5 cm batting (90% cotton−5% polyester−5% other fibers). comparing the two figure 2 . particle concentration as a function of particle size at a flow rate of 1.2 cfm. plots showing the particle concentration (in arbitrary units) upstream and downstream through a single layer of natural silk for particle sizes <300 nm (a,c) and between 300 nm and 6 μm (b,d). each bin shows the particle concentration for at least six trials. the particle concentrations in panels (b) and (d) are given in log scale for better representation of the data. the y-axis scales are the same for panels "a" and "c"; and for panels "b" and "d". acs nano www.acsnano.org article cotton sheets with different thread counts, the 600 tpi cotton is clearly superior with >65% efficiency at <300 nm and >90% efficiency at >300 nm, which implies a tighter woven cotton fabric may be preferable. in comparison, the single-layer 80 tpi cotton does not perform as well, with efficiencies varying from ∼5 to ∼55% depending on the particle size across the entire range. the quilt, a commonly available household material, with a fibrous cotton batting also provided excellent filtration across the range of particle sizes (>80% for <300 nm and >90% for >300 nm). electrostatic interactions are commonly observed in various natural and synthetic fabrics. 36, 37 for instance, polyester woven fabrics can retain more static charge compared to natural fibers or cotton due to their lower water adsorption properties. 36 the electrostatic filtering of aerosols have been well studied. 38 as a result, we investigated three fabrics expected to possess moderate electrostatic discharge value: natural silk, chiffon (polyester−spandex), and flannel (cotton−polyester). 36 the results for these are shown in figure 3b . in the case of silk, we made measurements through one, two, and four layers of the fabric as silk scarves are often wrapped in multiple layers around the face (the results for two layers of silk are presented in figure s1 (supporting information) and omitted from this figure) . in all of these cases, the performance in filtering nanosized particles <300 nm is superior to performance in the 300 nm to 6 μm range and particularly effective below ∼30 nm, consistent with the expectations from the electrostatic effects of these materials. increasing the number of layers (as the error bars on the <300 nm measurements are higher, particularly for samples with high filtration efficiencies because of the small number of particles generated in this size range, the relatively poorer counting efficiency of the detector at <300 nm particle size, and the very small counts downstream of the sample. the sizes of the error bars for some of the data points (>300 nm) are smaller than the symbol size and hence not clearly visible. shown for silk in figure 3b ), as expected, improves the performance. we performed additional experiments to validate this using the 600 tpi cotton and chiffon ( figure s1 ). we note that the performance of a four-layer silk composite offers >80% filtration efficiency across the entire range, from 10 nm to 6 μm. in figure 4a , we combine the nanometer-sized aerosol effectiveness (for silk, chiffon, and flannel) and wearability (of silk and chiffon because of their sheer nature) with the overall high performance of the 600 tpi cotton to examine the filtration performance of hybrid approaches. we made measurements for three variations: combining one layer 600 tpi cotton with two layers of silk, two layers of chiffon, and one layer of flannel. the results are also compared with the performance of a standard n95 mask. all three hybrid combinations performed well, exceeding 80% efficiency in the <300 nm range, and >90% in the >300 nm range. these cloth hybrids are slightly inferior to the n95 mask above 300 nm, but superior for particles smaller than 300 nm. the n95 respirators are designed and engineered to capture more than 95% of the particles that are above 300 nm, 39, 40 and therefore, their underperformance in filtering particles below 300 nm is not surprising. it is important to note that in the realistic situation of masks worn on the face without elastomeric gasket fittings (such as the commonly available cloth and surgical masks), the showing the filtration efficiencies of a surgical mask and cotton/silk with (dashed) and without a gap (solid). the gap used is ∼1% of the active mask surface area. the error bars on the <300 nm measurements are higher, particularly for samples with high filtration efficiencies because of the small number of particles generated in this size range, the relatively poorer counting efficiency of the detector at <300 nm particle size, and the very small counts downstream of the sample. the sizes of the error bars for some of the data points (>300 nm) are smaller than the symbol size and hence not clearly visible. www.acsnano.org article presence of gaps between the mask and the facial contours will result in "leakage" reducing the effectiveness of the masks. it is well recognized that the "fit" is a critical aspect of a highperformance mask. 27, 28, 33, 41 earlier researchers have attempted to examine this qualitatively in cloth and other masks through feedback on "fit" from human trials. 11, 12 in our case, we have made a preliminary examination of this effect via the use of cross-drilled holes on the tube holding the mask material (see figure 1 ) that represents leakage of air. for example, in figure 4b , we compare the performance of the surgical mask and the cotton/silk hybrid sample with and without a hole that represents about ∼1% of the mask area. whereas the surgical mask provides moderate (>60%) and excellent (close to 100%) particle exclusion below and above 300 nm, respectively, the tests carried out with the 1% opening surprisingly resulted in significant drops in the mask efficiencies across the entire size range (60% drop in the >300 nm range). in this case, the two holes were ∼0.635 cm in diameter and the mask area was ∼59 cm 2 . similar trends in efficiency drops are seen in the cotton/ silk hybrid sample, as well. hole size also had an influence on the filtration efficiency. in the case of an n95 mask, increasing hole size from 0.5 to 2% of the cloth sample area reduced the weighted average filtration efficiency from ∼60 to 50% for a particle of size <300 nm. it is unclear at this point whether specific aerodynamic effects exacerbate the "leakage" effects when simulated by holes. its determination is outside the scope of this paper. however, our measurements at both the high flow (table s1 ). the filtration efficiencies of all of the samples that we measured at both 1.2 cfm and 3.2 cfm are detailed in the supporting information (figures s2−s4) . in table 1 , we summarize the key findings from the various fabrics and approaches that we find promising. average filtration efficiencies (see materials and methods section for further detail) in the 10−178 nm and 300 nm to 6 μm range are presented along with the differential pressures measured across the cloths, which represents the breathability and degree of comfort of the masks. the average differential pressure across all of the fabrics at a flow rate of 1.2 cfm was found to be 2.5 ± 0.4 pa, indicating a low resistance and represent conditions for good breathability (table 1) . 31 as expected, we observed an increase in the average differential pressures for the higher flow rate (3.2 cfm) case (table s1) . guidance. we highlight a few observations from our studies for cloth mask design: fabric with tight weaves and low porosity, such as those found in cotton sheets with high thread count, are preferable. for instance, a 600 tpi cotton performed better than an 80 tpi cotton. fabrics that are porous should be avoided. materials such as natural silk, a chiffon weave (we tested a 90% polyester−10% spandex fabric), and flannel (we tested a 65% cotton−35% polyester blend) can likely provide good electrostatic filtering of particles. we found that four layers of silk (as maybe the case for a wrapped scarf) provided good protection across the 10 nm to 6 μm range of particulates. combining layers to form hybrid masks, leveraging mechanical and electrostatic filtering may be an effective approach. this could include high thread count cotton combined with two layers of natural silk or chiffon, for instance. a quilt consisting of two layers of cotton sandwiching a cotton−polyester batting also worked well. in all of these cases, the filtration efficiency was >80% for <300 nm and >90% for >300 nm sized particles. the filtration properties noted in (i) through (iii) pertain to the intrinsic properties of the mask material and do not take into account the effect of air leaks that arise due to improper the filtration efficiencies are the weighted averages for each size rangeless than 300 nm and more than 300 nm. www.acsnano.org article "fit" of a mask on the user's face. it is critically important that cloth mask designs also take into account the quality of this "fit" to minimize leakage of air between the mask and the contours of the face, while still allowing the exhaled air to be vented effectively. such leakage can significantly reduce mask effectiveness and are a reason why properly worn n95 masks and masks with elastomeric fittings work so well. in conclusion, we have measured the filtration efficiencies of various commonly available fabrics for use as cloth masks in filtering particles in the significant (for aerosol-based virus transmission) size range of ∼10 nm to ∼6 μm and have presented filtration efficiency data as a function of aerosol particle size. we find that cotton, natural silk, and chiffon can provide good protection, typically above 50% in the entire 10 nm to 6.0 μm range, provided they have a tight weave. higher threads per inch cotton with tighter weaves resulted in better filtration efficiencies. for instance, a 600 tpi cotton sheet can provide average filtration efficiencies of 79 ± 23% (in the 10 nm to 300 nm range) and 98.4 ± 0.2% (in the 300 nm to 6 μm range). a cotton quilt with batting provides 96 ± 2% (10 nm to 300 nm) and 96.1 ± 0.3% (300 nm to 6 μm). likely the highly tangled fibrous nature of the batting aids in the superior performance at small particle sizes. materials such as silk and chiffon are particularly effective (considering their sheerness) at excluding particles in the nanoscale regime (<∼100 nm), likely due to electrostatic effects that result in charge transfer with nanoscale aerosol particles. a four-layer silk (used, for instance, as a scarf) was surprisingly effective with an average efficiency of >85% across the 10 nm −6 μm particle size range. as a result, we found that hybrid combinations of cloths such as high threads-per-inch cotton along with silk, chiffon, or flannel can provide broad filtration coverage across both the nanoscale (<300 nm) and micron scale (300 nm to 6 μm) range, likely due to the combined effects of electrostatic and physical filtering. finally, it is important to note that openings and gaps (such as those between the mask edge and the facial contours) can degrade the performance. our findings indicate that leakages around the mask area can degrade efficiencies by ∼50% or more, pointing out the importance of "fit". opportunities for future studies include cloth mask design for better "fit" and the role of factors such as humidity (arising from exhalation) and the role of repeated use and washing of cloth masks. in summary, we find that the use of cloth masks can potentially provide significant protection against the transmission of particles in the aerosol size range. materials. all of the fabrics used as well as the surgical masks and n95 respirators tested are commercially available. we used 15 different types of fabrics. this included different types of cotton (80 and 600 threads per inch), cotton quilt, flannel (65% cotton and 35% polyester), synthetic silk (100% polyester), natural silk, spandex (52% nylon, 39% polyester, and 9% spandex), satin (97% polyester and 3% spandex), chiffon (90% polyester and 10% spandex), and different polyester and polyester−cotton blends. specific information on the composition, microstructure, and other parameters can be found in the supporting information (table s2) . polydisperse aerosol generation. a polydisperse, nontoxic nacl aerosol was generated using a particle generator and introduced into the mixing chamber along with an inlet for air. the aerosol is then mixed in the mixing chamber with the help of a portable fan. the particle generator produces particles sizes in the ranges of 10 nm to 10 μm. detection of aerosol particles. the particles were sampled both upstream (c u , before the aerosol passes through the test specimen) and downstream (c d , after the aerosol passes through the test specimen) for 1 min. the samples collected from the upstream and downstream are separately sent to the two particle sizers to determine a particle concentration (pt/cc). each sample is tested seven times following the minimum sample size recommended by the american industrial hygiene association exposure assessment sampling guidelines. 42 we observed a significantly lower particle count in the upper size distribution for both of the data sets, that is, for particles greater than 178 nm for the data from the tsi nanoscan analyzer and greater than 6 μm for the data from tsi ops analyzer. we exclude the data above these thresholds for all of the studies reported due to the extremely low counts. we categorize our data based on these two particle analyzersindividually the two plots (figure 2a,b) show two size distributionsparticles smaller than 300 nm and particles larger than 300 nm. two different flow rates of 1.2 cfm (a face velocity of 0.1 m/s) and 3.2 cfm (a face velocity of 0.26 m/s) were used that corresponded to rates observed at rest to moderate activity, respectively. the velocity of the aerosol stream was measured at ∼5 cm behind where the test specimen would be mounted using a velocity meter. differential pressure. the differential pressure (δp) across the test specimen was measured ∼7.5 cm away on either side of the material being tested using a micromanometer. the δp value is an estimate of the breathability of the fabric. data analysis. the particle concentrations from seven consecutive measurements were recorded and divided into multiple bins 10 for nanoparticle sizer (dimensions in nm: 10−13, 13−18, 18−24, 24−32, 32−42, 42−56, 56−75, 75−100, 100−133, 133−178) and 6 for optical particle sizer (dimensions in μm: 0.3−0.6, 0.6−1.0, 1.0− 2.0, 2.0−3.0, 3.0−4.0, 4.0−6.0). the seven measurements for each bin were subjected to one iteration of the grubbs' test with a 95% confidence interval to remove at most one outlier per bin. this improves the statistical viability of the data. following grubbs' test, average concentrations were used to calculate the filtration efficiencies as described below. filtration efficiency. the filtration efficiency (fe) of different masks was calculated using the following formula: where c u and c d are the mean particle concentrations per bin upstream and downstream, respectively. to account for any possible drifts in the aerosol generation, we measured upstream concentrations before and after the downstream measurement and used the average of these two upstream values to calculate c u (for runs that did not include a gap). we do not measure upstream concentration twice when the run included a gap. the error in fe was calculated using the quadrature rule of error propagation. due to noise in the measurements, some fe values were below 0, which is unrealistic. as such, negative fe values were removed from consideration in figures and further calculations. in addition to the fe curves, we computed an aggregate filter efficiency for each test specimen. to do this, we took a weighted average of fe values weighted by the bin width for the two particle size ranges (<300 nm and >300 nm). these values are reported in table 1 and table s1 . the supporting information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.0c03252. filtration efficiencies for various fabrics tested at two different flow rates and the effect of layering on the filtration efficiencies of chiffon, silk, and 600 tpi cotton; detailed information on various fabrics used (pdf) acs nano www.acsnano.org article how to sew a fabric face mask transmission routes of respiratory viruses among humans exhalation of respiratory viruses by breathing, coughing, and talking ) national academies of sciences. medicine. rapid expert consultation on the possibility of bioaerosol spread of sars-cov-2 for the covid-19 pandemic a cluster randomised trial of cloth masks compared with medical masks in healthcare workers evaluating the efficacy of cloth facemasks in reducing particulate matter exposure simple respiratory protection-evaluation of the filtration performance of cloth masks and common fabric materials against 20−1000 nm size particles testing the efficacy of homemade masks: would they protect in an influenza pandemic? professional and home-made face masks reduce exposure to respiratory infections among the general population airborne transmission of sars-cov-2: the world should face the reality transmission potential of sars-cov-2 in viral shedding observed at the university of nebraska documentary research of human respiratory droplet characteristics. procedia eng world health organization. annex c -respiratory droplets. in natural ventilation for infection control in health-care settings droplet fate in indoor environments, or can we prevent the spread of infection? indoor air reducing risk of airborne transmitted infection in hospitals by use of hospital curtains effectiveness of facemasks to reduce exposure hazards for airborne infections among general populations respiratory virus shedding in exhaled breath and efficacy of face masks aerosol technology: properties, behavior, and measurement of airborne particles 21 -aerosol sample applications and field studies 5 -filtration mechanisms comparison of filtration efficiency and pressure drop in anti-yellow sand masks, quarantine masks particle size-dependent leakage and losses of aerosols in respirators nanoparticle penetration through filter media and leakage through face seal interface of n95 a comparison of total inward leakage measured using sodium chloride (nacl) and corn oil aerosol methods for air-purifying respirators title 42: public health, part 84approval of respiratory protective devices. code of federal regulations 35the determination of the air permeability of fabrics air flow measurements on human subjects with and without respiratory resistance at several work rates performance of an n95 filtering facepiece particulate respirator and a surgical mask during human breathing: two pathways for particle penetration airborne contagion and air hygiene: an ecological study of droplet infections covid-19: a call for physical scientists and engineers 37) frederick, e. r. fibers, filtration and electrostatics -a review of the new technology experimental study of electrostatic aerosol filtration at moderate filter face velocity do n95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks? manikin-based performance evaluation of n95 filtering-facepiece respirators challenged with nanoparticles reusable elastomeric respirators in health care: considerations for routine and surge use a strategy for assessing and managing occupational exposures key: cord-269568-vwkawh6x authors: ten hulzen, richard d.; fabry, david a. title: impact of hearing loss and universal face masking in the covid-19 era. date: 2020-08-03 journal: mayo clin proc doi: 10.1016/j.mayocp.2020.07.027 sha: doc_id: 269568 cord_uid: vwkawh6x nan abbreviations: covid-19 = coronavirus disease 2019; db = decibel; ed = emergency department; ffp = filtering face piece; fm = frequency modulation; hz = hertz; icu = intensive care unit; n95 mask = a particulate-filtering face mask that filters at least 95% of airborne particles; ppe = personal protective equipment; psaps -personal sound amplification products; sars-cov-2 = severe acute respiratory syndrome-coronavirus-2. in the current coronavirus disease 2019 (covid-19) pandemic, health and government officials are encouraging, even mandating, community-wide face mask wearing (i.e., universal masking) to reduce potential pre-symptomatic or asymptomatic transmission of severe acute respiratory syndromecoronavirus-2 (sars-cov-2) to others. there are three major categories of masks being used to limit the airborne transmission of large respiratory droplets and infectious agents: a respirator, or filtering face piece (ffp), such as a n95 mask; medical face masks, such as a surgical or procedure mask; and nonmedical masks, such as commercially-or self-made masks usually made of cloth or other textiles. based on mechanistic plausibility and the desire to reduce sars-cov-2 transmission and community impact, universal masking is recommended as a means of source control of both symptomatic and pre-symptomatic/asymptomatic individuals to prevent the spread of infectious respiratory droplets to others. in addition to universal masking, the community can mitigate the risk of transmitting and acquiring sars-cov-2 by physical distancing (> 6 feet apart), remaining at home, avoiding crowded or public places, working remotely from home, respiratory etiquette, frequent handwashing, and avoiding unnecessary hand-face contact. 1 health care facilities may also restrict family members and interpreters from accompanying patients during surgery, emergency department (ed) visits, intensive care unit (icu) stays, or hospitalizations. while these measures arguably are epidemiologically-appropriate, the negative impact these measures have had on the short supply of masks and other personal protective equipment (ppe) has been widely reported. in addition, universal masking is a barrier to clear empathetic communication. we'd like to call attention to the negative impacts of universal masking and social distancing in both health-care and community settings for individuals with hearing loss. approximately 14.1% of american adults (27.7 million) aged 18 and over report some difficulty hearing. 2 hearing loss impacts all age groups, yet it is more prevalent among unscreened older adults-who are also likely to be without hearing assistance. for 60-69 year-olds, the prevalence for hearing loss affecting speech intelligibility was 39.3%. 2 in addition, covid-19 fatality rates are higher in older adults who are frail with other comorbidities. current policies often require patients to be unaccompanied by supporting family members. this can be detrimental to effective communication, patient safety, and quality healthcare with individuals with hearing loss who cannot understand attenuated and distorted speech nor gain clues from lip-reading and facial expressions due to universal masking. a recent study showed each type of mask wearing causes a low-pass filter effect attenuating the higher frequencies (2000-7000 hertz, or db for the n95 mask (respirator/ffp). 3 while both age-related hearing loss and ffp masking portend substantial high-frequency region (2000-4000 hz) inaudibility and speech understanding reduction compared to normal hearing individuals when no mask is worn, the addition of a noisy background setting (e.g., ed/icu) further confounds this and makes communication extremely difficult, if not impossible. social distancing also has an impact on speech audibility. sounds rapidly become quieter as they travel away from their sources. the decibel (db) scale logarithmically quantitates the relative intensities of sound-a sound with an intensity of half that of a reference sound corresponds to a decrease of little more than 3 db. the inverse square law states that doubling the distance reduces the sound intensity to a quarter of its initial value. if the distance is doubled, then a 6 db reduction in sound intensity is noted. while conversational distances between two talkers in the united states typically ranges from 1.5 to 3 feet, the currently recommended social distancing of at least 6 feet (which translates to a doubling or even quadrupling of the distance) means the sound pressure level drops by 6 to 12 db, or more. social healthcare professionals should recognize that, with the loss of visual cues (i.e., lip reading) and support systems (e.g., family members), current covid-19 policies such as universal masking, social distancing, and unaccompanied patients may "unmask" significant hearing loss-related issues that previously had been diminished or ignored. personal sound amplification products (psaps) tend to work best for individuals with rather mild hearing loss, while those with more advanced hearing loss may benefit from further audiologic evaluation for hearing aids or even cochlear implants. hospitals and clinics may wish to consider loaner amplification systems (e.g., hearing aids) or use a fm system where the physician uses a microphone lanyard)-however this may be a challenging endeavor given the issues of cost, device decontamination, and potential cross-infection. additional resources and temporary recommendations for healthcare facilities are continually updated and available online (https://www.nad.org/covid19-communication-access-recs-for -hospital/). 6 healthcare professionals • speak slightly louder, and with a minimally-reduced rate • rephrase-rather than repeating the same words, shouting, exaggerated pronunciation, etc. • take turns when speaking • optimize positioning (i.e., face-to-face, not moving around or walking) • use low-tech methods (e.g., pen-and-paper, clear partitions) • use high-tech methods (e.g., wi-fi enabled tablets, video chat apps on smartphones) • use video-conferencing platforms (e.g., telemedicine, unmasked, without ppe) • use clear (or clear-paneled) masks to improve visibility of facial expressions / lip-reading cues • use personal sound amplification products (psaps) • use loaner hearing aids or frequency modulation (fm) systems along with a microphone lanyard • use scribes or professional support staff to assist healthcare professionals with hearing loss a fm = frequency modulation; ppe = personal protective equipment; psaps = personal sound amplification products european centre for disease prevention and control declining prevalence of hearing loss in us adults aged 20 to 69 years speech blocked by surgical masks becomes a more important issue in the era of covid-19. the hearing review effect of facemasks on empathy and relational continuity: a randomized controlled trial in primary care time to take hearing loss seriously covid-19: deaf and hard of hearing communication access recommendations for the hospital. nad website key: cord-275693-ej76fsxa authors: stanislau affonso de araujo, e.; maria bernardes henriques amaral, f.; park, d.; paola ceraldi cameira, a.; augustinho muniz da cunha, m.; gutierrez karl, e.; henderson, s. j. title: teach, and teach and teach: does the average citizen use masks correctly during daily activities? results from an observational study with more than 12,000 participants date: 2020-06-28 journal: nan doi: 10.1101/2020.06.25.20139907 sha: doc_id: 275693 cord_uid: ej76fsxa covid-19 is a new disease with no treatment and no vaccine so far. the pandemic is still growing in many areas. among the core measures to prevent disease spread is the use of face masks. we observed 12,588 people in five brazilian cities within the baixada santista metropolitan area. even though this is densely populated region and heavily impacted by covid-19 with a high risk population, only 45.1% of the observed population wore in face masks in a correct way, and another 15.5% simply did not use masks at all. the remainder used masks incorrectly, which is evidence of the worst scenario of people believing that they are protected when they are not. this is among the first studies, to the best of our knowledge, that measures real life compliance with face masks during this covid-19 pandemic. it is our conclusion that it is paramount to first control the virus before allowing people back in the streets. we should not assume that people will wear masks properly. equally important is to instruct and sensitize people on how to use face masks and why it is important. the impact of covid-19 has been enormous; everyone has had to change their social and health behaviors. nonetheless, with every new day, covid-19 becomes an easier and less frightening subject for the less informed. especially with the need for daily income, the lack of social support for the stay at home policy, and in some countries like brazil, the political misguidance contrary to the recommendations of the science and health authorities [1] , public pressure has mounted to end the quarantine. some brazilian cities are arranging the progressive reopening of commercial areas and allowing people to move freely about town. as the quarantine ends, with the numbers of cases and deaths on the rise, it has now become obligatory to wear a face mask. the baixada santista metropolitan area is an immense harbor region (the largest in latin america), providing an oil and industrial area close to são paulo, with a large retired population of 60+ years in age. covid-19 is highly prevalent with rising deaths (1,706 cases/100,000 inhabitants and 65.3 deaths/100,000, as of june 20, 2020, for the city of santos) [2] . although a population-based serologic survey conducted in the region every two weeks in the last two months (since june 11, 2020) showed a variation in anti-sars-cov-2 antibodies from 1.4 to 6.6%, the region still eased on the social distancing rules. due to the strategic nature of the region, its aging population, and the growing numbers of cases, and antibodies prevalence, the impact of covid-19 is growing rapidly and perilously. for a proper risk assessment, it is critical to understand the degree of public compliance with protective measures. the face mask is a cornerstone measure to protect against the covid-19 infection [3] . to evaluate if, how often, and in what way people wear their face masks, we conducted an observational study in five major cities in the baixada santista metropolitan area with a sample of over 12,000 observations. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted june 28, 2020. . https://doi.org/10.1101/2020.06.25.20139907 doi: medrxiv preprint 3 of 9 from june 17th to 19th, 2020, medical student researchers went to large commercial streets in the cities of santos, são vicente, cubatão, guarujá, and praia grande. for three consecutive days, for a period of one hour, the same researcher occupied the same spot on the same street, at the same time, and observed and recorded if, how many, and in what way, people were wearing their face masks. the sample size was based on the numbers of people at streets seen and recorded during the specified hours of observation at the specified place, which reflected the real life scenario for an average weekday. to guard against observer bias, the researchers were included in determining the categories of face mask use, and we ensured consensus about these categories before the study began. the following categories were observed: people wearing masks covering mouth and nose, firmly adjusted; or individuals wearing a mask with their nose and/or mouth exposed; people not wearing masks; others were wearing a poorly fitting mask; and, finally, people who touch their masks during use. results were plotted and analyzed in total and by city. role of the funding source: there were no funding sources for this study. table 1 (by number and percentage) and figure 1 (by percentage) display the research results by city and in total. overall, an average of 45.1% of the people observed wore their masks properly, within a city by city range of 39.1% to 63.5%. within the remaining 54.9%, 15.5% wore no mask (ranging from 12.7% to 18.8%), 12.9% wore masks but exposed their mouth and nose (range: 9.9% to 17.6%), 12.0% exposed their nose only (7.9% to 16.6%), 17.8% touched their mask during use (0.0% to 14.0%), and 6.5% wore poorly fitted masks (1.2% to 10.7%). the number of observations across the five cities was similar from 2,270 people (18.0%) in são vicente to 3055 (24.6%) in santos. insert table 1 here insert figure 1 here . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted june 28, 2020. . https://doi.org/10.1101/2020.06.25.20139907 doi: medrxiv preprint 4 of 9 at the present time, there is little, if any, research data on face mask compliance worn to prevent the spread of covid-19. in this study, over three consecutive days, we observed 12,588 people in the streets wearing, or not, masks in their routine lives. overall, only 45.1% of the people observed wore their masks properly, 39.4% wore their masks improperly, and 15.5% did not wear masks at all. the 39.4% who were wearing masks improperly were likely to be as dangerous as those not wearing a mask. this suggests that many mask-wearing people were feeling safe, but in reality, were not, and therefore risking presence in the streets in an inadvisable fashion. non-pharmacological measures are the main line of defense against covid-19 [3] . several barriers-physical or behavioral-should exist between the susceptible host and sars-cov-2. face masks have grown in relevance during this pandemic, particularly going from health care facilities to the average people daily activities. face masks are now a cornerstone in prevention, no matter who or where the need exists. nevertheless, face masks are new for the public. face masks are not comfortable to wear, and they require a new routine for how to wear, how to remove, how to preserve and clean, and so forth. many people complain of a lack of oxygen while wearing masks. therefore, it may be overly optimistic to count on public compliance with face masks as a tool to prevent infection and as a measure to make it safe to relax hard social distancing. our results are quite disturbing. we found that only 45.1% of people wore face masks properly and safely in a research sample observed in a region with significant prevalence of covid-19, among people at high risk of infection (because of poverty and high prevalence) and complications (due to age and pre-existing health conditions). according some mathematical models, more than 80% of people must wear a face mask properly for efficacy in covid-19 spread prevention [4] . as a public health measure and the successful defense against the spread of covid-19, the use of masks to protect the public, in lieu of quarantine, depends on each individual adhering to proper use [5] . we must ask ourselves: who are we deceiving with the false . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted june 28, 2020. . https://doi.org/10.1101/2020.06.25.20139907 doi: medrxiv preprint 5 of 9 belief of high compliance? before we move to some plan of further relaxing control measures, it is clear that safe social distancing is still a critical target to be achieved in order to reduce circulation of the virus. these research results from baixada santista, revealing inadequate public compliance, suggest that we are playing with fire and jeopardizing people lives, and quite literally, offering them over to the virus. prevention of covid-19, like some other infectious diseases, (so far) lacks an effective vaccine and therefore requires a change in public behavior. hiv taught us how hard is to avoid risk with a single behavioral change, such as using a condom. so, before we move ahead with peace of mind, and erroneously assume that people will wear masks routinely and properly, it is paramount that we teach, and teach, and teach use of face masks, and explain why one's life depends on proper use. to the best of our knowledge, this study is the first to observe covid-19 prevention from the perspective of actual observed compliance. this was an observational study, in a single region with no intervention. the generalizability of this study is unknown, however, this study can be easily replicated at low cost in other regions around the world. observational studies are useful as preliminary but rapid research to raise significant red flags in current efforts against covid-19. the authors have no conflicts of interests to declare. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted june 28, 2020. . https://doi.org/10.1101/2020.06.25.20139907 doi: medrxiv preprint 6 of 9 [a] concept of the study, wrote manuscript, prepared dataset [b] field observation [c] reviewed and prepared manuscript . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted june 28, 2020. . https://doi.org/10.1101/2020.06.25.20139907 doi: medrxiv preprint so what especial covid-19 -dados por município physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis to mask or not to mask: modeling the potential for face mask use by the general public to curtail the covid-19 pandemic cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity the copyright holder for this preprint this version posted june 28, 2020. . https://doi.org/10.1101/2020.06.25.20139907 doi: medrxiv preprint 8 of 9. cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted june 28, 2020. . https://doi.org/10.1101/2020.06.25.20139907 doi: medrxiv preprint 9 of 9 . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted june 28, 2020. . https://doi.org/10.1101/2020.06.25.20139907 doi: medrxiv preprint key: cord-305282-x2zzzw43 authors: suen, c. y.; leung, h. h.; lam, k. w.; hung, k. p.; chan, m. y.; kwan, j. k. c. title: feasibility of reusing surgical mask under different disinfection treatments date: 2020-05-20 journal: nan doi: 10.1101/2020.05.16.20102178 sha: doc_id: 305282 cord_uid: x2zzzw43 the possibility to extend the lifespan or even reuse one-off personal protective equipment, especially for n95 respirator and surgical mask become critical during pandemic. world health organization has confirmed that wearing surgical mask is effective in controlling the spread of respiratory diseases in the community, but the supply may not be able to satisfy all the demands created all over the world in a short period of time. this investigation found that dry heat and uvc irradiance could effectively disinfect the mask material without creating significant damage to surgical mask. uring pandemic, the huge demand of personal protective equipment (ppe) compels countries to investigate the possibility to reuse and extend the lifespan of every one-off ppe, especially for n95 respirator and surgical mask. world health organization (who) has confirmed that wearing surgical mask is effective in controlling the spread of certain respiratory viral diseases in the community [1] . however, the supply of surgical masks is still behind the huge demand created all over the world. in order to provide an alternative for the general public to maintain basic protection with limited resource, the possibility of reusing surgical mask after different disinfection methods was investigated. methods of disinfection studied include 100 ℃ dry heat, steaming, boiling, autoclave, 75% and 95% ethanol, uvc irradiance and household detergent. all the disinfection treatments used for disinfecting surgical mask were proven to be effective [2] , except household detergent. however, studies of disinfection efficiency, structural and property changes of surgical mask after various disinfection treatments were very limited. astm-f, en14683, kf and yy0469 are common standards for testing the quality of surgical masks. although the testing parameters are not completely the same among these standards, they all involve testing of filtration efficiency, breathability and fluid repellency. filtration efficiency typically considers the effectiveness of particles of aerodynamic size from 0.1µm to 3µm. the cut-off sizes used for the standard tests are classified as particulate filtration efficiency (pfe) and bacteria filtration efficiency (bfe) [3] . latex sphere is used for the pfe filtration test with the astm standard test [4] while the kf, yy0469 and niosh use sodium chloride aerosol to perform standard tests for respirator and surgical mask [5] [7] . since droplets will start evaporating when exposed to air, the terminal velocity decreases when the droplet size reduces [8] . this implies that small-sized droplets can travel a longer distance, resulting in a higher possibility of infection if the droplet nuclei is a pathogen. in assessing the destructive level of different disinfection treatments to surgical masks, filtration efficiency and fluid repellency were the parameters being focused in this study. structural changes of filtration layer were observed and verified after the treatments. the effectiveness of disinfection to surgical mask was thoroughly investigated. medicom astm level 1 surgical mask was chosen as the test subject due to its popularization. this surgical mask model is widely used in hospitals and health care sectors. the samples were labelled with numbers and randomly assigned to various treatment groups. each treatment group (n=3) was disinfected by one of the following methods: a. dry heat -an oven (breville bov820bss, 2400 w) was used for heating at 100 ℃ for 15 minutes. the temperature was monitored by the lcd display of the oven with reference to an infrared thermometer. b. steaming -samples were placed at the centre of a steamer cooker at 100 ℃ for 10 minutes. c. boiling -samples were placed at 100 ℃ water bath for 10 minutes. d. autoclave -samples were wrapped with aluminum foil individually and placed into the middle basket of an autoclave (hirayama, hve-50). the autoclave sterilization was set at 121 ℃ for 20 minutes (complete cycle time was 1.5 hour). e. detergent -0.5% w/v of household detergent (ultra axion) was prepared by dilution with di water. samples were submerged into the solution for 30 minutes, and then gently rinsed with di water for 1 min to wash away the remaining detergent. f. uvc irradiation -irradiation disinfection was performed by using a biosafety cabinet (nuairs, nu-425-400s) fitted with 254 nm (20w) tube for 10 minutes. power density at the d . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted may 20, 2020. . mask level was monitored with uvx radiometer with uvx-25 254nm uv probe. samples were placed at a distance of 60 cm from the tube for irradiation with measured average uvc intensity of 450µw/cm 2 . the samples were turned over at 5 minutes for even irradiation. g. samples were submerged into 95 % v/v ethanol for 5 minutes. h. samples were submerged into 75 % v/v ethanol for 5 minutes. all samples were air dried in a biosafety cabinet for 24 hours before all measurements. filtration efficiency test 2% sodium chloride solution (nacl) was aerosolized by particle generator model 8026 with a count median diameter at 0.04 micrometer (nominal) and a geometric standard deviation of 2.2 (nominal). dusttrak™ ii aerosol monitor model 8532 was used to measure the particle concentration before and after filter material. an impactor for 1µm was installed to the aerosol monitor to study the penetration of small droplets. each sample was fitted to the sample holder and fastened by screws and rubber o-rings. the penetration of sample was measured when instruments were operating after 2 minutes for stabilization. measurements were taken at the sampling holes perpendicular to the laminar flow at aerosol upstream and downstream of the sample. the measurement of the concentration of nacl droplet was taken at a face velocity of 14 cm/s. the filtration efficiency was calculated by the following equation: where is filtration efficiency (the background particle count was cancelled before calculation.) bactericidal test staphylococcus aureus (clinical isolate) was inoculated to nutrient broth no.2 (thermo scientific™ oxoid™ nutrient broth no.2 (dehydrated)) by an inoculating loop aseptically. the bacteria were then cultivated overnight in an environmental shaker at 37℃, 200 rpm. the overnight culture would be re-cultured for a few hours until it reached the concentration of 10 8 cfu/ml. bacteria culture prepared was diluted to 10 6 cfu/ml with 0.9% saline and 0.1% tween 80. mask was cut into 1 inch x 1 inch square and put on supporting glass plate of 1 inch x 1 inch square with external layer of the mask material facing upward. 50 µl of the diluted bacteria suspension was dropped onto each sample and the inoculum was spread evenly to allow soaking into the sample. three samples were picked randomly and treated with the aforementioned disinfection methods. a timer was used to monitor the exposure time of the samples with bacteria. afterwards, the samples with supporting glass plates were transferred to a sterile bottle containing 10 ml of extraction solution (0.9% saline, 0.1% tween 80). the bottle was vortexed for 20 seconds, allowing sufficient time for dislodgement of microbes into the solution. the suspension was serially diluted with sterilized 0.9% saline solution. 100 µl of the solution was inoculated into tsa agar and cultured at 37℃ for 24 hours. the colony forming units (cfus) on agar plates were enumerated. the bactericidal efficiency was calculated by the following equation: where is bactericidal efficiency hydrophobicity test five 100ul load of di water were added at a distance of 10 cm above the sample at 5 different spots on the outer layer of mask. visual inspection of droplets was carried out for each sample. after wobbling the mask gently, hydrophobicity was recorded if the water droplets hold as beads. hydrophilicity was recorded when water droplet shape was flattened (lowered contact angle) but did not penetrate all three layers. thorough damage of the water repelling layer was recorded when the water droplet was absorbed and penetrated to the bottom. the filtering layer (polypropylene) of each sample after treatments were cut into a size of 4 mm x 4 mm and fixed on copper stage with carbon tapes. the samples were observed with a scanning electron microscope (sem) (hitachi, tm3000) at magnification of 1000×. structural changes such as melting, deformation, entanglement or cracking of polypropylene fibre were recorded. comparison of the control and treatment groups were analyzed by t-test in spss (version 19). p values <0.05 were considered significant. sem was used to observe any micro structural change of masks after different treatments. sem images at 1000× revealed that all methods used in the experiment did not cause observable structural change to the filtering layer. no shrinkage, melting, deformation, entanglement or cracking of fibre was noted. all samples were tested for filtration efficiency with nacl droplets. control samples had an average filtration efficiency of 97.83 % ± 0.9 % at 14 cm/s. the average filtration efficiency of household detergent water treated and ethanol treated samples were significantly lower than the control. samples after boiling, steaming, baking & uvc irradiation were slightly offset from the control but were not significantly different. bead-like droplets were observed in all the samples treated with non-fluid disinfection methods, such as dry heat and uvc irradiation. for the samples underwent other disinfection treatments, the fluid-repelling layers were concluded to be damaged as the water droplets on the mask surface could not retain bead shape. uvc treated sample was scanned using ftir. result showed insignificant difference between control and treated samples. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted may 20, 2020. . due to the pandemic, limited supply and a sudden surge of need for surgical masks in many places have been reported. surgical mask decontamination methods have been reported from various media. the goal of the study was to evaluate some common surgical mask decontamination methods and to identify the possible methods that cause the least damage to the surgical mask in terms of overall integrity, hydrophobicity and filtration rate. as practical decontamination methods should aim at effectively eliminate harmful microorganisms with high reproducibility while remaining safe to users, certain decontamination methods such as chlorine gas and ozone gas treatment were not included in this experiment. certain drawbacks have been noted in some preliminary tests, for example, aqueous 1:99 bleach solution alone cannot penetrate into the mask to perform thorough disinfection. ozone gas is highly hazardous to human being [9] . it is not recommended to be used in area without proper ventilation. chlorine gas and other chlorinated compounds were known to be incompatible with polypropylene [10] . treatment with incompatible disinfectants may cause unwanted damages to the surface characteristics and structure of the mask. except household detergent water, all disinfection methods were effective in eliminating s.aureus in the mask material. traditional disinfection methods such as boiling, steaming, submersion in ethanol, dry heat, uvc irradiation have long been used to control microbial growth. s.aureus is a gram-positive bacteria commonly used to demonstrate efficiency of various disinfection methods. moist-heat treatment methods, including boiling, steaming, autoclave, expose the mask material to 100 % r.h. but not in the case of dry heat treatment. disinfection by dry heat has been known to be relatively slower than moist-heat, however, dry heat at 100 ℃ for 15 minutes was still efficient to achieve a 4-log reduction. ethanol treatment between 60% to 95% denatures protein and dehydrate microorganisms [2] . results from the experiment also showed an efficient 4-log reduction of s.aureus in 5 minutes. 254 nm uvc irradiation is a physical disinfection method that utilizes electromagnetic wavelength to damage rna, dna, and protein. the samples were turned over after 5 minutes because the irradiation may not be efficient to penetrate the entire mask material and eliminate "dead-corner". experimental result showed the exposure at 450 µw/cm 2 for a total of 10 minutes could effectively eliminate all s. aureus in the mask material. household detergent was not classified as a disinfectant. the detergent used in the experiment did not have bactericidal effect towards s. aureus. reduction demonstrated in table 1 could be a result of the partial suspension of bacteria into the solution. dry heat and uvc treatment did not show observable effect on the hydrophobicity of mask surface. for household detergent, rinsing with water might not completely remove detergent from mask material. all detergent treated masks demonstrated severe water penetration possibly be related to the lowered surface tension [11] . for treatment by boiling, steaming, autoclaved and ethanol, samples demonstrated flattened droplets. this could possibly be related to altered surface characteristic after treatments. most treatment groups did not demonstrate observable change of the general structure of surgical mask. all the ear loops held unchanged throughout the experiment, except for the samples treated by boiling, steaming and autoclave. treatment by boiling and steaming had generally softened the texture of the mask. uvc did not damage the filtration layer even the exposure time was up to 90 minutes. although uvc is proven to facilitate the degradation of polypropylene, short exposure targeted for disinfection of masks would not cause significant structural damage to the filtration layer [12] . after one treatment cycle, all treatment methods except uvc demonstrated a drop in filtration efficiency. treatment with household detergent and ethanol resulted in significant decrease of the filtration efficiency. after three treatment cycles, treatment by uvc and dry heat could still maintain high filtration efficiencies (> 95%). generally, non-fluid treatments perform better than fluid-based treatments in filtration efficiency test. the plausible reason is that the electric charges of polypropylene filtration layer were neutralized after the treatment, especially with the use of organic solvents [13] . this study had only evaluated a surgical mask in the filtration of 0.1 -1 µm nacl droplets. however, the performance of the surgical mask after treatment has not been tested with more brands, particles of various sizes and different flowrates. as the study result was based on a modified protocol of niosh nacl respirator certification test, it only provides comparisons among different groups of treatments. the study did not determine whether the treated samples could pass any international standards of surgical mask testing. future studies can focus on certain treatments, and investigate the optimal condition of decontamination treatment so as to minimize damage to the mask and to determine detailed disinfection conditions and kinetics that were required for other strains of microorganisms. decontamination and reuse of surgical mask become an alternative strategy to regenerate basic protective equipment so as to control the spread of disease under the current difficult situation. non-fluid contacting disinfection methods such as uvc irradiation and dry heat retained the highest performance regarding filtration efficiency, structural consistence and surface hydrophobicity even after three cycles of treatments. these two disinfection methods for surgical mask would be considered under the severe ppe shortage situation. advice on the use of masks in the context of covid-19 disinfection, sterilization, and preservation a comparison of facemask and respirator filtration test methods standard test method for determining the initial efficiency of materials used in medical face masks to penetration by particulates using latex spheres comparison of filtration efficiency and pressure drop in anti-yellow sandmasks, quarantine masks, medical masks, general masks, and handkerchiefs surgical mask yy 0469-2004 determination of particulate filter efficiency level for n95 series filters against solid particulates for non-powered, air-purifying respirators standard testing procedure (stp) how far droplets can move in indoor environments -revisiting the wells evaporationfalling curve review of evidence on health aspects of air pollution -revihaap project polypropylene chemical resistance guide proteomic profiling and analytical chemistry weatherability of polypropylene by accelerated weathering tests and outdoor exposure tests in japan experimental study on charge decay of electret filter due to organic solvent exposure key: cord-314216-xx5xbjqu authors: malik, talia title: covid-19 and the efficacy of different types of respiratory protective equipment used by health care providers in a health care setting date: 2020-04-10 journal: cureus doi: 10.7759/cureus.7621 sha: doc_id: 314216 cord_uid: xx5xbjqu coronavirus, the virus that caused the global pandemic at the beginning of 2020 and affected millions across the globe, presented as an enormous challenge to health care providers around the world. with increasing numbers of infected patients presenting daily, health care workers are struggling to take effective measures to protect themselves from transmission against the highly contagious coronavirus. this case helps us understand the implications of coronavirus-infected patients on the health care providers directly responsible for the management of these patients and the relative efficacy of different types of respiratory protective equipment mainly n95 masks and surgical masks in preventing the spread of infection among those at the front lines providing care. the coronavirus (covid-19) was declared a global pandemic by world health organization (who) on march 11, 2020 after it was known to originate from wuhan, china, and resulted in more than 381,000 confirmed cases around the world at the time [1, 2] . very little is known about its effect among those responsible for its management and treatment, primarily the doctors, nurses, and the first responders. the coronavirus causes an acute respiratory infection that is transmitted by contact and droplet routes. the use of personnel protective equipment (ppe), such as surgical gloves, face masks, eye protection, and regular hand washing, is known to limit the spread of the virus, but little is known about the relative efficacy of n95 masks over the regular surgical masks in preventing the transmission of the virus among health care workers (hcws). this aspect of identifying the superior type of respiratory protective equipment (rpe) is of significant importance in order to provide maximal protection to hcws, prevent medical equipment shortages, and to lessen the burden on manufacturers and suppliers of this equipment. both types of face masks are known to prevent the transmission of respiratory particles; however, the n95 masks are thought to have a superior efficacy by filtering out very small particles. in spite of having many benefits, the n95 masks have certain limitations and it is important to understand if the benefits outweigh the risks when compared to surgical masks. this case helps us better understand the efficacy and benefits of different types of rpe used by hcws during the management of patients infected with the coronavirus. a 55-year-old woman with a history of diabetes mellitus was admitted to the intensive care unit (icu) in early march 2020 for severe shortness of breath. she had recently returned from a trip to iran and was suspected to have been in contact with people infected with the coronavirus. on admission, she was given high-flow supplemental oxygen that slightly improved her shortness of breath; however, after a few hours, her respiratory status worsened and she was intubated and mechanically ventilated in the icu. the hcws who performed the aforementioned procedures used either the n95 mask or the surgical mask depending upon availability and personal preference. the patient's respiratory status gradually improved over a period of two days. in accordance with existing guidelines, the patient was extubated and shifted to the isolation ward for further management. three samples of nasopharyngeal swabs were obtained from the patient for three consecutive days for covid-19 testing and all came out positive for severe acute respiratory syndrome coronavirus 2 (sars-cov-2) on polymerase chain reaction (pcr) assay. all the 34 hcws exposed to the patient were isolated and quarantined for a period of 14 days. information was obtained about the type of rpe used by each hcw during exposure to the patient. half of the hcws used surgical masks, whereas the rest used n95 masks as the rpe while performing procedures on the infected patient. during this period of quarantine, routine surveillance monitoring for cough, shortness of breath, and muscle aches was made. two samples of nasopharyngeal swabs were obtained from the hcws on the day of exposure and the last day of quarantine for covid 19 testing via the pcr assay. each hcw remained asymptomatic and tested negative for covid 19 on both tests. the coronavirus is known to spread through aerosolized particles. hcws are at an increased risk of being infected without proper ppe and protective measures. this case highlighted the importance of evaluating the efficacy of different rpe during a viral pandemic in protecting the hcws from the transmission of infection. none of the hcws who were exposed to the virus tested positive for covid-19 despite using the different types of rpe. this helps us in determining the relative efficacy of surgical masks and n95 masks over one another in preventing the transmission of the virus among hcws. it can also be deduced that both types of rpe offer equal protection to hcws from the virus; however, these findings need to be validated by well-designed large-scale studies. the observation made in this case report was also highlighted by a previous study which showed that n95 masks were not superior to surgical masks for preventing influenza infection among hcws [3] . another study concluded that there was no significant difference between n95 mask and surgical masks in preventing the risk of transmission of respiratory infections from infected patients [4] . although the above studies showed no significant difference in efficacy of both types of rpe, it is vital to understand that different infectious agents have different mechanisms of transmission and action, and hence large-scale randomized controlled trials (rcts) need to be conducted to better understand the particular pattern and characteristics of sars-cov2 that differentiate it from other respiratory infectious agents with similar features. the n95 mask is thought to be superior to the surgical masks. these masks are known to filter out 95% of small airborne particles including bacteria and viruses. they have been tested and approved by the national institute of occupational safety (nios); however, there are certain limitations to its use. since breathing while wearing the n95 mask is harder, it is not recommended for the elderly, claustrophobics, and individuals suffering from lung diseases as it may exacerbate their pre-existing conditions. these masks need to be properly fitted on the face every time to ensure that a proper seal is in place to provide maximal protection. the inability to form a proper seal does not provide adequate protection. this can be difficult to achieve in individuals with facial hair and in children. it can also inadvertently lead to frequent contact between the hands and the face while adjusting the mask, which further increases the risk of transmission. the tight seal also leads to the build-up of heat and humidity within the mask causing discomfort and difficulty in breathing. the duration and cost of manufacturing are longer and higher and during a pandemic, shortages of this equipment can result in avoidable exposure to hcws. during a pandemic or health crisis, hcws need to be able to access ppe readily in order to protect themselves, patients, and their contacts. interpretation of this case and the above studies helps us understand the need to urgently conduct large-scale rcts and incorporate the findings of these trials and studies to revise the existing guidelines regarding the use of rpe by hcws and possibly increase the usage of readily available surgical masks in favor of n95 masks for preventing covid-19 transmission. till the availability of any conclusive evidence, health care providers in direct contact with covid-19 cases should continue the use of n95 respirators as advocated by the current guidelines. although this case report helps us in determining the relative efficacy of different rpe in preventing covid-19 transmission, there is still a lot more that needs to be studied about the transmission and pathology of the coronavirus to introduce effective measures and equipment that will protect hcws in the future. the intricate details about the size and transmission of the virus still need to be studied in depth to figure out the best method of rpe that can be used to prevent its transmission. although this case report signifies that there is no superior protection offered by n95 masks in comparison to surgical masks, it has certain limitations and additional studies, particularly rcts need to be conducted in a health care setting to determine the effectiveness of different rpe, which may lead to the revision of existing policies and guidelines regarding the best ways to protect hcws from being infected with the coronavirus in the event of an exposure. human subjects: all authors have confirmed that this study did not involve human participants or tissue. conflicts of interest: in compliance with the icmje uniform disclosure form, all authors declare the following: payment/services info: all authors have declared that no financial support was received from any organization for the submitted work. financial relationships: all authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. other relationships: all authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work. clinical features of patients infected with 2019 novel coronavirus in wuhan, china journey of a thai taxi driver and novel coronavirus respect investigators: n95 respirators vs medical masks for preventing influenza among health care personnel: a randomized clinical trial effectiveness of n95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis key: cord-292587-hp4zd8lr authors: rubino, ilaria; choi, hyo-jick title: respiratory protection against pandemic and epidemic diseases date: 2017-10-31 journal: trends in biotechnology doi: 10.1016/j.tibtech.2017.06.005 sha: doc_id: 292587 cord_uid: hp4zd8lr respiratory protection against airborne pathogens is crucial for pandemic/epidemic preparedness in the context of personal protection, healthcare systems, and governance. we expect that the development of technologies that overcome the existing challenges in current respiratory protective devices will lead to a timely and effective response to the next outbreak. ilaria rubino 1 and hyo-jick choi 1, * respiratory protection against airborne pathogens is crucial for pandemic/epidemic preparedness in the context of personal protection, healthcare systems, and governance. we expect that the development of technologies that overcome the existing challenges in current respiratory protective devices will lead to a timely and effective response to the next outbreak. influenza, a major respiratory disease, poses great risks to global health. influenza epidemics and pandemics are responsible for 250 000-500 000 deaths each year (www.who.int/mediacentre/ factsheets/fs211/en/) and >50 million fatalities worldwide in the past century (www.cdc.gov/flu/pandemic-resources/ basics/past-pandemics.html), respectively. the next influenza pandemic is estimated to cause $60 million deaths [1] . ideally, vaccination within 2 months of the outbreak can provide effective protection [2] . however, because several months are necessary for vaccine development and administration, the infection risk is heightened during the non-vaccine period. this is further supported by the outcomes of 2002-2003 severe acute respiratory syndrome (sars) outbreak that originated in china, in which the disease was transmitted globally within few weeks, but the first vaccine phase i clinical study began a year after the outbreak [3] . logistically, an effective pandemic preparedness plan should include both vaccination and alternative mitigation methods (pharmaceuticalantiviral; non-pharmaceuticalisolation, administrative control, personal protective measures). therefore, respiratory protection devices are a key non-pharmaceutical intervention that is essential to the global strategy for pandemic readiness. the parameters behind respiratory protection and airborne transmission intertwine in a complex system that can be broken down into four bidirectional components: (i) release, (ii) infection, (iii) filtration, and (iv) protection (figure 1 ). once a subject is infected, nanometer-to-millimeter-sized pathogenic particles can be released while breathing, speaking, sneezing, or coughing, and infect a host respiratory tract via different mechanisms that depend on the aerodynamic size of the particles (d a <5 mm, lower respiratory tract; 5 < d a < 100 mm, upper respiratory tract). similarly to infection, current respiratory protection devices filter infectious particles in a size-dependent manner. filtration efficiency, comfort (e.g., breathability), and fit at the face-mask interface govern technical performance. while effective management and availability of control measures are crucial to an outbreak response, the pathogens [ 1 1 4 _ t d $ d i f f ] (virus/bacteria/ fungi) captured on filters are an intrinsic concern because of fear of cross-infection, new aerosol release, and contaminated waste. recurrent recommendations regarding respiratory protective measures by the centers for disease control and prevention (cdc) and the world health organization (who) emphasize their prominent role in emergency preparedness. nonetheless, fewer scientific efforts have been focused on respiratory protection technologies compared to vaccine development technologies. we present here an overview of currently available respiratory intervention technologies and their implications for future research directions in response to pandemic/epidemic outbreaks. surgical masks have been in use for over 100 years as barriers against the development of infection via large droplets produced during surgery. n95 filtering facepiece respirators (n95 respirators) were introduced in 1995 as part of the national institute for occupational safety and health (niosh) 42 code of federal regulations (cfr) part 84 on non-powered air-purifying respirators (www.cdc. gov/niosh/npptl/topics/respirators/ pt84abs2.html). currently, surgical masks and n95 respirators are the two main intervention measures for personal respiratory protection. nonetheless, technical challenges exist, some of which are shared by both devices: (i) filtration efficiency, (ii) cross[ 1 0 9 _ t d $ d i f f ] -infection, (iii) recyclability, and (iv) faceseal. a primary issue concerning the efficacy of surgical masks against airborne pathogens is low filtration efficiency. although performance can vary drastically among models, inconsistent reports on surgical mask efficacy are probably associated with improper application, resulting in performance mismatch. another crucial issue is cross[ 1 0 9 _ t d $ d i f f ] -infection/transmission. because viruses and microorganisms can survive for at least a few hours to several days [4] , masks and respirators become a source of infection for the wearer and others, thus limiting them to single use. infectious aerosols on filters can also be re-released into the environment (i.e., reaerosolization), for example through accidents. with a particle diameter of 1.15 mm, re-aerosolization from n95 respirators as a result of a fall (drop height, 0.76 m) was between 0.002% and 0.012% [5] . various sterilization methods (e.g., ethylene oxide, formalin, uv, bleach, hydrogen peroxide) have been tested to recycle respirators. however, the drawbacks of each method, such as performance deterioration and generation of toxic residues, have restricted their application. as an example, decontamination of n95 respirators by autoclave, 160 c dry heat, 70% isopropanol, and soap and water lowered the filtration efficiency [6] . ethylene oxide treatment of respirators caused deposition of hazardous residues of 2-hydroxyethyl acetate on the straps, and bleach, oxidants, or dimethyldioxirane raised issues of sharp odor and incompatibility with staples/nosepiece [7] . despite the need for further research, with safety as a preponderant concern, mask recyclability would be beneficial because it would reduce the amount of biohazardous waste and derived risks. in addition, reusability would naturally address a shortage of respirators during pandemics. furthermore, aerosols penetrate through loose-fitting masks/respirators, based on wearer facial features, movement, proper and timely fit testing/check, aerosol size, and mask shape. particles <10 mm enter through faceleaks 5-6-fold and up to 10fold more than through the filter of surgical masks and n95 respirators, respectively [8] . thus, although improving filtration efficiency is necessary, better fitting should be a primary objective to fully address aerosol penetration. interestingly, the general public tends to disregard infection control guidelines. as such, although respirators are recommended when airborne transmission is possible, surgical masks have experienced greater acceptance because of advantages such as comfort, availability, and cost. however, inappropriate application of devices may not provide consistent protection. this in turn stimulates research and development of new technologies to close the gap between guideline and practice. safer and more effective respiratory protection for a timely emergency response? diverse methods have been investigated to improve the performance of respiratory protection devices (box 1), such as higher subject releases pathogenic aerosols by breathing, talking, sneezing, and coughing. depending on the size, the particles deposit in different levels of the respiratory tract à upper respiratory tract (green), tracheobronchial region (blue), and alveolar region (red) à as a result of different mechanisms (i.e., interception, impaction, sedimentation, and diffusion). based on the same mechanisms, with additional electrostatic interactions of charged fibers, masks offer respiratory protection by filtration. the degree of respiratory protection is affected by the technical performance of the mask (filtration efficiency, comfort, faceseal, proper donning/doffing, and pathogen infectivity), as well as the infrastructure (available supplies, policies, and cost). in addition, because virus/bacteria infectivity is maintained on the fibers, the filter becomes a source of cross-infection, re-aerosolization, and environmental contamination. neutralization of the pathogens on respiratory protective devices is an approach that can bridge this gap towards pandemic and epidemic preparedness. filtration efficiency without sacrificing breathability. representative examples include fabrication using nanofibers and incorporation of electric charge by plasma treatment and charge-carrying agents. however, major technical challenges remain to be addressed for effective preparedness from the standpoint of contamination and infrastructure. hence, production of a filter that inactivates the collected pathogens would bring key improvements to current surgical masks and respirators, resulting in increased protection, reduced risk of cross[ 1 0 9 _ t d $ d i f f ] -infection, and recyclability without decontamination ( figure 1 ). to inactivate viruses, antimicrobial treatments have been investigated for filters utilizing halogens, metals, quaternary ammonium compounds, antibody-antigen reaction, and salt recrystallization. chlorine compounds such as n-halamines and iodine-treated filters have been assessed against bacteria (micrococcus luteus and escherichia coli) [9] . in addition, surgical masks functionalized with silver nitrate nanoparticles or quaternary ammonium inactivated bacteria (escherichia coli and staphylococcus aureus, and acinetobacter baumannii, enterococcus faecalis, and staphylococcus aureus, respectively) by interaction with thiol groups (100% reduction in $48 h) and membrane permeability damage ($92% reduction in 1 h), respectively [10, 11] . however, antimicrobial technologies based on silver/copper, reactive oxygen molecules, iodine, and titanium dioxide did not exhibit inactivation properties against ms2 virus [12] . another approach to inhibit virus transmission involves modification of the filter surface with the antigen-specific antibodies [13] . despite the merits of each approach, effective protection against virus aerosols is still limited by slow action (rapid inactivation should occur in the order of minutes, not hours) or binding specificity. recently, salt recrystallization was found to physically destroy viruses on surgical mask filters within few minutes in a strainindependent manner, potentially enabling reuse without separate processing steps [14] . notably, most studies have focused on the functionalization of the outermost and middle layers of the mask. the final design of the protection device layers should consider the spatial deposition of aerosols within masks and their contact surface. based on the above observations, we identify three central parameters in developing pathogen-inactivating filters. first, an inactivation mechanism should act rapidly to avoid cross[ 1 0 9 _ t d $ d i f f ] [ 1 0 8 _ t d $ d i f f ] -infection. although additional aspects are involved (e.g., fraction of transferred pathogens, surface area), unsafe handling and people's tendency to touch their face every $4 minutes lead to a risk of contact transmission from a pathogen-laden mask/respirator [15] . second, pathogens should be neutralized in a strainnonspecific way. the pathogen/strain responsible for the next pandemic cannot be exactly predicted because of continuous mutation. as such, antibodyfunctionalized protective devices that target a strain-specific virus would delay the emergency response. thus, the pathogen-killing mechanism should guarantee broad-spectrum protection. third, the ideal technology should be the key technical components of the performance of current respiratory protection devices are filtration efficiency, fit, and comfort. each has a significant role in protective efficacy, and specific parameters can be tuned to improve them. fit: non-filtered air entering through a poor seal between mask and face is a prominent concern. efforts towards reducing faceleaks can be grouped as follows. (i) material selection that allows customizable mask shape/tightness. (ii) investigation of wearers' facial features, and simulation of the spatial distribution of leaks to guide mask design. (iii) fit testing/training optimization to increase efficacy/compliance. filtration efficiency: whereas n95 respirators have a certified filtration efficiency of 95%, surgical masks have low performance. several major parameters can be controlled to decrease particle penetration, (i) decreasing the diameter of fibers. (ii) decreasing the size of filter pores, (iii) controlling fiber electrical charge through manufacturing process/material selection. (iv) increasing the thickness of the filters. user comfort: the wearer's perception of comfort is crucial to correct practices and effective protection. tolerability during mask use is often limited by the following factors. (iv) discomfort from prolonged contact between skin and rough materials. (iv) difficulty in communicating. device-independent. in the case of a pandemic outbreak, time-consuming production and cost would be major limitations to respirator use. although a certified respirator is recommended, considering the heavy use of surgical masks and scarcity of respirators, the technology should be easily extendable to masks and other existing infection control measures. therefore, the aforementioned factors outline the considerations that can enhance respiratory protection for a timely emergency response. the unpredictable nature of airborne pandemic diseases and their impact on our economy and society present a big challenge at the national and global level. only a prompt and coordinated response among different sectors of society can maintain security from this threat, which can be implemented through the help of technological innovations and comprehensive planning. unfortunately, despite being recognized as a key technical element in pandemic/epidemic preparedness, innovation in the design of respiratory protection devices has been sparse. in alignment with the strategic plan for pandemic/epidemic preparedness, we anticipate that incorporation of efficient pathogen-neutralization mechanisms can overcome the existing technical (contact transmission, source control, waste) and non-technical (supply shortage, policies, cost) challenges in respiratory protection. thus, we expect this engaging field to expand further, with the promise to offer enhanced protection to the global population. bacterial biohybrids use the energy of bacteria to manipulate synthetic materials with the goal of solving biomedical problems at the micro-and nanoscale. we explore current in vitro studies of bacterial biohybrids, the first attempts at in vivo biohybrid research, and problems to be addressed for the future. the aim of biohybrids is to harness cell motility and energy for user-desired tasks, including the transport of artificial cargo, drug delivery, or to power a tool for micromanipulation of other objects [1, 2] . bacteria-powered biohybrids (box 1) present new micromachines to perform complex tasks at the micro-and nanoscale. in vitro, biohybrids have demonstrated the ability to selectively sort particles [3] and even build microarchitectures [4] , but real-world applications for bacterial biohybrids have yet to be achieved. however, the biomedical field offers many opportunities to utilize the micromaneuverability and natural sensing capabilities of biohybrids for non-invasive medical applications that are not possible with current technologies, and recent research has been pushing biohybrids towards this goal. current bacterial biohybrids have the potential to be used for cancer or disease detection, targeted drug release, and even disruption of infectious biofilm sites. however, many challenges with external guidance, cargo loading and unloading, and efficient swimming remain, hindering their use in clinical and therapeutic applications. we present here recent attempts and developments to improve bacterial biohybrid performance and move the field closer to in vivo medical applications. bacteria attached to micro-or nanoparticles are some of the best-studied bacterial biohybrid systems. bacteria adhere to the particle and carry it while swimming, creating an effective cargo delivery system. guided cell adhesion of the bacterial body to localized regions of the estimation of potential global pandemic influenza mortality on the basis of vital registry data from the 1918-20 pandemic: a quantitative analysis strategies for mitigating an influenza pandemic severe acute respiratory syndrome persistence of the 2009 pandemic influenza a (h1n1) virus on n95 respirators particle release from respirators. part i: determination of the effect of particle size, drop height, and load effect of decontamination on the filtration efficiency of two filtering facepiece respirator models analysis of residual chemicals on filtering facepiece respirators after decontamination performance of an n95 filtering facepiece particulate respirator and a surgical mask during human breathing: two pathways for particle penetration evaluation of physical capture efficiency and disinfection capability of an iodinated biocidal filter medium antimicrobial effect of surgical masks coated with nanoparticles application of a quaternary ammonium agent on surgical face masks before use for pre-decontamination of nosocomial infection-related bioaerosols evaluation of the survivability of ms2 viral aerosols deposited on filtering face piece respirator samples incorporating antimicrobial technologies protection from avian influenza h5n1 virus infection with antibody-impregnated filters universal and reusable virus deactivation system for respiratory protection a study quantifying the hand-to-face contact rate and its potential application to predicting respiratory tract infection this research was financially supported by startup funds from university of alberta (h-j.c.). key: cord-321847-4a6eb4mr authors: eckl, l.; hansch, s. title: genderand age-related differences in misuse of face masks in covid-19 prevention in central european cities date: 2020-11-13 journal: nan doi: 10.1101/2020.11.11.20224030 sha: doc_id: 321847 cord_uid: 4a6eb4mr 1 abstract objective correct use of face masks is required for their efficacy in preventing possible droplet infections with sars-cov-2. we tried to provide information about differences in the distribution of gender and age groups wearing face masks incorrectly. design pilot field study methods visual observation of mask use in public, not ageand gender-related places in central european large cities regarding incorrect mask-wearing (n=523); statistical analysis (nominal scale) in terms of gender and estimated age group using the total numbers, binomial test and chi-square test. results there is no significant difference (binomial test: p-value = 0.43) in mask misuse between the genders (female: 271 (51.8%), male: 252 (48.2%) and 0 non-binary individuals (0%)). there is a significant difference (chi-square test: p-value < 2.2e-16) in age group distribution (170 young 10-29 years (32.5%), 261 middle-aged 30-59 years (49.9%), 92 older adults [≥]60 years (17.6%)). in total numbers, the highest counts were observed in middle-aged persons with 261 counts (49.9%). conclusion our study shows an uneven age-distribution of people wearing the face mask in public improperly. keywords coronavirus, sars-cov-2, covid-19, community, face mask, prevention in the spread of the global pandemic of corona virus disease 2019 (covid-19) caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2), the necessity of protective countermeasures emerges. dependent upon geographical area, professional or community setting, the use of face masks is controversially discussed or often mandatory. a recent overview by feng et al. [1] shows how different healthcare authorities handle the current evidence by providing different recommendations on the use of face masks. despite initial discouragement or at least insufficient evidence of risk reduction to get infected, the wearing of face masks in defined situations was recommended by the german federal ministry of health [2] . public guidelines for the use of face masks were provided by the german federal institute for drugs and medical devices [3] , inter alia regarding the placement of a closely fitting mask covering mouth and nose. besides other measures like distance and hand hygiene, the optimal use of face masks is needed to provide a sufficient efficacy of the physical barrier's aspired protective effect [4] . a recent study by leung et al. [5] on expiratory virus shedding found higher virus loads in nasal swabs than in throat swabs, so an incorrectly worn mask without covering the nose could drastically facilitate disease spread. . cc-by-nc-nd 4.0 international license it is made available under a perpetuity. is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 13, 2020. ; https://doi.org/10.1101/2020.11.11.20224030 doi: medrxiv preprint the prevalence of masking after the post-lockdown reopening of businesses has currently been examined in other studies [6, 7] , and significant differences in regional, age and gender groups have been found. we address the question: who are the people in public that are not wearing the face mask properly and therefore risk to spread sars-cov-2? this could contribute to improve health behavior education campaigns and / or advertisements, under the assumption, although not proven by this study, that people, who are wearing a mask, and therefore already show compliance with the latest regulations, are generally approachable for the correct use of a mask and prevention measurements. three factors influenced the observations: i) the general age-and gender-distribution in public, ii) the probability that a certain age-and gender-group does not properly use the mask and iii) the distribution seen by the observers. for efficiency reasons with focus on the spreading of sars-cov-2 in public space, we combined the numbers of the general age-and gender-distribution in public (i) and the probability, a certain ageand gender-group does not properly use the mask (ii) as there is lack of consequences in the first line, if surveyed separately. combining these two factors leads to a distribution of people improperly using the face masks in the public, which itself could risk a higher spread of the infections. factor iii was tried to be minimized, as to be seen in the methods part of this manuscript. we therefore measured the total counts of different age-and gender-groups in public (i and ii combined), that are using the mask incorrectly. between june 2020 and september 2020, we performed observations at different times and weekdays in three german (regensburg, augsburg and berlin), one austrian (vienna), and one polish city (szczecin). these observations were conducted by a team of one female and one male researcher and took place in public places and transportation (buses, streetcars, subways, trains, stations, shopping malls, bakeries and supermarkets). each of these places had an official recommendation to wear a face mask. we excluded gender-and age-specific locations, like woman clothing-shops, schools or retirement homes. the male and the female researcher both were medically experienced in signs of pre-aging and physical signs of age. both researchers had to see the person, otherwise the person was excluded. furthermore, both had to confirm the age-group and gender. without confirmation of both scientists, physical signs, like specific clothing, physical signs or family-status were used to determine an age group. as an incorrect fit of face mask, we defined any deviant kinds of mask use, i.e., covering only the mouth or the nose but not both or neither of them, a very loose fit with forming gaps between the mask and the face and taking the mask off for coughing or sneezing. as correct use of the face mask served the who recommendation, as to be seen in the "advice on the use of masks in the context of covid-19" [8] . we considered all people in the mentioned public places as eligible, with the exclusion criteria of (1) children under the estimated age of 10 years and (2) individuals with visible physical disabilities like people in wheelchairs, with walking aid or oxygen device. age groups were divided into young (10-29 years), middle-(30-59 years), and advanced age (≥60 years), independently estimated by the two researchers. gender groups included phenotypically female, male, and non-binary gender. observations were taken from a distance without interaction between researchers and subjects. notes were taken digitally by a tally list in the above-mentioned categories. we conducted statistical analysis (nominal scale) in terms of gender and age, total numbers, binomial test, and chi-square test using the r-functions chisq.test() and binom.test(). is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 13, 2020. ; https://doi.org/10.1101/2020.11.11.20224030 doi: medrxiv preprint we tried to further minimize the above-mentioned distribution seen by the observers (iii) by different approaches. one of these approaches concerns the time of the day. we performed separate measurements, either between morning and noon (9 am -2 pm, three measurements) or in the afternoon (4 pm -8 pm, three measurements), for an average duration of 1.5 hours for each observation. another approach was made by watching different cities. both are analyzed as part of the whole statistical analyses and separately. there was no acquiring of personal data, so no conclusions on individuals can be drawn. therefore, the university of regensburg ethics committee saw a board review of our study as not obligatory. we observed 523 samples of incorrect mask use, shown in table 1 and figure 1 . the first question was if there is a difference in misuse of the face mask between the genders. as we observed no cases in the non-binary gender group, only male and female genders are mentioned in the following. our hypothesis was, that there is no difference between man and woman in misuse. therefore, we compared the total numbers of each gender (271 (female) vs. 252 (male)) using the binomial test and received a p-value = 0.4313. this p-value is above our significance level of p<0.05. furthermore, we applied the chi-square test on our data, which showed x-squared = 0.99008, df = 2, p-value = 0.6095, which also indicates no difference. another question was if there is a difference between the age-groups (young with 170, middle-aged with 261 and older adults with 92 persons). we also applied a chi-square test and received x-squared = 82.076, df = 2, p-value < 2.2e-16. this p-value is below p<0.05 and shows, that misuse of face masks is significantly age-related. in total numbers, the highest counts were observed in middle-aged persons with 261 counts (49.9%). further analyses, which are especially addressing different cities and different daytimes are shown in table 2 and table 3 . all these analyses are statistically significant. is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 13, 2020. ; https://doi.org/10.1101/2020.11.11.20224030 doi: medrxiv preprint figure 1 total numbers of observed subjects is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 13, 2020. ; https://doi.org/10.1101/2020.11.11.20224030 doi: medrxiv preprint our study aims to determine if there is a relevant difference in the misuse of face masks between subgroups in terms of gender and age. this study is the first one to assess the misuse of face masks during the current global pandemic. this topic is especially of interest, to evaluate the application of protective countermeasures in public, and it can contribute to further modelling and prognosis of pandemic spread. another strength is the relative high case number, which allows a representative statement about our study question, and makes it comparable to other works. we performed our observations in cities in the south (regensburg, augsburg) and the northeast of germany (berlin), in a large polish city (szczecin), and the capital city of austria (vienna) to improve the study design by decreasing regional effects. here must be said that the highest number of observations was taken in regensburg, but a cross-analysis (see tables 2 and 3) between regensburg and the other cities shows a significantly uneven distribution of age groups with p-values below our level of significance of <0.05. also, some limitations must be noted. one is the time window of our observations in terms of the whole timespan. there may be an effect of in-or decrease of mask misuse over time in the assessed places, influenced by the current climate of public opinion or the continuously updated state of knowledge. another limitation lies within the location of our observations. these were taken mainly in centrally located malls, shops, supermarkets and stations of large cities as described in methods. rural areas, senior homes, universities, and suburban regions are not included in our study. further and more widespread investigation can contribute to exploring the topic of mask misuse in these areas. our pilot-study shows a significant, gender-independent difference between age groups in the correct use of face masks in public. this serves as a reference point for our further investigation concerning subgroup-analyses and prevalence studies, which are already in preparation. the results may be useful in health education and advertising, like promoting to avoid public places or the correct mask use, addressing especially subgroups with highest misuse rates. . cc-by-nc-nd 4.0 international license it is made available under a perpetuity. is the author/funder, who has granted medrxiv a license to display the preprint in (which was not certified by peer review) preprint the copyright holder for this this version posted november 13, 2020. ; https://doi.org/10.1101/2020.11.11.20224030 doi: medrxiv preprint rational use of face masks in the covid-19 pandemic coronavirus sars-cov-2: chronik der bisherigen maßnahmen 2020 hinweise des bfarm zur verwendung von mund-nasen-bedeckungen (z.b. selbst hergestellten masken physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and metaanalysis respiratory virus shedding in exhaled breath and efficacy of face masks who is wearing a mask? gender-, age-, and locationrelated differences during the covid-19 pandemic 2020 prevalence of mask wearing in northern vermont in response to sars-cov-2 2020 advice on the use of masks in the context of covid-19: interim guidance all authors of this article certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. we thank florian schlieckau, simon stelzl, karl-peter ittner, gerhard hansch, and fro wirtz for helpful discussions key: cord-255062-7ozdmb09 authors: ogoina, dimie title: improving appropriate use of medical masks for covid-19 prevention: the role of face mask containers date: 2020-08-04 journal: am j trop med hyg doi: 10.4269/ajtmh.20-0886 sha: doc_id: 255062 cord_uid: 7ozdmb09 use of medical masks is a key strategy for covid-19 prevention among healthcare workers. unfortunately, there are global shortages of this essential commodity, and many have resulted in inappropriate usage to conserve supply. this article highlights the likely benefits of face mask containers in promoting safe, appropriate, and extended use of medical masks by healthcare workers in settings where a sustainable supply of medical masks may be limited. public wearing of face masks is now one of the key strategies for containing the current covid-19 pandemic across the globe. 1, 2 the who has also recommended targeted continuous use of medical masks by healthcare workers working in clinical areas in health facilities in geographical areas with community transmission of covid-19. 2 according to the who, face masks are used appropriately when they always cover the mouth and nose, when the front and inside of the face mask is not touched, and when hand hygiene is performed before wearing, and after touching and removal of the face mask. 2 during targeted continuous mask use, healthcare workers are required to wear medical masks throughout their entire shift and advised to replace their medical masks when wet, damp, visibly soiled, damaged, and if the health worker/ caregiver removes the mask (e.g., for eating or drinking or caring for a patient who requires droplet/contact precautions for other reasons). 2 face mask use has been shown to be associated with a large reduction in the risk of covid-19 infection. 3 unfortunately, it is not comfortable to wear face masks for prolonged periods. 2, 4 as an infectious disease physician working in a covid-19 isolation facility in nigeria, i have observed that most healthcare workers do not have adequate supplies of medical masks to replace them each time there is need to temporarily remove their masks to undertake activities such as eating or drinking or when alone in their offices or cars. many have therefore opted to wear masks on their chin and neck or keep potentially contaminated face masks on desks, or inside pockets, or bags in close contact with other personal belongings. 5 in most cases, the masks are handled carelessly and squeezed repeatedly during removal and reuse. the consequence of this inappropriate use of face masks is selfand environmental contamination and increased risk of transmission of covid-19. although there is a growing literature on strategies to decontaminate and reuse single-use medical masks, 4,6 the who currently does not recommend reuse of single-use medical masks. however, if medical masks are to be worn continuously by healthcare workers for up to 8 hours or more every working day, then there should be provision to temporarily and safely store them for extended use during the day, especially when they are not visibly soiled, wet, damp, or damaged. the use of face mask containers could help to promote appropriate and safe storage of face masks and facilitate extended use when medical masks are not due for replacement. we designed a plastic box and a leather pouch as face mask containers (figure 1 ) to store masks temporarily when not in use. within the containers, the masks are secured by their straps and held flat in their natural positions without the risk of squeezing and self-and environmental contamination. this way they can easily be picked up by the straps and worn safely without touching the front or inside of the mask. we also created vents on both sides of the face mask containers to improve ventilation in the containers when closed. in the wake of global supply shortages, 7 appropriately designed face mask containers could be useful in promoting safe extended use of medical masks, especially in resourcelimited healthcare settings. face mask containers could conserve limited supplies of medical masks for sustainable use by frontline healthcare professionals. compared with the chin, neck, pocket, or desk, a face mask container is probably a safer environment to store a medical mask when there is need to remove it temporarily to perform activities such as eating or drinking, or when there is need to temporarily expose the mouth and nose to relieve the discomfort associated with the prolonged use of face masks. face mask containers should however not be used to store medical masks that are due for replacement, especially when they are wet, damp, visibly soiled, or damaged. unfortunately, an unintended risk of these containers is the likelihood of prolonged storage and repeated reuse of masks that should have been discarded or washed before reuse. with the growing call for universal masking as a key costeffective strategy to combat the covid-19 pandemic, it is my view that the benefits of face mask containers in promoting appropriate use of masks and enabling extended and safe use far outweigh the risks. further studies on the benefits and risks of face mask containers would be useful to confirm these assertions. universal masking to prevent sars-cov-2 transmission-the time is now advice on the use of masks in the community, during home care and in healthcare settings in the context of the novel coronavirus (covid-19) outbreak covid-19 systematic urgent review group effort (surge) study authors, 2020. physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis face masks for the public during the covid-19 crisis covid-19: the need for rational use of face masks in nigeria decontamination of surgical face masks and n95 respirators by dry heat pasteurization for one hour at 70°c shortage of personal protective equipment endangering health workers worldwide leather pouch (a) and plastic box (b) designed as face mask containers to safely store face masks to avoid self-and environmental contamination and promote extended use of face masks in the face of scarcity acknowledgments: i acknowledge the support of opaminola okrinya, key: cord-308857-otsrexqu authors: goel, saurav; hawi, sara; goel, gaurav; thakur, vijay kumar; pearce, oliver; hoskins, clare; hussain, tanvir; agrawal, anupam; upadhyaya, hari m.; cross, graham; barber, asa h. title: resilient and agile engineering solutions to address societal challenges such as coronavirus pandemic date: 2020-05-28 journal: mater today chem doi: 10.1016/j.mtchem.2020.100300 sha: doc_id: 308857 cord_uid: otsrexqu the world is witnessing tumultuous times as major economic powers including the us, uk, russia, india, and most of europe continue to be in a state of lockdown. the worst-hit sectors due to this lockdown are sales, production (manufacturing), transport (aerospace and automotive) and tourism. lockdowns became necessary as a preventive measure to avoid the spread of the contagious and infectious “coronavirus disease 2019” (covid-19). this newly identified disease is caused by a new strain of the virus being referred to as severe acute respiratory syndrome coronavirus 2 (sars cov-2; formerly called 2019-ncov). we review the current medical and manufacturing response to covid-19, including advances in instrumentation, sensing, use of lasers, fumigation chambers and development of novel tools such as lab-on-the-chip using combinatorial additive and subtractive manufacturing techniques and use of molecular modelling and molecular docking in drug and vaccine discovery. we also offer perspectives on future considerations on climate change, outsourced versus indigenous manufacturing, automation, and antimicrobial resistance. overall, this paper attempts to identify key areas where manufacturing can be employed to address societal challenges such as covid-19. coronaviruses (covs) belong to the family coronaviridae which includes four genera: α, β, γ and δ as well as several subgenera and species [1] . sars cov-2 is a β-coronavirus with a single-stranded rna genome of ~30 kb [2] . recent topical research has revealed several new covs (three α-coronaviruses, three new βcoronaviruses, and one previously described α-coronavirus) from bats captured from myanmar and future emergence of new diseases caused by these covs due to change of land use has been speculated [3] . furthermore, newer mutations of the virus that originally spread from wuhan were confirmed as deadlier in some countries compared to others, which has led to added confusion and concern [4] . sars cov-2 was first identified from the outbreak of respiratory illness cases in wuhan city in the hubei province of china. initial reports of the virus were made to the world health organisation (who) on december 31, 2019. this was followed by the who declaring covid-19 as a global health emergency on january 30, 2020 due to rapid spreading, and a later pandemic declaration on march 11, 2020. the disease has quickly engulfed most of the world and has caused severe infection to populations across numerous countries as shown in figure 1 . covid-19 is shorthand for "coronavirus disease 2019" which is caused by the sars cov-2 virus, also called coronavirus in typical usage. viruses cause disease by binding to receptors on cells in the human body and then replicating at a rapid rate which triggers a variety of pathogenic processes. in the case of covid-19, the structures on the surface of the virus bind to receptors in the airway or the lungs of human beings. the lungs may become inflamed, making breathing more difficult. for some people, the infection becomes severe and leads to critical care requirements. the anatomy of sars cov-2, including its internal biological structure of spike protein legs, envelope protein, and membrane protein, surrounding the genomic rna is shown in figure 2 (a). the virus shown in figure 2(a) highlights a large diameter of about 0.1 µm with variations in sizes reported by different researchers. the spike-shaped protein legs that make up a portion of the outer capsule of the virus create the crown-like or corona-like appearance. thus, the name coronavirus. the mechanism of infection due to the surface interactions between the spike protein and the lung cells is depicted in figure 2 (b). this understanding was gathered from the genetic analysis which revealed that the mutations located in the spike surface glycoprotein might induce conformal changes and play an essential role in binding to receptors on the host cell (lungs) and determine host tropisms by leading to possible changing antigenicity [7] . viruses are fundamentally different to bacteria so the classically developed work on nano-structuring and biomimicking surfaces, such as the cicada wing, primarily targeting bacterial killing, should not be confused as a readily available knowledge to kill sars cov-2. physically, a bacterium is larger than a virus (the biggest size of a virus is smaller than the smallest known bacteria). bacteria are living cells which are 100±60 nm capable of prolific reproduction independently, whereas viruses are non-living particles, requiring a host cell for replication. also, bacteria possess a cell-wall engulfing a chromosome, whereas viruses consist of genetic material, either dna or rna, covered by a protein coating. bacterial infections can therefore be treated with high success using antibiotic drugs. although some antiviral medicines are now available, the susceptibility of viruses to react to the treatment rate of medicines is significantly reduced as they are non-living. hence, the only long-term option to eradicate viruses is the development of vaccines that stimulate the natural production of antibodies. studies suggest that the source of sars cov-2 could either be ratg13 from horseshoe bats (rhinolophus affinis), pangolins (manis javanica), or a mix of both. their transmission has occurred by zoonotic mechanisms [6, 7] . however, the coronavirus isolated from pangolins is 99% similar in a specific region of the spike protein, which corresponds to the 74 amino acids involved in the angiotensin-converting enzyme 2 (ace 2) receptor binding domain, which allows the virus to enter human cells to infect them as shown in figure 2 (b). the virus ratg13 isolated from rhinolophus affinis bats is highly divergent in this specific region (only 77 % similarity). this observation indicates that the coronavirus isolated from pangolins can enter human cells, whereas coronavirus isolated from rhinolophus affinis bats is unable to enter human cells. the sars cov-2 has a high transmissible efficiency and covid-19 has high morbidity and mortality. a popular but possibly flawed measure for assessing fatality of disease is the use of deaths/case counts. this measure would yield a fatality rate of 6.6% for covid-19 as of 17th may 2020 [8] . the problem with this measure is that case counts reflect the number of tests that were done rather than infections, and the deaths lag the cases because fatality (if observed) may happen several days after the case is identified. a lag in reporting case numbers and incorrect tests may also occur. an alternative measure is the case fatality rate (cfr), which is the ratio of deaths / (deaths + recovered cases). this measure would yield a fatality rate of 14.6% [9] . the consensus is that the covid-19 disease has high fatality and can exceed the fatality ratio of the century-old "spanish flu", which had a 10% cfr [11] . however, the data analysis of callaway et al. [10] shown in figure 3 suggests that covid-19's cfr is lower than that of mers and ebola and that its infection rate (r0 -the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection) suggests that the infection can spread more easily than other diseases, including seasonal influenza. a further comparison of three different episodes of epidemics and pandemics caused by the family of coronavirus, namely, sars cov-1, mers and sars cov-2, is depicted in table 1 . the exact mechanism of these drugs towards the virus is yet to be completely understood. however, the mechanism where a drug affects the replication of viruses in-vivo is a broadly accepted concept. in general, viruses replicate via protein processing using endosomes within golgi bodies. a drug such as hcq increases the ph of the golgi bodies making them more basic, thus disrupting the integrity of the internal nucleocapsid protein (see figure 2a ). this denatures the protein of the coronavirus rendering it dysfunctional. therefore, the rationale for using hcq is built on the premise that the change in ph brought about by the drug inhibits the endosomal transport necessary to spread the infection, hence the patient recovers. another short-term treatment being implemented by some hospitals across the world is to infuse patients with the antibody-rich blood plasma of people who have recovered from covid19 [13] . this approach has been used during disease outbreaks for over a century. however, the approach carries significant risk in terms of the already immunocompromised patients' immune response after administration, and results may vary between patients. as an early effort of investigation of the problem from scratch, researchers at toho university in japan used high-sensitivity cameras and laser beam guidance experiments to deduce that saliva spray during a sneeze (potentially containing thousands of viruses) can be classified into large vs small droplets or droplets vs aerosols. the droplets, due to their heavier weight, fall off, whereas aerosols remain airborne for a few hours due to their relatively small size. prima facie evidence suggests that the coronavirus has escalated to a pandemic due to the high contagion occurring via this 'airborne' spread model. recently, the possibility of asymptomatic or oligosymptomatic infection has also been highlighted [14] . the aerosols may circulate near an infected patient in an airborne condition depending on the local conditions (airflow rate, humidity, dryness) for up to a few hours, even after the infected person has left the location. hence, the chances of contracting coronavirus are relatively high by merely occupying the same vicinity where an infected person has been or passed through. researchers have experimentally evaluated the stability of sars cov-2 recently, and these comparisons are shown in figure 4 [15, 16] . it is noteworthy that sars cov-2 was stable in the aerosol (airborne) form for up to 3 hours. as opposed to this, the virus appears to be stable on surgical masks or stainless-steel surfaces for up to 7 days and for up to 4 days on smooth surfaces such as glass or currency notes. the same research also shows that the application of hand soap does not immediately deactivate the virus but rather takes up to 5 minutes. therefore, a 5-minute waiting period after a handwash is required before bringing hands in contact with face, mouth or nose. covid-19 is not only present in the airway secretions of infected patients when they sneeze, but also when they simply breathe out or speak. studies have shown that covid-19 is also present in other body fluids of infected people, such as faeces, blood [17], oral fluids, anal secretions [18] , tears [19] , and urine [20] . the virus primarily attacks the respiratory system, however, new evidence shows the virus is not filtered by the kidneys, as traces of virus can be seen in sewage systems [8] . therefore, as a mitigation strategy, testing of these fluids, which can be available and abundant in the wider population can be done for identifying the most effective areas. overall, when people are in close contact with one another, then transmission is more likely. most sources for infection worldwide have happened in an enclosed space, including homes, offices, public transport and restaurants. a second spreading pathway for the virus is through touching a surface or object that has the virus on it and then touching one's own mouth, nose, or eyes. if one is in a wellventilated space with fewer people, even for a longer period, the risk of infection is low. sustained contact with an infected person, even for a short period, even without a cough or sneeze, can spread the infection. by the virtue of disturbing the cell programming, covid-19 possesses the capability to cause a surprise attack on almost any part of the body ranging from lungs, heart, blood vessels, brain, eyes, nose, liver, kidneys and intestine. a schematic representation of this adverse impact is shown in figure 5(a) [21] . recent literature suggests that apart from the airway, the human brain may also be targeted by the virus -see figure 5 (b) and figure 6 [22] . patients have reported having mild (anosmia and ageusia) to severe (encephalopathy) neurological manifestations, and if true, it makes sars cov-2 more lethal. [21] (b) tissue distribution of ace2 receptors in humans [23] (c) possible neuro disorders due to sars cov-2 [22] and (d) life cycle of sars cov-2 in host cells [24] . (figures reprinted with permission) our nasal lining tissue contains a rich number of cell receptors called angiotensinconverting enzyme 2 (ace2), which are favourable sites for the sars cov-2 to attach its spiked protein to, thus paving way for the entrance of the virus inside the body. once attached to the cell, sars cov-2 can change cell programming, replicate itself, and attack new cells at a very rapid pace. within a week of entrance into the body, the virus exhibits effects. during this time, the person may show early symptoms such as fever, dry cough, sore throat, loss of smell and taste, or head and body aches. at this point, the failure of the immunity in defeating the virus means giving the virus a way forward to enter into the respiratory system, where the lungs are attacked. the lungs also have a cell lining rich in ace2 [22] . as the immune system continues to fight the sars cov-2, the supply of healthy oxygen is disrupted. as the disease progresses inside the body, the white blood cells release inflammatory molecules or chemokines, which attack and kill the virusinfected immune cells, leaving the dead cells and pus behind. this affects healthy oxygen transfer in the lungs and is the stage where the patient starts to complain of pneumonia, coughing, fever, and rapid, shallow respiration. acute respiratory distress syndrome may develop. at this stage, the lungs start to be filled with opaque black spots signifying closure of the air pores, and such patients require ventilator support. the survivors of this severity of infection can end up having long-term complications. a few hospitals have successfully applied artificial intelligence to monitor the recovery rate by monitoring the coronascorea general term used to quantify the extent of the blocked pores (in cm 3 ) [25] long-term research measures, advanced manufacturing and metrology have pivotal roles to play in containing a pandemic. specifically, the development of engineering innovations is timely for the control of the covid-19 pandemic. for diagnostic testing to be useful for informing doctors and governments about the true incidence at any one time of coronavirus in the population, it needs to be inexpensive, high in sensitivity and specificity (sensitivity refers to the ability of a test to correctly identify those with the disease or true positive rate, whereas specificity refers to the ability of a test to correctly identify those without the disease or true negative rate) and easy to use for non-experts. as doctors are treating infected patients in this emergent time in an unprepared state, emergent manufacturing measures can help design better testing equipment and thus help in both short and long term to tackle this problem. the most significant challenge now lies in probing early-stage symptoms of covid-19. for a relatively late stage detection in severe cases, chest computer tomography (ct) using x-ray probes (providing >90% sensitivity) has proved to be a more reliable test assay in comparison to the reverse-transcription polymerasechain-reaction (rt-pcr) test and other sensor-based detection methods currently being pursued [27] . since the nervous system and respiratory dysregulation are both likely to co-exist, covid-19 testing should be done by combining brain mri and rt-pcr tests as shown in figure 7(a) [28] . however, caution is required in the analysis of results, such that covid-19 should not be confused with drug-resistant tuberculosis (tb) as both would show symptoms of damages in the lungs. in an attempt to boost the testing in a populous country such as india, the indian council of medical research (icmr) has approved the use of diagnostic machines used for testing drug-resistant tuberculosis under the guidance that the throat/nasal swabs are collected in the viral transport medium [29] . interestingly, the pcr test cannot identify asymptomatic infections or those people who were exposed to or infected with covid-19 in the past and did not suffer from the disease or have recovered from covid-19 and may still be spreading the virus (carriers). therefore, different tests may be required to collate vital information required by government bodies to carry out a risk-benefit analysis to relax lockdown measures to protect their economies. immunodiagnostic kits such as a lab-on-a-chip are being developed for asymptomatic detection of covid-19 [30] . a lab-on-chip (figure 7 (b) works on the principle of detecting the presence of patient-generated antibodies against the virus that causes a specific disease, in this case, covid-19. the test uses a lateral flow immunoassay to assess the presence of an analyte from a patient sample or specimen and detects two types of antibody isotypes: igm and igg. igm antibodies are the first antibodies to appear in response to a novel antigen and imply a more recently initiated infection while igg antibodies are generated later in the course of infection and possess a higher affinity for the target antigen, meaning they are more specifically able to bind the substance which caused the immune response. a test is declared positive if either one or both antibodies are detected during the test, similar to widely used pregnancy tests. the test consists of an anti-human igg coating in the g test line region and an igm coating the m test line region (see figure 7 (b). during testing, the sample (blood, urine etc) reacts with sars-cov-2 antigen-coated gold nanoparticles (aunp) in the conjugation pad of the test cassette. any antibody in the patient sample that recognises the sars-cov-2 antigen binds to the antigen-aunp complex. the mixture then migrates laterally across the membrane by capillary action/lateral flow. as these human antibody/antigen/aunp complexes move across the test lines, they are captured at the anti-human igm 'm' line, the anti-human igg 'g' line, or both, depending on the antibody contents of the specimen. the sample first reaches the anti-human igm antibodies which coat the m line. if the specimen contains igm antibodies to sars-cov-2, a coloured line will appear in the m test line region. next, the sample reaches the anti-human igg antibodies which coat the g line. if a specimen contains igg antibodies to sars-cov-2, the conjugate-specimen complex reacts with anti-human igg. a coloured line appears in the g test line region as a result. the rabbit igg-aunp complexes are captured by the control line (which contains anti-rabbit-igg). this visible line indicates that there has been successful lateral flow across the detection strip. the last check ensures that the sample had enough volume to move across the entirety of the test cassette. only human antibody/sars-cov-2 antigen/aunp complexes will produce a visible red or pink line at the m or g line. other antibodies produce no colour. the accuracy of these lab-on-chip tests is still being debated as it depends on two key parameters, sensitivity and specificity. to date, igg related sensitivity and specificity has been found to be higher than that of igm. a schematic diagram in figure 7(c) and figure 7(d) shows that unlike currently available diagnostic methods, field-effect transistor (fet)-based biosensing devices may have several advantages, including the ability to make highly sensitive and instantaneous measurements using small amounts of analytes [31] . the fet sensor shown in figure 7(d) makes use of a graphene sheet since graphene-based fet biosensors can detect surrounding changes on their surface and provide an optimal sensing environment for ultrasensitive and low-noise detection. from this standpoint, graphene-based fet technology is attractive for applications related to the sensitive immunological diagnosis. graphene as a sensing material is selected, and sars-cov-2 spike antibody is conjugated onto the graphene sheet via 1-pyrenebutyric acid n-hydroxysuccinimide ester [31] (figures reprinted with permission) a group of researchers at mit and harvard are developing coronavirus-identifying sensor embedded face masks. this ongoing work is an extension to their previous work where they developed a low-cost method to detect a zika virus [33] . in this technique, the sensor is made by using genetic material such as the rna or the dna which binds to the viruses. the researchers used a lyophilizer to freeze-dry the genetic material onto the fabric of the mask. the material deposited onto the fabric remains stable for many months (at room temperature) and the detection process starts merely by the presence of moisture (such as saliva). the detection signal is small (in terms of voltage) and can be detected by an additional fluorimeter device that can quantify this signal and emit in form of a fluorescent light. thus, one can expect to see light glowing masks to detect coronavirus in the future. fumigation chambers allow quick disinfection of a person while visiting areas such as hospitals, universities or airports. the aim is to use tubes releasing hydrogen peroxide in a chamber designed to be five-feet wide and seven-feet tall. the fumigation chamber usually seals automatically after the person's entry to avoid any leakage outside of the chamber and has designated sensors facilitating the chamber entry. the disinfection lasts for five seconds. it is to be noted here that hydrogen peroxide has also been recommended by the food and drug administration (fda) to be used as a sterilisation material to decontaminate n95 or n95-equivalent respirators for reuse by health care workers in hospital settings [34] . a populist view is that sunlight and high temperature during peak summers kills the coronavirus, which would help containment of its spread. it is reported that sars cov-2 does not survive beyond 5 min after being exposed to 70ºc [16] . however, it has yet to be ascertained as to how long does sunlight take to deactivate sars cov-2 and at what intensity. a more specific question is whether ultra-violet (uv) light can kill coronavirus? sunlight usually contains three types of uv: uva (320-400 nm), uvb (280-320 nm), and uvc (200-280 nm). uva and uvb can both cause sunburn, however, uvc is shorter and a more energetic wavelength of light. while uvc is effective at destroying genetic material, whether in humans or viral particles, it is filtered by the ozone layer and does not reach the earth's surface. preliminary findings from the national biodefense analysis and countermeasures centre of the usa (which houses a bsl-4 level lab) indicate that "sunlight seems to be very detrimental to the virus… within minutes, the majority of the virus is inactivated on surfaces and in the air in direct sunlight." [35] . research on the use of uv as a treatment is still evolving and the behaviour of sars cov-2 under uv light is unknown. results were relatively favourable for sars cov-1 treatment with uvc [36, 37] . sars cov-1 was efficiently inactivated after 40 minutes of uvc exposure (at about a wavelength of 254 nm), whereas addition of psoralen (a light-sensitive drug) to uva enhances inactivation of the sars cov-1. popular press reports suggest that uv light booths are capable of deactivating coronavirus without any human contact and are proposed to be deployed ( figure 8 ). one must be cautious, since uvc can be dangerous to the skin, causing burns within seconds and harmful to the eyes if observed directly. therefore, risk assessment and associated precautions would need to be deployed that may render this strategy difficult in the short-term. 3.5.1. antimicrobial coatings chouirfa et al. [39] summarised nanomaterials based coatings for antibacterial applications and xing et al. [40] have summarised the potential of natural polymer chitosan as an antimicrobial agent ( figure 9 ). their research on antimicrobial properties of a nanocomposite coating formed by polysaccharide 1-deoxylactit-1-yl chitosan (chitlac) and silver nanoparticles (nag) on methacrylate thermosets showed satisfactory results. figure 9 : antimicrobial mechanism of chitosan-based coating with antimicrobial agents. reprinted with permission from [40] . antimicrobial surfaces are based on three main mechanisms (see figure 10 ): the anti-biofouling mechanism which repels microbes and prevents them from adhering to the surface, the release-killing mechanism where microbes are killed in the nearsurface environment with a release of antimicrobial agents and the contact-killing mechanism where microbes adhere and are killed on the surface [41, 42] . researchers have also experimented with developing long-lasting antimicrobial surfaces to stop spreading pathogenic microbes through commonly touched surfaces or at-risk surfaces and have focused on the use of antimicrobial/antiviral materials such as copper. experimental trials for copper oxide impregnated respiratory protective facemasks have yielded 100% efficiency in eradicating the infectivity of human and avian influenza a virus in simulated breathing conditions [43] . warnes et al. [44] have shown that the surfaces of dry copper alloys are lethal to viruses such as mnv-1 at room temperature, with higher copper content being more time-efficient. generally, the antimicrobial activity of copper is attributed to oxidative behaviour of copper and the solubility properties of copper oxides [45] . more recently, surface texturing of copper via cold spray methods has shown enhanced promise as an antiviral agent [46] . combining the aforementioned antimicrobial contact-killing properties of copper, the anti-adhesion properties of polymeric micelles and the release-kill abilities of chlorine dioxide (clo2), li et al. [47] developed a multifunctional coating viricidal for influenza virus h1n1. this multifunctional coating is composed of clo2 encapsulated in polymeric micelles (with slow on-demand release) on which copper nanoparticles were covalently tethered. other studies have investigated hydrophobic polycationic coatings as antimicrobial coatings [48] [49] [50] . hsu et al. [51] investigated the mechanism by which the n,n-dodecyl,methyl-polyethelenimine (pei) coated surfaces killed the influenza a virus. it was concluded that upon contact with the coated surface, the virus adheres irreversibly and through hydrophobic and electrostatic interactions, the virus' disintegration is then initiated resulting in rna leakage into the solution. the incorporation of pei into protective mask textiles has also been investigated with nearly a 1000-fold improvement in the capture of the t4d bacteriophage virus of escherichia coli b [52] . finally, the direct mechanical action of sharp nanostructures such as darts, blades and spikes as a kind "mechano-cide" has been shown to have some success for bacteria, but remains largely unexplored for viruses [53] . from a contact mechanics perspective, the combined effect of sharp ( somewhat surprisingly, while researchers have investigated bactericidal properties of nanoparticles of silver, yet the current understanding of the interaction of these nanoparticles with viruses is limited. however, some positive results are reported and, based on these reports, this direction of manufacturing research holds a good promise to tackle sars cov-2. previous studies showed that the size of nanoparticle is critical to manifest a viricidal effect. for example, a nanoparticle size of less than 25 nm was found to be effective against tacaribe virus [56] , while a particle size of between 7 to 20 nm worked well against herpes simplex virus (hsv) type 1/2 and human parainfluenza virus type-3 [57] . nakamura et al. [58] reported that materials with immobilised silver nanoparticles possess enhanced microbicidal activities against the virus. these researchers developed a material using silver nanoparticle absorbed on a chitin sheet having a nanoscale fibre-like surface structure shown in figure 11 and obtained favourable results against h1n1influenza a virus. figure 11 : the mechanism of viricidal activity of silver (ag) nanoparticles (np) chitin nanofiber sheets showing strong antimicrobial activity via reactive oxygen species (ros) and silver ions on the substrate. reprinted with permission from [58] . moreover, the unique characteristics of metallic nanoparticles such as high surface to volume ratio, surface-enhanced raman scattering and localized surface plasmon resonance can be utilised for virus detection and therapy via destruction through laser-induced localised hypothermia as well. some of the candidate nanoparticles are metallic and high entropy alloy nanoparticles (agauptpdcu high entropy nanoparticles, feo nps, ag nps, tio2 nps, au nps, ag-au core-shell nps) [59] . for this purpose, uv-visible spectroscopy can be deployed to study the surface plasmon resonance, refractive index, and fluorescence change when nanoparticles interact with virus particles. nanoparticle-based investigation can help detect and inactivate viruses (figure 12 ). specific to coronavirus, graphene oxide sheets with silver nanoparticles (go-ag nps) were reported to inhibit the growth of feline coronavirus (fcov) by up to 25%, in comparison to pure go that inhibited it only up to 16% [60] . additionally, chiral biosensor with self-assembled chiral gold nanohybrids (cau nps) on account of multiple plasmonic scattering showed better detection performance on coronavirus [61] . figure 12 : nanoparticle based therapy for sars cov-2. reprinted with permission from [59] as with all fundamental and translation nanomaterial research, progress is not immediate. caution is required with nanomaterial technologies, as the long-term impact on human health and the environment of free nanoparticles has not been ascertained, and this may ultimately pose greater risk, particularly in the liver and respiratory tract of human beings and in ecosystems. lack of governmental regulation strategies for nanomaterials can also hinder the speed of approval and ultimately the availability in the marketplace. nevertheless, a call has gone out to nanomedicine researchers to utilise their existing knowledge base and translate their technologies towards covid-19, should the outbreak last more than 12 months [62] . filtration efficiency is a strong measure of penetration prevention of aerosols through mask filters and is usually required to be above 98% for surgical face masks [63] . ultrasonic welding is usually deployed to produce filters with sufficient filtration efficiency. both polymer and textile-based masks are popular and can benefit from the adoption of sequential micromachining techniques [64] . a surgical mask (procedure mask) is worn by health professionals during surgery to avoid exposure to aerosols. such masks are not designed to protect the wearer from inhaling airborne bacteria or virus particles and are less effective than respirators, such as n95 or niosh masks which provide better protection due to their material, shape and tight seal. the who laboratory biosafety manual necessitates biosafety level 2 (bsl-2) requirements for non-propagative diagnostic laboratories and bsl-3 for laboratories handling high concentrations of live sars-cov-2. according to the manual and the who biosafety guidance for sars-cov-2, the exhaust air from such laboratories should be discharged through high-efficiency particulate air (hepa) filters. it is worth mentioning that particle collection efficiency of such mechanical filtering methods decreases to about 50% at particle sizes of 0.5 µm due to diffusion and diffusioninterception regimes of particles with sizes in the range from 0.05 up to 1 µm [21] . therefore, hepa filters are not ideal in screening the viruses like sars cov-2 which has a typical diameter from 60 nm to 160 nm [22] . mass production of appropriate filters to screen the virus entry is a micromanufacturing challenge. this could potentially involve technologies such as direct laser micromachining or punch-based microstamping methods. for this purpose, a plasma spraying, or laser micromachining method may be used to obtain a well-suited punch which can be used to stamp (pierce) polymer sheets (e.g., pet), to achieve appropriate filter sizes. another candidate process of subtractive manufacturing is metal anisotropic reactive ion etching with oxidation (mario) [65] . an illustration of how the proposed micromachining strategies can be deployed for scalable fabrication of filters to screen virus scale particles is shown in figure 13 . while self-assembly techniques such as block copolymers have shown promise filtering small viral particles such as human rhinovirus [66] , direct printing methods allow greater engineering control over pore size and spacing, critical to tuning membrane efficiency, fluid resistance and mechanical strength. protection of surrounding or nearby people is important and an infected patient can help to control the spread by wearing a mask, leading to the concept of social distancing suggested by various governments. the safe distance guideline is an important concept especially in populous countries where an assembly of people on the streets can cause the spread to grow exponentially. keeping this in mind, the who urged people to maintain a safe social physical distance of about 3 ft (~1 m), while the centre of disease control and prevention recommends this to be 6 ft (~2 m). these limits are now challenged by recent research that suggests this safe distance should be 23 to 27 ft (7 to 8 m) [69] . the same study also suggested that the currently available commercial masks need to be redesigned. it was suggested that the masks available at present are not suitable for containment of sprayed aerosols (during a sneeze) travelling at the velocity of 108 kmph [70] , as this increases the possibility of escape of viruses through contaminated droplets from edges of the mask making nearby people more vulnerable to contracting the coronavirus. also, chin et al. [16] tested the strength of the virus and suggested that the virus is highly stable at 4ºc as well as in the ph range of 3 to 10. the virus was found to be detectable on a mask surface even after 7 days. these findings suggest a product design strategy to develop more appropriate masks for handling exhalations travelling at high speeds by considering human ergonomics, material aspects, antimicrobial nature and structural aspect. while the design and strategies for developing these new types of masks are underway, a possible technique for deploying the extant fabrication methods would be to merge the two approaches, namely, additive and subtractive manufacturing methods described above. this development would mean that even in the current landscape, a new mask-making strategy would provide more protection than the currently available masks. astm f2100-07 is the relevant international standard that details specifications of materials to be used in medical face masks. however, the current standards do not capture the techniques required to make the mask reusable especially as the current materials are yet to be tested against sars cov-2. as of now, curad antiviral isolation masks making use of a cocktail coating (citric acid, zinc and copper) are available as an option to disinfecting the outer surface of the mask. these are useful for medical professionals as they can come in contact with the virus infected aerosols more frequently. another concept is that of a 'germ trap' surface [71] , which is akin to fooling a virus. the team at the university of manchester, uk identified specific glycoproteins that have carbohydrates attached to their surface, similar to those seen on the surface of the cell of the nasal passages. this study suggests that a glycoprotein biocoating on a snood surface [72] denatures a virus by causing the same interfacial chemical reaction between the spike proteins and carbohydrate cell surface as the one when the coronavirus attaches to the ace2 receptors, but due to unavailability of any physical cells to invade on the snood surface, the virus decomposes and becomes deactivated immediately after landing on the textile surface (see figure 14 ). the efficiency of germ trap coating in achieving its goal is indicated to be 96%. based upon the existing literature, an immediate measure to functionalise the personal protective equipment's (ppes) could be to introduce the use of antimicrobial coatings comprising of proven materials (e.g., zinc and sodium [73, 74] based compounds) on the surface of ppes, especially the shields and visors. such coatings can be deposited by additive methods such as spraying (in 3d) or via roll to roll (r2r) manufacturing. in terms of processing techniques, one limitation of thermal spraying is that it requires heat resistant feedstock materials, limiting the use of most of the chemical species traditionally used to functionalise surfaces, such as polyethylene glycol (peg) [75] . in view of this limitation, a possible research avenue is to develop functional coatings with viricidal properties such that the coating ingredients do not degrade at high temperatures, thus providing a controlled release over time. with this goal in mind, a suitable processing and material matrix availability is crucial to obtain a coating to possess desirable advantages in the medical field. on the other hand, the use of thermal sprayed hydroxyapatite (ha) coatings on orthopaedic implants has been widely adopted in the medical field since the late 1980s [76] . as reported in the early 2000s [77] , the use of thermal sprayed ha coatings on metal implants presents several advantages and a positive potential for its use in the medical field [78] . taking into consideration the status of ha as the standard in thermal sprayed coatings and the decades of research on its behaviour and response to living tissue [79] , the choice of ha as a base material for the development of anti-microbial functional coatings has been most popular to date. at a personal level, deploying smart ppe incorporating viral detection capability into masks, gloves or wearing "viral dosimeter" badges might help monitor the strength of direct transmission vectors as well as environmental exposure rates and accumulation. conversely, masks could collect exhaled viral particles for early detection of infection [70] . detection could be implemented as microfluidic channels functionalized with bioelectronic miniaturized detection schemes [80, 81] with specific virus sensitivity [82, 83] . local area smart sensing filter textiles incorporated into mobile or in-place ventilation systems designed to both filter and detect could also help provide early alert alarms and protection in buildings and other areas of restricted air replacement. the importance of wearing a mask by the infected person and by a healthy person coming in the vicinity of the infected person is ranked on the priority order shown by the cartoon model in figure 15 . safe disposal of materials used in the treatment of infected patients such as gloves, masks, test samples, clothes or the human waste, especially in icu patients who may be closer to death is a challenging task. in addition to the possibility of an infection, this waste could lead to other secondary issues including emergence of a new category of virus/bacteria. hence, safe disposal of biomedical waste is very important. additionally, gaining support from members of the public to adequately dispose of their used personal masks etc. is essential. recently, an absorbent gel with embedded disinfecting material has been developed at sree chitra tirunal institute for medical sciences and technology, india for liquid respiratory and other body fluid solidification and disinfection for the safe management of infected respiratory secretions. this material helps to solidify the liquid respiratory secretions from icu patients or those with copious secretions treated in the wards. the material so collected becomes fit for disposal through the usual incineration system for biomedical wastes. newer guidelines are required to refine the existing risk assessments procedures [84] . big data analytics and extant research utilizes accelerated development of techniques for data mining, machine learning and use of artificial intelligence (ai) that shows promise in the treatment of sars cov-2. as a direct benefit to this approach, a digitalised shadow of the data to study plausible scenarios of certainty of an event becomes easier. as for sars cov-2, genome data now exist offering scope for soft-computing application researchers as well as those involved in ai based research to offer new insights into the area. as an example, the global initiative on sharing all influenza data (gisaid) database (https://www.gisaid.org), made available in march 2020, contains a compilation of over 24,000 sars-cov-2 complete and partial genomes from all over the globe since december 2019 [85] . recently, researchers from cambridge used phylogenetic network on 160 complete genomes of sars cov-2 [85] to predict probable mutation and migration paths of the coronavirus. atomistic modelling and molecular docking [86] can hold the key to a scientific breakthrough to address questions surrounding sars cov-2. the development of vaccines, antibodies and diagnostics is dependent in a large measure on our understanding of the interfacial science between the spike (s) glycoprotein of sars cov-2 and ace2 receptor in human lung cell (as shown earlier in figure 2 ). wrapp et al. [87] obtained a cryo-electron microscopy structure of the sars cov-2 s trimer in the metastable prefusion conformation, showing it undergoes a transient (hide and active states) structural rearrangement. their results relying on surface plasmonic resonance elucidated a stronger affinity of sars cov-2 with ace2 compared to sars cov-1, and shed light on two states, namely, a "down state" or receptorinaccessible and an "up state" or receptor-accessible state shown in figure 16 in yet another interesting study [89] , computer-aided drug screening was used to run a test assay over 10,000 compounds as inhibitors to a key cov enzyme, m pro . ebselen was found to exhibit antiviral activity and illustrate a way forward use of this potentially promising modelling strategy to discover targeted drug and vaccine down: transient hidden state of rbd up: active binding state of rbd development. a molecular docking example shown in figure 16 (b) is yet another effective example of accelerating the drug discovery [88] . recently, liu et al. [90] carried out an aerodynamic analysis by measurement of the rna of sars cov-2. they used pre-sterilized gelatin filters (pore size of 3 μm) to collect the aerosols from different areas of two wuhan hospitals. this study classified the sampling location in three areas: ( surprisingly, the researchers detected maximum stains of sars cov-2 in patients' toilet areas, while the levels were low in the isolation wards and ventilated patient rooms. also, the medical staff areas showed peaks of high concentrations with aerosol size ranging from 0.01 micrometres to 2.5 micrometres and they were neutralised after rigorous sanitisation procedures. the study suggests that there is a likelihood of resuspension of virus-laden aerosols from the surface of medical staff's protective equipment including surgical masks during their removal while having lunch, visiting toilets or breaks etc. the source of these virus suspensions was speculated to be from the direct deposition of patient's respiratory droplets or airborne sars-cov-2 onto the protective apparel. the researchers also found that the sars-cov-2 in aerosol forms had relatively longer residence time, implying the infection remains for a relatively longer time causing further transmissions. this study serves as a practice guide on the requirements and specification after the lockdown procedures are eased to avoid recurrent infection. the exit-strategy after the lockdown must consider carefully the ventilation of offices/classrooms, maximum use of open space (preferable sunlight), regular sanitisation of clothes, hairs and hands, and proper use and disinfection of toilet areas. the data obtained by toho university (figure 17) suggests that laser technology can be employed efficiently to monitor the streamlines and microdroplets movements from a sneeze. this monitoring could be a highly effective lab-scale activity to not just guide the futuristic cfd models but also to efficiently design new masks effective for preventing diseases caused by high velocity spray caused by a sneeze. while engineering and manufacturing will undoubtedly play their part over the coming years, the interventions proposed herein can help avoid the recurrent spread and emergence of new infections. the patients who have survived while battling against covid-19 showed that they have developed antibodies to the virus. antibodies are virus-specific proteins, which have a memory of the exposure to the virus and will recognize the virus on a second exposure. antibodies help prevent future infections by detecting the virus and binding to their surfaces signalling the body's immune system to destroy such viruses or virus-infected cells. while reasons are not clear, common wisdom is that the human body does not have an adequate immune response to hiv. for covid-19, an adequate immune response does exist. therefore, a vaccine is more likely to be created successfully for sars cov-2. additionally, the observation that a large majority of people recover, either without any symptoms or with minimal symptoms such as fever and body ache, also bodes well for the development of a vaccine. three major scenarios are currently being pursued or envisaged in tackling the disease. (i) research and trials on vaccines: clinical trials are being conducted across the globe into novel vaccines and fast-tracking approval processes are being deployed. however, scientists fear that the virus itself, like the flu, can mutate and form different strains. therefore, immunity after immunisation or contracting and surviving covid-19 may only last as short as two years. (ii) therapeutic trials using available drugs: attention is being focused to drug repurposing and advanced formulations, including antimalarial, hiv, and other antiviral and immune-modulating drugs and biomolecules. (iii) nanotechnology: study of molecules that show promise but exhibit poor physiochemical properties or toxicity is currently being formulated across the globe into advanced nanomedicine platforms, translating the knowledge gained in drug targeting and efficacy enhancement from conditions such as cancer and cardiovascular disease. such technologies aim to provide better treatment prognosis for those patients who fall ill with coronavirus related diseases. attention to immunemodulating molecules is growing, as patients who contracted severe forms of covid-19 were reported to experience notorious cytokine storms which ultimately 2 m 1 m lead to their death. ability to suppress such immunological responses could be one key to controlling the progression of the virus from mild to severe infection. lessons learned during this pandemic will also impact the outlook for other viruses. these include governmental pandemic funding allocation, stockpiling of medical protective equipment and emergency aid strategies within and between countries across the globe. as the coronavirus problem increased across the globe in 2020, many questions have been raised regarding what more governments could have done, why they did not act more quickly, and what were the fundamental failures within their policy. over time, addressing these issues will pave the way for a more streamlined and effective future response. in addition to this, contact tracing technology is being heavily invested in across the globe, with the intention that citizens would be able to download mobile applications, which could inform them (and the authorities) if they had been exposed to another person who tested positive to covid-19. whilst early trials seem positive, the longer-term question remains over privacy and ownership of personal data collected by such applications. access to death records inside countries and across continents will allow identification of high-risk population categories which will aid risk prevention. the positive news is that this pandemic has cemented the importance of scientific integrity, the inclusion of scientific advisors into government, and the role of science in society. while this may offer little solace at such an upsetting time, yet, with the power of science, this disease will be managed unlike many other viral threats over the years. currently, vaccine trials are ongoing at various phases of progress in different countries (see table 3 ) and good news may be expected soon. [95] . the world has seen a surge in the use of digital tools being growingly used for teaching, research, consultation, banking and day to day activities. digital health innovation has been a prime example. these approaches culminated in the development of telemedicine consultation. the current situation has also driven many changes in work-life routines such as less travel and digital technology-based remote work. the coronavirus pandemic has brought significant disruption and caused severe emotional, sentimental and financial losses. there is even a chance that life on the planet will never be the same again and many stringent safety measures will continue to be followed in the time to come while using public transport, air travel, or while visiting touristic places. the continued extension of lockdowns (e.g., lockdown 1.0 to lockdown 4.0 in india) has resulted in making people restless when staying indoors. countries who were not very resilient in adapting to the situation even saw disrupted supply chains, disturbed migrant workers, lack of food and other supplies and unavailability of essential items -a situation comparable to a natural disaster. however, every disaster brings forth a new cycle of life and the episode of covid-19 did bring some good things. countries facing severe pollution in air, water, and land saw a life not seen in the last many decades. social websites and digital tools were used heavily to share the beauty of nature. rivers got cleaner, the air became more breathable, and the sky got clearer [96] . as a result of this transition, even climate change and transition in weather were observed in many places and it will be befitting to say that we witnessed how "nature self-heals and mends itself". a prime example of climate change as a result of lockdown can be seen in china, europe and in india (see figure 18 ). india has faced two major challenges for many years in the wake of rapid urbanisation: alarming levels of air pollution and a rapid decrease in the availability of clean water, especially from rivers like the ganga. the government of india had earlier set up a mega project called "namami gange" [97] for freeing the rivers from industrial wastes. the project is of such importance that when addressing the indian community at madison square garden in new york in 2014, the prime minister of india mr narendra modi had said, "if we can clean the ganga, it will be a huge help for 40% population of the country." covid-19 has rejuvenated the ganga and many other rivers around the world, making them cleaner to a point that their water was reported to be potable [98] . the learning from the episode of covid-19 has been that resources offered by mother nature are meant to be used and not to be "exploited". if this simple rule is forgotten, then the world may continue to witness a regular self-healing cycle. on this occasion it was covid-19 but the next time, it could be readjustments in the ecosystem caused by a surge in the carbon emissions. researchers are reporting a decrease in solar activity leading to an increased flux of energetic particles in our galaxy [101] . before it is too late to realize, and the entire human race wipes-off the face of the earth due to the climate change, we must take this pandemic as a wake-up call towards being considerate to the environment. what has apparently come clearer though is that problems like biohazards primarily emerge due to our lifestyle (e.g., consumption patterns including eating habits) or mishandling of biowastes (see figure 19 ). there is an absolute necessity to pay utmost attention to biosafety and implementation of effective iso standards worldwide. health of people is also closely connected to the health of animals and our shared environment. this is because people, animals, plants, and our environment are interdependent [102] and this direction of research considers the concept of "one health". in the wake of the covid-19 pandemic, the world witnessed an all-time-high demand of ventilators, ppe's, masks, bed liners, other essential health supplies and medicines. the pandemic struck everywhere, including the largest manufacturing economiesand pretty much all at once. as a result, most nations experienced manufacturing shocks. the two shocks that have impacted manufacturing worldwide are: • supply shock: the containment measures (such as lockdowns and social distancing) kept the workers away and resulted in reduced productivity and output. • demand shock: customer consumption patterns started changing (e.g., movement away from "non-essentials") and this affected the demand for a large variety of manufactured goods and associated services. as the pandemic spread, a few countries were resilient enough to cope with the pace of transformed supply chain requirements while many others who had earlier (in pre-covid-19 era) aligned themselves to outsourced or cloud-based manufacturing, primarily driven by low-cost, became hugely dependent for their essential supplies on other countries (primarily china the manufacturing related lesson learned from the covid-19 episode is that pandemics can affect manufacturing in several geographical locations simultaneously and therefore can affect an individual nation's surge capacity to deliver essential supplies such as diagnostics, drugs and vaccines to its population. going forward, this lesson will critically affect thoughts on manufacturing strategy and low-cost based outsourcing, and we may see a sustained push towards development of resilient indigenous manufacturing capabilities and a decreasing reliance on low-cost based outsourced manufacturing. a second trend that we perceive is an increasing focus on digitised automation and use of automated production systems including the use of robotics in day to day life as well as deployment of embedded robotics in manufacturing operations. an example of a futuristic automation capability was displayed at the indian institute of technology guwahati who developed remote controlled food delivery robot for covid-19 isolation wards (see figure 20) . the robot was designed for 6 hours run when fully charged. antimicrobial resistance (amr) refers to the resistance of microbes to antimicrobial drugs or "microbial immunity". the who as well as several national health organizations have identified antibiotic resistance as one of the greatest threats to global public health, economic growth, agriculture, economic security and national security. around the globe, people are being admitted to hospitals with infections that do not respond to antibiotic treatment. the problem of amr is rooted in the fact that when microbes are repeatedly exposed to antibiotics, they mutate to produce strains that are resistant to the antibiotic and are therefore able to resist the effects of medication that could successfully treat the microbe. in 2014, lord jim o'neill and his team published a review commissioned by the united kingdom government entitled, "antimicrobial resistance: tackling a crisis for the health and wealth of nations" (the amr review) which is in line to the question that de kraker et al. [104] asked "will 10 million people die a year due to amr by 2050?" the problem of amr is connected to that of covid-19 with respect to the emergence of zoonotic diseases. the trend of overuse and/or misuse of antimicrobials, excess use of certain antibiotics in animals, and pharmaceutical industry pollution can lead to continuous emergence of zoonotic diseases. excessive use of antimicrobials stresses the naturally occurring microbiome and allows for resistant bacteria to become dominant. indeed, research has suggested that amr might spread to humans through food products of animal origin, the environment, and by direct contact in the case of agricultural workers. addressing the issue of amr as well as others shown in figure 21 is thus a global priority as its impact on claiming lives is no less than that of covid-19 [105]. the rapid emergence of the covid-19 pandemic provided minimal time for welldirected resource mobilization, and almost every country was tested for its resilience in its medical and manufacturing abilities during the first half of 2020. the number of tragic health cases pushed organizations such as the fda to allow emergency use authorisation of various drugs without a systematic testing protocol, and among the 70 drugs tried, favipiravir and tocilizumab were rated most effective. amidst the chaotic situation, the growing use of digital tools for professional communications and artificial intelligence to monitor the recovery of covid-19 patients showed some positive outcomes. a major question remains open to date, "how can the symptoms of covid-19 be detected in their early stages?" while more research is needed on the instrumentation and manufacturing sides, there are clear opportunities identified from the available scientific knowledgebase. in relatively advanced stages of the symptoms, rapid measurements by combining chest computer tomography (ct) and reverse-transcription polymerase-chain-reaction (rt-pcr) tests seem to provide a high confidence level in the screening. more work is needed on the sensing side for detection of the virus in the primitive stages. definitive promise has been exhibited using laser technology to monitor the aerosol spread and to detect the rna of the virus and gain a deeper understanding of the aerodynamic properties of emergent viruses. further development of fumigation chambers and ultra-violet chambers seem to hold promise as precautionary measures that can be implemented in public places like malls, airports, theatres and train stations etc. in this paper, we have also highlighted the possibilities of developing novel tools such as lab-on-the-chip, in addition to developing advanced personal protective equipment (ppe) using combinatorial additive and subtractive manufacturing techniques such as roll-to-roll manufacturing and thermal spray. these technologies allow the capability to filter the coronavirus, which has a diameter in the range of 100 ± 60 nm. it is envisioned that in future, wearing masks and social distancing would be mandated to avoid the recurrent spread of the virus. in the long term, micro-manufacturers, medical professionals, metrology engineers, material scientists and virologists will need to work in a more interdisciplinary way to develop modelling informed fabrication strategies. accelerated use of molecular modelling approaches -like molecular dynamics and molecular dockingalso seems to hold promise in drug and vaccine discovery to end this pandemic from its root. as society progresses to meet challenges such as covid-19, many overarching issues will become important. strong measures will need to be implemented to ensure careful handling of biowastes, indigenous capability-based manufacturing focus will become stronger and issues such as antimicrobial resistance will demand increased attention. our hope is that the post-pandemic society will better heed the warning signs from nature and work on making manufacturing systems resilient to address emerging threats. . figure 17 : airborne spread tracked by the laser experiments at toho university, japan laboratory diagnosis of emerging human coronavirus infections-the state of the art the architecture of sars-cov-2 transcriptome detection of novel coronaviruses in bats in myanmar patient-derived mutations impact pathogenicity of sars-cov-2. medrxiv the proximal origin of sars-cov-2 methods for estimating the case fatality ratio for a novel, emerging infectious disease how blood from coronavirus survivors might save lives virological assessment of hospitalized patients with covid-2019 aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 stability of sars-cov-2 in different environmental conditions. medrxiv molecular and serological investigation of 2019-ncov infected patients: implication of multiple shedding routes. emerging microbes & infections evaluation of coronavirus in tears and conjunctival secretions of patients with sars-cov-2 infection novel coronavirus can be detected in urine, blood, anal swabs and oropharyngeal swabs samples. medrxiv a rampage through the body. 2020 neurological insights of covid-19 pandemic evidence of the covid-19 virus targeting the cns: tissue distribution, host-virus interaction, and proposed neurotropic mechanisms remdesivir: a review of its discovery and development leading to emergency use authorization for treatment of covid-19 correlation of chest ct and rt-pcr testing in coronavirus disease 2019 (covid-19) in china: a report of 1014 cases updates on what acs reported: emerging evidences of covid-19 with nervous system involvement rapid detection of covid-19 causative virus (sars-cov-2) in human nasopharyngeal swab specimens using field-effect transistor-based biosensor diagnosing covid-19: the disease and tools for detection rapid, low-cost detection of zika virus using programmable biomolecular components issues-second-emergency-use-authorization-decontaminate-n95 inactivation of the coronavirus that induces severe acute respiratory syndrome, sars-cov evaluation of inactivation methods for severe acute respiratory syndrome coronavirus in noncellular blood products review of titanium surface modification techniques and coatings for antibacterial applications chitosan-based coating with antimicrobial agents: preparation, property, mechanism, and application effectiveness on fruits and vegetables antibacterial polymeric membranes: a short review surface modification of polyurethane with a hydrophilic, antibacterial polymer for improved antifouling and antibacterial function a novel anti-influenza copper oxide containing respiratory face mask inactivation of norovirus on dry copper alloy surfaces contact killing and antimicrobial properties of copper effectiveness of nanomaterial copper cold spray surfaces on inactivation of influenza a virus a smart multi-functional coating based on anti-pathogen micelles tethered with copper nanoparticles via a biosynthesis method using l-vitamin c polymeric coatings that inactivate both influenza virus and pathogenic bacteria hydrophobic polycationic coatings inactivate wild-type and zanamivir-and/or oseltamivir-resistant human and avian influenza viruses preparation, application and testing of permanent antibacterial and antiviral coatings mechanism of inactivation of influenza viruses by immobilized hydrophobic polycations a new material for airborne virus filtration mechano-bactericidal nanostructures and where to find them interaction of silver nanoparticles with tacaribe virus antiviral activity of mycosynthesized silver nanoparticles against herpes simplex virus and human parainfluenza virus type 3. international journal of nanomedicine synthesis and application of silver nanoparticles (ag nps) for the prevention of infection in healthcare workers nano-based approach to combat emerging viral (nipah virus) infection antiviral activity of graphene-silver nanocomposites against non-enveloped and enveloped viruses self-assembled star-shaped chiroplasmonic gold nanoparticles for an ultrasensitive chiro-immunosensor for viruses nano research for covid-19 surgical face masks: manufacturing methods and classification current trends and future of sequential micromachining processes on a single machine tool high-aspect-ratio bulk micromachining of titanium virus filtration membranes prepared from nanoporous block copolymers with good dimensional stability under high pressures and excellent solvent resistance the production of nanostructures by mechanical forming a direct-write, resistless hard mask for rapid nanoscale patterning of diamond. diamond and related materials turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of covid-19 respiratory virus shedding in exhaled breath and efficacy of face masks structural basis for human coronavirus attachment to sialic acid receptors zn2+ inhibits coronavirus and arterivirus rna polymerase activity in vitro and zinc ionophores block the replication of these viruses in cell culture universal and reusable virus deactivation system for respiratory protection. scientific reports thermal/oxidative degradation and stabilization of polyethylene glycol addressing processing problems associated with plasma spraying of hydroxyapatite coatings material fundamentals and clinical performance of plasma-sprayed hydroxyapatite coatings: a review the 2016 thermal spray roadmap chemical implant fixation using hydroxyl-apatite coatings: the development of a human total hip prosthesis for chemical fixation to bone using hydroxyl-apatite coatings on titanium substrates organic field-effect transistor sensors: a tutorial review interfacial electronic effects in functional biolayers integrated into organic field-effect transistors human influenza virus detection using sialyllactose-functionalized organic electrochemical transistors functional sensing interfaces of pedot: pss organic electrochemical transistors for chemical and biological sensors: a mini review covid-19: a risk assessment perspective phylogenetic network analysis of sars-cov-2 genomes anti-hiv drug repurposing against sars-cov-2 cryo-em structure of the 2019-ncov spike in the prefusion conformation fast identification of possible drug treatment of coronavirus disease-19 (covid-19) through computational drug repurposing study structure of mpro from covid-19 virus and discovery of its inhibitors aerodynamic analysis of sars-cov-2 in two wuhan hospitals covid-19: a new digital dawn? covid-19, climate change, and renewable energy research: we are all in this together, and the time to act is now pandemic spotlight on urban water quality. ecological processes update on galactic cosmic ray integral flux measurements in lunar orbit with crater. space weather biosafety materials: an emerging new research direction of materials science from covid-19 outbreak will 10 million people die a year due to antimicrobial resistance by 2050? plos medicine authors are very much thankful to the research support provided by the ukri via grants no.: (ep/k503241/1, ep/l016567/1, ep/s013652/1, ep/t001100/1, ep/s036180/1 and ep/t024607/1) as well as the gcrf/ epsrc supported sunrise program (ep/p032591/1). additionally, we acknowledge the support received from h2020 (cost actions (ca18125, ca18224, ca17136 and ca16235) and euramet empir a185 (2018)), royal academy of engineering grant no. iapp18-19\295 (indo-uk partnership), royal academy of engineering grant no. tsp1332 (south africa-uk partnership) and newton fellowship award from the royal society (nif\r1\191571). also, numerical calculations performed on the isambard bristol, uk and archer hpc were made available by the epsrc resource allocation panel (rap). all data in the manuscript will be available through cranfield university open repository. key: cord-301063-kqlra788 authors: li, dion tik shun; samaranayake, lakshman perera; leung, yiu yan; neelakantan, prasanna title: facial protection in the era of covid‐19: a narrative review date: 2020-06-07 journal: oral dis doi: 10.1111/odi.13460 sha: doc_id: 301063 cord_uid: kqlra788 we live in extraordinary times, where covid‐19 pandemic has brought the whole world to a screeching halt. tensions and contradictions that surround the pandemic ridden world include the availability, and the lack thereof, various facial protection measures to mitigate the viral spread. here, we comprehensively explore the different type of facial protection measures, including masks, needed both for the pubic and the health care workers (hcw). we discuss the anatomy, the critical issues of disinfection and reusability of masks, the alternative equipment available for the protection of the facial region from airborne diseases, such as face shields and powered air purifying respirators (papr), and the skin‐health impact of prolonged wearing of facial protection by hcw. clearly, facial protection, either in the form of masks or alternates, appears to have mitigated the pandemic as seen from the minimal covid‐19 spread in countries where public mask wearing is strictly enforced. on the contrary, the healthcare systems, that appear to have been unprepared for emergencies of this nature, should be appropriately geared to handle the imbalance of supply and demand of personal protective equipment including face masks. these are two crucial lessons we can learn from this tragic experience. the covid-19 pandemic presents one of the biggest challenges, as we transition into the third decade of the twenty-first century. collapses in the healthcare system in some parts of the world, global setback of the economy, and shortage of general and healthcare supplies are just some of the issues that policy makers have to cope with daily. amidst these challenges lies a critical question that confronts both the healthcare workers and the general public: the use of different types of facial protection. while there is no doubt that wearing different types of facial cover including face masks is an important weapon in the prevention of cross infection in the healthcare setting (meleney fl, 1926) , the efficacy of a majority of these appears to be yet unproven, and matter of conjecture and controversy. in the current setting of the global shortage of surgical masks, many authorities discourage the use of high efficiency masks in order to reserve them for those at the highest risk of contracting the disease, i.e., healthcare providers in direct contact with infected patients. at the other end of the spectrum is the argument that community-wide mask wearing could play a role in source control, which would likely decrease the rate of transmission. slowing down the speed of spread would "flatten-the-curve" and alleviate the pressure on the healthcare system, thus the quality of health care delivery would not be compromised (kenyon, 2020) . this is founded on the basis that many carriers of the virus are asymptomatic, and the incubation period or the prodrome can this article is protected by copyright. all rights reserved be lengthy, prior to the appearance of any tangible symptoms. in the absence of personal protection, these `silent carriers` as well as `super spreaders` may spread the virus through their respiratory droplets unawares. moreover, there is a clear lack of consensus on the level of protection required for different specialities of medical and dental professionals who are in contact with potential disease carriers. here, we provide a comprehensive review on the different type of facial covers, including masks, available both for the pubic and the health professionals. notably, we discuss the anatomy, and the critical issues of disinfection and reusability of masks, the alternative equipment available for the protection of the facial region from airborne diseases, such as face shields and powered air purifying respirators (papr). the review concludes with the skin-health impact of prolonged wearing of facial protection, by health care workers. understanding the different types of masks can initially be intimidating due to their diversity and confusing terminology. this is complicated by the regional differences in regulations and standards. nevertheless, most authorities divide masks into three tiers: respirator masks, surgical masks, and single-use face masks. the first tier in the classification of masks comprises the respirator masks. they have the highest filtering capacity of the three tiers. respirator masks are designed to filter over 90% of virussized pollutant particles in the air, and are tightly fitted onto the face of the wearer. they require fit testing to ensure proper adaptation to the face. in the u.s., respirator masks, so called n95 masks are certified by the national institute for this article is protected by copyright. all rights reserved currently, the u.s. centres for disease control and prevention (cdc) does not recommend the use of respirator masks for non-healthcare providers, as these are critical supplies that should be reserved for those at the highest risk of infection (u.s. food and drug administration, 2020). respirator masks are designed for single use only, and ideally should be changed after every patient encounter. because of the tight fit and high filtering capacity, the wearer of respirator masks might experience shortness of breath and discomfort after prolonged use. the next tier in the classification of facial masks is the surgical mask. these are loosely fitted masks that do not require fit testing, and are routinely used in the healthcare setting when the procedures do not generate a significant amount of aerosol, and when the risk of acquisition of airborne transmissible diseases is low to moderate. surgical masks are commonly referred as "face masks". however, not all face masks qualify as surgical masks due to the regulatory guidelines in the u.s., to be considered as surgical masks they have to be certified by the astm international (previously known as american society for testing and materials) standards authority. in europe, the surgical masks are certified using the european standards organisation (en). based on their filtration efficacy, surgical masks are classified into levels 1, 2 and 3 in the u.s. system. level 3 surgical masks have the highest filtration efficacy compared to their counterparts, with an ability to filter over 98% of particles of 3.0 microns, and a maximum level of fluid resistance. on the other hand, the european system classifies surgical masks into type i-iii, with the filtration capability similar to their us. counterparts. surgical masks offer protection against droplets from direct spatter, but do not effectively filter small particles. surgical masks, unlike respirator masks are not tightly fitted around the face, and due to this loose fit they do not protect against leakage from the lateral aspects of the masks. therefore, the niosh does not recommend that surgical masks be used as particulate respirators (u.s. national institute for occupational safety and health, 2018). nevertheless, surgical masks might be effective in blocking splashes, sprays, and large respiratory droplets during routine medical or surgical procedures. community-wide use of surgical masks remains a controversial topic in the setting of the ongoing covid-19 pandemic. on the one hand, the world health organization issued an interim report on april 6, 2020, stating that the evidence is lacking for the prevention of the acquisition of covid-19 virus in healthy persons (world health organization, 2020). however, it is now generally this article is protected by copyright. all rights reserved accepted that universal mask wearing might be beneficial with regards to source control, as they are likely help prevent the direct projectile of virus-containing respiratory droplets and aerosols from infected individuals. in a recent study using model simulations, it was suggested that the broad adoption of masks by the general public could be effective in reducing the community transmission of covid-19, thus lessening the burden on the healthcare system (eikenberry et al., 2020) . the authors concluded that the effect would potentially be greatest when the compliance of mask wearing is high, and when it is combined with other measures such as social distancing. in another study by cheng et al., the authors compared the incidence of covid-19 in hong kong special administrative region (hksar) where the compliance of face mask usage by the general public was 96.6%, to that of other "non-mask-wearing" countries with similar population density healthcare systems and social distancing measures. it was found that the incidence of covid-19 within the first 100 days was significantly lower in hksar than that of non-maskwearing regions. the authors concluded that universal mask-wearing might help reduce covid-19 burden by containing the emission of infected saliva and respiratory droplets from the mildly infected individuals, or those who are asymptomatic (v. c. . single-use face masks do not meet the requirements of surgical masks. the construction of single-use face masks varies, but are typically thin and might consist of only a single layer. single-use face masks are not normally used in the healthcare setting, if the supply of surgical masks is not a concern. although single-use face masks generally cannot filter very small particles, they might still be able to block the emission of large droplets and saliva fairly well. moreover, when the supply of surgical masks and respirator masks are limited even for healthcare workers (hcw), single-use face masks might be a realistic alternative to be used in the community setting. due to the acute shortage of surgical masks and n95 respirators, some jurisdictions discourage their use by the general public and reserve them for those at the highest risk for viral exposure, such as hcw who are in close contact with infected patients. a recent recommendation by the cdc issued in april 2020 encouraged the use of cloth face coverings in public settings to slow the spread of covid-19 (u.s. centers for disease control and prevention, 2020). this is a seemingly sensible solution when proper masks are in critical supply. while cloth masks do not protect against aerosols, they might still play a role in minimizing the spread of the virus, especially the other recommendations are practiced, such as staying home, reducing unnecessary travel, and social distancing. cloth masks are increasingly being offered at various online shops, and many do-it-yourself versions have been suggested. a comparison of the various masks is shown in table 1 . this article is protected by copyright. all rights reserved while the construction of unregulated single-use face masks is variable, the anatomy of most surgical masks certified by either the astm or en standards are similar (figures 1 and 2 ). surgical masks are commonly made of three layers, with a filter layer placed between two layers of non-woven fabric (thomasnet, 2020). the outer layer is usually coloured and is a waterresistant layer, while the inner layer is an absorbent layer and is in contact with the skin of the wearer. the middle filter layer is most commonly made of polypropylene, made through a meltblown technology (thomasnet, 2020). surgical masks are usually pleated to allow adjustment of fit around the face of the wearer. at the top part of the surgical mask, there is an adjustable nose clip for the wearer to adjust the shape around the nasal bridge. this reduces the gap between the mask and the face and thus prevents excessive leakage from the margins of the mask. the most common means for the surgical mask to be attached to the face of the wearer are through either ear loops on either sides of the mask, or via head ties for the wearer to tie them around the head at the level above the ears and around the neck. while surgical masks with ear loops are more convenient to wear and remove, those with head ties are adjustable and might allow a tighter fit around the face of the wearer. this could mean that the amount of leakage around the margins of the mask is less in surgical masks with head ties than those with ear loops. respirator masks, such as n95 masks, are usually made of, up to four, multiple layers (thomasnet, 2020) (figure 1c ) i) comprising a non-woven layer which filters particles of 0.5 microns in diameter, ii) an activated carbon layer which filters chemicals, iii) a cotton layer which filters particles of 0.3 microns in diameter, and iv) a second non-woven layer. they might have an optional valve for regulation of breathing. similar to surgical masks, n95 masks are commonly made by melt-blown technology using polypropylene . respirator masks are then sterilized after they have been manufactured (thomasnet, 2020). the shortage of facemasks during the covid-19 pandemic has created fear and panic amongst health care workers (hcw) in particular as this essential piece of ppe has been in major short supply, leading to prolonged and repetitive wear of a single mask, and re-use of disinfected masks. although us cdc has issued guidelines stating that a facemask is considered contaminated when it is worn in managing an infected patient, and the facemask should not be reused (siegel, rhinehart, jackson, chiarello, & health care infection control practices advisory, 2007) , facemasks shortage, has led to their reuse after decontamination and disinfection in a number of jurisdictions of the world. researchers have therefore investigated the possibilities to this article is protected by copyright. all rights reserved disinfect facemasks to ease the shortage problem. the practicality of the disinfection process of a used facemask depends on the following criteria: i. all pathogens are eliminated, ii. the structure of the facemask is not damaged, iii. the function of the facemask including filter capacity is maintained, iv. no residual disinfectant that could cause health hazard. different methods of disinfection have been suggested and tested, which could be broadly categorized into heat (dry and moist), chemical or radiation treatment (cadnum et al., 2020; lore, heimbuch, brown, wander, & hinrichs, 2012) . this article is protected by copyright. all rights reserved based solutions and soaps were detrimental to n-95-like fabric respirators. these agents cased degradation of the static charge in the fabric and decreased the filtration efficiency dramatically. facemask disinfection by radiation with microwave, gamma ray or ultraviolet germicidal irradiation (uvgi) have also been tested. microwave has melted the n95 respirators in one study (viscusi et al., 2009) , while gamma ray caused significant reduction in the filtering capacity of the masks (de man et al., 2020). both techniques were therefore not recommended. appropriate frequency ultra violet was found to have no effect on the facemasks filter capacity (viscusi et al., 2009 ), but a study found residual viruses in two of the six samples when tested by droplet inoculation of h1n1 viruses (heimbuch et al., 2011) . what is the best method to disinfect masks? this is a question that lacks clear-cut answers. however, considering a balance between decontamination and potential material damage, it appears that non-chemical approaches are preferable ( the extremely contagious nature of pandemic viral diseases such as covid-19 mandate precautions with necessary protective equipment, not only for hcw but also the general public. that said, there is also a worldwide shortage of masks, specifically those such as the n95 filtering facepiece respirators (ffr). this implies resorting to other mask types, especially those with reusable potential. furthermore, the increasing time of usage results on significant resistance to breathing, owing to the build-up of moisture. these caveats raise the question: can masks be reused? if so, the acceptable frequency of repetitive disinfection, and the type of masks that withstand such chemical assault are key questions that need to be resolved. additionally, there is evidence to show that sars-cov and sars-cov-2 can survive on plastic surfaces for up to 72 hours (van doremalen et al., 2020) . the exact duration of their survival on ffrs or other conventional masks remains unknown. nevertheless, the possibility of "selfthis article is protected by copyright. all rights reserved contamination" through repeated use of masks cannot be overruled. therefore, in terms of masks reusability, the following critical questions must be answered: can these masks be sterilized? what is the optimal mode of sterilization such that it kills the viruses but does not affect the properties of the mask? if so, how many times can they be sterilized? as discussed in the previous section, although research in this area is nascent, much more work regarding disinfection of masks need to be done in order to answer these questions. the next section explores the masks and face shields that are designed to be reusable. as early as 2006, the national academy of sciences, usa suggested that it may be better to stock reusable respirators than n95 respirators (the national academy of sciences, 2006) . such reusable respirators contain face pieces that can be cleaned and reused, while the exact nature of reusability of the filter cartridge remains unknown (weiss, weiss, weiss, & weiss, 2007) . recently the government of hong kong sar distributed reusable face masks (cumask+) to its residents. this six-layered, copper-infused mask is claimed to prevent the colonization/immobilization of bacteria and viruses. this mask, which satisfies the american society for testing and materials (astm) f2100 level 1 standard for particle filtration efficiency (pfe), bacterial filtration efficiency (bfe) and resistance to penetration by synthetic blood. it has also been claimed that this mask was effective up to 60 washes. however, it remains unclear if the efficacy to preventing the novel sars-cov-2 is retained up to 60 washes. in a recently published proof-of-concept study, the authors proposed in interesting approach towards 3d printing of custom-made face mask, with discrete manufacturing approaches for the reusable and disposable components (swennen, pottel, & haers, 2020) . although leakage and virologic testing of these masks have not been performed at the time of publication, 3d-printed face masks appear to be an interesting solution to the current short supply of ppe. however, the reusability of these protective devices remains unknown, as yet. as mentioned previously, wearing of cloth masks might be an alternative solution when proper masks are in short supply. however, cloth masks wearing is still a controversial topic due to concerns about reusability and proper disinfection. a practical approach to decontamination of cloth masks is to use steam under pressure. such an approach was proposed and is used commonly in taiwan, where, cloth masks are decontaminated using short cycles (about 20 minutes) of heating under pressure in a steam/rice cooker. as discussed above, moist heat disinfection of cloth masks significantly reduces the level of bacteriophage ms2 and methicillin this article is protected by copyright. all rights reserved resistant staphylococcus aureus (li et al., 2020) . however, the effects of moist heat on the sars-cov-2 on cloth masks is still unknown. whether all the mask types can achieve a balance between filtration efficiency and material integrity after repeated use and disinfection remains a conjecture, as yet. considering that we are on the verge of further impending epidemics and pandemics, scientists should be prudent in proactively developing masks that have reusable potential. a face shield, worn as an additional barrier in front of a face mask during medical and surgical procedures, is an adjunctive personal protective equipment (ppe) available to hcws (figure 3) . the purpose of a face shield, that usually consists of a clear plastic material, is to protect the mucous membrane of the face (eyes, nose and mouth) from direct splashing, spraying and spatter of blood, saliva, other contaminated bodily fluids and materials, and irrigation fluids during patient treatment. because most face shields do not form a tight seal around the side of the face and chin area, they do not offer protection against aerosols leaking in from the margins of the face shields. also, face shields might be subject to glare and fogging (roberge, 2016) . in fact, strong evidence is lacking in terms of the effectiveness of face shields against the transmission of viral respiratory diseases (the national academy of sciences, 2010). considering the above reasons, they are considered an adjunct, and should be used with other ppe, such as masks, and head caps. despite some of the disadvantages of face shields, many authors recommend the use of face shields, especially during the current pandemic, when ppe is in short supply (advani, smith, lewis, anderson, & sexton, 2020; garcia godoy et al., 2020; perencevich, diekema, & edmond, 2020) . face shields are robust, durable, easy to disinfect, and can be reused indefinitely in theory. also, they are easy to manufacture, and no specific materials are required other than a clear material which is easy to acquire. additionally, wearing of face shields does not jeopardize interpersonal communication: lip reading and interpretation of facial expressions are still possible. this is particularly important for those with hearing disabilities. during aerosol generating procedures, the cdc recommends that the care provider should wear either: i) a mask and eye googles, ii) a mask with attached face shield, or iii) a face shield that fully covers the front and sides of the face (centers for disease control and prevention, 2019). the american dental association (ada) also recommends wearing of face shields by dental this article is protected by copyright. all rights reserved health-care personnel (dhcp) when treating patients (american dental association, 2020). because it is assumed that even asymptomatic patients can transmit disease, the highest level of ppe available should be used (american dental association, 2020) . this includes wearing face shields or goggles in addition to the different types of masks (american dental association, 2020). aerosol-generating procedures (agps) are intrinsic to the routine practice of dentistry. while n95 respirators manage to filter at least 95% of particles <5m in size, fit tests are required to ensure the masks fit properly on the user by measuring air leakage. occasionally, individuals fail the fit tests and are deemed not suitable for wearing n95 respirators, or in situations like hcws working long hours and/or when the heavy growth of the facial air (e.g. beards, moustaches) impedes the mask fit and integrity (mcmahon, wada, & dufresne, 2008) . additionally, prolonged wearing of n95 respirators are also known to be uncomfortable because of the increased breathing resistance, and heat and moisture build-up (roberts, 2014) . hence powered air-purifying respirators (papr) have been suggested as a solution to alleviate the foregoing issues. papr is a battery-powered blower that provides positive airflow through a filter, cartridge, or canister to a hood or face piece (figure 4) . when compared to most facemasks, papr may offers additional protection. one study has shown that a properly used papr offered up to an assigned protection factor (apf) of 1000 when compared to apf of 10 for a n95 respirator (centers for disease control and prevention, 2018) . the air is filtered by high-efficiency particulate air (hepa) filter or p100 filters, which are both effective in filtering 99.97% of particle size 0.3m in diameter (bollinger, 2005) . papr is considered to be the alternative when an individual fails an n95 fitting test. it is also suggested to be used in high risk environments like managing patients with airborne diseases or high risks aerosol generating procedures (howard, 2020) . papr is also more comfortable than wearing n95 masks especially those working for long hours with physical exertions such as nurses and orthopaedic surgeons (powell, kim, & roberge, 2017 ). there are several drawbacks of using papr on top of its higher cost compared to other facial protection equipment. there are specific guidelines in donning and doffing a papr to avoid contamination, which require extra training and time (the national academy of sciences, 2015). some designs of papr, such as those with a loose-fitting hood, inhibit the use of headlight or this article is protected by copyright. all rights reserved loupes during dental procedures. the constant, noise generated by the air-purifier is also an irritant to the patient as well as the hcws especially in a dental clinic setting. the clinicians and the supporting staff, therefore, need to assess the risks/benefits carefully when deciding the necessity of using papr in the dental clinic. the covid-19 pandemic has clearly spotlighted the facial skin damage due to the prolonged use dermatological issues are also possible with custom-made 3d-printed masks, prolonged application of these masks may result in allergic and decubitus lesions at the nasal bridge. this is likely to be specifically amplified in hcw who work in virology units that are humid and warm. while adjustments of non-invasive ventilation devices are fairly easy to perform and hence prevent such ulcerations, such adjustments on protective respirators are not possible. one suggestion to mitigate this problem is to use protective hydrocolloid dressings over the nasal bridge (payne, 2020). in addition, the routine use of skin unguents may mitigate such damage, although there are no clear guidelines on the frequency of such usage. tensions and contradictions that surround the current pandemic ridden world include the availability, and the lack thereof, various facial protection measures to mitigate the viral spread. here, we comprehensively explore the different type of facial protection measures available to the public and the health care workers. we discuss the anatomy, the critical issues of disinfection and reusability of masks, the alternates available, such as face shields, cloth masks, and powered air purifying respirators (papr), and the skin-health impact of prolonged wearing of facial protection. evidence favor the widespread use of some form of face covering minimizes the community spread of covid-19. ideally, surgical masks and n95 respirators must be discarded after a single this article is protected by copyright. all rights reserved . this article is protected by copyright. all rights reserved showing a snugly fitting, air tight, head piece with a transparent plastic lining in front, connected through a (detachable) plastic tube to the power unit. the power unit has a replaceable air filter, and a motor which creates a positive pressure ventilation system with filtered air. universal masking in hospitals in the covid-19 era: is it time to consider shielding? interim mask and face shield guidelines niosh respirator selection logic effectiveness of ultraviolet-c light and a high-level disinfection cabinet for decontamination of n95 centers for disease control and prevention. a guide to air-purifying respirators. dhhs (niosh) publication no the role of community-wide wearing of face mask for control of coronavirus disease 2019 (covid-19) epidemic due to sars-cov-2 disinfection of n95 respirators by ionized hydrogen peroxide during pandemic coronavirus disease 2019 (covid-19) due to sars-cov-2 sterilization of disposable face masks by means of standardized dry and steam sterilization processes; an alternative in the fight against mask shortages due to covid-19 to mask or not to mask: modeling the potential for face mask use by the general public to curtail the covid-19 pandemic national pressure ulcer advisory panel (npuap), pan pacific pressure injury alliance (pppia) facial protection for healthcare workers during pandemics: a scoping review accepted article this article is protected by copyright. all rights reserved powered air-purifying respirator use in healthcare: effects on thermal sensations and comfort face shields for infection control: a review to papr or not to papr? essential microbiology for dentistry guideline for isolation precautions: preventing transmission of infectious agents in health care settings custom-made 3d-printed face masks in case of pandemic crisis situations with a lack of commercially available ffp2/3 masks the national academy of sciences: board on health sciences policy, institute of medicine. the use and effectiveness of powered air purifying respirators in health care: workshop summary the national academy of sciences: committee on the development of reusable facemasks for use during an influenza pandemic. reusability of face-masks during an influenza pandemic: facing the flu preventing transmission of pandemic influenza and other viral respiratory diseases. personal protective equipment for healthcare workers: update how surgical masks are made how to make n95 masks? isolation precautions recommendation regarding the use of cloth face coverings, especially in areas of significant community-based transmission accepted article this article is protected by copyright. all rights reserved u.s. food and drug administration respirator trusted-source information: ancillary respirator information aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 evaluation of five decontamination methods for filtering facepiece respirators disrupting the transmission of influenza a: face masks and ultraviolet light as control measures advice on the use of masks in the context of covid-19. interim guidance this article is protected by copyright. all rights reserved accepted article key: cord-298227-av1ev8ta authors: kähler, christian j.; hain, rainer title: fundamental protective mechanisms of face masks against droplet infections date: 2020-06-28 journal: j aerosol sci doi: 10.1016/j.jaerosci.2020.105617 sha: doc_id: 298227 cord_uid: av1ev8ta many governments have instructed the population to wear simple mouth-and-nose covers or surgical face masks to protect themselves from droplet infection with the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) in public. however, the basic protection mechanisms and benefits of these masks remain controversial. therefore, the aim of this work is to show from a fluid physics point of view under which circumstances these masks can protect against droplet infection. first of all, we show that the masks protect people in the surrounding area quite well, since the flow resistance of the face masks effectively prevents the spread of exhaled air, e.g. when breathing, speaking, singing, coughing and sneezing. secondly, we provide visual evidence that typical household materials used by the population to make masks do not provide highly efficient protection against respirable particles and droplets with a diameter of 0.3–2 μm as they pass through the materials largely unfiltered. according to our tests, only vacuum cleaner bags with fine dust filters show a comparable or even better filtering effect than commercial particle filtering ffp2/n95/kn95 half masks. thirdly, we show that even simple mouth-and-nose covers made of good filter material cannot reliably protect against droplet infection in contaminated ambient air, since most of the air flows through gaps at the edge of the masks. only a close-fitting, particle-filtering respirator without an outlet valve offers good self-protection and protection against droplet infection. nevertheless, wearing simple homemade or surgical face masks in public is highly recommended if no particle filtrating respiratory mask is available. firstly, because they protect against habitual contact of the face with the hands and thus serve as self-protection against contact infection. secondly, because the flow resistance of the masks ensures that the air stays close to the head when breathing, speaking, singing, coughing and sneezing, thus protecting other people if they have sufficient distance from each other. however, if the distance rules cannot be observed and the risk of inhalation-based infection becomes high because many people in the vicinity are infectious and the air exchange rate is small, improved filtration efficiency masks are needed, to take full advantage of the three fundamental protective mechanisms these masks provide. at present, humanity is threatened by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) pandemic. the risk of severe infection with the virus depends heavily on physical factors of the infected persons and the quality of the medical system. according to a recent study the estimated infection fatality ratio (ifr), averaged over all age-groups including those who don't have symptoms, is between 0.2% -1.6% with an average of 0.66% (verity et al., 2020) . these numbers look small, and the fatality risk may seem acceptable, and therefore the danger is often marginalized. this is surprising considering that the apollo crew, the space shuttle astronauts and the allied soldiers during the 2003 iraq war took a deadly risk of this magnitude. only very few people take such risks voluntarily and with full consciousness. for comparison, the lethal risk of a fatal accident with a commercial aircraft was 1:7700000 in 2008 and even such a small risk is not taken by some people. considering that the ifr of the seasonal flu is about 0.04 -0.1% (centers for disease, 2010) or even much lower (wong et al. 2013 ) the mortality rate of sars-cov-2 appears to be significantly higher than for influenza flu. although the numbers for sars-cov-2 are quite preliminary and the estimates may drop over time (verity et al., 2020 , faust, et al., 2020 it is quite clear that the strategy of herd immunization of the population is not an option, as the number of victims would be far too high. great hopes for coping with the pandemic currently rest on the development of a vaccine. unfortunately, it is completely uncertain when an effective and well-tolerated vaccine will be generally available to contain the pandemic. drugs such as chloroquine, remdesivir, lopinavir and ritonavir are also considered to be great sources of hope in the fight against the coronavirus disease 2019 (grein at al., 2020) . however, even if one of the drugs should prove to be effective, there is no guarantee that the drug can be made available to the world population in sufficient quantities. in addition, it is possible that, despite the use of drugs, going through a severe course of disease can lead to lifelong neuropsychiatric sequelae (troyer et al., 2020 and zandifar & badrfam, 2020) or cause other diseases (ackermann et al., 2020 and varga et al., 2020) . containing the pandemic is therefore the only viable way to quench the spread of the virus. but containing the pandemic is a difficult task as about 44% of sars-cov-2 infections are caused by people with a presymptomatic and asymptomatic course of infection (he et al., 2020) . therefore, due to the absence of symptoms, many people do not know that they are infected and are spreading the virus and these people make it very difficult to trace the transmission chains. furthermore, about 10% of infected people are responsible for 80% of infections (kupferschmidt, 2020 and lloyd-smith et al., 2005) . people who have many social contacts at work or in their private lives and who do not protect themselves and others sufficiently by observing the rules of distance and hygiene, or who consider the risk of the virus to be low, appear to be a serious problem in the actual pandemic. for these reasons, the government must act at various levels to avert great harm to the population. the effectiveness of the containment strategy depends on 1. how societies are able to protect themselves personally against infection through hygiene, social distance and technical aids such as protective masks, glasses, gloves, 2. how well the infrastructure is in place to identify the infection chains and effectively contain the spread, e.g. through mobile data collection, isolation or a lockdown, 3. how well the seriously ill can be treated in hospitals. in view of these prospects, it seems necessary for the time being to prevent the spread of the virus and to treat those infected as well as possible. in order to ensure the latter, the capacities of the health system must not be overloaded. but it is clear that this condition means that the pandemic will last for years without a vaccine. to not overload the medical system, governments are pursuing the concept of containment by means of a lockdown because it proved successful in st. louis during the spanish flu of 1918. this approach is quite effective when the population obeys the rules, but the impact on the state, economy and society is devastating when the lockdown lasts longer than a few weeks. therefore, this concept is not a viable way to contain the pandemic in the long term. consequently, it is necessary to fight the infection where it occurs. understanding the transmission pathways is the key to finding effective measures to block the infection and to reliably protect healthcare workers and the population. contact infection were initially assumed to be the main transmission route of sars-cov-2. today, hygiene measures and the avoidance of shaking hands effectively prevent this path of infection. droplet infection is currently assumed to be the main transmission route over short distances . since this path of infection is via the air, the rules of distance are effective (soper, 1919 and wells et al., 1936) . but it is also known that sars-cov-2 can remain infectious in aerosols for more than 3 hours, at least under laboratory conditions at high humidity (van doremalen et al., 2020 and pyankov et al., 2018) . it is therefore conceivable that infections can also occur under special conditions over long distances, provided that the local virus concentration reaches the minimum infection dose due to poor air exchange in rooms. a significant proportion of the aerosol exhaled by humans has a diameter of less than 10 μm (johnson et al., 2011) when breathing, speaking, singing and coughing. it is also known that the size and number of droplets increases with the volume of the voice (asadi et al. 2019 and loudon & roberts, 1968) and it is known that upper respiratory tract diseases increase the production of aerosol particles (lee et al., 2019) . water droplets of this size evaporate within a few seconds at normal humidity (liu et al. 2014 and rensink 2004) . droplets with a diameter of 10 μm for instance are evaporated after about 1 s at 50% relative humidity and larger droplets sink quickly to the ground and evaporate (marin et al., 2016 . if the viruses are released as "naked" viruses together with the salt after the droplets have evaporated, the spatial concentration decreases rapidly over time, as the viruses no longer move in a correlated manner but quickly separate due to the chaotic turbulent flow motion. the viral load thus decreases rapidly in time and space, making infections over long distances or long periods of time increasingly unlikely. for this reason it is most important to understand the transmission of the virus over short distances. hygiene regulations and social distancing are very effective in blocking short distance infections. during the lockdown, the distance rules can usually be adhered to, but what happens when the actual lockdown is over and the people meet again in a confined space? then additional effective and efficient protection is essential to stabilise infection rates. since the viruses are spread by contact and droplet infection, technical devices are required that effectively intervene in the chain of infection and effectively block infection. an effective protection is the respiratory mask as known since 100 years (soper, 1919) . the sars outbreak in hong kong suggested that the use of simple face masks may have contributed to an overall reduction in the incidence of viral respiratory infections lo et al., 2005) . another study has shown that even a simple surgical mask can effectively reduce sars infection (seto et al., 2003) . these results are supported by recent articles (leung et al., 2020b , howard et al., 2020 . it was surprizing that for months, who, the cdc and many public health professionals in europe advised against wearing face masks unless someone has covid-19 or cares for someone who has covid-19 (feng et al., 2020 and leung et al., 2020a) . this recommendation was based on three allegations. first, it was said that there is no scientific evidence that face masks can protect against droplet / aerosol infections. second, it was argued that the population will not be able to wear the masks properly. third, the statement that people will feel safe when wearing masks and then become careless and take risks was frequently made. at the same time, these experts have stressed that health professionals urgently need face masks to protect themselves effectively. this contradiction has created uncertainty among the population and called into question the credibility of the experts. it is a fact that particle filtration masks are recognized as legal occupational safety equipment and that the wearing of these masks in contaminated areas is required by labor law. there is therefore no doubt that these masks, when used correctly, provide effective protection within the specification range. the effectiveness of simple mouth-and-nose covers and surgical masks is less well accepted. the international council of nurses (icn) estimates that, on average, 7% of all confirmed cases of covid-19 are among healthcare workers (icn, 2020) . this illustrates that surgical masks may not provide the reliable protection against droplet infection, as anticipated. it is therefore very important to distinguish clearly between the different mask types when talking about their protective function. unfortunately, this was not done sufficiently by the virologists and politically responsible persons in the initial phase of the pandemic. also the second argument is questionable. why should the people of western societies not be able to protect themselves as many people in east asian countries have long been doing? many people in east asian countries have already recognized through numerous pandemics that proper masks work effectively. it does not seem right to regard the western population as unteachable or even incapable. the third argument is also false, because the opposite is true according to scientific studies (kimberly et al., 2020 , scott et al., 2007 and ruedl et al., 2012 . if people protect themselves personally, they have dealt with the danger and therefore they benefit from the protection of the safety device and from the less risky behaviour due to insight. the reason why these facts were not appreciated by the experts is due to the attempt to prevent competition for protective masks between medical personnel and the public. in the meantime, the general perception of the protective effect of face masks has become generally accepted. in the usa, the cdc has changed its guidelines and recommended that the public wear fabric face masks. in other countries, too, it is now recommended to protect themselves with suitable masks. however, it is recommended by governments and professionals to wear only simple mouse-and-nose covers that can be manufactured by the people themselves or surgical masks to avoid distribution battles with medical staff for certified and comfortable particle filtration masks. but the big question is, how effectively these homemade mouth-and-nose covers and surgical masks can protect against droplet infection. the answer is highly relevant to guide public behaviour (leung et al., 2020a) . one study suggests that a surgical face mask and masks made of dense cotton fabrics apparently cannot effectively prevent the spread of sars-cov-2 into the environment through the coughing of patients with covid-19 (bae et al., 2020) . another study suggests that any mask, no matter how efficiently it filters or how well it is sealed, has minimal effect unless used in conjunction with other preventive measures such as isolation of infected cases, immunisation, good respiratory etiquette and regular hand hygiene (kwok et al., 2015) . these findings contradict the results in , lo et al., 2005 and seto et al., 2003 . due to the contradiction, it is understandable that experts in the media have expressed the opinion that there is no scientific evidence for the effectiveness of masks and therefore the wearing of masks in public was not recommended for a long time. the fallacy of politicians and virologists, however, was to generalize the results obtained with simple mouth-and-nose covers to all masks without differentiation. in order to clarify whether or to what extent these masks offer effective protection against droplet infection and to understand why research results differ on this simple scientific question, we have carried out these tests. first, we analyse the flow blockage caused by surgical masks when coughing, as this is essential for the protection of others and because coughing is a typical symptom of covid-19. second, we qualify the effectiveness of different filter materials and masks to determine the protection ability against droplets. finally, we prove the effect of gap flows at the edge of surgical and particle filtrating respiratory masks. in contrast to the medical studies cited, we apply engineering research methods of fluid mechanics. the use of this research approach has several reasons: firstly, the detachment of droplets in the lungs and throat and their convective transport through the mouth into the atmosphere until inhalation as well as the deposit and evaporation of droplets is a purely fluid mechanical process. secondly, the effective blocking of the flow with suitable masks is a research subject of fluid mechanics. thirdly, the filtering of particles from an air stream with the aid of suitable materials is also a purely fluid mechanical problem as well as the gap flow. finally, this approach also has the advantage that the results are reproducible in a statistical sense, since the boundary conditions are well defined. we are not studying whether an infection really occurs in a special case, but whether an infection is physically possible in general. in the first sets of the experiments, outlined in section 3.1, the flow field generated by coughing without and with a surgical mask is examined as coughing sets the air strongly in motion and because coughing is a typical symptom of covid-19. to measure the flow field quantitatively in space and time we use particle image velocimetry (piv) (raffel et al., 2018) . for the measurements a 8 m long testing room with a cross section of 2 m × 2 m was seeded with dehs (di-ethyl-hexyl-sebacat) tracer particles with a mean diameter of 1 μm (kähler et al., 2003) . dehs was used as these droplets do not evaporate as quickly as water droplets. the tracer particles provided by a seeding generator (pivtec gmbh, germany) were illuminated in a light-sheet generated with a frequency doubled nd:yag laser (spitlight piv 1000-15, innolas laser gmbh, germany). the light-sheet was oriented normal to the mouth opening and parallel to the symmetry axis of the body and the longitudinal axis of the room. the light scattered by the tracer particles were recorded with back illuminated scientific cmos cameras (pco.edge 5.5, pco ag, germany) equipped with zeiss distagon t* lens with a focal length of 35 mm and 50 mm. the triggering of the system components was achieved with a programmable timing unit (lavision gmbh, germany). the recorded series of images were evaluated with a commercial computer program (davis, lavision gmbh, germany). these quantitative piv measurements allow to determine the area that can be contaminated due to the exhaled air, the velocity of the exhaled droplets and the turbulence properties of the flow. in the second set of experiments, discussed in section 3.2, common household materials currently used by the population and some medical staff to make simple masks at home were tested but also a surgical mask and a ffp3 mask to visualize their filtering properties. the tested materials are given in table 1 . for the investigation, a test set-up was installed which largely fulfilled the officially prescribed test conditions in europe (din en 149). the materials were installed one after the other in a fixed position in front of the inlet of a rectangular flow channel with a cross-section of 0.1 m × 0.1 m, as shown in fig. 1 . the material was held in place with a special clamping device that seals tightly to the duct to avoid leakage flows. to explore the filtering performance of the different materials the movement of small aerosol droplets passing through the media was observed visually in front of and behind the filter material with a digital camera. we only use droplets whose diameter is less than 2 μm, since the removal of the smallest droplets in an air stream is the greatest challenge in mask development. if these droplets can be effectively filtered out effectively, then all droplets larger than 2 μm can also be filtered. the droplets were generated from dehs with an aerosol generator (agf 2.0, palas gmbh). dehs was used again as these droplets are long lasting. consequently, bias errors due to evaporation effects can be neglected. a nd:yag double-pulse laser (evergreen 200, quantel, france) was used to illuminate the droplets. the output beam was fanned out with a few lenses to form a 1 mm thin light-sheet. the light-sheet was located in the middle of the flow channel parallel to the flow direction as indicated in fig. 1 . the scattered light emitted by the illuminated aerosol in the light-sheet plane was recorded with a highly sensitive pco edge 5.5 scmos camera equipped with a zeiss distagon t* lens with a focal length of 50 mm. the triggering of the system components and the data recording was realized again with the software davis from lavision. the flow velocity was driven by the pressure difference between the atmosphere and the flow box. the flow rate through the filter material was adjusted approximately according to the din en 149 test standard (90 liter/minute). the volume flow rate and the movement of the droplets through the filter material was measured optically with high spatial and temporal resolution using piv. to calculate the volume flow rate the average flow velocity within the light-sheet plane in the flow channel was measured and it was assumed that this velocity is homogeneous over the cross section of the channel. this assumption is justified as the filtering materials are homogeneous and the inflow condition is constant across the filtering material. with the know size of the cross section the volume flow rate can be calculated. the pressure drops provided in table 1 are calculated from the measured pressure drops and the volume flow rate. it is assumed that the pressure loss is proportional to the square of the volume flow rate. the pressure drop across the filter material was measured with a testo 480 (testo se & co. kg, germany) pressure transducer with an uncertainty of about 3 pa for the third set of experiments, analysed in section 3.3, simple flow visualizations using smoke were performed in order to demonstrate the effect of the gap around the mask edge. a person exhaled air seeded with tracer particles while wearing surgical and ffp2 masks. in the first series of experiments, one person performed a single severe cough while the piv system was measuring the flow field data. the video in the supplementary material shows the temporal evolution of the process. the results displayed in this subsection show instantaneous velocity fields of various independent timeresolved flow field measurements. color-coded is the magnitude of the local flow velocity and the vectors indicate the direction of the flow movement at a given time step. in areas where the flow movement remains close to zero over the whole recording time (blue colour), no droplets can penetrate as only the flow can move the particles to other areas. large droplets with a diameter of one millimetre or more, such as those produced when sneezing (lok, 2016) , can fly ballistic over long distances, and occasionally ballistic flying droplets are produced when certain sounds are spoken. but sneezing is not a typical covid-10 symptom so that this will not we considered here. the small droplets that are normally produced when breathing, speaking, singing and coughing are immediately slowed down and then move with the flow velocity of the ambient air. it is therefore important to study the air set in motion by exhalation. furthermore, the small droplets are particularly dangerous because they can be inhaled deep into the lungs. figure 2a shows that the spread of the exhaled air forms a cone like shape similar to a free turbulent jet (see video). the flow velocity is reaching values up to 1 m/s near the mouth, but due to the widening of the cone caused by the turbulent mixing and entrainment (reuther et al., 2020) the flow velocity decreases in streamwise direction. the widening of the area in motion reduces the viral load significantly with distance. a single strong cough sets the air in motion over a distance of less than 1.5 m in the experiments. distances of more than 1.5 m can be considered safe according to these results, since no droplets can reach such large distances when accelerated by a single cough. however, if the cough lasts longer, greater distances can be achieved, as shown in fig. 2b . for this reason, it is important to dynamically increase the distance to a person if the coughing stimulus is about to last longer. the results in fig. 2c illustrate how the spread of the airflow from the mouth during coughing is very effectively inhibited by a surgical mask. physically the mask ensures that the directional jet like air movement with high exit velocity from the mouth is converted into an undirected air movement with low velocity behind the mask. this is because the exhaled air increases the pressure inside the mask compared to the atmosphere outside, and the pressure difference creates a flow movement in all directions. this effect is of utmost importance for limiting the virus load in the environment. the results show that even a simple mouth-and-nose cover or a surgical mask can effectively protect other people in the vicinity because the mask prevents the droplets from spreading over a wide area. a simple mask with sufficient flow resistance therefore provides very effective protection for people 1 m 1 m 0.3 m 0.3 m in the surrounding area when infected and wearing the mask. wearing a mask is therefore absolutely useful to protect others according to our quantitative measurements. figure 2d shows the spread of exhaled air when speaking. it can be clearly seen that a greater spread of the exhaled air appears than when coughing with a mask. consequently, wearing a mask during normal face-to-face conversations and of course also when talking on the smartphone in a human environment is extremely useful to stop the transmission of the sars-cov-2 infection via droplets. it must also be taken into account that persons with a presymptomatic or asymptomatic course of infection will infect other persons most likely during face-toface conversations. a mask will therefore make an effective contribution to suppressing this significant path of infection. in this section we want to find out if the material of simple mouth-and-nose covers, surgical masks and ffp3 masks can protect the user from droplet infection, if the surrounding air is contaminated with sars-cov-2. in this case, the mask material must have good filtering properties to stop small droplets that typically occur when speaking, singing and coughing. since large droplets are easily filtered out by simple materials, we focus on small droplets in the range between 0.3 and 2 μm because they are produced in large fractions when speaking, singing and coughing and they can penetrate deep into the lungs. the droplets were distributed approx. 400 mm in front of the filter materials. in order to make the motion of the droplets and the filtering ability of the materials clearly visible an inhomogeneous droplet distribution was generated. the flow direction is from left to right and the flow state of the incoming air is laminar. if the intensity of the scattered light emanating from the droplets is large in front of the filter material (left image) and close to zero behind the filter material (right image), the droplets are almost completely filtered out through the material. if, on the other hand, no significant reduction in intensity can be detected behind the filter material, the filter effect is negligible. the area of the filter mount and the channel edges are not shown in the following images, since no relevant flow and droplet information is visible in these areas. the results presented are qualitative, but intended to be this way to provide readers with visual evidence of the particle penetration through different candidate filter media. a better impression of the filter efficiency is obtained by viewing the second video in the supplementary material. the comparison of the two pictures in fig. 3 (left) shows that almost all droplets pass the tested surgical face mask unhindered. consequently, this mask does not provide serious self protection against droplet infection. only a mixing of the droplet distribution takes place due to the porosity of the filter material. it is fatal that medical personnel are often so poorly protected by these masks. but it is also fatal for patients if clinical staff with a presymptomatic or asymptomatic course of infection uses these masks. even worse than the surgical face masks is the hygiene mask, see fig. 3 (right). this mask is designed for catching larger objects such as hair and spook, but tiny droplets, such as those produced when talking, singing and coughing, cannot be filtered out of the air stream by the hygiene mask. it should also be noted that the flow resistance of the hygiene mask is so low that even the protective mechanism described in subsection 3.1 does not function effectively. figure 4 reveals the effectiveness of particle filtering with toilet paper with 4 layers, paper towel, coffee filters, and microfibre cloth which also offer no serious protection against droplets in this size range. only very large droplets are retained by these materials and therefore these materials are suitable for their intended use, but not as filter material for small droplets. it is therefore strongly discouraged to make masks from these materials with the aim of protecting oneself from infection. furthermore, a very strong fleece was tested, which serves as a protective coating on ironing boards. the material is 4 mm thick, completely opaque and has a pressure drop of about 35 pa. however, a filter effect is not visible, as indicated in fig. 5 (left) . the droplet clouds flow almost unfiltered through the fleece. even several layers of a dense fabric do not have a proper filtering effect on the considered droplet sizes, which escape mainly when breathing, speaking, singing and coughing. good results could only be achieved with the material of a vacuum cleaner bag with fine dust filter properties, see fig. 5 (right) . despite the small droplets used in these tests, almost all droplets are reliably filtered out. consequently, also no larger droplets will be able to pass through the material. according to the manufacturer swirl, the material filters 99.9% of fine dust down to 0.3 μm diameter. this vacuum cleaner bag with fine dust filter therefore has better filtering properties than all tested materials and masks and even an ffp2 protective mask has poorer filtering properties, as it only has to filter out 94% of the fine dust down to 0.6 μm to meet the specifications (uvex, 2020). the material of vacuum cleaner bags with fine dust protection is therefore very well suited as a self-protecting mask if only the filter effect is considered. however, because vacuum cleaner bags are not certified clinical products, they may contain unhealthy ingredients that kill bacteria and harmful fibers that may leak from the bag material. it is therefore uncertain whether this material is suitable in practice as a material for a respirator mask. figure 6 (left) illustrates the filtering capabilities of an ffp3 mask under the test conditions. nearly all droplets are filtered out as expected. therefore, this mask type is very well suited to protect people from an infection by means of aerosols even when the environment is strongly contaminated with infectious droplets. recently, some hospitals in the usa make use of halyard h600 material to protect their employers from aerosol infection. the test result of the material is displayed in fig. 6 (right). it is clearly visible that the filtering capacity of the material is not sufficient to protect people from infection by aerosols if the environment is contaminated with the sars-cov-2. figure 7 shows with different resolution microscopic images of the halyard h600 material. it is composed to fibers but the density might not be sufficient to filter the particles used in our investigation. there are also tiny holes in the pockets visible, which could be the reason why the aerosol passes through the material, as the flow resistance at the holes is low compared to the other parts of the material. the flow tests clearly show that apart from the vacuum cleaner bag and the ffp3 mask, the filter effect of the tested materials is not sufficient to protect against droplet infection reliably if the environment is contaminated with sars-cov-2. even masks routinely used by medical staff in hospitals and doctor's offices have almost no significant filtering effect on the droplet sizes typically produced when breathing, speaking, singing and coughing. the results are therefore in good agreement with the results from (leung et al., 2020b and davies et al., 2013 and kwok et al., 2015 . but why has wearing these masks been shown to provide effective protection against infection with the virus in the sars epidemic, as shown in , lo et al., 2005 and seto et al., 2003 ? because a mask is important not only because of its filtering ability, but to limit the droplet propagation as discussed in section 3.1. so in combination with distances these mask can protect if only a few people are infected in the surrounding. the results in (leung et al., 2020b and bae et al., 2020) are correct, but they do not consider the full performance of masks, but only a partial aspect. therefore, the conclusions in the articles are not universal. the findings in and lo et al., 2005 and seto et al., 2003 are understandable when the full performance of masks in blocking infections is considered. unfortunately, wearing a simple mouth-and-nose cover may be less comfortable than wearing a particle filtering face mask. in effect, this can promote a smear infection. since all these transmissions of infection are possible in daily life, wearing a comfortable mask is essential to block human-to-human transmission by smear and droplet infection. to ensure the best possible protection, a particle filtering mask should be used if the number of infected persons in the environment and the viral load in the room is unknown. at present, social distancing practices and universal masking wearing seem to be the best methods of containing viral pandemic without stricter lockdown policies and without vaccines. some recent studies show that even the simple materials we have tested have some filtering ability (davies et al., 2013 , drewnick, 2020 , konda et al., 2020 and van der sande et al., 2008 , we do not question these results, although the pressure drops in one study is anomalously low (see supporting information in konda et al., 2020) , but we state explicitly that a material that does not have an adequate filtering ability equivalent to an ffp2/n95/kn95 mask cannot be recommended as a filter material for self-protection against droplet infection. statistically speaking, every loss of performance leads to an increase in the number of infected people and thus to an increase in the number of death. it is therefore very dangerous to recommend materials with some filtering properties as possible materials for self-protection masks. but there is another important aspect that will be discussed next. according to the previous section one might argue that a mouth-and-nose cover or surgical mask made of a good filter material would provide good protection against infection when infected people are in the vicinity or the room is contaminated with viruses. but that will not usually be the case. air takes the path of least resistance. as these masks do not seal tightly enough with the face, droplets can flow unhindered past the edge of the mask when inhaled and exhaled and reach the lungs or the environment. if the mask does not fit properly, this will even be the rule. this is illustrated in fig. 8 were a person is exhaling air during an easy exhalation without physical exertion (left), strong breathing during physical exertion (middle) and when coughing (right). the first video in the supplementary material shows the animated sequences. the analysis shows that it is very important do differentiate between mouth-and-nose cover, surgical mask and particle filtering respirator mask because they differ substantial in their fundamental protection properties. face masks can offer three fundamental different kind of protection: 1. they effectively prevents a smear infection, as the wearers of the masks no longer perform their habitual grip on the face and thus no longer bring the virus from the hand into the mouth or nose (howard et al., 2020) . 2. the flow resistance of the mask greatly limits the spread of viruses in the room. this significantly reduces the risk of infection in the vicinity of an infected person (protection of third parties). 3. the inhalation of droplets containing viruses can be prevented by using a tight-fitting mask with particle filtering properties (self-protection). the first fundamental protection mechanism can be reached by all face masks if they fit well and sit comfortably. if not, the user will touch the face even more than usual to correct the fit of the mask. as this can increase the risk of smear infection, a good fit of the mask is very important. the first and second fundamental protection mechanisms are fulfilled by all masks that have sufficient flow resistance. if the mask is worn and a candle can easily be blown out despite the mask, the mask does not fulfil this function and should not be used. all three fundamental protection mechanisms can be only achieved with ffp2/n95/kn95 or better particle filtering respirator mask. typical materials currently used by the public to build masks reduce the risk of smear infection and effectively prevent the widespread spread of viruses in the environment. therefore, the use of these mouse-and-nose covers and surgical masks are very important to prevent smear infection and droplet infection to others if the distance is not too close. as these masks do not have a significant particle-filtering protective effect against droplets that are typically produced when breathing, speaking, singing, coughing and sneezing they should not be used if the environment is contaminated, like in hospitals, even when the distance rules are followed. to achieve effective self-protection in a virus-contaminated environment, masks with particle filtering properties (ffp2/n95/kn95) are absolutely necessary from our point of view. if a large number of infected persons are present and distance rules cannot be achieved, a very good particle filtration mask (ffp3 or better) is strongly recommended. if these general rules are followed and all people use suitable particle-filtering respirators correctly, the transmission of viruses via droplets / aerosols can be effectively prevented. otherwise, these types of masks would never have received certification, nor would they be a core component of the personal protective equipment in hospitals and other environments. therefore, proper face masks can save lives while maintaining social life and securing the economy and the state. but universal masking alone is not enough for two reasons: first, many people are not very good at following rules consistently. therefore, it is advisable to observe the rules of hygiene and distance and to be careful even when wearing a mask. in the event of a car accident, the occupants are also protected by various devices (bumpers, crumple zone, safety belts, airbags, head and legroom, autonomous assistance systems, ...). second, some people are extremely bad at following rules, either because they do not want to or because they simply cannot. these people can become superspreaders. therefore, the early detection of sources of infection and their isolation remains important beside universal masking and the rules of hygiene and distance. pulmonary vascular endothelialitis, thrombosis, and angiogenesis in covid-19 aerosol emission and superemission during human speech increase with voice loudness effectiveness of surgical and cotton masks in blocking sars-cov-2: a controlled comparison in 4 patients estimates of deaths associated with seasonal influenza ---united states physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis. the lancet testing the efficacy of homemade masks: would they protect in an influenza pandemic? aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 abscheideeffizienz von mund-nasen-schutz masken, selbstgenähten gesichtsmasken und potentiellen maskenmaterialien assessment of deaths from covid-19 and from seasonal influenza rational use of face masks in the covid-19 pandemic. the lancet respiratory medicine compassionate use of remdesivir for patients with severe covid-19 temporal dynamics in viral shedding and transmissibility of covid-19 modality of human exposed aerosol size distributions generation and control of tracer particles for optical flow investigations in air universal masking in hospitals in the covid-19 era aerosol filtration efficiency of common fabrics used in respiratory cloth masks why do some covid-19 patients infect many others, whereas most don't spread the virus at all? science face touching: a frequent habit that has implications for hand hygiene quantity, size distribution, and characteristics of cough generated aerosol produced by patients with an upper respiratory tract infection the impact of community psychological responses on outbreak control for severe acute respiratory syndrome in hong kong mass masking in the covid-19 epidemic: people need guidance. the lancet respiratory virus shedding in exhaled breath and efficacy of face masks evaporation and dispersion of exhaled droplets in stratified environment superspreading and the effect of individual variation on disease emergence respiratory infections during sars outbreak where sneezes go singing and the dissemination of tuberculosis solutal marangoni flow as the cause of ring stains from drying salty colloidal drops surfactant-driven flow transitions in evaporating droplets survival of aerosolized coronavirus in the ambient air reducing transmission of sars-cov-2. science, eabc6197 particle image velocimetry verdunstung akustisch levitierter schwingender tropfen aus homogenen und heterogenen medien effect of the intermittency dynamics on single and multipoint statistics of turbulent boundary layers interfacial flows in sessile evaporating droplets of mineral water does risk compensation undo the protection of ski helmet use? professional and home-made face masks reduce exposure to respiratory infections among the general population testing the risk compensation hypothesis for safety helmets in alpine skiing and snowboarding effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (sars). the lancet the lessons of the pandemic are we facing a crashing wave of neuropsychiatric sequelae of covid-19? neuropsychiatric symptoms and potential immunologic mechanisms. brain, behavior, and immunity endothelial cell infection and endotheliitis in covid-19 estimates of the severity of coronavirus disease 2019: a model-based analysis clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in wuhan air-bone infection case fatality risk of influenza a (h1n1pdm09): a systematic review covid-19: considering the prevalence of schizophrenia in the coming decades identifying airborne transmission as the dominant route for the spread of covid-19 the authors would like to thank stefan ostmann for conducting the mask experiments presented in section 3.3 and amirabas bakhtiari for taking the microscopic images in figure 7. (www.preprints christian j. kähler (prof. dr.) and rainer hain (dr.) • a simple mouth-and-nose cover or a surgical mask is able to effectively limit the spread of air and aerosol when breathing, speaking, singing, coughing and sneezing. • wearing a mask is therefore a very useful contribution to contain a pandemic by protecting people in the vicinity from droplet infection.• however, a mouth-and-nose cover or a surgical mask does not fit tightly enough on the face to protect against droplet infection.• only a particle-filtering half-mask that fits tightly offers protection against droplet infection.• common household materials, however, do not have a sufficient filter effect to protect against droplet infection. key: cord-271822-ohkki0ke authors: verma, siddhartha; dhanak, manhar; frankenfield, john title: visualizing the effectiveness of face masks in obstructing respiratory jets date: 2020-06-01 journal: phys fluids (1994) doi: 10.1063/5.0016018 sha: doc_id: 271822 cord_uid: ohkki0ke the use of face masks in public settings has been widely recommended by public health officials during the current covid-19 pandemic. the masks help mitigate the risk of cross-infection via respiratory droplets; however, there are no specific guidelines on mask materials and designs that are most effective in minimizing droplet dispersal. while there have been prior studies on the performance of medical-grade masks, there are insufficient data on cloth-based coverings, which are being used by a vast majority of the general public. we use qualitative visualizations of emulated coughs and sneezes to examine how materialand design-choices impact the extent to which droplet-laden respiratory jets are blocked. loosely folded face masks and bandana-style coverings provide minimal stopping-capability for the smallest aerosolized respiratory droplets. well-fitted homemade masks with multiple layers of quilting fabric, and off-the-shelf cone style masks, proved to be the most effective in reducing droplet dispersal. these masks were able to curtail the speed and range of the respiratory jets significantly, albeit with some leakage through the mask material and from small gaps along the edges. importantly, uncovered emulated coughs were able to travel notably farther than the currently recommended 6-ft distancing guideline. we outline the procedure for setting up simple visualization experiments using easily available materials, which may help healthcare professionals, medical researchers, and manufacturers in assessing the effectiveness of face masks and other personal protective equipment qualitatively. infectious respiratory illnesses can exact a heavy socioeconomic toll on the most vulnerable members of our society, as has become evident from the current covid-19 pandemic. 1, 2 the disease has overwhelmed healthcare infrastructure worldwide, 3 and its high contagion rate and relatively long incubation period 4, 5 have made it difficult to trace and isolate infected individuals. current estimates indicate that about 35% of infected individuals do not display overt symptoms 6 and may contribute to the significant spread of the disease without their knowledge. in an effort to contain the unabated community spread of the disease, public health officials have recommended the implementation of various preventative measures, including social-distancing and the use of face masks in public settings. 7 the rationale behind the recommendation for using masks or other face coverings is to reduce the risk of cross-infection via the transmission of respiratory droplets from infected to healthy individuals. 8, 9 the pathogen responsible for covid-19 is found primarily in respiratory droplets that are expelled by infected individuals during coughing, sneezing, or even talking and breathing. [10] [11] [12] [13] [14] [15] apart from covid-19, respiratory droplets are also the primary means of transmission for various other viral and bacterial illnesses, such as the common cold, influenza, tuberculosis, sars (severe acute respiratory syndrome), and mers (middle east respiratory syndrome), to name a few. [16] [17] [18] [19] these pathogens are enveloped within respiratory droplets, which may land on healthy individuals and result in direct transmission, or on inanimate objects, which can lead to infection when a healthy individual comes in contact with them. 10, 18, 20, 21 in another mode of transmission, the droplets or their evaporated contents may remain suspended in the air for long periods of time if they are sufficiently small. this can lead to airborne several studies have investigated respiratory droplets produced by both healthy and infected individuals when performing various activities. the transport characteristics of these droplets can vary significantly depending on their diameter. [23] [24] [25] [26] [27] [28] the reported droplet diameters vary widely among studies available in the literature and usually lie within the range 1 μm-500 μm, 29 with a mean diameter of ∼10 μm. 30 the larger droplets (diameter >100 μm) are observed to follow ballistic trajectories under the effects of gravity and aerodynamic drag. 20, 31 intermediate-sized droplets 20,31,32 may get carried over considerable distances within a multiphase turbulent cloud. [33] [34] [35] the smallest droplets and particles (diameter < 5 μm-10 μm) may remain suspended in the air indefinitely, until they are carried away by a light breeze or ventilation airflow. 20, 32 after being expelled into the ambient environment, the respiratory droplets experience varying degrees of evaporation depending on their size, ambient humidity, and temperature. the smallest droplets may undergo complete evaporation, leaving behind a dried-out spherical mass consisting of the particulate contents (e.g., pathogens), which are referred to as "droplet nuclei." 36 these desiccated nuclei, in combination with the smallest droplets, are potent transmission sources on account of two factors: (1) they can remain suspended in the air for hours after the infected individual has left the area, potentially infecting unsuspecting individuals who come into contact with them and (2) they can penetrate deep into the airways of individuals who breathe them in, which increases the likelihood of infection even for low pathogen loads. at present, the role of droplet nuclei in the transmission of covid-19 is not known with certainty and the matter is the subject of ongoing studies. [37] [38] [39] in addition to generating microscopic droplets, the action of sneezing can expel sheet-like layers of respiratory fluids, 40 which may break apart into smaller droplets through a series of instabilities. the majority of the fluid contained within the sheet falls to the ground quickly within a short distance. regardless of their size, all droplets and nuclei expelled by infected individuals are potential carriers of pathogens. various studies have investigated the effectiveness of medical-grade face masks and other personal protective equipment (ppe) in reducing the possibility of cross-infection via these droplets. 13, 33, [41] [42] [43] [44] [45] [46] [47] notably, such respiratory barriers do not prove to be completely effective against extremely fine aerosolized particles, droplets, and nuclei. the main issue tends to be air leakage, which can result in aerosolized pathogens being dispersed and suspended in the ambient environment for long periods of time after a coughing/sneezing event has occurred. a few studies have considered the filtration efficiency of homemade masks made with different types of fabric; 48-51 however, there is no broad consensus regarding their effectiveness in minimizing disease transmission. 52, 53 nonetheless, the evidence suggests that masks and other face coverings are effective in stopping larger droplets, which, although fewer in number compared to the smaller droplets and nuclei, constitute a large fraction of the total volume of the ejected respiratory fluid. while detailed quantitative measurements are necessary for the comprehensive characterization of ppe, qualitative visualizations can be invaluable for rapid iteration in early design stages, as well as for demonstrating the proper use of such equipment. thus, one of the aims of this letter is to describe a simple setup for visualization experiments, which can be assembled using easily available materials. such setups may be helpful to healthcare professionals, medical researchers, and industrial manufacturers, for assessing the effectiveness of face masks and other protective equipment qualitatively. testing designs quickly and early on can prove to be crucial, especially in the current pandemic scenario where one of the central objectives is to reduce the severity of the anticipated resurgence of infections in the upcoming months. the visualization setup used in the current study is shown in fig. 1 and consists of a hollow manikin head which was padded on the inside to approximate the internal shape and volume of the nasal-and buccal-cavities in an adult. in case a more realistic representation is required, such a setup could include 3d-printed or silicone models of the internal airways. the manikin was mounted at a height of ∼5 ft and 8 in. to emulate respiratory jets expelled by an average human male. the circular opening representing the mouth is 0.75 in. in diameter. the pressure impulse that emulates a cough or a sneeze may be delivered via a manual pump, as shown in fig. 1 , or via other sources such as an air compressor or a pressurized air canister. the air capacity of the pump is 500 ml, which is comparable to the lower end of the total volume expelled during a cough. 54 we note that the setup here emulates a simplified representation of an actual cough, which is an extremely complex and dynamic problem. 55 we use a recreational fog/smoke machine to generate tracer particles for visualizing the expelled respiratory jets, using a liquid mixture of distilled water (4 parts) and glycerin (1 part). both the pressure-and smoke-sources were connected to the manikin using clear vinyl tubing and npt fittings wherever necessary. the resulting "fog" or "smoke" is visible in the right panel of fig. 1 and is composed of microscopic droplets of the vaporized liquid mixture. these are comparable in size to the smallest droplets expelled in a cough jet (∼1 μm-10 μm). we estimate that the fog droplets are less than 10 μm in diameter, based on stokes' law and our observation that they could remain suspended for up to 3 min in completely still air with no perceptible settling. the laser source used to generate the visualization sheet is an off-the-shelf 5 mw green laser pointer with 532 nm wavelength. a plane vertical sheet is created by passing the laser beam we first present visualization results from an emulation of an uncovered heavy cough. the spatial and temporal evolution of the resulting jet is shown in fig. 2 . the aerosolized microscopic droplets visible in the laser sheet act as tracer particles, revealing a twodimensional cross section of the conical turbulent jet. these tracers depict the fate of the smallest ejected droplets and any resulting nuclei that may form. we observed high variability in droplet dispersal patterns from one experimental run to another, which was caused by otherwise imperceptible changes in the ambient airflow. this highlights the importance of designing ventilation systems that specifically aim to minimize the possibility of cross-infection in a confined setting. 23, [56] [57] [58] despite high variability, we consistently observed jets that traveled farther than the 6-ft minimum distance proposed by the u.s. centers for disease control and prevention (cdc's). 7 in the images shown in fig. 2 , the ejected tracers were observed to travel up to 12 ft within ∼50 s. moreover, the tracer droplets remained suspended midair for up to 3 min in the quiescent environment. these observations, in combination with other recent studies, 35, 59 suggest that current social-distancing guidelines may need to be updated to account for the aerosol-based transmission of pathogens. we note that although the unobstructed turbulent jets were observed to travel up to 12 ft, a large majority of the ejected droplets will fall to the ground by this point. importantly, both the number and concentration of the droplets will decrease with increasing distance, 59 which is the fundamental rationale behind socialdistancing. we now discuss dispersal patterns observed when the mouth opening was blocked using three different types of face masks. for these results, we focus on masks that are readily accessible to the general public, which do not draw away from the supply of medical-grade masks and respirators for healthcare workers. figure 3 shows the impact of using a folded cotton handkerchief mask on the expelled respiratory jet. the folded mask was constructed by following the instructions recommended by the u.s. surgeon general. 60 it is evident that while the forward motion of the jet is impeded significantly, there is notable leakage of tracer droplets through the mask material. we also observe a small amount of tracers escaping from the top edge of the mask, where gaps exist between the nose and the cloth material. these droplets remained suspended in the air until they were dispersed by ambient disturbances. in addition to the folded handkerchief mask discussed here, we tested a single-layer bandana-style covering (not shown) which proved to be substantially less effective in stopping the jet and the tracer droplets. we now examine a homemade mask that was stitched using two-layers of cotton quilting fabric consisting of 70 threads/in. the mask's impact on droplet dispersal is shown in fig. 4 . we observe that the mask is able to arrest the forward motion of the tracer droplets almost completely. there is minimal forward leakage through the material, and most of the tracer-escape happens from the gap between the nose and the mask along the top edge. the forward distance covered by the leaked jet is less than 3 in. in this case. the final mask design that we tested was a non-sterile conestyle mask that is available in most pharmacies. the corresponding droplet-dispersal visualizations are shown in fig. 5 , which indicate that the flow is impeded significantly compared to figs. 2 and 3. however, there is noticeable leakage from gaps along the top edge. the forward distance covered by the leaked jet is ∼6 in. from the mouth opening, which is farther than the distance for the stitched mask in fig. 4 . a summary of the various scenarios examined in this study is provided in table i , along with details about the mask material and the average distances traveled by the respiratory jets. we observe that a single-layer bandana-style covering can reduce the range of the expelled jet to some extent, compared to an uncovered cough. importantly, both the material and construction techniques have a notable impact on the masks' stopping-capability. the stitched mask made of quilting cotton was observed to be the most effective, followed by the commercial mask, the folded handkerchief, and, finally, the bandana. importantly, our observations suggest that a higher thread count by itself is not sufficient to guarantee better stoppingcapability; the bandana covering, which has the highest thread count among all the cloth masks tested, turned out to be the least effective. we note that it is likely that healthcare professionals trained properly in the use of high-quality fitted masks will not experience leakage to the extent that we have observed in this study. however, leakage remains a likely issue for members of the general public who often rely on loose-fitting homemade masks. additionally, the masks may get saturated after prolonged use, which might also influence their filtration capability. we reiterate that although the non-medical masks tested in this study experienced varying degrees of flow leakage, they are likely to be effective in stopping larger respiratory droplets. in addition to providing an initial indication of the effectiveness of protective equipment, the visuals used in this study can help convey to the general public the rationale behind social-distancing guidelines and recommendations for using face masks. promoting widespread awareness of effective preventative measures is crucial, given the high likelihood of a resurgence of covid-19 infections in the fall and winter. the data that support the findings of this study are available within this article. a un framework for the immediate socio-economic response to covid-19 the socio-economic implications of the coronavirus pandemic (covid-19): a review fair allocation of scarce medical resources in the time of covid-19 the incubation period of coronavirus disease 2019 (covid-19) from publicly reported confirmed cases: estimation and application temporal dynamics in viral shedding and transmissibility of covid-19 covid-19 pandemic planning scenarios social distancing, quarantine, and isolation face mask use and control of respiratory virus transmission in households a rapid systematic review of the efficacy of face masks and respirators against coronaviruses and other respiratory transmissible viruses for the community, healthcare workers and sick patients droplet fate in indoor environments, or can we prevent the spread of infection? exhalation of respiratory viruses by breathing, coughing, and talking size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities simplified models for exhaled airflow from a cough with the mouth covered the airborne lifetime of small speech droplets and their potential importance in sars-cov-2 transmission airborne or droplet precautions for health workers treating covid-19? transmission and control of rhinovirus colds core curriculum on tuberculosis: what the clinician should know transmission routes of respiratory viruses among humans recognition of aerosol transmission of infectious agents: a commentary review of aerosol transmission of influenza a virus aerobiology and its role in the transmission of infectious diseases observing and quantifying airflows in the infection control of aerosoland airborne-transmitted diseases: an overview of approaches factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises study on transport characteristics of saliva droplets produced by coughing in a calm indoor environment how far droplets can move in indoor environments-revisiting the wells evaporation-falling curve transport of airborne particles from an unobstructed cough jet a new methodology for studying dynamics of aerosol particles in sneeze and cough using a digital high-vision, high-speed video system and vector analyses the role of particle size in aerosolised pathogen transmission: a review characterizations of particle size distribution of the droplets exhaled by sneeze characterization of expiration air jets and droplet size distributions immediately at the mouth opening on air-borne infection: study ii. droplets and droplet nuclei the size and the duration of air-carriage of respiratory droplets and droplet-nuclei a schlieren optical study of the human cough with and without wearing masks for aerosol infection control violent expiratory events: on coughing and sneezing turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of covid-19 toward understanding the risk of secondary airborne infection: emission of respirable pathogens aerodynamic analysis of sars-cov-2 in two wuhan hospitals air, surface environmental, and personal protective equipment contamination by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) from a symptomatic patient indirect virus transmission in cluster of covid-19 cases visualization of sneeze ejecta: steps of fluid fragmentation leading to respiratory droplets the efficacy of standard surgical face masks: an investigation using "tracer particles a quantitative assessment of the efficacy of surgical and n95 masks to filter influenza virus in patients with acute influenza infection dispersion and exposure to a cough-generated aerosol in a simulated medical examination room efficacy of face shields against cough aerosol droplets from a cough simulator effectiveness of cough etiquette maneuvers in disrupting the chain of transmission of infectious respiratory diseases respiratory virus shedding in exhaled breath and efficacy of face masks assessment of a respiratory face mask for capturing air pollutants and pathogens including human influenza and rhinoviruses simple respiratory protection-evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles testing the efficacy of homemade masks: would they protect in an influenza pandemic? effectiveness of surgical and cotton masks in blocking sars-cov-2: a controlled comparison in 4 patients aerosol filtration efficiency of common fabrics used in respiratory cloth masks rational use of face masks in the covid-19 pandemic nonpharmaceutical measures for pandemic influenza in nonhealthcare settings-personal protective and environmental measures flow dynamics and characterization of a cough coughing frequency in patients with persistent cough: assessment using a 24 hour ambulatory recorder dispersal of exhaled air and personal exposure in displacement ventilated rooms dispersion of exhaled droplet nuclei in a two-bed hospital ward with three different ventilation systems role of ventilation in airborne transmission of infectious agents in the built environment-a multidisciplinary systematic review on coughing and airborne droplet transmission to humans how to make your own face covering key: cord-261580-zghq7mcg authors: sugrue, michael; o’keeffe, derek; sugrue, ryan; maclean, lorraine; varzgalis, manvydas title: a cloth mask for under-resourced healthcare settings in the covid19 pandemic date: 2020-05-12 journal: ir j med sci doi: 10.1007/s11845-020-02241-3 sha: doc_id: 261580 cord_uid: zghq7mcg introduction: covid19 pandemic poses a global threat, with many unknowns. the potential for resource limited countries to suffer huge mortality is of major concern. prevention and risk reduction strategies are paramount in the current absence of effective treatment or a vaccine. there is a global shortage of personal protective equipment. aims: this short paper describes the rationale for and development of a cloth homemade mask and has a step by step video. results: the template is reproducible around the world and is both washable and cheap. conclusion: this article describes a simple way to make a cloth mask, suitable if medical masks are not available. the covid19 pandemic drives the need to maximise the use of available resources to protect people from contracting the virus to minimise morbidity and mortality. there are universal reports of limitations on personal protective equipment (ppe), and many countries in resource-challenged regions have minimal or no reserves [1] . this will result in an inability to control the pandemic and poor outcomes. there are a wide range of ppe and very robust criteria to assess its efficacy and suitability [2] . facial morphology and hair may confound the standards of protection and tolerance of the protection [3] . doremalen and colleagues have recently shown that sars-cov-2 remained viable in aerosols for over 3 hours, with a reduction in infectious titre from 103.5 to 102.7 tcid50 per litre of air [4] . over a decade ago, van der sande identified that a tea towel offered some protection, all be it suboptimal compared to an ffp2 commercial mask [5] . the aim of this report is to share the details for the design and rapid fabrication of a cloth face mask, with the potential to provide the population with alternatives when medical grade face masks are not available. a dress maker (mv) designed multiple prototypes of cloth face masks and after six versions came up with the pattern shown in fig. 1 . the base of the parabolic curved pattern for this full size adult mask was 29 cm. the curve of the mask creates a duckbilled design similar to a commercial ffp2 mask, with a facial cup, nasal bone bridge and two elastic bands. the material used was a polycotton with a tight weave. the nasal bone was created from a coated 3-mm metal garden wire obtained from a hardware shop. the first step was to fold the material in two and pin the pattern to the material. this is cut with a scissors (a view of the step by step mask manufacture and application is available in supplementary video www. dcra.ie) [6] . a small hem is added to the lateral edges to allow the elastic strap to be inserted with ease (marked as b in fig. 1 ). folding the top flaps over, the leaves are sewn together and then stitched to the bottom unfolded leaf. the free flap of the bottom end is then stitched to the top but leaving a 6-cm opening to allow it to be inverted. the mask is then turned inside out. the apical defect of approximately 6 cm is hand stitched closed. all the seams are on the inside so an overlocking stitch was not necessary. at both bases, a 7-mm tunnel was created by stitching to allow the passage of the elastic bands, which can be facilitated by a small round safety pin (marked as a in fig. 1 in video) . the nasal bridge bone was made from a 14 cm length of 3-mm wire coated in plastic and an additional layer of insulating tape was wound the exterior of the wire. the elastic strapping used was 5 mm in width and 60 cm in length for both top and bottom straps. the mask fitted comfortably and provides a good seal (fig. 2) . the elastic bands are placed over the crown of the head and the occiput. there is an additional opportunity to apply tape to the superior edge of the mask to increase the seal or reduce fogging. the cost of the material was less than 1€. the measurements shown in the mask fit an adult male face and adjustment would need to be made according to facial size and features. this work reports the design and fabrication steps of a simple cloth face mask, which may be considered as a last resort for those wishing to have some protection and protect others from aerosol and droplet spread. the enormity of this covid19 pandemic remains to be seen, but apart from china and korea, it remains unabated, with over 1,982,552 cases and 126,753 deaths [7]. protective effects of face masks have been studied extensively, often involving personal respirators for professionals under idealized conditions, involving protection of specifically trained personnel. van de sande has suggested the deployment of masks in the general population during an outbreak of an infectious disease, where anyone may encounter the infectious micro-organism, implying much greater heterogeneity, fig. 1 the pattern for the home made mask in training levels (experience and understanding), goodness of fit of a mask and activities interfering with mask use and thus reducing potential reduction of transmission [5] . transmission barriers, isolation and hygienic measures are effective at containing respiratory virus epidemics. surgical masks are most consistent and comprehensive supportive measures and are not inferior to n95 masks [8, 9] . face masks are only a part of the overall approach but together with personal distancing, hand hygiene and other measures form a bundle which may overcome this disease [8] . the protection conferred by face masks appeared stable over time and was not dependent on activity [5] . given doremalen's recent results indicating that aerosol and fomite transmission of sars-cov-2 is plausible, and since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days, extra caution is required [4] . these findings echo those with sars-cov-1, in which these forms of transmission were associated with nosocomial spread and super-spreading events [10] . the centers for disease control and prevention recommends a 6-ft (2-m) separation [11] . however, bourouiba et al. suggest that these distances are based on estimates of range that have not considered the possible presence of a high-momentum cloud carrying the droplets long distances. given the turbulent puff cloud dynamic model, recommendations for separations of 3 to 6 feet (1-2 m) may underestimate the distance, timescale and persistence over which the cloud and its pathogenic payload travel, thus generating an underappreciated potential exposure range for a health care worker. for these and other reasons, wearing of ppe is important for health care workers caring for patients who may be infected, even if they are farther than 6 ft away from a patient [12] . this may apply to patients and their families also in clinical areas. there is increasing global suggestions that face masks should be worn at all times, but this strategy has yet to be proven. in its current guidance to optimise use of face masks during the pandemic, the centers for disease control and prevention (cdc) identifies three levels of operational status: conventional, contingency and crisis [13] . this mask would be in the crisis category and would intuitively offer more protection to the wearer than no ppe at all. well-resourced countries are increasingly becoming under-resourced in ppe. innovative ideas are required to ensure adequate supplies. the cloth face mask is simple, cheap and made from materials that are globally available. we would not advocate its use in preference over proven medical masks that have been rigidly tested, rather as a last but important option, in the fight against the covid19 pandemic, and is consistent with the application of the precautionary principle [14] . critical supply shortagesthe need for ventilators and personal protective equipment during the covid-19 pandemic hase guidance on respiratory protective equipment (rpe) fit testing, indg 479 0376 if the mask fits: an assessment of facial dimensions and mask effectiveness aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 professional and homemade face masks reduce exposure to respiratory infections among the general population physical interventions to interrupt or reduce the spread of respiratory viruses surgical mask vs n95 respirator for preventing influenza among health care workers: a randomized trial travelers from countries with widespread sustained (ongoing) transmission arriving in the united states turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of covid-19 sourcing personal protective equipment during the covid-19 pandemic face masks for the public during the covid-19 crisis publisher's note springer nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations acknowledgments seamus hughes letterkenny for providing some test material. marite vilcane dressmaker with zip yard letterkenny donegal ireland. we thank seubp and inter regional eu support. key: cord-280220-q4aqkr0w authors: patel, samir n.; mahmoudzadeh, raziyeh; salabati, mirataollah; soares, rebecca r.; hinkle, john; hsu, jason; garg, sunir j.; regillo, carl d.; ho, allen c.; cohen, michael n.; khan, m. ali; yonekawa, yoshihiro; chiang, allen; gupta, omesh p.; kuriyan, ajay e. title: bacterial dispersion associated with various patient face mask designs during simulated intravitreal injections date: 2020-10-28 journal: am j ophthalmol doi: 10.1016/j.ajo.2020.10.017 sha: doc_id: 280220 cord_uid: q4aqkr0w purpose: to investigate bacterial dispersion with patient face mask use during simulated intravitreal injections. design: prospective cross-sectional study methodssetting: single-center study population: fifteen healthy subjects were recruited intervention: each participant was instructed not to speak for 2-minutes, simulating a “no-talking” policy, while in an ophthalmic examination chair with an blood agar plate secured to the forehead and wearing various face masks (no mask, loose fitting surgical mask, tight-fitting surgical mask without tape, tight-fitting surgical mask with adhesive tape securing the superior portion of the mask, n95 mask, and cloth mask). each scenario was then repeated while reading a 2-minute script, simulating a talking patient. main outcome measures: number of colony-forming units (cfu) and microbial species. results: during the “no-talking” scenario, subjects wearing a tight-fitting surgical mask with tape developed fewer cfus compared to subjects wearing the same mask without tape (difference, 0.93cfu; 95%ci, 0.32–1.55; p=.003). during the speech scenarios, subjects wearing a tight-fitting surgical mask with tape had significantly fewer cfus compared to subjects without a face mask (difference, 1.07cfu; p=.001), subjects with a loose face mask (difference, 0.67; p=.034), and subjects with a tight face mask without tape (difference, 1.13; p<.001). there was no difference between those with a tight-fitting surgical mask with tape and an n95 mask in the “no-talking” (p>.99) and “speech” (p=.831) scenarios. no oral flora was isolated in “no-talking” scenarios, but was isolated in 8/75 (11%) cultures in speech scenarios (p=.02). conclusion: addition of tape to the superior portion of a patient’s face mask reduced bacterial dispersion during simulated intravitreal injections, and had no difference in bacterial dispersion compared to wearing n95 masks. since the introduction of intravitreal anti-vascular endothelial growth factor (anti-vegf) therapy, intravitreal injections have become one of the most commonly performed procedures in all of medicine. 1 although these medications have excellent safety profiles, acute bacterial endophthalmitis remains an uncommon but visually devastating complication. 2 multiple prior studies have evaluated potential risk factors associated with post-injection endophthalmitis. [3] [4] [5] [6] [7] in particular, prior studies have established that the dispersion of oral flora may be reduced by minimizing speaking during the procedure and thereby reduce the incidence of oral flora-associated endophthalmitis. 7 prior experimental investigations involving simulated intravitreal injections suggest that face mask use by physicians may reduce bacterial dispersion associated with speech. 8, 9 however, it is unknown how patient face mask use may affect bacterial dispersion. these findings are of particular importance given that, during the covid-19 pandemic, universal precautions have been established for patients and physicians to wear face masks in order to decrease potential exposure to coronavirus through respiratory secretions. 10, 11 however, there is concern that face mask use by patients during an intravitreal injection may result in increased bacterial dispersion toward the eye. prior studies have suggested that various face mask designs may result in upward or downward bacterial dispersion. 12, 13 furthermore, in response to the critical shortage of medical face masks resulting from the covid-19 pandemic, many patients may be wearing homemade cloth masks as recommended by the center for disease control and prevention. 14 it is unknown how these types of face masks may affect the degree of bacterial dispersion. the purpose of this study is to investigate the amount of bacterial dispersion associated with various patient face mask designs during simulated intravitreal injections. this prospective, cross-sectional, single-center study was conducted in accordance with the tenets of the declaration of helsinki and conformed to the health insurance portability and accountability act. the protocol was prospectively approved by wills eye hospital institutional review board, and all participants provided written informed consent. fifteen healthy subjects were recruited to participate in the study as previously described. 8 inclusion criteria included subjects at least 18 years of age with the ability to read a standardized script for two minutes. all subjects had previously received fittesting for n95 face masks based on the united states occupational safety and health administration guidelines. exclusion criteria included any subject with a history of upper respiratory symptoms, fever, cough, or chills within the past two weeks. each subject was seated in an ophthalmologic examination chair in a standard examination lane at an outpatient ophthalmology office. the examination chair was reclined until the volunteer's face was approximately 45 degrees from to the ground. a j o u r n a l p r e -p r o o f standardized 100mm circular blood agar plate (bd bbl tsa ii 5% sheep blood; becton, dickinson and company, franklin lakes, nj) was then secured on the subject's forehead. twelve scenarios were then tested. six scenarios simulated a "no talking" policy in which the subjects were instructed to sit in silence for two minutes while breathing with their mouth closed. after completing the "no talking" scenarios, subjects were instructed to read a standardized script for two minutes for each of the six scenarios. for both the "no talking" and speaking scenarios, the face mask conditions included the following: (1) wearing no face mask, (2) wearing a loose fitting surgical face mask ( figure 1a all blood agar plates were sealed and taken to jefferson clinical microbiology laboratory (thomas jefferson university, philadelphia, pa) where they were incubated for 72 hours at 37°c in a 5% carbon dioxide-rich environment. the number of bacterial colonies per plate was counted, and bacteria were identified using standard laboratory techniques by microbiologists who were masked to the plate collection sequence. no organisms were excluded from analysis, and a culture was considered to be oral floraassociated when enterococcus or streptococcus species was grown on culture. all data were analyzed using statistical software (ibm spss 25 statistics, armonk, ny, usa). the mean difference of colony-forming units (cfus) and 95% confidence intervals among the groups were analyzed using an analysis of variance with adjustment for multiple comparisons using a bonferroni correction. for categorical variables, significant differences between groups were analyzed using a pearson's chisquared test or fisher's exact test. pair wise comparisons between the "no talking" scenario and speech scenarios were performed using a paired student's t-test with adjustment for unequal variances. statistical significance was considered to be a 2sided p value < .05. fifteen subjects were recruited for the study, and a total of 180 blood agar plates were successfully incubated. overall, the mean (sd) [range] cfu was 0.56 (0.88) [0 -4] in the "no talking" scenarios compared to 0.83 (0.95) [0 -6] in the speech scenarios (p = .044). bacterial dispersion during "no talking" conditions figure 2a shows the cfus under the "no talking" scenario among the different face mask conditions. during the "no talking" scenario, subjects with tight-fitting face mask without tape grew the most colonies with a total of 17 cfus or a mean (sd) of 1.13 (1.60) per subject. in contrast, during the "no talking" scenario, subjects with a tight-fitting face mask with adhesive tape or those with an n95 mask both grew the fewest number of colonies with a total of 3 cfus or a mean (sd) of 0.20 (0.56) and 0.20 (40) per subject, respectively. notably, during the "no talking" scenario, subjects wearing an n95 mask grew fewer cfus compared to subjects wearing a tight-fitting face mask without tape (mean difference, 0.93; 95% ci, 0.32 -1.55; p = .003). furthermore, during the "no talking" scenario, subjects wearing a tight-fitting face mask with tape grew fewer cfus compared to subjects wearing a tight-fitting face mask without tape (mean difference, 0.93; 95% ci, 0.32 -1.55; p = .003). however, during the "no talking" scenario, there was no difference between subjects wearing the tight-fitting face mask with tape and subjects wearing an n95 mask (difference, 0; 95% ci, -0.62 -0.62; p >.99). during the "no talking" scenario, there was no significant difference in mean cfus between the no face mask and loose fitting face mask group (p = .831), between the no face mask and tight-fitting face mask (p = .089), between the no face mask and tight-fitting face mask with adhesive tape (p = .201), between the no face mask and n95 face mask (p = .201), and between the no face mask and cloth face mask (p = .831). bacterial dispersion during speech conditions figure 2b shows the mean cfus under the speech scenario among the different face mask conditions. during the speech scenarios, subjects wearing a tight-fitting face mask without tape grew the most colonies with a total of 21 cfus or a mean (sd) of 1.4 (0.82) per subject. subjects wearing an n95 mask grew the fewest colonies with a total of 3 cfus or a mean (sd) of 0.2 (0.40) per subject. subjects wearing a tight-fitting face mask with adhesive tape during the speech scenario grew significantly fewer cfus compared to the following groups: 1) subjects with no face mask (mean difference, 1.07; 95% ci, 0.45 -1.68; p = .001); 2) subjects with a loose face mask (mean difference, 0.67; 95% ci, 0.05 -1.28; p = .034); and 3) subjects with a tight face mask without tape (mean difference, 1.13; 95% ci, 0.52 -1.75; p < .001). subjects wearing an n95 face mask during the speech scenario grew significantly fewer cfus compared to the following groups: 1) subjects with no face mask (mean difference 1.13; 95% ci, 0.52 -1.75; p < .001); 2) subjects with a loose face mask (mean difference 0.73; 95% ci, 0.12 -1.35; p = .02); 3) subjects with a tightfitting face mask without tape (mean difference 1.20; 95% ci, 0.59 -1.82; p < .001); and 4) subjects with a cloth face mask (mean difference, 0.67; 95% ci, 0.05 -1.28; p = .034). during the speech scenario, there was no difference between subjects wearing the tight-fitting face mask with tape and subjects wearing an n95 mask (difference, 0.07; 95% ci, -0.55 -0.68; p = .831). bacterial dispersion between the speech and "no talking" conditions table 1 summarizes the mean (sd) cfus for each face mask design during the "no talking" and speech scenarios. in the no face mask scenario, subjects had significantly more mean cfus during the speech scenario when compared to the "no talking" scenario (mean difference, 0.73; 95% ci, 0.12 -1.35; p = .020). there was no j o u r n a l p r e -p r o o f difference in mean cfus between the "no talking" and the speech scenarios with a loose fitting face mask (p = .201), tight-fitting face mask without tape (p = .393), tightfitting face mask with adhesive tape (p = .831), n95 face mask (p > 0.99), or cloth face mask (p = .521). a total of 125 cfus were isolated with 50 isolated during the "no talking" scenario and 75 isolated in the speech scenario. of the 50 cfu in the "no talking" group, 0/50 (0%) were from oral flora, whereas 8/75 (11%) of the cfu in the speech group were from oral flora (p=.02). the most common organism isolated in the "no talking" scenario were staphylococcal species (32/50, 64%). in the speech scenarios, the most common organism isolated in the "no talking" scenario were staphylococcal species (38/75, 51%). in the speech scenarios, 8 oral flora organisms were isolated with of 4 of the cases in the no face mask scenario, and 4 cases in the tight-fitting face mask without adhesive tape scenario. causative oral flora organisms included 3 colonies of streptococcus mitis, 3 colonies of streptococcus viridans, and 2 colonies of undifferentiated streptococcus. the covid-19 pandemic has necessitated universal face mask protocols for infection control, which has resulted in significant interest in understanding face mask effectiveness from various disciplines, 11,15-17 including ophthalmology 18 . however, there are few data on how patient face mask use may alter bacterial dispersion during an intravitreal injection, which subsequently may affect the risk of post-injection endophthalmitis. in this experimental study of bacterial dispersion during a simulated intravitreal injection scenario with six different face masks, we found that subjects wearing tight-fitting face masks without adhesive tape covering the superior portion of the mask grew the most bacterial organisms under both "no talking" and speech scenarios. however, the introduction of adhesive tape to secure the superior portion of the same tight-fitting face mask significantly reduced the amount of bacterial dispersion toward the eyes. furthermore, the introduction of adhesive tape to secure the superior portion of a tight-fitting face mask resulted in no statistically significant difference in bacterial dispersion compared to bacterial dispersion with an n95 face mask. we assessed the number of cfus under "no talking" conditions to simulate the clinical practice of a "no talking" policy in which intravitreal injections are administered under a strict policy of silence such that the physician, patient, and others in the room do not speak during the injection procedure. under the "no talking" condition, bacterial growth around the subject's eye was highest when wearing a tight-fitting face mask without adhesive tape, and the source of bacteria in these "no talking" scenarios may be from the subject's natural breathing. a known physiologic reaction to stress and anxiety is to hyperventilate, which some patients routinely do as they are anticipating an intravitreal injection, and wearing a mask may contribute to this phenomenon. however, bacterial growth was significantly reduced when subjects wore the same tight-fitting face mask but had adhesive tape attached over the entire superior portion of the face mask. the bacterial growth was reduced such that the addition of adhesive tape to the tightfitting face mask resulted in similar rates of bacterial growth compared to those wearing an n95 face mask. a prior study on face mask use by the injector during simulated intravitreal injections reported that subjects speaking without a face mask resulted in an increased proportion of bacterial colony growth. 8 the current study evaluated bacterial growth under speech scenarios where subjects were instructed to read a 2-minute standardized script while wearing various face masks. regardless of the type of face mask worn, subjects in the speech scenarios had significantly greater bacterial growth compared to the "no talking" scenarios. specifically, subjects wearing no face masks had greater bacterial growth in the speech scenario compared to the "no talking" scenario. these findings underscore the importance of a speech reduction policy when intravitreal injections are administered. furthermore, within the various speech scenarios, subjects wearing n95 face masks and tight-fitting face masks with adhesive tape had significantly fewer cfus compared to subjects wearing no face masks, loose face masks, and tight-fitting face masks without tape. current guidelines from the center for disease control and prevention at the time of writing recommend cloth face covering, which may not adhere to the face as well. 14 our study found similar rates of bacterial dispersion with cloth based face mask use in both scenarios. although we did not assess the effect of adhesive tape for cloth face masks, future studies may be indicated to evaluate these specific scenarios given the findings of this study. in both the "no talking" and speech scenarios, subjects wearing a tight-fitting face mask without tape had the highest bacterial growth -similar to, or even higher than, not wearing any mask. it is possible that the tight-fitting face without tape may result in a greater amount of bacterial dispersion upward toward the subject's eye. 12, 17 indeed, a recent study assessing respiratory droplet velocities with face mask use during simulated coughs reported that even with tight-fitting face masks, small openings can lead to leakage of droplets around the mask. 17 however, our study suggests that securing the superior portion of the same, tight-fitting face mask with adhesive tape significantly decreased the amount of bacterial growth, suggesting that securing the superior portion of the mask with tape may create an important barrier for upward bacterial dispersion. although all forms of endophthalmitis are visually threatening, oral floraassociated endophthalmitis is associated with a particularly poor prognosis. [19] [20] [21] prior clinical studies have established that oral flora-associated endophthalmitis may be reduced with the implementation of a strict "no talking" policy by the physician and patient during intravitreal injection administration. 7, 21 refraining from speaking during an intravitreal injection is thought to minimize the potential to contaminate the uncapped needle or conjunctival surface with oral flora immediately before or during the injection. indeed, in our study, there were no cases of oral flora isolated during the "no talking" scenarios, which further supports the efficacy of a speech reduction policy to reduce the risk of oral flora-associated endophthalmitis. in contrast, during the speech scenarios, oral flora were isolated when subjects were speaking without a face mask or speaking j o u r n a l p r e -p r o o f with a tight-fitting face mask without tape, which parallel a prior study showing high rates of oral flora growth during similar scenarios. 8 our study has several limitations. blood agar plates were used for bacterial quantification and identification. however, these plates do not precisely reproduce the target field of the ocular surface. furthermore, we standardized the distance between the agar plate and the eye, the duration of speech, and the positioning of the face mask, but in real world clinical scenarios there may be significant variability in all of these clinical factors. for example, prior studies have reported that the tendency to wiggle one's face beneath a surgical mask 12 may increase bacterial dispersion and shedding, presumably from the beard and facial skin. another limitation is that the speech scenarios had the subject read a script for two minutes, which is likely more time than any patient would spend speaking during an intravitreal injection. however, two minutes may be realistic when considering the preparation time for an intravitreal injection during which the patient may be speaking. furthermore, prior studies have suggested that bacterial dispersal can occur even with shorter durations of speech. 22 another limitation is that our study included participants who were previously fitted to wear n95 face masks, which may not be generalizable to the true patient population who wears n95s. our findings may be underestimating the real world benefit of taping because many patients come in with suboptimal fitting masks, regardless of material or type. finally, it is unknown if the statistically significant difference in colony counts among the groups is of clinical significance. this study cannot prove that the presence of additional bacterial colonies surrounding the injection site necessarily contributes to an increased risk of post-injection endophthalmitis. however, given the devastating visual prognosis of postinjection endophthalmitis, it is critical to minimize the potential risk of endophthalmitis with any measures available. in summary, these experiments replicate the specific conditions of an intravitreal injection when patients are wearing different types of face masks. until now, there was minimal evidence in the literature to guide practitioners in the management of patient face mask use during an intravitreal injection. these in vitro experiments suggest that addition of adhesive tape to the superior portion of a patient's face mask during an intravitreal injection reduces bacterial dispersion, which may subsequently reduce the risk of post-injection endophthalmitis. no talking" scenarios in which subjects were instructed to sit in silence for two minutes. 2b) speech scenarios in which subjects were instructed to read a script for two minutes. error bars represent standard deviation. * indicates p < 0.05 and ** indicates p < 0.01, and *** indicates p < 0.001. cfu = colony-forming units. • patient face mask use may alter bacterial dispersion around the eye during intravitreal injections. • there was significantly more bacterial dispersion when wearing a tight-fitting face mask without tape compared to wearing a tight-fitting mask with tape. • there was no difference in bacterial dispersion between tight-fitting surgical masks with tape and n95 masks. • taping the superior portion of a patient's face mask may limit bacterial dispersion when performing intravitreal injections. this study evaluated if face masks worn by patients during intravitreal injections altered bacterial dispersion around the eye. in this cross-sectional study of 15 participants undergoing simulated intravitreal injections with six face mask designs, there was significantly more bacterial dispersion when wearing a tightfitting face mask without tape compared to wearing a tight-fitting mask with tape. taping the superior portion of a patient's face mask may limit bacterial dispersion when performing intravitreal injections. trends of anti-vascular endothelial growth factor use in ophthalmology among privately insured and medicare advantage patients international practice patterns for the management of acute postsurgical and postintravitreal injection endophthalmitis: european vitreo-retinal society endophthalmitis study report 1 endophthalmitis following intravitreal injections performed in the office versus operating room setting outcomes and risk factors associated with endophthalmitis after intravitreal injection of antivascular endothelial growth factor agents the role of topical antibiotic prophylaxis to prevent endophthalmitis after intravitreal injection the impact of prefilled syringes on endophthalmitis following intravitreal injection of ranibizumab effect of a strict 'no-talking' policy during intravitreal injection on post-injection endophthalmitis bacterial dispersal associated with speech in the setting of intravitreous injections reducing oral flora contamination of intravitreal injections with face mask or silence universal masking in hospitals in the covid-19 era visualizing speech-generated oral fluid droplets with laser light scattering mask wiggling as a potential cause of wound contamination is a mask necessary in the operating theatre? use of cloth face coverings to help slow the spread of covid-19 physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis visualizing the effectiveness of face masks in obstructing respiratory jets on respiratory droplets and face masks do slit-lamp shields and face masks protect ophthalmologists amidst covid-19? microbial spectrum and outcomes of endophthalmitis after intravitreal injection versus pars plana vitrectomy endophthalmitis after intravitreal injection: the importance of viridans streptococci endophthalmitis following intravitreal injection the use of surgical facemasks during cataract surgery: is it necessary? key: cord-270766-rasjpg8v authors: luan, phan thien; tak-shing ching, congo title: a reusable mask for coronavirus disease 2019 (covid-19) date: 2020-04-10 journal: arch med res doi: 10.1016/j.arcmed.2020.04.001 sha: doc_id: 270766 cord_uid: rasjpg8v abstract the outbreak of novel coronavirus is causing an intensely feared globally. world health organization has even declared that it is a global health emergency. the simplest method to limit the spread of this new virus and for people to protect themselves as well as the others is to wear a mask in crowded places. the sudden increase demand on face mask has caused manufacturers the inability to not provide enough products in a short time and the situation properly will stay the same for a period of time. in this article, we aim to give an idea on how to save the number of face masks used but still provides the same protective values using a cardiopulmonary resuscitation (cpr) mask and a common surgical facemask. the outbreak of novel coronavirus is causing an intensely feared globally. world health organization has even declared that it is a global health emergency. the simplest method to limit the spread of this new virus and for people to protect themselves as well as the others is to wear a mask in crowded places. the sudden increase demand on face mask has caused manufacturers the inability to not provide enough products in a short time and the situation properly will stay the same for a period of time. in this article, we aim to give an idea on how to save the number of face masks used arch med res e20_298 2 but still provides the same protective values using a cardiopulmonary resuscitation (cpr) mask and a common surgical facemask. key words: reusable, face mask, coronavirus disease. at the end of 2019, an outbreak of pneumonia cases of unknown causes has raised greatly concerned internationally in wuhan, hubei province, china. novel coronavirus or ncov has been found to be the cause of this outbreak by chinese medical experts and the report was published in the lancet (1). since then, the number of cases has been intensively increased and the risk assessment level around the world is very high. up until 12 th february 2020, 43103 cases with 1018 deaths have been confirmed globally (2) . in fact, the outbreak has caused the world health organisation to declare a global health emergency. staying hygiene by washing your hand frequently or cover mouth and nose with tissue or elbow when coughing and sneezing is among the basic protective measures. for people who need to be in crowded places such as the market, public transportation or especially school and hospital, it is recommended that they should always wear a facemask in order to stop the spread of the virus. single-use surgical face masks are a very common item that people choose to either protect themselves or others. "surgical masks were originally designed to protect the wearer from infectious droplets in clinical settings, but it doesn't help much to prevent the spread of respiratory diseases such as sars or mers or influenza", hyo-jick choi (3). although they are not an absolute protection method, they do provide a barrier that will protect the wearer from a spray of fluid, sneezing for example, and catch the bacteria shed in liquid droplets and aerosols from the wearer's mouth and nose (4, 5) . the sudden growing demand on face mask has made the number of available masks become insufficient. it is reported that, only in china, with a population of more than 1.3 billion, mask production rates globally properly can't even meet the country's needs. due to the act of china stopping the exportation of facemask and mask making material, mask production around the world is being affected. in taiwan, since february 6th, the government is instituting a registration system to ration the supply of masks to two per person per week (6). this is clearly not enough because the mask should only be used once and thrown away right after used, as masks are used, they collect exhaled airborne pathogens that remain living in the masks' fibers, rendering them infectious when handled. in this situation, people need a way to use less facemask but still can shield themselves from the illness. because of the above reasons, this commentary aims to provide a novel idea on how to combine the use of a reusable cpr mask and a piece of the surgical face mask to limit the amount of face mask uses but still have the same protective value. the main idea is to create a filter for the cpr mask by to test the cpr isolation efficiency, a plastic bag is used to cover the connector hole ( figure 1b) then carefully sealed it with a rubber band and some teflon tape. then by pumping air on the wearer's end of the mask and determine if there is any leakage on the sealed end of the connector hole, the arch med res e20_298 4 cpr mask will be proved to be fully sealed and can be used as a substitute for the lacking of surgical face mask after given a sufficient filter. the commercial surgical face masks (figure 2a) commonly had a three-layer structure. the middle layer is the filter media, whereas the inner layer is for absorbing moisture, and the outer layer repel water. on the surgical mask, the metal nose clip and elastic ear loops, as well as rectangular samples ( figure 2b ), were cut out. the sample is used to cover the connector of the cpr mask ( figure 1c ), with the same method, tightly sealed the sample on the connector with a rubber band or teflon tape, thus giving the cpr reusable mask the same filter from the surgical face mask. this article tries to give a new method in which people can limit the amount of face mask uses per week. the cpr mask can easily be cleaned (by using 75% alcohol solution or liquid bleaching agents) after use and the surgical mask piece can be thrown away. as countries are limiting the number of masks sold to citizens, taiwan for example, only allows people to buy two masks per person per week (6). the surgical face mask comes in a wide variety of sizes, commonly at 18 centimeters long and 10 centimeters wide. this means if cut into 6 samples such as suggestted ( figure 2b) we can have at least 6 filter pieces per piece of face mask. by applying this method, 2 masks can be used for at least 12 times per week, so instead of having to use 2 masks for a week, people can use more than 1 different filter piece per day. by proving that the cpr mask is totally sealed with the isolation examination experiment, the filter is 100% provided by the surgical facemask thus giving the exact same protection value. furthermore, arch med res e20_298 5 the surgical masks fit loosely on the face around the edges, so they don't completely keep out the germs, and small airborne particles can still get through those edges. whereas the cpr mask, can fir tightly on the user's face, thus giving even higher protection. this method should be applied where people cannot afford to have enough surgical masks to protect themselves. it is especially effective for people who have to be in a crowded place for a short period of time, being in public transportation for example. funding this is no funding support for this study and manuscript. a novel coronavirus outbreak of global health concern world health organization, novel coronavirus (2019-ncov) -situation report -22, data as universal and reusable virus deactivation system for respiratory protection procedure mask. nursingcenter.com (accessed on respiratory protection against airborne infectious agents for health care workers: do surgical masks protect workers? (osh answers fact sheets). canadian centre for occupational health and safety ever ready first aid adult and infant cpr mask combo kit the authors declare that they have no conflict of interest. key: cord-304941-yg4x7c8n authors: hossain, emroj; bhadra, satyanu; jain, harsh; das, soumen; bhattacharya, arnab; ghosh, shankar; levine, dov title: recharging and rejuvenation of decontaminated n95 masks date: 2020-09-01 journal: phys fluids (1994) doi: 10.1063/5.0023940 sha: doc_id: 304941 cord_uid: yg4x7c8n n95 respirators comprise a critical part of the personal protective equipment used by frontline health-care workers and are typically meant for one-time usage. however, the recent covid-19 pandemic has resulted in a serious shortage of these masks leading to a worldwide effort to develop decontamination and re-use procedures. a major factor contributing to the filtration efficiency of n95 masks is the presence of an intermediate layer of charged polypropylene electret fibers that trap particles through electrostatic or electrophoretic effects. this charge can degrade when the mask is used. moreover, simple decontamination procedures (e.g., use of alcohol) can degrade any remaining charge from the polypropylene, thus severely impacting the filtration efficiency post-decontamination. in this report, we summarize our results on the development of a simple laboratory setup allowing measurement of charge and filtration efficiency in n95 masks. in particular, we propose and show that it is possible to recharge the masks post-decontamination and recover filtration efficiency. face masks are our first line of defense against airborne particulate matter. 1, 2 in particular, n95 34 respirators comprise a critical part of the personal protective equipment (ppe) used by frontline health-care workers as they provide a barrier for transmission of pathogen laden droplets that are ejected by coughing, sneezing, talking, or breathing by an infected person. [3] [4] [5] [6] the name designation n95 indicates that these masks can filter 0.3 μm sized particles with 95% efficiency. 4 n95 masks are meant for one-time usage for two reasons: (1) potential contamination and (2) rapid degradation of their filtration efficiency with use. however, the recent covid-19 pandemic has resulted in a serious shortage of these masks, which has started an intensive search for methods, which would allow for multiple uses. most of the literature has dealt with various proposals for decontamination procedures, including careful use of dry and wet heat or exposure to hydrogen peroxide vapor, ozone, uv radiation, or alcohol. 5, [7] [8] [9] [10] [11] [12] [13] [14] while each of these methods likely deactivates viruses, it seems to be common knowledge that such procedures adversely impact filtration efficiency and may even cause deterioration of the structural integrity of the mask. less attention has been focused on restoring the filtration efficiency of a mask once it has become degraded; this is the question we address in this work. in this paper, we propose a method, which, provided the mask has not been structurally compromised, can restore the filtration efficiency to out-of-box levels. as with other filtration processes, n95 masks intercept foreign particles in different layers of the mask material. a particle can be captured either mechanically, if it encounters a mask scitation.org/journal/phf fiber directly in its path, or electrostatically, if the mask material is such that it can attract and ensnare particles. 16 on making contact with the surface of the fiber, adhesive forces, such as the van der waals force, immobilize the particle on the surface of the fiber. 17 flow through a mask is usually thought to be laminar such that the flow would usually bend smoothly around an obstacle (fiber). if this is the case, mechanical capture of the particle on the surface of the fiber happens when a particle deviates from its streamline path, causing an impact with the mask material. this can happen for larger particles whose inertia is large enough to cause such a deviation from the streamline or for smaller particles whose brownian diffusion is strong enough. 18 for filters based on fibrous materials and operating at filtration velocities similar to those encountered in human breathing, the minimum filtration efficiency occurs for ≈0.3 μm sized particles. at this scale, the filtration mechanism crosses over from a diffusion dominated regime to an inertia dominated regime. 19 in addition to mechanical capture, n95 respirators employ an electrostatic mechanism to attract and intercept foreign particles (charged or uncharged). this happens when there are significant electric fields and electric field gradients in the mask material, which may occur when the fibers are charged. 20 it is these electrostatic interactions that raise the filtration of n95 masks to the 95% level. charged fibers can attract both inherently charged particles by coulombic forces and neutral polar particles (such as tiny aqueous droplets) by dielectrophoretic forces that come from the interaction of polarized objects and electric field gradients. in typical n95 masks, the electrostatic filtration is performed by a layer comprised of a non-woven melt-blown mesh of charged polypropylene fibers. most of the pores in this mesh have a characteristic length scale of about 15 μm, and about 90% of its space is void. this layer is held in place between two or more quasi-rigid layers that provide both support and mechanical filtration. polypropylene is an electret, a dielectric material, which can hold a charge or possess a net microscopic dipole moment. 21 pure polypropylene is a non-polar polymer with a band gap of 8 ev. however, the presence of molecular level defects both chemical and physical in nature allows the formation of localized energy states that can trap charge. 21 moreover, its electrical polarization properties are often enhanced by introducing various additives such as magnesium stearate 22 or batio 3 , 23 which are added to the polymer melt to increase the electret performance. even then, the charge on the polypropylene fibers undergoes significant degradation when open to the surroundings, which is exacerbated by the warm humid environment created by respiration during use. additionally, most decontamination methods remove all the charges from the charged layer, with a concomitant reduction in mask efficiency. thus, a key aspect of the performance of an electret-based mask is its ability to maintain its charge in a hot and humid atmosphere. failing this, extended usage can only be obtained through a cycle of decontamination and recharging if this is possible. it follows that a simple procedure for electrically recharging a decontaminated mask without disassembling it would be very useful, especially if it does not rely on special-purpose equipment, which would not be readily available. the standard methods for charging polymer fibers are corona discharge, 24 photo-ionization induced by particle beams (gamma rays, x-rays, and electron beams), 25, 26 tribo-electrification, [27] [28] [29] and liquid contact charging. 30 these methods are not easily deployable in hospital conditions on preassembled masks. in this note, we propose a simple recharging method based on high electric fields and demonstrate its effectiveness. crucially, our method can be performed using readily available equipment and materials and so can be employed both in urban and rural settings. because of the covid-19 pandemic, we did not have access to special-purpose mask filtration equipment, so we designed and constructed a rough apparatus to measure the efficiency of filtration of particulate matter using an air-quality monitor as a particle counter. the setup is shown in fig. 1 . a plastic ball serves as our proxy of the human face, on which we place the mask that we want to test. air is sucked through the mask with a vacuum pump whose flow rate is controlled and monitored by using a flow meter. we use an oil-free diaphragm pump (hsv-1, high speed appliances, mumbai) that provides a maximum flow of 30 lpm. the flow can be measured and controlled with a taper-tube flow meter. for most experiments, we used a flow of 10 lpm, similar to typical human breathing rates. this air is made to flow through a particle counting setup, which contains a plantower pms7003 sensor. 35 the details of the experimental setup can be found in the github repository 15 or in the supplementary material. while the particle sensor chips are optimized for 2.5 μm particle measurements, the plantower pms7003 sensor also has a 0.3 μm channel. the filtration efficiency (η) is determined from the ratio of 0.3 μm particles per unit time detected with the mask attached (n mask ) to that without the mask attached (n ambient ) as our measurements are taken using a small diaphragm pump to suck air through a mask attached to a plastic ball at flow rates (∼10 lpm) of the order of physiological breathing rates. much higher flow rates (∼80 lpm) are often used to certify n95 masks. to check for the dependence of the filtration efficiency on flow rates, we measured the filtration efficiency for flow rates between 3 lpm and 30 lpm and have found that the difference in the measured η is about one percent. the efficiency of our particle counter for smaller particles is of order 50%. since η is related to the ratio of n mask and n ambient , it is insensitive to the fact that not all the particles at 0.3 μm are being counted. we have cross-checked the measurements obtained with the plantower chip with a lighthouse clean-room particle counter, and we found the measurements of η by both the devices to be consistent. for the ambient air to be filtered, we generated aerosols of normal saline solution (0.9%) by employing a standard medical nebulizer. these nebulizers produce a broad distribution of droplet sizes ranging from 100 nm to 10 μm. 31 the fit of the mask to the plastic ball is imperfect, allowing air leakage from the sides. to obtain reproducible values, the mask edges were taped to the ball using paper masking tape. the filtration data, albeit employing a home-made testing apparatus, should be sufficient to make at least semi-quantitative comparisons between one mask and another and quantitative comparisons between the same mask in its charged and uncharged states. to give a sense of the measurement, the filtration data from a pristine n95 mask are shown in fig. 2 . when the mask is placed on the ball without taping the sides, its efficiency was 76% ± 1%. upon taping the sides, the efficiency improved to 95% ± 1%. the reduction in the filtering efficiency due to poor fitting is a generic problem associated with the use of face masks. 1 as shown in fig. 3(a) , we used a keithley 6514 electrometer to measure the charge, with the mask placed in a metal cup, which was electrically isolated from the ground by an insulating fig. 2 . filtration tests on a pristine venus 4400 n95 mask. for the initial and final readings, no mask was attached, which serves as a baseline. when untaped, the seal between the mask and the ball is imperfect, and the filtration efficiency is 76% ± 1%. upon taping the mask to the ball, we obtain ∼95% ± 1% filtration efficiency. teflon surface. the input of the electrometer is a three-lug triax connector, with the innermost wire (input high) being the charge sensing terminal. this charge sensing terminal of the electrometer was connected to the metal cup. in our experiments, we used the guard-off condition, i.e., the common (input low) and the chassis are grounded. electrometers measure charge by transferring the charge from the point of measurement to the reference capacitor of the electrometer, and only free charge can be transferred. therefore, since it does not account for any bound charge, our measurement likely underestimates the total charge on a mask and so should be regarded as giving a relative indication rather than a precise measurement of the total charge on the masks. this being said, there appears to be a qualitative correlation between measured charge and filtration efficiency, with masks with higher values of measured charge having higher filtration efficiency η (see table i ). the data of both n95 and surgical masks are tabulated in table i . the surgical masks are different than the n95 masks in construction. hence, comparisons between charge and filtration efficiency should be made between masks of the same type. moreover, our charge measurement technique is not sensitive to the dipolar character of the electrets. hence, quantitative calculation of correlation based on free charges cannot be estimated from this measurement alone. the masks were recharged by sandwiching them between two metal plate electrodes, which were connected to the high and the low output terminals of a srs ps370 power supply. the low output terminal was grounded, and a suitable voltage of positive or negative polarity was applied from the high output terminal of the source meter; fig. 3 (b) sketches the recharging setup. our recharging method exploits the nonlinear conductivity of electrets, in particular, polypropylene, as a function of the applied electric field. the electrical conductivity of polypropylene is dominated by hopping. 32, 33 thus, at high fields, the conductivity of polypropylene is high, which makes the introduction of excess charges into the material possible by connecting it to a charge source. when the charge source is switched off, the applied electric field becomes zero, and conductivity of the polypropylene drops effectively to zero. as a result, the added charge carriers become immobile, and the material remains charged. we find that the total charge deposited on the masks depends strongly on the charging time, as seen in fig. 4 , which shows the result of different charging times on a n95 mask, with the pristine value almost reattained after a 60 min charge at 1000 v. in the section titled recharging, we demonstrated that the application of a relatively high voltage recharges the masks. of course, the important test is whether this recharging translates into improved efficiency in the filtration of fine particles. to assess this, we first obtained a baseline measurement for the filtration efficiency of new unused masks (the masks were not individually vacuum sealed). we then performed typical sanitization protocols, during which the masks typically lost most of their charge (we emphasize again that we are primarily measuring the free charge) and measured the filtration efficiency of the discharged masks. we then recharged the masks and measured their filtration efficiency. the effect of different sanitization protocols and recharging on the filtration efficiency of the masks is tabulated in table ii . representative data of the filtration efficiency of various masks after decontamination and recharging are given in the top panels of fig. 5 , where we start with a new kn95 mask whose out-of-box filtration efficiency was measured to be 95% ± 1% [see fig. 5(a) ]. the mask was then washed at ∼40 ○ c in a conventional washing machine with detergent. such treatment would be expected to dissolve the lipid layer of the sars-cov-2 virus, which causes covid-19. the mask was then air dried, and its efficiency was measured to be 75% ± 1% [see fig. 5(b) ]. the mask was then recharged for 60 min using the method of fig. 3(b) , following which its filtration efficiency was measured to be 95% [see fig. 5(c) ]. we then repeated this protocol and found that the filtration efficiency reattained 95% ± 1%. figure 5(d) shows that the filtration efficiency of an exposed mask degrades only slightly, from ∼95% ± 1% to ∼92% ± 1%, over the course of one day. this suggests that the use of sterilization procedures, which do not cause structural damage to a mask coupled with our recharging protocol, will produce a respirator, table ii. the drop in the filtration efficiency in n95 masks due to different protocols of decontamination and the recovery of filtration by recharging the masks. for the kn95 masks, we used 2000 v, while for the venus and magnum n95masks, we used 1000 v a . for decontamination by ethanol, a new kn95/magnum mask was soaked in ethanol and then dried. in the boiling method, the mask was immersed in boiling water for 1 h and then dried. for the washing machine method, the mask was laundered in a regular washing machine in a standard 40 ○ c, 84 min cycle, wash/rinse/spin dry cycle. for the steam method, the venus mask was exposed to steam for 5 min on each side. for all these protocols, we started with a new n95mask. which may be used multiple times with no sacrifice in filtration efficiency. we have verified that the recharging method works on a variety of n95 respirators and that the filtration efficiency of degraded masks can be improved by charging, if not to brand-new efficiency. this suggests that by using this method, we should be able to determine the effect of various disinfection protocols on the structural integrity of different brands of mask. in this context, we note that a given sensitization method may affect different brands of masks very differently, as seen in table ii . 6. (a) schematic representation of the in situ continuously charged mask, whose cartridge fits onto a 3d printed housing. (b) upon applying a field, the efficiency of the cartridge improves from 85% ± 1% to about 95% ± 1%. filtration measured for 0. 3 μm sized particles. today, n95 masks are being worn by health-care workers for extended periods of time. this gives rise to very humid conditions. humidity is detrimental to electrostatics. thus, during use, all electrostatics-based masks slowly lose their efficiency. a solution that can help replenish the lost charge on the masks in real time would be desirable. in this section, we provide a proof-of-concept method of keeping the masks charged, which comes as a logical extension of our recharging method. we tested a technique by which the filter material maintains its charge and thus its filtration efficiency. we do this by applying a high electric field in a current limited condition [very low current (few μa), so no risk of discharge or shocking] to the material in situ. figure 6 shows a schematic of the in situ setup: a layer of filtration material (polypropylene mesh) cut from a standard n95 mask including all its layers serves as the filtration medium. this filter is sandwiched between two porous metallic screens, which are connected to a 4 v battery whose voltage is multiplied to 2000 v using a standard voltage multiplier circuit. we use a rubber gasket on both sides of the mask material to provide electrical insulation. the efficacy of the method is indicated in fig. 6 , where the filtration efficiency in the absence of an electric field is 85% ± 1%, which rises to 95% ± 1% upon application of voltage. we have verified that as long as the voltage is applied, the filtration efficiency remains high. since the currents required are extremely small, a large battery is not required, and it is possible that a small compact and practical solution may be feasible. since the loss of electrical charge from the polypropylene filter layer in n95 masks is known to impact the filtration efficiency, scitation.org/journal/phf we investigated the possibility of mask recharging for a few commercially available n95 masks using a simple laboratory setup. our results suggest that it is possible to recharge the masks poststerilization and recover filtration efficiency. however, this is a promising development that merits further research as it may permit multiple or extended use in practical applications. in particular, this method may allow for n95 masks to be used for a considerably longer period of time than is the current norm, which can have a significant effect in hospitals where mask supply is insufficient. additionally, we envisage that our method may find applications in a variety of air filtration contexts. we have focused in this paper on high efficiency respirators for use in preventing disease transmission, but we anticipate applications to heating, ventilation, and air conditioning and industrial filtration as well, where our recharging method would allow for the extended use of electrostatic filters, resulting in reduced cost and waste. furthermore, our in situ field application makes possible high efficiency filtration with undiminished performance over time. in the supplementary material, we outline the design of the low-cost, compact, particle filtration efficiency test setup using a plantower pms 7003 particle concentration sensor air quality monitor chip and a esp8266-based wifi microcontroller that was used for the measurements of particle filtration efficiency reported in this work. all the construction details, diagrams, and source codes for the micro-controller and interface are available in the supplementary material. on respiratory droplets and face masks visualizing the effectiveness of face masks in obstructing respiratory jets sneezing and asymptomatic virus transmission n95 respirators and surgical masks decontamination and reuse of filtering facepiece respirators on coughing and airborne droplet transmission to humans effectiveness of n95 respirator decontamination and reuse against sars-cov-2 virus can n95 respirators be reused after disinfection? how many times? n95 mask decontamination using standard hospital sterilization technologies decontaminating n95 masks with ultraviolet germicidal irradiation does not impair mask efficacy and safety it's not the heat, it's the humidity: effectiveness of a rice cooker-steamer for decontamination of cloth and surgical face masks and n95 respirators reuse of n95 masks decontamination of face masks with steam for mask reuse in fighting the pandemic covid-19: experimental supports efficacy and safety of disinfectants for decontamination of n95 and sn95 filtering facepiece respirators: a systematic review electret air filters weak adhesion at the mesoscale: particles at an interface the mechanics of inhaled pharmaceutical aerosols: an introduction on the minimum efficiency and the most penetrating particle size for fibrous filters some effects of electrostatic charges in fabric filtration physical principles of electrets design of electret polypropylene melt blown air filtration material containing nucleating agent for effective pm2.5 capture electrostatic capture efficiency enhancement of polypropylene electret filters with barium titanate physics of electrophotography gamma irradiation effects on electrets irradiation effects in plexiglas ionic electrets: electrostatic charging of surfaces by transferring mobile ions upon contact household materials selection for homemade cloth face coverings and their filtration efficiency enhancement with triboelectric charging aerosol filtration efficiency of common fabrics used in respiratory cloth masks stability of liquid charged electrets estimation of the size distribution of aerosols produced by jet nebulizers as a function of time electrical conductivity of polypropylene hopping conduction in "pure" polypropylene the authors thank tata memorial hospital, mumbai, for sending us the samples of n95/ffp2 masks for testing our setup. the authors are grateful to paul chaikin for many useful and insightful discussions. e.h. thanks c-camp bengaluru for financial support. the data that support the findings of this study are available within the article. additional drawings and interfacing codes of the mask tester can be found in the github repository. 15 key: cord-260429-5wsj003j authors: kenyon, chris title: widespread use of face masks in public may slow the spread of sars cov-2: an ecological study date: 2020-04-06 journal: nan doi: 10.1101/2020.03.31.20048652 sha: doc_id: 260429 cord_uid: 5wsj003j background the reasons for the large differences between countries in the sizes of their sars cov2 epidemics is unknown. individual level studies have found that the use of face masks was protective for the acquisition and transmission of a range of respiratory viruses including sars cov1. we hypothesized that population level usage of face masks may be negatively associated sars cov2 spread. methods at a country level, linear regression was used to assess the association between covid19 diagnoses per inhabitant and the national promotion of face masks in public (coded as a binary variable), controlling for the age of the covid19 epidemic and testing intensity. results eight of the 49 countries with available data advocated wearing face masks in public: china, czechia, hong kong, japan, singapore, south korea, thailand and malaysia. in multivariate analysis face mask use was negatively associated with number of covid19 cases/inhabitant (coef. -326, 95% ci -601-51, p=0.021). testing intensity was positively associated with covid-19 cases (coef. 0.07, 95% ci 0.05-0.08, p<0.001). conclusion whilst these results are susceptible to residual confounding, they do provide ecological level support to the individual level studies that found face mask usage to reduce the transmission and acquisition of respiratory viral infections. sars cov-2, the viral cause of covid-19, has spread rapidly to over 190 countries 63 [1]. there has, however, been remarkable variation in how extensively it has spread 64 and in the national responses to this spread [1, 2] . for example, although the virus is 65 thought to have first emerged in china, european countries such as italy and spain 66 have reported roughly 30-fold higher number of infections per capita than china [1, 67 2]. understanding the reasons underpinning this heterogeneity in spread is crucial to 68 ongoing prevention efforts. the cornerstones of prevention efforts have included 69 extensive testing, contact tracing and isolation and various forms of social 70 distancing/quarantining [3, 4] . whilst there have been important differences in how 71 these were implemented in different countries, arguably the most striking difference 72 in approach has been in the use of universal face masks in public. whereas a 73 number of predominantly asian countries have promoted this practice, the world 74 health organization (who) and most european and north american countries have 75 not promoted this strategy [5, 6] . the head of the chinese center for disease 76 control and prevention has stated that the biggest mistake that europe and the us 77 were making in tacking covid-19 was their failure to promote the widespread usage 78 of face masks in public [7] . the who argues against universal face mask use 79 based on a lack of evidence to support the practice, as well as a concern that using 80 face masks will provide users with a false sense of security which may result in 81 poorer hand hygiene and hence increased transmission [3, 5, 8] . the us centers for 82 disease control and prevention does not recommend that people who are well wear 83 a face mask to protect themselves from respiratory diseases, including covid-19 84 [5]. in fact, the us surgeon general stated that facemasks "are not effective in 85 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https: //doi.org/10.1101 //doi.org/10. /2020 preventing (the) general public from catching coronavirus" and urged people to 86 stop buying face masks [5] . 87 advocates of universal usage of face masks point to four types of evidence. firstly, 89 sars cov-1 and -2 are spread mainly through contact-and droplet-but also 90 through airborne-transmission [6, 9] . detailed environmental and epidemiological 91 investigations from the large amoy gardens outbreak of sars cov-1 revealed that 92 airborne transmission played an important role in the outbreak [10, 11] . likewise in 93 vitro studies demonstrate that sars cov-2 can be aerosolized and remain viable in 94 the air in this form for at least 3 hours [12] . although viral viability was not assessed, 95 air samples from hospital rooms and toilets used by covid-19 patients as well as 96 from a crowded entrance to a department store tested positive for sars . 97 even if we discount the evidence of airborne transmission, face masks could play a 98 major role in reducing droplet and possibly contact (via reduced digital-oral 99 interactions) transmission. the second type of evidence is that from epidemiological 100 studies showing that masks do provide this protective effect. one systematic review 101 on the efficacy of face masks to prevent influenza, found evidence that face masks 102 were effective in preventing the transmission to others and weaker evidence that 103 they prevented influenza acquisition [14] . likewise, a systematic review and 104 metanalysis in health care workers found that mask wearing was associated with a 105 lower incidence of clinical respiratory infections [15] . a cochrane review of different 106 physical measures to prevent the acquisition of respiratory viruses found face masks 107 to be the most effective of all measures investigated -including social distancing 108 [16]. the results were similar for studies limited to sars cov-1 transmission, with 109 the authors concluding: 'wearing a surgical mask or a n95 mask is the measure with 110 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https://doi.org/10.1101/2020.03.31.20048652 doi: medrxiv preprint the most consistent and comprehensive supportive evidence' [16] . thirdly, there is 111 increasing evidence that a large proportion of sars cov-2 transmission occurs from 112 pauci-or asymptomatic individuals. an estimated 30% of infections are truly 113 asymptomatic and 80% mild infections [17] . evidence is also mounting that infected 114 individuals are infectious prior to the onset of symptoms [18] . taken together these 115 findings provide an explanation for why epidemiological studies have found that 116 nondocumented infections were the infection source for 79% of documented cases 117 in wuhan, china [18] . in this setting limiting masks to confirmed infections is far less 118 likely to have an impact on transmission than universal use. the key argument for 119 universal use is thus preventing transmission and a secondary argument is 120 preventing acquisition [7, 9] . linear regression was used to analyze the association between the independent and 152 dependent variables. we controlled for the fact that sars cov-2 epidemic is at 153 different stages in different countries via two methods. firstly, the 'age of the 154 epidemic' variable was included in all analyses. secondly, we only included countries 155 with at least 500 cumulative cases and countries whose first case was reported 156 before 7 march 2020. countries with missing data were dropped from the analyses. 157 the analysis was performed in stata version 16 (stata corp, college station, tx). 158 although hong kong is a part of china it was included as a separate data point in 159 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https: //doi.org/10.1101 //doi.org/10. /2020 in this ecological study we found that countries that promoted widespread face mask 185 usage had lower cumulative numbers of covid-19 diagnosed after controlling for 186 testing intensity and age of the epidemic. it is important to note that this association 187 may be entirely explained by unmeasured confounders. for example, if countries 188 promoting universal face masking also conducted more effective contact tracing and 189 isolation than other countries and this was responsible for the slower spread, our 190 study design would have falsely attributed this effect to using face masks. we did not 191 have accurate data to control for these confounders. we did however control for 192 testing intensity which is an important potential confounder. we also controlled for 193 the age of the epidemic which is an obvious independent determinant of the size of 194 the epidemic. a further limitation of our study was that we were unable to quantitate cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https: //doi.org/10.1101 //doi.org/10. /2020 there are a number of countries in western european such as italy that have 209 conducted intensive screening, contact tracing, isolation, social distancing and 210 widespread lockdowns and yet have amongst the largest covid-19 epidemics in the 211 world [2] . a striking omission from this response-list if we compare it to the 212 responses in china and other asian countries with lower covid-19 incidence is that 213 the widespread use of face masks in public was not promoted. the only european 214 country to adopt this strategy was czechia, and it did so at a relatively late stage in 215 the epidemic [19, 20] . early indications suggest that despite higher testing rates than 216 the average for western european countries, the number of new infections is lower in 217 czechia [1] . future studies will however be crucial to evaluate the impact of this 218 intervention in czechia and elsewhere. these studies may benefit from including 219 data from taiwan and macau where use of face masks in public has been high and 220 the cumulative number of infections has remained so low that they did not meet the 221 it is likely that a single intervention is not sufficient to suppress the spread of covid-225 19 [2]. the safest approach in the middle of this epidemic may be to introduce the 226 full package of interventions that have been proven to work in asian countries and 227 then scale back according to new findings [3, 9] . our analysis provides further 228 evidence that this package should include widespread usage of face masks in public. 229 currently the only european country that can be considered to be doing this is 230 czechia. 231 232 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https://doi.org/10. 1101 authors' contributions 233 ck conceptualized the study, was responsible for the acquisition, analysis and 234 interpretation of data and wrote the analysis up as a manuscript. 235 236 nil 238 239 the author declares that he/she has no competing interests. 241 242 the analysis involved a secondary analysis of public access ecological level data. as 244 a result, no ethics approval was necessary. 245 246 not applicable 248 nil 250 251 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https://doi.org/10. 1101 . cc-by-nc-nd 4.0 international license it is made available under a author/funder, who has granted medrxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) the copyright holder for this preprint . https://doi.org/10. 1101 european centre for disease prevention and control. situation update worldwide, as 262 of 29 how will country-265 based mitigation measures influence the course of the covid-19 epidemic? the lancet world health organization. coronavirus disease (covid-2019) situation reports. 268 who: geneva report of the who-china joint mission on coronavirus 270 disease rational use of face masks in 272 the covid-19 pandemic. the lancet respiratory medicine mass masking in the covid-19 epidemic: people 274 need guidance. the lancet world health organization. advice on the use of masks in the community, during 278 home care and in health care settings in the context of the novel coronavirus (2019-ncov) 279 outbreak, interim guidance 29 let us not forget the mask in our attempts to stall the 281 spread of covid-19 severe acute respiratory syndrome beyond amoy 283 gardens: completing the incomplete legacy multi-zone modeling of probable sars virus 286 transmission by airflow between flats in block e aerodynamic characteristics 292 and rna concentration of sars-cov-2 aerosol in wuhan hospitals during covid-19 293 outbreak face masks to prevent 295 transmission of influenza virus: a systematic review against respiratory infections in healthcare workers: a systematic review and meta-299 302 physical interventions to interrupt or reduce the spread of respiratory viruses. cochrane 303 estimation 306 of the asymptomatic ratio of novel coronavirus infections (covid-19) substantial undocumented 309 infection facilitates the rapid dissemination of novel coronavirus (sars-cov2) czechs facing up to covid-19 crisis by making masks 312 mandatory. euronews would everyone wearing face masks help us slow the pandemic? : science 314 magazine mass testing, alerts and big fines: the strategies 316 used in asia to slow coronavirus: the guardian key: cord-332512-28utunid authors: eikenberry, steffen e.; mancuso, marina; iboi, enahoro; phan, tin; eikenberry, keenan; kuang, yang; kostelich, eric; gumel, abba b. title: to mask or not to mask: modeling the potential for face mask use by the general public to curtail the covid-19 pandemic date: 2020-04-11 journal: nan doi: 10.1101/2020.04.06.20055624 sha: doc_id: 332512 cord_uid: 28utunid face mask use by the general public for limiting the spread of the covid-19 pandemic is controversial, though increasingly recommended, and the potential of this intervention is not well understood. we develop a compartmental model for assessing the community-wide impact of mask use by the general, asymptomatic public, a portion of which may be asymptomatically infectious. model simulations, using data relevant to covid-19 dynamics in the us states of new york and washington, suggest that broad adoption of even relatively ineffective face masks may meaningfully reduce community transmission of covid-19 and decrease peak hospitalizations and deaths. moreover, mask use decreases the effective transmission rate in nearly linear proportion to the product of mask effectiveness (as a fraction of potentially infectious contacts blocked) and coverage rate (as a fraction of the general population), while the impact on epidemiologic outcomes (death, hospitalizations) is highly nonlinear, indicating masks could synergize with other non-pharmaceutical measures. notably, masks are found to be useful with respect to both preventing illness in healthy persons and preventing asymptomatic transmission. hypothetical mask adoption scenarios, for washington and new york state, suggest that immediate near universal (80%) adoption of moderately (50%) effective masks could prevent on the order of 17--45% of projected deaths over two months in new york, while decreasing the peak daily death rate by 34--58%, absent other changes in epidemic dynamics. even very weak masks (20% effective) can still be useful if the underlying transmission rate is relatively low or decreasing: in washington, where baseline transmission is much less intense, 80% adoption of such masks could reduce mortality by 24--65% (and peak deaths 15--69%), compared to 2--9% mortality reduction in new york (peak death reduction 9--18%). our results suggest use of face masks by the general public is potentially of high value in curtailing community transmission and the burden of the pandemic. the community-wide benefits are likely to be greatest when face masks are used in conjunction with other non-pharmaceutical practices (such as social-distancing), and when adoption is nearly universal (nation-wide) and compliance is high. under the ongoing covid-19 pandemic (caused by the sars-cov-2 coronavirus), recommendations and common practices regarding face mask use by the general public have varied greatly protect against droplets/aerosols and viral transmission, but experimental results by davies et al. [9] suggest that while the homemade masks were less effective than surgical mask, they were still markedly superior to no mask. a clinical trial in healthcare workers [5] showed relatively poor performance for cloth masks relative to medical masks. mathematical modeling has been influential in providing deeper understanding on the transmission mechanisms and burden of the ongoing covid-19 pandemic, contributing to the development of public health policy and understanding. most mathematical models of the covid-19 pandemic can broadly be divided into either population-based, sir (kermack-mckendrick)type models, driven by (potentially stochastic) differential equations [38, 20, 34, 22, 21, 23, 31, 26, 32, 24, 33] , or agent-based models [39, 28, 25, 27, 30] , in which individuals typically interact on a network structure and exchange infection stochastically. one difficulty of the latter approach is that the network structure is time-varying and can be difficult, if not impossible, to construct with accuracy. population-based models, alternatively, may risk being too coarse to capture certain real-world complexities. many of these models, of course, incorporate features from both paradigms, and the right combination of dynamical, stochastic, data-driven, and network-based methods will always depend on the question of interest. in [38] , li et al. imposed a metapopulation structure onto an seir-model to account for travel between major cities in china. notably, they include compartments for both documented and undocumented infections. their model suggests that as many as 86% of all cases went undetected in wuhan before travel restrictions took effect on january 23, 2020. they additionally estimated that, on a per person basis, asymptomatic individuals were only 55% as contagious, yet were responsible for 79% of new infections, given their increased prevalence. the importance of accounting for asymptomatic individuals has been confirmed by other studies ( [39] , [21] ). in their model-based assessment of case-fatality ratios, verity et al. [40] estimated that 40-50% of cases went unidentified in china, as of february 8, 2020, while in the case of the princess diamond cruise ship, 46 .5% of individuals who tested positive for covid-19 were asymptomatic [49] . further, calafiore et al. [21] , using a modified sir-model, estimated that, on average, cases in italy went underreported by a factor of 63, as of march 30, 2020 . several prior mathematical models, motivated by the potential for pandemic influenza, have examined the utility of mask wearing by the general public. these include a relatively simple modification of an sir-type model by brienen et al. [36] , while tracht et al. [37] considered a more complex seir model that explicitly disaggregated those that do and do not use masks. the latter concluded that, for pandemic h1n1 influenza, modestly effective masks (20%) could halve total infections, while if masks were just 50% effective as source control, the epidemic could be essentially eliminated if just 25% of the population wore masks. we adapt these previously developed seir model frameworks for transmission dynamics to explore the potential community-wide impact of public use of face masks, of varying efficacy and compliance, on the transmission dynamics and control of the covid-19 pandemic. in particular, we develop a two-group model, which stratifies the total population into those who habitually do and do not wear face masks in public or other settings where transmission may occur. this model takes the form of a deterministic system of nonlinear differential equations, and explicitly includes asymptomatically-infectious humans. we examine mask effectiveness and coverage (i.e., fraction of the population that habitually wears masks) as our two primary parameters of interest. we explore possible nonlinearities in mask coverage and effectiveness and the interaction of these two parameters; we find that the product of mask effectiveness and coverage level strongly predicts the effect of mask use on epidemiologic outcomes. thus, homemade cloth masks are best deployed en masse to benefit the population at large. there is also a potentially strong nonlinear effect of mask use on epidemiologic outcomes of cumulative death and peak hospitalizations. we note a possible temporal effect: delaying mass mask adoption too long may undermine its efficacy. moreover, we perform simulated case studies using mortality data for new york and washington state. these case studies likewise suggest a beneficial role to mass adoption of even poorly effective masks, with the relative benefit likely greater in washington state, where baseline transmission is less intense. the absolute potential for saving lives is still, however, greater under the more intense transmission dynamics in new york state. thus, early adoption of masks is useful regardless of transmission intensities, and should not be delayed even if the case load/mortality seems relatively low. in summary, the benefit to routine face mask use by the general public during the covid-19 pandemic remains uncertain, but our initial mathematical modeling work suggests a possible strong potential benefit to near universal adoption of even weakly effective homemade masks that may synergize with, not replace, other control and mitigation measures. we consider a baseline model without any mask use to form the foundation for parameter estimation and to estimate transmission rates in new york and washington state; we also use this model to determine the equivalent transmission rate reductions resulting from public mask use in the full model. we use a deterministic susceptible, exposed, symptomatic infectious, hospitalized, asymptomatic infectious, and recovered modeling framework, with these classes respectively denoted s(t), e(t), i(t), h(t), a(t), and r(t); we also include d(t) to track cumulative deaths. we assume that some fraction of detected infectious individuals progress to the hospitalized class, h(t), where they are unable to pass the disease to the general public; we suppose that some fraction of hospitalized patients ultimately require critical care (and may die) [35] , but do not explicitly disaggregate, for example, icu and non-icu patients. based on these assumptions and simplifications, the basic model for the transmission dynamics of covid-19 is given by the following deterministic system of nonlinear differential equations: where is the total population in the community, and β(t) is the baseline infectious contact rate, which is assumed to vary with time in general, but typically taken fixed. additionally, η accounts for the relative infectiousness of asymptomatic carriers (in comparison to symptomatic carriers), σ is the transition rate from the exposed to infectious class (so 1/σ is the disease incubation period), α is the fraction of cases that are symptomatic, ϕ is the rate at which symptomatic individuals are hospitalized, δ is the disease-induced death rate, and γ a , γ i and γ h are recovery rates for the subscripted population. we suppose hospitalized persons are not exposed to the general population. thus, they are excluded from the tabulation of n , and do not contribute to infection rates in the general community. this general modeling framework is similar to a variety of seir-style models recently employed in [38, 39] , for example. for most results in this paper, we use let β(t) ≡ β 0 . however, given ongoing responses to the covid-19 pandemic in terms of voluntary and mandated social distancing, etc., we also consider the possibility that β varies with time and adopt the following functional form from tang et al. [34] , with the modification that contact rates do not begin declining from the initial contact rate, β 0 , until time t 0 , where β min is the minimum contact rate and r is the rate at which contact decreases. the incubation period for covid-19 is estimated to average 5.1 days [19] , similar to other model-based estimates [38] , giving σ = 1/5.1 day −1 . some previous model-based estimates of infectious duration are on the order of several days [38, 39, 34] , with [34] giving about 7 days for asymptomatic individuals to recover. however, the clinical course of the disease is typically much longer: in a study of hospitalized patients [35] , average total duration of illness until hospital discharge or death was 21 days, and moreover, the median duration of viral shedding was 20 days in survivors. the effective transmission rate (as a constant), β 0 , ranges from around 0.5 to 1.5 day −1 in prior modeling studies [44, 43, 38] , and typically trends down with time [34, 38] . we have left this as a free parameter in our fits to washington and new york state mortality data, and find β 0 ≈ 0.5 and β 0 ≈ 1.4 day −1 for these states, respectively, values this range. the relative infectiousness of asymptomatic carriers, η, is not known, although ferguson et al. [39] estimated this parameter at about 0.5, and li et al. [38] gave values of 0.42-0.55. the fraction of cases that are symptomatic, α, is also uncertain, with li et al. [38] suggesting an overall case reporting rate of just 14% early in the outbreak in china, but increasing to 65-69% later; further, α = 2/3 was used in [39] . in the case of the diamond princess cruise ship [49] , 712 (19.2%) passengers and crews tested positive for sars-cov-2, with 331 (46.5%) asymptomatic at the time of testing. therefore, we choose α = 0.5 as our default. given an average time from symptom onset to dyspnea of 7 days in [35] , and 9 days to sepsis, a range of 1-10 days to hospitalization, a midpoint of 5 days seems reasonable (see also [39] ); ϕ ≈ 0.025 day −1 is consistent with on the order of 5-15% of symptomatic patients being hospitalized. if about 15% of hospitalized patients die [39] , then δ ≈ 0.015 day −1 (based on γ h = 1/14 day −1 ). we assume that some fraction of the general population wears masks with uniform inward efficiency (i.e., primary protection against catching disease) of ϵ i , and outward efficiency (i.e., source control/protection against transmitting disease) of ϵ o . we disaggregate all population variables into those that typically do and do not wear masks, respectively subscripted with u and m . based on the above assumptions and simplifications, the extended multi-group model for covid-19 (where members of the general public wear masks in public) is given by: all rights reserved. no reuse allowed without permission. the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint (which was not peer-reviewed) is (2.25) while much more complex than the baseline model, most of the complexity lies in what are essentially bookkeeping terms. we also consider a reduced version of the above model (equations not shown), such that only symptomatically infected persons wear a mask, to compare the consequences of the common recommendation that only those experiencing symptoms (and their immediate caretakers) wear masks with more general population coverage. we assume a roughly linear relationship between the overall filtering efficiency of a mask and clinical efficiency in terms of either inward efficiency (i.e., effect on ϵ i ) or outward efficiency (ϵ o ), based on [36] . the fit factor for homemade masks averaged 2 in [9] , while the fit factor averaged 5 for surgical masks. when volunteers coughed into a mask, depending upon sampling method, the number of colony-forming units resulting varied from 17% to 50% for homemade masks and 0-30% for surgical masks, relative to no mask [9] . surgical masks reduced p. aeruginosa infected aerosols produced by coughing by over 80% in cystic fibrosis patients in [14] , while surgical masks reduced cfu count by >90% in a similar study [13] . n95 masks were more effective in both studies. homemade teacloth masks had an inward efficiency between 58 and 77% over 3 hours of wear in [12] , while inward efficiency ranged 72-85% and 98-99% for surgical and n95-equivalent masks. outward efficiency was marginal for teacloth masks, and about 50-70% for medical masks. surgical masks worn by tuberculosis patients also reduced the infectiousness of hospital ward air in [15] , and leung et al. [42] very recently observed surgical masks to decrease infectious aerosol produced by individuals with seasonal coronaviruses. manikin studies seem to recommend masks as especially valuable under coughing conditions for both source control [11] and prevention [10] . we therefore estimate that inward mask efficiency could range widely, anywhere from 20-80% for cloth masks, with ≥50% possibly more typical (and higher values are possible for well-made, tightly fitting masks made of optimal materials), 70-90% typical for surgical masks, and >95% typical for properly worn n95 masks. outward mask efficiency could range from practically zero to over 80% for homemade masks, with 50% perhaps typical, while surgical masks and n95 masks are likely 50-90% and 70-100% outwardly protective, respectively. we use state-level time series for cumulative mortality data compiled by center for systems science and engineering at johns hopkins university [47] , from january 22, 2020, through april 2, 2020, to calibrate the model initial conditions and infective contact rate, β 0 , as well as β min when β(t) is taken as an explicit function of time. other parameters are fixed at default values in table 1 . parameter fitting was performed using nonlinear least squares algorithm implemented using the lsqnonlin function in matlab. we consider two us states in particular as case studies, new york and washington, and total population data for each state was defined according to us census data for july 1, 2019 [48] . closed-form expressions for the basic reproduction number, r 0 , for the baseline model without masks and the full model with masks are given, for β(t) ≡ β 0 , in appendix a and b, respectively. we run simulated epidemics using either β 0 = 0.5 or 1.5 day −1 , with other parameters set to the defaults given in table 1 . these parameter sets give epidemic doubling times early in time (in terms of cumulative cases and deaths) of approximately seven or three days, respectively, corresponding to case and mortality doubling times observed (early in time) in washington and new york state, respectively. we use as initial conditions a normalized population of 1 million persons, all of whom are initially susceptible, except 50 initially symptomatically infected (i.e., 5 out 100,000 is the initial infection rate), not wearing masks. we choose some fraction of the population to be initially in the masked class ("mask coverage"), which we also denote π, and assume ϵ o = ϵ i = ϵ. the epidemic is allowed to run its course (18 simulated months) under constant conditions, and the outcomes of interest are peak hospitalization, cumulative deaths, and total recovered. these results are normalized against the counterfactual of no mask coverage, and results are presented as heat maps in figure 1 . note that the product ϵ × π predicts quite well the effect of mask deployment: figure 1 also shows (relative) peak hospitalizations and cumulative deaths as functions of this product. there is, however, a slight asymmetry between coverage and efficacy, such that increasing coverage of moderately effective masks is generally more useful than increasing the effectiveness of masks from a starting point of moderate coverage. figure 2 : equivalent β 0 ,β 0 (infectious contact rate) under baseline model dynamics as a function of mask coverage × efficacy, with the left panel giving the absolute value, and the right giving the ratio ofβ 0 to the true β 0 in the simulation with masks. that is, simulated epidemics are run with mask coverage and effectiveness ranging from 0 to 1, and the outcomes are tracked as synthetic data. the baseline model without mask dynamics is then fit to this synthetic data, with β 0 the trainable parameter; the resulting β 0 is theβ 0 . this is done for simulated epidemics with a true β 0 of 1.5, 1, or 0.5 day −1 . we run the simulated epidemics described, supposing the entire population is unmasked until mass mask adoption after some discrete delay. the level of adoption is also fixed as a constant. we find that a small delay in mask adoption (without any changes in β) has little effect on peak hospitalized fraction or cumulative deaths, but the "point of no return" can rapidly be crossed, if mask adoption is delayed until near the time at which the epidemic otherwise crests. this general pattern holds regardless of β 0 , but the point of no return is further in the future for smaller β 0 . the relationship between mask coverage, efficacy, and metrics of epidemic severity considered above are highly nonlinear. the relationship between β 0 (the infectious contact rate) and such metrics is similarly nonlinear. however, incremental reductions in β 0 , due to social distances measures, etc., can ultimately synergize with other reductions to yield a meaningfully effect on the epidemic. therefore, we numerically determine what the equivalent change in β 0 under the baseline would have been under mask use at different coverage/efficacy levels, and we denote the equivalent β 0 value asβ 0 . that is, we numerically simulate an epidemic with and without masks, with a fixed β 0 . then, we fit the baseline model to this (simulated) case data, yielding a new equivalent β 0 , β 0 . an excellent fit givingβ 0 can almost always be obtained, though occasionally results are extremely sensitive to β 0 for high mask coverage/efficacy, yielding somewhat poorer fits. results 9 all rights reserved. no reuse allowed without permission. the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint (which was not peer-reviewed) is . https://doi.org/10.1101/2020.04.06.20055624 doi: medrxiv preprint are summarized in figure 2 , where theβ 0 values obtained and the relative changes in equivalent β (i.e., (β 0 ) / (β 0 )) are plotted as functions of efficacy times coverage, ϵ × π, under simulated epidemics with three baseline (true) β 0 values. from figure 2 , we see that even 50% coverage with 50% effective masks roughly halves the effective disease transmission rate. widespread adoption, say 80% coverage, of masks that are only 20% effective still reduces the effective transmission rate by about one-third. figure 3 demonstrates the effect of mask coverage on peak hospitalizations, cumulative deaths, and equivalent β 0 values when either ϵ o = 0.2 and ϵ i = 0.8, or visa versa (and for simulated epidemics using either β 0 = 0.5 or 1.5 day −1 . these results suggest that, all else equal, the protection masks afford against acquiring infection (ϵ o ) is actually slightly more important than protection against transmitting infection (ϵ i ), although there is overall little meaningful asymmetry. finally, we consider numerical experiments where masks are given to all symptomatically infected persons, whether they otherwise habitually wear masks or not (i.e., both i u and i m actually wear masks). we explore how universal mask use in symptomatically infected persons interacts with mask coverage among the general population; we let ϵ i o represent the effectiveness of masks in the symptomatic, not necessarily equal to ϵ o . we again run simulated epidemics with no masks, universal masks among the symptomatic, and then compare different levels of mask coverage in the general (asymptomatic) population. in this section, we use equivalent β 0 as our primary metric. figure 4 shows how this metric varies as a function of the mask effectiveness given to symptomatic persons, along with the coverage and effectiveness of masks worn by the general public. we also explore how conclusions vary when either 25%, 50%, or 75% of infectious covid-19 patients are asymptomatic (i.e., we vary α). unsurprisingly, the greater the proportion of infected people are asymptomatic, the more benefit there is to giving the general public masks in addition to those experiencing symptoms. fitting to cumulative death data, we use the baseline model to determine the best fixed β 0 and i(0) for cumulative death data for new york and washington state. we use new york state data beginning on march 1, 2020, through april 2, 2020, and washington state data from we fix r and t 0 , as it is not possible to uniquely identify r, t 0 and β min , from death or case data alone (see e.g., [46] on identifiability problems). figure 5 gives cumulative death and case data versus the model predictions for the two states, and for the two choices of β(t). note that while modeled and actual cumulative deaths match well, model-predicted cases markedly exceed reported cases in the data, consistent with the notion of broad underreporting. we then consider either fixed β 0 or time-varying β(t), according to the parameters above, in combination with the following purely hypothetical scenarios in each state. all rights reserved. no reuse allowed without permission. the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint (which was not peer-reviewed) is . 1. no masks, epidemic runs its course unaltered with either β(t) ≡ β 0 fixed or β(t) variable as described above. 2. the two β scenarios are considered in combination with: (1) weak, moderate, or strong deployment of masks, such that π = 0.2, 0.5, or 0.8; and (2) weak, moderate, or strong masks, such that ϵ = 0.2, 0.5, or 0.8. no masks are used up until april 2, 2020, and then these coverage levels are instantaneously imposed. this yields 18 scenarios in all (nine mask coverage/efficacy scenarios, plus two underlying trends). following the modeled imposition of masks on april 2, 2020, the scenarios are run for 60 additional simulated days. figures 6 and 8 summarize the future modeled death toll in each city under the 18 different scenarios, along with historical mortality data. figures 7 and 9 show modeled daily death rates, with deaths peaking sometime in late april in new york state under all scenarios, while deaths could peak anywhere from mid-april to later than may, for washington state. we emphasize that these are hypothetical and exploratory results, with possible death tolls varying dramatically based upon the future course of β(t). however, the results do suggest that even modestly effective masks, if widely used, could help "bend the curve," with the relative benefit greater in combination with a lower baseline β 0 or stronger underlying trend towards smaller β(t) (i.e., in washington vs. new york). this study aims to contribute to this debate by providing realistic insight into the communitywide impact of widespread use of face masks by members of the general population. we designed a mathematical model, parameterized using data relevant to covid-19 transmission dynamics in two us states (new york and washington). the model suggests a nontrivial .... there is considerable ongoing debate on whether to recommend general public face mask use (likely mostly homemade cloth masks or other improvised face coverings) [51] , and while the situation is in flux, more authorities are recommending public mask use, though they continue to (rightly) cite appreciable uncertainty. with this study, we hope to help inform this debate by providing insight into the potential community-wide impact of widespread face mask use by members of the general population. we have designed a mathematical model, parameterized using data relevant to covid-19 transmission dynamics in two us states (new york and washington), and our model suggests nontrivial and possibly quite strong benefit to general face mask use. the population-level benefit is greater the earlier masks are adopted, and at least some benefit is realized across a range of epidemic intensities. moreover, even if they have, as a sole intervention, little influence on epidemic outcomes, face masks decrease the equivalent effective transmission rate (β 0 in our model), and thus can stack with other interventions, including social distancing and hygienic measures especially, to ultimately drive nonlinear decreases in epidemic mortality and healthcare system burden. it bears repeating that our model results are consistent with the idea that face masks, while no panacea, may synergize with other non-pharmaceutical control measures and should be used in combination with and not in lieu of these. under simulated epidemics, the effectiveness of face masks in altering the epidemiologic outcomes of peak hospitalization and total deaths is a highly nonlinear function of both mask efficacy and coverage in the population (see figure 1) , with the product of mask efficacy and coverage a good one-dimensional surrogate for the effect. we have determined how mask use in the full model alters the equivalent β 0 , denotedβ 0 , under baseline model (without masks), finding this equivalentβ 0 to vary nearly linearly with efficacy × coverage ( figure 2 ). masks alone, unless they are highly effective and nearly universal, may have only a small effect (but still nontrivial, in terms of absolute lives saved) in more severe epidemics, such as the ongoing epidemic in new york state. however, the relative benefit to general masks use may increase with other decreases in β 0 , such that masks can synergize with other public health measures. thus, it is important that masks not be viewed as an alternative, but as a complement, to other public health control measures (including non-pharmaceutical interventions, such as social distancing, self-isolation etc.). delaying mask adoption is also detrimental. these factors together indicate that even in areas or states where the covid-19 burden is low (e.g. the dakotas), early aggressive action that includes face masks may pay dividends. these general conclusions are illustrated by our simulated case studies, in which we have tuned the infectious contact rate, β (either as fixed β 0 or time-varying β(t)), to cumulative mortality data for washington and new york state through april 2, 2020, and imposed hypothetical mask adoption scenarios. the estimated range for β is much smaller in washington state, consistent with this state's much slower epidemic growth rate and doubling time. model fitting also suggests that total symptomatic cases may be dramatically undercounted in both areas, consistent with prior conclusions on the pandemic [38] . simulated futures for both states suggest that broad adoption of even weak masks use could help avoid many deaths, but the greatest relative death reductions are generally seen when the underlying transmission rate also falls or is low at baseline. considering a fixed transmission rate, β 0 , 80% adoption of 20%, 50%, and 80% effective masks reduces cumulative relative (absolute) mortality by 1.8% (4,419), 17% (41, 317) , and 55% (134,920), respectively, in new york state. in washington state, relative (absolute) mortality reductions are dramatic, amounting to 65% (22, 262) , 91% (31, 157) , and 95% (32,529). when β(t) varies with time, new york deaths reductions are 9% (21,315), 45% (103,860), and 74% (172,460), while figures for washington are 24% (410), 41% (684), and 48% (799). in the latter case, the epidemic peaks soon even without masks. thus, a range of outcomes are possible, but both the absolute and relative benefit to weak masks can be quite large; when the relative benefit is small, the absolute benefit in terms of lives is still highly nontrivial. most of our model projected mortality numbers for new york and washington state are quite high (except for variable β(t) in washington), and likely represent worst-case scenarios as they primarily reflect β values early in time. thus, they may be dramatic overestimates, depending upon these states' populations ongoing responses to the covid-19 epidemics. nevertheless, the estimated transmission values for the two states, under fixed and variable β(t) represent a broad range of possible transmission dynamics, are within the range estimated in prior studies [43, 44, 38] , and so we may have some confidence in our general conclusions on the possible range of benefits to masks. note also that we have restricted our parameter estimation only to initial conditions and transmission parameters, owing to identifiability problems with more complex models and larger parameter groups (see e.g. [46] ). for example, the same death data may be consistent with either a large β 0 and low δ (death rate), or visa versa. considering the subproblem of general public mask use in addition to mask use for source control by any (known) symptomatic person, we find that general face mask use is still highly beneficial (see figure 4) . unsurprisingly, this benefit is greater if a larger proportion of infected people are asymptomatic (i.e., α in the model is smaller). moreover, it is not the case that masks are helpful exclusively when worn by asymptomatic infectious persons for source control, but provide benefit when worn by (genuinely) healthy people for prevention as well. indeed, if there is any asymmetry in outward vs. inward mask effectiveness, inward effectiveness is actually slightly preferred, although the direction of this asymmetry matters little with respect to overall epidemiologic outcomes. at least one experimental study [11] does suggest that masks may be superior at source control, especially under coughing conditions vs. normal tidal breathing and so any realized benefit of masks in the population may still be more attributable to source control. this is somewhat surprising, given that ϵ o appears more times than ϵ i in the model terms giving the forces of infection, which would suggest outward effectiveness to be of greater import at first glance. our conclusion runs counter to the notion that general public masks are primarily useful in preventing asymptomatically wearers from transmitting disease: masks are valuable as both source control and primary prevention. this may be important to emphasize, as some people who have self-isolated for prolonged periods may reasonably believe that the chance they are asymptomatically infected is very low and therefore do not need a mask if they venture into public, whereas our results indicate they (and the public at large) still stand to benefit. our theoretical results still must be interpreted with caution, owing to a combination of potential high rates of noncompliance with mask use in the community, uncertainty with respect to the intrinsic effectiveness of (especially homemade) masks at blocking respiratory droplets and/or aerosols, and even surprising amounts of uncertainty regarding the basic mechanisms for respiratory infection transmission [4, 41] . several lines of evidence support the notion that masks can interfere with respiratory virus transmission, including clinical trials in healthcare workers [3, 4] , experimental studies as reviewed [12, 10, 9, 15, 11] , and case control data from the 2003 sars epidemic [1, 2] . given the demonstrated efficacy of medical masks in healthcare workers [3] , and their likely superiority over cloth masks in [5] , it is clearly essential that healthcare works be prioritized when it comes to the most effective medical mask supply. fortunately, our theoretical results suggest significant (but potentially highly variable) value even to low quality masks when used widely in the community. with social distancing orders in place, essential service providers (such as retail workers, emergency services, law enforcement, etc.) represent a special category of concern, as they represent a largely unavoidable high contact node in transmission networks: individual publicfacing workers may come into contact with hundreds or thousands of people in the course of a day, in relatively close contact (e.g. cashiers). such contact likely exposes the workers to many asymptomatic carriers, and they may in turn, if asymptomatic, expose many susceptible members of the general public to potential transmission. air exposed to multiple infectious persons (e.g. in grocery stores) could also carry a psuedo-steady load of infectious particles, for which masks would be the only plausible prophylactic [10] . thus, targeted, highly effective mask use by service workers may be reasonable. we are currently extending the basic model framework presented here to examine this hypothesis. in conclusion, our findings suggest that face mask use should be as nearly universal (i.e., nation-wide) as possible and implemented without delay, even if most mask are homemade and of relatively low quality. this measure could contribute greatly to controlling the covid-19 pandemic, with the benefit greatest in conjunction with other non-pharmaceutical interventions that reduce community transmission. despite uncertainty, the potential for benefit, the lack of obvious harm, and the precautionary principle lead us to strongly recommend as close to universal (homemade, unless medical masks can be used without diverting healthcare supply) mask use by the general public as possible. the basic reproduction number of the model, denoted by r 0 , is given by . (4.2) risk factors for sars among persons without known contact with sars patients sars transmission, risk factors, and prevention in hong kong effectiveness of masks and respirators against respiratory infections in healthcare workers: a systematic review and meta-analysis the efficacy of medical masks and respirators against respiratory infection in healthcare workers a cluster randomised trial of cloth masks compared with medical masks in healthcare workers face mask use and control of respiratory virus transmission in households facemasks and hand hygiene to prevent influenza transmission in households: a cluster randomized trial surgical mask to prevent influenza transmission in households: a cluster randomized trial testing the efficacy of homemade masks: would they protect in an influenza pandemic effectiveness of facemasks to reduce exposure hazards for airborne infections among general populations respiratory source control using a surgical mask: an in vitro study professional and home-made face masks reduce exposure to respiratory infections among the general population face masks reduce the release of pseudomonas aeruginosa cough aerosols when worn for clinically relevant periods surgical masks reduce airborne spread of pseudomonas aeruginosa in colonized patients with cystic fibrosis surgical face masks worn by patients with multidrug-resistant tuberculosis: impact on infectivity of air on a hospital ward modes of transmission of virus causing covid-19: implications for ipc precaution recommendations: scientific brief aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 air, surface environmental, and personal protective equipment contamination by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) from a symptomatic patient the incubation period of coronavirus disease 2019 (covid-19) from publicly reported confirmed cases: estimation and application. annals of internal medicine nowcasting and forecasting the potential domestic and international spread of the 2019-ncov outbreak originating in wuhan, china: a modelling study a modified sir model for the covid-19 contagion in italy early dynamics of transmission and control of covid-19: a mathematical modelling study. the lancet infectious diseases a simple stochastic sir model for covid 19 infection dynamics for karnataka: learning from europe data-based analysis, modelling and forecasting of the novel coronavirus (2019-ncov) outbreak covid-19 spread: reproduction of data and prediction using a sir model on euclidean network statistics based predictions of coronavirus 2019-ncov spreading in mainland china modelling transmission and control of the covid-19 pandemic in australia the role of age distribution and family structure on covid-19 dynamics: a preliminary modeling assessment for hubei and lombardy. available at ssrn 3564800 transmission of 2019-ncov infection from an asymptomatic contact in germany the networks infection contagious diseases positioning system (nicdp-system): the case of wuhan-covid-19 inferring covid-19 spreading rates and potential change points for case number forecasts covid-19 infection and recovery in various countries: modeling the dynamics and evaluating the non-pharmaceutical mitigation scenarios controlling the transmission dynamics of covid-19 an updated estimation of the risk of transmission of the novel coronavirus (2019-ncov) clinical course and risk factors for mortality of adult inpatients with covid-19 in wuhan, china: a retrospective cohort study the effect of mask use on the spread of influenza during a pandemic mathematical modeling of the effectiveness of facemasks in reducing the spread of novel influenza a (h1n1) substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (sars-cov2) impact of non-pharmaceutical interventions (npis) to reduce covid19 mortality and healthcare demand estimates of the severity of coronavirus disease 2019: a model-based analysis. the lancet infectious diseases turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of covid-19 & seto, w. h. respiratory virus shedding in exhaled breath and efficacy of face masks modelling the epidemic trend of the 2019 novel coronavirus outbreak in china. biorxiv. the baseline model parameters are listed in table 1, with approximate ranges from the literature based on both clinical and modeling studies novel coronavirus 2019-ncov: early estimation of epidemiological parameters and epidemic predictions uncertainties about the transmission routes of 2019 novel coronavirus. influenza and other respiratory viruses why is it difficult to accurately predict the covid-19 epidemic covid-19. github repository annual estimates of the resident population for the united states, regions, states public health responses to covid-19 outbreaks on cruise ships-worldwide response to covid-19 in taiwan: big data analytics, new technology, and proactive testing covid-19 epidemic: disentangling the re-emerging controversy about medical facemasks from an epidemiological perspective on the definition and the computation of the basic reproduction ratio r0 in models for infectious diseases in heterogeneous populations reproduction numbers and sub-threshold endemic equilibria for compartmental models of disease transmission one of the authors (abg) acknowledge the support, in part, of the simons foundation (award #585022) and the national science foundation (award 1917512). all rights reserved. no reuse allowed without permission. the basic reproduction number for both the baseline and the full model is for the special case when β(t) ≡ β 0 . the local stability of the dfe is explored using the next generation operator method [52, 53] . using the notation in [53] , it follows that the matrices f of new infection terms and v of the remaining transfer terms associated with the version of the model are given, respectively, bythe basic reproduction number of the model, denoted by r 0 , is given by the local stability of the dfe is explored using the next generation operator method [52, 53] .using the notation in [53] , it follows that the matrices f of new infection terms and v of the remaining transfer terms associated with the version of the model are given, respectively, by key: cord-266377-3krv9ekb authors: nakayachi, kazuya; ozaki, taku; shibata, yukihide; yokoi, ryosuke title: why do japanese people use masks against covid-19, even though masks are unlikely to offer protection from infection? date: 2020-08-04 journal: front psychol doi: 10.3389/fpsyg.2020.01918 sha: doc_id: 266377 cord_uid: 3krv9ekb wearing masks against 2019 coronavirus (covid-19) is beneficial in suppressing pandemic spread, not through preventing the wearer from being infected but by preventing the wearer from infecting others. despite not providing much protection, the custom of wearing masks has prevailed in east asia from the early stages of the pandemic, especially in japan, to such an extent that it caused a shortfall in supply. why do many japanese people wear masks during the covid-19 pandemic, even though masks are unlikely to prevent them from getting infected? we examined six possible psychological reasons for wearing masks: three involved expectations about the risk of infection and three involved other driving psychological forces. the results of our nationwide survey revealed that people conformed to societal norms in wearing masks and felt relief from anxiety when wearing masks. however, risk reduction expectations did not affect mask usage. the social psychological motivations successfully explained much about mask usage. our findings suggest that policymakers responsible for public health should consider social motivations when implementing public strategies to combat the covid-19 pandemic. why do many japanese people wear masks during the 2019 coronavirus (covid-19) pandemic, even though masks are unlikely to prevent them from getting infected? wearing masks against covid-19 is beneficial in suppressing pandemic spread, not through preventing the wearer from being infected but by preventing the wearer from infecting others, according to suggestions from the world health organization (who, 2020a,b,c) and lessons from previous pandemics, such as the 2003 severe acute respiratory syndrome (sars) pandemic and the 2009 influenza a virus subtype h1n1 pandemic (mniszewski et al., 2014; leung et al., 2020) . the director-general of the chinese center for disease control and prevention also stated that, "not wearing masks to protect against coronavirus is a "big mistake"" in terms of preventing the spread of infection, but not in terms of personal infection prevention (cohen, 2020) . despite not providing much protection, the custom of wearing masks has prevailed in east asia from the early stages of the pandemic, especially in japan (yamagata et al., 2020) ; to such an extent that it caused a shortfall in supply (bbc, 2020) . what are the psychological reasons prompting an individual to take a measure from which they cannot directly benefit? individuals' cumulative actions are beneficial to society, but not directly beneficial to themselves. in our survey, we examined six possible psychological reasons for wearing masks: three involved individuals' perception of the severity of the disease and the efficacy of masks in reducing the infection risks both for themselves and for others; the remaining three involved other psychological driving forces. the altruistic intention could be the primary reason for wearing masks, to avoid spreading the disease to others. although perfect altruism seems impossible, people often behave to benefit others at a certain cost to themselves (batson et al., 1981; schwartz and howard, 1981) . altruistic risk reduction to others is favorable for the whole of society; however, does such an altruistic motivation work well during a dreadful pandemic? another motivation to reduce risk is self-interest that is, protecting oneself against the virus, even if this is a misperception. if people are confident that masks will protect them against infection, they are likely to wear them. perceived seriousness of the disease could be another reason to wear a mask. the more an individual sees the disease as serious, the higher is the person's motivation to take action. theories of protection behavior such as the protection motivation theory (rogers, 1975 (rogers, , 1983 and the protective action decision model perry, 1992, 2012) posit that people cope well with risks when they perceive a threat as serious, and take action when they perceive the action as effective in mitigating associated damage. those three reasons are predicated on reducing the risk of infection to others or to oneself. however, people's actions are not necessarily connected to the original motivating purpose of the action. three factors could result in collective maskwearing even in the absence of an intention to avoid risk. people may simply conform to others' behavior, through perceiving a type of social norm in observing others wearing masks (i.e., a descriptive norm; cialdini et al., 1990; lapinski and rimal, 2005) . during the 2009 h1n1 epidemic, wearing masks became a norm in hong kong (lau et al., 2010) . ambiguous situations or states of anxiety -which are central characteristics of the present emergency -can also boost conformity (taylor, 1953; crutchfield, 1955) . wearing masks might relieve people's anxiety regardless of masks' realistic capacity to prevent infection. another factor that may explain the decision to wear a mask is the affect heuristic, which predicts that our intuitive feelings toward activities or technologies define our perceptions of benefit as well as risk (finucane et al., 2000; slovic et al., 2002 slovic et al., , 2004 . many people might wear masks simply because doing so promotes positive feelings, irrespective of masks' objective effectiveness in reducing risks. finally, a single-action bias in which people tend to adopt a single action against a risk may also be at play (weber, 1997 (weber, , 2006 . the pandemic compels people to cope as well as they can, and wearing masks may be an accessible and convenient means to deal with the hardship. our research examined how these six broad psychological reasons may explain the japanese use of masks against covid-19. identifying influential psychological predictors can help us to improve our collective solutions. we recruited participants through cross marketing, a leading market research company in japan. participants were recruited through electronic mail and accessed the designated website to participate in the survey. they earned small amounts of points for participating, with cash or a gift card awarded based on the number of accumulated points. we included only those who consented to participate in the study. there were 515 female participants and 485 male participants; 11.5% of female participants were in their 20s, 14.6% were in their 30s, 16.9% were in their 40s, 14.8% were in their 50s, 31.5% were in their 60s, 10.1% were in their 70s, and 0.8% were 80 years of age or older; 12.4% of male participants were in their 20s, 15.7% were in their 30s, 18.8% were in their 40s, 15.9% were in their 50s, 26.8% were in their 60s, 9.9% were in their 70s, and 0.6% were 80 years of age or older. the mean age of participants was 51.1 (sd = 15.5). the sample closely reflected the general population in japan for sex, age, and residential area (the whole of japan is divided into seven regions). this survey was conducted between march 26 and 31, 2020. during this period, the total number of people infected with the 2019 novel coronavirus in japan increased from 1,253 to 1,887, and the government announced that japanese people should only go out if the trip was necessary or urgent. participants were asked about covid-19 and the efficacy of masks, responding to six items using a five-point likert scale (1 = not at all to 5 = very much). the items were the following: • perceived severity (severity): do you think that your disease condition would be serious if you had covid-19? • perceived self-efficacy of wearing a mask for protection (protection): do you think that wearing a mask will keep you from being infected? • perceived efficacy of wearing a mask for preventing spread (prevention): do you think that people who have covid-19 can avoid infecting others by wearing masks? • perceived norm to wear masks (norm): when you see other people wearing masks, do you think that you should wear a mask? • feeling relief when wearing masks (relief): do you think that you can ease your anxiety by wearing a mask? • impulse to take whatever actions are necessary (impulsion): do you think that you should "do whatever you can" to avoid covid-19? participants were also asked about their frequency of wearing masks during this outbreak, using a three-point scale (1 = i have not worn one at all, 2 = i have sometimes worn one, and 3 = i have usually worn one). figure 1 shows the results of participants' mask usage, indicating that more than half usually wore masks from the beginning of the pandemic (yamagata et al., 2020) . table 1 shows the descriptive statistics and correlations among variables regarding mask usage. we computed the product of severity and efficacy as an indicator of the effectiveness of wearing a mask (effectiveness). reversed efficacy implies the inefficacy of wearing masks; thus, the product of severity and inefficacy is the perceived risk of infection under the mask-wearing condition (ineffectiveness). all psychological motivations were positively correlated to mask usage. mask usage was regressed by the six psychological reasons to wear masks, removing the products above to avoid multicollinearity, and in order to compare the explanatory power of the psychological reasons. as indicated in table 2 , a powerful correlation was found between perception of norms and mask usage; conformity to the mask norm was the most influential determinant, given the standardized coefficient. feeling relief from anxiety by wearing masks also promoted mask use. by contrast, frequency of mask usage depended much less on the participants' perceived severity of the disease and the efficacy of masks in reducing infection risk both for themselves and for others. this implies that the perceived threat and risk reduction intentions were not the primary reason for wearing masks. our analysis did not find a significant effect of willingness to take any action necessary. these six psychological factors explained one-third of the total variance in the frequency of wearing masks. even though the expectation of risk reduction (personal or collective) explained only small portion of mask usage, motivations superficially irrelevant to disease mitigation strongly promoted mask-wearing behavior; conformity to the social norm was the most prominent driving force for wearing masks. this tendency to conform was reported narratively during the h1n1 epidemic (lau et al., 2010) , but our research empirically confirmed the association. as mentioned in the context of the sars pandemic, wearing masks can be a symbol of collective confrontation against a pandemic, even though its effectiveness in reducing personal risk remains uncertain (syed et al., 2003) . to establish effective strategies against covid-19, social motivations such as conformity should be used to good advantage and embedded in nudge approaches. nudges utilizing social norms are widely accepted and recommended by social scientists (nyborg et al., 2016) ; therefore, we encourage policymakers to apply the effects of the social norm on the wearing of masks to promote collective efforts to combat covid-19. from the perspective of canonical models of risk-coping behavior, mitigation should be driven by intentions of risk reduction. however, our findings of the modest association between risk reduction expectations and behavior illustrate the complexities of risk-coping. policymakers should also consider these complexities when conducting public relations. the positive correlation between behavior and relieving anxiety by wearing masks suggests that laypeople consider subjective feelings rather than objective risks. we did not examine whether this was derived from lack of knowledge, risk calculation ability, or human predisposition toward risks. however, this tendency should also be considered when delivering risk information. this study has limitations, prompting recommendations for future research. single items were used for measuring the constructs in the survey. therefore, the measures may be associated with larger error variance compared with multiple scales. furthermore, factors other than conformity, affect heuristic and single action bias were not included in the predictors of mask usage in the regression model. despite these limitations, this study has empirically revealed that the expectation of risk reduction does not greatly promote mask-wearing countermeasures against covid-19, suggesting that the nudge approach (i.e., taking advantage of people's conformity) may be more promising. in future research, it will be necessary to construct more extensive models and design and conduct more elaborate surveys to comprehensively understand the public's behaviors in relation to infection risks. all datasets presented in this study are included in the article/supplementary material. the studies involving human participants were reviewed and approved by the ethical commission of the faculty of psychology at doshisha university. written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements. kn designed and performed the research. ry analyzed the data. to and ys wrote and edited the paper. all authors contributed to the article and approved the submitted version. this research was supported by internal funds from doshisha university to kn. is empathic emotion a source of altruistic motivation? coronavirus: sharp to use tv factory to make surgical masks a focus theory of normative conduct: recycling the concept of norms to reduce littering in public places not wearing masks to protect against coronavirus is a "big mistake conformity and character the affect heuristic in judgments of risks and benefits prevalence of preventive behaviors and associated factors during early phase of the h1n1 influenza epidemic respiratory virus shedding in exhaled breath and efficacy of face masks behavioral foundations of community emergency planning the protective action decision model: theoretical modifications and additional evidence understanding the impact of face mask usage through epidemic simulation of large social networks" in theories and simulations of complex social systems, intelligent systems reference library social norms as solutions a protection motivation theory of fear appeals and attitude change cognitive and physiological processes in fear appeals and attitude change: a revised theory of protection motivation" in social psychophysiology: a sourcebook a normative decision-making model of altruism" in altruism and helping behavior: social, personality, and developmental perspectives the affect heuristic" in heuristics and biases: the psychology of intuitive judgment risk as analysis and risk as feelings: some thoughts about affect, reason, risk, and rationality journey through an epidemic: some observations of contrasting public health responses to sars a personality scale of manifest anxiety perception and expectation of climate change: precondition for economic and technological adaptation" in environment, ethics, and behavior: the psychology of environmental valuation and degradation (the new lexington press management series experience-based and description-based perceptions of long-term risk: why global warming does not scare us (yet) coronavirus disease (covid-19) advice for the public: when and how to use masks world health organization (who) (2020b) who emergencies press conference on coronavirus disease outbreak -30 the relationship between infection-avoidance tendency and exclusionary attitudes towards foreigners: a case study of the covid-19 outbreak in japan we are grateful to makiko oku for assistance with data collection. the dataset generated for this study can be found online at: https://www.frontiersin.org/articles/10.3389/fpsyg.2020.01918/ full#supplementary-material. the authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. the original publication in this journal is cited, in accordance with accepted academic practice. no use, distribution or reproduction is permitted which does not comply with these terms. key: cord-292173-95t89yee authors: villani, federico alcide; aiuto, riccardo; paglia, luigi; re, dino title: covid-19 and dentistry: prevention in dental practice, a literature review date: 2020-06-26 journal: int j environ res public health doi: 10.3390/ijerph17124609 sha: doc_id: 292173 cord_uid: 95t89yee sars-cov-2 is a member of the family of coronaviruses. the first cases were recorded in wuhan, china, between december 2019 and january 2020. italy is one of the most affected countries in europe. covid-19 is a new challenge in modern dentistry. new guidelines are required in dental clinics to avoid contagion caused by cross-infections. a narrative review was performed using both primary sources, such as scientific articles and secondary ones, such as bibliographic indexes, web pages, and databases. the main search engines were pubmed, scielo, and google scholar. twelve articles were selected to develop the bibliographic review by applying pre-established inclusion and exclusion criteria. precautionary measures should be applied to control covid-19 in clinical practice. several authors have highlighted the importance of telephone triage and/or clinic questionnaires, body temperature measurement, usage of personal protective equipment, surface disinfection with ethanol between 62% and 71%, high-speed instruments equipped with an anti-retraction system, four-handed work, and large-volume cannulas for aspiration. clinically, the use of a rubber dam is essential. ffp2 (or n95) and ffp3 respirators, if compared to surgical masks, provide greater protection for health workers against viral respiratory infections. further accurate studies are needed to confirm this. this article is a narrative review. zoonotic diseases constitute a large group of infections that can be transmitted from animals to humans, regardless of the presence of vectors [1] . approximately 80% of viruses, 50% of bacteria, and 40% of fungi are capable of generating a zoonotic infection [2] . bats are considered important reservoirs and vectors for the exponential spread of zoonotic infectious diseases; they are associated with sars and ebola, the latter of which was responsible for an epidemic with its epicenter in sub-saharan africa in 2014 [3] . sars coronavirus in 2003 and 2019, and h1n1 flu in 2009 have demonstrated how a zoonotic infection can spread rapidly among humans, causing potentially irreversible global repercussions, from an economic, social, and health-related standpoint [2] . compared to previous eras, globalization and the intensification of international movements have greatly facilitated the spread of viruses [1] [2] [3] [4] . coronaviruses are a subfamily of viruses [5] . all viruses contain nucleic acids, either dna or rna, and a protein coat which encases the nucleic acid. some viruses are also enclosed by an envelope of fat and protein molecules [5, 6] . towards the last week of december 2019, cases of abnormal pneumonia with unknown etiology were recorded in wuhan, the capital of the hubei province, in the geographical heart of the people's republic of china [11] . in the second half of january, the chinese competent authorities confirmed 6000 cases of patients infected with sars-cov-2, although 80,000 cases were estimated at that time [21] . however, unlike sars-cov-1, sars-cov-2 has shown a greater tendency for rapid human-to-human transmission, with an r0 varying between 1.4 and 6.5, and an incubation period ranging from 2 to 14 days, with an average of 7 days [10] . on 31 january 2020, 213 deaths had been confirmed globally in 19 different countries [11] . according to the data of 14 march 2020, italy was the most affected european country, followed by spain [22] . on 3 may 2020, the number of people currently positive in italy was 100,179, with 28,884 deaths [23] . the average age of people who died of covid-19 was 78.5 years, while, the average age of diagnosis was 65 [22] . the age group with the highest mortality rate was 80 to 89 years, with a male predominance (67%). the mortality rate in the male population increased by 10% (77%) in the 70-79 age group [22] . forty-eight percent of patients deceased from sars-cov-2 exhibited three or more comorbidities, two comorbidities (26%), one comorbidity (23%) and no comorbidity (1.2%). hypertension, diabetes, and ischemic heart diseases are among the main preexisting pathologies. only 1% of deaths from covid-19 occurred in patients under the age of 50 years. lombardy was the most affected region, accounting for 68% of the national cases, followed by emilia romagna (16.4%) and veneto (4.3%) [24] . these data prompted authors to investigate the existence of a possible link between the exponential transmission of covid-19 in certain italian regions and the pollution of atmospheric particulate matter, the latter acting as a vector of the virus [25] . however, this is a spurious association because there are systematic errors that determine the lack of correlation between these two factors. according to that reported by the new york times [26] , dentistry is one of the most exposed professions to the covid-19 contagion. it is necessary to establish a clinical protocol to be applied in the working environment to avoid new infections and progressive virus spread. in daily clinical practice, the patient's oral fluids, material contamination, and dental unit surfaces can act as sources of contagion both for the dentist and the assistant, and for the patient himself or herself. saliva and blood droplets that are deposited on the surfaces or aerosol inhalation generated by rotating instruments and ultrasound handpieces constitute a risk for those who occupy or will occupy those environments. therefore, the use of disinfectants and personal protective equipment (ppe) remain essential for the proper development of the dental profession [27] . the sudden spread of sars-cov-2 has determined the need to modify both preventive and therapeutic protocols in dental practice. consequently, the need to analyze the available sources in the literature to update clinical practice is crucial. the aim of this narrative review is to investigate preventive measures in dental practice by assessing the operator and patient health protection during the new covid-19 emergency by considering past experiences in terms of prevention, as the virus was only recently discovered. special attention is devoted to personal protection equipment, such as respirators and surgical masks, due to the major exposition of dental workers to the coronavirus. the authors carried out a narrative review and not a systematic review, as the topic is based on a recent event, and there are still several aspects pending to be analyzed. the process of selecting scientifically valid sources took place over five weeks, between 1 april and 4 may 2020. the search engines used were pubmed, scielo, and google scholar. the boolean operators used "and" and "or". the mesh terms for the research were: "dental care", "dentistry", "dental offices", "masks", "coronavirus", "dental equipment", and "disinfectants". non-mesh words were "sars-cov-2" and "ppe" the following terms were used with boolean operators to combine searches: "covid-19" or "sars-cov-2" or "coronavirus" and "dental care" or "dental office" or "dentistry" with no limitation to the year of publication. in addition, a second search was made: "masks" or "disinfectants" or "ppe" or "dental equipment" and "covid-19" or "coronavirus" or "sars-cov-2". included in the study were bibliographic reviews, systematic reviews, meta-analyses, randomized controlled trials, cohort studies, case reports, and studies in english, italian, spanish, and portuguese. the exclusion criteria were as follows: articles not related to the topic, animal studies, full-text not available, and articles in other languages. no time limits were applied during the screening phase of the scientific articles ( figure 1 ). given the heterogeneous results, the selected articles were divided into two main groups according to the treated topic: sars-cov-2 guidelines in dentistry ( table 1 ) and analysis of preventive masks used for protection against sars-cov-2 (table 2) . a third group, on disinfectants, was analyzed. the results obtained demonstrate compliance and homogeneity between the authors. in studies done by rabenau et al. [37] and kampf et al. [38] , ethanol proved to be one of the first-choice disinfectants in percentages ranging from 80 to 95% (used as a hand rub gel) [37] or 62 to 71% (used as a surface disinfectant) [38] . the coronavirus is reduced to below recording levels in a variable lapse of time between 30 and 60 s. in the study by rabenau et al., similar results were observed with disinfectant based on 45% iso-propanol, 30% n-propanol, and 0.2% mecetronium ethyl sulfate. furthermore, the use of surface disinfectants such as mikrobac forte (containing benzalkonium chloride and laurylamine), khorsolin ff (containing benzalkonium chloride, glutaraldehyde, and didecyldimonium chloride), and dismozon (containing magnesium monoperphthalate) can be valid options, even if the desired effect is obtained after 30-60 min [37] . with all tested preparations, sars-cov-2 was inactivated to below the limit of detection, regardless of the type of organic load (0.3% albumin, 10% fetal calf serum, and 0.3% albumin with 0.3% sheep erythrocytes). kampf et al. in carrier tests demonstrated the disinfectant action of ethanol at 62-71% against the sars coronavirus in 60 s, of sodium hypochlorite between 0.1-0.5% in one min, and glutaraldehyde at 2%. in contrast, 0.04% benzalkonium chloride, 0.06% sodium hypochlorite, and 0.55% ortho-phtalaldehyde were less effective [38] . the percentages varied in the suspension tests, where ethanol (between 78 and 95%), 2-propanol (70-100%), the combination of 45% 2-propanol with 30% 1-propanol, glutardialdehyde (0.5-2.5%), formaldehyde (0.7-1%) and povidone iodine readily inactivate the coronavirus; hypochlorite is effective at a concentration greater than 0.21% [38] . fundamentally, the authors agree ( table 1 ) that it is essential to perform an accurate telephone triage, a subsequent triage in dental clinics, and a complementary questionnaire to collect as much information as possible about the patient and his or her family members, specifically regarding symptoms and movements in the previous 14 days [27] [28] [29] [30] [31] . temperature measurement is recommended when the patient enters the dental office; if the body temperature exceeds 37.3 • c, it is suggested the treatment be postponed [30] . in patients with a cured covid-19 infection, the american dental association (ada) guidelines propose to reschedule dental treatment at least 72 h after the resolution of the symptoms, or 7 days after the appearance of initial symptoms, such as fever controlled without antipyretics and spontaneous improvement of breathing [39] . meng et al., in a precautionary way, set the necessary recovery period to 30 days before performing non-deferrable dental care in patients who have been infected [28] . for medical-legal issues, a patient's self-certification is also required with regard to what he/she claims during the telephone and clinical triage phase. the ada and the centers for disease prevention and control (cdc) recommend keeping the waiting room empty, without magazines, and avoiding the overlap of two or more appointments. if this is not possible, the minimum distance between one patient and the other must be 2 m (6 feet) in each direction. in extreme situations, for health protection, it is reasonable to ask patients to wait in their vehicle, if possible, or nearby to the dental clinic, and advise them by telephone call or message when it is their turn [40] . as far as pediatric dentistry is concerned, persons accompanying minor age patients are asked to come to the appointment in the smallest possible number, wear a protective mask, wait in the waiting room, and not attend the patient's treatment to avoid the risk of aerosol inhalation [27] . further accurate studies have been carried out to demonstrate the importance of oral rinses just before dental treatment; costa et al., in a study in 2019, highlighted how the use of chlorhexidine at 0.12% and 0.20% alters the amount of bacteria, viruses, and fungi present in the oral biofilm, reducing the risk of cross-contamination due to aerosol [29] . since covid-19 is sensitive to oxidation, peng et al. proposed rinsing with 1% hydrogen peroxide or, alternatively, with 0.2% povidone-iodine [30] . this must be interpreted with caution: saliva is constantly and cyclically renewed by the salivary glands, making the virus available again. regardless of the type of treatment planned, healthcare professionals, especially dentists, hygienists, and dental assistants, must follow rigid protocols related to dressing and personal protective equipment. hair caps, protective goggles, surgical masks or n95, disposable surgical gowns, special footwears, and protective visors are essential [27] [28] [29] [30] [31] . according to the "en iso 374-5.2016" regulation, for medical protection gloves to be considered functional against microorganisms, such as bacteria and fungi, must pass the penetration test, which analyzes air and water transition through material pores, seams, holes, and other structural imperfections [41] . "iso 16604: 2004 method b" is an additional test that is necessary to certify the specific protection of the gloves against viruses [42] . the ppe should be used as asserted in the instructions in the user manual and must be disposed of as special waste. it is always recommended to check the integrity of the ppe, and if any negative findings, eliminate the ppe immediately [43] . there are several articles in the scientific literature on the effectiveness of surgical masks in comparison to respirators ( table 2 ). the distance and length of time in which particles remain suspended in the air are determined by particle size, settling velocity, relative humidity, and air flow [36] . the european standard classifies filtering facepiece respirators (ffp) into three categories: ffp1, ffp2, and ffp3 with minimum filtration efficiencies of 80%, 94%, and 99%. consequently, ffp2 respirators are approximately equivalent to n95, and therefore recommended for use in the prevention of airborne infectious diseases in the us and other countries [44, 45] . both long et al. [32] and radonovich et al. [34] , in their respective analyses did not find significant differences between the n95 and surgical masks in terms of protection from the influenza virus. similar results were also observed in the study by offeddu et al., which was performed two years before the current covid-19 health emergency. on one hand, there is an equal effectiveness between the two types of masks on the influenza virus. however, compared to nonspecific respiratory tract infections, the n95 masks give slightly better results [33] . macintyre et al. instead obtained diametrically opposing results; they showed, through a randomized controlled clinical study on 3591 subjects, that health workers who used n95 masks continuously during the shift or in situations considered to be at high risk, presented an 85% chance of not contracting a viral infection transmitted via droplets [36] . in addition, the n95 mask group compared to the control group was associated with a significantly lower risk of contracting influenza, as confirmed by the laboratory. the authors suggest updating the classification of infectious transmissions; they consider that focusing only on aerosols and droplets is an oversimplification. in a recent study, ma et al. analyzed the degree of protection of surgical masks, n95, and home masks (four layers of paper and polyester) against the virus; n95 masks showed greater reliability [35] . lee et al., focused on particles between 0.093 and 1.61 µm, and demonstrated that the ffp respirators provided better protection than the surgical masks, suggesting that such surgical masks are not a good substitute for ffp respirators in the case of airborne transmission of bacterial and viral pathogens [44] . the principal limitation of surgical masks is due to the poor face fit and the consequential possibility of aerosol aspiration [43] . in spain, the dentists council (consejo de dentistas) reports a maximum of 4 h of use, and if kept in good condition, ffp2 or n95 masks can be sterilized through various techniques: hydrogen peroxide vapor, dry heat at 70 • c for 30 min, or in humid heat at 121 • c; however, not for more than 2-3 times [45] . the who protocol recommendations suggest the use of ffp3 masks according to the european nomenclature or n100, according to the united states nomenclature [46] . hand hygiene is considered the first step in limiting the spread of the virus; who guidelines impose scrupulous hand-washing before and after any contact with the patient [46] . being previously considered an essential tool for correct operating practice, the rubber dam has become even more so after the viral epidemic of 2020. various authors underline the utility of the rubber dam on containment and protection from oral fluids; it reduces the particles present in the aerosol by 70% [30] and also drastically reduces the risk of cross-infection [27, 28, 30 ]. if it is not possible to position it, peng et al. recommend the use of the carisolv and an excavator for conservative treatments [30] . high-speed rotating instruments, such as the turbine and the contra-angle, must be equipped with an anti-retraction system, which prevents the release of debris and fluids that can accidentally be inhaled by healthcare professionals during clinical procedures [29, 30] . meng et al. suggests minimizing the use of these tools; if this is not possible, the last appointment of the day should be intended for those patients who need dental treatments requiring the use of high-speed rotating instruments [28] . they also recommend not to use intraoral radiographs; therefore, they propose the use of orthopantomography or ct if strictly necessary. the authors agreed on the need for four-handed work to reduce the risk of spreading the virus in the dental care unit, to manipulate the water-air syringe with extreme caution, and to use large-volume aspirators [27, 28, 30] . concerning potentially deferred dental emergencies, luzzi et al. recommend remote telephone or assistance support from the dentist. in the case of pulp pain, therapy with non-steroidal anti-inflammatory drugs, such as ibuprofen, and antibiotics, such as beta-lactams, are recommended, if the patient does not have allergies [27] . alharbi et al. classified therapeutic dental procedures into five groups: emergencies, emergencies manageable through invasive or non-invasive procedures (minimum aerosol), non-emergencies, and elective treatments, depending on the dentist. among the emergencies, the authors highlight maxillofacial fractures that compromise the respiratory tract, uncontrolled post-operative bleeding, and bacterial oral soft tissues infections with intra-or extra-oral swelling that negatively affect the patient's respiratory capacity [47] . orthodontists are suggested to stop activating the rapid palate expander; parents are instructed to reposition the ni-ti arch if it should go off-axis and cause a contact ulcer on the oral mucosa. any non-urgent treatment must be postponed; if this is not possible, the dentist must follow strict protocols to avoid contagions. peng et al., advise the elimination of waste using special yellow double-layer bags for special waste and mark them to facilitate their elimination [30] . various disinfectants available on the market, can effectively inactivate the sars-cov-2. the italian dentists association recommends covering all surfaces, where possible, with polyethylene wrap [48] . the results obtained demonstrate compliance and homogeneity between the authors. rabenau et al. [37] and kampf et al. [38] illustrated that various groups of disinfectants, such as propanol, sodium hypochlorite, and ethanol, in percentages ranging from 80 to 95% (as a hand rub) [37] or 62 to 71% (as a surface disinfectant) [38] , can reduce sars-cov-2 load to below recording levels in a variable lapse of time. pertinent papers on this topic are limited. the who guidelines recommend the use of 5% sodium hypochlorite, with a 1:100 dilution, to be applied on surfaces for an average action time of 10 min; constant ventilation of the dental surgery room is also recommended [46] . studies have shown that other biocidal agents such as 0.05-0.2% benzalkonium chloride or 0.02% chlorhexidine digluconate probably have lower efficiency [49] . the spanish dentists council suggests the use of 1% sodium hypochlorite for the disinfection of the impressions. the action time of the disinfectant varies depending on the material used: 10 min for alginate, and 15-20 min for elastomers [45] . as reported by kyun-ki et al., it is necessary to establish preventive policies in clinical and hospital settings to avoid the high risk of nosocomial infections, as with mers [50] . sabino-silva et al., starting with the assumption that covid-19 may be present in saliva through major salivary gland infection or through the crevicular fluid, suggest more accurate studies in order to evaluate the possibility of early and non-invasive virus diagnosis using saliva samples [51] . the possibility of the role of salivary gland cells in the initial progress of the infection and as a source of the virus should be considered and validated [8] . dentistry remains one of the most exposed professions to sars-cov-2; each individual clinical situation must be adequately controlled and pondered by the healthcare professional; defaults in protocols cannot be tolerated. however, there are indications in the literature on how to deal with emergencies. currently, the swab represents the only system of diagnosis, and it requires a laboratory procedure that cannot be implemented in the dental clinic. however, rapid immunoglobulin tests, which are not considered for diagnosis, can report whether a healthcare professional has had the disease and been immunized. the development of new diagnostic tools will provide a reasonable hope for greater protection from the virus in the future. two types of rapid tests are currently being developed for covid-19: the first one directly detects sars-cov-2 antigens by nasopharyngeal secretions, while the second indirectly records the antibodies present in the serum as part of the autoimmune response against the virus [52] . ahmed et al. conducted a cross-sectional study on 699 dental practitioners from 30 different countries using an online survey between the second and the third weeks of march 2020; 87% of participants were afraid of becoming infected with covid-19 from either a patient or a co-worker. a considerable number of dentists (66%) wanted to close their dental cabinets until the number of covid-19 cases declined [53] . the fear that dentists have regarding becoming infected by covid-19 could be less if dentists and dental healthcare workers conscientiously follow the relevant recommendations [53] . looking ahead, it is necessary to increase research efforts in aerosol control during dental treatments, including improving engineering control in dental office design. the covid-19 pandemic has exposed important gaps in the collective response of global healthcare systems to a public health emergency [54] . dentistry as an integral part of the health care system should be prepared to play an active role in the fight against future emerging life-threatening diseases. preventive measures against covid-19 in dental practice include telephone and clinical triage supported by a questionnaire on recent symptoms and movements, body temperature measurement, oral rinses with 1% hydrogen peroxide, and the use of specific ppes. pragmatic and technical recommendations for correct clinical practice are the implementation of anti-retraction dental handpieces, four-handed work, the use of a rubber dam, and large-volume cannulas for aspiration. ffp2 (or n95) and ffp3 respirators, if compared to surgical masks, provide greater protection to health workers against viral respiratory infections. ethanol between 62% and 71% and sodium hypochlorite between 0.1% and 0.5% are considered to be the best among the surface disinfectants. this narrative review has some limitations. as there is a current emergency, in the literature there is a limited and heterogenous number of primary sources directly related to the repercussion of sars-cov-2 on the dental discipline. further studies are needed in the future. author contributions: authors equally contributed to conceptualization, methodology, validation, investigation, writing-original draft preparation, writing-review and editing, supervision. all authors have read and agreed to the published version of the manuscript. review: the important bacterial zoonoses in lipkin, w.i.; daszak, p. prediction and prevention of next pandemic zoonosis zoonoses and one health: a review of literature origin of measles virus: divergence from rinderpest virus between the 11th and 12th centuries the origin, transmission and clinical therapies on coronavirus disease 2019 (covid-19) outbreak-an update on the status comparative interactomics for virus-human protein-protein interactions: dna viruses versus rna viruses an overview of their replication and pathogenesis salivary diagnostics in covid-19: future research implications a pneumonia outbreak associated with a new coronavirus of probable bat origin the reproductive number of covid-19 is higher compared to sars coronavirus epidemiology, causes, clinical manifestations and diagnosis, prevention and control of coronavirus disease (covid19) during the early outbreak period: a scoping review the basic reproduction number (r0) of a measles: a systematic review ireland's health services. health care worker information clinical characteristics of coronavirus disease 2019 in china covid-19 and lung pathology the italian health system and the covid-19 challenge clinical features of patients infected with 2019 novel coronavirus in aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 surface environmental, and personal protective equipment contamination by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) from a symptomatic patient environmental contamination and viral shedding in mers patients during mers-cov outbreak in south korea breaking down of healthcare system: mathematical modelling for controlling the novel coronavirus (2019-ncov) outbreak in wuhan tra apparenza e realtà covid-19-situazione in italia characteristics of covid-19 patients dying in italy report based on available data on relazione circa l'effetto dell'inquinamento da particolato atmosferico e la diffusione di virus nella popolazione the workers who face the greatest coronavirus risk covid-19: pediatric oral health during and after the pandemics covid-19): emerging and future challenges for dental and oral medicine efficacy of preprocedural mouthrinses in the reduction of microorganisms in aerosol. a systematic review transmission routes of 2019-ncov and controls in dental practice experience of diagnosing and managing patients in oral maxillofacial surgery during the prevention and control period of the new coronavirus pneumonia effectiveness of n95 respirators versus surgical masks against influenza: a systematic review and meta-analysis effectiveness of masks and respirators against respiratory infections in healthcare workers: a systematic review and meta-analysis n95 respirators vs medical masks for preventing influenza among health care personnel potential utilities of mask wearing and instant hand hygiene for fighting sars-cov-2 the efficacy of medical masks and respirators against respiratory infection in healthcare workers. influenza other respir efficacy of various disinfectants against sars coronavirus persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents interim guidance for management of emergency and urgent dental care. united states of america ada interim guidance for minimizing risk of covid-19 transmission. united states of america protective goves against dangerous chemicals and micro-organisms. part 5: terminology and performance requirements for micro-organisms risks guantes de protección frente a microorganismos the severe acute respiratory syndrome coronavirus-2 (sars cov-2) in dentistry. management of biological risk in dental practice particle size-selective assessment of protection of european standard ffp respirators and surgical masks against particles-tested with human subjects plan estratégico de acción para el periodo posterior a la crisis creada por el covid-19 infection prevention and control of epidemic-and pandemic-prone acute respiratory infections in health care guidelines for dental care provision during the covid-19 pandemic. saudi dent linee guida covid19 restart being a front-line dentist during the covid19 pandemic: a literature review risk of transmission via medical employees and importance of routine infection-prevention policy in a nosocomial outbreak of middle east respiratory syndrome (mers): a descriptive analysis from a tertiary care hospital in south korea coronavirus covid-19 impacts to dentistry and potential salivary diagnosis european centre for disease prevention and control. an overview of the rapid test situation for covid-19 diagnosis in the eu/eea fear and practice modifications among dentists to combat novel coronavirus disease (covid-19) outbreak dental care and oral health under the clouds of covid-19 this article is an open access article distributed under the terms and conditions of the creative commons attribution (cc by) license funding: this research received no external funding. the authors declare no conflict of interest. key: cord-258846-v6aaflzc authors: shruti, v.c.; pérez-guevara, fermín; elizalde-martínez, i.; kutralam-muniasamy, gurusamy title: reusable masks for covid-19: a missing piece of the microplastic problem during the global health crisis date: 2020-10-20 journal: mar pollut bull doi: 10.1016/j.marpolbul.2020.111777 sha: doc_id: 258846 cord_uid: v6aaflzc nan coronavirus disease 2019 has spread rapidly to 188 countries and regions since the first cases in wuhan, china, at the end of 2019. as of october 7, 2020, more than 35.5 million people have been diagnosed with novel coronavirus and the total number of covid-19 death cases has exceeded one million globally (who, 2020a) . given that pandemic is spreading fast, countries worldwide have mandated face masks in public places to reduce transmission of respiratory droplets by infected individuals and protect healthy individuals from inhaling droplets. eight months into the covid-19 pandemic, there remains an unprecedented demand for personal protective equipment (ppe) products including, face masks, gloves, coveralls, gowns, goggles, and face shields. previously, world health organization warned of a potential ppe shortage with an estimated requirement of 89 million medical masks each month and requested to increase manufacturing by 40% (who, 2020b). since march 1, 2020, according to customs statistics, china has exported 26.7 million n-95/kn-95 masks, 504.8 million surgical masks, 195.9 million gloves, 17.3 million surgical gowns and 873,000 goggles. responding to evolving global needs, both national and international companies augmented their manufacturing and output of ppe products. for example, 3 m (usa) has multiplied its output of n95 masks to 95 million per month by may and the annual rate was projected from 1.1 billion to 2 billion masks by the end of 2020 (gereffi, 2020) . meanwhile, the far lower prices for ppe have been increased dramatically in the last months. the berkeley public health center reported an increase for n95 masks from $1.27 to $5.90, for surgical masks from $0.05 to $0.55, for isolation gowns from $0.5 to $5, for face shields from $0.50 to $4.50 and for exam glove pairs from $0.04 to $0.12 during pandemic period (laurel lucia, 2020) . this is mainly due to several factors such as, supply shortages, a limited number of ppe manufacturing companies worldwide and increasing awareness among people to use high quality products (ranney et al., 2020) . in addition, the march 2020 collapse in oil production under the weight of covid-19 pandemic has become one of the major drivers for the exceptional growth of plastics (king, 2020; wood mackenzie, 2020) . notwithstanding the impact of plummeted oil price and production, companies are forced to turn crude oils into virgin plastics, that may possibly result in the massive plastic production for ppe and elevating their prices to overcome increasing oil losses. during the outbreak, many countries experienced challenges in acquiring sufficient quantities of quality masks largely because they are underfunded. in developing countries such as thailand, japan, mexico, vietnam, and south africa, where surgical and n95 masks have been reserved for health care providers or are scarce, the main alternative for the general public seems to be the use of nonmedical reusable masks made up of fabric or cloth. reusable masks are washable and costeffective and thus do not constitute an additional burden on already diminished economic activity. countries like south africa and thailand have made it mandatory for the public to wear cloth face masks alone and diminished the use of n95 and surgical masks (rsa, 2020; who thailand, 2020) . according to ministry of public health of thailand, from april 3, 2020, over 43 million cloth masks have been distributed to public (who thailand, 2020). in just a matter of months, the use of reusable face masks is quite widespread among public and have quickly evolved as an essential public health item in the combat against the pandemic. indeed, the rapid expansion of sales on millions of cloth masks has been reported in online sources such as amazon and etsy (kavilanz, 2020) . the chicago-based global market research estimated the cloth face mask market would reach $800 million in the us, and $3 billion globally, by the end of 2020 (kavilanz, 2020) . according to the who, the ideal reusable masks can be rewashed multiple times and have a combination of three distinctive layers, providing 2-5 times increased filtration efficiency compared to a single layer of the same cloth: 1) an inner layer of a hydrophilic material (e.g. cotton or cotton blends) that absorbs; 2) an outermost layer made of a non-absorbent hydrophobic material (e.g., a fabric that is a combination of cotton and polyester; nylon or rayon; polypropylene; polyester; or their blends) to limit external contamination; 3) a middle hydrophobic layer of synthetic non-woven material (e.g. polypropylene) or a cotton layer that filters or retain droplets, with elastic ties (rubber bands, string, cloth strips, or hair ties) for wearing (who, 2020c masks should be washed using a complete wash cycle at 60 • c with detergent and can only be used after being well-dried (who, 2020c). guidelines provided by various organizations including the u.s. centers for disease control and prevention, the infection control expert group (australia), and the pan-canadian public health network have also made similar recommendations for reusable masks made from highquality material, such as high-grade cotton, and having multiple layers and particularly hybrid constructions. commercially available homemade reusable face masks include different types of fabrics with significant portion of synthetic textiles, such as cotton quilt, flannel (65% cotton and 35% polyester), synthetic silk (100% polyester), natural silk, spandex (52% nylon, 39% polyester, and 9% polyetherpolyurea copolymer), satin (97% polyester and 3% spandex), chiffon (90% polyester and 10% spandex), cotton/polyester, and polyester/ polyamide mix (konda et al., 2020) . in addition, the online shopping and retail stores offer a wide variety of reusable face masks with in-built or disposable filters that are made up of plastic materials similar to disposable masks. studies have confirmed the effectiveness of homemade cloth face masks, which likely have two or three layers, in reducing droplets from coughing and sneezing (aydin et al., 2020; konda et al., 2020) . a recent study surveyed the state of mask-wearing and found that a majority of persons leaving their home reported using cloth face masks (61.9% to 76.4%) than other types (fisher et al., 2020) . with the continuous spread of the covid-19 pandemic, the reusable face mask market is witnessing high demand across the globe. developed countries have certification for reusable masks that ensures their composition and reusability (number of washes possible), and only masks that are certified are allowed in the market. for countries like portugal, spain, belgium, germany, and france, the certification is from the technological centre for the textile and clothing industry of portugal (ww.citeve.pt). however, the situation in several countries across continents is not the same, and evidence for certifications is sparse, leading to uncertified and substandard masks being reported as sold in the market and shops (lam et al., 2020) (fig. 1) . considering that plastic pollution in the marine environment is a global issue, in light of the covid-19 pandemic-induced changes, an increasing number of research papers have raised concerns about plastic waste management and the improper disposal of ppe (sharma et al., 2020; silva et al., 2020) . two recent studies have investigated whether surgical face masks and n95 masks could be a source of microplastic (plastic fragments with dimension of <5 mm) pollutants in the environment. the results strongly suggest that these masks act as a potential source of microfibers when they are released into the environment, adding additional burden to current microplastic pollution (fadare and okoffo, 2020; aragaw, 2020) . reusable masks are presently excluded from microplastic surveys; as of now, the environmental impact of reusable masks is unknown and not scientifically documented. one can imagine why should we consider reusable masks as a potential source of microplastics. under these circumstances, it is imperative to step back and examine the basic scientific evidence regarding the machine-and hand-laundering of synthetic textiles and clothing for microplastic pollution. generally, the release of microplastics from clothing is mainly caused by mechanical action and chemical (e.g. detergent) stresses, leading to the detachment of microfibers from fabrics (made up of polyester, polyester-cotton blend, cotton, rayon, and acrylic fabrics, among others) during the washing process in laundry machines (napper and thompson, 2016) . further, the short staple fibers are easily broken and released from the fabric, contributing majorly to microfiber contamination. a quick review of the academic literature reveals a number of studies that indicate that laundering clothing is a significant point source for emissions of microplastics (napper and thompson, 2016; almroth et al., 2018; belzagui et al., 2019; de falco et al., 2019; zambrano et al., 2019; o'brien et al., 2020) . the emission values of microfibers are influenced by mode of laundering (i.e. machine or hand), type of detergent and conditioner used, temperature conditions, and type of clothing being laundered (hartline et al., 2016; napper and thompson, 2016; zambrano et al., 2019) . the size of majority of microfibers released from laundering ranged from <6 μm to >2 mm. boucher and friot (2017) estimated that synthetic clothes, the main source of primary microplastics, contribute about 35% of the global release of primary microplastics to the earth's oceans. as textiles have become an important source of microplastics, arguably, it is important to consider including reusable masks in microplastic research to address questions concerning its contribution to microfiber generation during machineand hand-laundering. assuming that reusable masks do undergo similar effects as other clothing during washing, emissions of a variety of natural (e.g. cellulose) and synthetic (e.g. polyester, nylon, rayon) fibers are expected, depending on the cloth characteristics (fig. 2) . after laundering, they are discharged into wastewater and enter the environment through wastewater effluent, atmospheric deposition, or through contaminated sludge, finally making their way into oceans and human food chain (yang et al., 2019; henry et al., 2019; o'brien et al., 2020) . natural and synthetic fibers appear to be ubiquitous in the world's oceans, with variation in abundance and composition among ocean basins (suaria et al., 2020) . among these fibers, cotton microfibers are considered biodegradable, but little is known about their degradation in marine environments (henry et al., 2019) . it is important to highlight that cellulose fibers are mostly man-made and are extruded and processed industrially. importantly, cellulose-based fabrics have shown to shed more microfibers than laundering polyester; however, differences may occur based on fabric constructions and washing conditions (zambrano et al., 2019) . moreover, microfibers comprised of rubber, polypropylene, and nylon are not easily biodegradable. over time, these nonbiodegradable microfibers break down to generate smaller tiny plastic particles in the environment (gesamp, 2015; koelmans and pahl, 2019) . the negative impacts of microfibers on aquatic organisms have been well-studied and well-documented in recent reviews (avio et al., 2020; kutralam-muniasamy et al., 2020) . further, textile microfibers have a number of chemicals, added at the manufacturing stage, including, resins, softeners, dyes, and flame retardants, and it is possible that they can become coated in organic micropollutants and heavy metals during their persistence in the environment. once released in the body, they will be hazardous for marine life (carbery et al., 2018; fred-ahmadu et al., 2020) . another important research question is regarding the number of microfibers released from reusable masks. for example, de falco et al. (2019) reported that the quantity of microfibers released during washing differs with the type of garment being washed, ranging from 124 to 308 mg for each kilogram of fabric washed, which corresponds to microfibers ranging between 640,000 and 1,500,000 units. owing to the lack of evidence, there is an immense knowledge gap regarding the emissions of microfibers from reusable masks during each wash, and it is now essential to start investigations addressing these issues. the estimation is particularly important since millions of reusable masks are being/already sold, washed every day by public around the globe. from an experimental design, machine-and hand-laundering of 1 kg of reusable masks (each mask weighs ~20-50 g) is a good starting point to quantify the mass of microfibers generated and to understand their characteristics (i.e. size and polymer). beyond this, even the reusable masks have a limited time of use. some can be used efficiently until 25 washes and others until 50 (ww. citeve.pt). therefore, what happens with these masks after use is a concern that is overlooked in recent literature. alarmingly, from what has been observed in the covid-19 pandemic, it is not inevitable that these masks will end up either in nature or in domestic waste. in case of non-certified reusable masks, there are currently no recommendations agreed upon regarding the lifetime/number of cycles of using a reusable mask, misleading the public to consume more and often. thereby, the increased usage and regular washing will ultimately weaken the fabric and consequently result in the disposal of reusable masks and their fig. 2 . potential release, transfer, and fate of microfibers from reusable face masks. accumulation in the environment. this further emphasizes the necessity of conducting investigations on reusable masks to understand their contribution of microfibers during machine-and hand-laundering throughout their life cycle. on the other hand, it is expected that the related authorities might take action and advise the public on the best usage conditions of uncertified reusable masks with respect to these terms in the near future. it should also be taken into account that marine plastic litter also originates from fishing, recreational activities like tourism, aquaculture and/or directly discharged from ships (galgani et al., 2019) . this pandemic has caused the shipping and maritime industry to shut down for the safety and prevention of the escalation of covid-19. during april 2020, nearly 44.3% of the global ocean and 77.5% of 22 national jurisdictions showed a decrease in marine traffic density . furthermore, activities related to tourism, fishing and aquaculture came to a standstill during this pandemic (fao, 2020) . from the environmental point of view, the impact of reduction in these activities is broad and even with the following gradual recovery of maritime activities, we may expect a large decrease in litter generation. yet, it is not possible to estimate the extent of the impact of covid-19 as there is no robust data on hand for the analysis of trends in marine litter contamination because of the temporary closure of field campaigns in many countries. while there is a lot we do not yet know, we do know that, a large increase in mask production and usage is equally worrisome as they are already showing up in water bodies along various beaches and coastlines around the world. while we wait for the data, however, we presume that the poor ppe disposal may continue to rise and end up contributing to marine litter. in conclusion, we emphasize the immediate need for understanding the degree of risk and potential significance of the environmental impact of reusable face masks to fill the knowledge gap during the global health crisis. moreover, we believe that this open discussion would trigger some productive conversations among researchers and will hopefully accelerate multidisciplinary research to promote scientific development and management of this source of microplastic pollution. with face masks becoming a normalized requirement due to the covid-19 pandemic, there is a chance of increasing environmental microplastic concentrations and thus a higher chance of interaction, ingestion, and hazardous effects across food webs. therefore, the calls for further research and rapid development in this area are of urgent importance as the use of reusable masks continues to increase among the general public and will continue to do so for an extended period of time in the future. the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. quantifying shedding of synthetic fibers from textiles; a source of microplastics released into the environment surgical face masks as a potential source for microplastic pollution in the covid-19 scenario distribution and characterization of microplastic particles and textile microfibers in adriatic food webs: general insights for biomonitoring strategies performance of fabrics for home-made masks against the spread of covid-19 through droplets: a quantitative mechanistic study microplastics' emissions: microfibers' detachment from textile garments trophic transfer of microplastics and mixed contaminants in the marine food web and implications for human health the contribution of washing processes of synthetic clothes to microplastic pollution covid-19 face masks: a potential source of microplastic fibers in the environment fao, 2020. covid-19 and its impact on the fisheries and aquaculture sector factors associated with cloth face covering use among adults during the covid-19 pandemic -united states interaction of chemical contaminants with microplastics: principles and perspectives impacts of marine litter. front what does the covid-19 pandemic teach us about global value chains? the case of medical supplies sources, fate and effects of microplastics in the marine environment: a global assessment microfiber masses recovered from conventional machine washing of new or aged garments microfibres from apparel and home textiles: prospects for including microplastics in environmental sustainability assessment etsy's on fire as reusable face mask sales surge oil price crash ripples through chemicals production a scientific perspective on microplastics in aerosol filtration efficiency of common fabrics used in respiratory cloth masks an overview of recent advances in micro/nano beads and microfibers research: critical assessment and promoting the less known global risk to the community and clinical setting: flocking of fake masks and protective gears during the covid-19 pandemic economic and health benefits of a ppe stockpile tracking the global reduction of marine traffic during the covid-19 pandemic release of synthetic microplastic plastic fibres from domestic washing machines: effects of fabric type and washing conditions airborne emissions of microplastic fibres from domestic laundry dryers critical supply shortages-the need for ventilators and personal protective equipment during the covid-19 pandemic republic of south africa challenges, opportunities, and innovations for effective solid waste management during and post covid-19 pandemic increased plastic pollution due to covid-19 pandemic: challenges and recommendations microfibers in oceanic surface waters: a global characterization who, 2020a. coranavirus disease (covid-19 shortage of personal protective equipment endangering health workers worldwide advice on the use of masks in the context of covid-19 coronavirus disease 2019 (covid-19) who thailand situation report has covid-19 changed the economics of plastics recycling? microfiber release from different fabrics during washing microfibers generated from the laundering of cotton, rayon and polyester based fabrics and their aquatic biodegradation elizalde-martínez a , gurusamy kutralam-muniasamy b,* a centro mexicano para la producción más limpia (cmp+l) vcs thanks conacyt project no. 274276 "fase i de la remediación de á reas contaminadas con hidrocarburos en la refinería gral. lázaro cárdenas" for postdoctoral fellowship. the authors would like to acknowledge all the doctors, health-care professionals, police personnel, sanitation workers and waste collectors at the frontlines working silently and tirelessly during covid-19 outbreak world-wide. key: cord-296216-odzm7lml authors: kroo, l.; kothari, a.; hannebelle, m.; herring, g.; pollina, t.; chang md, r.; banavar, s. p.; flaum, e.; soto-montoya, h.; li, h.; combes, k.; pan, e.; vu, k.; yen, k.; dale, j.; kolbay, p.; ellgas, s.; konte, r.; hajian, r.; zhong, g.; jacobs, n.; jain, a.; kober, f.; ayala, g.; allinne, q.; cucinelli, n.; kasper, d.; borroni, l.; gerber, p.; venook, r.; baek md, p.; arora m.d., n.; wagner md, p.; miki md, r.; kohn md, j.; kohn bitran md, d.; pearson md, j.; herrera md, c. m.; prakash, m. title: pneumask: modified full-face snorkel masks as reusable personal protective equipment for hospital personnel date: 2020-04-29 journal: nan doi: 10.1101/2020.04.24.20078907 sha: doc_id: 296216 cord_uid: odzm7lml here we adapt and evaluate a full-face snorkel mask for use as personal protective equipment (ppe) for health care workers, who lack appropriate alternatives during the covid-19 crisis in the spring of 2020. the design (referred to as pneumask) consists of a custom snorkel-specific adapter that couples the snorkel-port of the mask to a rated filter (either a medical-grade ventilator inline filter or an industrial filter). this design has been tested for the sealing capability of the mask, filter performance, co2 buildup and clinical usability. these tests found the pneumask capable of forming a seal that exceeds the standards required for half-face respirators or n95 respirators. filter testing indicates a range of options with varying performance depending on the quality of filter selected, but with typical filter performance exceeding or comparable to the n95 standard. co2 buildup was found to be roughly equivalent to levels found in half-face elastomeric respirators in literature. clinical usability tests indicate sufficient visibility and, while speaking is somewhat muffled, this can be addressed via amplification (bluetooth voice relay to cell phone speakers through an app) in noisy environments. we present guidance on the assembly, usage (donning and doffing) and decontamination protocols. the benefit of the pneumask as ppe is that it is reusable for longer periods than typical disposable n95 respirators, as the snorkel mask can withstand rigorous decontamination protocols (that are standard to regular elastomeric respirators). with the dire worldwide shortage of ppe for medical personnel, our conclusions on the performance and efficacy of pneumask as an n95-alternative technology are cautiously optimistic. personal protective equipment (ppe) is one of the most important protective layers for healthcare workers around the world in a crisis like covid-19 [1, 2] . however, the supply of ppe in hospitals is extremely limited and the crisis is worsening by the day [2] [3] [4] , as the industrial supply chains are unable to scale up to meet current demand [5] . we propose a potential stop-gap solution which consists of three parts: an off-the-shelf snorkel mask, a custom (3d-printed / injection-molded) adapter, and a filter/filter cartridge. the primary benefit of a snorkel mask is providing a full-face shield and air seal while allowing for controlled intake and exhaust flows through rated respiratory filters. such masks are already widely available in large quantities and designing to make use of this supply chain could allow better access to ppe for medical personnel during this crisis. typical full-face snorkel masks have a respiratory snorkel-port located at the top of the mask consisting of 1 inhale and 2 exhale channels ( figure 1 ). in most models, there is an additional one-way exhale port near the mouth/chin area. the full-face mask has been tested to withstand disinfection protocols, while still maintaining its seal performance after the disinfection. this allows the mask to be safely reused, if proper standard operating procedures are followed. our designs are aimed specifically at doctors, nurses and hospital staff (for use in settings where no alternative fdaapproved medical ppe is available or suitable for use). unlike many other open-source designs that are intended for ventilated patients or consumers, this mask is primarily designed to prioritize the protection of a healthy user, rather than the surrounding environment. it is assumed that users are alert and active during mask usage, can be trained on standard operating procedures, and have access to standard sterilization and disinfection methods used in hospitals. additionally, the appropriate filters for pneumask are currently only accessible to those with a hospital affiliation (in the usa, at the time of this publication). this concept is not intended for patient use. the goal is to couple the snorkel-port of the mask to a filter through a custom adapter. there are a couple of strategies with regards to the filter: (1) rated off-the-shelf medical respiratory inline filters can be directly connected to the adapter, or (2) alternative filter materials, such as niosh-rated industrial filters, can be attached with a second modular adapter. (a list of medical inline filters and industrial-used filters are listed in appendix a table 1 and appendix a table 4 .) many of these filters are rated for a substantially longer life-span as compared to the standard disposable n95 respirators. this project is an effort to provide a safer solution to the current ppe shortage crisis compared to untested homemade masks or bandanas, which often cannot provide good seals around the face and are not tested for high filtration efficiency. adapter. additionally, we have also developed (reverse-engineered) the geometry of the connecting feature and the cad adapter for the dolfino frontier mask, which is openly available. we have focused our design effort in this document specifically on the dolfino frontier mask unless otherwise stated. this choice to focus on the dolfino frontier mask was due to local availability in the usa at the start of this project. to facilitate further design and communications, we have developed a standard nomenclature for possible connection configurations of a snorkel mask ( figure s6 in appendix e) . the original airflow pathway of a non-modified snorkel mask is shown in (figure 2a,b) , while the modifications to the flow path are depicted in 2b. in the normal mode of operation of a non-modified snorkel mask, the inhaled air passes through the center channel of the snorkel, enters the eyes chamber, then the mouth chamber, and is inhaled by the user. in water, the chin valve is blocked, and all the exhaled air goes through the two side channels of the snorkel at the top of the mask. in air, most of the exhaled air goes through the chin valve near the mouth. the modified flow path for use as ppe (general hospital usage), is very similar to the stock configuration of the mask: all inhale breath is directed through the filter, and the majority of exhale air is directed through the chin valve. we discuss alternative flow pathway designs specifically for surgeons. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) with aids of the airflow diagrams (see panels c and d of figure 2 ), our team currently has two designs of the coupling adapters that are targeted at two different use-cases. • anesthesiologist and general-hospital use ppe: the first, most prevalent use-case is a ppe solution for hospital personnel that do not require a "sterile-field". functionally, this means that the air exhaled by the user does not need to be filtered, or redirected away from the patient. this use-case is the application for the majority of the workers in hospitals. we will refer to this prototype in this document as "pneumask-g". ( figure 2c ). • surgeon ppe: the second design is specifically targeting the needs of surgeons (a vast minority of the use-cases), which has filters on both the inhale and the exhale, and directs the exhale away from the patient. we will refer to this prototype in this document as "pneumask-s". ( figure 2d) in pneumask-g, the system is designed such that all inhaled air passes through the filter(s) attached to the top of the mask, and exhale is mostly channeled out through the built-in one-way valve at the chin of the mask ( figure 2c ) with some exhale flowing out through the filter. the design of this main system is modular to allow adaptation to supply chain shortages of filters. it consists of 2 custom adapters: 1. the first piece is an adapter that couples the dolfino frontier full-face snorkel to a female filter port, specifically to accept iso standard 22mm od filters ( figure 3b ). this adapter connects the snorkel to a single standard respiratory filter that is already in supply at many hospitals. all air from inhale is meant to be channeled through this adapter. an optional one-way valve can be placed between the adapter and the filter to prevent any exhaled air from going back to the filter, which lowers fogging and co2 buildup. optional valve and air pathway modifications are discussed in the adapter design supplementary. the final injection-molded adapter can be downloaded here (final version by eric gagner, .step only): https: //www.dropbox.com/sh/sztddvy1or1auc7/aabi99d3pklqkqbgl7xdtkhna?dl=0. the original 3dprinted design from the prakash lab is depicted in figure 3c . pull tests on this adapter were performed on several of our 3d-printed prototype models to ensure usability and secure fit. our team tested the linear pull force necessary to disconnect the adapter/o-ring male mask coupling on a snorkel mask. we found this force to be 17lbs, which was the same as for the supplied snorkel, and compared favorably with our measured linear pull force necessary to disconnect the 22mm male iso adapter/female iso virex filter coupling of 9lbs. the configuration of the pneumask-g design shown in figure 3a can be implemented with any rated filter with an iso 22mm od port. this includes both hme filters (some of which are hepa-rated) and viral filters. the performance of the design in terms of 1) work of breath and 2) co2 accumulation will depend on the filter that is used inline in the system. performance of different filters is discussed in the filter testing section. we found that it is possible to remove the soft side-channel tubes in the dolfino frontier mask, and "plug" the two remaining gaps that are left between the eye and mouth chambers. this can improve comfort slightly by forcing all exhaled air exclusively though the chin valve and decreasing inhale resistance, while also reducing backflow. however, due to the complexity of this modification and the only minor performance benefits, we do not think that these optional airflow pathway modifications are necessary. 2. in the case of supply shortage of the respiratory filters, there is a second adapter piece that we have designed to replace the viral filter with two p-100 filters made by 3m (figure 4a ). this adapter interfaces with the snorkel-to-iso part, and can be added onto the prototype. the input port is a male iso standard 22mm. the output port is designed to connect to standard cartridge filters by 3m. two gaskets are required to mount these filters (figure 4b) , and typically must be ordered separately. the validity of using p100 industrial filters for infection control is first provided by gardner et al [15] , in which they tested the viral penetration through an n95 and p100 respirator, and showed that those respirators filtered out viral particles at claimed filtering efficiencies. the specific needs of hospital personnel that are required to perform 'sterile-field' procedures was recognized as an important, separate challenge with regards to design. during surgical procedures, the air exhaled by the surgeon must be directed away from the patient, and preferably be filtered [16] . pneumask-s can also be used for surgeons who fail n95 fit tests, as typical ppe alternatives, such as positive air pressure respirators (papr), are unsuitable while operating over a surgical field. the circumstance of a contagious/infected patient posing risk to hospital personnel in a surgical environment (sterile-field) poses a unique occupational health challenge at the current time of publication. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04. 24.20078907 doi: medrxiv preprint table 4 . . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . the chin valve can be modified to be permanently closed/blocked for this prototype ( figure 2d ), such that all exhaled air is ported up through the two outside channels to the top of the snorkel. a single-part design has been developed for connecting the center channel of the snorkel (for inhale) to a male filter port, and the 2 outside channels (for exhale) to a separate male filter port. this design has the benefit of fully separating the input and output streams, while avoiding use of the chin valve. a one-way valve on the input prevents any exhaled air from going back to the filter, and lowers fogging and co2 buildup (optional). the exhale port needs to be connected to a one-way valve (mandatory). . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the primary function of respiratory ppe is to protect the wearer from exposure to pollutants present in air, specifically in this case from particles exhaled/sneezed/coughed by an infected individual. the residual exposure of the wearer depends on three independent additive components: the leak at the face, the penetration through the filter and the internal contamination. residual exposure = leak at the face + penetration through the filter + internal contamination (1) the leak at the face depends on how well the mask forms a seal with the wearer face, or said differently, how well the mask fits the wearer face. the fit is clearly dependent on the mask shape and the morphology of the individual face, and should be determined systematically for each wearer with each of the mask models used. as the origin of the leaks is a breakthrough in the sealing, the fit is considered independent from the nature of the pollutant. the penetration through the filter depends on the efficiency of the filtering material to remove particles from the air. the filtration efficiency is clearly a characteristic of the filter material and the nature of the particle, and is independent from the individual and from the mask shape. the filtration efficiency has to be measured under normalized conditions, or at least with well characterized particles corresponding to the pollutant the wearer has to be protected from. filters with less than 99% filtration efficiency at inhalation flow rates will interfere with fit tests and can result in a false fit test failure. this problem can be addressed, in quantitative fit testing, by testing masks with lower filtration efficiencies in the n95 mode available in some tsi portacount machines. the internal contamination is mainly due to an inadequate maintenance of the mask, but could be significantly reduced by wearer training, adapted maintenance, and storage protocols (such as sterilization). currently, the particles exhaled by the mask wearer have the same size range as those generated by the patients, and which the mask should protect against. the global protection factor of the mask cannot be determined while the mask is being worn, as the wearer-exhaled particles could be misinterpreted as a "leak". thus, for multiple scientific reasons, the fit and the filtration efficiency must be determined separately. the exposure of the wearer will be considered adequate when both fit and filtration efficiency criteria are respected. for their intended purpose, the seal tests of snorkel masks are done by the manufacturing companies underwater. however, the sealing ability of the snorkel masks on dry skin is unknown. per cdc and niosh regulations on the use of elastomeric respirators, a fit test can be performed in the same manner as n95 respirators to ensure seal and safety to use for an individual [19] . at this time, we recommend that all practitioners seeking to utilize these masks perform a fit test under standard n95 fit test conditions. in addition to this recommendation, additional fit test experiments have been performed in our laboratories. practically, two types of fit test can be conducted: • qualitative fit test: a liquid aerosol with a sweaty or bitter taste are generated within a confinement around the head of the mask wearer. the result of the fit test is based on the detection of the taste under the mask. • quantitative fit test: the method is based on a particle counting outside and inside the mask in parallel using the tsi portacount device. the ratio out/in gives the fit factor. at the university of utah, we performed a qualitative fit test on 3 separate volunteers, utilizing our 3d printed adapter and both an hme anesthesia circuit filter and a hepa anesthesia circuit filter on a dolfino frontier mask ( figure 5 ). out of 3 volunteers, 2 were male and 1 was female, and both males had failed their fit test in the past using regular n95 respirators. the fit test was performed by the standard university of utah operating room team as for n95 tests, as part of the emergency covid-19 response in order to evaluate emergency countermeasure personal protective equipment. importantly, all 3 individuals passed their fit tests. this preliminary result seems to indicate that the fit seal satisfies the minimum requirements for an n95 respirator or elastomeric respirator. the fit test is only meant to measure the ability of the mask to form a seal with the wearer's face, and not the efficiency of the respiratory protection. the principle of this test consists of successive measurements of the particulates concentrations inside and outside of the mask during normalized exercises. the ratio between the external and the internal concentrations is called fit factor (ff). the relevancy of the results is dependent on a few assumption: . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04. 24.20078907 doi: medrxiv preprint figure 5 a qualitative fit test was performed by the standard university of utah operating room team using the same protocol suggested by cdc and niosh on elastomeric respirators and n95 masks. • the efficiency of the filter is high enough to assure that the particle penetration rate is insignificant compared to the expected leak rate, within the range of the measured particle size (0.015 − 1 µm). p3, n100 or hepa filters are generally required to reach this specification (filtration rate > 99.95 % at 0.3 µm), with a theoretical ff > 2000 in case of perfect fit. for filters with significant penetration rate (p2 or n95), the measure is based on a smaller subset of particle sizes (around 0.04 µm) using the n95 protocol to avoid the counting of the filter-penetrating particles. • the range of the particle size measures by the portacount (0.015 − 1 µm) has been selected to stay mostly outside of the range of particulates generated by human exhalation, apart from smokers (it is inadvisable for smokers to perform these tests, but at a minimum, they should not have smoked within 30 minutes of testing). this is necessary because the particulates generated by mask wearer would otherwise be misinterpreted as a leak into the mask. • the ambient particle count exterior to the mask, in the particle size range measured by the machine, must be significantly higher than the quantity of particles that could be generated by the wearer by any method. quantitative fit testing units such as the tsi portacount are programmed to abort testing if the ambient particle count decreases under a minimum level. practically, the quantitative fit test will not measure only the leaks at the wearer's face, but also any leaks in relation with the connection after the filter or with the exhaust valve. in this way, high fit factors reflect both that the leakage at the wearer's 10/50 . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . face is acceptably low (wearer dependent), but also that the residual leaks at the level of the adapter and the chin valve are acceptable as well (wearer independent). here we present quantitative fit test results. we will first discuss the multiple tests run at stanford university (through multiple groups) on the dolfino frontier mask. we will then review the results both from stanford and from epfl on the subea decathlon mask. both mask models passed quantitative fit testing with fit factors that meet the industry-standard threshold for typical half-face elastomeric respirators. • fit measured using a portacount pro+ in order to collect a thorough measurement, each test was repeated in three locations, sampling from the mouth chamber, the eye chamber, and directly from the adapter, right after the filter. this required building two modified adapters. the adapter which sampled directly after the filter was modified by drilling a hole in the adapter between the filter connection port and the mask port. the drilled hole was cleaned and smoothed before a luer lock connector was press fit into the hole and sealed using epoxy. the epoxy was allowed to cure for 24 hours and the assembly was subsequently washed with isopropyl alcohol for 2 minutes. the adapter which sampled from the eye chamber and mouth chamber used a flexible tube to sample air from a desired location. this adapter was modified by drilling a hole large enough for the flexible tube to pass through. the hole was once again cleaned and a luer lock connector was pressed into the tube. the luer lock connector and tube were press fit into the drilled hole and sealed using epoxy. the epoxy was allowed to set for 24 hours before the entire assembly was washed for 2 minutes in isopropyl alcohol. both adapters were allowed to dry completely before any tests were conducted. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint results from the stanford prakah lab are posted here for the fit results on the dolfino frontier mask. figure 8 fit factor results when the portacount sample tube was connected to the mouth chamber, eye chamber, and inlet port of a pneumask. this mask consisted of a dophino mask connected, via an adapter, to a hepa rated mechanical hme filter (pall ultipor 25). these tests were completed in half-face respirator mode and the mask passed in all three cases. further tests were completed independently at stanford occupational health and safety which confirmed that the dolphino mask passes the quantitative fit test. two additional fit tests were conducted at stanford environmental, health and safety -one completed using the requirement of a half-face elastomeric respirator and another using the fit factor for a full-face tight fitting air purifying respirator, and the results are shown in figure 10 . the participant (female) wearing dolfino frontier with a custom adapter, and a pall ultipor 25 breathing filter, who is typically a size m, was still able to pass the quantitative fit test well beyond the requirements on both tests. the minimum passing fit factor was 100 for half-face respirator and 500 for a full-face respirator. the activities that were tested while wearing the mask included bending over (50 seconds), jogging in place (30 seconds), moving head side to side (30 seconds), and moving head up and down (30 seconds), and the fit factor outcomes were all above 750. please note that, although the test yielded positive results, this was conducted with a limited testing sample and does not yet indicate any certification/endorsement from eh&s of the product. each entity should also conduct its own evaluation and testing before use. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint subea decathlon experimental results testing was undertaken both at stanford university and at epfl with quantitative fit testing for the subea decathlon mask. below are the results from our tests at stanford. figure 10 fit factor results when the portacount sample tube was connected to the mouth chamber and inlet port of a pneumask. this mask consisted of a decathlon mask connected, via an adapter, to a hepa rated mechanical hme filter (pall ultipor 25). these tests were completed in half-face respirator mode and the mask passed in all cases. important note: the adapters used in the above test did not fit the subea mask as well as the dolphino mask. tape had to be used to form a better seal. thus these results should be interpreted as a lower bound on the sealing capabilities of the mask. validation of the fit of the decathlon mask was completed in a separate series of experiments at epfl, also using a portacount pro+ in n95 mode and following the osha 29cfr1910.134 protocol. the decathlon easybreath mask was connected to a medical grade hme filter (dar adult-pediatric electrostatic filter hme, small) with a 3d-printed pla connector. the mask was in pneumask-g configuration (3 snorkel ports connected to the filter, chin valve non modified). the mask was connected through the silicon skirt of the eyes chamber, as indicated in figure 7f , using the standard connector sold by the manufacturer of the particle counter. in n95 mode, the test was positive for the two individuals (men, freshly shaved) tested, with a fit factor of 200+, which is higher than the requirement for half-masks (100). removing the chamber valves to connect permanently the eye chamber and the mouth chamber led to the same results. this test was run in n95 mode because the test was completed using an hme filter which was not hepa rated (fit factors around 4 would have been obtained with the n100 normal protocol under the same testing conditions). the full results from epfl testing are shown in figure 11 . figure 11 fit factor test results from epfl (translated from french). note that we have identified a common testing issue mistake -you cannot use the default n100 mode unless the respirator or hme filter is rated above 99% at respiratory flow rates. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint figure 12 difference in portacount's functionality across the default and n95 modes. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint the successful results for the fit test with the different individuals used in this study indicate that the dolphino and decathlon masks both form acceptable seals, showing also that the custom adapter and the chin valve do not generate significant leaks. the measured fit factors correspond to the requirement for elastomeric half-mask. the remaining performance of the mask depends on the efficiency of the filter, which is attached to the mask. the position of the sampling point gives similar results between the mouth and the eyes chambers. however, a sampling point directly connected on the custom adapter shows significant higher fit factors, which seem over evaluated, probably due to the proximity of the filter. in this case, the measured particle concentration should not be relevant of the real concentration in the breathed air. the use of the n95 protocol of the portacount is important for the fit evaluation when hepa filters are not available, especially with hme virus filters. the efficiency of the filters should be measured independently of the portacount system to assure safe working conditions. we developed an simple experimental test rig and method for testing the particle filtration efficiency of various materials. please note this setup is not the standard testing method which typically uses the tsi automated filter tester 8130a. the setup pictured in figure 14 includes a lighthouse handheld particle counter (model 3016 iaq), intex quickfil 6c battery pump, a rubber stopper with 2 holes covered by 2 kim wipes to mitigate the airflow, incense: satya sai baba nag champa 100 gram, connectors (universal cuff adaptor, teleflex multi-adaptor), and filters to test (hudson rci main flow bacterial/viral filter, romsons hme disposable bacterial viral filter, pall ultipor 25 filter). the pump with the rubber stopper, covered by 2 kim wipes, in it, provides an airflow within a range of 5.6 -11.32 l/min to mimic that of breathing. the incense produces particles of various sizes, including those in the range picked up by the detector (0.3 µm -10 µm). with the pump on, we measure the number of particles produced by the incense. then we place the filter on the setup and run the particle counter to measure the number of unfiltered particles. to calculate the filtration efficiency, we calculate the ratio of unfiltered particles to the number of particles produced by the incense, and then subtract from one. the filter efficiencies for the 3 filters tested are reported in figure 15 . we constructed an experimental system for measuring the pressure drop across various materials, including n95 masks, during inhalation and exhalation. the setup in picture figure 16 includes an intex quickfil 6c battery pump, a honeywell awm700 airflow sensor, a honeywell abpdlnn100mg2a3 pressure sensor,a rubber stopper with 2 holes covered by 2 kim wipes to mitigate the airflow, connectors (universal cuff adaptor, teleflex multi-adaptor), and filters to test (hudson rci main flow bacterial/viral filter, romsons hme disposable bacterial viral filter, pall ultipor 25 filter). the pump with the rubber stopper, covered by 2 kim wipes, provides an inhalation or exhalation airflow within a range of 0.2-0.4 cfm to mimic that of breathing. with the pump on, we measure the airflow applied to the mask, and the differential pressure drop across the mask. the pressure drops for the 3 filters tested are reported in figure 15 . we have found that the decathlon subea masks and the dolphino masks are both capable of forming a seal that exceeds the standards required for half-face respirators and n95 masks (fit factor >100). the masks must still be properly secured and sized appropriately for the wearer with the fit verified according to the standards of the institution where the ppe is being used. the sealing capabilities of these masks were tested using a tsi portacount pro+ (in half-face mode using the osha . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint standard) on a system that consisted of the mask, a custom adapter to connect the mask and filter, and a hepa rated hme filter. the custom adapter was modified to include a sampling port to which the tsi portacount pro+ could be connected, allowing measurements at three different places inside of the mask (next to the filter, in the eye space, and in the mouth space). the particle concentrations in all parts of both masks were found to be less than 1 part in 100 relative to the ambient particle concentration (fit factor of >100). the decathlon subea mask was also tested at epfl, again with a tsi portacount pro+, on a system consisting of a decathlon mask, a custom adapter, and an electrostatic hme filter. the test was run by connecting the portacount pro+ to a port which was installed in the rubber siding of the mask next to the eye chamber. the test was run using an osha standard in n95 mode (as required by the portacount pro+ for filters with <99% efficiency). the portacount pro+ reported a fit factor of >200 (a particle count of less than 1 part in 200 relative to ambient conditions) for two different wearers. repeating the test with the eye chamber and mouth chamber directly connected to allow bidirectional airflow between the two chamber resulted in the same fit factor. the sealing capability of both the dolphino and decathlon masks has been shown to exceed the standards for half-face respirators and n95 respirators. these tests were verified at multiple locations within stanford and at epfl using different masks, wearers, adapters, filters, portacount machines, and machine operators. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint figure 16 setup for measuring pressure drop across filter. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint one concern our team had was the ability for particulates to enter through the chin exhalation valve. as these snorkel valves are not medically approved, it is necessary to understand the performance of the valves to assess safety. the niosh standard "exhalation valve leakage test" (section 84.182) stipulates the pressures and flow rates necessary for equivalent performance standard to typical n95 respirators. particularly, it states that: "(a) dry exhalation valves and valve seats will be subjected to a suction of 25mm water-column height while in normal operating position. (b) leakage between the valve and valve seat shall not exceed 30 milliliters per minute." [28] with this specification in mind, we conducted the following test to determine technical equivalency to niosh standards, investigating if this sports equipment is adequate to meet industrial device standards. a chamber was glued around the chin valve using epoxy, and an 8mm tube was connected to this chamber ( figure 17a ). the 8mm tube is connected to an opened water tank ( figure 17b) . first, the water was allowed to equilibrate by manually opening the chin valve briefly ( figure 17b) . then, the mask was lifted up to create a water column of 30mm ( figure 817c) , which corresponds to a negative pressure of 30mmh2o applied to the chin valve. as time passes, the small leakage of the chin valve reduces the negative pressure and therefore the height of the water column. the leak of the chin valve can be approximated as the ratio between the volume of air in 10mm of tube length, and the time it takes for the water column to go from 30mmh2o to 20mmh2o. on average, this time was 21 seconds. as a consequence, in steady state and for a negative pressure of 25mmh2o on average, the leak of the chin valve is on average 1.5ml/min (12 measurements, standard deviation 0.3ml/min). we conclude that the leak flow of the exhale valve (chin valve) is lower than the maximum flow allowed to comply with the niosh regulation (30ml/min for 25mmh2o of pressure). it is noted that this test was done on a one specific mask model our team had available, the decathlon freebreath. although our findings here are reassuring, there is a possibility that different mask models and manufacturers have varying quality of valves. we recommend quantifying this parameter prior to usage (especially prior to large-scale usage of any particular mask brand). the mask is lifted up (chin valve closed) to create a water column of 30mm, which means that a negative pressure of 30mmh2o is applied to the chin valve. aside from the above testing, we have also done the following calculation to see how long the chin valve takes to close ( figure 18a , figure 19 ), assuming standard exhale -to assess the likelihood of localized backflow. the following figure ( figure 18b) shows the schematic of a circular chin valve, which is pinned at the center. the valve is assumed to open from the bottom side, moving from vertical position to an angled location after exhalation of air. forces acting on the valve include the force due to the gauge exhale pressure, (p ex,g = pex − p atm ), and elastic forces. the elastic force occurs to return the valve to its original shape, this force is simply modeled by a linear spring formula. these forces should balance for a static valve at (2): where a and k denote the cross-section area and the elasticity constant of silicon, respectively. now, let's assume inhale starts at time t=0 and the valve is in the angled position (2) shown in figure 18b , α = p ex,g a kr at each time instant, in addition to the elastic force, the pressure forces due to the inhale, p in , and atmospheric pressure are acting on the valve: . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint on the other hand: and therefore: this equation is a second-order ode with boundary-conditions: θ = α and dθ dt = 0 at t = 0. this leads to the solution: accordingly, the time it takes for the valve to reach θ = 0 equals: . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04. 24.20078907 doi: medrxiv preprint the maximum closure time occurs when we assume there is no force due to pressure during inhalation, p in = p atm , and equals: in order to determine a time associated with this dynamics, we need to directly measure some of the properties of materials used in elastomeric valves. for an order of magnitude calculation, we use known numbers; for a silicon valve with density ρ = 2.3290g / cm 3 , thickness l = 0.35mm, and radius 13.5mm, the mass of the moving section is m = 0.233g.assuming elasticity constant k = 1n/m, this formula suggests that the valve closes after approximately t max = 0.024sec. the accumulation of carbon dioxide in the deadspace is a valid concern that can result in significant risks to healthcare workers utilizing respirators [18] . the accumulation of co2 can vary greatly in snorkel masks as the connections between the inhalation and exhalation arms, the design of one-way valves, and possibly attached cartridges are very versatile. also, the issue of co2 buildup is not unique to full face mask snorkels nor to elastomeric respirators, but is a known factor in the continuous use of disposable n95 respirators as well [19] . for example, lim et al., 2006 found that up to 1 3 of healthcare workers in the sars outbreak reported headaches during use of n95 (presumably from hypercapnia) and that 4 hours of continuous use of n95 is associated with headaches [18] . to test this aspect, we utilized the mask-adapter-filter setup attached to a headform and simulated lung ( figure 20 ) [20, 21] . carbon dioxide is added to the test lung at rates ranging from 200-500 ml/minute to simulate a range of metabolic output. the test lung was ventilated at respiratory rates of 12-28 breaths/minute, and tidal volumes of 400-600 ml. gas sampling is performed with a datex-ohmeda gas bench at the mouth of the headform after the carbon dioxide concentration in the snorkel mask reaches steady state for at least 4 minutes. the 3 anesthesia circuit filters we tested are teleflex main flow bacterial/viral filter 1605, iso-gard filters and filter hmes 28012, and romsons hme disposable bacterial/viral filter gs-2095. in the co2 accumulation result, for the 3 anesthesia circuit filters we tested, the steady state co2 concentration inside the mask is approximately 1-2%, which is generally safe for short term usage [20] and comparable to commercial elastomeric respirators [22] . these preliminary results are comparable to our user feedback from university of utah, where one of our authors self-tested and reported that the work of breathing appears similar to an n95 respirator when either filter is attached. subjectively, it appeared comfortable but took a small adjustment period to adapt to breathing to a comfortable level. at this time, we would recommend a periodic (every 5-10 minutes) deep forced exhalation to purge the mask of any co2 buildup, which is quite similar to previously proposed solution for elastomeric respirators [19] . as the risk of co2 accumulation is directly related to the volume of dead-space, we performed direct volume measurement on our pneumask-g setting with a body glove snorkel mask. the effective dead-space volume of the adapter is 10 ml while the effective dead-space volume of a virex n100 in-line filter is 11 ml, adding to a total volume of 21 ml, which is very low compared to the effective dead-space volume of the supplied snorkel (157ml, isolating inhalation/exhalation pathways). these results suggested that if a snorkel manufacturer has passed a co2 accumulation test with their mask and snorkel tube, it is very likely that a pneumask-g based on their snorkel mask will also pass a co2 accumulation test. under the same logic, it was proposed that ventilation on relaxed or resting states may conduce to co2 accumulation due to an insufficient quenching of the mask secondary to the low minute ventilation expected during resting states. to determine if there is a difference between resting and exercise in terms of co2 accumulation and re-breathing, a volunteer member of the team performed a "resting test". a male, 38 years old healthy volunteer, under standard monitoring including ecg, sato2, nibp, etco2 and inspired co2 measurements, wore the pneumask in the g configuration for a total of 80 minutes. during the test, the subject lied recumbent and without moving. an anesthesiologist was present at all times during the test, recording the vital signs trend and was instructed to stop the test if vital signs deteriorated in any way. the subject could not see the monitor values to prevent from altering the normal breathing pattern in reaction to co2 or other variable values. the results are displayed in the following spreadsheet. although the was an increase in the inspired co2, consistent with rebreathing and insufficient quenching of exhaled co2, with a maximum value of 9 mmhg of inspired co2 at the minute 15 of the test, the etco2 values remained stable, as did all the other vital signs values for the entirety of the test. our explanation is that the inspired co2 rise triggered an increase in minute ventilation and respiratory rate, maintaining etco2 within normal values. in conclusion, after 80 minutes of mask use under resting conditions, there was no significant accumulation of co2 and no deleterious effects secondary to the observed elevation of inspired co2. it is likely that any accumulation under resting conditions will be minimal and automatically adjusted by the user by the normal physiologic response to co2 buildup. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint figure 21 data from co2 testing on dolfino frontier. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint currently, 3 exercise tests have been conducted by volunteers using the pneumask-g configuration. in the first 2 tests, the volunteer was a 38 years old male, asa 1 status, with weight of 83kg for a height of 1.80 m (2.03 m2 total body surface area by mosteller formula). both tests were performed at fio2 of 21% (ambient inspired oxygen fraction at a barometric pressure of 1011 hpa). in the first test, a decathlon freebreath mask was used with a 1.6 cmh2o pressure drop, bacterial/viral filter with no hme (heat and moisture exchanger). the mask has been worn on a treadmill at maximum inclination, for 10 minutes, to measure the co2 level during intense activity. for a constant running speed of 6mph, the inhaled co2 remained below 2mmhg at all times, while the exhaled co2 rises up to 48mmhg on peak physical effort. the second test was performed by the same volunteer subject, in the same treadmill machine, under same general conditions for 1 hour, with the pneumask-g configuration but with a hmef filter with a pressure drop of 4.5 cmh2o, which is almost 3 times higher than the filter used for the first test. for the second test, we monitored heart rate, spo2, non-invasive blood pressure (nibp), ecg, end-tidal co2, inspiratory co2, fio2, as well as a number of subjective measures including discomfort and stamina. the results of this test are summarized in 22. these results indicate that the change in inspiratory co2 throughout use of the device, in exertion that simulates that of most healthcare work, is negligible and in line with niosh standards [19] . subjective comfort/discomfort was rated from 1 of complete discomfort to 10 of complete comfort. it is notable that this never fell below a rating of a 7. further, the volunteer had an appropriate hr response for the level of exertion and no further alterations in physiological processes were noted. this indicates the device performs similar to elastomeric respirators under near identical conditions. the third qualitative testing was performed with pneumask-g configuration on a body glove tm snorkel mask on one of our co-authors. a series of capnographic measurements were performed using a closed anesthesia circuit including etco2, pressure, volume, and flow measurements. under normal respiration with an open mask purge valve, the etco2 is around 30 mmhg. under regular simulated operating room activities, there was no rise in etco2 noted for 30 minutes. once we closed the purge valve with tape, the etco2 rose to 33 mmhg with normal respiratory pattern. no rise was noted in etco2 with 30 minutes of regular or activities. work of breathing was noted to be more difficult in this setup. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . in an effort to better understand co2 buildup with different flow path configurations in different masks, our team has also begun to build cfd models of these masks (led by simon ellgas, waymo). we are in the process of building a platform to rank different designs and mask models by theoretical relative performance. the software used was siemen's star-ccm + ; the model used the segregated flow implicit unsteady solver, with the realizable k-epsilon urans turbulence model. computational runtime is around 8-9 hours per exhale-inhale cycle. we are currently solving these tests using 32 cores intel xeon on a desktop machine (not on a compute server). mesh size is 4.8m cells, so we have 150k cells per core. the timestep is set at 0.01s, to compromise between compute speed and quality, with a cfl number around ≈ 20. one-way valve modeling poses some challenges numerically in the model: to avoid the numerical cost of mesh motion, and the very thin gaps present during opening and closing of the purge valves, the valves are modeled by simply varying the porous resistance of a porous region at the location of the valve. therefore, the viscous resistance is set to a very high value to force the flow to practically zero when air would flow against the valve's direction. for flow in the valve's direction, the resistance is set to a value that reproduces the pressure drop across the valve in its full-open position. to be clear, the variable porous resistance is currently not set based on the local flow field at each valve, which would be more physical, but caused substantial numerical instability. instead, each valve's resistance parameter is set based on the global direction of the flow (inhaling, vs exhaling). this approach is only valid since the flow changes direction almost instantaneously throughout the computational domain. while this solution is pragmatic, and allows us to perform the desired qualitative ranking of the co2 buildup of different mask configurations with quick turn-around, it can indeed be further improved. these computational predictions of co2, flow rates and pressures -while they appear similar in range to experiments we report here -we caution readers that these computational models were built specifically to assess relative performance of different design configurations (different flow paths, mask models, etc.) and not absolute values that could be compared to experimental tests. we are currently extending these preliminary results to ask specific, targeted questions about relative performance of . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . different configurations. preliminary results comparing co2 between the stock-snorkel mask and the pneumask with filter and adapter are shown in figure 23 . the visibility of dolfino frontier has been extensively tested by multiple lab members, and no fogging was noted. the anesthesiologists among our co-authors also tested the same mask, and the mask did not interfere with a simulated intubation process nor with simulated standard anesthetic practices. the mask was found to reduce the volume of one's voice when worn, which can be overcome by users increasing their volume of speaking or by using our bluetooth microphone solution discussed further in the next section. the full-face snorkel mask can significantly muffle the user's voice, thereby inhibiting communication and requiring the user to strain their voice to communicate with others in a noisy environment [17] . in order to help sound travel past the mask, we created a mobile app to relay audio from a bluetooth microphone inside the mask to speakers outside the mask (figure 24 ). sound can either be played on the phone's internal speakers or through speakers connected to the device's wired headphone port. the download instructions and app user instructions are available in appendix c. all code is available on github at https://github.com/kylecombes/mic-repeater-android. this solution is currently only available on android platforms, although the team is currently working on the ios version, and hopes to release that soon. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . we have developed suggested donning and doffing procedures based on the recommendation of ucsf [26] and from stanford and ucsf feedback on our prototypes. a set of suggested procedures can be found in appendix d. due to the cost and design of the full-face snorkel mask, sustainable use requires that the mask itself be reused. thus, it will need to survive common decontamination procedures such as autoclaving or immersion in a bath of bleach or ethanol. we have performed preliminary tests in which we subjected the dolfino frontier mask to the conditions involved in common decontamination procedures; the mask is stated by the manufacturer to consist of either silicone or thermoplastic rubber and polycarbonate lenses. we have developed and tested our decontamination protocols based on recommendations from the cdc [21] , osha decontamination protocols for respirators [7] , and the consensus of national academy of science on reusable elastomeric respirators (p. 76) [8] . from these guidelines, a simple approach could potentially be the combined usage of detergent and bleach to achieve decontamination of the snorkel masks. besides sodium hypochlorite, there are other hospital-used disinfectants that meet the epa's criteria for use against sars-cov-2 [9] or cdc guidelines on chemical disinfectant use [10] . among these, some hydrogen peroxide solutions, such as accelerated hydrogen peroxide, offer the advantage of potentially being less harmful to the user and equipment, while only requiring a short contact time of just a few minutes. ethylene oxide sterilization is another commonly used method to disinfect heat sensitive equipment [11] ; however, it requires specialized equipment and facilities, and whether access to such services, with the required turnaround time, is widely available to health institutions needs to be determined. we first performed a preliminary test to check whether mask functionality survives over the course of multiple autoclaving cycles. before autoclaving the mask, we first took reference photos of its condition ( figure s2 ). we then autoclaved the mask using a 30 minute gravity cycle at 121 deg c and 15 psi, with 10 minutes of warm-up before sterilization and 30 minutes of drying afterwards. afterwards there was a mild "hot plastic smell". small scratches were found upon visual inspection of the black plastic material. after letting the mask rest for at least 30 minutes to cool down, we again autoclaved the mask for another identical 30 minute gravity cycle. the mask survived both cycles of autoclaving without damage. finally, we again let the mask rest for at least 30 minutes to cool down and then autoclaved the mask for another identical 30 minute gravity cycle. after this third round of autoclaving, with a cumulative autoclaving time of 90 minutes, the silicone rubber of the mask strap and mask seal appeared to remain elastic and functional. mask was worn after autoclaving with no apparent loss of function. besides autoclaving, the mask may be immersed in a bath of bleach for decontamination [12] . thus, we tested whether a mask could survive the relatively harsh chemical conditions of immersion in a bath of bleach. we immersed a new snorkel mask for 10 hours in a bath of 10% bleach. there was no apparent damage afterwards despite some white coating which can be easily washed off ( figure s3 ). we thus concluded that our mask should be able to survive most bleach disinfection protocols used in the hospital [7] . besides autoclaving and immersion in bleach, the mask may be immersed in a bath of ethanol for decontamination [12] . thus, we tested whether a new mask could survive immersion in a bath of 70% ethanol for 10 hours ( figure s4 ). no apparent damage was noted afterwards. (note that we should always use 95% ethanol to make the 70% ethanol solution, since 100% ethanol may contain trace amounts of benzene which is carcinogenic.) with our three snorkel masks treated under three different decontamination conditions (3 cycles of autoclaving, 10 hours of bleach immersion, and 10 hours of ethanol immersion, respectively), we then performed a simple stretch test on the elastomer bands of each mask by holding the strap with both hands such that the thumbs touched each other at the tips, then pulling and qualitatively observing the separation. the straps for the ethanol-treated mask appeared to have stretched the most, while the straps for the bleach-treated mask appeared to have stretched the least. nonetheless, all the masks are functional and seal well after all the cleaning processes. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . several reports indicate that dry heat at 65 degrees c is capable of killing any viral particles [13, 14] . although we did not explicitly test this protocol, given the fact that the masks survived 121 degrees c in the autoclave for 30 minutes, we can safely infer that our mask will also survive a dry heat disinfection protocol. based on above testing results and the recommendation from osha [7] , we developed suggested protocols for cleaning and decontaminating our snorkel mask (dolfino frontier), which is available in appendix b. please note that this protocol is not formally approved, and each hospital should consult their eh&s officers or infection disease specialists for a standard operating procedure. if you are using disinfectants other than bleach, please also check this table compiled by epa for recommended cleaning time. another important note is that not all snorkel masks can tolerate the decontamination. for example, snorkel masks from animdive, tinmiu and keystand cannot withstand the temperature of autoclave or industrial washers commonly used in or. if you are using snorkel masks other than dolfino frontier, please perform appropriate testing before usage. we have also performed a failure modes and effects analysis on our pneumask-g design. in this analysis, we first decomposed the product into different components and listed the primary functions of each component. we then analyzed what would happen if each component fail to serve their primary functions and how much negative impact it would bring. by considering the severity, chance of occurrence, and chance of detection of that malfunctioning scenario, we can compute a semi-quantitative score. by comparing the semi-quantitative score of each possible failure mode, we can identify the most important failure modes that require immediate action or improvement in design. the analysis suggested several points that may be useful for anyone to further build upon our system: (1) using surgical hood or any additional coverage to protect the filter surface, lateral side of the mask and the straps from gross contamination may provide additional protection (2) separating the airflow pathway for inhaled air and exhaled air as much as possible can further improve performance for the pneumask-g design. modification or blocking of the chin valve would require complete redesign of airflow pathway. (3) use a single-usage filter if available. for filters designed for repetitive usage, follow the instructions and regulatory-approved extended use claims (euc) of the manufacturers (4) avoid prolonged usage if possible (5) long-term durability of the adapter when subjected to many cleaning process cycles will likely be dependent on the exact material and manufacturing process. please perform appropriate further failure testing to characterize usage lifetime of these adapters in the material that is used. (6) instructions on cleaning should specifically mention the necessity of cleaning the valve, as discussed in step 5 of the decontamination protocol in appendix b. (7) use of voice amplifying system may help to minimize risk due to jaw movements (8) encourage face washing after doffing. we recognize that under normal circumstances, the adaptation of recreational sports equipment for medical usage would not be advisable, because of the availability of superior alternatives ( and more medically-specific in their overall design). a recent survey [3] shows that in the us, 31.4% of health care workers reported that there are no masks in their hospitals. the number of healthcare workers without access to suitable ppe will continue to grow if no additional efforts are made, due to a discrepancy between demand and available supply. with lack of ppe solutions for health care workers globally, new alternatives have to be explored. but even more critical than the design of these new solutions, is the rigorous and stringent evaluation of quantitative performance. here we perform stringent testing on topics ranging from co2 accumulation, fit testing, filtration efficiency testing and valve performance. • our tests found the pneumask capable of forming a seal that exceeds the standards required for half-face respirators or n95 respirators, through both quantitative and qualitative fit testing. we found this to be the case for both the dolfino frontier and the subea decathlon mask models. we encourage readers who wish to replicate our fit-testing results to perform quantitative fit testing with a very high performance hepa-rated inline filter (standard is 99.97% efficient for particles at 0.3 µm). this is to ensure that the fit of the mask (sealing capability of the mask) is evaluated separately from the filter performance. if no filter is available that operates >99% efficiency at breathing flow-rates, you may need to use specialized modes for fit testing (such as n95 mode on portacount devices). • work of breath on the overall system was evaluated qualitatively to be comfortable to the user with several different filter types for extended periods (1-3 hours). • filter testing indicates a range of options with varying performance depending on the quality of filter selected, but with typical filter performance exceeding or comparable to the n95 standard. if multiple filter options are available to clinicians, we recommend the usage of inline pleated, hydrophobic mechanical filters (such as the pall bb25 or bb50t) rather than electrostatic/viral filters. this is due to superior stated filtration performance in the specification of the filter, and also due to superior filter durability. extended use of filters in this context is still under evaluation. see table 15. • co2 buildup was found to be roughly equivalent to levels found in half-face elastomeric respirators in literature; between 1 and 2 percent. • we report results for average exhalation valve leakage of 1.5 ml/min at a suction of 25mm water-column height over 12 tests. this result indicates good performance when compared to the maximum niosh specification exhale valves (30 ml/min) at this pressure. we report a theoretical estimation of valve closure time of approximately 0.024 seconds. • clinical usability tests indicate sufficient visibility. clinical usability tests indicate speaking can be muffled, especially in noisy environments. in these environments, this muffled speech poses a technical challenge for users. we have developed an open-source amplification solution using hardware that many clinicians own personally: a bluetooth headset (or earbud) and a smartphone. this solution is optional for users, and will depend on individual preferences and occupational circumstances. the android app is available, the ios version is still under development. • while not intended for extreme extended usage, durations on the order of 4-6 hours of continuous use in clinical environments have been reported by international partners (in france and chile). • we present guidance on the assembly, usage (donning and doffing) and decontamination protocols. testing of decontamination protocols indicate reuse of the snorkel masks is technically feasible. additionally, we recognize that beyond being an alternative to n95 respirators (and protective goggles/face shields), pneumasks can be combined with a disposable hood to leave no directly exposed hairs or skins that are otherwise susceptible to being contaminated with droplets ( figure 25 ). without pneumasks, this kind of protection is only achievable with papr or the use of surgical hood/coveralls, which may also be in short supply and are associated with a more complex doffing process [27] . in the context of a dire worldwide shortage of ppe for medical personnel, and where no other approved alternatives are available, we are cautiously optimistic about the performance and efficacy of this system as an n95-alternative technology. figure 25 pneumasks can be used with a disposable plastic hood to offer additional droplet protection. also shown as references are uses of surgical hood and papr [27] . the fda has issued emergency use authorization (eua) for ppe, including niosh approved respirators, which has significantly altered the clearance process for solutions such as ours. we are actively seeking guidance from the fda for our approach in order to provide regulatory clarity to our partners and clinical sites to expedite implementation. it is our understanding that this approach will allow for niosh approved filtration and meet or exceed fit specifications for n95 and elastomeric respirators currently authorized by the eua. upon further discussions with the fda, we have received the following communication regarding use solutions such as the full-face snorkel mask ppe: . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint fda recognizes the urgent need for face masks in the setting of the covid-19 pandemic due to increased use and shortages in their availability. fda does not object to the marketing and distribution of face masks in the healthcare setting without prior 510(k) clearance if the product is labeled in the following manner: 1. it states it may be used when fda cleared masks are unavailable; 2. it recommends against use in a surgical setting or where significant exposure to liquid bodily or other hazardous fluids may be expected; 3. it makes no claims of antimicrobial or antiviral protection; 4. it makes no claims of infection prevention or reduction; 5. it makes no claims regarding flammability 6. the labeling contains a list of the body contacting materials. 7. the mask is not labeled as a "surgical mask"; rather it may be labeled as a "face mask" in addition, fda does not intend to object to marketing of masks that meet the above criteria even if they are manufactured at facilities that do not meet 21 cfr 820. as an update, on 3/25/2020, the us fda issued updated guidance titled "enforcement policy for face masks and respirators during the coronavirus disease (covid-19) public health emergency"(fda-2020-d-1138). in summary, this guidance now covers solutions such as the reusable full-face snorkel mask ppe project with the following (pg3): fda recognizes that, when alternatives, such as fda-cleared masks or respirators, are unavailable, individuals, including healthcare professionals, might improvise ppe. fda does not intend to object to individuals' distribution and use of improvised ppe when no alternatives, such as fda-cleared masks or respirators, are available. the cdc has published guidelines on crisis/alternate strategies for ppe decisions in the setting of n95 respirator shortages. at this time, our solution can be considered a case of "hcp use of non-niosh approved masks or homemade masks" which is permissible in a setting where n95 respirators are so limited that routine use of them is no longer possible and surgical masks are not available. while we believe and have documented that our solution can provide higher levels of protection than homemade or simple cloth masks, we cannot make legal claims at this time until further guidance is received from regulatory authorities. this project was a global collaborative effort that crossed typical boundaries between academic, industry, government and medical institutions. convergent design on this concept occurred nearly simultaneously in many different regions throughout the world on this work, and it brought together a highly diverse and driven community. for more information on the consortium of industrial and institutional contributors to this project who are involved with the development and distribution of pneumask in the united states, please reference: www.pneumask.org. for europe and france, see involved entities here: (https://adaptateur-masque.planktonplanet.org/). . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint figure 27 global efforts on design effort by our team of collaborators worldwide. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04. 24.20078907 doi: medrxiv preprint this has been a large community projects with support from global community including clinicians who have given us feedback throughout. we thank everyone who has engaged with the pneumask community, specially international community working to build solutions for the current ppe shortage. we thank schmidt futures, moore foundation, autodesk and cz biohub for financial support of the project. we thank boston scientific and medtronics staff for support in development of injection molding parts and overall consultation. we thank mitre and helena for conversations around equitable distribution and members from pall corporation for discussions around filter efficiency. gerry ayala (wildhorn outfitters), quentin allinne (subea decathlon), and dave kasper (isnorkel inc) have company affiliations with snorkel-mask manufacturers or distributors. they consulted on original designs of these masks, and in some cases to help with adapter design strategy. none of the scientific data included in this report, nor the conclusions of this report were written or substantially influenced by these co-authors. john pearson, md has a conflict of interest, as a stake holder in a for-profit entity focused on snorkel-based ppe. patrick kolbay is volunteering his time at this company. we certify that none of the other authors have any affiliations with or involvement in any organization or entity with any financial interest in the subject matter or materials discussed in this manuscript. none of the other authors (beyond what is listed above) have any affiliations with john pearson's company. this is an early preprint of this article intended for an preprint online platform. this article is intended for submission to a peer-reviewed journal at a later date. we are sharing this openly to enable others to find and replicate this work and engage to further improve this in an open manner. please reference the below link for hyperlinked tables (at the end of this live lab-notebook): https://docs.google.com/ document/d/1j22le3dbzbnndxgljlrb38z7v7laojkfden9f0tfeky/edit?usp=sharing, but are also shown below. table s1 , part 1 of 2: list of commercially available respiratory filters which are initially designed for ventilators. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint table s1 , part 2 of 2: list of commercially available respiratory filters which are initially designed for ventilators. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint table s2 , part 1 of 1: list of commercially available filters which are not initially designed for medical usage. more characterizations of the filtering abilities are required before using in a hospital setting. the star marks next to the product name indicate the ones prakash lab is planning to test. (n/a = not available.) . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint table s4 , part 1 of 2: list of commercially available p100 respirator filters/cartridges originally for industrial usage. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint table s4 , part 2 of 2: list of commercially available p100 respirator filters/cartridges originally for industrial usage. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint table s5 , part 1 of 2: list of epa-certified wipes. it is ordered by required contact time. all listed products are approved for healthcare use. if a product qualifies for the emerging viral pathogen claim, it is effective against a harder-to-kill virus than human coronavirus. all products on this list meet epa's criteria for use against sars-cov-2, including those marked as "no" in this column. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint table s5 , part 2 of 2: list of epa-certified wipes. it is ordered by required contact time. all listed products are approved for healthcare use. if a product qualifies for the emerging viral pathogen claim, it is effective against a harder-to-kill virus than human coronavirus. all products on this list meet epa's criteria for use against sars-cov-2, including those marked as "no" in this column. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04. 24.20078907 doi: medrxiv preprint . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04. 24.20078907 doi: medrxiv preprint . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04.24.20078907 doi: medrxiv preprint . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 29, 2020. . https://doi.org/10.1101/2020.04. 24.20078907 doi: medrxiv preprint how to train the health personnel for protecting themselves from novel coronavirus (covid-19) infection during their patient or suspected case care critical supply shortages -the need for ventilators and personal protective equipment during the covid-19 pandemic protecting the healthcare workers during covid-19 pandemic: a survey of infection preventionists uv sterilization of personal protective equipment with idle laboratory biosafety cabinets during the covid-19 pandemic sourcing personal protective equipment during the covid-19 pandemic surgical n95 vs . standard n95 -which to consider? app b-2 -respirator cleaning procedures (mandatory). | occupational safety and health administration reusable elastomeric respirators in health care. reusable elastomeric respirators in health care disinfectants for use against sars-cov-2 | pesticide registration | us epa chemical disinfectants | disinfection & sterilization guidelines | guidelines library | infection control | cdc ethylene oxide sterilization of medical devices: a review filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods evaluation of inactivation methods for severe acute respiratory syndrome coronavirus in noncellular blood products stability and inactivation of sars coronavirus viable viral efficiency of n95 and p100 respirator filters at constant and cyclic flow surgical face masks and downward dispersal of bacteria speech intelligibility assessment of protective facemasks and air-purifying respirators headaches and the n95 face-mask amongst healthcare providers reusable elastomeric respirators in health care: considerations for routine and surge use unmanned assessment of respirator carbon dioxide levels: comparison of methods of measurement guideline for disinfection and sterilization in healthcare facilities reusable elastomeric air-purifying respirators: physiologic impact on health care workers 3m's collaboration on covid-19 supply challenges and price gouging why, where, and how paprs are being used in health care. in the use and effectiveness of powered air purifying respirators in health care: workshop summary training and fit testing of health care personnel for reusable elastomeric half-mask respirators compared with disposable n95 respirators droplet + contact isolation donning and doffing-sequence for putting on personal protective equipment available at niosh standard exhalation valve leakage test requirements. specifications available at suggested decontamination protocols 1. perform hand hygiene. 2. put on a gown, gloves, and a protective mask wipe the surface of the filter with 70% ethanol or hydrogen peroxide, and carefully remove the filter discard the filter if it is intended for single-use only wash mask and filter adapter thoroughly in warm water (43 deg c [110 deg f] maximum) with a mild detergent. a stiff bristle (not wire) brush may be used to facilitate the removal of dirt rinse the mask and adapter thoroughly in clean, warm (43 deg c [110 deg f] maximum), running water prepare enough solution to fully immerse the entire mask. remove all the air in the side channel to ensure full immersion. please note that mixing bleach solutions with detergents can generate toxic substances immerse the mask and adapter in the hypochlorite solution (50 ppm of chlorine) for 2 minutes wearing fresh gloves, rinse the mask and adapter thoroughly in clean, warm, running water (43 deg c [110 deg f] maximum). the mask and adapter must be thoroughly rinsed with water to remove any detergents or disinfectants that may gently disconnect the filter from the mask. dispose the filter if it is designed for one-time usage wipe the surface of the ziplock bag with epa-approved wipe (appendix a table 5) and open the ziplock bag. perform hand hygiene. dump the microphone from the ziplock bag with one hand (dirty hand) onto the other hand (clean hand). dispose the ziplock bag with your dirty hand. place the microphone somewhere you will not forget with your clean hand by the end of the shift, bring the box and the mask to somewhere you can fully decontaminate it following our decontamination protocol, or hand it to hospital technicians per hospital policy. the recommendation of using disinfection wipe between patients and fully washing it after one shift is following the recommendation of niosh on elastomeric respirator key: cord-288569-sitxa2ul authors: smereka, jacek; ruetzler, kurt; szarpak, lukasz; filipiak, krzysztof jerzy; jaguszewski, milosz title: role of mask/respirator protection against sars-cov-2 date: 2020-04-20 journal: anesth analg doi: 10.1213/ane.0000000000004873 sha: doc_id: 288569 cord_uid: sitxa2ul nan to the editor s ince its outbreak on december 31, 2019, in wuhan, a central city in china, coronavirus disease 2019 (covid-19) has now spread to almost all countries in the world. it has been declared a pandemic, and it has infected over 1,041,126 people in a very short time, with 55,132 deaths as of april 3, 2020. wearing masks/respirators and practicing self-isolation at home have been recommended as guidelines for the public. however, the problem is the number of cases among medical personnel. interestingly, a higher risk of infection was noticed in male professionals. 1 there are currently many types of masks/respirators available, ranging from simple surgical masks designed to protect wearers from microorganism transmission and fit loosely to the user's face, through n95 masks used to prevent users from inhaling small airborne particles. these must fit tightly to the user's face. 2 masks differ primarily in their maximum internal leakage rate limit. surgical masks are designed to protect against droplets or particles with a diameter of >100 μm, whereas severe acute respiratory syndrome coronavirus 2 (sars-cov-2) virus is essentially spherical, albeit slightly pleomorphic, with a diameter of 60-140 nm and 100 times smaller than the pore diameter. thus, surgical masks cannot prevent inhalation of small airborne particles; however, both can protect users from large droplets and sprays. 3, 4 the pn-en 149:2001 standard defines 3 protection classes for half masks: filtering face piece 1 (ffp1), filtering face piece 2 (ffp2), and filtering face piece 3 (ffp3). the maximum internal leakage limit is 25% for ffp1, 11% for ffp2, and 5% for ffp3. class ffp1 masks retain about 80% of particles smaller than 2 μm, ffp2 ones retain 94% of particles smaller than 0.5 μm, and ffp3 ones retain 99.95% of particles smaller than 0.5 μm (table) . at the moment, we may meet divergent recommendations for the use of masks. while the centers for disease control and prevention recommend the use of masks in low-risk and high-risk situations, the world health organization advises applying masks in lowrisk situations and respirators in high-risk situations. long et al 5 conclude in their meta-analysis that the use of n95 respirators compared with surgical masks is not associated with a lower risk of laboratory-confirmed influenza. they suggest that n95 respirators should not be recommended for the general public and non-high-risk medical staff who are not in close contact with influenza patients or suspected patients. the potential of face masks to reduce the spread of respiratory infections could be useful. wang et al 1 indicated that 10 of 213 medical professionals with no mask were infected by covid-19 as compared with 0 of 278 wearing n95 respirators. it is also worth noting that the respirator increases resistance to inhalation. the longer they are used, the more difficult breathing becomes because of more absorbed dust. what is more, the effectiveness decreases with the increase of carbon dioxide and water vapor between the respirator and face (the socalled dead space). the concentration of carbon dioxide in the dead space increases with each subsequent exhalation. therefore, masks should be replaced frequently. additionally, to improve the comfort of use, masks use 1-way exhalation valves, which accelerate the circulation of gases. 6 to conclude, the use of protective masks can and should be the first protection against sars-cov-2 transmission to medical personnel. medical personnel should use class ffp3 masks. additionally, the application of visors to cover the entire face during contact with the patient is worth considering. association between 2019-ncov transmission and n95 respirator use comparison of performance of three different types of respiratory protection devices protecting healthcare staff from severe acute respiratory syndrome: filtration capacity of multiple surgical masks a close shave? performance of p2/n95 respirators in health care workers with facial hair: results of the beards (adequate respiratory defences) study effectiveness of n95 respirators versus surgical masks against influenza: a systematic review and meta-analysis cloth masks versus medical masks for covid-19 key: cord-148354-3nl3js2x authors: kumar, vivek; nallamothu, sravankumar; shrivastava, sourabh; jadeja, harshrajsinh; nakod, pravin; andrade, prem; doshi, pankaj; kumaraswamy, guruswamy title: on the utility of cloth facemasks for controlling ejecta during respiratory events date: 2020-05-05 journal: nan doi: nan sha: doc_id: 148354 cord_uid: 3nl3js2x the utility of wearing simple cloth face masks is analyzed using computational fluid dynamics simulations. we simulate the aerodynamic flow through the mask and the spatial spread of droplet ejecta resulting from respiratory events such as coughing or sneezing. without a mask, a turbulent jet forms, and droplets with a broad size distribution are ejected. large droplets (greater than about 125 {mu}m in diameter) fall to the ground within about 2 m, while turbulent clouds transport a mist of small aerosolized droplets over significant distances (~ 5 m), consistent with reported experimental findings. a loosely fitted simple cotton cloth mask (with a pore size ~ 4 microns) qualitatively changes the propagation of the high velocity jet, and largely eliminates the turbulent cloud downstream of the mask. about 12% of the airflow leaks around the sides of a mask, considering a uniform gap of only 1 mm all around, between the face and the mask. the spread of ejecta is also changed, with most large droplets trapped at the mask surface. we present the viral load in the air and deposited around the person, and show that wearing even a simple cloth mask substantially decreases the extent of spatial spread of virus particles when an infected person coughs or sneezes. there is consensus 1, 2, 3, 4 that the use of surgical facemasks and n95 respirators help control the transmission of respiratory diseases such as influenza. therefore, the use of these personal protective equipment (ppe) has been recommended 5 for health care personnel, infected patients and their care givers. to ensure that surgical masks and n95 respirators are available to those at greatest risk of infection, the world health organization 6 and national agencies have recommended against their use by the general public. even so, greatly increased demand during the covid-19 pandemic has seen a global shortage of such ppe. since surgical masks and n95 respirators are not readily available to the public, the use of simple homemade reusable cloth facemasks has been suggested 7,8 as a protective measure, especially due to the possibility 9 of asymptomatic disease transmission. however, there has been considerable controversy 10, 11, 12, 13 over the efficacy of home-made reusable cloth face masks. one report 14 suggests that the use of a homemade face mask would be better than "no protection at all". in south east asian countries, the practice of using face masks for combating pollution or for personal hygiene is widespread. this has been cited 15 as an important factor in controlling the transmission of covid-19 infections. however, there are concerns that the use of facemasks may decrease the rigour in following strict physical distancing and handwash hygiene. further, incorrect use of masks, for example, wearing masks incorrectly or touching the outer surface of masks can result in adverse outcomes. sars-cov2 has been found 16 on the surface masks worn by infected patients, and has been shown 17 to remain viable on the surface of surgical masks for several days. therefore, a detailed understanding of the benefits of wearing homemade cloth masks would be useful in determining policy on their recommended and possible mandatory use. sars-cov2, the virus responsible for the covid-19 pandemic, infects cells in the upper respiratory system. transmission of covid-19 is currently believed 18, 19, 20 to happen primarily through shedding of virus particles in droplets ejected as infected people speak, cough or sneeze, or through contact with viable infective virus deposited on surfaces. when people cough or sneeze 21 (or even simply talk loudly 22, 23 ) , they eject droplets of mucosal fluid. large droplets ~o(100 µm) fall due to gravity and, under no wind conditions, are transported over lateral distances of the order of 1 m. however, turbulent flows resulting from violent expulsions during sneezing or coughing suspend finer droplets and transport them over large distances, of the order of 7-8 m. 24, 25, 26 therefore, it has been suggested that transmission of infection through fine droplets be investigated. 27, 28, 29 the effect of surgical masks and n95 respirators on airflows (but not spread of droplet ejecta) during expiratory events has been experimentally imaged. 30 here, we employ computational fluid dynamics (cfd) simulations to address the influence of homemade face masks on the turbulent clouds that result due to sneezing events, and on the lateral extent of spread of ejecta. our emphasis is on understanding the effect of face masks in altering the flow field and droplet dispersion due to the respiratory event. respiratory events (sneezing or coughing) and the resultant spread of ejecta are modeled as two-phase flow using ansys fluent software 2020 r1. the carrier fluid (air) is represented as a continuum phase, and mucosal droplets are represented as the discrete phase. mucosal droplets are assumed to have properties of water. we model the dynamics of turbulent air jets using timeaveraged navier-stokes mass and momentum conservation equations. the renormalization group (rng) k-epsilon model is used to model the turbulence, allowing us to span high velocity turbulent flows to lower velocity flows. we employ the enhanced wall treatment model in combination with rng k-epsilon model to account for the viscous sublayer near the wall surface. a detailed description of the equations and models is given elsewhere, 31 and a brief summary is provided in the supporting information (section a). for the discrete droplet phase, equations of motion are solved for each droplet to model its trajectory. droplets can exchange mass (due to vaporization), momentum and energy with the continuous fluid phase. droplets are convected by the continuous phase and can, in turn, affect the flow of the continuous phase (two way coupling between the fluid and droplet phase). to reduce computational time, half the domain is simulated assuming symmetry in geometry and flow features. ambient conditions (35 o c, 60% relative humidity) representative of summer conditions in india are assumed. in our simulations, a human face is included in the domain 2 m from the left surface, at a height of 1 m from the ground level, and the mouth is represented as a 2 cm 2 opening facing right. experimentally, it has been observed 24,30,33 that respiratory events result in jets angled towards the ground, with some variability in the angle. we followed previous simulations 32 that model the respiratory event as a jet emanating from the mouth in the horizontal direction. for this jet, a time dependent velocity profile is applied with the peak velocity of 50 m/s at 0.1s. values for the peak flowrate (= 6 l/s) and the total volume expelled (= 1 l) are obtained from gupta et al. 33 we do not describe the detailed breakup of the ejecta into droplets. rather, we prescribe the size distribution of droplets in the ejected spray as a rosin-rammler distribution with droplet sizes ranging from 1 to 500 µm. droplets ejected are not allowed to coalesce or break-up. based on previous work, 32 we consider that 94% of injected droplet mass can evaporate and the remaining 6% represents non-volatile matter. following aliabadi, 32 we inject 6.1 mg of droplets over 10 equal injections with initial droplet positions staggered over 1 cm. the cloth mask is not tightly fitted around the face, representative of homemade masks. therefore, we model the mask as covering 22% of the face area around the nose and mouth and model air leaks by considering a uniform gap of 1 mm all around, between the face and the mask. the area of the gap around the mask is about 2% of the mask area. to model 34 the resistance presented by the mask to the flow of air, we consider the mask as an isotropic porous medium, with darcy and inertial contributions to the pressure drop, given by: where si is the source term in the momentum equation, µ is the fluid viscosity, vi is the velocity, α is the permeability and c2 is the inertial resistance factor. we consider a mask made of cotton cloth, and obtain α and c2 from a fit to experimental data presented in the literature 35 (details in si -section a). to model the permeation of droplet ejecta, we follow experimental reports 36 of the penetration efficiency of fabric. we consider an effective pore size of 4 µm for the cotton cloth and impose a trap condition so that all droplets larger than the pore size are trapped by the mask. more details about the governing equations, computational method and validation can be found in the supporting information (section a). the instantaneous flow field 0.1 s after the respiratory event without and with masks, respectively, is shown in figures 1 a, b (close ups: figures 1 c, e) . we represent the flow field using streamlines and present data in the symmetry plane passing through the face. without a mask (figure 1 a, c) , the respiratory event results in an air jet with a fast moving turbulent core that entrains ambient air and slows down as it propagates from the face. as the surrounding air is entrained, the jet forms a conical shape with a cone angle = tan -1 (radius/height) ≈ tan -1 (0.2) = 11.3 o , corresponding to an entrainment coefficient slightly lower than that reported in the literature 24 there is a qualitative change in the airflow when a mask is worn (figure 1 b, e). here, the turbulent jet and strong recirculating flows are eliminated by the mask and about 12% of the air flow is diverted through the openings at the sides of the mask to create a qualitatively different flow around the face. we reiterate that the area of the openings (considering a uniform gap of 1 mm all around, between the face and the mask) represents only about 2% of the area of the mask. this leakage flow is similar to experimental reports 30 of flows using surgical masks (which are also not tightly fitted). correspondingly, we observe a drastic change in the spatial distribution of the turbulent kinetic energy when a mask is worn (compare figure 1 d with 1 f, plotted through the symmetry plane at t = 0.1 s). without a mask, a highly turbulent jet with large mean square velocity fluctuations propagates axially away from the face (figure 1 d) . this is virtually eliminated by the mask (figure 1 f) . at t = 0.1 s, the centerline velocity through the face decreases from ≈ 50 m/s to ≈ 40 m/s over 0.2 m. we note that the velocity reported here is exactly at the centreline. therefore, these values are higher than the experimentally measured peak velocities of the jet, that are likely averaged around the centreline. at 0.2 s after the respiratory event, the centreline velocity immediately after the face is about 30 m/s, and decreases to about 20 m/s at 0.2 m. in contrast, the centreline velocities drop to less than 5 m/s within 0.02 m when a mask is worn (figure 1 f) . correspondingly, when no mask is worn, the centerline turbulent kinetic energy decreases from about 8 m 2 /s 2 to 2 m 2 /s 2 at 0.05 m from the face at t = 0.1 s, and then rises to 47 m 2 /s 2 at a distance of 0.25m from the face as the entrained air forms a turbulent cloud (figure 1 h). when a mask is worn, the turbulent kinetic energy rises near the mask due to the increase in mean square velocity fluctuations as the expelled jet impinges on the mask. however, due to the resistance to the flow presented by mask, it rapidly decreases immediately after the mask and approaches 0 m 2 /s 2 at 0.04 m from the face. the dissipation of the turbulent flow field tracks the trend in the turbulent kinetic energy. without a mask, it decreases by about 10-fold over 0.05 m (for t = 0.1 s) and then rises reaching a maximum at 0.2 m, while wearing a mask results in a rapid decrease by over 3 orders of magnitude over a distance of 0.05 m (figure 1 i) . wearing a mask has a significant impact on the spread of cough ejecta. we observe the time dependent trajectories of large and small droplets with time from the respiratory event (figure 2 ). without a mask (figure 2, top panel) , large drops are not convected by the flow and rapidly fall to the ground: drops > 200 µm fall within a lateral distance of 0.2 m, while drops > 125 µ m extend to about 2 m (si, figure s6 ). in contrast to the large drops, smaller drops (< 25 µ m in size) are convected by the turbulent cloud. they shrink in size as their water content is completely evaporated, and are transported to significant distances, as far as 5 m from the face (si, figure s7 ). we observe that the non-volatile content in these drops continues to stay suspended for as long as 60 s. our data is consistent with the experimental literature. 25 wearing even a simple cotton mask restricts the spatial transport of droplets (figure 2 , bottom panel). large droplets (> 4 µm) are trapped by the mask while smaller droplets are transported by the flows through the surface of the mask and through the openings on the sides. at t = 0.4 s, droplet ejecta is transported over less than 0.3 m (as compared to well over 2 m, without a mask). thus, large droplets are trapped by the mask while the damping of the turbulent flow field by the mask leads to smaller droplets being transported only over relatively short distances. flow through the openings around the mask convects small droplets along the face, in contrast to the case without a mask. we estimate the potential viral concentrations suspended in the air and deposited on the floor due to propagation of droplets from the respiratory event of an infected person. recent literature 37 indicates that the sars-cov2 load in throat swabs on patients within the first 5 days of the infection averages 6.76 x 10 5 rna copies/ml. for sputum samples, an average of 7 x 10 6 rna copies/ml was observed. based on these, in these simulations we assume a representative viral concentration of 10 6 particles/ml in the ejecta, to estimate the potential spatial dispersion of the virus. when an infected person not wearing a mask sneezes or coughs, virus particles in the large droplets rapidly drop to the floor. by t = 60 s, ≈ 37% of the potential viral load in the ejecta is deposited on the floor while ≈ 63% remains in the air. most of the virus particles that are deposited on the floor are within 2 m from the person, with a maximum virus density ≈ 10 cm -3 at about 0.2 m from the person (figure 3 a, d) . the suspended aerosolized virus particles form a low density cloud that extends from 2 to 5 m. at the centerline passing through the face, the suspended concentration ≈ 10 -3 cm -3 (figure 3 a, c) . when a mask is worn, most of the virus-laden droplets (nearly 70%) are deposited on the mask. flow through the mask surface and leakage flows from the openings around the mask result in generating a cloud, potentially conveying virus to a distance of about 1.5 m from the face. at the centerline passing through the face, this cloud has a density of 10 -2 cm -3 within about 1.5 m from the person (figure 3 b, c) . however, the suspended concentration drops significantly after 1.5 m from the person, and there is virtually no deposition of droplets on the ground (figure 3 b, c) . thus, there is a clear qualitative difference in the distribution of virus particles when the infected person wears a mask. without a mask, high concentrations of potentially virus-laden droplets are deposited on the floor within 2 m of the person and a dilute suspended cloud is observed over 2 -5 m. in contrast, when a mask is worn, there is no deposit on the ground since most of the virus is deposited on the mask. virus particles stay suspended within 1.5 m of the person, but this suspended concentration falls off sharply after that distance. our simulation results conclusively demonstrate that wearing even just a simple cotton mask has a dramatic influence on the air flow and spread of ejecta after a respiratory event. when a person not wearing a mask coughs or sneezes, the emanating jet sets up turbulent flows at distances of several meters from the person. while the large mucosal droplets fall to the floor within a distance of 2 m, the turbulent clouds continue to suspend aerosols at distances up to 5 m, for over a minute after the respiratory event. when an infected person coughs or sneezes, most of the virus deposits on the floor within a meter of the person. however, a dilute aerosol stays suspended, potentially carrying virus particles. in contrast, wearing a mask dissipates the turbulent flows passing through the mask, and diverts about 12% of the flow to the openings at the sides of the mask. the vast majority of the virus particles are retained on the mask and face. at t = 60 s, a cloud of virus particles (10-fold higher in density compared to the case without the mask) stays suspended within 1.5 m of the person. our results strongly suggest that airborne transmission from patients (especially asymptomatic or presymptomatic patients) can be greatly reduced by wearing a simple cotton mask and maintaining strict physical distancing of 2 m. the fluid phase is treated as a continuum by solving the navier-stokes equations, while the dispersed phase is solved by tracking droplets through the calculated flow field. the dispersed phase can exchange momentum, mass, and energy with the fluid phase. the dispersed phase is treated by the lagrangian approach, where a large number of droplet parcels, representing a number of real droplets with the same properties, were traced through the flow field. by representing droplets by parcels, one can consider size distribution and simulate the measured liquid mass flow rate at the injection locations by a reasonable number of computational droplets. the trajectory of each droplet parcel is calculated by solving the equation of motion for a single droplet. the droplets in the dispersed phase are modelled using the discrete phase model (dpm). in this approach, a lagrangian frame of reference is used to calculate the trajectories of a large number of droplets representing real droplets with the same properties, by integrating the forces acting on droplets. the droplets can exchange mass, momentum and energy with the fluid. the force balance on each droplet can be written as: where is the particle mass, ⃗ is the fluid velocity, ⃗ is the droplet velocity, ρ is the fluid density, ρp is the density of the droplet, ⃗ is an additional force, ⃗ ⃗ is the drag force, and is the droplet relaxation time calculated by = 18 here, µ is the molecular viscosity of the fluid, and dp is the diameter of the droplet. the relative reynolds number re is defined as the drag coefficient is calculated considering spherical particles. the dispersion of droplets due to turbulence in fluid phase is included using the stochastic tracking (random walk) model which includes the effect of instantaneous turbulent velocity fluctuations. for evaporating droplets, inert heating/cooling along with vaporization laws are applied. more information about the energy treatment of the dpm droplets and evaporation rate can be found in ansys fluent 2020r1 help manual. other fluid-droplet and droplet-droplet interactions are ignored in the study. the droplets are two-way coupled into the continuum fluid phase to make it possible for the droplets to influence the continuous fluid phase. we model the effect of wearing a woven cloth face mask as follows: the mask is included in the cfd model as a thin volume and modeled as porous media. for the current study the media is considered to be homogeneous and the resistances included via this media are considered to be isotropic in nature. porous media are modeled by the addition of a momentum source term to the standard fluid flow equations. the source term is composed of two parts: a viscous loss term (darcy, the first term on the right-hand side of equation 4 , and an inertial loss term (the second term on the right-hand side of equation 4) where si is the source term for the i th (x, y , or z ) momentum equation, µ is the dynamic viscosity of fluid , v is the magnitude of the velocity and dij and cij are prescribed matrices. this momentum sink contributes to the pressure gradient in the porous cell, creating a pressure drop that is proportional to the fluid velocity (or velocity squared) in the cell. to recover the case of simple homogeneous porous media where α is the permeability and c2 is the inertial resistance factor, obtained by specifying d and c as diagonal matrices with diagonal values of 1/α and c2 , respectively (and zero for the other elements). we consider a mask prepared from cotton cloth. details of the cloth used are taken from the thesis 1 of saldaeva. details of the construction of the fabric as provided in the thesis are given in table s1 . pressure drop versus velocity data obtained from the thesis and shown below in figure s1 can be fitted to obtain the darcy (proportional to v) and non-darcy inertial (proportional to v 2 ) components of the resistance to flow. for the jet coming from the mouth, a time dependent velocity profile is applied with peak velocity time (pvt) of 0.1 sec as shown in figure s3 . cough peak flowrate (cpfr) is derived using the formulation reported by gupta et al. 3 to simulate varied human expirations, various cough expired volume (cev) values are used corresponding to very weak, medium and very strong expirations. to simulate the spray of droplets, a rosin-rammler distribution method is used for the injection. 94% of injected droplet mass fraction represents evaporating sprays and the remaining 6% represents the non-volatile matter. a total 6.1 mg of droplets are injected using 10 injections with equal distribution among the injections. the initial droplet positions are staggered over 0.01 m. conditions used for the baseline simulation are shown in table s2 . a user defined function (udf) has been used to filter the droplets from the mist generated by the respiratory event. we model filtration by cloth with reference to reported experimental literature. guyton et. al. 4 measure the filtration efficiency of a single layer of fabric typical of bath towels, cotton shirts, handkerchiefs, etc. and report the penetration efficiency of 2 µm particles. rengasamy et. al. 5 report the penetration efficiency of cotton cloth for a range of particle sizes (up to 1 m in size). we use a conservative estimate for the penetration efficiency of the cotton mask used in this work and implement a simplified filtering mechanism such that all droplets above 4 µm diameter are filtered out while droplets below 4 m are allowed to pass through the mask. this boundary condition is applied when the droplets hit the surface of the mask. the baseline case is created to validate the methods used simulate near field cough, particle dispersion, heat and mass transfer in a still environment. the results from the baseline cfd simulation are verified against results from aliabadi et. al. 2 in figure s4 (a) , average droplet diameter in each of the diameter bins are plotted against time. figure s4 (b) shows the vertical penetration of the droplet plumes in the gravity direction. in the current work, penetration is computed as the location where 98% of the total mass of the droplet is contained. the exact approach taken by aliabadi et. al. 2 to compute penetration length is not known. some differences may be expected because of this uncertainty as wells as the uncertainty about the exact location of the duct. we employ a geometry representing a 5m x 6m x 6m domain with a small duct of 0.2m x 0.2m placed opposite side of the inlet plane. half of the computational domain is simulated by placing a symmetry boundary condition in the middle. the computational domain is discretized into 1.8 million elements with a mix of polyhedral and hexahedral elements using ansys fluent 2020r1 mesh creation tools as shown in figure s5 . the conditions used for the simulation presented in this paper are shown in table s3 . b. additional simulation results, as referred to in the main manuscript are presented here. respiratory virus shedding in exhaled breath and efficacy of face masks potential utilities of mask wearing and instant hand hygiene for sars-cov-2 a cluster randomised trial of cloth masks compared with medical masks in healthcare workers effectiveness of n95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis covid-19, shortages of masks and the use of cloth masks as a last resort mass masking in the covid-19 epidemic: people need guidance rational use of face masks in the covid-19 pandemic not wearing masks to protect against coronavirus is a 'big mistake,' top chinese scientist says would everyone wearing face masks help us slow the pandemic? testing the efficacy of homemade masks: would they protect in an influenza pandemic? disaster medicine and public health preparedness covid-19: face masks and human-to-human transmission effectiveness of surgical and cotton masks in blocking sars-cov-2: a controlled comparison in 4 patients stability of sars-cov-2 in different environmental conditions community transmission of severe acute respiratory syndrome coronavirus 2 early transmission dynamics in wuhan, china, of novel coronavirusinfected pneumonia clinical features of patients infected with 2019 novel coronavirus in wuhan facemasks for the prevention of infection in healthcare and community settings aerosol emission and superemission during human speech increase with voice loudness visualizing speech-generated oral fluid droplets with laser light scattering violent expiratory events: on coughing and sneezing visualization of sneeze ejecta: steps of fluid fragmentation leading to respiratory droplets experimental investigation of far field human cough airflows from healthy and influenza-infected subjects turbulent gas clouds and respiratory pathogen emissions. potential implications for reducing transmission of covid-19 controversy around airborne versus droplet transmission of respiratory viruses: implication for infection prevention an investigation of liquid droplet evaporation model used in multiphase flow simulation cfd simulation of human coughs and sneezes: a study in droplet dispersion, heat and mass transfer flow dynamics and characterization of a cough estimation of viscous and inertial resistance coefficients for various heat sink configurations through thickness air permeability and thermal conductivity analysis for textile materials simple respiratory protection-evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles virological assessment of hospitalized patients with covid-2019 through thickness air permeability and thermal conductivity analysis for textile materials cfd simulation of human coughs and sneezes: a study in droplet dispersion, heat and mass transfer flow dynamics and characterization of a cough emergency respiratory protection against radiological and biological aerosols simple respiratory protection-evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles key: cord-257997-btj4ckkz authors: wen, zhanbo; yu, long; yang, wenhui; hu, lingfei; li, na; wang, jie; li, jinsong; lu, jianchun; dong, xiaokai; yin, zhe; zhang, ke title: assessment the protection performance of different level personal respiratory protection masks against viral aerosol date: 2012-12-23 journal: aerobiologia (bologna) doi: 10.1007/s10453-012-9286-7 sha: doc_id: 257997 cord_uid: btj4ckkz new viral disease such as sars and h1n1 highlighted the vulnerability of healthcare workers to aerosol-transmitted viral infections. this paper was to assess the protection performance of different level personal respiratory protection equipments against viral aerosol. surgical masks, n95 masks and n99 masks were purchased from the market. the masks were sealed onto the manikin in the aerosol testing chamber. viral aerosol was generated and then sampled simultaneously before and after the tested mask using biosamplers. this allows a percentage efficiency value to be calculated against test phage sm702 aerosols which surrogates of viral pathogens aerosol. at the same time, the masks face fit factor was determined by tsi8020. the viral aerosol particles aerodynamic diameter was 0.744 μm, and gsd was 1.29. the protection performance of the material of all the tested masks against viral aerosol was all >95 %. all the five surgical masks face fit factor were <8. f model n95 mask and h model n99 mask face fit factor were all >160. g model n95 mask face fit factor was 8.2. the protection performances of n95 or n99 masks were many times higher than surgical mask when considering the face fit factor. surgical masks cannot offer sufficient protection against the inhalation of viral aerosol because they cannot provide a close face seal. severe acute respiratory syndrome (sars), h5n1 avian influenza and novel h1n1 influenza a are classified as infectious respiratory diseases. sars posed a mammoth challenge because of the impact of nosocomial transmission on healthcare manpower and facilities, and the resources needed for controlling and preventing further spread (tai 2006) . with concerns about a possible approaching influenza pandemic, the control of transmission via infectious air has become more important. public health services as well as clinicians and practitioners will be confronted with a new paradigm of infectious disease control. there were many types of masks available, and the different types offered very different levels of protection performance. surgical masks are primarily designed to protect the patient and surgical area from contamination and not the wearers from the infectious aerosol, and they are open on the sides, top and bottom. n95 or n99 masks cover the nose and mouth and are specifically designed to protect the wearer from exposure to airborne infectious diseases by sealing tightly to the face and filtering infectious particles from the air. studies showed that surgical mask and n95 mask have no statistically significant in risk of sars infection (seto et al. 2003; loeb et al. 2004 ). gamage pointed out the shortcomings of above studies (gamage et al. 2005) . while macintyre's study showed that n95 had the protection efficiency and surgical mask had no efficiency to control influenza transmission in healthcare workers (hcws) (liverman et al. 2009 ). some studies showed that even n95 or n99 mask had no adequate protection efficiency against viral aerosol in experimental environment (balazy et al. 2006; eninger et al. 2008; lee et al. 2008) . health care workers have long relied heavily on surgical masks to provide protection against influenza and other infections ). until now clinical effectiveness data of surgical mask and n95 mask are thus quite limited and conflicting. faced with the emergence of a virulent respiratory disease like sars, tuberculosis, avian or pig flu, etc. how to choose and use respiratory protection mask can be key decisions, among other things (lavoie et al. 2007) . given the likelihood that n95 or n99 mask will be in short supply during a pandemic and unavailable in many countries, understanding the relative effectiveness of surgical masks and n95 or n99 masks is important. in this study, the surgical masks, n95 and n99 masks were purchase from the market. the masks protection performance against viral aerosol and face fit factor was determined in order to evaluate the protection efficiency of different level protection mask. henan piaoan group co., ltd., china) and one model n99 mask (h: firmshield biotechnology, china) were purchased from the market. all of the masks were disposable personal protection equipments (ppe) and approved to manufacture by state food and drug administration. surgical masks were used in ordinarily work by hcws, and n95 or n99 masks were used the face fit technology to protect the wearer against the infectious aerosol. bacteriophage sm702 was isolated by ourselves. it is dsdna virus and about 100 nm size. sm702 had good aerosol stability in our previous study (yu et al. 2010 ). phage sm702 was preparation as before (yu et al. 2010) . a fresh preparation was made for each series of tests. there have total of eight series of tests. the test method was modificated from our previous study ) and balazy study (balazy et al. 2006) . it was shown diagrammatically in fig. 1 . the challenge viral aerosol was generated using a 6-jet collison nebulizer (bgi inc., waltham, ma, usa) at flow rate 10 l/min, which was supplied by a clean compressed air system. generated aerosol was diluted by clean compressed air in a testing aerosol chamber. the dryer was not used in order to mimic the actual conditions because most airborne 20-300 nm sized viruses were the part of droplet nuclei or attached to other particles, namely the carrying-virus particles or droplets (chen et al. 2009 ). the viral aerosol particle size distribution outside the tested mask in the test chamber was determined using tsi 3321 aerodynamic particle sizer (aps, tsi inc., mn, usa). the aps detects particles size distribution using a sophisticated time-of-flight technique that measures aerodynamic diameter in real time. the viral aerosol particles aerodynamic diameter was 0.744 lm, and geometric standard deviation (gsd) was 1.29. the tested masks were sealed by silicon sealant to the face of a manikin, which was placed at the height of 80 cm inside the chamber. a bubble-producing liquid was used to assure that there were no leaks between the tested masks and the manikin's surface. the sealant surface was covered by this liquid, and the compressed air flowing through the mask caused bubbles formation in case of a leak. the places at which the leakages were detected were additionally sealed and checked for leaks again. the test chamber was located inside a -20 pa negative lab. the viral aerosol protection efficiency experiments were carried out at constant flow rates 28.3 l/min using six-stage andersen samplers which were used to sample the air at two positions. one was at the control position to obtain a control sample, and the other was in the test position to obtain a test sample so as to determine the viral aerosol concentration before filtration and after the mask filtration, respectively. when testing the mask, the flow was 28.3 l/min (which simulates inhalation at light workload) and sample time was 1 min for control and 2 min for test. three sample masks of each model mask were selected mask to test the protection efficiency against viral aerosol. the collecting agars were cultured, and the plaque numbers counted. the filtration efficiency was determined by the aerosol concentration before and after the tested sample. filtered air can be drawn through the aerosol chamber by an air pump through a hepa filter. collecting samples of phage sm702 were covered by up layer of 0.5 ml host bacteria s. marcescens 8039 and 10 ml semi-solid culture (0.7 % agar) and incubated at 37°c for 12-16 h then counted the plaque on the plate. the number of pfu (plaque forming unit) of each plate was revised as reference (andersen 1958 ). by taking pre-and post-mask viral aerosol samples with sampling device, this method allows simultaneous measurement of viral aerosol concentration before and after filtration. the percentage efficiency of the test mask was calculated using the following formula, where a was the concentration of viral aerosol challenging the mask and b was the concentration of viral aerosol after filtration. phage sm 702 aerosol was determined in terms of pfu/m 3 . face fit factor was done by tsi8020 and n95 components as previous study ). the mask can be fit tested by inserting a test probe through the filter material. tsi model 8025-n95 probe kit includes disposable probes and insertion tools. in our test, fit factor pass level was set 150. eight testing actions included normal breathing, deep breathing, head side to side, head up and down, talk out aloud, grimace, bend and touch toes, normal breathing. face fit factor ranged 1-200, and when the fit factor more than 200, the result was 200?. overall fit factor is automatically calculated by fitplus software. the following equation is used to calculate the overall fit factor (ff): ffx=fit factor for test cycle, n=number of test cycles (exercises). each exercise includes an ambient sample, a mask sample and then another ambient sample. measures respirator fit by comparing the concentration of microscopic particles outside the respirator to the concentration of particles that have leaked into the respirator. face fit factor is defined as the particle concentration outside the mask divided by the particle concentration inside the mask. face fit factor of 150 fig. 1 rig for testing filtration efficiency of respiratory protection equipments against viral aerosol aerobiologia (2013) 29:365-372 367 means that the air inside the mask is 150 times as clean as the air outside the mask. two men and two women were selected to test the face fit factor. phage sm702 viral aerosol particles size distribution was showed in fig. 2 . the viral aerosol particles aerodynamic diameter was 0.744 lm, and geometric standard deviation (gsd) was 1.29. three new masks samples of each model masks were selected to test filtration efficiency against viral aerosol. the result of five models surgical masks filtration efficiency against viral aerosol showed in table 1 , and the results of n95 or n99 masks showed in table 2 . six-stage andersen sampler was used to collect the air after filtration of the mask, and the flow rate was 28.3 l/min. the sampling time was set 2 min because the prolonged nature of the tests may have caused excessive drying of agar and loss of viral viability, so the testing limit was 18 pfu/m 3 . if there were no phage sm702 plaques on the collected agar of the tested samples, the result was \18 pfu/m 3 . all of the tested masks filtration efficiency of phage f2 aerosol were [95 %. if do not consider the face fit factor, both the surgical mask and n95 or n99 mask had good protection efficiency against viral aerosol in our study. two female and two male researchers performed the face fit factor test. face fit factor of the tested surgical masks were showed in table 3 , and n95 or n99 masks were showed in table 4 . the overall face fit factor pass level was set 150. the highest overall protection factor of the tested surgical masks was 6.9, and the lowest was 2.5. f model n95 mask overall protection factor was 194.5, and e model n95 was 8.2. h model n99 mask overall fit factor was 180.3. the measurement provided by the equipment is an assessment of mask protection factor during a fit test only. mask fit at other times will vary. the protection factor value is not intended for use in calculating an individual's actual exposure to hazardous substances. two different models of n95 mask, one model of n99 mask and five different models of surgical masks were evaluated in this study. the concentration of the viral aerosol was measured outside and inside of each tested masks by the biosamplers. based on the results obtained from the biosamplers, the masks protection efficiency against viral aerosol was determined. the surgical masks and n95 or n99 mask used in this study were sealed to the face of the manikin, so their efficiency determined during viral aerosol protection experiments is defined as the efficiency of the filter material. the actual field-measured efficiency may be lower if there are some leakages between the wearer's face and the material of the surgical mask or n95 or n99 mask. so the face fit factors of the tested masks balazy et al.'s study showed that n95 masks penetration levels of the ms2 virions was exceed 5 % and 2 surgical masks were 20.5 and 84.5 %, respectively, at an inhalation flow rate of 85 l/min (balazy et al. 2006) . different particles size, testing flow rate and mask products may be lead the different results. though the efficiency of the filter material of tested masks against viral aerosol was all [95 %, the protection factors determined by tsi8020 and n95 components were different greatly. the protection factor of n95 mask or n99 mask except g model was nearly 30 times greater than the surgical mask, and no surgical mask protection factor was above 8. face fit testing reduces the risk of exposure to infectious agents by the airborne route (huff et al. 1994; hannum et al. 1996) . the fit factor obtained through fit testing may not adequately predict the true respiratory protection when the worker is performing actual work activities. as true workplace protection factors are often difficult to measure, simulated workplace protection factors are used as an alternative to estimate the respiratory protection level. in our study, simulated workplace protection factors were conducted using a tsi portacount plus model 8020. the assigned protection factor is 100 for n95 or n99 masks (aqsiq 2010); in our study, 150 was set as pass level. the laboratory-generated protection factor results are expected to be greater than the field protection factor results due to lower workload and narrower range of head movements performed in the test. lee et al. (2008) found that n95 masks had protection factors that were 8-12 times greater than those of surgical masks. oberg and brosseau study showed the majority of the nine types of surgical masks failed the qualitative fit tests and all failed the quantitative fit tests (oberg and brosseau 2008 ). the majority of particle penetration of n95 masks and n99 masks comes from facepiece leakage (liverman et al. 2009; grinshpun et al. 2009 ). there even have debate in clinical protection efficiency of surgical mask and n95 mask against aerosol infection. seto et al. found that not consistently wearing either a surgical mask or an n95 mask was associated with developing sars when compared with their consistent use (seto et al. 2003) . only mask usage was significant in the multivariate analysis; however, there was no difference in risk of infection whether hcws were using surgical masks or n95 mask. loeb et al. did a retrospective cohort study of 43 nurses in 2 critical care units with sars patients and find a trend toward increased protection from n95 masks compared with surgical masks, but this was not statistically significant (loeb et al. 2004 ). unfortunately, gamage et al. pointed out that the small sample size of the cohort and other confounding factors made interpretation of the results difficult. the role of fit testing was not addressed, and the potential for accidental autoinoculation when removing gear was not examined (gamage et al. 2005) . a cluster randomized clinical trial was conducted to compare the clinical efficacy of surgical masks versus n95 mask with and without fit testing, versus control in influenza transmission in 1,936 healthcare workers in china. n95 masks were found to have statistically significant efficacy, while surgical masks showed no efficacy (liverman et al. 2009 ). the efficiency of n95 or n99 mask depends on user compliance. it is feasible that the improved efficiency of an n95 respirator over a surgical mask may be easily lost if compliance is poor or inadequate training is provided. radonovich et al. study showed that no more than 30 % of workers tolerated respiratory protective devices consistently throughout an 8-h workday, citing difficulties with speaking and communication, discomfort and other physical problems (radonovich et al. 2009 ). few data are available on the clinical effectiveness of surgical masks and n95 masks in preventing the transmission of respiratory disease viruses. there is a pressing need for research in respiratory protection, particularly for randomized, controlled trials on the effectiveness of different protection level masks. faced with the emergence of a virulent disease like sars, recommended the use of n95 mask, that must be properly fit and used in conjunction with other necessary protective equipment (eye protection, gloves, coveralls, etc.) and infection control procedures. surgical masks do not offer sufficient protection against the inhalation of viral aerosol because they cannot provide a close face seal. in our study, the filter material of the surgical mask had good protection against viral aerosol, but they had lower face fit factor and cannot provide adequate protection efficiency against viral aerosol. if the surgical masks use the face seal technology and have good face fit factor, they can be used to protection against aerosol infection particularly where the availability of n95 respirators is limited. for the hcws of healthcare settings in general, the surgical mask is enough, and it will be excellent if the surgical masks have used the face seal technology. new sampler for the collection, sizing, and enumeration of viable particles do n95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks? viral kinetics and exhaled droplet size affect indoor transmission dynamics of influenza infection filter performance of n99 and n95 facepiece respirators against viruses and ultrafine particles influenza virus in human exhaled breath: an observational study protecting health care workers from sars and other respiratory pathogens: a review of the infection control literature general administration of quality supervision, inspection and quarantine (aqsiq) performance of an n95 filtering facepiece particulate respirator and a surgical mask during human breathing: two pathways for particle penetration the effect of respirator training on the ability of health care workers to pass a qualitative fit test personnel protection during aerosol ventilation studies using radioactive technetium (tc99 m) technical guide rg-501, guide on respiratory protection against bioaerosols recommendations on its selection and use respiratory performance offered by n95 respirators and surgical masks: human subject evaluation with nacl aerosol representing bacterial and viral particle size range respiratory protection for healthcare workers in the workplace against novel h1n1 influenza a: a letter report. iom (institute of medicine) sars among critical care nurses surgical mask filter and fit performance respirator tolerance in health care workers effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (sars) novel h1n1 influenza and respiratory protection for health care workers sars: how to manage future outbreaks? annals of the academy of medicine determining the filtration efficiency of half-face medical protection mask (n99) against viral aerosol effects of different sampling solutions on the survival of bacteriophages in bubbling aeration acknowledgments this work was supported by the national importance infectious disease program of china (no. 2012zx 10004402). key: cord-257519-mug5g92f authors: baluja, a.; arines, j.; vilanova, r.; bao-varela, c.; flores-arias, m. t. title: uv light dosage distribution over irregular respirator surfaces. methods and implications for safety date: 2020-04-11 journal: nan doi: 10.1101/2020.04.07.20057224 sha: doc_id: 257519 cord_uid: mug5g92f background and objectives: the sars-cov2 pandemic has lead to a global decrease in protection ware, especially facepiece filtering respirators (ffrs). ultraviolet-c wavelength is a promising way of descontamination, however adequate dosimetry is needed to ensure balance between over and underexposed areas and provide reliable results. our study demonstrates that uvgi light dosage varies significantly on different respirator angles, and propose a method to descontaminate several masks at once ensuring appropriate dosage in shaded zones. methods: an uvgi irradiator was built with internal dimensions of 69.5 x55 x 33 cm with three 15w uv lamps. inside, a grating of 58 x 41 x 15 cm was placed to hold the masks. two different respirator models were used to assess irradiance, four of model aura 9322 3m of dimensions 17 x 9 x 4cm, and two of model safe 231ffp3nr with dimensions 17 x 6 x 5 cm. a spectrometer stn-silvernova was employed to verify wavelength spectrum and surface irradiance. a simulation was performed to find the irradiance pattern inside the box and the six masks placed inside. these simulations were carried out using the software dialux evo 8.2. results: the data obtained reveal that the dosage received inside the manufactured uvgi-irradiator depends not only on the distance between the luminaires plane and the base of the respirators but also on the orientation and shape of the masks. this point becomes relevant in order to assure that all the respirators inside the chamber receive the correct dosage. conclusion: irradiance over ffr surfaces depend on several factors such as distance, angle of incidence of the light source. careful dosage measurement and simulation can ensure reliable dosage in the whole mask surface, balancing overexposure. closed box systems might provide a more reliable, reproducible uvgi dosage than open settings. the sars-cov2 pandemic has lead to a global, critical decrease in protection ware, especially facepiece filtering respirators (ffrs). due to this shortage, multiple recommendations have arisen, in particular related to the use of ultraviolet germicidal irradiation (uvgi, 254 nm) for decontamination [1] [2] [3] . as of 30/03/2020 cdc issued new guidelines to reuse masks [4] acknowledging that decontaminated n95 mask limited reuse may be necessary in dire shortage situations. uvgi acts primarily over surfaces. thus, surface shape, incidence angle and distance related to the light source are key factors for local irradiance. the resulting uv dose (fluence) is therefore the product of the irradiance by exposure time. given the high spread potential and severity of sars-cov2, local overdose may be sacrificed in order to minimise contamination risk by underexposure, as most ffrs can tolerate higher than germicidal doses. however, protocols for mask descontamination inside rooms with powerful uv-c sources might not ensure an even dosage distribution among masks placed at different angles from the lamp. the main objective of this study is to demonstrate that uvgi light dosage varies significantly on different respirator angles, and propose a method to descontaminate several masks at once ensuring appropriate dosage in shaded zones. 3 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint an uvgi box irradiator was built with internal dimensions of 69.5 cm length, 55 cm wide, 33 cm tall. inside, a grating of 58x41x15 cm was placed in order to hold the masks. three 15w lights hns 15w g13 (osram) were located at the upper limit in three of the four walls of the box. the plane containing the three luminaires is parallel to the bottom. the grating that will hold the respirators is placed over the bottom. the length between the luminaires plane and the grating was evaluated and measurements were taken to find the more homogeneous dosage inside the uvgi chamber. the whole internal surface of the chamber was coated with a matte aluminum insulating lining. aluminum is known to present a good reflection in the uv-c wavelength range [5, 6] . a spectrometer stn-silvernova, with a sensitivity range between 190nm and 1110 nm (2nm resolution) equipped with a stn-cr2-cosine corrector was used to verify the 254nm emission spectrum. the spectrometer was calibrated with the stn-irraduvn-cal to measure the dosage received inside the chamber and evaluate the several critical positions. 4 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint the irradiance distribution of the luminaire (see figure 1 ) was measured, showing its peak at the 254nm with a full width half maximum (fwhm) of 4.84 nm. a lamp heating time around 5 min was observed in order to obtain a stable emission. in order to evaluate the optimal orientation of the respirators inside the chamber, several dosage measurements were done. the first measurements were obtained with the grating located at a vertical distance of 10 cm from the luminaires plane and with a sigle respirator inside the chamber located near the wall without luminaires. the detector was placed just at the right of the respirator at the first measure (see figure 2a) . a dosage of 550 w/cm2 was obtained. the measure was repeated moving the respirator 5 cm towards the opposite wall that counts with a luminaire (see figure 2b ). in this case a dosage of 700 w/cm2 was measured. the same measurements were repeated with a distance between the grating and the luminaires planes of 16 cm. in this case values of 650 w/cm2 and 780 w/cm2 were obtained at positions a and b, respectively. that indicates that a 16cm distance assures higher dosages than at 10 cm distance, thus this height was selected for performing the following measurements. in addition, the detector was placed pointing upwards inside the masks, to measure the dosage received by the inner part of the respirator. with this setup a dosage of 60 w/cm2 was obtained. (see figure3a) to evaluate if there is difference in the dosage received by the respirators, when they are placed in different positions inside the chamber, as well as to evaluate the shadows in terms of dosage when several respirators are disinfected at the same time, the following measurements were performed. two different respirator 5 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint in the second configuration, the position of the higher respirators was changed by moving them close to lamp l2. in this configuration, shown in figure 3c, the dosage achieved at the position marked by letter f was 1050 w/cm2. to test if the dosage depends on the position of the respirators over the grid, they were rotated 90 degrees and the sensor probe was bent at a 30 degree with the horizontal in order to evaluate the dosage at the lateral of the respirators. this configuration is shown in figure 3d. in this case the result obtained at the point marked by a g was 878 w/cm2. note that the sensor was located slightly below the plane of the masks so, a higher dosage value is expected in upper positions. finally, the sensor was placed under the respirators pointing downwards in order to determine the light coming from reflections at the bottom of the chamber at two different position marked by an h and a i in figures 3 e and 3 f, respectively. the results at both positions were 422 w/cm2 and 410 w/cm2; respectively, indicating that the light distribution generated by reflections in the matte aluminum coating of the box is very homogeneous. the data obtained reveal that the dosage received inside the manufactured uvgi-irradiator depends not only on the distance between the luminaires plane and the base of the respirators but also, on the orientation and shape of the masks. this point becomes relevant in order to assure that all the respirators inside the chamber receive the correct dosage. although could be expected that the nearer the respirator is to the luminaires, the higher dose it receives, the experiment reflects this assumption is not true. for example in the presented work, 100 w/cm2 more irradiance was obtained when placing the base of the masks at 16cm than when they were placed them at 10cm from the plane that contains the lamps. by the analysis of the data, the absorption produced in a respirator can be determined, by measuring the dosage received just under one of them. the data confirms that around one order of magnitude of the dosage 6 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint figure 3 : photography of the inner part of the chamber, with the grating located at 16 cm from the luminaires plane a) detector just below the respirator, and 6 respirators placed in different configurations b) masks placed vertically with the shorter masks closer to the left lamp c) masks placed vertically with the taller masks closer to the left lamp d) masks placed horizontally, e) detector placed below one of the tall masks near the middle of the box; and f) detector placed below one of the short masks near the right side of the box, far from the lamp on the left side of the box. 7 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint is absorbed by the bulk of the respirator. that should be taken into account, in case that the geometry of the respirator doesn't allow to turn them for receiving a certain dose for sterilization. in this case, the exposure time should be calculated in order to warrant the dosage in the inner part of the ffrs. some simulations were also made in order to find the shadows and areas with less irradiance inside the box. these simulations were carried out using the software dialux evo 8.2. two masks models were simulated: model safe 231ffp3nr and the model aura 9322 3m. the first model was simulated with a truncated pyramid of dimensions (long, width, high) 17cm x 4cm x 9cm. the base of 4 cm corresponds to the case were the masks are slightly open. the second model was simulated with a truncated pyramid of dimensions 17cm x 9cm x 5cm. the masks were placed in two rows and three columns as they are planned to be in the disinfection box. additionally, two different orientations were simulated with respect to the long side of the box, parallel and perpendicular. blue colors correspond to a reference amount of light. green color represents a value equal to two times the reference value, yellow corresponds to three times, amber to four times, and red to 5 times. similarity was observed between the measured data and the simulations. in both cases, as long as we move away from l2, a reduction in the irradiance is calculated, getting the minimum exposure in the right side of the respirator mask on the right. both, measured data and simulations reflect that in region c of figure 4 we get half of the exposure obtained at d, and one third of that at e. additionally, comparing the two light distribution obtained for the two orientations of the respiratory masks, the shadows obtained with the masks parallel to the long side of the box, are less pronounced. hence, this orientation is suggested as the preferred one. figure 5 compares the pseudocolor maps of the light distribution inside the disinfection box using three and four lamps. note the difference between using three or four lamps, as four lamps provide a more uniform light distribution with less difference in the light amount. with four lamps we also diminish the shadows in the face of the mask of the right side. the resulting uv dose (fluence) is the product of the irradiance by exposure time, as follows: (1) ( / 2 ) = ( / 2 ) * ( ) therefore, in order to know the exposure time needed for sterilization of the respirators used with covid patients, the following relation is used: (2) = being t, the exposure time expressed in seconds, dosage expressed in j/cm2 and the irradiance in w/cm2. calculations were made for the time needed to receive a certain dosage in the less irradiated position. as an example, exposure times for different dosages are presented at table 1 . this was carried out to ensure that the cumulative dosage received by all and each respirator is enough to work in safety conditions when these are reused after being in contact with covid patients. 8 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint figure 4 : left) representation of the experimental data obtained in the disinfection box; right) simulated light distribution maps in pseudocolor maps inside the uvgi irradiator. the luminaires are marked in white and named l1, l2 and l3. blue colors correspond to a reference amount of light. green color represents a value equal to two times the reference value, yellow corresponds to three times, amber to four times, and red to 5 times. 9 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint 10 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint the irradiator, equipped with four wheels, was placed in the covid icu of a tertiary-care hospital (16 beds) in a separate room more than 2m away from any covid patient. the placement was inside the covid area to avoid contamination elsewhere. the box was equipped with an on-off switch and a security mechanism that turned the lamps on when closed and off upon lid opening. after building another irradiator unit, the capacity doubled to 93*2=186 units/day. precise instructions were given for their use, indicating the target time of descontamination (1.5 hours). users were instructed to write down their name in the ffrs and mark them each time they underwent descontamination. the masks waiting to be descontaminated were placed inside individual, named envelopes. the ffrs were then placed one by one as described in fig 3b avoiding contact with the surface in contact with the wearer. after irradiation, masks were placed again in clean, individual envelopes. to ensure grid decontamination after each cycle, an additional time of 5 min was added with the cabinet closed and no masks inside. an additional set of instructions were given in order to promote a rational use of the irradiator, as neither niosh nor 3m nor the spanish health ministry recommend ffr reuse except in extreme shortages when no new masks are available. based on recommendations given by those sources and our own user experience we discourage using the irradiator when any of the following conditions are met: this study demonstrates the extent of the dependence between dosimetry and mask location, relative to the light cone and other masks or obstacles that might be present. with regard to room uvc decontamination of ffrs, dosage needs to be measured at the most extreme incidence angles. on the other side, small uvgi cabinets have less angle variability but they often need flipping the object to be decontaminated, and some respirator brands have conic-oval volumes that can't stand stable in both flipped positions. a big-furnace method is proposed which allows for multiple mask decontamination without the need to leave covidareas and doesn't require to flip the respirator for the desired dosage, thus ensuring minimal respirator manipulation. ultraviolet light is gaining acceptance among the healthcare community as they're a cost-effective alternative to heat or chemical descontamination. at moderate uvgi doses, mask performance still surpasses that of surgical masks, thus being a viable alternative when no new ffrs are available. viscusi et al administered 3.24 j/cm2 and examined fit, odor, comfort and deterioration in several mask brands, not finding significant differences using uvgi [2] . niosh collaborators, lindsley et al [3] found changes in particle penetration, but only small changes in resistance after very high uvgi doses (up to 950 j/cm2). regarding disinfection, niosh guidelines [3] advise to discard masks after aerosol-generating procedures. however, previous studies have shown that uv disinfection is suitable to remove viral load although more studies are needed to acscertain viral removal from the inner ffr layers. uvgi dose for coronavirus in surfaces has been shown to be lower than other types as they're single-stranded rna virus. for example, duan et al [7] found that 0.32 j/cm2 can inactivate sars-cov in culture plates, whereas for h1n1 influenza, decontamination with 1.2, 1.8 or 1.98 joules/cm2 achieved an average 4-log reduction of viable h1n1 influenza virus [1, 8, 9] . this is a study where changes in irradiance are studied in a closed, controlled environment. different mask brands have different shapes, modifying local irradiance. to compensate for this, overdosing of more exposed areas might be necessary, causing them to accumulate more deterioration, shortening the respirator's life. further studies might be needed to ascertain dose homogeneity when the uvgi lamps are placed in a bigger compartment, such as a room. in addition, adding light sources on both sides of the rack might provide more reliable illumination avoiding over and underexposure. this uvgi box currently doesn't support the descontamination of more than six masks at once. bigger designs can provide mask reuse at a bigger scale in times of severe shortages. currently, virological assessment is being designed in an appropirate setting for this irradiator. thus, target dosage regimes are based on previously published experiments elsewhere. 12 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. irradiance over ffr surfaces depend on several factors such as distance, angle of incidence of the light source. careful dosage measurement and simulation can ensure reliable dosage in the whole mask surface, balancing overexposure. closed box systems might provide a more reliable, reproducible uvgi dosage than open settings. â�¢ custom uvgi devices must feature mechanisms to protect from harmful uvgi irradiation. â�¢ dosimetry from strategic locations of an uvgi facility allows for correct time-irradiance calculations in respirators at different positions. â�¢ irradiance measurements can be performed by experts in visible light pollution or photonics, given access to a uv-c light spectrometer. â�¢ alternatively, manual dosimeter probes can be used at such locations. â�¢ careful respirator placement must be ensured to minimise error in the administered uv dose. â�¢ clear instructions on device operation and respirator reuse must be issued, updated and published in the work environment. all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint table 1 . exposure time with the respirators in the configuration of fig 3d. 14 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 11, 2020. . https://doi.org/10.1101/2020.04.07.20057224 doi: medrxiv preprint ffr which completed 3 uv-c cycles used during aerosol-generating procedures (such as oral hygiene or airway procedures) wet mask (sweat, etc) any of the 3 known complications uv-c disinfection in ffrs: 6a-loss of fit or adjustment. 6b-moderate or intense odor that doesn't disappear after 10 minutes of aireation. 6c-elastic bands deteriotarion also, discard when: 7a-doubts about adequate decontamination in a suitable time. 7b-visible damage to the mask or increased difficulty in breathing through the filter if it must be removed prematurely from the irradiator, treat it as a non-decontaminated ffr a pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with h1n1 aerosols and droplets impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease effects of ultraviolet germicidal irradiation (uvgi) on n95 respirator filtration performance and structural integrity centers for disease control and prevention far-uvc light: a new tool to control the spread of airborne-mediated microbial diseases handbook of optics, third edition volume iv: optical properties of materials, nonlinear optics, quantum optics stability of sars coronavirus in human specimens and environment and its sensitivity to heating and uv irradiation ultraviolet germicidal irradiation of influenza-contaminated n95 filtering facepiece respirators effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators. the annals of occupational hygiene we would like to acknowledge the help and support received by the physics and optics faculties, ricardo rodrã­guez and julio cortiã±as from the department of anaesthesiology. we would also like to thank professor salvador barã¡ viã±as of the photonics4life group at usc for his advice in carrying out measurements and checking calculations. key: cord-171219-jkoegawm authors: sheets, donal; shaw, jamie; baldwin, michael; daggett, david; elali, ibrahim; curry, erin; sochnikov, ilya; hancock, jason n. title: an apparatus for nondestructive and rapid comparison of mask approaches in defense against infected respiratory aerosols date: 2020-06-03 journal: nan doi: nan sha: doc_id: 171219 cord_uid: jkoegawm at the front lines of the world's response to the covid-19 pandemic are hero-clinicians facing a lack of critical supplies including protective medical grade breathing masks and filtering materials. at the same time, the general public is now being advised to wear masks to help stop the spread. as a result, in the absence of centrally coordinated production and distribution efforts, supply chains for masks, respirators, and materials for advanced filtration technology are immensely burdened. here we describe experimental efforts to nondestructively quantify three vital characteristics of mask approaches: breathability, material filtration effectiveness, and sensitivity to fit. we focus on protection against water aerosols $>$0.3$mu$m using off-the-shelf particulate, flow, and pressure sensors, permitting rapid comparative evaluation of these three properties. we present and discuss both the pressure drop and the particle transmission as a function of flow to permit comparison of relative protection for a set of proposed filter and mask designs. the design considerations of the testing apparatus can be reproduced by university laboratories and medical facilities and used for rapid local quality control of respirator masks which are of uncertified origin, monitoring the long-term effects of various disinfection schemes, and evaluating improvised products not designed or marketed for filtration. sars-cov-2 is an infectious virus which is believed to be transmitted via respiratory aerosols [1] [2] [3] . the threat of aerosol spreading is of such concern that the hvac systems of hospitals are being re-engineered from their design intent so that infected air is released from the building immediately after potential infection in covid wards 4 . near the peak of an infection curve 5 , the rate of infected patients can stretch the resources of hospitals and federal regulations have been adjusted to meet the realities of scarcity in the absence of enhanced production of personal protective equipment (ppe) 6 . this situation has set the medical profession on edge, and hospital systems in the northeast have so far responded with an all-hands-on-deck approach to the myriad challenges posed by covid-19 [7] [8] [9] . independent researchers at local universities have also heard the call and moved rapidly to help their regional hospitals with the local problem of insufficient ppe such as face masks, face shields, and ventilators. of these three vital hospital resources, face masks capable of blocking small virus-containing droplets require the most developed textile technology 10 . disrupted supply chains have limited access to advanced textiles such as corona-charged melt-blown polypropylene, a material capable of supporting electrostatic filtration 11 , which provides a high-efficiency, breathable, inexpensive and accessible mask certified as n95. with supply chains slowly recovering, the quality and safety of masks and a) electronic mail: donal.sheets@uconn.edu b) electronic mail: jason.hancock@uconn.edu respirators from new suppliers is critical to address. dwindling supplies of ppe in clinics and hospitals 12, 13 combined with the concomitant emergence of appeals for the general population to begin donning masks 14 has strained the supply chain and led to local efforts to produce new technologies, as well as many proposed do-it-yourself mask approaches, in an effort to meet these needs 9, 15, 16 . in this environment, many claims of efficacy are made, while the data supporting such claims are often incomplete or lacking. even in the case of certified respirators and surgical masks, historical variation in the testing regimes for particle filtering and infection control has been a complicating issue 17 . in addition, issues such as the presumed higher efficacy of n95 respirators over surgical masks in ultimately preventing infection remain controversial, with critical issues of fit and compliance likely confounding the utility of materials with ostensibly superior filtering properties [18] [19] [20] [21] . in this time of crisis, accessible methodologies are needed which can rapidly compare novel materials and mask designs alongside currently certified materials. this document describes an experimental apparatus, devised and developed at the university of connecticut and in collaboration with clinicians from the university of connecticut health center during a short response period in march and april 2020. this apparatus is capable of making comparisons of essentially any proposed mask design with respect to filtration of water aerosol particles in the <1.0µm size range. our approach relies on a simulation of the clinical situation 22 , illustrated in figure 1a . aerosol containing virus particles is exhaled by an infected patient (ip) into a clinical environment (ce), where it is potentially inhaled by a medical professional (mp). each of these abbreviated terms corresponds to a separate chamber in our apparatus ( figure 1b ). controlled flow of aerosolized air propagates from the ip chamber to the ce chamber and enters the mp chamber through either (a) a mask-donning dummy head or (b) a clamped-material tester depending on the state of two ball valves (figure 2c ). the chambers are connected sequentially ip-ce-mp with gas flow fittings and feature calibrated sensors capable of measuring flow rate, pressure drops, and aerosol particle distribution in different size ranges. the two modalities of the apparatus permit assessment of (a) a mask on a dummy head with realistic respiratory geometry or (b) material-only properties regarding breathability and filtration efficiency over selected sections of a mask. each of these modalities provide vital information to assess the practicality and effectiveness of protection against infectious diseases like those born by sars-cov-2. the apparatus ( figure 2 ) consists of a fiberglass glove box (labconco 50350, kansas city, missouri, usa) with a sealable load-lock chamber mounted on a large swinging door which can be opened/closed and sealed quickly using toggle clamps. the large chamber of the glove box represents the ce where clinicians are exposed to potentially infected aerosol droplets exhaled by the infected patient (ip). a steady flow of aerosolized air flows from the ip through the ce and enters the pumped mp load-lock chamber through either (a) a fit tester dummy head (laerdal airway management trainer, stavanger, norway) or (b) a clamp-style materials tester based on kwik-flange (kf) vacuum fittings. identical sets of particle meters in the ce and mp chambers monitor particulate sizes, humidity, temperature, and pressure on each side of the mask or material. operation of two 3 4 in pvc ball valves enables either the (a) mask or (b) material tester, permitting various tests with the same chambers and sets of particle detectors. a gas pump, needle valve, and flow meter control and measure the flow through the mask or material and into the mp. steady-state air flows into the ce from a controlled aerosolized air source, through the ce and enters the load-lock chamber representing the mp. aerosol particle distributions are measured before and after the mask or the filter material and the experiment is repeated with an open system and a control high-performance mask (3m-1860 n95 standard) for comparison. pressure drop is measured simultaneously using a differential pressure meter to assess breathability of masks and materials. below we detail different components of the system following the air flow, from ip to ce to mp chambers. sars-covid-2 is a virus around 60-140nm in diameter 23 and is believed to be long-lived in airborne aerosol form, particularly in droplet nuclei, the dried-out residuals of droplets which potentially contain infectious pathogens [24] [25] [26] . the halflife of sars-cov-2 in water aerosol is determined to be approximately 1 hour 27 . while respiratory fluid is known to contain water as a dominant component, significant other constituents besides virions are common. a respiratory droplet 0.1nl in volume has a radius 2.8µm and a mass of 100ng and can contain as much as 1ng salt and 1ng protein. we simulate covid-infected respiratory aerosols with a chamber where an ultrasonic nebulizer element submersed in water produces faraday surface waves and cavitation 28 , emitting a plume of fine water aerosol. much of the water evaporates and the fine particulate matter is determined by the residual ions. the use of water as a particulate has advantages for testing mask and material filtration specific to covid-19. water does not contaminate the system, compared to choices like saline solution aerosols, allowing for rapid screening of alternative ppe candidates, with direct comparison to desired outcome ppe, such as n95 respirators, within hours. the aerosol-generating subsystem used in the experiments presented here is outlined in figure 2a , left side. the nebulizer consists of an immersed piezoelectric element which is figure) or a material clamp tester and into the mp chamber. optical and condensing particle meters measure humidity, pressure, temperature, and count particulate matter 0.02 to 10µm in diameter. (b,c) photographs of the apparatus testing two n95 reference masks. active when driven with a 60hz 24v amplitude sine-wave. in order to achieve fine control of aerosol content of the air flowing through the system independently of the flow dynamics such as pressure drop and air currents, we pulse the nebulizer around 0.2hz and variable duty cycle. this subsystem produces a plume of fine mist into the flow stream of the air once every five seconds, and the duration of the plume is controlled by varying the duty cycle of the input square wave. we find that after the mixing stage, there is no observable time structure in the aerosol content and the distribution is unaffected by the duty cycle >1%. the measured relative humidity level in our main chamber is determined by ambient conditions and rarely exceeds 40% relative humidity. in this way, fine control of aerosol content of the air flowing through the system is realized independently of the flow dynamics such as pressure drop and air currents. to achieve controlled 24v 60hz pulse duration, we use an arbitrary waveform generator (awg; instek 2000 series, taiwan) which is amplified by a waveform amplifier (accel ts250, usa) to increase the current supplied to drive the element. if the nebulizer is on, we find that 45 seconds of operation completely saturates the detectors in the ce (>6.5×10 4 particles/sec >0.3µm). we gate the awg with a square wave gate pulse with variable duty cycle from a function generator (instek 2000 series, taiwan). alternatively, variable duty cycle of ac power with low-cost electronics could be achieved using a short period repeat cycle timer or a solid-state relay operated via a low-cost function generator. aerosol was sampled in the ce chamber using an optical particle detector (fluke 985 clean room particle detector, usa) and found to have a particle distribution mostly below 1µm, consistent with prior reports on a similar device 28 after significant evaporation. aerosol in this range is both challenging to filter using woven or common fabric materials but also makes up the vast majority of exhaled particulates 29 so is suitable for our apparatus. once the aerosolized air is pushed into the ce glovebox chamber, two dc motor fans, arranged to set up a vertical circulating flow pattern on the left end of the glovebox chamber, rapidly mix the aerosol and prevent settling. during this mixing process, large droplets evaporate and approach an equilibrium size distribution. applying the standard theory for settling time and terminal speed under stokes-law drag force developed for spherical aerosol droplets in air, we estimate the settling velocities of the 0.3 to 1µm water aerosol observed in our chamber to be in the range 1 to 10 cm/h, which implies that the aerosol in the chamber would stay well mixed over a few hours, more than sufficient to reach the mask and materials testers in the ce chamber. solutes such as nacl or kcl can be added to the water in the ip chamber and control the particulate size distribution as well as concentration. the mixed aerosol crossed through a baffle made from two layers of steel mesh with a 3.5mm grid pattern. using a hot wire anemometer, the measured air speed in the mixing chamber is of order 100cm/sec but less than 1cm/sec on the downstream side of the baffles. for a circular flow pattern of the mixing chamber has approximately 1m circumference, we estimate the chamber churns the air 5 times per aerosol pulse delivered 5 times/sec, consistent with the lack of detectable time structure has been observed in the ce chamber. aerosolized air was sampled on the right side of the ce chamber using optical particle detectors before transiting the mask or material into the mp chamber where a matching set of particle meters measured the aerosol distribution for comparison. three different types of meters are employed to span different size distribution ranges. fast readout particle detectors developed by purpleair (utah, usa) are based upon the plantower 5001 (beijing plantower, china) optical meters. in collaboration with pur-pleair, we have gratefully acquired test software permitting complete readout and logging of the two detectors per unit (two units/chamber) at approximately one second intervals. these meters have been studied under various conditions and correlate reasonably well with higher-performing and more costly particle meters 30 . they do not work as well in high humidity environments (>50%), are known to have lowered efficiency ( %50) in the finest particle channel (0.3-1.0µm) and are designed to perform well at high particle concentration levels. these meters are used during the experiment to make decisions during data acquisition as well as in analysis. nist-traceable cleanroom fluke 985 integrating and logging optical particle detectors are placed in each chamber during a typical run. these detectors are best suited for lower particle concentrations. the devices are programmed to collect 15 seconds with 2 minute wait times between. a single p-trak 8525 ultrafine condensing particle counter is used to detect integrated particle count in the 0.02-1.0µm range. this costly device consumes reagent grade isopropanol and is placed outside the chamber and connected to a small ball valve manifold with equal-length tubing to the ce and mp chambers. a single condensing particle counter was also used and a small ball valve manifold permitted fast switching between ce and mp chambers. a dummy head was removed from a laerdal airway management trainer, designed to give an accurate representation of human airflow pathways. the lungs were removed and the right main bronchus was closed with a rubber stopper and hose clamp. the left main bronchus was also hose-clamped onto a 1 2 in pvc barb fitting to to 3 4 in npt pipe thread, a short segment of vinyl tubing, and another barb into a pvc ball valve which is open when the mask tester is in use. the valve feeds through an acrylic door to the load-lock chamber using pvc pipe fittings and seals with an o-ring. optical breadboard sections mounted inside the door and in the bottom of the ce chamber provide secure mounting options for the particle sensors as well as dummy head and materials tester. to rapidly identify whether the fit or material are the weak link in any proposed mask design, we have enabled an option to disable the dummy head and open the ce-mp chamber connections though a dedicated materials tester. this jig is made active by opening a pvc ball valve connecting the mp chamber through pvc hard line or thick-wall 3 4 " rubber tubing terminating in a kf25 vacuum fitting pointing upwards and held fixed in the center of a 6"x6" polycarbonate plate mounted to the glovebox door. four 1 4 "-20 threaded rods in each corner of the polycarbonate plate form a materials clamp with a matching plate above and a second kf25 fitting. in order to access lower face velocities, we can introduce one of two conical adapters (kf25 to kf40 or kf25 to kf50) and matching vacuum fittings (kf40 or kf50, respectively) to distribute the flow over a larger area. figure 3a summarizes the parameters achievable with each of these fittings and figure 4a shows the transmission and pressure drops over these choices of fitting. this configurability permits access to face velocities up to 170cm/sec at a flow 25l/min with a 17.8mm hole on the kf25 fitting and down to the lower value of 2.9cm/sec at 5l/min flow with the 47mm hole in the kf50 fitting. our system could be operated at higher flows with suitable replacement of mass flow meter with a high flow mass flow meter or controller. both jigs were mounted inside the glovebox door as shown in figure 2c in order to permit short tubes in geometries which do not move when the door is opened. to facilitate this mounting, a small strip of optical breadboard was bolted to the inside of the glovebox door to present suitable and versatile mounting options. the material tester can be accessed using the box gloves enabling rapid swapping of the material without the need to wait for the chambers to equilibrate. the ability to swap out masks consecutively without altering environmental conditions is helpful for direct comparison of material approaches. experiments at various conditions indicate that pure water aerosol <1µm in diameter evaporates quickly, reaching its equilibrium size in less than one second 23, 29 . figure 3b ,c show the normalized size distribution of aerosol measured in the mp and ce chambers, showing that for tap water aerosol source, >90% of the observed particles are in the finest size bin 0.3-0.5µm and there is only a weak redistribution of sizes on transit from the ce to mp. figure 3d shows the difference of these plots, (mp minus ce) and reveals a small but detectable redistribution of the aerosol before and after the mask or material testers. the shape of the distribution changes no more than 3.3% between bins and does not significantly alter our comparative filtration measurements of masks and materials. note that the difference depends only slightly upon flow, with greater change occurring for lower flow as expected from evaporation. we estimate for the slowest flow rates used here (5l/min), aerosol is drawn from one to another in less than 3 seconds. in addition to changes in the shape of the distribution, there is also a flow-dependent transmission of the total number of aerosol particles >0.3µm through an open pipe. this arises from a well-known effect of aerosol collisions in the connecting pipe 31 -the longer the aerosol spends in the pipe, the more chance for a collision with a pipe wall and removal from the flow stream. as expected, we observe the lowest transmission of an empty pipe for the lower flows. to isolate the transmission of the mask or material, it is therefore necessary to address the loss of particles in the system when there is no mask present. for each measurement, the number of particles n are measured for the mp and ce chamsystem. the gas pump is located in a separate pump room, connected by 1 4 in tubing to a constrictive needle valve which permits fine control of the flow through the system. a thermal mass flow meter and a protective inlet filter recommended by the manufacturer is installed upstream and sensitively reads the mass flow with precision of 0.001l/min. feedback mass flow control could be introduced easily although we find the drift in flow is quite small. a. breathing, pressure drop, flow, face velocity: crucial for high performance masks is that low effort is required to inhale or exhale through a mask or mask material. this effort is typically quantified using the pressure drop at a given flow rate. the flow requirements on breathing are given by the situation, which for humans at rest is around 5-6 l/min on average assuming a tidal volume of 0.5l cycled 10-12 times per minute. time-resolved measurements of human respiration give flow rates in the range 10 l/min peak exhalation, with larger inhalation flow rates of order 25l/min. exertional breathing in healthy humans can reach peak inhalation flow exceeding 600l/min. the national institute for occupational safety and health (niosh) performs tests of mask and mask materials for n95 certification at 85l/min, where >95% of a defined distribution of nacl particles >0.3µm are blocked 10 . for any mask the flow q is distributed over the active filter material area a with a mask-averaged speed called the face velocity v = q/a. some standards for mask testing like niosh, specify flow, while others such as fda specify face velocity 17 . for the niosh test over a typical half face respi-rator such as the 3m-1860 of area 150cm 2 , the mask-averaged face velocity is around 9.3cm/sec while the same exercise for a surgical mask of area 2 results in a face velocity of 14.2cm/sec 17 . processes behind filtration include inertial impaction and diffusion in addition to electrostatic effects in the case of n95 10, 17 and this speed of impact determines the filtration efficiency. in what follows we will express the flow rate as well as face velocity, the latter of which permits comparison of filter measurements which used different areas. we emphasize that use of variable size vacuum fittings permits wide changing of the face velocity for a given flow range as shown in figure 3a . breathing through a mask is always more effort than breathing without one. the resistance to flow of the mask is determined by the filter material and the fit of the mask and can be quantified by the pressure drop at a given flow. in our experiments, the pressure difference between the mp and ce chambers is the pressure drop over either the mask or material being tested. we measure the pressure drop using a differential pressure meter (tsi 9565, minnesota, usa) connected to each chamber by tubing of equal length. figure 4a shows the pressure drop versus flow for the dummy head and each of the kf fittings attached to the materials clamp. these constrictions produce a measurable pressure drop much smaller than that of typical masks and materials. figure 4b shows the pressure drop over a set of materials with the kf40 vacuum fitting in the materials clamp. we note in particular the spread of pressure drops among masks labelled n95 and kn95. large pressure drops across filter material can significantly reduce the protection of a given mask, since the required air flow is distributed over both the mask and leaks. at a given flow, as the pressure drop across the mask increases, the draw of contaminants through leaks and facial fit gaps increases. we return to this point below in section iii d. c. filtration efficiency of filter material: figure 5a shows the transmission of all particles >0.3µm versus flow rate for certified n95s and many other materials using the kf40 materials tester attachment. the woven bandana provides very little protection from aerosol in the size range of our experiments, around 90% of particulates counted were in the 0.3-0.5µm range. it does however have an appreciable pressure drop, around 60% of an n95. a surgical mask has far superior 50% filtration efficiency compared to a bandana but is similarly breathable with similar pressure drop at the same flow rate. sterilization wrap has been proposed as a highly efficient filter candidate for improvised ppe approaches 32 and sterile and readily available in many clinical settings. compared to a surgical mask, the material has higher filtration efficiency , but it is less breathable. while a higher filtration aid protection, a higher pressure drop means that to sustain a given flow, the pressure across leakages and draw across soft points in the facial seal will support more flow which is detrimental to protection. another class of ppe filter materials are hepa-type vacuum bags and electrostatic furnace filters. these have standardized filtration rating systems of merv and mpr and examples are shown to achieve very good filtration and excellent low pressure drop. multiple layers of materials in this class could give excellent filtration in an abundant material source alternative to melt-blown polypropylene, the finest filtration component of the electrostatic n95 10 . the logarithmic scale in figure 5b brings out the lowtransmission region of interest for comparison of n95s for quality control and inspection of deterioration effects from disinfection schemes on post-cleaning filtration efficiency. all n95, most kn95s, and a high-efficiency based upon pftecoated pet show >95% filtration efficiency. this last material excels at filtration but is far too difficult to breath through. note that one uncertified mask labelled kn95 #3 performs poorly with only 60% filtration efficiency. while this mask has filtration performance slightly better than a surgical mask, the pressure drop is greater which means more flow is expected through the small leaks around the mask and may not in fact be safer in practice. this observation highlights the importance of local testing of mask and materials of uncertified origin as well as the need to assess both filtration and pressure drop properties of materials. sections iii b and iii c describe materials tests of pressure drop and filtration efficiency for materials with issues of facial fit completely isolated. inclusion of a second test channel through the dummy head permits an assessment of mask fit and its potentially deleterious contribution to protection. to expose this sensitivity, figure 6 shows the transmission of aerosol through the dummy head with a mask labelled kn95 fitted as received and with the metal nose piece pinched. the use of a glove box is a necessary feature for making small insitu adjustments to study the facial fit sensitivity. the drastic improvement from >50% transmission to <20% transmission highlights the benefits of fitment. at the same time, the degree of protection is still much less than the material alone, which transmits less than 1%. this demonstrates the apparatus ability to rapidly compare developing mask approaches but is limited in addressing dynamic factors such as head and jaw movement while talking as well as variation of head forms. we have demonstrated the construction and evaluation of a fast-turnaround apparatus capable of evaluating three important characteristics of aerosol-filtering masks: breathability quantified through pressure drop, filtration quantified through particulate transmission, and facial fit as determined from direct measurements on an anthropic head form. we have demonstrated the sensitivity of the measurements and considered sources of error in the measurement. we present comparison of high-technology electrostatic filters, surgical masks, instrument wrap fabric, and common textiles against complete lack of protection. the glovebox-based design concept has many advantages such as rapid screening of many masks without disrupting aerosol generation and flow. the design can be implemented with resources common to many universities and hospitals and can be implemented with low-cost sensors and electronics to screen masks that may vary substantially from dangerously poor to very high performance depending on the quality of the materials used. results of the anemometer face velocity measurement (points) along with the volumetric flow divided by kf weld stub inner area (lines). aerodynamic analysis of sars-cov-2 in two wuhan hospitals modes of transmission of virus causing covid-19: implications for ipc precaution recommendations academies of sciences and medicine, rapid expert consultation on the possibility of bioaerosol spread of sars-cov-2 for the covid-19 pandemic interim infection prevention and control recommendations for patients with suspected or confirmed coronavirus disease 2019 (covid-19) in healthcare settings nih director: 'we're on an exponential curve change in u.s. law will make millions more masks available to doctors and nurses, white house says a scalable method of applying heat and humidity for decontamination of n95 respirators during the covid-19 crisis an accessible method for screening aerosol filtration identifies poor-performing commercial masks and respirators aerosol filtration efficiency of common fabrics used in respiratory cloth masks information and faqs -charged filtration material performance after various sterilization techniques n95 mask shortage comes down to this key material: "the supply chain has gotten nuts why we're running out of masks osha enforcement guidance for respiratory protection and the n95 shortage due to the coronavirus disease 2019 (covid-19) pandemic state of connecticut, executive order no. 7bb.: protection of public health and safety during covid-10 pandemic and response -use of facemasks or cloth face coverings use of cloth face coverings to help slow the spread of covid-19 using blue shop towels in homemade face masks can filter particles 2x to 3x better than cotton, 3 clothing designers discover after testing dozens of fabrics a comparison of facemask and respirator filtration test methods physical interventions to interrupt or reduce the spread of respiratory viruses. part 1 -face masks, eye protection and person distancing: systematic review and meta-analysis effectiveness of n95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis surgical mask vs n95 respirator for preventing influenza among health care workers: a randomized trial respiratory virus shedding in exhaled breath and efficacy of face masks detection of infectious influenza virus in cough aerosols generated in a simulated patient examination room features, evaluation and treatment coronavirus airborne contagion and air hygiene: an ecological study of droplet infections how far droplets can move in indoor environments-revisiting the wells evaporation-falling curve natural ventilation for infection control in health-care settings aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 size distributions of droplets produced by ultrasonic nebulizers evaporation of ventilated water droplet: connection between heat and mass transfer field and laboratory evaluations of the low-cost plantower particulate matter sensor treatment of losses of ultrafine aerosol particles in long sampling tubes during ambient measurements uf doctor invents new type of mask to help offset coronavirus shortage we are especially grateful to adrian dybwad and purpleair for support in designing the software acquisition system. we would like to also like to thank joseph luciani, matthew phelps, amani jayakody, asanka amarasinghe, kaitlin lyszak for assistance and for supporting the work. this work was supported in part by national science foundation grant no. nsf-dmr-1905862. the data that support the findings of this study are available from the corresponding author upon reasonable request. appendix a: materials tester detail figure 7 details the materials tester mechanism. a flowthrough clamp is based upon kwik-flange vacuum fittings to create a tight and reproduceable clamp on thin pieces of material without invasive handling or destruction of a mask or material being tested. the clamp can be operated with the gloves of the glovebox, permitting direct comparison of materials with each other or with an empty holder under the same environmental conditions. in order to ensure the mating flanges clamp parallel to one another and form a tight uniform seal on the material, the kf flanges are compressed between two polycarbonate plates using 1 4 -20 threaded rod as shown. large knobs on the clamping nuts are convenient for changing masks while using the gloves. an advantage of the kf approach is the possibility to change the filter or mask area being probed which leads to a change in the tested face velocity range as illustrated in figure 3a of the main text. details of the clamp mechanism options for the three sizes available for the materials tester are shown in figure 8 .appendix b: direct face velocity measurements figure 9 shows results of an experiment using a hot wire anemometer to directly measure the face velocity across the open weld stub where air enters the materials tester. the lines through the points are the volumetric flow rate divided by measured area. this plot shows that our face velocities are as expected and that there are no significant leaks in the mp chamber. key: cord-267699-h7ftu3ax authors: macintyre, c. raina; chughtai, abrar ahmad title: a rapid systematic review of the efficacy of face masks and respirators against coronaviruses and other respiratory transmissible viruses for the community, healthcare workers and sick patients date: 2020-04-30 journal: int j nurs stud doi: 10.1016/j.ijnurstu.2020.103629 sha: doc_id: 267699 cord_uid: h7ftu3ax background: the pandemic of covid-19 is growing, and a shortage of masks and respirators has been reported globally. policies of health organizations for healthcare workers are inconsistent, with a change in policy in the us for universal face mask use. the aim of this study was to review the evidence around the efficacy of masks and respirators for healthcare workers, sick patients and the general public. methods: a systematic review of randomized controlled clinical trials on use of respiratory protection by healthcare workers, sick patients and community members was conducted. articles were searched on medline and embase using key search terms. results: a total of 19 randomised controlled trials were included in this study – 8 in community settings, 6 in healthcare settings and 5 as source control. most of these randomised controlled trials used different interventions and outcome measures. in the community, masks appeared to be more effective than hand hygiene alone, and both together are more protective. randomised controlled trials in health care workers showed that respirators, if worn continually during a shift, were effective but not if worn intermittently. medical masks were not effective, and cloth masks even less effective. when used by sick patients randomised controlled trials suggested protection of well contacts. conclusion: the study suggests that community mask use by well people could be beneficial, particularly for covid-19, where transmission may be pre-symptomatic. the studies of masks as source control also suggest a benefit, and may be important during the covid-19 pandemic in universal community face mask use as well as in health care settings. trials in healthcare workers support the use of respirators continuously during a shift. this may prevent health worker infections and deaths from covid-19, as aerosolisation in the hospital setting has been documented. the pandemic of covid-19 is growing, and a shortage of masks and respirators has been reported globally. policies of health organizations for healthcare workers are inconsistent, with a change in policy in the us for universal face mask use. the aim of this study was to review the evidence around the efficacy of masks and respirators for healthcare workers, sick patients and the general public. a systematic review of randomized controlled clinical trials on use of respiratory protection by healthcare workers, sick patients and community members was conducted. articles were searched on medline and embase using key search terms. a total of 19 randomised controlled trials were included in this study -8 in community settings, 6 in healthcare settings and 5 as source control. most of these randomised controlled trials used different interventions and outcome measures. in the community, masks appeared to be more effective than hand hygiene alone, and both together are more protective. randomised controlled trials in health care workers showed that respirators, if worn continually during a shift, were effective but not if worn intermittently. medical masks were not effective, and cloth masks even less effective. when used by sick patients randomised controlled trials suggested protection of well contacts. the study suggests that community mask use by well people could be beneficial, particularly for covid -19, where transmission may be pre-symptomatic. the studies of masks as source control also suggest a benefit, and may be important during the covid-19 pandemic in universal community face mask use as well as in health care settings. trials in healthcare workers support the use of respirators continuously during a shift. the use of personal protective equipment for coronavirus disease (covid-19) has been controversial, with differing guidelines issued by different agencies (1) . coronavirus disease is caused by severe acute respiratory syndrome coronavirus2 (sars-cov-2), a beta-coronavirus, similar to severe acute respiratory syndrome coronavirus2 (sars cov) (1). seasonal alpha and beta coronaviruses cause common colds, croup and broncholitis. the transmission mode of coronaviruses in humans is similar, thought to be by droplet, contact and sometimes airborne routes (2) (3) (4) . the world health organization recommends surgical mask for health workers providing routine care to a coronavirus disease patient (5), whilst the us centers for disease control and prevention recommend a respirator (6) . most authorities are recommending that community members not wear a mask, and that a mask should only be worn by a sick patient (also referred to as source control) (7) . there are more randomised controlled trials of community use of masks in well people than studies of the use by sick people (source control). the aim of this study was to review the randomised controlled trials evidence for use of masks and respirators by the community, health care workers and sick patients for prevention of infection. we searched medline and embase for clinical trials on masks and respirators using the key words "mask", "respirator", and "personal protective equipment". the search was conducted between 1 march to april 17 2020 and all randomised controlled trials published before the search date were included. two authors (crm and aac) reviewed the title and abstracts to identify randomised controlled trials on masks and respirators. we also searched relevant papers from the reference lists of previous clinical trials and systematic reviews. studies that were not randomised controlled trials, were about anaesthesia, or not about prevention of infection were excluded. animal studies, experimental and observational epidemiologic studies were also excluded. studies published in english language were included. we found 602 papers on medline and 250 on embase. 820 papers were excluded by title and abstract review. full texts were reviewed for 32 papers and 18 were selected in this review. results were reported according to the preferred reporting items for systematic reviews and meta-analyses (prisma) criteria (8) . in general, the results show protection for healthcare workers and community members, and likely benefit of masks used as source control. we found eight clinical trials (9-16) on the use of masks in the community (table 1 ). in the community, masks appear to be more effective than hand hygiene alone, and both together are more protective (9, 12) . however, the randomised controlled trials which measured both hand hygiene and masks measured the effect of hand hygiene alone, but not of masks alone (9, 12, 16) . masks were only examined in combination with hand hygiene. therefore the protective effect of masks and hand hygiene combined could be due to both interventions together, or the effect of masks alone. the use of hand hygiene alone in these trials was not effective. in more than one trial, interventions had to be used within 36 hours of exposure to be effective (9, 15, 16) . to date, six randomised controlled trials (17) (18) (19) (20) (21) (22) has been conducted on the use of masks and/or respirators by healthcare workers in health care settings ( table 2 ). the healthcare workers trials (table 2) used different interventions and different outcome measures, and one was in the outpatient setting. a japanese study had only 32 subjects, and likely was underpowered to find any difference between masks and control (18) . two north american trials of masks and respirators against influenza infection found no difference between the arms, but neither had a control arm to differentiate equal efficacy from equal inefficacy (17, 22) . without a control group to determine rates of influenza in unprotected healthcare workers, neither study is able to determine efficacy if no difference was observed between the two interventions. a serologic study showed that up to 23% of unprotected healthcare workers (a rate identical to that observed in loeb the trial, which also used serology) contract influenza during outbreaks (23) , which suggests lack of efficacy. studies of nosocomial influenza generally find lower influenza attack rates in unprotected healthcare workers than observed in the loeb trial (24) . further problems with this study are that the majority of subjects were defined as having influenza on the basis of serological positivity (22) . the 10% seroconversion to pandemic h1n109 (with no pandemic virus isolation or positive pcr) observed in the trial, suggests that pandemic h1n109 was circulating in ontario before april 2009, which is unlikely. the overall flu rate was 38%, higher than the expected attack rate in a pandemic (22) . the majority of subjects defined as having influenza were by serology. a serological definition of influenza can be affected by vaccination. the authors claim they excluded influenza vaccinated subjects in the outcome, but according to figure 1 , these subjects (130 in total) are included in the analysis. if they had been excluded and even if no other subjects were excluded, the total analysed would be 348, which is lower than the 422 subjects analysed (22) . these 130 vaccinated subjects should have been excluded entirely from the analysis. the vaccination status of subjects with seropositivity is not provided in the paper, but it appears people with positive serology due to vaccination may have wrongly been counted as influenza cases (22) . in both the north american trials, the intervention comprised wearing the mask or respirator when in contact with recognized ili or when doing a high risk procedure, which is a targeted strategy (17, 22) . one was in an outpatient setting. (17) we conducted a randomised controlled trial comparing the targeted strategy tested in the two north american studies, with the wearing of respiratory protection during an entire shift, and showed efficacy for continual (but not targeted) use of a respirator (19) . the study also did not show efficacy for a surgical mask worn continually, and therefore no difference between a surgical mask and targeted use of a respirator (19) , which is consistent with the findings of the north american trials (17, 22) . in summary, the evidence is consistent that a respirator must be worn throughout the shift to be protective. targeted use of respirators only when doing high risk procedures and medical mask use is not protective. another randomised controlled trial we conducted in china showed efficacy for continual use of a respirator, but not for a mask, and also found fit-testing of the respirator did not affect efficacy (20) . however, this may be specific to the quality of the tested product, and is not generalisable to other respirators -fit testing is a necessary part of respirator use (25) . for healthcare workers, there is evidence of efficacy of respirators if worn continually during a shift, but no evidence of efficacy of a mask (19, 20) . for hospitals where covid-19 patients are being treated, there is growing evidence of widespread contamination of the ward environment, well beyond 2 meters from the patient, as well as aerosol transmission (2, 26, 27) . several studies have found sars-cov-2 on air vents and in air samples in intensive care units and covid-19 wards (26, 28, 29) , and an experimental study showed the virus in air samples three hours after aerosolization (30). the weight of this evidence and the precautionary principle(31, 32), favors respirators for healthcare workers. we showed lower rates of infection outcomes in the medical mask arm compared to control, but the difference was not significant (20) . it could be that larger trials are needed to demonstrate efficacy of a mask, but any protection is far less than from a respirator. a trial we conducted in vietnam of 2-layered cotton cloth masks compared to medical masks showed a lower rate of infection in the medical mask group, and a 13 times higher risk of infection in the cloth mask arm (21) . the study suggests cloth masks may increase the risk of infection (21), but may not be generalizable to all home-made masks. the material, design and adequacy of washing of cloth masks may have been a factor (33) . there are no other randomised controlled trial of cloth masks published, but if any protection is offered by these it would be less than even a medical mask. table 3 shows the trials of source control. there were five randomised controlled trials identified of masks used by sick patients (34) (35) (36) (37) . one was an experimental study of 9 influenza patients, which did not measure clinical endpoints (34) . participants with confirmed influenza coughed onto a petri dish wearing a n95 respirator or a mask. no influenza grew on the medium. a trial of 105 sick patients wearing a mask (or no mask) in the household found no significant difference between arms (36). however, the trial was terminated prematurely and did not meet recruitment targets, so was probably underpowered. one randomised controlled trial was conducted among hajj pilgrims, with both well and sick pilgrims wearing masks, and low rates of ili were reported among contact of mask pilgrims (37) . our randomised controlled trial is the largest available, and studied 245 patients randomised to mask or control (35) . compliance was suboptimal in the mask group and some controls wore masks. the intention to treat analysis showed no difference, but when analysed by actual mask use, the rate of infection in household contacts was lower in those who wore masks (35) . a trial with an experimental design was published in april 2020, examining a range of viruses including seasonal human coronaviruses (38) . this showed that coronaviruses are preferentially found in aerosolized particles compared to large droplets, and could be expelled by normal tidal breathing. wearing a surgical mask prevented virus from being exhaled. there are more randomised controlled trials of community use of masks in well people (9) (10) (11) (12) (13) (14) (15) (16) than studies of the use by sick people (also referred to as "source control"), and these trials are larger than the few on source control (34) (35) (36) . the evidence suggests protection of masks in high transmission settings such as household and college settings, especially if used early, if combined with hand hygiene and if wearers are compliant (9, (12) (13) (14) (15) (16) . if masks protect in high transmission settings, they should also protect in crowded public spaces, including workplaces, buses, trains, planes and other closed settings. the trial which did not show efficacy used influenza as the outcome measure (10) , which is a rare outcome, so requires a larger sample size for adequate power and may have been underpowered. for healthcare workers, the only trials to show a difference between respirators and masks demonstrated efficacy for continuous use of a respirator through a clinical shift, but not masks (19, 20) . the two trials which showed no difference are widely cited as evidence that masks provide equal protection as respirators (17, 22) . however, without a control arm, the absence of difference between arms could reflect equal efficacy or inefficacy, and it is not possible to draw any conclusions about efficacy. the high rates of influenza in the loeb trial suggest equal inefficacy, and further, there were likely misclassified outcomes in the trial by inclusion of seropositive, vaccinated healthcare workers, which would have biased the results (22) . the outpatient setting in the us trial may have had lower exposure risk than the inpatient setting of other trials. (17) in both the north american trials, the intervention comprised wearing the mask or respirator when in contact with recognized ili or when doing a high risk procedure (17, 22) . the underlying assumption that the majority of infections in healthcare workers occur during self-identified high-risk exposures is not supported by any evidence. it assumes healthcare workers can accurately identify when they are risk in a busy, clinical setting, when the majority of infections may occur when healthcare workers are unaware of the risk (such as when walking through a busy emergency room or ward where aerosolized virus may be present). conversely, infections could occur outside the workplace. this could explain the lack of difference if there was no actual efficacy of either arm and if much of the infection occurs in unrecognised situations of risk either within or outside the workplace. in practice, hospital infection control divides infections into droplet or airborne spread, and recommends droplet (mask) or airborne (respirator) precautions accordingly (39) . in a pooled analysis of both healthcare worker trials, we showed that continual use of a respirator is more efficacious in protecting healthcare workers even against infections assumed to be spread by the droplet route (39) . medical masks did not significantly protect against viral, bacterial, droplet or other infection outcomes. however, the summary odds ratio for masks was less than one, which suggests a low level of protection. targeted use of respirator protected against bacterial and droplet infections, but not against viral infections, suggesting viral infections may be more likely to be airborne in the hospital setting (39) . the five available studies of mask use by sick patients suggest a benefit, but are much smaller trials than the community trials, two without clinical endpoints, and with less certainty around the findings (34) (35) (36) (37) . only 3/5 trials examined clinical outcomes in close contacts (35) (36) (37) . many systematic reviews have been conducted on masks, respirators and other ppe in past (40) (41) (42) (43) (44) (45) (46) (47) (48) (49) . these reviews generally examined multiple interventions (e.g. masks and hand hygiene etc), often combined different outcome measures that were not directly comparable and were inconclusive. moreover, most of these reviews did not include more recent randomised controlled trials (17, 21) . this systematic review only focuses on masks and respirators and contains all new studies. in summary, there is a growing body of evidence supporting all three indications for respiratory protectioncommunity, healthcare workers and sick patients (source control). the largest number of randomised controlled trials have been done for community use of masks by well people in high-transmission settings such as household or college settings. there is benefit in the community if used early, and if compliant. they also found no evidence of efficacy of hand hygiene or health education, suggesting mask use is more protective than hand hygiene. respirators protect healthcare workers if worn continually, but not if worn intermittently in self-identified situations of risk. this supports the suggestion that the health care environment is a risk to healthcare workers even when not doing aerosol generating procedures or caring for a known infectious patient. for covid-19 specifically, the growing body of evidence showing aerosolisation of the virus in the hospital ward highlights the risk of inadvertent exposure for healthcare workers and supports the use of airborne precautions at all times on the ward (26, 28, 29) . further, the rule of 1-2 m of spatial separation is not based on good evidence, with most research showing that droplets can travel further than 2m, and that infections cannot be neatly separated into droplet and airborne (39, 50) . in the uk, one healthcare trust found almost one in five healthcare workers to be infected with covid-19 (51) . the deaths of healthcare workers from covid-19 reflect this risk (52) . the use of masks by sick people, despite being the who's only recommendation for mask use by community members during covid-19 pandemic, is supported by the smallest body of evidence. source control is probably a sensible recommendation given the suggestion of protection and given specific data on coronaviruses showing protection (38) . it may help if visitors and febrile patients wear a mask in the healthcare setting, whether in primary care or hospitals. universal face mask use is likely to have the most impact on epidemic growth in the community, given the high risk of asymptomatic and pre-symptomatic transmission (53) . research fellowship) and sanofi currently. she has received funding from 3m more than 5 years ago for face mask research. abrar ahmad chughtai had testing of filtration of masks by 3m for his phd more than 5 years age. 3m products were not used in his research. he also has worked with cleanspace technology on research on fit testing of respirators (no funding was involved). epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in wuhan, china: a descriptive study surface environmental, and personal protective equipment contamination by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) from a symptomatic patient molecular and serological investigation of 2019-ncov infected patients: implication of multiple shedding routes infection prevention and control during health care when novel coronavirus (ncov) infection is suspected. interim guidance 2020 interim healthcare infection prevention and control recommendations for patients under investigation for 2019 novel coronavirus policies on the use of respiratory protection for hospital health workers to protect from coronavirus disease (covid-19) preferred reporting items for systematic review and meta-analysis protocols (prisma-p) facemasks, hand hygiene, and influenza among young adults: a randomized intervention trial findings from a household randomized controlled trial of hand washing and face masks to reduce influenza transmission in bangkok, thailand. influenza and other respiratory viruses impact of nonpharmaceutical interventions on uris and influenza in crowded, urban households mask use, hand hygiene, and seasonal influenza-like illness among young adults: a randomized intervention trial. the journal of infectious diseases face mask use and control of respiratory virus transmission in households. emerging infectious diseases preliminary findings of a randomized trial of non-pharmaceutical interventions to prevent influenza transmission in households the role of facemasks and hand hygiene in the prevention of influenza transmission in households: results from a cluster randomised trial facemasks and hand hygiene to prevent influenza transmission in households: a cluster randomized trial n95 respirators vs medical masks for preventing influenza among health care personnel: a randomized clinical trial use of surgical face masks to reduce the incidence of the common cold among health care workers in japan: a randomized controlled trial a randomized clinical trial of three options for n95 respirators and medical masks in health workers a cluster randomized clinical trial comparing fit-tested and non-fit-tested n95 respirators to medical masks to prevent respiratory virus infection in health care workers a cluster randomised trial of cloth masks compared with medical masks in healthcare workers surgical mask vs n95 respirator for preventing influenza among health care workers: a randomized trial incidence and recall of influenza in a cohort of glasgow healthcare workers during the 1993-4 epidemic: results of serum testing and questionnaire influenza in the acute hospital setting. the lancet infectious diseases examining the policies and guidelines around the use of masks and respirators by healthcare workers in china, pakistan and vietnam transmission potential of sars-cov-2 in viral shedding observed at the university of nebraska medical center aerosol and surface distribution of severe acute respiratory syndrome coronavirus 2 in hospital wards detection of air and surface contamination by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) in hospital rooms of infected patients aerodynamic characteristics and rna concentration of sars-cov-2 aerosol in wuhan hospitals during covid-19 outbreak respiratory protection for healthcare workers treating ebola virus disease (evd): are facemasks sufficient to meet occupational health and safety obligations? uncertainty, risk analysis and change for ebola personal protective equipment guidelines a quantitative assessment of the efficacy of surgical and n95 masks to filter influenza virus in patients with acute influenza infection cluster randomised controlled trial to examine medical mask use as source control for people with respiratory illness surgical mask to prevent influenza transmission in households: a cluster randomized trial pilot randomised controlled trial to test effectiveness of facemasks in preventing influenza-like illness transmission among australian hajj pilgrims in 2011 respiratory virus shedding in exhaled breath and efficacy of face masks the efficacy of medical masks and respirators against respiratory infection in healthcare workers. influenza and other respiratory viruses the use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence. influenza and other respiratory viruses protecting healthcare workers from pandemic influenza: n95 or surgical masks? critical care medicine protecting health care workers from sars and other respiratory pathogens: a review of the infection control literature physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review physical interventions to interrupt or reduce the spread of respiratory viruses. the cochrane database of systematic reviews physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review non-pharmaceutical public health interventions for pandemic influenza: an evaluation of the evidence base physical interventions to interrupt or reduce the spread of respiratory viruses -resource use implications: a systematic review personal protective equipment for preventing highly infectious diseases due to exposure to contaminated body fluids in healthcare staff airborne or droplet precautions for health workers treating covid-19? the journal of infectious diseases roll-out of sars-cov-2 testing for healthcare workers at a large nhs foundation trust in the united kingdom death from covid-19 of 23 health care workers in china temporal dynamics in viral shedding and transmissibility of covid-19. medrxiv key: cord-289521-zun6tp2o authors: leonard, scott; strasser, wayne; whittle, jessica s.; volakis, leonithas i; debellis, ronald j.; prichard, reid; atwood, charles w.; dungan, george c. title: reducing aerosol dispersion by high flow therapy in covid‐19: high resolution computational fluid dynamics simulations of particle behavior during high velocity nasal insufflation with a simple surgical mask date: 2020-05-29 journal: j am coll emerg physicians open doi: 10.1002/emp2.12158 sha: doc_id: 289521 cord_uid: zun6tp2o objective: all respiratory care represents some risk of becoming an aerosol generating procedure (agp) during covid‐19 patient management. personal protective equipment (ppe) and environmental control/engineering is advised. high velocity nasal insufflation (hvni) and high flow nasal cannula (hfnc) deliver high flow oxygen (hfo) therapy, established as a competent means of supporting oxygenation for acute respiratory distress patients, including that precipitated by covid‐19. although unlikely to present a disproportionate particle dispersal risk, agp from hfo continues to be a concern. previously, we published a preliminary model. here, we present a subsequent high‐resolution simulation (higher complexity/reliability) to provide a more accurate and precise particle characterization on the effect of surgical masks on patients during hvni, low‐flow oxygen therapy (lfo2), and tidal breathing. methods: this in‐silico modeling study of hvni, lfo2, and tidal breathing presents ansys fluent computational fluid dynamics simulations that evaluate the effect of type i surgical mask use over patient face on particle/droplet behavior. results: this in‐silico modeling simulation study of hvni (40l∙min(‐1)) with a simulated surgical mask suggests 88.8% capture of exhaled particulate mass in the mask, compared to 77.4% in lfo2 (6l∙min(‐1)) capture, with particle distribution escaping to the room (>1m from face) lower for hvni+mask versus lfo2+mask (8.23% versus 17.2%). the overwhelming proportion of particulate escape was associated with mask‐fit designed model gaps. particle dispersion was associated with lower velocity. conclusions: these simulations suggest employing a surgical mask over the hvni interface may be useful in reduction of particulate mass distribution associated with agps. this article is protected by copyright. all rights reserved covid-19, the clinical disease related to infection with the sars-cov-2 coronavirus (covid19) represents a major world-wide health risk. it is associated with varying degrees of respiratory distress, hypoxemia, and failure. management of the oxygenation of these patients has been the topic of much discussion, receiving current guidance from numerous international and national agencies and organizations. 1,2,3,4 these guidance documents all include the use of high flow oxygen (hfo) therapy in the list of possible interventions. these guidance documents also caution regarding the potential aerosol generation from the use of respiratory support. according to the who, covid-19 is transmitted via respiratory droplets and fomites during close unprotected contact between people. 5 based on current evidence, classically defined airborne spread has not been reported for covid-19 as of this writing and it is not believed to be a major driver of transmission. caution is recommended due to the unclear nature of particle dispersion during aerosol generation. 6 all guidelines are clear and reinforce the requirement for strict adherence to personal protective equipment (ppe) guidelines and use of environmental controls, including negative pressure rooms, when available. agps can produce airborne particles which can remain suspended in the air, travel over a distance and may cause infection if they are inhaled/contacted, therefore, agps create the potential for airborne transmission of infections that may otherwise only be transmissible by the droplet route. 7 respiratory therapies that are known agp's include intubation, extubation and related procedures such as manual ventilation and open suctioning, bronchoscopy, non-invasive ventilation (niv) such as non-invasive positive pressure ventilation (nippv) and continuous positive airway pressure (cpap), high-frequency oscillating ventilation (hfov), high flow oxygen (hfo, hfnc, and hvni), induction of sputum, and any procedure that induces coughing. 8, 9 particle sizes of droplets or aerosolized infectious pathogens can directly have bearing on transmission distance. other factors such as room ventilation, people walking nearby, environmental factors, and air flows of any variety can influence particle dispersion distance from the host/origin. [10] [11] [12] [13] [14] the transmission risk of hfo was brought into question, noting that (1) all agps, including hfnc, are high risk for covid-19 infection transmission; and (2) due to non-universal interfaces across multiple device technologies, that hfnc and niv (specifically nippv), with a potential for poor application to the patient, is not recommended for use without an isolation room. 15 prior research found there was no significant increase in risk for hfo therapy, with lower risk compared to manipulation of oxygen mask, endotracheal aspiration, bronchoscopy, and nebulizer treatment. 8 studies have shown that good interface practice should be in place for niv and hfnc. 6, 16 these studies determined that hfnc aerosol dispersion distance is lower than found in nippv and cpap. good interface practice for hfnc is a simple and practical consideration of cannula placement into the patient nares, whereas a more significant challenge exists in the case of placing an nippv mask-toskin interface. 6, 16 although mechanistically different for ventilatory effect, hvni shares characteristics with hfnc/hfo therapy, in that both deliver heated humidified gas through an open nasal interface, and both able to deliver oxygen-rich gas at supraphysiologic flows, allowing a more precise fio 2 delivery in management of hypoxic respiratory failure. hvni and hfnc have been shown to effectively manage hypoxic respiratory failure in adult patients presenting in the emergency department. 17, 18 high flow therapy in general has demonstrated broad capability to manage acute respiratory failure, wherein a meta-analysis demonstrated that hfnc provided superior outcomes regarding avoidance of endotracheal intubation as compared to conventional oxygen therapy, and comparable rates of intubation compared to nippv. 19 computational fluid dynamics (cfd) is an in-silico simulation method used to evaluate fluid-flow problems. complex geometry is broken down into a mesh of discreet elements. boundary conditions, such a flow inlets, outlets, and surface conditions are applied to the surfaces of some of the elements. an algorithm then iteratively solves the flow in each element based on the boundary conditions and flow conditions in the elements surrounding it. smaller elements increase the accuracy, but also the total number of mesh elements (mesh count) required to model the geometry, thus increasing the computation time for the simulation. there are several advantages in comparing in-silico cfd with in-vitro and in-vivo testing. cfd allows measurements of any fluid property simultaneously at all points in the flow, where other methods only allow measurement at specific points at which sensors are placed. for particle studies, cfd allows precise tracking of particle sizes and location that is generally not possible with other methods. most importantly, cfd allows testing of complex problems without the need to fabricate a physical experiment. there are also disadvantages to cfd, such as the need for careful design of the model and assumptions to avoid obtaining inaccurate results. the addition of a simple surgical mask over a high flow therapy interface has been proposed as a mitigation to particle dispersal. 3 this study evaluated this recommendation in the case of tidal breathing, low flow oxygen therapy (lfo2), and hvni. this study expands upon previous work, and by employing high-resolution cfd. the in-silico model included a room simulation to evaluate the fluid dynamic behavior of the effect of a surgical mask on particles which may be generated in the airway while receiving hvni therapy. a preliminary study was published with lower mesh-count and lower resolution. 20 this report provides a subsequent high-mesh-count simulation with improved fidelity, performed in ansys fluent cfd, of the noted models, thereby generating results with higher reliability/acuity than initially published. computational fluid dynamics (cfd) allows for the simulation of complex flow fields, tracking of particles through those fields, interactions of those particles with the carrier fluid, and the differential capturing of particles by a porous media. evaluation of the use of a type i surgical mask with hvni, low flow oxygen, and tidal breathing was performed in ansys fluent cfd (ansys, inc, canonsburg, pa, usa). simulations were performed on control cases modeling a patient on hvni (40l•min -1 ), low flow oxygen (lfo2) therapy (6l•min -1 via nasal cannula), and simulated breathing (tidal breathing, no therapy) without a surgical mask. summary of all the evaluated cases are shown in table 1 . the patient is modelled to be breathing at 32 breaths per minute with a tidal volume of 500ml with a sinusoidal 1:1 ratio (inspiratory:expiratory) breath curve, without a pause (no interbreath interval) amongst the inspiratory/expiratory phases. the peak expiratory flow rate is 49.0l•min -1 . detailed and expanded description of of the cfd modelling methods, validation, and assumptions are provided in the appendix. a 3d modeled human head, positioned 736mm above the floor with a 30° incline, was placed on a bed in a room. the head model includes a simplified airway structure, an adult small / pediatric cannula (vapotherm® inc, exeter, nh, usa) and a surgical mask (figure 1 ).there are two inlet vents and two outlet vents located on the ceiling and wall near the floor across the room from the patient. there are 6 air changes per hour (ach) implemented to simulate a conservative (non-negative pressure) room ventilation flow. a type i surgical mask, appropriate for use on patients to prevent the spread of droplet particles carrying infectious diseases, is modeled for the simulation (figure 2 , left). the model employs a mask fitted to a simulated head. to imitate clinical practice, gaps between skin and mask were modeled in eight discrete locations (figure 2 , right). simulated gaps were modelled as a 'poor-fitting' mask at the nose (e.g., failure to 'pinch the nose' at the bridge of the nose/face interface). each side of the face has one gap which simulates a cannula tube passing through the edge of the mask. the vapotherm adult-small/pediatric cannula nose piece is modeled in position with its prongs in the simulated nares. therapeutic gas flow is defined to emit from the prongs of this cannula. the mask properties were obtained from the standard governing surgical masks, en14683 21 , and from data in chen et al., aerosol penetration through surgical masks. 22 the mask is modelled as a porous medium which allows flow to pass through with a pre-defined resistance. particle penetration is obtained from chen et al data for a mask with a filtration layer at 100l•min -1 . as the simulated flow rate through the modeled mask does not exceed 80l•min -1 , this is conservative. as the chen et al data does not include efficiency for particle sizes above 4µm, the data was extrapolated with the assumption that for every additional 5µm, the percentage of particles passing through is halved. the distribution of particle sizes emitted by a patient breathing, talking, coughing, and sneezing has been investigated in several studies. the specific distributions vary, however, the range of particle sizes that are meaningful to the study is generally from 0.1 to 100µm. particles larger than 100µm are highly unlikely to penetrate a mask or travel far without a very high velocity flow. particles smaller than 0.1µm account for a very small fraction of the total particles are likely to escape regardless of a mask and will remain airborne regardless of the velocity. the particle distribution (table 3) , for the simulation is taken from exhaled droplets due to talking and coughing. 13 particles smaller than 0.1µm and larger than 100µm were not included virtual particles are introduced in this simulation at just above the larynx, and material properties (mass) of the particles/droplets were defined as water in the ansys model. this allows the model to account for both particle size, as denoted in table 2 , and particle mass using water as a correlate. the standard clinical room simulation is transient, accounting for variations of the flow with time caused by cyclic breathing. the simulation was allowed to run until the flow in the room reached a steady state. streamlines of the fully developed room ventilation flow are shown in figure 4 . the simulations then run for six breath cycles (9.8sec). particles are injected at five timesteps near peakexpiratory (pe); pe -0.2sec, pe -0.1sec, pe +0.1sec, and pe +0.2sec. the particles are tracked along their trajectories (lagrangian) and their final position is calculated. the particle final positions are grouped into one of the following categories, with the results averaged across the five timesteps: (1) caught in the mask, (2) trapped in the vicinity of the patient, and (3) escaped. particles caught in the mask are absorbed in the filter and become trapped, and as such are removed from consideration in the additional airflow dynamics. particles trapped in the vicinity of the patient are deposited on the patient head, upper torso, bed, or pillow with path lengths less than 1m, normally considered a likely risk area. escaped particles are considered to have traveled further than 1m and could remain in an airflow for longer time within the room. sensitivity studies were performed to ascertain the effects of various computational methods used in the fluid flow simulation. based on the sensitivity studies, the final simulations were all run using the 16.2.1 solver, sst turbulence model, 0.001sec time step, and without advanced numerics (to be more conservative). particle modelling was performed in post-processing using 1-way coupling, so the feedback effects of momentum and turbulence augmentation or suppression by the particles on the fluid flow are not considered. a sensitivity study of mass flow rate of particles on the results confirmed that the mass flow does not affect the percentage of particles caught in the mask or in the vicinity of the patient. larger particles may remain suspended for a longer time in a flow which has a higher velocity. this demonstrates that in all cases the velocity of the expiratory flow is substantially reduced by the presence of a mask. the mask resists high velocity flow through the media and distributes the flow through a larger area. this diffusing effect results in a much lower velocity in the area near the patient's face and does not allow jetting of flow over long distances, shown graphically by the velocity contours, along the sagittal plane, for all tested cases ( figure 5 ). even with the loosely fitted mask modelled in this simulation, most of the flow does not pass through the simulated mask, but rather exits through the designed gaps between skin and mask. near peak-expiratory flow was defined as expiratory flow that is within 10% of peak-expiratory flow ( table 3) . although the percentage of flow loss near peak-expiratory flow is very high, ranging from 67.9% (hvni) to 76.2% (tidal breathing, no therapy), the exiting flow velocity is similarly reduced as compared to flow that passes through the mask, demonstrated by evaluating the isosurfaces for all cases at peak expiratory flow ( figure 6 ). all points on the isosurfaces have a velocity of 0.5m•sec -1 . in the cases where a mask is present, the velocity is both reduced and is redirected back toward the patient rather than out into the room. images of results without a mask in place are not shown. with an actual mask in place, flow passes through the mask and is filtered to remove approximately 96.5% of particles by mass when weighted by the distribution of particles and the efficiency of the filter for those particle sizes. this efficiency would be the upper limit of filtration for a perfectly sealed mask. the flow demonstrated in this simulation, which does escape through the gaps followed a tortuous path, which tended to cause the larger particles to impact the surface of the mask, face, and cannula. these particles remain trapped in the areas around the model's head. relative pressure in the airway and inside the mask for each of the three cases modeling the mask show increasing therapy flow (from 6 to 40l•min -1 ) resulting in an increase in relative pressure in the upper airway and mask (figure 7 ). in the case of hvni, a high-pressure region is also present at the surface of the mask where the high velocity flow from the mouth impacts the mask. this localized high pressure gradient across the mask forces flow through the mask in the localized area. this can also be observed as a region of increased velocity is present outside of the mask ( figure 5 ), directly opposite the high-pressure region. for hvni at 40l•min -1 with a mask, 88.8% of the total particle mass is captured and terminated/deposited in the mask (table 4, figure 8 top), as compared to 77.4% of the total particle mass captured in the mask whilst on lfo2 at 6l•min -1 , and 73.4% for tidal breathing with a mask. the low proportion of total particles which escape the mask during hvni have a longer travel length, with 2.97% of particles settling within 1m, compared to 5.47% for lfo2, and 6.81% for tidal breathing. when the patient simulation is tidal breathing in the room, without therapy and without a surgical mask, 52.3% of total particle mass leaving the nose and mouth will deposit greater than one meter from the face. the proportion of particles >5μm, which are captured in the simulated mask over hvni therapy is 93.4%, as compared to 85.1% whilst receiving lfo2, and 83.9% during tidal breathing. table 5 provides the disposition distribution into two categories: particles sized ≤5μm and >5μm (figure 8 , middle and bottom). this study adds information for current clinical practice decision-making. particle-mass dispersion is reduced in this simulated model with the addition of a surgical mask analogue. the simulation showed that the greatest particle loss was associated through the gaps between the skin and mask , but those locations imparted lower velocities of escaping gas, limiting the overall virtual particle mass dispersion. the amount of particle mass captured by the mask was actually greater for the hvni+mask scenario as compared to the lfo2+mask or tidal breathing+mask scenarios. this is likely due to the greatly increased velocity of gas outflow into the mask matrix seen in this model, promoting capture at the mask and diffusion/deflection of the gas stream. the increased particle capture in the model by hvni+mask as compared to lfo2+mask or tidal breathing+mask is unexpected, given the degree of flow loss by hvni+mask was expected to be higher with higher flow. this suggests that the flow loss occurs 'after' deposition of the particle mass within the mask matrix or on the face. although seemingly counterintuitive, the high-pressure region where the flow impacts the mask offers a probable explanation -the velocity of the flow exiting the mouth during hvni is significantly higher than the other cases, causing greater momentum of the gas and particles through the mask. as much of the flow is redirected toward the designed gaps, the particles' momentum resists directional change. the momentum propels particle trapping/deposition into the mask. while a greater proportion of larger particles (>5μm) are trapped/deposited in the mask, the effect of increasing the velocity of the flow (lfo2 to hvni) promulgates a greater difference in the capture of smaller particles (≤5μm). for particles >5µm during hvni, the mask captures 9.75% more particles than lfo2, and 11.32% more particles than no therapy (tidal breathing). for particles ≤5µm during hvni, the mask captures 130.72% more particles than lfo2, and 223.45% more particles than no therapy (tidal breathing). in all cases, the importance of using a mask to reduce the particle dispersion is evident (figure 8 ). without a mask, most particles disperse beyond the immediate area of the patient. increased velocity translates to increased particle spread into the room (77.0%, 63.7%, 52.3%) for hvni, lfo2 and tidal breathing, respectively. this difference is primarily due to the behavior of larger particles/droplets escaping into the room (73.3%, 58.1, 44.0%), respectively. there is less disparity between therapies (100.0%, 98.0%, 94.5%, respectively), for the smaller particles (<5μm), as these may remain suspended in the room with less velocity. adding to previous simulations, these ansys results are considered more robust due to the higher mesh density (3.0•10 6 vs 8.8•10 5 elements), finite mask thickness, improved mesh design, finer timesteps, better numerics, inclusion of lift effects, and more robust particle tracking. 20, 23 this model suggests that the addition of a surgical mask, placed over the mouth and nose of the patient, may significantly reduce the spread of these particles by reducing the flow's velocity through the gaps, thereby decreasing the particles escaping into the room. an important finding was that the overwhelming majority of particles escaping the mask were associated with the model design of the simulation. while this model is intended to simulate a 'worst-case' real-world clinical application, the findings suggest attention must be paid to securing the mask to the face. the who has suggested the primary mode of transmission was droplet. 5 this has been brought into question with more recent findings suggesting the maintenance of viral activity in smaller (aerosol) particles. 24 the mask also captured a greater proportion of smaller particles (≤5μm) than were captured while receiving lfo2 or tidal breathing alone. these findings support the notion that a mask over the nasal interface during hvni may substantially reduce the particulate burden in the room around the patient. clinicians and healthcare workers must always wear personal protective equipment (ppe) as well as practice droplet precautions during patient interactions with suspected or confirmed covid-19, as the risk of agp in the care of the patients may remain an issue. newer information suggests important physiological phenotypes which may be better suited to noninvasive support than to invasive mechanical ventilation. 25 the role of invasive mechanical ventilation as the 'first line' therapy after simple oxygen management fails has been brought into question. 26 as such, the ability to limit the overall environmental exposure becomes important. although modeling of liquid and bacterial pathogen dispersal demonstrated that high flow therapy limited the dispersion to the area proximate to the face and cannula, the issue of partial contamination remains concerning. 27 particle sizes of droplets or aerosolized infectious pathogens can directly have bearing on transmission distance. although sars-cov-2 associated with covid-19 is reported as 0.06-0.14μm in size, these viral/infectious particles may be carried in droplets and aerosols when you talk/cough/sneeze. 28, 29 a 2018 study measuring influenza virus presence in droplets from a coughing patient noted that the influenza virus was present in 42%, 23%, and 35% of droplets/particles sized <1μm, 1-4μm, and >4μm, respectively. 30 this cfd simulation suggests that there may be capture of the majority of aerosol particles (≤5μm) and almost all larger particles (>5μm). the area immediately proximate to the patient's face may remain the likely 'hot zone' for higher contact likelihood even when a mask is employed in clinical practice. the strength of the study was built upon the following: inclusion of real-life variables outlining details such as an average fitting type i surgical mask with appropriate gaps as a result of fitting. the quality and type of mesh in the mask was designed per type i mask specifications. a room demonstrating particle dispersion via a fixed patient space, over time, under appropriate hospitalgrade airflow conditions. the particle sizes were engineered to simulate a range of human particle sizes that are emitted during breathing and while on multiple varieties of oxygen support. the quality and high fidelity of analysis using ansys in this simulation which increased the specificity of the test and carried out the particle behavior in the room over time compared to the previous simulation trial that utilized solidworks for simulation. in addition, the range and modality of comparators used, dispel bias measured with and without a mask in place, tidal breathing, lfo2 at 6l•min -1 , and hvni at 40l•min -1 . this method of testing provided extremely specific measurable qualities. this simulation contained aerosolized particles that were engineered to have a wide range of size. these results may be applicable to other operations characterized as agps. limitations of the simulation include the fact this is an in-silico model. in-vivo testing to determine particle distribution would be methodologically difficult, with limited ability to further quantify the nature and result of the droplets/particles. such testing may be an important follow-on study once adequate methodologies have been identified. the current simulation model is high-fidelity and takes both a 'functioning room' geometry and dynamics into account, including air currents, as well as plausible particle mass distributions in a breathing model, and includes an accurate rendering of the mask behavior. as such it is informative for clinical decision making but has not been tested in vivo. such testing will no doubt further refine the clinician decision making in the management of these patients. the designed limitation of mask-fit served the simulation well in highlighting the importance of mask-fit for any real-world utilization of a similar model. another limitation may be the studied particle size thresholds in the findings and applying these to situations in which there are predominantly smaller particles. however, smaller particle masses were studied as part of this evaluation and an advantage of using the mask is demonstrated in this subgroup. finally, the actual dynamics were tested at a single flowrate for hvni and for lfo2, although the anticipated behavior of the mask capture simulated in that pair of scenarios would suggest 'worst case'. the fact that tidal breathing and breathing with lfo2 in this simulation were both associated with potential particulate dispersal, these findings may suggest a role for use of a simple surgical mask in the care of any covid-19 patient in the acute care environment. the use of masks are likely to help address issues of cough and sneeze, which have been associated with high velocity impulses know to transit particulate mass great distances. 31 these surgical mask simulations would not change current recommendations to use negative pressure rooms, when available. hvni with a mask may be the safest option in an overwhelmed system (insufficient negative pressure rooms), where patients are treated in simple rooms (as modeled in this study). regarding disinfection/cleaning implications, these findings suggest no substantive change to current practices because particle escape remains dependent on mask security and due to the fact that respiratory-therapy related transmission is only one means of dispersal of particulate contaminants. however, practically, the results for this particular configuration and simulation infer that additional focus could be placed on areas behind the patient head. cleaning procedures should be completed correctly and consistently to prevent excess viral load accumulation on fomites, thereby decreasing risk of infectious particle/droplet transmission. non-invasive therapies such as high flow oxygen are widely used in management of acute critically ill patients with respiratory distress. such patients present a potential droplet-transmissive risk during care. personal protective equipment and environmental control/engineering should be a primary concern/consideration when managing patients with covid-19. this model corresponds with prior work indicating that even tidal breathing disperses particles some distance. this model also suggests that when making decisions regarding limitation of potentially infectious droplets/particles, the application of a simple surgical mask, which is well-fit to the patient's face, may reduce the velocity of escaping gas and capture particles. this adjunct must be balanced against the totality of the patient care situation, as the addition of a surgical mask adds, albeit very slightly, to the complexity of management of the patient. clinicians will have to decide on the cadence for changing such masks, if required, based on the particular circumstances in management of that patient. no recommendations regarding that aspect of care can be made from these data. these insilico findings should be evaluated in-vivo with appropriately constructed clinical trials. this appendix is intended to provide additional cfd model specificity for reproducible study results. the room model used in the simulation measures 4.87m x 3.65m x 2.44m with a total volume of 43m 3 . two inlet vents are positioned on the ceiling (dimensions 0.305m x 0.305m), and two outlet vents (0.305m x 0.305m) located on the centerline of the wall across from the patient, with one near the floor and the other near the ceiling. a 3d model of a human head is positioned on a bed 736mm above the floor with a 30° incline. the head model includes a simplified airway structure. the mouth opening is rectangular with rounded corners (5mm x 20mm with 2.5mm radius corners). the nasal openings each measure 8mm x 9mm with 2.5mm rounded corners. an adult small / pediatric cannula (vapotherm® inc., exeter, nh, usa) is positioned with its prongs in the center of the nasal openings. the flow opening of the nasal cannula measured 2.62mm in diameter. the airway model extends to a point just above the larynx, where the fluid passage is terminated with a planar surface. this surface is used as both a flow opening for the breathing flow and the source of the particles introduced into the flow. a model of a type i surgical mask is fitted to simulated head. the mask is modelled with a thickness of 4mm to allow a mesh with 4 hexahedral elements across the thickness without requiring prohibitively small mesh elements. the mask properties are adjusted to account for the modelled thickness. to imitate clinical practice, the designed emission-openings were modeled in eight discrete locations (figure 2 , right). the total cross section of the emission-openings is 679mm 2 , thereby modeling a 'poor fitting' of the mask at the nose (e.g., failure to 'pinch the nose' at the bridge of the nose/face interface). each side of the face has one emission-opening which simulates a cannula tube passing through the edge of the mask. the discrete emission-openings have the same cross section as a 1.3mm gap around the entire perimeter. discrete emission-openings were used to improve cfd performance. modelling the emission-opening as a continuous narrow channel would have required a finer mesh to accurately simulate the emissions. the mask pressure-drop properties were obtained from the standard governing surgical masks, en14683 21 , and from data in chen et al., aerosol penetration through surgical masks. 22 the mask is modelled as a porous medium which allows flow to pass through with a pre-defined resistance. the pressure drop of the mask is modelled to be in accordance with en14683 and chen et al, providing a pressure drop of 29.4 pa•cm -2 for a test area of 4.9cm 2 . the velocity and pressure drop data used to model the porous media properties is given in table a1 . the porous media properties were validated by modelling the standard test defined in en14683. using the 4mm thick mask, a test area of 4.9 cm 2 and the defined porous media properties a pressure drop of 29.4 pa•cm -2 was obtained in the validation model. particle penetration is obtained from chen et al. data for a mask with a filtration layer at 100l•min -1 . as the simulated flow rate through the modeled mask does not exceed 80l•min -1 , this is conservative. as the chen et al. data does not include efficiency for particle sizes above 4µm, the data was extrapolated with the assumption that for every additional 5µm, the percentage of particles passing through is halved. above 20µm the filtration efficiency is assumed to be 100%. the filtration efficiency, summarized in table 2 , was used to implement a user defined function (udf) in ansys fluent to remove particles that pass through the filter. when a particle trace enters the porous media volume, the mass travelling along that particle trace is reduced by the filtration efficiency for that size particle. cfd allows for the simulation of complex flow fields, tracking of particles through those fields, interactions of those particles with the carrier fluid, and the differential capturing of particles by a porous media. evaluation of the use of a surgical mask with hvni, low flow oxygen, and tidal breathing was performed in ansys fluent cfd (ansys, inc, canonsburg, pa, usa). simulations were performed on control cases modeling a patient on hvni (40 l•min -1 ), lfo2 therapy (6 l•min -1 via nasal cannula), and simulated breathing (tidal breathing, no therapy) without a surgical mask. summary of all the evaluated cases are shown in table 1 . the patient is modelled to be breathing at 32 breaths per minute with a tidal volume of 500ml with a sinusoidal 1:1 ratio (inspiratory:expiratory) breath curve, without a pause (no inter-breath interval) amongst the inspiratory/expiratory phases. the peak expiratory flow rate is 49.0 l•min -1 . the distribution of assumed spherical particle sizes emitted by a patient breathing, talking, coughing, and sneezing has been investigated in several studies. the specific distributions vary, however, the range of particle sizes that are meaningful to the study is generally from 0.1 to 100µm. particles larger than 100µm are highly unlikely to penetrate a mask or travel far without a very high velocity flow. particles smaller than 0.1µm account for a very small fraction of the total particles are likely to escape regardless of a mask and will remain airborne even in very low velocity flows. the particle distribution (table a2) , for the simulation is taken from exhaled droplets due to talking and coughing. 13 a rosin-rammler diameter distribution method is used during the simulation to generate particles that approximate this particle distribution. particles smaller than 0.1µm and larger than 100µm were not included. the rosin-rammler parameters, ̅ and n = 0.990 are used for the simulation, with the parameters' curve fit shown ( figure a1 ). the particles are released at five time-steps near peak expiratory flow and traced through the flow field at that time step. particles are introduced at just above the larynx, representative as water for material properties. note that all surfaces inside the airway are defined to have ideal reflection for particles that contact those surfaces, such that particles are not absorbed until particles exit the nasal-oral opening of the human airway. table a2 . mass fractions of the particle distribution used in the room simulation (left) and for the curve fit (left and right) of the rosin-rammler diameter distribution ( figure a1 ). figure a1 . rossin-rammler diameter distribution of the particles in the room simulation. mesh geometry of 3 million elements used in the simulation is shown in figure 3 . a hex-dominant mesh is implemented in the mask and the majority of the room volume. tetrahedral elements converted to polyhedron elements are implemented in the regions near the head, where hexdominant meshing was unachievable. as the mask is a critical component for an accurate simulation, the mesh density within the mask is set to achieve a thickness of at least 4 hexahedral elements. hexahedral elements were used in this instance since validation testing in ansys reveals that hexahedra are required for accurate pressure drop results and are preferred for atomization studies. 32 mesh refinement is also applied to the regions around the patient to best achieve accurate particle movement trajectories both near the patient and where particles settle. the patient breathing is modelled as a sinusoidal flow with a frequency of 32 breaths per minute. the breath curve is defined by the equation ̇ where ̇ is the mass flow rate in kg/s. therapy flow is modelled as a constant inlet with a mass flow rate of 8.02•10 -4 kg/sec (40 l/min) or 1.204•10 -4 kg/sec (6 l/min). room ventilation is modelled as an inlet with a constant flow of 0.066 m 3 /sec the simulations are transient, accounting for variation of the flow with time caused by cyclic breathing. the simulation is allowed to run until the flow in the room reaches a quasi-steady state. figure 3 shows the streamlines of the fully developed room ventilation flow. a fixed time step of 0.001sec is used for the simulation. the solver (16.2.1 v 2020r1), turbulence model (rsm v sst), and timestep (0.001s v 0.0001s) had negligible effect on the results (data not shown). use of the advanced numerics option showed a non-negligible increase in particle capture in the mask. this is possibly due to the numerics affecting how the porous media resistance is computed at the interface between the porous zone and the bordering fluid zone. the particle model uses a specified mass flow rate for normalization purposes only. all results are reported as a percentage of the total mass flow rate. a sensitivity study of mass flow rate of particles on the results confirmed that the mass flow does not affect the percentage of particles caught in the mask or in the vicinity of the patient. saffman lift effects are included in the particle simulation. a sensitivity study showed saffman lift increases capture in the mask as compared to neglecting this effect (data not shown). the preliminary simulation and model was published in a chest research letter. 20 upon review of this preliminary work, the authors designed a subsequent model, with the aim to provide a more reliable and accurate simulation. there are several differences between the preliminary study and the current study, which improve the simulation, and thereby provide more reliable findings. first, the mesh across the surgical mask is now hexahedral element instead of tetrahedral element, as tetrahedral element mesh may constrain/influence the properties of the porous media and subsequently may affect the differential particle filtration. second, the hexahedral elements replaced the bulk room geometry mesh, and an increased mesh density was now applied to the area of the room immediately surrounding the patient. third, the current study involves a significantly higher computational cell count and resolution/quality on and around the patient mouth, nose, and internal airway, which provides a lower growth rate as element size transitions more gradually from smaller to larger elements. finally, the emission-openings between the face and mask were previously artificially restricted by use of tetrahedral elements that were converted to polyhedral elements, thus reducing the mesh cell count (resolution) through the emission-openings. this study, with hexahedral elements, does not artificially constrict these emission-openings by allowing the boundary conditions to be fully realized. the effect of this change was to invert the preliminary model results for the proportion of flow that passes through the emission-openings. table 5 . ansys results for the percentage of particle mass by disposition and particle size (≤5µm or >5µm) for all tested cases, both with and without a surgical mask. . ansys results for the percentage of (top) total particle mass disposition, (middle) particle mass disposition for particles ≤5µm, and (bottom) particle mass disposition for particles >5µm for all tested cases with a surgical mask. for particles >5µm during hvni, the mask captures 9.75% more particles than lfo2, and 11.32% more particles than no therapy (tidal breathing). for particles ≤5µm during hvni, the mask captures 130.72% more particles than lfo2, and 223.45% more particles than no therapy (tidal breathing). clinical management of severe acute respiratory infection when novel coronavirus (2019-ncov) infection is suspected: interim guidance. who reference number: who/ncov/clinical surviving sepsis campaign: guidelines on the management of critically ill adults with coronavirus disease 2019 (covid-19) respiratory care committee of chinese thoracic s. [expert consensus on preventing nosocomial transmission during respiratory care for critically ill patients infected by zhonghua jie he he hu xi za zhi = zhonghua jiehe he huxi zazhi = chinese journal of tuberculosis and respiratory diseases report of the who-china joint mission on coronavirus disease 2019 (covid-19) exhaled air dispersion during high-flow nasal cannula therapy versus cpap via different masks. the european respiratory journal infection prevention and control of epidemic and pandemic prone acute respiratory infections in health care aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review department of health and social care -public health wales -public health agency northern ireland -health protection scotland -public health england guidance for infection prevention and control in healthcare settings: adapted from pandemic influenza guidance for infection prevention and control in healthcare settings the role of particle size in aerosolised pathogen transmission: a review factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises the size and concentration of droplets generated by coughing in human subjects exhaled droplets due to talking and coughing study on the initial velocity distribution of exhaled air from coughing and speaking staff safety during emergency airway management for covid-19 in hong kong exhaled air dispersion during noninvasive ventilation via helmets and a total facemask high-velocity nasal insufflation in the treatment of respiratory failure: a randomized clinical trial high-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. the new england journal of medicine can high-flow nasal cannula reduce the rate of endotracheal intubation in adult patients with acute respiratory failure compared with conventional oxygen therapy and noninvasive positive pressure ventilation?: a systematic review and meta-analysis preliminary findings of control of dispersion of aerosols and droplets during high velocity nasal insufflation therapy using a simple surgical mask: implications for high flow nasal cannula aerosol penetration through surgical masks discrete particle study of turbulence coupling in a confined jet gas-liquid separator aerosol and surface stability of sars-cov-2 as compared with sars-cov-1. the new england journal of medicine covid-19 pneumonia: different respiratory treatments for different phenotypes? intensive care medicine basing respiratory management of coronavirus on physiological principles assessment of the potential for pathogen dispersal during high-flow nasal therapy a novel coronavirus from patients with pneumonia in china transmission potential of sars-cov-2 in viral shedding observed at the university of airborne spread of expiratory droplet nuclei between the occupants of indoor environments: a review turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of covid-19 the war on liquids: disintegration and reaction by enhanced pulsed blasting phd, is a research scientist at vapotherm key: cord-306244-8gjng3o9 authors: alizargar, javad title: wearing masks and the fight against the novel coronavirus (covid-19) date: 2020-05-29 journal: pulmonology doi: 10.1016/j.pulmoe.2020.05.011 sha: doc_id: 306244 cord_uid: 8gjng3o9 nan we read with great interest the article by ippolito et al. 1 in which the authors summarized the use of medical masks in the viral outbreaks like the covid-19. they pointed out that wearing medical masks and respirators are critical in the personal protection for the healthcare workers, especially in virus breakouts such as covid-19. they also expressed their concerns about the worldwide mask supplies running out. as their study compared different features of medical masks and respirators, the essential role of wearing masks for both inward and outward protection (protecting the wearer from the environment and the opposite) was emphasized. apart from the inward and outward protection that wearing the mask provides, the indirect effect of wearing masks during epidemics can also be of great importance. as covid-19 is present in saliva, 2 wearing the medical mask stops the transmission of this disease in droplets and aerosols. as patients may be asymptomatic and the reactivation of this disease is possible, 3,4 wearing masks by asymptomatic individuals is strongly recommended. in addition to the direct mechanisms of preventing the spread of the virus, which is the main function of medical masks in viral infections, the other way that wearing the medical masks helps the healthcare systems to combat such epidemics is by decreasing the workload of the healthcare systems and facilitating detection of the new cases. in covid-19 outbreak, the symptoms of the disease are cough, fever, fatigue, diarrhea, headache, sputum production, haemoptysis, dyspnoea and lymphopenia. 5 these symptoms are common among other types of influenza and bacterial common cold. wearing masks will also prevent those types of infections caused by other types of pathogens which are communicable with aerosols and droplets. if all the individuals in a community wear masks, the number of cases referred to the hospitals presenting covid-19 like symptoms decreases. in other words, the work load of the medical system decreases. so, the real cases of covid-19 can be screened out of all other types of influenza and common cold comparatively easily. by referring fewer people to the clinics and hospitals, the chance of the contamination of new patients while visiting the hospitals and clinics also deceases. this strategy might help countries to fight against the outbreak of covid-19. the authors declare that no funding was received for this paper. the authors have no conflicts of interest to declare. medical masks and respirators for the protection of healthcare workers from sars-cov-2 and other viruses saliva samples as an alternative for novel coronavirus (covid-19) diagnosis risk of reactivation or reinfection of novel coronavirus (covid-19) prophylactic anticoagulant therapy for reducing the risk of stroke and other thrombotic events in covid-19 patients the epidemiology and pathogenesis of coronavirus disease (covid-19) outbreak none. javad alizargar * research center for healthcare industry innovation, national taipei university of nursing and health sciences, taipei city 112, taiwan key: cord-288354-7ruoysxu authors: howard, matt c. title: understanding face mask use to prevent coronavirus and other illnesses: development of a multidimensional face mask perceptions scale date: 2020-06-26 journal: br j health psychol doi: 10.1111/bjhp.12453 sha: doc_id: 288354 cord_uid: 7ruoysxu face masks are an avenue to curb the spread of coronavirus, but few people in western societies wear face masks. social scientists have rarely studied face mask wearing, leaving little guidance for methods to encourage these behaviours. in the current article, we provide an approach to address this issue by developing the 32‐item and 8‐dimension face mask perceptions scale (fmps). we begin by developing an over‐representative item list in a qualitative study, wherein participants’ responses are used to develop items to ensure content relevance. this item list is then reduced via exploratory factor analysis in a second study, and the eight dimensions of the scale are supported. we also support the validity of the fmps, as the scale significantly relates to both face mask wearing and health perceptions. we lastly confirm the factor structure of the fmps in a third study via confirmatory factor analysis. from these efforts, we identify an avenue that social scientists can aid in preventing coronavirus and illness more broadly – by studying face mask perceptions and behaviours. but many researchers point out that preventative measures also reduce the spread of illness (chen et al., 2020; long et al., 2019; wang et al., 2020) . among these preventative measures are hand washing, social distancing, andthe focus of the current articleface mask wearing. face masks are cloth coverings worn on the face with the intention to prevent illness. while face masks partially protect the wearer, they are more effective at ensuring that the wearer does not spread their germs (cdc, 2020) . even while the number of coronavirus cases and deaths dramatically increase, those in western populations appear reluctant to wear face masks (bbc, 2020b; friedman, 2020) . a recent study supported that <35% of those in canada, france, germany, and the united kingdom wear face masks to protect themselves from coronavirus, whereas more than 75% in china, india, japan, and vietnam do so (bricker, 2020) . the cause of this resistance is still largely unknown. social scientists frequently study other health behaviours, such as hand washing, smoking cessation, and exercise (ogden, 2012) ; however, very few have investigated face mask wearing. this dearth of research is particularly damaging in the current worldwide landscape, as public health officials have little knowledge regarding effective interventions to encourage face mask wearing. if an avenue was identified to develop such interventions, public health officials argue that the spread of coronavirus could be greatly reduced and millions of lives could be saved (bbc, 2020b; cdc, 2020) . the current article provides a starting avenue to study face mask perceptions, which could lead to the development of interventions to alter face mask wearing. we undergo a three-study process to develop the face mask perceptions scale (fmps), which is a 32-item and 8-dimension measure to gauge justifications for not wearing face masks. we demonstrate that the fmps produces superb psychometric properties, appropriate validity evidence, and significant relations with face mask wearing. in our discussion, we also link the current results with prior frameworks and theories associated with intervention development. we argue that the current results can be broadly framed in the com-b model (michie et al., 2011) , but future researchers should also apply more specific theories (arden & chilcot, 2020; bish & michie, 2010; teasdale et al., 2012) to develop interventions and encourage face mask wearing via perceptual change. the fmps can encourage researchers to integrate face mask wearing with studies on protective behavioursespecially those focusing on the importance of perceptions as done in the current article. notably, a significant base of research has investigated hand washing, and authors have developed complex theoretical frameworks and associated interventions regarding hand washing (aunger et al., 2010; lam et al., 2004; nicholson et al., 2014) . for instance, judah et al. (2009) studied the efficacy of fourteen different messages to target seven psychological mechanisms (including perceptions) and promote hand washing in public restrooms. the authors demonstrated the varied effectiveness of these messages, implied importance of the psychological mechanisms, and influence of gender on the efficacy of the messages. such findings can provide an approach to study face mask wearing, wherein the eight dimensions identified in the current article can be incorporated into associated frameworks and the fmps can be used as an indicator of intervention effectiveness. thus, we assert that it is key for future research to utilize these prior findings regarding protective behavioursand hand washing specificallyto better understand and promote face mask wearing. together, the current article provides many benefits for research and practice. first, we identify an avenue that social scientists can aid in preventing coronavirusstudying face mask perceptions. second, we identify the most common face mask perceptions as well as those with the strongest relation to face mask use, which allows future researchers to target these barriers via interventions to encourage face mask wearing. third, we show that face mask perceptions are complex. people do not simply have positive or negative perceptions of face masks, but they instead have several differentpossibly conflictingperceptions that influence their behaviours. fourth, by assessing face mask perceptions in an eight-dimensional rather than unidimensional manner, we highlight that face mask perceptions and any associated interventions are not a 'one size fits all' approach, as people have varying justifications for not wearing face masks. for all studies, appendix s1 includes the associated datasets, and appendix s2 includes the complete reporting of methods, analyses, and results. study 1 was conducted to generate items for the fmps using mechanical turk (mturk) on 26 april 2020. researchers have supported that results from mturk samples are reliable and valid when sufficient precautions are taken, and we followed prior guidelines for ensuring adequate data quality when using mturk (buhrmester et al., 2018; mellis & bickel, 2020; robinson et al., 2019) . for all studies, we restricted participants to only those with more than 50 mturk assignment completions at a 95% approval rate or better. for studies 2 and 3, we included multiple attention checks and utilized time-separate research designs. via these efforts, we believe that our analyses included only those providing appropriate survey responses. in study 1, two open-ended questions were administered to 205 participants in return us$0.05. the first question queried participants' personal perceptions regarding face masks, whereas the second question queried participants' public perceptions. the questions read as follows: 'face-masks are often recommended to reduce the spread of viruses, but many people don't wear face masks in public. in the box below, please list as many reasons as possible that [you/ people in general] do not wear a face mask when you go out in public. please write at least three reasons'. (bolded and underlined in original questions). the primary author thematically categorized and qualitatively analysed responses following recommendations for item generation and scale pretesting (devellis, 2016; howard, 2018; presser & blair, 1994) . thirteen categories were identified (table 1) . to ensure that an adequate scope of face mask perceptions was assessed in the fmps while being reasonably concise, we developed items for categories with more than a 10% frequency in participants' qualitative responses for either personal or public perceptions. this resulted in the inclusion of eight categories: comfort, efficacy doubts, access, compensation, inconvenience, appearance, attention, and independence. because we intended to develop a concise measure (~30 items), we initially developed six to eight items per category (55 total) to be subsequently reduced to four items per category in the following study. these initial items were developed from participants' responses to ensure content relevance. all initial items can be seen in appendix s3. in study 2, we subject our initial item list to exploratory factor analysis (efa) to support the eight-dimension factor structure and reduce the initial item list to a more concise measure. reducing the item list results in the fmps, and we then assess its construct validity. participants participants (n = 745, m age = 36.76, sd age = 12.59, 45% female, 85% western english-speaking countries) were recruited from mturk and were provided us$1.25. we included nine attention checks and removed participants' responses if they failed any. all statistics, including the reported sample size above, reflect the sample after removing these participants' responses. participants enrolled into study 2 via mturk on 28 april 2020. they provided their informed consent and completed the first survey online (time 1). one day later, they were emailed and completed the second survey (time 2). two days after the second survey, they were emailed and completed the third survey (time 3). we analysed our item list via efa using the recommendations of prior authors (costello & osborne, 2005; fabrigar et al., 1999; howard, 2016) . we applied a principal axis factoring method with direct oblimin rotation, as we expected our factors to be correlated. our initial efa supported an eight-factor solution (appendix s4), but some items did not produce satisfactory results. we removed eight problematic items in a stepwise process, resulting in an intermediate list of 47 items. while these items produced adequate psychometric properties, our intent was to develop a more concise measure. we continued removing items with the lowest primary factor loading in a stepwise manner until four items remained for each factor. our final factor structure can be found in appendix s4. an eight-factor solution was again observed, and each item produced satisfactory factor loadings. we label these 32 final items as the fmps (appendix a). we assessed the relation of the fmps with other relevant variables (table 2) . three variables reflected face mask wearing. none of the eight dimensions significantly correlated to face mask wearing before the prior six months (p > .05), but six of the eight dimensions significantly correlated to face mask wearing within the prior six months as well as the course of the study (p < .05). the two dimensions that did not significantly relate to these two variables were comfort and attention. further, six variables reflected general health perceptions and behaviours. efficacy doubts had the strongest average correlation with each of these variables (average |r| = .35, all p < .01). inconvenience (average |r| = .23, all p < .05) and appearance (average |r| = .23, all p < .05) also significantly correlated to each of these variables, whereas attention (average |r| = .14, five p < .05) and independence (average |r| = .25, five p < .05) significantly correlated to most. lastly, comfort (average |r| = .14, four p < .05), access (average |r| = .07, two p < .05) and compensation (average |r| = .08, two p < .05) each had smaller and fewer significant relationships with these variables. together, most of the fmps dimensions significantly predicted recent face mask usage, but more variation was seen among the dimensions regarding their relation to general health perceptions and behaviours. we confirm the factor structure of the fmps via confirmatory factor analysis (cfa). participants participants (n = 327, m age = 36.46, sd age = 11.52, 43% female, 66% western english-speaking countries) were recruited from mturk and were provided us$0.40. we included five attention checks and removed participants' responses if they failed any. all statistics, including the reported sample size above, reflect the sample after removing these participants' responses. participants enrolled into study 3 via mturk on may 3, 2020. they provided their informed consent and completed the first survey online (time 1). one day later, they were emailed and completed the second survey (time 2). at time 1, we measured age and gender. at time 2, we administered the fmps. we followed the recommendations of prior authors to perform our cfa (brown, 2015; harrington, 2009 ). although our eight face mask perception dimensions are measured via a single scale, we do not consider these dimensions to form a unitary construct. instead, we conceptualize these dimensions as independent perceptions, and therefore, we modelled these dimensions as eight covaried latent factorseach with four indicators. no second-order factors were included. initially, our model fit indices (cfi = .86, ifi = .86, rmsea = .09, srmr = .07, v 2 / df = 3.41) fell short of recommended cut-offs (cfi ≥ 0.95, ifi ≥ 0.95, rmsea ≤ 0.08, srmr ≤ 0.05, v 2 /df ≤ 2.00). five pairs of items had particularly strong modification indices (>10) and loaded onto the same factor. when analysing the content of these pairs, each was near synonyms. we then covaried the error terms of these item pairs because they each loaded on common factors and their association could be clearly justified, which is a process recommended by prior authors (brown, 2015; harrington, 2009 ). the revised model fit indices each met or closely approached recommended cut-offs (cfi = 0.95, ifi = 0.95, rmsea = 0.05, srmr = 0.07, v 2 /df = 1.86). each item strongly loaded onto its respective latent factor (≥ .48), and full reporting of these factor loadings is included in appendix s4. despite dramatic rises in coronavirus, those in western societies appear reluctant to wear face masks (bbc, 2020a (bbc, , 2020b . our goal was to develop the fmps to identify justifications for not wearing face masks. via a three-study process, we developed a measure with satisfactory psychometric and validity evidence. we supported an eightdimension structure via efa and cfa, showing that face mask perceptions are complex. people may have many justifications for not wearing face masks, which poses several implications for research and practice. most broadly, the current results can be situated within the com-b model to understand their association with behavioural change and relevant interventions (michie et al., 2011) . the com-b model synthesizes extant models of behavioural change and provides an organizing framework to identify and interlink behavioural sources, intervention functions, and policy categories. it identifies six behavioural sources, nine intervention functions, and seven policy categories. face mask perceptions are a type of reflective motivation source, which involves evaluation and cognition in developing behavioural attitudes; reflective motivation sources are most closely associated with the intervention functions of education, persuasion, incentivization, and coercion; and these intervention functions are associated with each of the policy categories except environmental/social planning. because several face mask perceptions significantly related to face mask wearing in the current study, future authors should utilize the com-b model to develop face mask interventions associated with education, persuasion, incentivization, and coercionthe relevant intervention functions to reflective motivation sources (and the fmps). in developing these interventions, researchers should integrate frameworks associated with reflective motivation sources and these four intervention functions (arden & chilcot, 2020; bish & michie, 2010; teasdale et al., 2012) . notably, bish, and michie (2010) systematically reviewed determinants of prevention behaviours during a pandemic in response to h1n1 (swine flu). they discovered that predictors of protective behaviours differ based on whether the behaviour is preventive or avoidant, and they identified predictors of face mask wearing in the scope of preventive behaviours. these included demographic characteristics (gender, age, and marital status) and attitudes (perceived severity, perceived susceptibility, social pressure, and perceived efficacy)the latter being a reflective motivation source. only one of these antecedents, perceived efficacy, represents a perception identified in the current article, and thereby their model can be expanded by incorporating the other perceptions. also, face mask perceptions may serve as mediators between certain antecedents and face mask wearing, as many of their antecedents (e.g., demographics, social pressure) are known to influence perceptions (wilson et al., 1988) . identifying specific perceptions (and not others) as mediators may not only increase the sophistication of face mask research, but it would also identify which face mask perceptions may be susceptible to influences and useful to target via interventions. lastly, bish and michie (2010) showed that some antecedents predicted other preventative behaviours but not face mask wearing. this finding suggests that not all relations of preventative behaviours can generalize to face mask wearing, emphasizing the need to replicate results regarding one type of preventative behaviour across each of the other types of preventative behaviours. similar assertions could be made for teasdale et al.'s (2012) findings. these authors supported that, as predicted by protective motivation theory, threats and coping appraisals predict protective behaviours. their experimental manipulations of threat and coping appraisals included the intervention functions of education, persuasion, incentivization, and/or coercionaligning with the proposed associations of reflective motivation sources in the com-b model. future research could extend their findings to face masks by incorporating face mask perceptions as mediators of threats' and coping appraisals' effects on face mask wearing behaviours. additionally, interventions to encourage face mask wearing are not a 'one size fits all' approach. instead, researchers should consider specific perceptions in developing interventions, and the most common perceptions may not be the most important to target. while comfort, for example, was among the most common perceptions reported by participants, it did not have significant relationships with face mask wearing. other perceptions, such as efficacy concerns, may be more fruitful to address. furthermore, face mask perceptions may be associated with differing theoretical frameworks. for instance, the perception of efficacy doubts may be relevant to theory associated with message framing and even fake news (e.g., prospect theory, parallel response theory; effron & raj, 2020; gallagher & updegraff, 2012; murphy et al., 2019) , as perceptions regarding the efficacy of face masks may be largely developed via communicated information and misinformation. other face mask perceptions, such as comfort, may be less relevant to these theoretical approaches, as perceptions of comfort may be more developed through embodied experiences than communicated information. these differences emphasize the need for future researchers to apply multiple theoretical frameworks to understand face mask perceptions and behaviours. future research should also replicate the current results and address our limitations. although face mask perceptions likely differ between eastern and western populations, we did not perform any tests of measurement invariance (van de schoot et al., 2012) . the fmps may not be appropriate for use with eastern populations, and future research should assess this possibility. we also did not assess test-retest reliability, which would provide insights into the stability of face mask perceptions. likewise, we did not explore participant reactions to items via think-aloud methods to identify problematic wording and cognitive burdens 1 (devellis, 2016; howard, 2018; presser & blair, 1994) , and such an assessment would provide insights into the ease (or difficulty) of completing the fmps. all authors declare no conflict of interest. health psychology and the coronavirus (covid-19) global pandemic: a call for research three kinds of psychological determinants for hand-washing behaviour in kenya coronavirus pandemic: tracking the global outbreak. bbc news coronavirus: why is there a us backlash to masks? bbc news demographic and attitudinal determinants of protective behaviours during a pandemic: a review more people say they're wearing masks to protect themselves from covid-19 since march confirmatory factor analysis for applied research an evaluation of amazon's mechanical turk, its rapid rise, and its effective use use of cloth face coverings to help slow the spread of covid-19 covid-19 control in china during mass population movements at new year. the lancet best practices in exploratory factor analysis: four recommendations for getting the most from your analysis scale development: theory and applications misinformation and morality: encountering fake-news headlines makes them seem less unethical to publish and share evaluating the use of exploratory factor analysis in psychological research face masks are in. the atlantic health message framing effects on attitudes, intentions, and behavior: a meta-analytic review confirmatory factor analysis a review of exploratory factor analysis decisions and overview of current practices: what we are doing and how can we improve? experimental pretesting of hand-washing interventions in a natural setting hand hygiene practices in a neonatal intensive care unit: a multimodal intervention and impact on nosocomial infection does health coaching improve healthrelated quality of life and reduce hospital admissions in people with chronic obstructive pulmonary disease? a systematic review and meta-analysis mechanical turk data collection in addiction research: utility, concerns and best practices the behaviour change wheel: a new method for characterising and designing behaviour change interventions false memories for fake news during ireland's abortion referendum an investigation of the effects of a hand washing intervention on health outcomes and school absence using a randomised trial in indian urban communities health psychology: a textbook: a textbook survey pretesting: do different methods produce different results? tapped out or barely tapped? recommendations for how to harness the vast and largely unused potential of the mechanical turk participant pool the importance of coping appraisal in behavioural responses to pandemic flu a checklist for testing measurement invariance a novel coronavirus outbreak of global health concern compliance to health recommendations: a theoretical overview of message framing supporting information the following supporting information may be found in the online edition of the article: 4. i want to prove a point against authority. note when administering scale appendix s1. all datasets for the current submission, but the submission manager would not allow.zip files to be uploaded.appendix s2. complete reporting of studies 1, 2, and 3.appendix s3. original, intermediate, and final face mask perception scale (fmps) items.appendix s4. exploratory factor analysis results. face mask perceptions scale (fmps) please indicate the extent to which you disagree to agree with the following statements regarding face masks, which refers to cloth coverings worn on the face typically intended to prevent the spread of disease and illness. answer each of the following items as if they began with: when i do not wear a face mask in public, it is because. health safety perceptions 1. people should thoroughly wash their hands whenever they go out because of coronavirus. 2. people should stay six feed apart when out in public due to coronavirus. 3. people should limit their trips to the store because of coronavirus. 4. people should stay at home due to coronavirus. 5. people should not touch others (e.g., shake hands) due to coronavirus. 6. people should take extra safety precautions due to coronavirus. 1. it is a good idea to wear a face mask due to coronavirus. 2. it is a good idea to wear a face mask in general. 3. people should wear face masks in public. 4. wearing face masks should be more popular. key: cord-254861-lpzx878m authors: saggese, nicholas p.; rose, adam l.; murtagh, keith; marks, andrew p.; cardo, vito a. title: an interim solution to the decreased availability of respirators against covid-19 date: 2020-04-22 journal: anesth analg doi: 10.1213/ane.0000000000004879 sha: doc_id: 254861 cord_uid: lpzx878m nan to the editor w e read the recent article titled, "utility of substandard facemask options for health care workers during the covid-19 pandemic" by abd-elsayed and karru 1 with great interest. the authors do an excellent job capturing the issue of n95 respirator shortages due to a surge in coronavirus disease 2019 (covid-19) cases and panic use by the public. however, the article emphasizes the importance of facial seal and fit in face masks but they do not provide a solution to this ongoing issue. we would like to shed light on a few more potential alternatives to the n95 that exhibit good facial seal and may be considered under dire circumstances. boston children's hospital has conducted a pilot study on a do-it-yourself reusable respirator. the respirator is comprised of an anesthesia mask, inline ventilator filter, or high-efficiency particulate air (hepa) filter and elastic straps ( figure a) . it has minimal leakage around the mask's edge (if appropriately sized), and breathability was shown to be similar to the n95 respirator but with n100 filtration efficiency (99.97% efficient in filtering viral and bacterial particles). 2 this apparatus can be washed with soap and water or disinfectant when contaminated. the filter should be changed when visibly damaged or difficult to breathe through. 2 our first author applied the mask while simultaneously monitoring pulse oximetry and end-tidal co 2 for 15 minutes. there was no decrease in oxygen saturation, and normal end-tidal co 2 was observed. the mask was comfortable and easy to breathe through. overall, the device was simple to construct and cost-effective. second, the authors mention that surgical masks are "suboptimal, 1 " which is controversial and may not be true. a randomized control study showed that surgical masks offered comparable protection to n95s against viral respiratory infections in the clinical setting. 3 also, a case report from singapore demonstrated 41 health care workers (hcws) who came in contact with covid-19 patients during aerosolizing procedures. the hcws were subsequently tested negative for covid-19. eighty-five percent of the hcws wore surgical masks and 15% wore n95s, showing that surgical masks combined with other recommended precautions were efficacious. 4 however, we do agree that protection in these masks can be optimized with proper seal, as stated by the authors. 1 to better conform a mask to the face, an organization called "fix the mask" designed a "surgical mask brace." all that is needed are 3 rubber bands and a surgical mask. rubber bands are looped together to create a chain. the mask is donned with the middle rubber band over the mask and the lateral rubber bands around the ears to create a better seal ( figure b) . 5 this is also a simple, cost-effective design and is now undergoing quantitative testing by the organization. alternatively, the authors of this letter used 2 tourniquets fashioned together instead of rubber bands to create a better seal ( figure c) . tourniquets are readily available in the hospital system. tourniquets offer an advantage over rubber bands because they are wider, providing more surface area over the edges of the mask. after using this technique and performing a user seal an interim solution to the decreased availability of respirators against covid-19 figure. suggested alternatives to respirator shortages. a, anesthesia mask with inline ventilator filter and head strap. concept adapted from boston children's hospital pilot study. b, rubber band "surgical mask brace" adapted from fix the mask. c, modification of the "surgical mask brace" with tourniquets. www.anesthesia-analgesia.org letters to the editor check, we noticed no evident air leakage around the mask margins during inhalation and exhalation. we would recommend that this be used with an american society for testing and materials (astm) level 3 surgical mask with eye protection and reserved for situations that do not involve aerosol-generating procedures. in conclusion, there is no high-level evidence showing that either of these devices are safe at this time, and none are approved by the national institute for occupational safety and health (niosh) or the food and drug administration (fda). however, these strategies may be good alternatives during crisis capacity. powered air-purifying respiratory hood systems, although expensive, can also be an alternative, especially when performing procedures with high aerosolization. furthermore, it is important to remember that other personal protective equipment (ppe) must be used in addition to the respirator or facemask to protect against severe acute respiratory syndrome coronavirus 2 (sars-cov-2), such as goggles, face shield, gown, and gloves. the user must also correctly don and doff the ppe and hand wash for at least 20 seconds to help prevent the spread of sars-cov-2. solutions to the shortage of n95 respirators are crucial for protecting health care workers from contracting the virus and becoming a vector of transmission to others. utility of substandard face mask options for health care workers during the covid-19 pandemic covid-19: our response to the n95 shortage: making your own reusable elastomeric respirator. boston children's hospital respect investigators. n95 respirators vs medical masks for preventing influenza among health care personnel: a randomized clinical trial covid-19 and the risk to health care workers: a case report surgical mask brace: a solution designed by mechanical engineers at fix the mask key: cord-301723-zz24wmv7 authors: jotz, geraldo pereira; bittencourt, aline gomes title: why we need to use and which mask types are effective against the novel coronavirus (covid-19)? date: 2020-06-23 journal: int arch otorhinolaryngol doi: 10.1055/s-0040-1713588 sha: doc_id: 301723 cord_uid: zz24wmv7 nan transmission of coronavirus generally occurs through respiratory droplets and contact. current evidence suggests that sars-cov-2 may remain viable for hours to days on surfaces made from a variety of materials. in the house, care must be taken for open outside doors and windows and the use of ventilating fans to increase air circulation. we recommend using masks to self-protect and to protect others around, during the covid-19 pandemic, mainly in inside closed spaces as buildings and malls. also, maintaining distance between each person helps us to control the transmission of coronavirus. there is much to learn about the novel coronavirus (sars-cov-2) that causes coronavirus disease 2019 . based on what is currently known about the virus and about similar coronaviruses that cause sars and mers, spread from person-to-person happens most frequently among close contacts (within about 6 feet). this type of transmission occurs via respiratory droplets, but disease transmission via infectious aerosols is currently uncertain. 1, 2 respiratory droplets are generated when an infected person coughs or sneezes. any person who is in close contact (within 1 meter) with someone who has respiratory symptoms (coughing, sneezing) is at risk of being exposed to potentially infective respiratory droplets. droplets may also land on surfaces where the virus could remain viable; thus, the immediate environment of an infected individual can serve as a source of transmission (contact transmission). 3 the incubation period for covid-19, which is the time between exposure to the virus and symptom onset, is on average 5-6 days, but can be as long as 14 days. during this period, also known as the "presymptomatic" period, some infected persons can be contagious and therefore transmit the virus to others. [4] [5] [6] [7] [8] [9] the united states national institute for occupational safety and health (niosh) has standardized n95 face masks (►figure 1). the "n" stands for "not resistant to oil," while "95" represents its minimum 95 percent filter capacity for catching viruses as small as 0.3 microns. the face filtering piece (ffp) face masks are a rage in europe, divided into three categories: ffp1, ffp2 and ffp3. according to the european standards, each type can filter 80, 94 and 99.95 particles down to 0.3 microns. they are equivalent to n95 in europe. 1, 2 homemade masks need to be fabric with 100% cotton (►figure 2), because it is most effective. 10 in the hospital, in low-risk areas to covid-19, the surgical masks is a good option (►figure 3). masks can be made of different materials and designs which influence on their filtering capability. masks can also be used for source control, which refers to blocking droplets ejected by the wearer. it is hypothesized that if everyone is wearing masks to decrease the chance that they themselves are unknowingly infecting someone, everyone ends up being more protected. 11 there are, however, large gaps in the scientific literature as to the effectiveness of facemasks in reducing community transmission of covid-19. although there is experimental evidence that facemasks are capable of retaining infectious droplets and potentially reduce transmission, as well as reports of transmission reduction by using facemasks, there is no evidence that such reduction occurs in community environments. epidemiological studies are needed to eluci-date this issue. they must be conducted following consistent protocols, with sufficient sample sizes, as well as respecting research ethics principles. 12 the use of medical masks in the city, nonetheless, may create a false sense of security, with neglect of other essential measures, such as hand hygiene practices and physical distancing, and may lead to touching the face under the masks and under the eyes. there is also the issue of difficulting access to the medical masks to supply the health workers. the use of nonmedical masks made of other materials (e.g., cotton fabric) in the community has not been well evaluated. there is no current evidence to make a recommendation for or against their use in this setting. 13 unfortunately, macintyre et al evaluated the use of cloth masks in a health care facility and found that health care workers using cotton cloth masks were at increased risk of infection compared with those who wore medical masks. 14 in the interim, when advising the use of nonmedical masks, the following features should be taken into consideration: numbers of layers of fabric/tissue, breathability of the material used, water repellence/hydrophobic qualities, shape of mask and fit of mask. 13 for any type of mask, appropriate use and disposal are essential to ensure that they are effective and to avoid any increase in transmission. health care workers should: • wear a medical mask when entering a room where patients with suspected or confirmed covid-19 are admitted. • use a particulate respirator at least as protective as a us national institute for occupational safety and healthcertified n95, european union standard ffp2, or equivalent, when performing or working in settings where aerosol-generating procedures, such as tracheal intubation, non-invasive ventilation, tracheotomy, cardiopulmonary resuscitation, manual ventilation before intubation, and bronchoscopy are performed. why we need to use and which mask types are effective jotz, bittencourt • place the mask carefully, ensuring it covers the mouth and nose, and tie it securely to minimize any gaps between the face and the mask. • avoid touching the mask while wearing it. • remove the mask using the appropriate technique: do not touch the front of the mask but untie it from behind. • after removal or whenever a used mask is inadvertently touched, clean hands using an alcohol-based hand rub or soap and water if hands are visibly dirty. • replace masks as soon as they become damp with a new clean, dry mask. • do not re-use single-use masks. • discard single-use masks after each use and dispose of them immediately upon removal. 13 kowalski et al published here the "effect of the covid-19 pandemic on the activity of physicians working in the areas of head and neck surgery and otorhinolaryngology" and they demonstrated a direct impact of the covid-19 pandemic on the clinical practice of specialties related to the treatment of patients with diseases of the head and neck region already in the beginning of the management of the illness in brazil. 15 in the first editorial, itzhak brook discusses about prevention of covid-19 infection in neck breathers, including laryngectomees, highlighting the hygiene care that these patients must have in order to prevent contamination with this disease. we can observe in this journal some articles demonstrating the opinion and experience of the authors against covid-19. finally, regardless of the scientific evidence, we recommend using any kind of masks to self-protect and to protect others, during the pandemic, mainly in public spaces, especially in closed ones. keeping appropriate distance between each person helps us controlling the transmission of coronavirus disease. hand hygiene is an uncontroversial point: it should always be done with 70% alcohol or washing hands with soap. remember: my mask may protect you; your mask may protect us! united states national institute for occupational safety and health (niosh) total respiratory water, sanitation, hygiene and waste management for covid-19 a familialclusterofinfectionassociatedwiththe 2019 novel coronavirus indicatingpossibleperson-topersontransmissionduringtheincubationperiod a family cluster of sars-cov-2 infection involving 11 patients in nanjing, china asymptomatic cases in a family cluster with sars-cov-2 infection potential presymptomatic transmission of sars-cov-2 presymptomatic transmission of sars-cov-2 -singapore public health -seattle & king county; cdc covid-19 investigation team. asymptomatic and presymptomatic sars-cov-2 infections in residents of a long-term care skilled nursing facility -king county, washington face masks against covid-19: an evidence review use of facemasks to limit covid-19 transmission advice on the use of masks in the context of covid-19. interim guidance. world health organization a cluster randomised trial of cloth masks compared with medical masks in healthcare workers effect of the covid-19 pandemic on the activity of physicians working in the areas of head and neck surgery and otorhinolaryngology the authors have no conflict of interests to declare. key: cord-262920-yjsl6kck authors: schilling, katherine; gentner, drew r.; wilen, lawrence; medina, antonio; buehler, colby; perez-lorenzo, luis j.; pollitt, krystal j. godri; bergemann, reza; bernardo, nick; peccia, jordan; wilczynski, vincent; lattanza, lisa title: an accessible method for screening aerosol filtration identifies poor-performing commercial masks and respirators date: 2020-08-06 journal: j expo sci environ epidemiol doi: 10.1038/s41370-020-0258-7 sha: doc_id: 262920 cord_uid: yjsl6kck background: the covid-19 pandemic has presented an acute shortage of regulation-tested masks. many of the alternatives available to hospitals have not been certified, leaving uncertainty about their ability to properly protect healthcare workers from sars-cov-2 transmission. objective: for situations where regulatory methods are not accessible, we present experimental methods to evaluate mask filtration and breathability quickly via cost-effective approaches (e.g., ~$2000 usd) that could be replicated in communities of need without extensive infrastructure. we demonstrate the need for screening by evaluating an existing diverse inventory of masks/respirators from a local hospital. methods: two experimental approaches are presented to examine both aerosol filtration and flow impedance (i.e., breathability). for one of the approaches (“quick assessment”), screening for appropriate filtration could be performed under 10 min per mask, on average. mask fit tests were conducted in tandem but are not the focus of this study. results: tests conducted of 47 nonregulation masks reveal variable performance. a number of commercially available masks in hospital inventories perform similarly to n95 masks for aerosol filtration of 0.2 μm and above, but there is a range of masks with relatively lower filtration efficiencies (e.g., <90%) and a subset with poorer filtration (e.g., <70%). all masks functioned acceptably for breathability, and impedance was not correlated with filtration efficiency. significance: with simplified tests, organizations with mask/respirator shortages and uncertain inventories can make informed decisions about use and procurement. the covid-19 pandemic has presented an acute need for masks and respirators to be used by healthcare workers on the frontlines and growing needs for essential workers and the public to wear masks in affected areas. the rapid shortage of medical n95 respirators or other certified masks creates an urgent demand for suitable alternatives. this has led to an influx of a wide variety of masks that have not been tested by the national institute for occupational health and safety (niosh) into the medical community and the public with little to no assurance of performance. hospitals are often faced with deciding which other type of masks (e.g., kn95) to consider buying when the traditional supplies of tested masks are no longer available for purchase [1] . many claim to have filtration characteristics equivalent to traditional n95 masks but have not undergone the same testing for n95 masks in the u.s. there is also a large influx of counterfeit masks into the market due to mask shortages during the pandemic [2] [3] [4] . many hospitals are receiving donations from a well-intentioned public that range from non-medical respirators and surgical masks to handsewn facemasks. most of these donated items have not been confirmed by niosh to provide comparable protection from the transmission of sars-cov-2 to a standard medical n95 mask [5] . as such, the decision to use them without testing information poses significant risk to healthcare and other essential workers. currently the certification capacity of niosh is too limited to accommodate the high demand for testing of masks and allow for timely decision making on purchases or the use of donated masks during this critical nationwide shortage. the pandemic and need for accessible mask testing methods are also likely to reach regions with decreased capacity for mask testing (e.g., developing nations). in the absence of available regulation testing facilities or the specific and costly equipment to replicate regulatory methods, we present a screening method to quickly evaluate masks using an accessible approach that could be replicated in communities lacking the infrastructure necessary for regulation tests. these methods are not intended to replace regulation approaches, but to provide alternatives to nonexperts in times of need to screen and prioritize the use or acquisition of masks/respirators and to complement the existing body of literature on mask and alternative mask testing (e.g., [6] ). as such, readily accessible equipment has been used to maintain accessibility for a greater diversity of communities. there are several key considerations for mask performance: (a) filtration, (b) flow impedance (i.e., breathability), (c) fit, and (d) continued performance under environmental conditions (e.g., wetting). the assessments performed in this document focuses on the first two aspects. in tandem with this study, masks were also evaluated for fit using a commercial leak detection apparatus, conducted by members of yale university's office of environmental health and safety, to characterize and reduce penetration of aerosols at the edges of the masks [7] . in order for a mask to be deemed appropriate for clinical use in a covid-19 patient setting it must pass the filtration and breathability tests as well as a fit test. niosh, fda, and other federal methods for medical testing masks and respirators have differences in test aerosols (e.g., nacl solution vs. latex spheres) and measurement methods [8] [9] [10] [11] [12] (e.g., offline gravimetric vs. online counters) as summarized and compared in detail in rengasamy et al. [5] . respiratory droplets and aerosols are emitted from humans during coughing, sneezing, breathing, talking, or intubation that could contain viruses, including sars-cov-2. exhaled aerosol/droplets may span from the nominal size of sars-cov-2 (~120 nm) up to 10 μm or larger [13] [14] [15] [16] [17] [18] [19] , and can decrease in size with evaporation of condensed water [20] [21] [22] . the world health organization identifies two main categories of particles as key factors in coronavirus transmission: "respiratory droplets" (>5-10 μm in diameter) and "droplet nuclei" (aerosols <5 μm in diameter) [23] ; the latter of which includes the typical test aerosol diameters for u.s. agencies involved in mask certification (0.075-5 μm) [5] . the airborne lifetime of these humangenerated aerosol/droplets are size-dependent, reaching upwards of several hours for aerosols in the 0.1-1-μm size range [24, 25] and suspended sars-cov-2 can survive airborne for over 1 h at moderate humidities (rh = 65%) [26] . aerosols in that size range containing sars-cov-2 and surface contamination have been observed in staff areas of hospitals away from patients [18, 19, 27] . therefore, it is important to consider a wide range of droplet and aerosol sizes for mask filtration efficacy. our overall goals are (a) to disseminate simplified testing setups that can be used in comparative evaluations of nonregulation or alternative masks against regulation masks and (b) present results from our survey of a set of commercially available masks representative of those entering u.s. hospital networks. testing specifically focuses on flow impedance and aerosol filtration, both of which are evaluated in the traditional niosh mask certification process. this study utilizes more readily available equipment and resources to conduct similar assessments in an experimentally comparable procedure, but does not attempt to replicate or claim niosh approval. its purpose is to allow health professionals to make informed decisions on the most appropriate masks to use when trusted ppe is not available. with the intent of evaluating filtration efficiency without purporting to replicate niosh equivalency, the methods designed in this study are aimed at testing masks with relevant, reproducible aerosol distributions at face velocities appropriate for human respiration. to evaluate performance, we utilize a combustion-generated polydisperse aerosol and measure removal efficiencies for several size ranges. using readily available aerosol instrumentation, size-resolved aerosol number, and mass concentrations are measured upstream and downstream of a test mask material. the measured aerosol removal efficiencies of untested respirators and masks are then compared with those of a production lot of regulatory n95 masks to establish performance criteria. the combustion-generated aerosol is produced via incense inside a sealed 0.25-m 3 acrylic box that serves as a contained aerosol source (fig. 1) . to achieve the desired aerosol concentrations (e.g., 50-100 μg m −3 ), a stick of burning incense is inserted briefly via a small port in the source chamber. as the incense smolders, it generates humidity and organic compounds, which condense to create a polydisperse aerosol that comprises a wide range of sizes, across the range of concern [28] [29] [30] , including both aerosol and droplet emissions from humans (e.g., fig. s14 ). sufficient time is allowed for the aerosol population to become well-mixed and stable in the chamber, using a real-time sensor to track size-resolved concentrations. the aerosols produced in the source chamber may be too highly concentrated depending on the measurement instrumentation used (e.g., the airnet aerosol particle counter used in this study, described in detail below). thus, the flow from the chamber is diluted using pressurized house air that is humidified via a bubbler and regulated by a mass flow controller (alicat) to control the rate of dilution, though other flow control options are feasible. this diluted aerosol stream is used to test the mask material, which is a disk cut from a full mask using a die for consistency (fig. s3 ). the disk is housed in a filter holder, in this case a custom aluminum holder with an exposed filter area of 30.5 mm in diameter ( fig. s1 ), but commercially available filter holders should suffice, and disks may be cut by hand. grounded metal tubing was used leading to the filter holder and the detectors to reduce losses of charged particles. however, charge neutralization of aerosols is not employed in this setup, and aerosol charge may play a role in filtration for some masks. this test method, as with standard test methods, mimics the face velocity (equal to the volume flow rate/surface area) of aerosol deposition on a mask during typical human inspiratory breathing flow rates of 65-220 lpm [5] corresponding to face velocities of~6.4-21.7 cm/s for masks ranging in area from 130-225 cm 2 (e.g., table s1 ). these face velocities are achieved with our 30.5-mm disk sample using volume flow rates from 2.8 to 9.5 lpm and most of the testing focused on 4.5 lpm corresponding to 10 cm/s. two real-time detectors were used in the study, an airnet (model 210, particle measurement systems) and a search multipollutant monitor equipped with a plantower a003 sensor from the "solutions for energy, air, climate, and health" center at yale-johns hopkins [31] . other detectors may be used, provided the careful considerations detailed in this paper are followed. the airnet detector measures the number concentration of aerosols in size bins of 0.2-0.3, 0.3-0.5, 0.5-1, and >1 μm. the search monitor measures mass and number concentrations of aerosols in size bins 0.3-0.5, 0.5-1, 1-2.5, 2.5-5, and 2.5-10 μm with a lower sensitivity compared with the airnet [31] . upstream of the filter, the search detector is used to monitor and maintain reproducible and stable test aerosol concentrations in the source chamber. downstream of the filter, aerosol concentrations were measured with both the airnet and a second search instrument for redundancy. primary experimental setup for aerosol filtration assessmen. "aerosol detectors" refer to search monitors and the "aerosol particle counter" is the airnet instrument (in orange). however, the analysis was done primarily with the airnet to demonstrate that only a single reliable detector is critical for such an assessment. downstream concentrations of the aerosols are checked regularly without a mask in place to confirm that they match those expected based on the source chamber concentrations and dilution rates. periodic downstream measurements with the second search monitor were done to cross-check the observed filtration efficiencies, dilution rates, and aerosol transmission. downstream flow rates are controlled to change the face velocity used to test the filter material and provide the suction from the source chamber. the airnet is controlled by a built-in orifice (2.8 lpm) and a second mass flow controller (alicat) is used to pull the remainder of the flow through the system (e.g., 1.7 splm for a 10-cm/s face velocity), where vacuum is generated using two separate vacuum pumps. at any given face velocity, changing the dilution flow rate adjusts the test aerosol concentration. a more detailed description of the flow rates shown in fig. 1 can be found in section s1. the filtration efficiency for any of the size-resolved bins is defined as and for the purposes of this study was further substantiated by measuring across a series of dilution factors (with and without mask material in place) to gain multi-point measurements across a range of test aerosol concentrations at a given face velocity (see section s4 and fig. s6 ). information related to the cost of equipment as well as criteria for optimizing concentration levels are described in section s4. flow impedance assessment of the mask materials is conducted to gauge the potential breathability of a given mask. proper use of a mask mandates that the mask creates a good seal around one's face. this forces intake air to be limited to what can pass easily through the mask, which means that enough pressure is needed from breathing to drive the air flow. regardless of filtration capability, a mask with low breathability still poses a risk to the wearer due to the difficulty of breathing normally. the niosh procedure takes into account the effect of mask area on the maximum pressure allowed for a specified volume flow (the ratio defining an "extrinsic impedance") by using a full mask for the test. here, we employed a straightforward apparatus to measure the intrinsic impedance of mask material by measuring the pressure drop (in mm h 2 o) across a 40-mm disk of mask filter material as a function of the face velocity (calculated from the volume flow rate and the 40-mm disk area of 12.6 cm 2 ). the sample disk diameter here was determined by the size of a commercially available plastic filter holder, which was used for its easy availability, low cost, good sealing properties, and dual applicability in the rapid screening setup described below. the slope of the linear fit to these points is the intrinsic impedance of the material in units of mm h 2 o/(cm/s). the experimental apparatus (fig. 2) is from petculescu and wilen [32] and further described in section s3. to get a value for the extrinsic impedance for a given mask, we divide the intrinsic impedance by the mask area, either measured directly or approximated based on mask type and geometry. it should be noted that the instrumentation used here could easily be replaced with low-cost commercial rotameters and manometers to measure flow and pressure. we also evaluated a rapid screening approach with the understanding that initial screening of large inventories is necessary to determine which masks/respirators warrant further testing and also that some communities and facilities may be constrained in terms of available instrumentation for aerosol measurement and flow control. this furthersimplified setup (fig. 3) relies on a filter holder (same as that used for impedance) and a single airnet 210 detector, with a fixed volume flow rate of 2.8 lpm, and configured to read out count data through its analog outputs. the face velocity through the filter was modified with a pair of lasercut ring inserts to test at~13 cm/s (see images in fig. s2 ). with this setup, adjusting the filter area to achieve the appropriate face velocity is critical, otherwise slow face velocities atypical of breathing conditions might skew results and give false positive results. an example procedure is shown in fig. 3b where two mask materials are inserted and removed to assess against upstream concentrations without the mask in place. if ambient aerosol concentrations are sufficiently stable in the room where testing is occurring, ambient air can serve as the aerosol "source," as was the case for this evaluation approach. data and results of this testing are described in supplemental information. although a second airnet 210 detector was used here, which allowed for a direct comparison to the full technique, any instrument that provides size-resolved aerosol concentration measurements could possibly work for this approach (see "considerations" section). aerosol filtration efficiency while the instrumentation package measured an aerosol size range of 0.2-10 μm, aerosol filtration analysis focused on the range of 0.2-1 μm for these reasons: this range is closer to sizes of interest in the niosh/fda methods; it targets the most challenging aerosols to filter (0.2-0.3 μm); and this particle diameter range is where mask performance differentiated most for the masks and instruments used in this study. a set of face velocities were examined to span typical inspiratory flow rates and typical test procedures [5] , but primarily focused on 10 cm/s for inventory screening (fig. 4) as discussed earlier. prior to recommending that a mask be used in service, multiple trials of the same mask type across a set of individual masks from a delivered lot are conducted to ensure consistent results in the data. results from repeated tests of a single mask type (fig. 4a inset) show variability within mask lots, which were larger for a poorly performing mask type (#15), compared with the six n95 tests that ranged 98-99% at 10 cm/s. repeat tests of the same exact mask sample on different days resulted in minimal variance and demonstrated consistency in the experimental setup. specifically, the error was 0.7 ± 0.6% in absolute deviation between tests (i.e., eff. test t − eff. test t + 1 ) for the 0.2-0.3 μm size bin. an accessible method for screening aerosol filtration identifies poor-performing commercial masks and. . . fig. 4 , tests conducted on 47 nonregulation masks using this setup reveal that a number of commercially available masks perform similarly to the regulation n95 mask's aerosol filtration for 0.2 μm and above. then, there are a range of masks with relatively weaker filtration efficiencies (i.e., 80-95% for aerosols >0.2 μm). yet, a subset of commercially available masks have poor performance (i.e., <80%) relative to n95 or similar masks. it is important to note that the masks tested here focus on nonregulated, commercially available masks, most of which are purported to be efficacious for aerosol filtration at, or near, that of an n95 respirator (table s1 ). the performance of the ten commercial (traditional) surgical-style masks tested varied widely 22-95% (see table s1 ) with an average of 72 ± 19%. while materials for homemade masks could be tested with this setup, it was generally outside the scope of this ppe survey (the one homemade mask and one commercially made alternative mask donated to the hospital included in this study performed very poorly, i.e., 14%). there was significant disparity in the performance of masks purported to be n95 equivalent (i.e., kn95) or even labeled as "n95," spanning efficiencies of 38% (mask #22) to 99% (see table s1 for values). some kn95 masks performed consistently well, but others did not. for example, mask #1 performed consistently well while mask #15 had significant variance (fig. 4a inset) with two masks from #15's lot performing at or near 95% filtration and others reaching as low as 78-82%. these results raise the importance of both testing a significant sample size of masks from any received lots and the value of validation independent of vendor assurances. mask filtration efficiencies expectedly varied as a function of aerosol size. given the higher efficiency of inertial impaction for larger aerosols with more mass and momentum, the masks generally performed better for larger aerosols (fig. 5) . while mask filtration performance can be similarly differentiated, absolute efficiencies are greater when considering all aerosols (i.e., >0.2 μm) than solely aerosols of 0.2-0.3 μm (fig. 4, s7) . consistent with aerosol filtration theory, the removal of smaller aerosols is better at slower face velocities (fig. 5) given the dependence of "diffusive" losses (i.e., brownian motion to the filter fibers) on flow rates (i.e., timescales for air transport through the filters). this aerosol size dependence is important since sars-cov-2-containing aerosols are distributed across a wide size range and aerosols with diameters of 0.1-0.5 μm can remain airborne longer [18, 19, 24, 25] . with regard to testing protocols, fig. 5 demonstrates clearly how flow rate (i.e., face velocity) influences filtration efficiencies. using the technique described above, the intrinsic impedance was measured and tabulated for the mask inventory table s1 and not rankordered performance. (fig. 6) . the extrinsic impedance was also examined for some of the masks for which areas had been measured independently using an image analysis technique (see supplementary information) . all the extrinsic impedances (table s1 ) are below the niosh threshold of 0.0247-mm h 2 o/(cm 3 /s) and even for masks for which areas were not measured, based on their intrinsic impedances, their areas would have to be improbably small to exceed the niosh threshold for breathability [33] . for simplicity in comparison, we also present an "intrinsic breathability index" which is defined as the ratio of the intrinsic impedance for a mask compared with a standard n95 mask. in section s4, we discuss various implications for the filtration, impedance, and face sealing relating to the mask area. presented with a large array of masks to test, efforts to include area measurement were streamlined. some masks were excluded from consideration early, based on poor filtration of the mask material. masks found to be made of material with the highest measured filtration efficiencies were prioritized for more extensive examination. among these, higher priority 6 measured impedance values shown against breathability index (i.e., n95 intrinsic impedance/intrinsic impedance) where all masks are within the niosh threshold for impedance. points are colored based on filtration efficiency, and no correlation was observed between impedance and filtration efficiency (see fig. s7a ). for use in hospitals was then given to masks with the smallest extrinsic impedance, also taking face sealing into account. to evaluate the rapid screening setup (fig. 3) , we tested this approach for half of the masks tested in the fig. 1 setup. the rapid screening approach's filtration efficiencies were consistent with those of the primary setup and effective for rank-ordering masks (fig. 7) . the differences in filtration efficiencies in fig. 7 are not random, but well-correlated when fit to a power function (fig. s13) , potentially owing to the combined effects of differences in in-room aerosol size distributions and face velocities. based on these results, we conclude that this method has efficacy as a rapid screening method, where 26 masks can be preliminarily screened in 80 min (fig. s11) . however, frequent cross-comparison to n95 benchmark masks is essential between operational sessions since variations in-room aerosol composition can affect results. more details about correlations between the two techniques and calibration procedures are described in the section s5. as defined above, these methods are not intended to replace regulation approaches, but to provide accessible screening approaches where necessary for emergency evaluation of incoming masks/respirators. the goal is to allow users to rank-order masks in comparison with n95 "benchmark" masks (in their possession) to enable more informed decisions and prioritization of ppe for use. mask fit and durability must also be assessed. as mentioned earlier, a commercial leak detection apparatus is used to characterize penetration of aerosols at the edges of the masks, and these results are also factored into the decision/prioritization process. to facilitate replicate setups, we outline a selection of considerations, potential issues, and best practices with additional detail in section s4. given that all masks here performed sufficiently in terms of breathability (i.e., flow impedance) compared with the niosh threshold, our discussion in the main text is focused on filtration test considerations, where the tested masks performed more variably. the primary testing setup described in fig. 1 is not the sole feasible configuration, as is readily demonstrated with the rapid screening approach (fig. 3) . however, the primary setup does offer certain advantages that should be considered by future users: (a) consistent and stable spherical polydisperse aerosol populations that span the range of target aerosol sizes; (b) repeatable flow rates delivering the test aerosol mixture at atmospheric pressure and representative face velocities (e.g., 10 cm/s) that allow for discrimination of mask performance; (c) leak-checked systems, especially in the filter holder where bulky mask materials increase the potential for leaks (note: flow balance can be confirmed using multiple flow controllers; fig. 1 ); (d) frequent confirmation of test aerosol concentrations via downstream instruments (with no filter in place) checked at all flow and dilution conditions used, with redundant instruments up-and downstream (if available); (e) regular checks of filtration efficiency against n95 "benchmark" masks; and (f) metal tubing and filter holder (all grounded) are best practice to avoid electrostatic aerosol losses, but nonmetallic components may work with frequent comparisons to "blank" measurements without a filter. similarly, digital mass flow controllers are used in this study, but sufficiently precise rotameters or flow constrictions may prove effective substitutes. aerosol instrumentation is a critical consideration, and differences between available instrumentation are considerable across the global scientific and hospital community. as such, this study is carried out using a total aerosol instrumentation cost of under $2000 usd, and found high utility in the airnet aerosol particle counter used for clean-room monitoring. while multiple monitors are included in fig. 1 and used in cross-checks, the conclusions were derived primarily with a single detector. the key elements are that (a) the aerosol concentrations used for testing must be adjusted based on the sensitivity of the instrumentation such that the signalto-noise ratio of the measurements are sufficiently high to determine the filtration efficiency with some precision (i.e., accurately measure changes between upstream and downstream concentrations) while also avoiding exceeding upper limits of detection or linearity; (b) real-time instruments allow fig. 7 comparison of rapid screening setup (fig. 3 ) compared with primary setup (fig. 1) showing equivalent ranking of mask/respirator performance. filtration efficiencies are shown for 0.2-0.3 μm aerosols. tested face velocities were not the same between the two approaches. for faster screening of inventories and prioritization of masks; (c) size-resolved measurements are better suited to discern differences in mask performance and more closely match aerosols in niosh/fda tests since larger, easily filtered aerosols are major contributors to the mass distributions of combustion or in-room aerosols; and (d) it is beneficial to use aerosols that span the range of sizes of potentially viruscontaining aerosols (>0.2 μm in this setup), but smaller aerosols in this range are more challenging to filter at the typical face velocities and are preferentially tested in the niosh and fda procedures. yet, total aerosol number concentration measurements without size-resolution that include sizes below 0.1 μm may skew efficiency results by incorporating filtration of combustion or in-room aerosols dominated by these smaller sizes, which are easily collected via brownian motion, and are outside the size range of interest for sars-cov-2 aerosol transmission. while aerosol number concentrations were used to determine filtration efficiencies in this study, size-resolved mass concentrations could be used with appropriate test aerosol concentrations and instrument sensitivities. regardless of the testing setup, it is essential to screen a sufficient number of masks/respirators to constrain lot-to-lot variability (e.g., fig. 4a inset) for masks that might be used in service. the niosh protocol requires 20 of 20 masks to exceed the 95% filtration efficiency. the exact number of randomly selected masks to be tested by an organization may depend on the supply of masks in a given lot and their likely application, but based on our results there are clear indicators of mask-to-mask variance within a sample size of five masks (fig. 4a inset) that could be used to inform further examinations of variance. given that aerosol filtration efficiency varies with aerosol size, larger aerosols will be removed more effectively (i.e., 1-5 μm), but smaller aerosols (e.g., 0.2-0.5 μm) may provide more ability to discern between mask/respirator performance. similarly, faster flow rates may provide more potential to discern between masks, yet care should be taken to not extend velocities outside the range of the typical conditions during breathing (coughing, speaking, etc.) that are examined in regulation testing (e.g., 3-14 cm/s) [5] . for a given flow rate, differences in face velocity with a full mask, compared with the subsections tested here, will vary with mask area, such that a larger surface area mask will have lower face velocities while in-use. yet changes in filtration efficiencies for well-performing masks will be minor (e.g., with a decrease from 10 to 7.5 cm/s; fig. 5a ) and the face velocity can be adjusted to account for the mask area where necessary for verification. the methods presented here rely upon regular comparisons to niosh n95 benchmark masks, as absolute filtration efficiencies will vary with changes in flow rates and aerosol sizes measured (e.g., fig. 5 ). similar aerosol concentrations and consistent flow conditions between masks must be maintained to minimize system variance that could affect data interpretation. validation of a system should include testing a range of materials expected to have both excellent and poor filtration efficiencies. finally, this approach does not convey the equivalent of an n95 certification, and this publication does not include a full comparison to niosh results other than the comparison with available n95-compliant masks. sourcing personal protective equipment during the covid-19 pandemic global risk to the community and clinical setting: flocking of fake masks and protective gears during the covid-19 pandemic availability of covid-19 related products on tor darknet markets. statistical bulletin no. 24. canberra: australian institute of criminology counterfeit filtering facepiece respirators are posing an additional risk to healthcare workers during covid-19 pandemic a comparison of facemask and respirator filtration test methods simple respiratory protectionevaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles filtering out confusion: frequently asked questions about respiratory protection, fit testing revision 2.0. determination of particulate filter efficiency level for n95 series filters against solid particulates for non-powered, airpurifying respirators standard testing procedure (stp) surgical masks-premarket notification guidance for industry and fda staff. fda standard test method for determining the initial efficiency of materials used in medical face masks to penetration by particulates using latex spheres standard test method for evaluating the bacterial filtration efficiency (bfe) of medical face mask materials, using a biological aerosol of staphylococcus aereus standard specification for performance of materials used in medical face masks quantity and size distribution of coughgenerated aerosol particles produced by influenza patients during and after illness influenza virus aerosols in human exhaled breath: particle size, culturability, and effect of surgical masks size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities the size distribution of droplets in the exhaled breath of healthy human subjects exhaled droplets due to talking and coughing aerodynamic characteristics and rna concentration of sars-cov-2 aerosol in wuhan hospitals during covid-19 outbreak detection of air and surface contamination by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) in hospital rooms of infected patients interaction of aerosol particles composed of protein and salts with water vapor: hygroscopic growth and microstructural rearrangement dynamics of airborne influenza a viruses indoors and dependence on humidity ultrastructural characterization of sars coronavirus world health organization. modes of transmission of virus causing covid-19: implications for ipc precaution recommendations. scientific brief. world health organization indoor particle dynamics modeling indoor particle deposition from turbulent flow onto smooth surfaces aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 transmission potential of sars-cov-2 in viral shedding observed at the university of nebraska medical center characterization of emissions from burning incense chemical composition of fine particles from incense burning in a large environmental chamber incense smoke: clinical, structural and molecular effects on airway disease field and laboratory evaluations of the low-cost plantower particulate matter sensor oscillatory flow in jet pumps: nonlinear effects and minor losses niosh procedure no. teb-apr-stp-0007. determination of inhalation resistance test, air purifying respirators standard testing procedure (stp) conflict of interest drg has externally funded projects on low-cost air quality monitoring technology (epa, hkf technology), which yale has licensed to hkf technology. key: cord-283555-pgel6i3y authors: chan, tak kwong title: universal masking for covid-19: evidence, ethics and recommendations date: 2020-05-26 journal: bmj glob health doi: 10.1136/bmjgh-2020-002819 sha: doc_id: 283555 cord_uid: pgel6i3y nan ► policy makers must rely on best available evidence rather than awaiting strongest evidence when devising urgent policies that can potentially save human lives. ► there is no shortage of mechanistic evidence and observational studies that affirmed the benefits of wearing a face mask in the community, which should drive urgent public health policy while we await the results of further research. ► there is no valid scientific evidence to support the assertion that the use of a face mask in the community may impose a higher risk of infection on the ground of improper use or false sense of security. ► rationing offers no moral ground to ignore the evidence about the benefits for the users of lower priorities. ► the proper approach to addressing shortage is to formulate stratified recommendations that take full account of the benefits of using face masks in the community and provide viable solutions at different scenarios (see table 3 in the main text). ► i urge the who and policy makers worldwide to consider my stratified recommendations, or adopting measures to a similar effect, particularly as the authorities are contemplating relaxation of other aggressive measures such as border closure, lockdown and social distancing. this commentary echoes the plea from greenhalgh et al to encourage people to wear a disposable surgical mask (face mask) in the community. 1 there is limited clinical evidence that wearing a disposable face mask, enhancing hand hygiene practice or social distancing can reduce transmission of respiratory viral infections in the community, 2 3 although there is mechanistic basis for these measures to work. 4 5 for covid-19, hand hygiene and social distancing are widely recommended, while universal use of face masks in the community is not widely recommended, especially in some western countries. [6] [7] [8] [9] some doubted the effectiveness of wearing a face mask in the community. 10 some argued it may foster a false sense of security. 10 11 some said face masks should be reserved for healthcare workers. 7 inconsistent messages from the experts and policy makers about the rationale for the recommendation has led to confusion in the community. i aim to provide further clarification of the evidence and ethics on this issue (which can provide grounds alternative and/or supplementary to the precautionary principle applied by greenhalgh et al) and make a plea to the world health organisation (who) and policy makers to reformulate current recommendations with a view to enhancing the practice of wearing a face mask in the community. current best available evidence should guide urgent policy while public health decisions should be evidence-based, drawing on randomised controlled trials (rct) as an important source of information, the methodological challenges of evaluating large-scale public health interventions need to be recognised. 12 when there is logistic difficulty in conducting an rct, evidence from other data sources can provide valid support for an urgent public health action. 13 the mechanistic effects of handwashing and wearing a face mask have been demonstrated, thus offering some scientific basis for their benefits in terms of disease control. 4 5 a recently published article shows turbulent gas cloud can prolong the life of pathogenbearing droplets and allow them to travel a longer distance. the turbulent gas cloud dynamics should offer further scientific basis to recommend the use of face masks for source control and protection of the wearer. 14 healthcare workers are recommended to wear a face mask as part of droplet precautions, which may prevent them from splashes bmj global health of respiratory droplets from sneezing, coughing or talking patients. some experts suggested that while there is a perception that wearing a face mask may help, there is little evidence of any benefit outside the clinical setting. 15 in a recent meta-analysis, six rcts were identified reporting the effect of wearing a face mask with enhanced hand hygiene in reducing laboratory-confirmed influenza in the community. 2 although none of them supported a significant protective effect, 2 all the authors acknowledged that their studies may have underestimated the effect of the intervention (see table 1 for their limitations). [16] [17] [18] [19] [20] [21] their results also may not be generalisable to the universal use of face masks in the community during an actual pandemic which should result in heightened level of public awareness and community efforts. as some authors unequivocally made it clear, due to the inherent limitations, one cannot base on their rcts to conclude that it offers no benefits to wear a face mask in the community during a pandemic. furthermore, an absence of evidence (from rcts in this instance) should be distinguished from evidence of absence. 22 a previous systematic review identified two case controlled observational studies to assess the effectiveness of wearing a face mask in the community. [23] [24] [25] subsequent to that systematic review, one further relevant observational study was published. 26 all these three observational studies concurred with each other, showing a significant protective effect of face masks in the community, although their findings may be limited by misclassification and reporting bias (see table 2 for details). in view of the imperfect data from the rcts, the mechanistic evidence and the observational studies should contribute to the best available evidence guiding the policy. while efforts should be guided for further clinical research, the benefits of wearing a face mask in the community during a pandemic should be affirmed in the interim. put another way, while the strongest evidence from valid rcts is not yet available, and perhaps it will never be available because of the methodology issue, the choice should favour accepting current best available evidence over putting human lives at risk during a pandemic. summing up, i wish to quote greenhalgh et al as saying '… while there are occasions when systematic review (of rcts) is the ideal approach to answering specific forms of questions, the absence of thoughtful, interpretive critical reflection can render such products hollow, misleading and potentially harmful'. 27 face mask wearers are offered added protection rather than put at higher risk of infection the who recommend that in the community only symptomatic patients and caretakers should wear a face mask. 6 but studies have shown that covid-19 carriers may be asymptomatic and so members of the public may be unaware that they carry the virus. 28 29 the effective control of disease outbreak relies on the concerted efforts of everyone in the community. as the symptomatic infected are asked to wear a mask to avoid splash onto others, the logic should follow that all healthy individuals should also wear a face mask for two reasons. first, they should avoid a splash from others who may be asymptomatic carriers not wearing a mask. second, they may be an asymptomatic carrier themselves. some experts talked about the downside to wearing a face mask and thereby opposed the idea that the general public should wear a face mask. 10 they said people wearing a face mask may be exposed to a higher risk of getting the infection-if they touch their face more often, if they wear the mask improperly or if they dispose of the mask unsafely. there is a previous study showing that some people may touch their face 23 times a day. 30 it was therefore argued that mask wearers who touch the mask on their face may be exposed to a higher risk of infection. such arguments are flawed in that there is no evidence that people who wear a face mask would touch their face more often than those who do not. indeed, given the splash that one without a face mask may receive on the face during usual contact with other people, people who touch their face often is likely exposed to the similar risk of infection regardless of whether they wear a face mask or not. there were also concerns about the use of a face mask because this may offer a false sense of security. 10 11 no effective measure would by itself offer 100% protection. people who wash hands properly and frequently may also have a false sense of security let alone those who do not wash their hands long enough or thoroughly enough. various measures need to be applied in combination to achieve maximal effectiveness. the proper response should be to reinforce the proper way of applying all useful measures in combination through education. a previous study showed that the use of a face mask likely reduces viral exposure and infection risk on a population level in spite of imperfect fit and imperfect adherence. 31 to assert that the use of a face mask in the community may impose a higher risk of infection on the ground of improper use or false sense of security has no support of valid scientific evidence, defies common sense and raises suspicion of an implicit decision not to act or to act on the basis of past practice rather than available evidence. 13 the current available evidence about the benefits of its use should prompt the policy makers to recommend it with no further delay. rationing offers no moral ground to ignore the evidence about the benefits of wearing a face mask in the community it has been suggested that face masks should be reserved for healthcare workers, the sick and caregivers. 7 while this can be a ground for rationing the distribution of face masks to those in greater needs, this by no means offers a reasonable basis to ignore the evidence about its benefits in the community setting. to start with, the authorities bmj global health should have always kept a sufficient amount of protective gears for the healthcare workers and for everyone in the community in preparation of an outbreak. in case of shortage during a pandemic, there is no dispute that those in greater needs such as healthcare workers should be given higher priorities of getting face masks. however, it is also important to protect the public and slow the spread of the infection in the community. the proper approach to addressing shortage is to formulate stratified recommendations that take full account of the benefits of using face masks in the community and provide solutions at different scenarios (see table 3 ). acknowledging the benefits of using face masks in the community does make a big difference. an analogy can be made to patients with end-stage renal disease. even for those who are given lower priorities for renal transplantation, amid severe organ shortage, they deserve to have their needs recognised, to be put on a waiting list and to be given the hope and the chance of receiving the best cure. the rationale is plain. dignity is an essential dimension of human health and even dying patients deserve to have their needs recognised and treated with respect. 32 in a similar vein, during a pandemic, even when the public cannot be allocated sufficient face masks, they deserve to have their needs treated with respect. in case the public are asked to sacrifice their well-being for the overall benefits of the entire community, they need to be told of this and they deserve the credits. those who are given higher priorities for face masks are protected by administrative tools and legal means available to the authorities to ensure adequate supplies to them. on the other hand, manipulating the otherwise legitimate demand from those given lower priorities would unjustly deny the free market a chance to respond to their genuine need with accelerated production of face masks or invention of substitute products. any effort of rationing by means of ignoring the evidence about the benefits for the users of lower priorities does not fit into any current ethical framework 33 and would be counter to maintaining public trust in the public office and the medical profession. herd immunity offers no moral ground to let the infection spread one may even suggest that infection should be allowed to spread to produce herd immunity. herd immunity was recognised when it was observed in the 1930s that the number of new infection subsequently dropped after a significant number of children became immune to measles. nowadays, it can be produced by vaccinating the community. in theory, allowing the infection to spread naturally can also produce herd immunity. given the existing public health tools to slow down the spread of bmj global health infection, however, allowing infection to spread naturally would mean sacrificing human lives with intention. at best, this would be highly controversial and would only be remotely justifiable if and only if there was evidence that sacrificing some human lives at first can save more human lives at the end. there is no such evidence. nor do we have any evidence that people infected with covid-19 at one time point may develop immunity in the subsequent exposure to the same or slightly mutated virus. we may also remain optimistic that a vaccination may be available in a matter of months or early next year. in the circumstance, the priority should be to protect human lives by all means. when there are measures that potentially can slow down the spread of infection, with wearing a face mask in the community being one of them, they must be actively pursued. we are still in the battle against covid-19. while social distancing and hand washing form the main recommendations, there is no shortage of mechanistic evidence and observational studies that affirmed the benefits of wearing a face mask in the community. wearing a face mask is an effective, cheap and easy-to-implement measure. it is more essential when social distancing is less feasible, such as on public transport, when people shop for daily essentials, and for people who cannot work from home. the development of covid-19 pandemic and the current crisis may in part be attributable to the insufficient protection for the community. while the benefits of the universal use of face masks in the community should have been recognised earlier, it will never be too late to implement what is necessary. there may be a long period that other more aggressive measures such as border closure, lockdown and social distancing need to be relaxed to some extent after the peak of the pandemic but before the pandemic completely subsides. this will be the time the general public will need sufficient protection more than ever. the recommendations can be tailored to different scenarios but the bottom line is that it should remain faithful to the current available evidence. i urge the who and policy makers worldwide to consider my stratified recommendations, or adopting measures to a similar effect (see table 3 ). acknowledgements the author would like to thank ben cowling for helpful comments on an earlier draft. funding the author has not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors. competing interests none declared. patient consent for publication not required. provenance and peer review not commissioned; externally peer reviewed. open access this is an open access article distributed in accordance with the creative commons attribution non commercial (cc by-nc 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. see: http:// creativecommons. org/ licenses/ by-nc/ 4. 0/. orcid id tak kwong chan http:// orcid. org/ 0000-0001-7349-4345 face masks for the public during the covid-19 crisis nonpharmaceutical measures for pandemic influenza in nonhealthcare settings-personal protective and environmental measures nonpharmaceutical measures for pandemic influenza in nonhealthcare settings-social distancing measures a quantitative assessment of the efficacy of surgical and n95 masks to filter influenza virus in patients with acute influenza infection efficacy of soap and water and alcohol-based hand-rub preparations against live h1n1 influenza virus on the hands of human volunteers coronavirus disease (covid-19) advice for the public: when and how to use masks covid-19): steps to prevent illness are face masks useful for preventing coronavirus daily updates on the coronavirus: is wearing a surgical mask, as protection against acute respiratory infections said in a video on bbc reported as saying on bbc evidence-based public health: moving beyond randomized trials evidence for health decision making -beyond randomized, controlled trials turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of covid-19 quoted as saying on bbc mask use, hand hygiene, and seasonal influenza-like illness among young adults: a randomized intervention trial facemasks, hand hygiene, and influenza among young adults: a randomized intervention trial facemasks and hand hygiene to prevent influenza transmission in households: a cluster randomized trial impact of nonpharmaceutical interventions on uris and influenza in crowded, urban households findings from a household randomized controlled trial of hand washing and face masks to reduce influenza transmission in the role of facemasks and hand hygiene in the prevention of influenza transmission in households: results from a cluster randomised trial rational use of face masks in the covid-19 pandemic the use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence sars transmission, risk factors, and prevention in hong kong risk factors for sars among persons without known contact with sars patients effectiveness of vaccination and wearing masks on seasonal influenza in matsumoto city time to challenge the spurious hierarchy of systematic over narrative reviews? the transmission and diagnosis of 2019 novel coronavirus infection disease (covid-19): a chinese perspective face touching: a frequent habit that has implications for hand hygiene professional and homemade face masks reduce exposure to respiratory infections among the general population promoting dignity: the ethical dimension of health fair allocation of scarce medical resources in the time of covid-19 key: cord-253786-dvh2wnwj authors: church, lauren elizabeth; nagi, gurnoor title: comment on: frequency of face touching with and without a mask in pediatric hematology/oncology health care professionals: for application to the covid‐19 pandemic date: 2020-08-03 journal: pediatr blood cancer doi: 10.1002/pbc.28634 sha: doc_id: 253786 cord_uid: dvh2wnwj nan the american society of pediatric hematology/oncology comment on: frequency of face touching with and without a mask in pediatric hematology/oncology health care professionals: for application to the covid-19 pandemic we thank the authors for their contribution to literature regarding face touching (ft) associated with mask use. the ongoing covid-19 (sars-cov-2) pandemic provides an important context, given the global cultural landscape of use of masks by the general population. the uk mandate for masks on public transport and shops has been recently published 1 ; mask wearing poses unique risks if not done properly. our response to this article attempts to highlight some of these concerns. the study observed a total of 330 person-minutes. it was found that face touching was lower with masks (5 ft/h compared to 20 ft/h without) in a health care setting. 2 it took place in health care professionals (hcp), who would have had access to and use of masks throughout training and practice. it can therefore be inferred that they would be habituated in good mask practice. in public populations lacking training, there is the potential that the mask changing process can pose risk of infection. 3 this would have particular relevance to the doffing process, where potentially infected internal surfaces can be touched, and people can touch their face with infected hands. a study in 10 individuals performing isolated office work without masks found that hand-to-face contact rate was 15.7 ft/h. this is comparable to the 20 ft/h found in the study under discussion. it should be noted that this study was observed in a student population, and none of the participants was noted to be a hcp. 4 there is no evidence that decreased face touches while wearing masks can be applied to public populations. particularly in mask users who wear glasses, the combination of the flexible nose strip of a mask with the bridge of a pair of glasses may cause discomfort. this coupled with glasses' inclination to gather condensation might cause increased adjustments to the mask during wear. this may be mitigated by training; initial wear in a naive general public may cause discomfort and lead to improper use. we again offer our gratitude to the authors of the study for their work. further studies should be completed, allowing for more personfurther to this, public health campaigns regarding correct mask protocol and avoiding face touching can be evaluated for efficacy; this could involve randomising groups to receive training and then observing mask use. should this be done in a large enough sample size, the true benefit of public health information regarding masks could be assessed. with the covid-19 pandemic remaining pervasive in many countries across the world, limiting infection risk through hand-to-face contact will be paramount in public health maintenance. the authors declare that they have no relationships, financial or otherwise, with any organisation that might benefit from this piece. gurnoor nagi to-wear-one-and-how-to-makeyour-own/face-coverings-when-to-wear-one-and-how-to-makeyour-own frequency of face touching with and without a mask in pediatric hematology/oncology health care professionals. pediatr blood cancer. 2020:e28593 reducing covid-19 transmission from potentially asymptomatic or pre-symptomatic people through the use of face masks a study quantifying the hand-to-face contact rate and its potential application to predicting respiratory tract infection key: cord-262200-2enorlii authors: nan title: use of masks by health care workers date: 2020-05-30 journal: bull acad natl med doi: 10.1016/j.banm.2020.05.096 sha: doc_id: 262200 cord_uid: 2enorlii nan prevent the transmission of sars-cov-2. for healthcare workers, the choice of mask may vary depending on whether they are in contact with patients presumed to be healthy, suspect or affected by covid-19, and according to the type of care [1] . in all cases, this choice is a compromise: the more effective a mask, the less ''it is permeable'', and the more uncomfortable it is to wear. in the context of the covid-19 pandemic, three types of masks are available to healthcare workers: • surgical masks, also known as masks for medical use or anti-projection masks ( the national academy of surgery, may 23, 2020. tecting the wearer. they are not medical devices. their wearing is more restrictive than that of surgical masks. ffp2 masks (filtering at least 94% of aerosols) without an exhalation valve are recommended to health professionals performing procedures that expose them to aerosols loaded with fine particles and viruses (the valve provides a better comfort but does not filter); the national academy of medicine and the national academy of surgery recommend to healthcare personnel: • in civilian life, to wear a type i surgical mask or a standard ''general public'' mask, industrially manufactured or home-made, as soon as they leave their home. each person should consider himself as a potential carrier of the virus and contagious, even when he is feeling healthy [3] . as a caregiver he needs to act as an example; • in the professional life, to wear a mask adapted to the risk of contamination: • a type ii surgical mask in community or hospital medicine, during direct contact with patients, especially if they show respiratory signs, a suspected or a confirmed infection, but only if they are not performing an invasive intervention on the respiratory tract, • a type ii or type i surgical mask for professionals in charge of first aid, or medical transport, or in contact with a fragile public (ehpad and home care). these rules must apply even in the non-covid sector, as any patient is a potential carrier of the coronavirus, • an ffp2 mask without protection valve during acts exposing to fine particle aerosols or viruses (ent examination, nasal sampling, intubation/extubation, bronchial fibroscopy, dental care, respiratory physiotherapy. . .); • to consult, for correct use of the mask during fitting, wearing and removal, the tutorials [4] and videos [5] available online (afnor, inrs, ars, etc.); • to choose an ffp2 mask according to the morphology of the face, a good fitting to the face being an essential condition for effectiveness. the simplest verification test is called ''fit-check'' or ''negative pressure test''. soft masks (''duck's beak'' and ''pleated'') appear to be more suitable than ''hard shell'' masks. the creation of abacuses from the morphological parameters of the face could help in the choice of a personalized mask; • to use over-gowns, gloves and goggles in addition to the ffp2 mask in certain circumstances, as sars-cov-2 contamination may pass through other entry points than the respiratory tract. the authors declare that they have no competing interest. avis du 24 mars 2020 portant sur la place des masques alternatifs en tissus dans le contexte de l'épidémie à covid-19 masques et covid-19 pandémie de covid-19 : mesures barrières renforcées pendant le confinement et en phase de sortie de confinement bien ajuster son masque pour se protéger comment bien oser un masque : la méthode key: cord-284925-vy2li9lz authors: lam, dennis shun chiu; wong, raymond lai man; lai, kenny ho wa; ko, chung-nga; leung, hiu ying; lee, vincent yau wing; lau, johnson yiu nam; huang, suber s. title: covid-19: special precautions in ophthalmic practice and faqs on personal protection and mask selection date: 2020-04-29 journal: asia pac j ophthalmol (phila) doi: 10.1097/apo.0000000000000280 sha: doc_id: 284925 cord_uid: vy2li9lz the coronavirus disease 2019 (covid-19), caused by severe acute respiratory coronavirus-2, was first reported in december 2019. the world health organization declared covid-19 a pandemic on march 11, 2020 and as of april 17, 2020, 210 countries are affected with >2,000,000 infected and 140,000 deaths. the estimated case fatality rate is around 6.7%. we need to step up our infection control measures immediately or else it may be too late to contain or control the spread of covid-19. in case of local outbreaks, the risk of infection to healthcare workers and patients is high. ophthalmic practice carries some unique risks and therefore high vigilance and special precautions are needed. we share our protocols and experiences in the prevention of infection in the current covid-19 outbreak and the previous severe acute respiratory syndrome epidemic in hong kong. we also endeavor to answer the key frequently asked questions in areas of the coronaviruses, covid-19, disease transmission, personal protection, mask selection, and special measures in ophthalmic practices. covid-19 is highly infectious and could be life-threatening. using our protocol and measures, we have achieved zero infection in our ophthalmic practices in hong kong and china. preventing spread of covid-19 is possible and achievable. t he world health organization (who) officially named the atypical pneumonia the coronavirus disease 2019 (covid19) , which is caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2). on march 11, 2020 , who declared covid-19 outbreak a pandemic. as of april 17, 2020, >2,000,000 people from 210 countries and territories had been infected. the death toll is >140,000. the case fatality rate (cfr) is 6.7%. despite sharing similar properties with other lethal coronaviruses, covid-19 is much more infectious, and has become the biggest challenge to healthcare systems in many countries including the developed ones who have the most advanced healthcare facilities. before vaccines and/or specific treatments are available, infection control is the key to minimize damage made by covid-19. this can be achieved by case identification, contact tracing, isolation, and supportive treatment. personal hygiene and social distancing are extremely important as well, since these are the means to prevent community spread. ophthalmologists are at risk of covid-19 infection, since routine ophthalmic examinations are usually performed in a setting with close doctor-patient contact. moreover, the covid-19 present in tears could become a source of crossinfection. therefore, eye care professionals shall remain highly vigilant all the time during the pandemic. in the following sessions, we will discuss the properties and characteristics of sars-cov-2 and covid-19. we have also prepared answers to frequently asked questions (faq) regarding the virus, personal hygiene, and the differences between various face masks. we have also shared the precautions and strategies that we have implemented in our ophthalmic practice, based on our previous and current successful experiences in preventing severe acute respiratory syndrome (sars) in 2003 and the current covid-19 outbreaks in hong kong. coronaviruses spread mainly through inhalation of droplets, direct or indirect contacts, and to a limited scale, aerosol-related transmission. direct contact means the virus is transmitted from the infected to the healthy through direct physical contacts, whereas indirect contacts are usually transmitted through fomites. droplets as well can transmit the infection both by direct and indirect means. it can be inhaled directly by others when the infected cough or sneeze; in contrast, droplets may settle on table surface, and later on when another person touches the table before touching his own mucosal surfaces (including nose, mouth, and eyes), the transmission of disease might then happen. [1] [2] [3] aerosols are a collection of very tiny droplets in air, produced in specific circumstances, which are capable of traveling a longer distance and longer time in air, compared with typical droplets, before settling down owing to the small size and light weight. aerosols can be generated during aerosol-generating procedures in hospital settings, such as resuscitation, endotracheal intubation, positive pressure ventilation, tracheostomy insertion, bronchosocopy, airway suction, and so on. 4, 5 when medical personnel is performing aerosol-generating procedures, full personal-protective equipment should be put on, including goggles, n95 respirators, face shield, protective gowns, and shoe-cover, among others. coughing, sneezing, toilet flushing, cigarette smoke, and hot pot steam, among others, might also have a possibility to generate infective aerosols but need further studies to confirm it (fig. 1) . epidemiologists use basic reproductive number (r 0 ) to represent the infectivity of certain infectious disease. it is defined as the number of individuals being infected when a confirmed case enters the population composed of only susceptible individuals. 6 for example, r 0 ¼ 1.0 means on average an infected patient would infect one other healthy individual in the community and r 0 ¼ 2.0 refers to 2 healthy individuals acquired the infection from a single confirmed case. r 0 of covid-19 was initially estimated to be 2.2 to 2.7; however, as more data are available with time, some epidemiologists suggested that the true r 0 of this virus could be much higher and lies between 3.3 and 5.47, or even higher between 4.7 and 6.6. 7, 8 in contrast, r 0 of sars-cov were 1.88 in beijing, 1.70 in hong kong, and 0.95 worldwide, 9, 10 whereas r 0 of mers-cov were 0.47 in middle east, 0.45 in saudi arabia, and 0.91 overall for middle east and south korea. 10, 11 the infectivity of covid-19 is, therefore, highest among the 3 lethal coronavirus infections. the cfr, however, has a reverse order for the 3 viruses when comparing with infectivity. they are 6.7%, 9.6%, and 34.4% for covid-19, sars, and mers, respectively. 12 possible reasons for the covid-19 to be more infectious than mers or sars coronavirus sars-cov-2 utilizes the same cellular receptors as sars-cov, the human angiotensin-converting enzyme 2. therefore, it is expected that this new virus would behave very similar to sars-cov in terms of transmission properties, such as causing lower instead of upper respiratory tract symptoms. 13 however, unlike sars-cov or mers-cov, epithelial cells in human airway are more suitable than standard tissue culture medium for the growth of sars-cov-2. 13 moreover, the incubation period of this virus is up to 24 days and the virus is capable of transmitting the disease even when patients only have mild or even no symptoms. 14 unlike sars in which most patients developed fever, studies from china and europe showed only 43% to 48% of them had fever at the time of admission. 15, 16 this renders comprehensive early identification of cases extremely difficult. lastly, the low cfr of the disease relative to sars and mers may make people more complacent and less compliant with preventive measures. with global spread, the role of quarantine is to slow or stop the transmission of infection so that serious cases are at least spread over a longer period of time. an uncontrolled outbreak of infection could easily overwhelm the ability to care for patients and lead to exponential spread. all of the aforementioned characteristics of covid-19 facilitate the transmission of virus in the community thus increasing the difficulty of its containment. further studies to investigate the mechanisms for covid-19's high infectivity are warranted. coronaviruses (covs) are the largest group of viruses belonging to the nidovirales order. the name "coronavirus" comes from the latin "corona," which means crown, due to its characteristic appearance resembling a crown or solar corona. cov can induce respiratory, gastrointestinal, and neurological dysfunction in their hosts and predominately respiratory infections in human (fig. 2) . 17 a total of 7 species of covs have been found to be pathogenic to humans, including hku1, oc43, nl63, and 229e, which can lead to mild upper respiratory tract infections and are still circulating among human, 18, 19 whereas the more aggressive sars-cov, mers-cov, and sars-cov-2 are zoonotic and these viruses crossed species from animals and infected human. sars was first known to human in 2002 to 2003, starting in guangdong province of china, infecting 8098 people worldwide and with a cfr of 9.6%. 20,21 mers-cov, however, first appeared in 2012 in saudi arabia, infected almost 2500 people, mainly in the middle east and korea and with a high cfr of 34.4%. 22 recently, a new member to the coronavirus family, sars-cov-2, has led to a large-scale pandemic with an estimated cfr of 6.7%. 23 the earliest cluster of covid-19 identified as "pneumonia of unknown etiology" or "atypical pneumonia" was defined as evidence of pneumonia on x-ray or computer tomography scans, fever of !388c, normal or low white blood cell count, and no clinical improvement despite standard antibiotics treatment for 3 to 5 days. according to the studies from china and europe, symptoms of covid-19 include fever, olfactory dysfunction, gustatory dysfunction, cough, fatigue, sputum, shortness of breath, conjunctival injection, and so on (fig. 3) . 13, 15, 16 viable sars-cov-2 could be detected in aerosol up to 3 hours after aerosolization, thus raising concerns on the possibility of viral transmission through aerosolization. the survival time of sars-cov-2 varies among different materials. for example, viable sars-cov-2 could only be detected on copper up to 4 hours, but its survival time could be as long as 2 to 3 days on plastic and stainless steel (table 1) . 24 therefore, indirect transmission of sars-cov-2 through fomite is highly likely! to lower the risk of infection, we must always remain vigilant and be aware of personal hygiene. droplets, in term of respiratory infections, refer to small liquid drops that are generated by expiratory events such as coughing, sneezing, laughing, talking, or even breathing. 25 aerosols are suspensions of small liquid droplets or solid particles in air. droplets are subdivided by size into large and small droplets, and the smallest form as droplet nuclei. the size definitions vary among studies, but most naturally and artificially produced aerosols contain a range of droplet sizes. after being expelled, droplets are usually brought down to ground under gravity and are transmitted over a limited distance only. however, the water content of small droplets may evaporate during the stay in air, producing even smaller droplet nuclei that could then remain suspended in air and could be transmitted over a long distance (fig. 1 ). 26 the traditional model of infectious disease, known as the epidemiologic triad, consists of a pathogen, a susceptible host, and an environment that brings the host and agent together. the overall risk of infection further depends on the infectivity, pathogenicity, and virulence of the invading pathogen. effective preventive measures for infectious disease require assessment of all the above components and their interactions. in general, it is advisable to avoid going to places that are crowded with people, or with higher risk of infection such as clinics or hospitals. good hand hygiene and proper wear of suitable face mask are other key preventive measures. standard recommendation on hand hygiene is to use alcoholbased handrubs or washing hands with soap and water for at least 29 ethanol is the ingredient present in most alcoholic drink. however, commercially available high concentration ethanol may contain toxic additives to prevent people from drinking as required by certain countries, making it less popular as disinfectant. isopropyl alcohol, however, is produced in high quantities with high purity, and is widely used in households and industries as disinfectants or detergents. face mask is defined as a physical barrier loosely worn between the mouth and nose of the wearer and the surrounding. it is not tightly fit and offers no air-sealing. surgical masks are face masks that are qualified to prevent contamination of sterile surgical field. respirators (eg, n95 respirators) are air filtration devices designed to remove particulates from inhaled air. it should be tightly fitted onto the mouth and nose to ensure air sealing. one major common property is that they utilize filters to prevent unwanted substances from passing through the barrier, while allowing air to pass through. 30 filters can capture particles of different size through various mechanisms. larger particles are captured by filter fibers directly when they impact or intercept the fibers. smaller particles are constantly bombarded by air molecules, causing them to deviate from the air stream and come into contact with a fiber. furthermore, oppositely charged particles are attracted to charged fiber. all particles that come into contact with a fiber will stay attached to the fiber firmly. in that way, filters can capture particles smaller than the pore size. structures and mechanisms of various filter materials are illustrated in figure 4 . table 2 . n95 respirators are primarily developed for industrial safety to reduce particulates inhaled by wearers. 30,31 they are certified by national institute for occupational safety and health (niosh) under the guidance of "niosh 42 cfr part 84," with the mark "niosh" printed on the surface of the respirators. the notation "95" implies that they can filter at least 95% of particles sized 0.3 microns, and "n" represents non-oil particles. they are tested under stringent protocols which aim to simulate the "worst case" condition. 32 noncharged sodium chloride particles of 0.3 mm was selected, which represent the most penetrating particle size, where the particles are most likely to bypass various mechanisms to capture them. n95 respirators have also been tested under conditions similar to that of astm standards, showing filtration efficiency of >99% for uncharged particles sized around 0.1 mm. 33 the overall filtration efficiency of n95 respirators is superior to surgical masks of all astm levels. (see fig. 5 for performance of various respirators and masks). 34 n95 respirators offer better protection than surgical masks, which are loosely fit and not air-tight. both of them offer protection against splash of fluid and droplets, but only n95 respirators protect the wearer against small viral particles or aerosol inhalation. fitting procedure is required for n95 to ensure tight air-seal, and should not be worn by children, men with beard or individuals with breathing difficulty. n95 respirators offer better protection against air-borne infection. for surgical masks, fitting procedure is not required. although the theoretical particle filtration efficiency of the filter material in surgical mask may reach 98% (for astm level 2 and 3 masks), the actual total inward leakage (til) may reach 30% to 35% due to inadequate sealing. 34, 35 therefore, 30% to 35% of air that is breathed into the wearer's respiratory system might not have passed through the filtering materials of surgical marks. this is the reason why surgical masks can prevent droplets but not airborne particles or aerosols. despite that, surgical masks should be worn by individuals with suspected respiratory infections, effectively lowering the environmental contamination due to droplets expelled by individuals with respiratory infection. for healthcare workers, surgical masks should be worn when performing sterile procedures, or as general protection against droplets infections. for public use, such as individuals with respiratory symptoms, people exposed in crowded and poorly ventilated places, such as taking public transports, students in school and individuals visiting clinics or hospitals, surgical masks are also recommended. 36 n95 respirators are recommended to be worn by healthcare workers when working in high-risk areas such as fever wards, inpatient or isolation rooms for patients with confirmed or suspected covid-19. 36 they should be removed and discarded when leaving the patient room or care area, followed by immediate hand hygiene. the outer layer of masks is considered dirty, whereas the inner layer is relatively clean. hand hygiene should be performed before and after taking off the mask to avoid contamination of our hands. mask should be fitted snugly over the face. other points worth noting are: the colored side of the mask should face outwards; the metallic strip at the uppermost side molds to the bridge of the nose; the mask covers the nose, mouth, and chin; the strings or elastic bands are positioned properly to keep the mask firmly in place; and avoid touching or manipulating the mask once secured on face as frequent handling may reduce its protection. if you must do so, wash your hands before and after touching would help. change masks timely. replace the mask immediately if it is damaged, wetted, or soiled. after taking off the mask, discard it into a lidded waste bin and perform hand hygiene immediately. surgical n95 mask is a subgroup of n95 respirator that also fulfils astm requirements and food and drug administrationcleared as surgical mask. they are fluid-resistant, whereas other standard n95 respirators may not be fluid-resistant. both types exhibit similar filtration efficiencies for small particles like viruses. for general protection of the wearer, standard or surgical n95 respirators will all suffice. 32 the key difference is that the surgical n95 masks prevent the wearers from contaminating the surgical field or environment and are used when performing sterile procedures under the threat of air-borne transmission. there are industrial respirators with higher filtration efficiency available, eg, n99, p100, etc. however, their uses in healthcare settings are often limited due to relatively lower breathability. respiratory distress may occur after prolonged wearing. n95 respirators already provide good protection against viral droplets or aerosol protection and their breathability are similar to surgical masks. therefore, they are satisfactory in most healthcare settings, especially when prolonged wearing is needed. 31 no, the protection is very limited! although reusable cotton masks can be sterilized for reuse, they generally suffer from limitations including low filtration efficiency, time-consuming production, and higher risk of contamination. charcoal-activated carbon masks are intended to absorb chemicals from inhaled air. those masks are not formally tested for the particle and bacterial filtration efficiency, and do not claim for protection from airborne or droplet transmission. at the height of covid-19 epidemic, it would be better than none to be worn by patients with respiratory symptoms to reduce environmental contamination, if surgical masks are not available. the close proximity of patients and doctors during eye examination, the presence of tears and liquids for anesthesia and dilation, or the potential aerosol or droplets from "air puff" tonometry, all pose a high risk for infective transmission. 37 conjunctivitis was reported to be present in 0.8% to 5.2% of covid-19 patients. 15, 38, 39 conjunctivitis can be the presenting symptom/sign of covid-19, high vigilance is essential as conjunctivitis is a common condition in ophthalmic practice. furthermore, because eye centers could harbor asymptomatic patients with covid-19 that have subtle or even no symptoms, proper precautions should be taken to protect for both patients and staff from the infection. yes. conjunctivitis could be present in covid-19 patients, and virus may even be present in their tears and conjunctival secretion. direct contact with the ocular surface and mucosal membrane during routine ophthalmic examination may have risk of infection. the doctor-patient distance during examination is usually <1 m, where the possibility of droplet transmission is high if there is no proper protection. air jet produced in non-contact tonometry might also generate aerosol of fluids from the eye, which might be infectious. last but not least, ophthalmic centers may be crowded with patients with potential risk of infection. extra precautions should be taken in ophthalmic practices. preventing patients with potential respiratory infection from entering the facilities might minimize the chance of exposure. for patients with potential risk, nonurgent ophthalmic consultations will be deferred after appropriate period of quarantine and observation. special precautions will be taken in handling such patients with sight-threatening conditions ( fig. 6 and table 3 ). patients are screened before entering the facilities by phone screening and triage at the entrance. face masks should be worn by all personnel and visitors inside the facilities. visitors wait at an adequately ventilated area, keeping at least 1-m distance from others, and were provided with adequate alcohol-based handrubs, rubbish bins, and educational material in the waiting area. in consultation rooms, transparent shields are installed on slit-lamps to prevent droplet transmission. all instruments and surfaces are disinfected properly after each use. if patients are screened as high risk of covid-19 infection and having ophthalmic emergencies, doctor-in-charge should be informed. ideally patient should be isolated in a single room, with a dedicated team of healthcare workers entering with full personal protective equipment including n95 respirators for examination. patients are not allowed to enter the public waiting areas. potentially aerosol-generating procedures are to be avoided. all equipments are disinfected immediately after patient contact. in slit-lamp examination, physical barrier between doctors and patients is advisable to prevent droplet transmission. commercially available breath shields are available, but producing home-made shields is not difficult. the material chosen should be highly transparent to allow effective visualization, rigid enough not to collapse, and thin enough to be cut into desired shape (fig. 7) . a clear polyvinyl chloride document holder is a good choice. make a central opening and fit it in between the optical modules. the edges of the shield should be smoothen with a sand paper polisher should it be too rough or sharp. the size of the shield should not be too small in which protection effect will be compromised; or too large in which manipulation of the slit-lamp equipment will become difficult. the size of an a3 size paper or one that is slightly larger would be quite optimal and recommended. the location of the hole is also important. we want the upper portion to be larger to provide more protection while the lower portion to be smaller to allow easier access to slit-lamp manipulation. it should be cleaned and disinfected regularly. the patient contact areas of general equipment such as slitlamp, non-contact tonometer, autorefractor, and so on should be disinfected with 70% to 75% ethanol or isopropyl alcohol immediately after each use. instruments that had direct contact with patient's ocular surface such as goldmann applanation tonometer prisms and diagnostic contact lenses are disinfected by immersion in either 1:10 diluted bleach solution with sodium hypochlorite or 3% hydrogen peroxide for at least 5 minutes. surgical instruments are sterilized according to standard protocols. in non-contact tonometry, the air jet impacted on the tear film was reported to general micro-aerosols. 40, 41 since sars-cov-2 was reported to be present in tears and conjunctival secretions from covid-19 confirmed patients with conjunctivitis, extra caution shall be exercised when performing noncontact tonometry on patients with red eyes. alternative methods such as rebound tonometry could be considered. operators should wear proper face mask or respirator. surgical mask should be worn by all patients entering operating rooms, to prevent contamination from coughing or sneezing. adhesive tape could be applied across the nose bridge area to ensure complete coverage of patient's nose and mouth. in our center, we also require patients changing their clothes and putting on surgical caps to further reduce the risk. for patients with suspected respiratory infection or exposure risk, only urgent operations would be considered. they would be scheduled as last case of operation to allow thorough disinfection afterwards. all personnel should be cautious and vigilant against sharp needles or blades injury. it would be a good idea to refer high-risk cases to hospitals that have adequate facilities such as negative-pressure isolation rooms to provide proper care to patients. the outbreak of covid-19 has now spread to every part of the world. the key to successful reduction in morbidity and mortality during this pandemic relies on early identification, containment, prevention of transmission, and adequate supportive treatments. before safe and effective vaccines and specific treatments are available, the only way to control and contain covid-19 would be applying the basic principles and measures in the prevention of the transmission of the disease. covid-19 is an infectious disease following every rule in the field of infection control; therefore, as long as good infection control measures are implemented, prevention of disease spreading and zero new case in medical practices are not impossible. these are extremely important and relevant since there have been at least 3000 and 2600 medical professionals and healthcare workers infected in china and italy, respectively. in the midst of the current pandemic, everyone on this planet has to be highly vigilant and compliant to the precautions. we hope our answers to the frequently asked questions would help one be more fully equipped with the necessary knowledge and know how to protect oneself and the people around him/her. early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia turbulent gas clouds and respiratory pathogen emissions potential implications for reducing transmission of covid-19 novel coronavirus (covid-19) outbreak: a review of the current literature aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review quantity and size distribution of cough-generated aerosol particles produced by influenza patients during and after illness the basic reproduction number as a predictor for epidemic outbreaks in temporal networks preliminary estimation of the basic reproduction number of novel coronavirus (2019-ncov) in china, from 2019 to 2020: a data-driven analysis in the early phase of the outbreak the novel coronavirus, 2019-ncov, is highly contagious and more infectious than initially estimated superspreading and the effect of individual variation on disease emergence transmission characteristics of mers and sars in the healthcare setting: a comparative study unraveling the drivers of mers-cov transmission novel coronavirus of pneumonia in wuhan, china: emerging attack and management strategies the novel coronavirus: a bird's eye view transmission of 2019-ncov infection from an asymptomatic contact in germany clinical characteristics of coronavirus disease 2019 in china olfactory and gustatory dysfunctions as a clinical presentation of mild-to-moderate forms a3-sized transparent plastic sheet with round corners and a round hole of 64 mm (fit for haag-streit models) in diameter produced by a round cutter. the upper portion is larger to provide better protection, while the lower portion is smaller to allow easier access to slit-lamp manipulation; (b) the shield (red arrows) provides a barrier between the patient and the ophthalmologist; (c) the eye piece and the microscope modules of the slit-lamp are carefully dissembled of the coronavirus disease (covid-19): a multicenter european study coronavirus pathogenesis epidemiology and clinical presentations of the four human coronaviruses 229e, hku1, nl63, and oc43 detected over 3 years using a novel multiplex real-time pcr method detection of the human coronavirus 229e, hku1, nl63, and oc43 between 2010 and 2013 in yamagata severe acute respiratory syndrome the aetiology, origins, and diagnosis of severe acute respiratory syndrome middle east respiratory syndrome a novel coronavirus from patients with pneumonia in china aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 dynamics of infectious disease transmission by inhalable respiratory droplets airborne transmission of exhaled droplet nuclei between occupants in a room with horizontal air distribution interim infection prevention and control recommendations for patients with suspected or confirmed coronavirus disease 2019 (covid-19) in healthcare settings 30. n95 respirators and surgical masks novel coronavirus and covid-19 outbreak -3m personal protective equipment (ppe) considerations. available at niosh-approved particulate filtering facepiece respirators filter performance of n99 and n95 facepiece respirators against viruses and ultrafine particles effect of particle size on the performance of an n95 filtering facepiece respirator and a surgical mask at various breathing conditions how does breathing frequency affect the performance of an n95 filtering facepiece respirator and a surgical mask against surrogates of viral particles? aerosol transmission of infectious disease evaluation of coronavirus in tears and conjunctival secretions of patients with sars-cov-2 infection ophthalmologists' strategy for the prevention and control of coronavirus pneumonia with conjunctivitis or with conjunctivitis as the first symptom microaerosol formation in noncontact 'air-puff' tonometry aerosol formation during non-contact "airpuff" tonometry and its significance for prevention of covid-19 patient not allowed to enter common waiting area 8. may wait in personal vehicle or outside the healthcare facility and called back upon their turn for ophthalmic assessment 9. patient must wear face mask key: cord-275370-bt45gnqk authors: arellano-cotrina, josabet johana; marengo-coronel, nicole; atoche-socola, katherine joselyn; peña-soto, claudio; arriola-guillén, luis ernesto title: effectiveness and recommendations for the use of dental masks in the prevention of covid-19: a literature review date: 2020-07-17 journal: disaster medicine and public health preparedness doi: 10.1017/dmp.2020.255 sha: doc_id: 275370 cord_uid: bt45gnqk the purpose of this investigation was to identify, synthesize, and compare all the current information on the efficacy of dental masks, emphasizing their use, types, and filters to prevent the spread and infection of covid-19 and other infectious diseases. a bibliographic search of the main scientific databases was carried out using the words “masks, covid-19, and dentistry.” articles without language restriction up to may 31, 2020, were obtained. the types of masks, their half-life, method to use, sterilization, and proposed alternatives for dental masks were analyzed. most of the articles refer to the use of n95 or ffp2 respirators presented as a strategy to extend the life of the masks and limited reuse. regarding sterilization, most of the articles presented studies using ultraviolet germicidal irradiation as the sterilization method. regarding respirator mask half-life, we recommend prolonged use, combined with a disposable surgical mask over the respirator mask. finally, the use of n95 or ffp2 respirators are recommended as part of personal protective equipment for dental use. a s health professionals, dentists are in the front line and have a high risk of contracting infectious diseases, which can be transmitted by direct or indirect contact through instruments or body fluids, such as blood and saliva. 1 therefore, dentists must comply with biosafety standards to protect both themselves and their patients. 2 safety in dental care should be similar for all patients and not only for those with infectious diseases. operators and patients may be potential asymptomatic carriers of different microorganisms, causing cross-infections that can affect anyone in dental care and that can be transmitted to the family environment, increasing the risk of contagion. 3 on december 31, 2019, the authorities of wuhan, china, notified the world health organization (who) of the presence of an outbreak of viral pneumonia of unknown origin, mainly among vendors or operators of the marine huanan food market. [4] [5] [6] within a few days the disease was called coronavirus disease 2019 (covid-19) caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2 virus, which is transmitted mainly by close contact with secretions or excretions (droplets) of infected patients in the absence of the necessary protective barriers. 7 thus, covid-19 spread rapidly to different parts of the world, and on march 11, 2020, covid-19 was categorized as a global pandemic by the who, 5, 8 the main symptoms being high fever (83-98%), dry cough (76-82%), and difficulty in breathing (17-29%). 4, 9 to ensure good clinical practice, health professionals must comply with a set of rules and behaviors to reduce the risk of contracting infections through the use of protective barriers in each procedure, consisting in the use of scrubs, gowns, hats, disposable gloves, protective glasses, and masks. 10, 11 according to the manufacturers, surgical masks must achieve efficient filtration, resistance to fluids, pressure differential, and flammability. these masks must create a hermetic seal against the skin, preventing the passage of particles, such as aerosols or splashes that may contain bacteria or viruses. mask quality certification relies on 2 types of tests to assess filtration efficiency, including quantitative and qualitative tests, such as the particulate filtration efficiency (pfe) test and the bacterial filtration efficiency (bfe) test. 11, 12 obtention of this certification has a direct impact on the biosafety of professionals and patients. however, effective prevention of infectious diseases depends on the type of mask used. fear of the spread of serious respiratory diseases persists, as in the case of the recent coronavirus pandemic and is largely due to the current lack of effective antiviral drugs and vaccines. 13, 14 the who and the united states centers for disease control and prevention (cdc) recommend a series of fundamental preventive measures, such as protective equipment for health personnel during the care of patients with suspected or confirmed covid-19, one of the most effective being masks. however, the who suggests their use only in the presence of symptoms, and the cdc indicates that the use of n95 respirators is exclusively for health personnel and not for the general public. 15 these masks play an important role in the control of the spread of aerosols in the case of coughing, talking, or sneezing. 16, 17 therefore, the purpose of this research was to identify and synthesize all the current information comparing the efficacy of dental masks, to increase our knowledge about the correct use of different types of masks and filters to prevent the spread and contagion of the covid-19 virus and other infectious diseases. a bibliographic search was carried out in the main databases of the international scientific literature on health sciences (medline) by means of pubmed, ebsco, scopus, scielo, and the latin american and caribbean literature in health sciences (lilacs), using the following keywords: masks, covid-19, and dentistry. articles without language restriction up to may 31, 2020, were obtained. experimental studies, literature review articles, and systematic reviews were used and opinion articles, letters to the editor, and editorials were excluded ( table 1 ). when a pandemic begins difficulties arise due to the lack of vaccines and ideal treatments for the disease, and, therefore, protection barriers play an important role in controlling the spread and prevention of the disease. 18 taking this into account, 2 types of masks have been described: surgical and conventional (or respiratory). the efficacy of these masks depends on their structure and filtering capacity. in this sense, respiratory masks guarantee better protection compared with surgical masks, both of which are disposable. 19 under the european standard, surgical masks are considered a medical device with an official nomenclature of the en 14683 standard that classifies these masks as type i, type ii, and iir. the latter is classified as the most effective for presenting a microbial barrier and resistance to splashes, offering a filtration rate of around 80%. 18, 20 they are designed for protection in only 1 direction to avoid the transmission of infectious agents carried by the user. they prevent the passage of microorganisms present from the inside out; therefore, the use of these masks is recommended for covid-19 patients. 19, 21, 22 however, these surgical masks do not ensure a good hermetic seal, and thereby allow particles to enter around the edges. the classification of respiratory masks is independently certified by 2 major entities: the european committee for standardization (en) and the national institute for occupational safety and health (niosh). both entities guarantee a percentage of filtering capacity of particles that measure 0.3 microns in diameter. respiratory masks must have multiple layers of polypropylene and electrostatic charge, providing adequate protection in 2 directions; that is, they are able to filter both incoming and outgoing air and must be resistant to liquid spray, blood splatter, and of other bodily fluids. likewise, masks are considered to be effectively adjusted when a hermetic seal is achieved on contact with the skin. 17, 19, 21, 23, 24 the european standard en 149: 2001 establishes 3 categories or levels of protection for respiratory masks according to their filtering facepiece (ffp) parts, and these are divided into ffp1, ffp2, and ffp3, with a particle filtration capacity of 0.3 microns of 80%, 95%, and 99%, respectively. 19, 20 on the other hand, the niosh establishes 9 respirator classifications, all with a particulate filtering capacity combining the respirator series (n, r, or p) and the level of efficacy (95%, 99%, 100%). the first part of the respirator classification indicates the resistance of the filter to degradation when exposed to oil-based aerosols, whereas the n series is for use in particulate environments and oil-free aerosols, and the r and p series are for use in particulate environments with and without oil. the number determines the filtering capacity of 0.3-micron particles, being measured in percentages of 95%, 99%, and 100%. 17, 23, 25 the use of n95 masks has been considered a us standard administered by the niosh. these masks are designed to protect users from air particles, including aerosols, 26 with a particle filtration capacity of 0.3 microns of 95% and have less leakage in the face seal due to the tight fit to the user's face 19, 22, 24, 27, 28 n99 masks have a 0.3-micron particle filtration capacity of 99%, while n100 masks provide 99.7% filtration protection. 23 or (dentistry)) and (coronavirus)) and (n95)) (((dentistry[mesh terms]) or (dentistry)) and (covid 19)) and (respirator)) ( on the other hand, the use of kn95 respirators of chinese origin are available in the dental market and comply with gb 2626-2006 regulations. these masks have a filtration capacity of 94-95% of particles with 4 overlapping layers, which are fused together to avoid the exit of particles from the carrier and the aspiration of aerosols or drops that may contain the virus. these respirators are considered to be functionally similar to the niosh-certified n series. 12, 23 mean life of the masks an important approach to moderating mask wear and avoiding scarcity is to adopt strategies for mask reuse. 17, 18 the cdc recommends 2 conservation strategies for respirators: extended use and limited reuse. 29, 30 surgical and respiratory masks are for single use per patient. however, conservation of these resources is imperative in this crisis. thus, an alternative is use with multiple patients, 12, 20 but with strict biosecurity conditions, involving safeguards, evaluation of sealing, and mask integrity during use. a second surgical mask can be used on the respiratory mask to serve as direct protection against patient fluids, being discarded after use. in the case of using only 1 respiratory mask while under great exposure to infectious droplets due to the aerosols, it is not recommended to reuse the same mask between patients because of a higher risk of contamination. however, this condition can be ameliorated with the use of a face protection mask or the use of 2 masks, which will allow the second protective mask to be discarded and the facial mask disinfected, thereby preserving the respiratory mask. 12, 20 the second form of conservation of respiratory masks is limited reuse, which is the removal of the mask after each patient with restrictions limiting the number of uses. however, this requires strict validation regarding cleaning, sterilization, and functional performance. 29 it is important to consider that the duration of use for surgical masks should not exceed 4 h and 8 h for ffp masks. 19, 20, 31 in the literature, few studies have evaluated the reuse of masks. one study evaluated health policies of 27 countries (in europe and the americas), finding that widespread use and limited reuse of masks is allowed in 10 countries. on the other hand, more than 60% of the countries do not recommend 1 of these 2 strategies. 30 in 1 of its publications, the cdc recommends how to use and dispose of respiratory masks. 32 secure the ties or elastic bands to the middle of the back of the head and neck, and then adjust the band to the bridge of the nose, around the face and chin. finally, check the fit of the mask. after placement, hands must be disinfected with alcohol and washed with soap for at least 20 s. the front of the mask is contaminated and should not be touched. hold the ties or elastic bands of the mask and remove them upward without touching the front. discard in the indicated garbage container and wash your hands with soap for at least 20 s. given the shortage of personal protective equipment (ppe), sterilization and disinfection methods have been determined to prolong the effectiveness of the masks for the prevention of virus transmission. it is important that the sterilization treatment does not deteriorate the material of the respiratory mask, which would decrease the filtering power against infectious pathogens. the cdc has recommended different chemical, radioactive, and physical sterilization methods. 24 different decontamination strategies, such as sterilization by exposure to ultraviolet germicidal irradiation (uvgi), ethylene oxide, or vaporized hydrogen peroxide, have been shown to be effective in maintaining adequate protective function. 30 disaster medicine and public health preparedness from masks. this virus is 7-10 times more resistant to aerosolization and ultraviolet light than the coronavirus. 39 the susceptibility of the virus to gamma irradiation has shown good disinfecting ability by penetration of all the layers of the respirators. however, the use of ionizing radiation is limited because gamma radiation cannot be performed in a health-care center, requiring the need for transportation to another location entailing a risk for the personnel transporting the masks. 29 on the other hand, the cdc reports that some autoclave methods at 160°c in dry heat, 70-75% isopropyl alcohol and soapy water can deteriorate the filter of the respirators, and consequently allow the access of particles through the mask. 24 for mask sterilization, certain requirements must be taken into account, such as the efficacy against the sars-cov2 organism, avoiding damage to the respirator filtration changes in the physical characteristics of the respirators, and ensuring biosafety to the persons who must wear the respirator mask. 29 according to the information obtained from covid-19, the transmission routes are direct or indirect contact with contaminated patients, saliva drops, 12 and large aerosol particles suspended in the air (up to 1 m away), which remain present for a short period of time. 17, 21, 40 in dentistry, there is direct contact with the patient through fluids, such as blood or saliva, and many dental treatments generate aerosols. it should also be taken into account that the sars-cov2 virus has affinity for the angiotensin 2 converting enzyme receptor (ace-2), which is found in the respiratory tract and the salivary gland ducts, producing a high viral load in saliva. 12, 17 different models of masks are available, making it difficult to choose the most suitable type of respirator for dental care. therefore, according to past recommendations, it is recommended to perform fit tests of masks for health personnel to determine the best fit and hermetic seal according to facial dimensions, ethnic origin, and appearance of the fit. the literature recommends that surgical masks should not be used as a substitute for respiratory masks. 19, 27, 41 the use of an n95, ffp2, and ffp3 mask is recommended for personnel working with aerosols. filtration is achieved by combining a polypropylene network and electrostatic charge, 21 thereby explaining their good protective effect against aerosols, and the reason why respirators should not be used by the general public. 22, 31, 42 on analyzing the filtering capacity according to the mask classification, the n95 has shown a similar filtration efficacy to that of ffp2 or kn95. 24 regarding mask sterilization, although it is necessary to determine the exact uvgi doses for mask sterilization against the sars-cov-2 virus, this strategy provides a possibility to extend the use of the limited supply of respirator masks against covid-19, being both profitable and accessible. 33 a major problem with respirator masks is discomfort and the generation of humidity inside, decreasing air permeability. therefore, a super absorbent polymer (sap) has been designed for use in respirator masks. this harmless material absorbs large amounts of liquid is used in baby diapers, sanitary napkins, and incontinence pads. an absorbent layer or sap pad is cut according to the shape and size of the respirator and finally placed inside the respirator. the sap pad helps to quickly absorb exhaled moisture, leading to a longer mask life cycle and providing greater comfort to the professional. 43 in these times of international health alert, dentists have a high risk of contracting covid-19 due to direct contact with body fluids during patient care. therefore, the use of ppe is extremely important for the protection of dentists, with masks being part of the clothing for daily use to avoid aspiration of virus particles. 44 the aim of this literature review was to identify and synthesize all the current information available on the efficacy of the masks in dentistry to prevent the spread of the new covid-19. currently the different types of masks in the market cause confusion at the time to choosing the most adequate equipment. there are 2 types of masks: surgical masks and respiratory masks. surgical masks have a filtering capacity of 80% of particles compared with n95 and ffp2 respirators, which have a 95% filtering capacity of particles measuring 0.3 microns in diameter due to their multiple layers of polypropylene in combination with an electrostatic charge. this good filtering capacity has led to recommending their use a global standardization. 12, 17, 19, 24, 27 ideally, 1 mask is used per patient. however, regulatory authorities are trying to take action involving the widespread use and limited reuse of masks due to the global shortage of ppe. one of the most recommended strategies is the prolonged use of the respirator for different patients, using a second surgical mask over the respirator to protect it from fluids to preserve its integrity. however, it is highlighted that this strategy is only a resource for the protection of health personnel during the covid-19 pandemic, due to the shortage of this equipment. 20, 30 regarding the mask sterilization method, many studies report that covid-19 is susceptible to sterilization by uvgi, which inactivates these microorganisms by damaging their dna. 17, 29 likewise, this method has shown great efficacy, maintaining the protective function of the mask and filtering power against pathogens. in the same way, hydrogen peroxide vapor sterilization is an effective method to prolong mask efficacy. however, these methods still require further study to ensure preservation of the physical characteristics of the respirators and adequate biosecurity for dentists. 30, [33] [34] [35] [36] [37] [38] [39] there are different studies of the efficacy and recommendations for the use of masks to prevent the spread of covid-19. 19, 21, 30 the information described in this study highlights the importance of the resistance of the masks to droplets and aerosols for the prevention of inhalation of contaminating particles, guaranteeing biosecurity to dentists. recommendations are based on the largest evidence available. on the other hand, there are several limitations regarding sterilization for reuse of respirators that should be recognized. further studies are required to standardize adequate and effective exposure to prolong the efficacy of respirator masks. likewise, it is recommended that dental centers adhere to the correct use of respirators, otherwise, they risk endangering their health and the transmission of covid-19 to those in their work environment. the use of n95 or ffp2 respirators is recommended as part of ppe for dental use during patient care. for a longer useful life of respiratory masks, it is recommended to add a surgical mask together with the use of a face mask. likewise, at the time of placing the mask, it is important to ensure a correct fit and hermetic seal against the skin. likewise, at the time of removal, avoid direct contact with the external part of the mask. finally, as a method of mask sterilization, up to now the use of uvgi, hydrogen peroxide steam, and heat guarantee the preservation of the filtering and structural capacity of masks, providing dentists with adequate protection. nonetheless, more studies are needed for more information on the exact doses of uvgi to implement. profile of dental students about biosafety from biosafety to infection control in dentistry biosafety measures in dental practice: literature review preparation and control of the coronavirus disease 2019 (covid-19) in latin america world health organization. novel coronavirus (2019-ncov) situation report-1 a novel coronavirus from patients with pneumonia in china prevention related to the occupational exposure of health professionals workers in the covid-19 scenario report of the who-china joint mission on coronavirus disease analysis of factors associated with disease outcomes in hospitalized patients with 2019 novel coronavirus disease review of infection control regulations in dental care with an emphasis in hiv/aids surgical masks on the subject of covid-19: some technical aspects role of respirators in controlling the spread of novel coronavirus (covid-19) among dental health care providers: a review facemasks, hand hygiene, and influenza among young adults: a randomized intervention trial a cluster-randomised controlled trial to test the efficacy of facemasks in preventing respiratory viral infection among hajj pilgrims on the use or not of masks, as uncertain as the new coronavirus covid-19: face masks and human-to-human transmission. influenza other respir viruses can n95 respirators be reused after disinfection? how many times covid-19 and dentistry: a review of recommendations and perspectives for latin america covid-19 coronavirus: recommended personal protective equipment for the orthopaedic and trauma surgeon what face mask for what use in the context of covid-19 pandemic? the french guidelines medical mask or n95 respirator: when and how to use? effectiveness of n95 respirators versus surgical masks against influenza: a systematic review and meta-analysis 3m respirator selection guide covid-19 pandemic and personal protective equipment shortage: protective efficacy comparing masks and scientific methods for respirator reuse high-risk aerosol-generating procedures in covid-19: respiratory protective equipment consideration effectiveness of masks and respirators against respiratory infections in healthcare workers: a systematic review and meta-analysis effectiveness of n95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis potential utilities of mask wearing and instant hand hygiene for fighting sars-cov-2 sterilization of n95 respirators: the time for action is upon us! lung india extended use or reuse of n95 respirators during covid-19 pandemic: an overview of national regulatory authorities' recommendations sars-cov-2/covid-19: empfehlungen zu diagnostik und therapie coronavirus disease 19 (covid-19): implications for clinical dental care covid-19 global pandemic planning: decontamination and reuse processes for n95 respirators disinfection of n95 respirators by ionized hydrogen peroxide in pandemic coronavirus disease 2019 (covid-19) due to sars-cov-2 institution of a novel process for n95 respirator disinfection with vaporized hydrogen peroxide in the setting of the covid-19 pandemic at a large academic medical center respiratory protection considerations for healthcare workers during the covid-19 pandemic ultraviolet germicidal irradiation: possible method for respirator disinfection to facilitate reuse during covid-19 pandemic concise communication: covid-19 and the n95 respirator shortage: closing the gap comparison of five bacteriophages as models for viral aerosol studies protecting healthcare workers from sars-cov-2 infection: practical indications dentistry and coronavirus (covid-19) -moral decision-making mask is the possible key for self-isolation in covid-19 pandemic a "paper diaper" in n95 respirator covid-19 and its impact on peruvian dentistry key: cord-266814-0l78gpg3 authors: mondal, a.; das, a.; goswami, r. p. title: utility of cloth masks in preventing respiratory infections: a systematic review date: 2020-05-11 journal: nan doi: 10.1101/2020.05.07.20093864 sha: doc_id: 266814 cord_uid: 0l78gpg3 background: using face masks is one of the possible prevention methods against respiratory pathogens. a number of studies and reviews have been performed regarding the use of medical grade masks like surgical masks, n95 respirators etc. however, the use of cloth masks has received little attention. objectives: the purpose of this review is to analyze the available data regarding the use of cloth masks for the prevention of respiratory infections. we intended to use data from both clinical and non-clinical studies to arrive at our conclusion. methods: we used pubmed, cochrane library and google scholar as our source databases. both clinical and non-clinical studies, which had data regarding the efficacy of cloth masks, were selected. articles not containing analyzable data including opinion articles, review articles etc. were excluded. after screening the search results, ten studies could be included in our review. data relevant to our objective was extracted from each study including clinical efficacy, compliance, filtration efficacy etc. data from some studies were simplified for the purpose of comparison. extracted data was summarized and categorized for detailed analysis. qualitative synthesis of the data was performed. but the heterogeneity between the studies did not allow for a meta-analysis. discussion: the review was limited by a lack of sufficient clinical studies. lack of standardization between studies was another limitation. although cloth masks generally perform poorer than the medical grade masks, they may be better than no masks at all. filtration efficacy varied greatly depending on the material used, with some materials showing a filtration efficacy above 90%. however, leakage could reduce efficacy of masks by about 50%. standardization of cloth masks and appropriate use is essential for cloth masks to be effective. however, result of a randomized controlled trial suggest that they may be ineffective in the healthcare setting. one of the commonly employed methods to prevent the spread of any pandemic caused by air-borne respiratory pathogens is use of physical barrier methods like protective clothing and mask usage. the primary method of transmission of respiratory pathogens especially viral infections is via droplets. physical barriers like masks may have some benefit in preventing such infections by preventing the droplet spread from person to person. at the moment of conducting this review, the covid-19 pandemic has been sweeping through the globe and a number of preventive measures have been implemented including but not limited to social distancing, hand hygiene, respiratory etiquette etc. some countries have even recommended the use of cloth masks for the general population. 1 however, a closer look at the available evidences is necessary regarding the matter of cloth masks. a 2011 systematic review and meta-analysis in the cochrane database for systematic reviews 2 analyzed results of 67 studies on the effect of physical interventions to prevent the spread of respiratory pathogens. data from nine case control studies suggested that physical barriers were effective in this regard. both surgical masks and n95 masks were found to be effective, however there was no information about the efficacy of cloth masks. in the time of a pandemic there is a noted scarcity of resources, which includes medical grade masks like surgical masks and other respirators like n95. in such times of crisis, the policymakers especially in the community setting may seek supplementation of these equipments. hence, whether cloth masks may be used in the place of medical grade masks, needs to be answered. cloth masks are different from medical grade masks. they are not standardized and there is no standard evidence based guidelines for their use in the context of preventing disease transmission. there is a severe dearth of evidence regarding the efficacy of cloth masks in preventing the transmission of respiratory pathogens. moreover, due to their much dissimilarity with the medical grade masks, we cannot extrapolate the evidence from one to the other. hence, although the systematic review of jefferson t et al. 2 concluded that use of masks is likely to be effective in preventing disease transmission, the same cannot be said about the cloth masks without further evidence. therefore, to address this research gap, our study aims to analyze the available evidences to find the utility of cloth masks in preventing respiratory pathogen transmission. since only a handful of clinical studies are available we will also take into account the nonclinical studies which have a direct clinical implication in this matter. the question we seek to answer is stated as follows • is cloth mask useful in preventing respiratory infection? we reported our study in compliance with preferred reporting items for systematic reviews and meta-analyses (prisma) guidelines. 3 we searched the following databases including pubmed, the cochrane library and google scholar. we used the following search terms • pubmed and cochrane library-(mask or masks) and (cloth or fabric or homemade or home-made or (home and made) or improvised) • google scholar-allintitle: mask and (cloth or fabric or homemade or home-made or improvised) two authors, am and ad, performed the search independently and duplicate results were removed. the results were then evaluated for eligibility by two authors independently, first by the titles, then by the abstracts and lastly by the full texts. references from 2 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted may 11, 2020. . each included study were also searched for further relevant studies. the result from each author was compared and any disparity was resolved through discussion among all three authors. the studies meeting the following criteria were considered for inclusion • studies evaluating efficacy of cloth masks in the clinical settings • studies evaluating compliance of the subjects to wearing cloth masks • studies evaluating filtration efficacy of cloth masks • studies evaluating microscopic characters of the cloth masks we excluded the following types of papers • papers on opinions, hypothesis, case reports, case series, letters and editorials • review articles • non-experimental studies such as mathematical modelling • papers with unavailable full text we did not set any time, geographic or language restriction for search results. the translated entries in the databases and online translator tools were used for non-english studies. all studies published till the date of search were considered for inclusion. data from individual studies were extracted for evaluation, including the clinical outcomes, risk ratio of developing respiratory illness, rate of compliance, filtration efficacy and microscopic characteristics. in case of the papers, having only graphical representation of the data, a graph digitizer was used to extract the necessary data. data from some studies were simplified to make them comparable to other studies. the included randomized controlled trials were assessed for risk of bias using the risk of bias tool version 2 by the cochrane collaboration. 4 two authors, am and ad, performed the assessments independently and any disagreement was resolved by discussion. the extracted data was summarized and categorized based on different aspects of the research question. tabulation of data was done when possible. the data from the studies were then compared to each other and analyzed to form a conclusion. the literature search was performed on may 2, 2020 according to the prisma protocol ( figure 1 ). the pubmed search yielded 143 results in total, whereas cochrane library and google scholar produced 140 and 24 results respectively. a total number of 293 studies remained after removing duplicates. after screening, ten studies met our inclusion criteria. among them two papers were randomized controlled trials and eight were non-clinical studies. the randomized controlled trial comparing efficacy of cloth masks with that of surgical masks in preventing infections was performed in vietnam. 5 the second paper used the data from the first trial to assess the compliance of the healthcare workers to cloth masks and surgical masks. 6 seven of the non-clinical studies measured filtration efficacy of cloth masks 7-13 and the remaining study analyzed the microscopic properties of cloth masks. 14 risk of bias assessment of the randomized controlled trials is provided in table 1. however, a meta-analysis could not be performed due to a lack of homogeneity of the available data. maclntyre et al. 5 some concern chughtai et al. 6 some concern table 1 : risk of bias assessment 4 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. only one randomized controlled trial evaluated cloth masks for their efficacy in preventing infection by respiratory pathogens in comparison to surgical masks. this randomized controlled trial 5 by maclntyre et al. had three arms, surgical masks, cloth masks and standard practice. the total number of participants were 1607, all of them healthcare workers. the study found that after four weeks of follow up, the cloth masks performed poorer than the surgical masks in preventing influenza like illness. the relative risk of influenza like illness was 13.25 (95% confidence interval 1.74 to 100.97) compared to the surgical masks on intention-to-treat analysis. however, there was no appreciable difference between cloth masks and surgical masks regarding laboratory confirmed viruses (relative risk 1.66, 95% confidence interval 0.95 to 2.91). the compliance to cloth masks in comparison to surgical masks was assessed by chughtai et al. 6 using the data from the previous randomized controlled trial. compliance was defined as the use of designated masks for 70% of the time while on hospital duties. the authors reported a compliance rate of 56.8% in the cloth mask arm and 56.6% in the surgical mask arm. the multivariate analysis showed a relative risk of 1.02 (95% confidence interval 0.97 to 1.08) which indicates that compliance in both groups was almost identical. however, they also failed to show any association between compliance and the efficacy in preventing infections. seven of the included studies had evaluated the filtration efficacy of different types of cloth masks ( table 2) . four of these studies were conducted in laboratories with mechanical particles or droplet generators. these particles were passed through the mask under examination and filtration efficacy was calculated depending on the percentage of particles blocked by the mask. two studies used healthy volunteers. one of them 8 placed the detector under the mask while it was worn by the subject and counted the ambient particles passing through. in the other study 10 the volunteers coughed into a box with or without masks and the microbes inside the box were then cultured to estimate the filtration efficacy. almost all studies showed that surgical masks and n95 masks were superior to cloth masks, except one. in the study by shakya et al. 11 a certain type of cloth mask performed better than surgical masks and even n95 masks in some cases. n95 also performed poorly in the study by konda et al. 12 when the particle size was less than 300 nm. the study by van der sande et al. 8 measured the filtration efficacy of cloth masks on expulsion of droplets by a person and found it to be about 14%. filtration efficacy of cloth masks varied depending on the material used. a value as low as 9% was obtained while the highest value was 99.5%. as per the available data from the included studies cloth masks had better filtration efficacy in case of larger particles similar to surgical masks and n95 masks. in the study by shakya et al. 11 one of the cloth masks having an exhaust valve performed exceptionally well in case of particles larger than 1 µm in size. it showed a filtration efficacy of 81% compared to 78% efficacy of the surgical mask. konda et al. 12 assessed the filtration efficacy of 15 natural and synthetic fabrics. the best performers in the <300 nm range were the cotton/chiffon hybrid, cotton quilt, cotton/flannel hybrid and cotton/silk hybrid with above 90% for all of them. in the range of >300 nm however, the best performers with >90% efficacy were the double layered and single layered cotton with 600 threads per inch, cotton/chiffon hybrid, cotton-silk hybrid and cotton quilt. two studies evaluated the effect of leakage around the masks on the filtration capacity. in both studies the filtration efficacy dropped significantly in the presence of leakage. 5 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. neupane et al. 14 examined 20 different types of cloth masks under light microscope and found that the smallest pore size was 81 ± 29 µm, whereas the largest pore size was 461 ± 108 µm. the pore density was found to be 12 to 47 pores / 4.5 mm 2 . the surfaces of the cloth masks were distorted significantly under stretch and the pore size increased, but the surgical masks did not show any such effect. the washing and drying of a cloth mask was also observed to gradually decrease its filtration efficacy (r 2 = 0.99). after four cycles of washing and drying the filtration efficacy dropped by about 20%. available clinical data suggests that cloth masks are inadequate in preventing influenza like illness in healthcare settings. however, no relationship was found between compliance and clinical efficacy. filtration efficacy of cloth masks was found to be variable between different types of materials used in cloth masks. filtration efficacy is also reduced significantly by leakage. the microscopic study 14 of the cloth masks revealed that the pore size of cloth masks is larger than 50 µm (smallest pore size 81 ± 29 µm). yang et al. 15 plotted the size distribution of droplets produced by coughing and found three peaks at 1 µm, 2 µm and 8 µm size bands, which are much smaller than the pores in the cloth masks. however, the studies on the filtration efficacy of cloth masks report a decent efficiency of cloth masks in filtering out particulate matters for certain types of fabrics. in some cases, the efficacy of cloth masks has been reported to be higher than 90%. in the study by konda et al. 12 double layered cotton with 600 threads per inch showed a filtration efficacy of 99.5 ± 0.1% in the >300 nm particle range compared to 99.9 ± 0.1% efficacy of n95 masks in the same range. although less than the n95 masks in most cases such high efficiency of some types of cloth masks raises the hope of them being useful against droplet infections. in the filtration efficacy studies the efficiency of the cloth masks in filtering particulate matters remained decent even with the particles smaller than the pore size. this may be due to multiple layers of cloths. the electrostatic forces in the fabric threads may also play a role. 6 all rights reserved. no reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted may 11, 2020. . however, cloth masks are not standardized and there is a wide range of cloth masks available with different quality fabrics. each of these studies used different types of cloth masks. which may explain the apparent disparity among the study results. the cloth masks are also rarely fit tested which causes significant decrease in efficiency due to leakage, which may be up to 50% or even more. 12 in the healthcare setting, cloth masks were found to be inadequate 5 in preventing influenza like illness compared to the surgical masks (relative risk 13.25, 95% confidence interval 1.74 to 100.97). however, the conclusion must be drawn carefully as there was no arm without mask. it is not possible to deduce whether the use of these masks is better than no masks. moreover the filtration test of the cloth masks in that study showed only 3% efficacy, so the poor performance of the cloth masks may have been due to their quality. the study on compliance, 6 however, failed to show any relation between the infection rate and the mask use. this result puts into question whether use of masks has any effect on preventing infection or not. this finding contrasted with a previous cochrane review 2 in 2011. in this review, a meta-analysis of seven case-control studies showed that the odds ratio of mask use vs control was 0.32 (95% confidence interval 0.26 to 0.39) regarding the occurrence of infection by respiratory viruses. but the question of efficacy of masks, as a whole, is beyond the scope this review. despite good filtration efficacy, a poor protective effect against the infection by respiratory pathogens may be explained by a number of reasons. first, the leakage around the masks may contribute significantly in reducing the efficacy. in fact, two of the included studies 7, 12 showed that it may reduce the efficacy by as much as 50%. another possibility is that, despite a decently high efficacy of cloth masks the small amount of particles passing through may be sufficient to cause a clinical infection. however, these issues are also likely to affect the efficacy of medical grade masks. from the analysis of the available evidence, it is clear that further clinical studies are needed to resolve the apparent disparity. if such a trial is conducted it would be necessary to use different types of cloth masks. there is also a lack of study in the community setting. the only available clinical study was done in a healthcare setting and the data cannot be extrapolated for the use of cloth masks in the community. during a pandemic the scarcity of resources might prevent the distribution of surgical masks to the community. the use of cloth masks may arise in times like that. as per the available evidences use of cloth masks may be recommended to the general population. however, it must be ensured that the people using the masks understand its limited efficacy against the infection, otherwise they might fall victim to a false sense of security. use of cloth masks should not lead to a neglect of other infection control measures. evidence 10 shows that cloth masks were also capable of reducing droplet expulsion during coughing compared to the absence of a mask. hence, maximum safety with cloth masks may be obtained if both the infected and the healthy persons were the masks. if cloth masks are recommended for community use, it would perhaps be advisable to standardize the masks with usage of the materials proven to have high filtration efficacy. leakage needs to be minimized as much as possible. the users should also be instructed to use the masks properly and replace them regularly rather than repeatedly using the same mask. in the healthcare setting, use of cloth masks cannot be recommended. the available evidence indicates that cloth masks are grossly ineffective in preventing infection by respiratory pathogens in the healthcare workers. the standard protocol in this context should include surgical masks and respirators like n95. unlike the disposable surgical masks, cloth masks are often washed and dried repeatedly and used for a prolonged period of time. however, the study on the microscopic structure of the cloth masks 14 showed that repeated washing and drying may reduce the quality of the cloth mask, by almost 20% after four such cycles. in the light of this evidence, it may be advisable to change the cloth masks regularly rather than repeated washing. wearing a cloth mask for a prolonged time continuously would also accumulate the respiratory pathogens on the outer surface. this may result in selfcontamination from the mask itself. a study on the surgical masks 16 found that this effect increases with the duration of mask wear. the effect is most likely similar in cloth masks. we need a similar study with the cloth masks to determine their maximum safe period of continuous use. our study had several limitations. the number of clinical studies was very small. also, the results of the included studies were too heterogeneous to allow for a meta-analysis. the paper by shakya et al. 11 only had graphical representation of the data. this data had to be extracted by use of a graph digitizer which maybe prone to some degree of inaccuracy. the lack of standardization of the cloth masks meant that every study used different types of masks, which may lead to noncomparable results and make interpretation difficult. although the filtration efficacy of cloth masks is generally lower compared to the surgical masks and n95 masks, they are capable of filtering out some fraction of particles and hence may be better than using no masks at all. in the community setting cloth mask may be recommended during a pandemic caused by respiratory pathogens if medical grade masks are in short supply. however, the randomized controlled trial showed 5 that cloth masks are likely to be inadequate in the healthcare setting, so it may be advisable to avoid recommending them to the healthcare workers. however, more randomized controlled trials is needed in both the healthcare and the community settings to generate adequate evidence. efficacy of cloth masks varies greatly depending on the materials used, which may be improved by standardization of the manufacturing process of cloth masks. appropriate instructions for their use, proper fitting to avoid leakage and regular change of cloth masks are essential to maximize their protective efficacy. no funding was received for this study. center for disease control and prevention. recommendation regarding the use of cloth face coverings physical interventions to interrupt or reduce the spread of respiratory viruses. cochrane database syst rev the prisma statement for reporting systematic reviews and metaanalyses of studies that evaluate healthcare interventions: explanation and elaboration cochrane collaboration's tool for assessing risk of bias in randomised trials a cluster randomised trial of cloth masks compared with medical masks in healthcare workers rahman b, raina macintyre c. compliance with the use of medical and cloth masks among healthcare workers in vietnam common materials for emergency respiratory protection: leakage tests with a manikin professional and home-made face masks reduce exposure to respiratory infections among the general population simple respiratory protection-evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles testing the efficacy of homemade masks: would they protect in an influenza pandemic? evaluating the efficacy of cloth facemasks in reducing particulate matter exposure aerosol filtration efficiency of common fabrics used in respiratory cloth masks potential utilities of maskwearing and instant hand hygiene for fighting sars-cov-2 optical microscopic study of surface morphology and filtering efficiency of face masks the size and concentration of droplets generated by coughing in human subjects contamination by respiratory viruses on outer surface of medical masks used by hospital healthcare workers non of the authors have any conflict of interests. am conceived and prepared the outline of the study. all authors were involved in the study design. am and ad were involved in the collection of data and served as the first and the second reviewer. rpg acted as the overall supervisor of the study and the third reviewer. the first draft of the manuscript was prepared by am which was then further edited by rpg and ad. key: cord-285425-3v1bid02 authors: macintyre, chandini raina; chughtai, abrar ahmad; rahman, bayzidur; peng, yang; zhang, yi; seale, holly; wang, xiaoli; wang, quanyi title: the efficacy of medical masks and respirators against respiratory infection in healthcare workers date: 2017-08-30 journal: influenza other respir viruses doi: 10.1111/irv.12474 sha: doc_id: 285425 cord_uid: 3v1bid02 objective: we aimed to examine the efficacy of medical masks and respirators in protecting against respiratory infections using pooled data from two homogenous randomised control clinical trials (rcts). methods: the data collected on 3591 subjects in two similar rcts conducted in beijing, china, which examined the same infection outcomes, were pooled. four interventions were compared: (i) continuous n95 respirator use, (ii) targeted n95 respirator use, (iii) medical mask use and (iv) control arm. the outcomes were laboratory‐confirmed viral respiratory infection, influenza a or b, laboratory‐confirmed bacterial colonisation and pathogens grouped by mode of transmission. results: rates of all outcomes were consistently lower in the continuous n95 and/or targeted n95 arms. in adjusted analysis, rates of laboratory‐confirmed bacterial colonisation (rr 0.33, 95% ci 0.21‐0.51), laboratory‐confirmed viral infections (rr 0.46, 95% ci 0.23‐0.91) and droplet‐transmitted infections (rr 0.26, 95% ci 0.16‐0.42) were significantly lower in the continuous n95 arm. laboratory‐confirmed influenza was also lowest in the continuous n95 arm (rr 0.34, 95% ci 0.10‐1.11), but the difference was not statistically significant. rates of laboratory‐confirmed bacterial colonisation (rr 0.54, 95% ci 0.33‐0.87) and droplet‐transmitted infections (rr 0.43, 95% ci 0.25‐0.72) were also lower in the targeted n95 arm, but not in medical mask arm. conclusion: the results suggest that the classification of infections into droplet versus airborne transmission is an oversimplification. most guidelines recommend masks for infections spread by droplets. n95 respirators, as “airborne precautions,” provide superior protection for droplet‐transmitted infections. to ensure the occupational health and safety of healthcare worker, the superiority of respirators in preventing respiratory infections should be reflected in infection control guidelines. there is currently a lack of consensus around the efficacy of medical masks and respirators for healthcare workers (hcws) against influenza, with only five published randomised control trials (rcts) in hcws conducted to date. [1] [2] [3] [4] [5] while n95 respirators have been shown to be superior to medical masks in preventing clinical respiratory infection (cri), influenza illness (ili) and other outcomes, none of the studies were adequately powered to examine laboratory-confirmed influenza. in the smallest of the trials, involving only 32 hcws, there was no difference in the rates of respiratory illnesses between hcws who used medical masks and the control group. 1 a canadian study of 422 hospital nurses compared targeted use of n95 respirators and medical masks and found that the rate of serologically defined influenza was 25% in both arms. 2 however, in the absence of a control arm for comparison, the finding of no difference in outcomes between the intervention arms could represent either equal efficacy or equal inefficacy of the two interventions. the other two published hcw rcts used a more specific and less sensitive definition of influenza based on nucleic acid testing (nat) of respiratory specimens in symptomatic subjects. as such, even these substantially larger rcts were unable to demonstrate any significant difference in influenza infection between n95 respirators and medical masks. 3, 4 finally, a recent study examined the efficacy of cloth masks compared to medical mask and control groups, and found that cloth masks may increase the risk of infection in hcws. 5 guidelines for respiratory protection have been driven by presumed transmission mode alone, and under an assumption that influenza and other pathogens are spread by one mode alone. 6 however, the paradigm of unimodal droplet or airborne spread is based on outmoded experiments from the 1940s, which concluded that only large droplets are found at close proximity to the patient, while small droplet nuclei and airborne particles are found at a longer distance. [7] [8] [9] it has since been shown that both small and large particles can exist at short distances from the patient, and that aerosolised transmission can occur at close proximity. 9 in our two published rcts conducted in china, 3,4 we used the same outcomes, case definitions and measurement tools, and used the same testing methods for a range of different pathogens transmitted by different routes. this afforded an opportunity to pool the data from both trials for improved statistical power to examine the outcomes by pathogens and mode of transmission. the aim of this pooled analysis was to examine the efficacy of medical masks and respirators in hcws against respiratory infection. we pooled the results of our two rcts on mask and respirator use in hospital hcws in beijing, china. the first rct (trial 1) was conducted from december 2008 to january 2009, 3 hcws randomised to: medical mask arm (n = 492), n95 fit-tested arm (n = 461) and n95 non-fit-tested arm (n = 488). the rate of fit-test failure was very low (5/461) in this trial, so data from both n95 arms were combined for analysis. an additional 481 healthcare workers from nine hospitals were recruited to a control arm. these hospitals were purposefully selected as they indicated low levels of routine mask/respirator use during a pretrial assessment. participants in the control arms continued their usual mask wearing practices and were followed using the same protocol as applied to the other arms. 3 the second trial (trial 2) was conducted from 28 december 2009 to 7 february 2010, using the same design. 4 in trial 2, participants were randomised to three arms: medical masks at all times on shift (n = 572), continuous n95 respirators at all times on shift (n = 516) and targeted/intermittent use of n95 respirators only while doing high-risk procedures or barrier nursing of a patient with known respiratory illness (n = 521). fit testing was not performed in the second rct. in both trials, participants were followed for 4 weeks of wearing the medical masks or respirators, and an extra week of non-wearing of masks for the development of symptoms. demographic and clinical data were collected, including gender, age, smoking, vaccination status, pre-existing medical illnesses, hand hygiene and high-risk procedures. pharyngeal swabs were collected from symptomatic participants, and samples were tested at the laboratories of the beijing centers for disease control and prevention. there was no major difference in the products used in both clinical trials. in the first trial, we used medical masks (3m, catalogue number 1820) and n95 fit/ non-fit-tested respirator (3m, catalogue number 9132). the following products were used in the second trial: medical masks (3m, catalogue number 1817) and respirator (3m, catalogue number 1860). the interventions compared in the pooled analysis were as follows: (i) continuous use of n95 respirators (pooled data from both trials -1530 subjects); (ii) targeted n95 respirator use (data from trial 2-516 subjects); (iii) continuous use of medical masks (pooled data from both trials -1064 subjects) and (iv) and a control group (data from trial 1-481 subjects). only laboratory-confirmed outcomes were included in the analysis, which were defined and measured identically in both trials, and the laboratory testing has previously been described. 3, 4 laboratory-confirmed bacteria and viruses identified in participants were categorised according to droplet (n = 285), contact (n = 6) and airborne (n = 3) transmission modes (table s1a) . sixty-one coinfection cases with multitransmission were categorised separately. (table s1a) . as the largest number of confirmed infections was in the droplet category, we conducted a subgroup analysis of droplet-transmitted infections. given there were a large number of rsv cases (n = 33) in our data set and rsv is variously categorised as | 513 either "droplet" 11 or "contact" spread 12 in different guidelines, we performed a sensitivity analysis by including rsv into the droplet transmission category instead of contact. ethics approvals of two clinical trials were obtained from the institutional review board and human research ethics committee of the beijing center for disease prevention and control. we did not involve patients and their families in the design and conduct of the study. we have acknowledged the support of participants, and the results will be published in open access journal. the data sets from the two trials were pooled incorporating the common variables. we calculated the attack rate (proportion of outcome) of each of the four outcomes by the study arms. we conducted a fixed effect individual patient data (ipd) metaanalysis by fitting a multivariable log binomial model, using generalised estimating equation (gee) to account for clustering by hospital/ward. we used a fitted fixed effect model because there are only two trials. two studies were conducted in the same setting with similar participant characteristics, and they examined the same underlying effect. in the analysis, relative risk (rr) was estimated using the control arm as the referent category after adjusting for potential confounders and their interaction terms with a trial id number. the overall rates of seasonal infection were higher in the second trial than the first. the consistency assumption (ie between study homogeneity) for the ipd meta-analysis was tested by fitting an interaction term between trial id and trial arms where a significant interaction is indicative of inconsistency. 13 any interaction term (between trial id and covariates other than trial arm) that was not a confounder was subsequently excluded from the model using backward elimination approach. this approach is described in detailed elsewhere. 4 we repeated the above-described methods for each of the outcomes. after combining the data sets from the two trials, 3591 cases were in the ipd meta-analysis, none of the interaction terms between trial arm and trial id was significant for any of the outcome variables. thus, the consistency assumption for the ipd meta-analysis was satisfied. however, a significant interaction was observed between trial id and hand washing for laboratory-confirmed bacterial colonisation only; therefore, we estimated the rr for trial id stratified by hand washing. in the similar analysis, the risk of influenza was also lower in medical mask arm compared to control; however, the difference was not statistically significant (rr 0.81 and 95% ci 0.25-2.68) arm. table 5 compares the results of this analysis with the individual studies. we demonstrated superior clinical efficacy of continuous use of n95 respirator (also known as "airborne precautions") against infections presumed to be spread by the droplet mode, including influenza. this suggests that transmission is more complex than assumed by traditional classifications, and supports the fact that both large and small droplets are present close to the patient, and that aerosol transmission may occur for presumed "droplet" infections. respirators are designed to provide respiratory protection through filtration and fit, and properly fitted respirators provide better protection compared to medical masks. 3, 4 we could not demonstrate efficacy of medical masks against any outcome, but the non-significant trend appeared to be towards protection. medical masks may well have efficacy, 5 but if so, the degree of efficacy was too small to detect in this study, and larger studies are needed, given the widespread use of these devices in health care. a diagnosis of influenza requires the detection of virus from respiratory specimens, or a fourfold rise in serological titres, both of which are highly resource-intensive and depend on daily subject follow-up and on optimal timing of specimen collection. for all these reasons, the published studies to date have been unable to determine whether there is a difference in efficacy against influenza infection between medical masks and n95 respirators. this study can therefore usefully inform policies for prevention of influenza. in the first rct, compared to medical masks, n95 respirators were found to be protective against cri, but not against ili or laboratoryconfirmed influenza. 3 when compared with the control arm, rates of laboratory-confirmed virus and bacterial colonisation were significantly lower in n95 arm (table 5 ). in the second rct, continuous use of n95 respirators was associated with lower rates of cri and laboratory-confirmed bacterial colonisation compared to the medical mask use. 4 pooled analysis of these studies improved the power to analyse other infectious outcomes by intervention and to allow analysis by mode of transmission. an important finding of this analysis was the efficacy of n95 respirators against droplet-transmitted infections. generally, medical masks are considered sufficient for droplet-transmitted infections such as influenza. 18 however, this study has demonstrated a clear benefit of using n95 respirators (both continuous and targeted) to protect hcws against droplet infections and does not show significant protection of medical masks. in the light of these findings, it may be prudent to use respirators when the transmission mode of a disease is unknown or when hcws exposed to droplet-transmitted infections with a high-case fatality rate. 6 this study has some limitations. firstly, the reporting of the results included in figure 1 is different from the ipd meta-analysis results. this is due to the uneven distribution of randomisation arms and differing seasonal attack rates between the trials. in figure 1 , these between-trial differences were not taken into account. the ipd meta-analysis takes into account of these and gives an unbiased association. secondly, the control arm in trial 1 was not randomised; however, the risk of bias is less due to similar study setting, outcome measures and participant characteristics. moreover, whether infection was acquired in the community or the hospital cannot be determined, but the rct design should result in community exposure being distributed equally across all arms. finally, we categorised pathogens according to various transmission modes, while certain viruses are transmitted via multiple routes. the pooled data were suggestive of an effect of respirators against influenza, but probably did not have enough statistical power for this outcome. the major strength of this study is the use of the same endpoints, measurements and methods in the two trials, which allowed valid pooling of the data. it is a long-held belief in hospital infection control that a mask is adequate for droplet-transmitted infections. we showed that the use of respirators provides better protection against respiratory infections, even those presumed to be spread predominantly by the droplet mode. the targeted use of a respirator was also effective, whereas no efficacy was demonstrated for medical masks alone. however, the trends suggest some degree of protection from medi3. for many infections, more than one mode of transmission is possible, and our data suggest that transmission of infections is more complex than suggested by these paradigms. clinical efficacy data are a higher level of evidence than theoretical paradigms of transmission, and show better protection afforded by respirators. use of surgical face masks to reduce the incidence of the common cold among health care workers in japan: a randomized controlled trial surgical mask vs n95 respirator for preventing influenza among health care workers: a randomized trial a cluster randomized clinical trial comparing fit-tested and non-fit-tested n95 respirators to medical masks to prevent respiratory virus infection in health care workers. influenza other respir viruses a randomized clinical trial of three options for n95 respirators and medical masks in health workers a cluster randomised trial of cloth masks compared with medical masks in healthcare workers respiratory protection for healthcare workers treating ebola virus disease (evd): are facemasks sufficient to meet occupational health and safety obligations? bacteriologic procedures in the evaluation of methods for control of air-borne infection transmission of ebola viruses: what we know and what we do not know health workers need optimal respiratory protection for ebola public health agency of canada. pathogen safety data sheets and risk assessment center for disease control and prevention (cdc). respiratory syncytial virus infection (rsv): transmission and prevention public health agency of canada indirect and mixed-treatment comparison, network, or multiple-treatments meta-analysis: many names, many benefits, many concerns for the next generation evidence synthesis tool prevention strategies for seasonal influenza in healthcare settings infection prevention and control of epidemic-and pandemic-prone acute respiratory infections in health care exposure to influenza virus aerosols during routine patient care measurements of airborne influenza virus in aerosol particles from human coughs guideline for isolation precautions: preventing transmission of infectious agents in health care settings guidance on personal protective equipment to be used by healthcare workers during management of patients with ebola virus disease in u.s. hospitals, including procedures for putting on (donning) and removing (doffing) interim infection prevention and control recommendations for hospitalized patients with middle east respiratory syndrome coronavirus (mers-cov) uncertainty, risk analysis and change for ebola personal protective equipment guidelines ebola and marburg virus disease epidemics: preparedness, alert, control, and evaluation infection prevention and control during health care for probable or confirmed cases of novel coronavirus (ncov) infection centers for disease control and prevention and world health organization. infection control for viral haemorrhagic fevers in the african health care setting facemasks for the prevention of infection in healthcare and community settings availability, consistency and evidence-base of policies and guidelines on the use of mask and respirator to protect hospital health care workers: a global analysis this is pooled analysis of two clinical trials. key: cord-282879-28nhr1hv authors: patel, samir n.; hsu, jason; sivalingam, meera d.; chiang, allen; kaiser, richard s.; mehta, sonia; park, carl h.; regillo, carl d.; sivalingam, arunan; vander, james f.; ho, allen c.; garg, sunir j. title: the impact of physician face mask use on endophthalmitis after intravitreal anti-vascular endothelial growth factor injections date: 2020-09-02 journal: am j ophthalmol doi: 10.1016/j.ajo.2020.08.013 sha: doc_id: 282879 cord_uid: 28nhr1hv purpose: to evaluate the effect of physician face mask use on rates and outcomes of post-injection endophthalmitis. design: retrospective, comparative cohort study methods: . setting: single-center study population: eyes receiving intravitreal anti-vascular endothelial growth factor injections from 7/1/2013 to 9/1/2019. intervention: cases were divided into “face mask group” if face masks were worn by the physician during intravitreal injections or “no talking group” if no face mask was worn but a no talking policy was observed during intravitreal injections. main outcome measures: rate of endophthalmitis, visual acuity, and microbial spectrum. results: of 483,622 intravitreal injections administered, 168 out of 453,460 (0.0371%) cases of endophthalmitis occurred in the “no talking” group, and 9 out of 30,162 (0.0298%) cases occurred in the face mask group (odds ratio, 0.81; 95%ci, 0.41–1.57; p=0.527). sixteen cases of oral flora-associated endophthalmitis were found in the “no talking” group (1 in 28,341 injections) compared to none in the face mask group (p=0.302). mean logmar visual acuity at presentation in cases that developed culture-positive endophthalmitis was significantly worse in the “no talking” group compared to the face mask group (17.1 lines lost from baseline acuity vs 13.4 lines lost; p=0.031), though no difference was observed at six months following treatment (p=0.479). conclusion: physician face mask use did not influence the risk of post-injection endophthalmitis compared to a no talking policy. however, no cases of oral flora-associated endophthalmitis occurred in the face mask group. future studies are warranted to assess the role of face mask use to reduce endophthalmitis risk, particularly due to oral flora. the use of intravitreal anti-vascular endothelial growth factor (anti-vegf) injections has become the standard of care for the treatment of common retinal diseases including neovascular age-related macular degeneration, retinal vein occlusion, and diabetic macular edema. since the introduction of intravitreal anti-vegf therapy, intravitreal injections have become one of the most commonly performed procedures in all of medicine. 1 although these medications have excellent safety profiles, acute bacterial endophthalmitis remains an uncommon but potentially devastating complication. 2 multiple prior studies have evaluated patient-related and procedure-related risk factors associated with post-injection endophthalmitis. [3] [4] [5] [6] [7] in particular, one study found that oral flora-associated endophthalmitis was reduced after instituting a "no talking" policy where speaking was minimized during the procedure. 7 understanding potential risk factors for oral flora-associated endophthalmitis is of particular importance given its poor visual prognosis. [7] [8] [9] [10] surgical face masks reduce transfer of nasopharyngeal flora from respiratory emissions. previous studies demonstrated that surgical masks reduced forward bacterial dispersion into the surgical field. 11, 12 two laboratory investigations involving simulated intravitreal injections suggest that face mask use may reduce bacterial dispersion associated with speech. 13, 14 partly due to this data, some have suggested including face mask use as part of the standard of care for intravitreal injections. 7, 15 however, it is unclear whether decreased bacterial dispersion in these simulations correlates with an impact on clinical practice. both studies also found that maintaining silence during the simulated injection was equally effective as wearing a face mask. 13, 14 however, other studies have suggested that face mask use may increase bacterial dispersion and infection risk. [16] [17] [18] [19] there are no known clinical studies, to our knowledge, investigating the potential impact of physician face mask use during intravitreal injection administration in a clinicbased setting on the rates of endophthalmitis. this lack of data is particularly relevant given that the use of personal protective equipment like face masks has become a standard of care for routine medical care by ophthalmic providers since the covid-19 pandemic. 20 prior to the covid-19 precautions, within our practice, a subset of physicians have consistently worn face masks while performing intravitreal injections, while other physicians have used a no talking technique without face mask use during the procedure. the purpose of this study is to evaluate the rate and outcomes of postinjection endophthalmitis with physician face mask use compared to a no talking policy without face masks. this retrospective, single-center, comparative cohort study received prospective approval from the institutional review board at wills eye hospital. data were collected in accordance with health insurance portability and accountability act of 1996 guidelines, and the study conformed to the tenets of the declaration of helsinki. billing records and j o u r n a l p r e -p r o o f endophthalmitis logs were used to identify patients who developed endophthalmitis following anti-vegf injections. billing data was used to determine the total number of intravitreal injections, patients, type of anti-vegf injection (bevacizumab, ranibizumab, and aflibercept) used, gender, age, and indication for treatment. charts of all patients who were treated for endophthalmitis were reviewed, and the diagnosis was confirmed. recorded data included date of causative injection; date of tap and injection and/or vitrectomy; best available visual acuity (va) based on the better of habitual correction or pinhole testing before causative injection, at time of tap and inject and/or vitrectomy, at 6 months post-procedure, and at last follow-up; and microbial culture results. physician face mask use was determined by a survey of physician practice patterns. all patients diagnosed with presumed infectious endophthalmitis following an intravitreal injection of bevacizumab, ranibizumab, or aflibercept were included in this study. dates of inclusion were july 1, 2013 to september 1, 2019. endophthalmitis was defined as patients who presented with a clinical suspicion that was high enough to warrant either intravitreal antibiotic injection with vitreous/aqueous tap or pars plana vitrectomy with injection of antibiotics. in general, these patients presented with decreased visual acuity and pain, and had signs of intraocular inflammation on examination (generally ≥2+ anterior segment cellular reaction and/or posterior segment vitritis). culture-positive endophthalmitis was defined as any patient with bacterial growth on culture or a positive gram stain from a vitreous or anterior chamber tap. a culture was considered to be oral flora-associated when enterococcus or streptococcus species was grown on culture. endophthalmitis was considered culture-negative when both the gram stain and culture plates were negative. patients with presumed inflammatory endophthalmitis treated with topical steroids without additional interventions were excluded. all intravitreal anti-vegf injections were performed in office-based settings, either in a designated procedure room or in a clinical room where the exam was conducted. all eyes were routinely prepared with topical anesthetic. no physicians routinely used lidocaine gel, topical pledgets, or subconjunctival lidocaine for anesthesia. after ocular anesthesia, all eyes received topical 5% povidone-iodine at least 60 seconds prior to injection, and povidone-iodine administration was repeated just prior to injection at physician discretion. injections were performed with a 30-gauge needle for ranibizumab and aflibercept injections, or 31-gauge needle for bevacizumab injections, and inserted 3.5 -4mm from the limbus. lid retraction was achieved through manual lid retraction with no routine use of lid speculum by any of the providers. surgical gloves, surgical caps, and sterile drapes were not used by physician providers for intravitreal injection administration during the study period. injection techniques were not altered during the study period and were otherwise similar between the two groups (supplementary table 1 available at ajo.com). for the "no talking" group, all injections were administered under a strict policy of silence in which the physician, patient, and others in the room including technicians and family members did not speak during the injection procedure. during the informed consent portion of the procedure, patients are informed of the importance of minimizing speech during the procedure prior to entering the injection room. families are asked to not come into the injection room unless required for certain reasons such as help with mobility as their presence may encourage conversation. technicians are trained not to talk during preparation of the injection or during the procedure. physicians do not talk during the procedure except to cue the patient to look in a certain direction prior to uncapping the injection needle. when speaking close to the patient, physicians directed their faces away from the eye to be injected. for the face mask group, a subset of physicians wore a surgical mask (procedure mask mckesson pleated earloops #91-2002, mckesson, irving, tx) when administrating an intravitreal injection. additionally, technicians who assisted with drawing drug from the vial, placing the needle on a prefilled syringe, or assisting with lid retraction wore a face mask. during the timeframe of the study, patients did not wear face masks during the injection administration. patients and others in the room were still asked not to speak during the procedure as per the "no talking" policy above, but the physician could speak to give instructions and reassurance. all eyes developing presumed infectious endophthalmitis immediately underwent a pars plana vitreous tap with aspiration or anterior chamber paracentesis with injection of intravitreal antibiotics or consideration for immediate pars plana vitrectomy with vitreous culture and intravitreal antibiotics. patients typically received intravitreal vancomycin (1mg/0.1ml) and ceftazidime (2mg/0.1ml). intravitreal amikacin (400μg/0.1ml) was substituted for ceftazidime for patients with penicillin allergy at the discretion of the treating physician. a subset of patients did not have microbiologic specimens sent for processing if they were being treated at a satellite office without immediate access to a microbiology facility. patients were variably prescribed cycloplegic agents, topical antibiotics, and topical steroid drops based on physician discretion. all data were analyzed using statistical software (ibm spss 25 statistics, armonk, ny, usa). the primary outcome was the rate of endophthalmitis following intravitreal injection in the face mask group compared to the "no talking" group. the secondary outcomes were va and microbial spectrum of culture-positive cases. va at 6 months was used for the analysis based on prior studies. 21 snellen va was converted to logmar equivalent for the purpose of statistical analysis. as established by prior studies, 22,23 vision levels of counting fingers, hand motion, light perception, and no light perception were assigned va values of 1.0/200, 0.5/200, 0.25/200, and 0.125/200 (logmar equivalent 2.3, 2.6, 2.9, 3.2 respectively). for categorical variables, significant differences between groups were analyzed using a pearson's chi-squared test or fisher's exact test. for continuous variables, significant differences between groups were analyzed using two sample t-test, mann-whitney u test, or analysis of variance with a tukey's honest significant difference post-hoc test. statistical significance was considered to be a 2-sided p value < 0.05. during the study period, 20 physicians contributed cases with a mean (sd) 21,279 (12,438) (range, 704 -41,672) injections per physician. a total of 483,622 intravitreal anti-vegf injections (67,578 bevacizumab, 267,002 ranibizumab, and 149,042 aflibercept) were performed with 453,460 injections in the "no talking" group and 30,162 injections in the face mask group. overall, a total of 177 cases of suspected endophthalmitis after intravitreal injection were identified (0.036%; 1 in 2732 injections). over the six-year study period, the annualized rate of post-injection endophthalmitis ranged from 0.0295% (1 in 3386 injections) to 0.0431% (1 in 2319 injections) with no significant difference among the annualized rates (p = 0.933). cultures were performed in 128 of these cases, and mean follow-up for all suspected endophthalmitis cases was 32.5 months (range, 14 days -80.5 months). mean (sd) duration of follow-up was 27.7 (15.8) months (range, 0.5 -80.5 months) for the face mask group and 32.7 (21) months (range, 9 -53 months) for the "no talking" group (p = 0.380). in the "no talking" group, suspected endophthalmitis occurred in 168 cases of 453,460 injections (0.0371%; 1 in 2,699 injections), of which 47 cases were culturepositive ( table 1 ). the most common causative organism was staphylococcus epidermidis in 18 cases. there were 16 cases of oral flora-associated endophthalmitis (0.00353%; 1 in 28,340 injections), and causative organisms included 6 cases of streptococcus mitis, 5 cases of streptococcus viridians, 2 cases of streptococcus pneumoniae, and 3 cases of undifferentiated streptococcus. in the face mask group, suspected endophthalmitis occurred in 9 cases of 30,162 injections (0.0298%; 1 in 3,351 injections) of which 5 cases were culture-positive (table 1 ). causative organisms included 3 cases of gram-positive cocci (by stain), 1 case of staphylococcus epidermis, and 1 case of staphylococcus aureus. there were no cases of oral flora-associated endophthalmitis. overall, patients with presumed endophthalmitis presented an average of 5.54 days after intravitreal anti-vegf injection (range, 1 -29 days). the vast majority of cases presented within 7 days of intravitreal injection (81.4%). patients in the face mask group presented an average of 6.3 days after injection compared to an average of 5.5 days in the "no talking" group (p = 0.484). of the cases sent for culture, in the face mask group, 5/7 (71%) cases were culture-positive compared to 47/119 (39%) endophthalmitis cases in the "no talking" group (p = 0.124). endophthalmitis cases in the face mask group were oral floraassociated in 0/9 (0%) cases compared to 16/119 (13%) cases for the "no talking" group (p = 0.306). of the 30,162 injections in the face mask group, 4,100 (14%) were bevacizumab, 16,611 (55%) were aflibercept, and 9,451 (31%) were ranibizumab. of the 453,460 injections in the "no talking" group, 63,478 (14%) were bevacizumab, 132,431 (29%) were aflibercept, and 257,551 (57%) were ranibizumab. compared to the "no talking" group, the face mask group was more likely to use aflibercept (p < 0.001) and less likely to use ranibizumab (p < 0.001). overall, there were 80 cases of endophthalmitis after ranibizumab injection (0.029%; 1 in 3337 ranibizumab injections), 75 cases of endophthalmitis after aflibercept injection (0.05%; 1 in 1987 aflibercept injections), and 22 cases of endophthalmitis after bevacizumab injection (0.03%; 1 in 3071 bevacizumab injections). endophthalmitis cases were associated with ranibizumab in 80/177 (45%) cases, aflibercept in 75/177 (42%) cases, and bevacizumab in 22/177 (12%) cases. endophthalmitis cases in the "no talking" group were associated with bevacizumab in 21/168 (13%) cases, aflibercept in 68/168 (41%) cases, and ranibizumab in 79/168 (47%) cases. endophthalmitis cases in the face mask group were associated with bevacizumab in 1/9 (11%) cases, aflibercept in 7/9 (78%) cases, and ranibizumab in 1/9 (11%) cases. there was no significant difference in the risk of endophthalmitis between the face mask group and the "no talking" group based on drug type (table 1) . overall average baseline va at the causative injection prior to endophthalmitis was logmar 0.60 (approximately 20/80) with no significant difference between the face mask group (logmar 0.46; approximately 20/60) and the "no talking" group (logmar 0.61; approximately 20/80) (p = 0.453) ( table 2 ). at 6-months follow-up, average va was logmar 0.842 (approximately 20/140) for the face mask group vs. logmar 1.06 (approximately 20/230) for the "no talking" group (p = 0.500). for the face mask group, 0/9 (0%) cases had a va of count fingers or worse at 6-months follow-up compared to 24/168 (15%) for the "no talking" group (p = 0.205). at 6-months follow up, 3/9 (33%) cases in the face mask group lost 3 or more lines of va from baseline compared to 63/168 (40%) cases in the "no talking" group (p = 0.685). at last follow-up, average va was logmar 1.08 (approximately 20/240) for the face mask group vs. logmar 1.17 (approximately 20/300) for the "no talking" group (p = 0.793). for the face mask group, 1/9 (11%) cases had a va of count fingers or worse at last follow-up compared to 36/168 (22%) for the "no talking" group (p = 0.454). average va at presentation for culture-positive endophthalmitis cases was logmar 1.58 (approximately 20/760) in the face mask group compared to logmar 2.29 (approximately 20/4000) in the "no talking" group (p = 0.036) ( table 3 ). at 6-months follow-up, average va for the culture-positive endophthalmitis cases was logmar 0.868 (approximately 20/150) in the face mask group vs. logmar 1.53 (approximately 20/700) in the "no talking" group (p = 0.157). for the culture-positive endophthalmitis cases in the face mask group, 0/5 (0%) cases had a visual acuity of count fingers or worse at 6months follow-up compared to 11/47 (27%) for the "no talking" group (p = 0.184) furthermore, at 6-months follow up, 2/5 (40%) cases in the culture-positive face mask group lost 3 or more lines of va from baseline compared to 27/47 (66%) cases in the culture-positive "no talking" group (p = 0.258). at last follow-up, average va for culture-positive endophthalmitis cases was logmar 1.65 (approximately 20/900) in the "no talking" group vs. logmar 1.22 (approximately 20/330) in the face mask group (p = 0.383). for the culture-positive endophthalmitis cases in the face mask group, 1/5 (20%) cases had a va of count fingers or worse at last follow-up compared to 17/47 (37%) for the "no talking" group (p = 0.451). overall, visual outcomes were significantly worse for culture-positive and oral flora-associated endophthalmitis cases. comparing vision loss from baseline, at 6months follow up, oral flora-associated cases lost an average of 17 lines of visual acuity, non-oral flora-associated culture-positive cases lost 9.1 lines of visual acuity, and culture-negative cases lost 2.9 lines of visual acuity (p < 0.001). this study examined the impact of physician face mask use on the rates and outcomes of endophthalmitis after intravitreal anti-vegf injections. in this single-center study of 483,622 intravitreal injections, we found that physician face mask use did not affect the overall rate of post-injection endophthalmitis. injection techniques for both the face mask and "no talking" groups were similar. however, the injecting physicians in the face mask group likely did not uniformly adhere to a strict policy of silence for all people in the room during the procedure compared to the physicians in the "no talking" group. in spite of this, no cases of oral flora-associated endophthalmitis were observed in the face mask group. although all forms of endophthalmitis are visually threatening, oral floraassociated endophthalmitis is associated with a particularly poor visual prognosis. [8] [9] [10] therefore, there is significant interest in understanding potential risk factors and prophylaxis measures for reducing the incidence of oral flora-associated endophthalmitis. a meta-analysis of the literature covering 105,536 intravitreal injections from 2005 to 2009 found that streptococcal species were three times more likely to be the causative organism in post-injection endophthalmitis cases than in intraocular surgeries in which a surgical mask is typically worn. 24 furthermore, prior studies have established that oral flora-associated endophthalmitis may be reduced with the implementation of a strict "no-talking" policy by the physician and patient during intravitreal injection administration. 7,10 refraining from speaking during an intravitreal injection is thought to minimize the potential to contaminate the uncapped needle or conjunctival surface with oral flora immediately before or during the injection. similarly, face mask use by the physician administering the injection may serve to further limit bacterial dispersion during speech. within the neurology literature, multiple outbreaks of iatrogenic oral flora associated meningitis have been reported. as a result, face mask use has become the standard of care for any clinician performing spinal injections. [25] [26] [27] in one case of iatrogenic meningitis, the causative bacteria was genotyped and shown to be identical to that of a throat swab taken from the neurologist who performed the lumbar puncture. 25 within ophthalmology, an in vitro study involving 10 surgeons and 4 simulated intravitreal injection scenarios found that the rate of oral flora bacteria was significantly reduced when speaking with face masks compared to speaking without face masks. 14 furthermore, another in vitro study of 15 volunteers who underwent simulated intravitreal injection administrations demonstrated significantly more bacterial dispersion occurred when speaking without a face mask compared to speaking while wearing a face mask. 13 however, there was no significant difference in bacterial dispersion when speaking with a face mask compared to not speaking without a face mask (simulating a "no-talking" policy). these in vitro studies correlate with our study findings as all intravitreal injections were administered with either a "no-talking" policy or face mask use by the physician. some studies have suggested that the presence of a beard 17 or the tendency to excessively move one's face beneath a surgical mask 16,17 may increase bacterial dispersion and shedding, presumably from the beard and facial skin. in addition, other studies have suggested that extended use of the same face mask may increase infectious risk as the external surface can function as a fomite. 19 furthermore, physicians speaking with a loose fitting face mask may result in upward or downward bacterial dispersal. 18 collectively, these concerns may explain why the majority of retina physicians surveyed in two recent studies did not wear face masks during intravitreal injections. 28, 29 at a minimum, our study findings suggest that physician face mask use does not increase the risk of post-injection endophthalmitis and may be equivalent to a strict "no talking" policy. these findings are particularly relevant as routine use of face masks by physicians has exponentially increased with the emergence of the covid-19 pandemic, and it is unclear what the duration of these precautions will be. 20 although this study focused on the impact of physician and technician assistant face mask use, current covid-19 guidelines recommend universal face mask protocols for all individuals in the injection room which includes the patient. with regard to patient face mask use, it is possible that bacterial dispersion around the edges of the face mask may be directed towards the eye, which could potentially increase the risk of endophthalmitis. indeed, current guidelines from the center for disease control and prevention recommend cloth face covering, which may not adhere to the face as well. 30 further studies are indicated to understand the effects of universal face mask use on rates of various types of endophthalmitis. overall, va outcomes following endophthalmitis were similar in the face mask group compared to the "no talking" group. va at the causative injection, endophthalmitis presentation, and six months following treatment were similar between the two groups. patients in the "no talking" group were more likely to have a visual acuity of cf or worse at 6 months compared to the face mask group (15% vs 0%), though these findings were not statistically significant. regardless of face mask use, our findings were similar to prior studies that have established that visual outcomes are worse for culture-positive cases compared to culture-negative cases. 6, 31 when assessing culture-positive endophthalmitis cases, visual outcomes at endophthalmitis presentation were worse for the "no talking" group with a mean loss of 17.1 lines of vision from baseline acuity compared to a loss of 13.4 lines for the face mask group. furthermore, at 6-months follow up, patients in the "no talking" group were more likely to have a va of cf or worse compared to the face mask group (27% vs 0%), though these findings were not statistically significant. strengths of the study include the large number of intravitreal injections from a single institution with a standardized injection protocol, including injection technique and preparation, amongst multiple retina specialists. endophthalmitis following intravitreal injection is an uncommon event with reported incidence rates ranging from as high as 1 in approximately 500 injections to as low as 1 in 19,000 injections with the majority of large recent studies reporting an incidence rate of 1 in 2000 -3000 injections. 5,6,21,31-34 . therefore, any prophylaxis measure to potentially lower the risk of endophthalmitis requires an assessment of a large number of intravitreal injections to achieve adequate power to detect a difference. although we report one of the largest single center studies of post-injection endophthalmitis, our study findings may be limited by the study's imbalanced sample size with 30,162 injections in the face mask group compared to 453,460 injections in the "no talking" group. assuming the risk of oral flora-associated endophthalmitis is 1 in 28,340 injections as reported in this study, and that face mask use may reduce the risk of oral flora-associated endophthalmitis to 1 in 100,000 injections, a study would need 993,182 injections to be sufficiently powered to detect a j o u r n a l p r e -p r o o f significant difference between the two groups with a confidence of 0.95 and power of 0.8. ideally, a randomized controlled study could evaluate the risk of endophthalmitis with and without physician face mask use; however, the low incidence of endophthalmitis makes such a study prohibitive. furthermore, the granularity of physician-specific practice patterns, like face mask use, may not be captured in large-scale insurance claims databases or clinical registries. another limitation is the imbalance in medication distribution as the face mask group was more likely to use aflibercept and less likely to use ranibizumab compared to the "no talking" group. these findings may be particularly relevant as the prefilled syringe use for ranibizumab was introduced during the study period, and prior studies have reported prefilled syringes may reduce the risk of endophthalmitis. 6, 35 furthermore, during the study period, there was a clustered spike in cases with intraocular inflammation after intravitreal aflibercept injections, 36 which may explain the increased proportion of endophthalmitis associated with aflibercept compared to ranibizumab or bevacizumab in this study. the authors' standard practice is to have a low threshold to administer intravitreal antibiotics whenever the examining physician believes there is a possibility the case could represent infectious endophthalmitis; however, when sterile inflammation is suspected, topical medications alone were typically prescribed. regardless, there were no differences in endophthalmitis risk between the face mask group and "no talking" group based on drug type. another limitation is that microbiologic cultures were obtained in 128 of 177 (72%) cases. however, there were similar rates between the two groups as cultures were performed in 121 of 168 (72%) cases for the "no talking" group and 7 of 9 cases (77%) for face mask group (p > 0.99). recent studies have suggested that culture results have limited impact on clinical management. 31, 37 furthermore, another limitation is that a positive gram stain was considered culture-positive even if there was no bacterial growth on culture. however, prior studies have suggested that any bacteria detected on gram stain of a sterile site specimen, such as vitreous or aqueous samples, should be considered significant. 38 in addition, a culture result was considered to be oral flora-associated when enterococcus or streptococcus species was grown, which may not represent all potential oral flora. however, there were no cultures that grew other common oral flora including lactobacilli, corynebacteria, or bacteroides in either group. furthermore, streptococcal associated post-injection endophthalmitis is of particular concern given the poor visual prognosis relative to other forms of endophthalmitis. 7-10 additional limitations of this study are inherent in its retrospective nature. it is possible that patients could have developed endophthalmitis and sought treatment at an outside institution, although it is unlikely given the tertiary care nature of our institution. in summary, our study indicates that physician face mask use did not influence the risk of endophthalmitis or visual outcomes compared to a strict no talking policy during the injection procedure. no cases of oral flora-associated endophthalmitis occurred in the group in which the injecting physician wore a face mask though this study was underpowered to detect a difference. these findings are particularly relevant as routine use of face masks by retina specialists has increased with the emergence of the covid-19 pandemic. however, it is important to note that patients in the face mask group did not wear a mask which is unlike the current universal face mask protocols in place. additional studies are warranted to assess the potential role of face mask use to reduce the risk of endophthalmitis, particularly those due to oral flora. table 3 . visual acuity outcomes for culture-positive endophthalmitis after intravitreal anti-vascular endothelial group factor injection in the face mask group vs. "no talking" group this study evaluated the rate of post-injection endophthalmitis with physician face mask use compared to a "no talking" policy without face mask use. in evaluating 483,622 intravitreal injections, physician face mask use did not reduce the rate of post-injection endophthalmitis compared to a "no talking" policy. no cases of oral flora-associated endophthalmitis were identified with physician face mask use. trends of anti-vascular endothelial growth factor use in ophthalmology among privately insured and medicare advantage patients international practice patterns for the management of acute postsurgical and postintravitreal injection endophthalmitis: european vitreo-retinal society endophthalmitis study report 1 endophthalmitis following intravitreal injections performed in the office versus operating room setting outcomes and risk factors associated with endophthalmitis after intravitreal injection of antivascular endothelial growth factor agents the role of topical antibiotic prophylaxis to prevent endophthalmitis after intravitreal injection the impact of prefilled syringes on endophthalmitis following intravitreal injection of ranibizumab effect of a strict 'no-talking' policy during intravitreal injection on post-injection endophthalmitis microbial spectrum and outcomes of endophthalmitis after intravitreal injection versus pars plana vitrectomy endophthalmitis after intravitreal injection: the importance of viridans streptococci endophthalmitis following intravitreal injection effect of surgical mask position on bacterial contamination of the operative field unmasking the surgeons: the evidence base behind the use of facemasks in surgery bacterial dispersal associated with speech in the setting of intravitreous injections reducing oral flora contamination of intravitreal injections with face mask or silence endophthalmitis after intravitreal injections: should the use of face masks be the standard of care? mask wiggling as a potential cause of wound contamination the effect of facial hair and sex on the dispersal of bacteria below a masked subject surgical face masks and downward dispersal of bacteria surgical masks as source of bacterial contamination during operative procedures preparedness among ophthalmologists: during and beyond the covid-19 pandemic long-term visual outcomes and clinical features after anti-vascular endothelial growth factor injection-related endophthalmitis functional status and quality of life measurement among ophthalmic patients novel method for analyzing snellen visual acuity measurements meta-analysis of endophthalmitis after intravitreal injection of antivascular endothelial growth factor agents: causative organisms and possible prevention strategies iatrogenic meningitis by streptococcus salivarius following lumbar puncture iatrogenic meningitis: the case for face masks guideline for isolation precautions: preventing transmission of infectious agents in healthcare settings current practice preferences and safety protocols for intravitreal injection of anti-vascular endothelial growth factor agents real-world trends in intravitreal injection practices among american retina specialists use of cloth face coverings to help slow the spread of covid-19 changes in management based on vitreous culture in endophthalmitis after intravitreal anti-vascular endothelial growth factor injection trends in vitreoretinal procedures for medicare beneficiaries eliminating antibiotic prophylaxis for intravitreal injections: a consecutive series of 18,839 injections by a single surgeon endophthalmitis: then and now association of acute endophthalmitis with intravitreal injections of corticosteroids or anti-vascular growth factor agents in a nationwide study in france aflibercept-related sterile intraocular inflammation outcomes endophthalmitis after cataract surgery: changes in management based on microbiologic cultures the spinal tap: a new look at an old test key: cord-269665-byuv48wi authors: macintyre, chandini raina; wang, quanyi; cauchemez, simon; seale, holly; dwyer, dominic e.; yang, peng; shi, weixian; gao, zhanhai; pang, xinghuo; zhang, yi; wang, xiaoli; duan, wei; rahman, bayzidur; ferguson, neil title: a cluster randomized clinical trial comparing fit‐tested and non‐fit‐tested n95 respirators to medical masks to prevent respiratory virus infection in health care workers date: 2011-01-27 journal: influenza other respir viruses doi: 10.1111/j.1750-2659.2011.00198.x sha: doc_id: 269665 cord_uid: byuv48wi please cite this paper as: macintyre et al. (2011) a cluster randomized clinical trial comparing fit‐tested and non‐fit‐tested n95 respirators to medical masks to prevent respiratory virus infection in health care workers. influenza and other respiratory viruses doi: 10.1111/j.1750‐2659.2010.00198.x. background we compared the efficacy of medical masks, n95 respirators (fit tested and non fit tested), in health care workers (hcws). methods a cluster randomized clinical trial (rct) of 1441 hcws in 15 beijing hospitals was performed during the 2008/2009 winter. participants wore masks or respirators during the entire work shift for 4 weeks. outcomes included clinical respiratory illness (cri), influenza‐like illness (ili), laboratory‐confirmed respiratory virus infection and influenza. a convenience no‐mask/respirator group of 481 health workers from nine hospitals was compared. findings the rates of cri (3·9% versus 6·7%), ili (0·3% versus 0·6%), laboratory‐confirmed respiratory virus (1·4% versus 2·6%) and influenza (0·3% versus 1%) infection were consistently lower for the n95 group compared to medical masks. by intention‐to‐treat analysis, when p values were adjusted for clustering, non‐fit‐tested n95 respirators were significantly more protective than medical masks against cri, but no other outcomes were significant. the rates of all outcomes were higher in the convenience no‐mask group compared to the intervention arms. there was no significant difference in outcomes between the n95 arms with and without fit testing. rates of fit test failure were low. in a post hoc analysis adjusted for potential confounders, n95 masks and hospital level were significant, but medical masks, vaccination, handwashing and high‐risk procedures were not. interpretation rates of infection in the medical mask group were double that in the n95 group. a benefit of respirators is suggested but would need to be confirmed by a larger trial, as this study may have been underpowered. the finding on fit testing is specific to the type of respirator used in the study and cannot be generalized to other respirators. trial registration australian new zealand clinical trials registry (anzctr), actrn: actrn12609000257268 (http://www.anzctr.org.au). background we compared the efficacy of medical masks, n95 respirators (fit tested and non fit tested), in health care workers (hcws). methods a cluster randomized clinical trial (rct) of 1441 hcws in 15 beijing hospitals was performed during the 2008 ⁄ 2009 winter. participants wore masks or respirators during the entire work shift for 4 weeks. outcomes included clinical respiratory illness (cri), influenza-like illness (ili), laboratoryconfirmed respiratory virus infection and influenza. a convenience no-mask ⁄ respirator group of 481 health workers from nine hospitals was compared. findings the rates of cri (3ae9% versus 6ae7%), ili (0ae3% versus 0ae6%), laboratory-confirmed respiratory virus (1ae4% versus 2ae6%) and influenza (0ae3% versus 1%) infection were consistently lower for the n95 group compared to medical masks. by intentionto-treat analysis, when p values were adjusted for clustering, nonfit-tested n95 respirators were significantly more protective than medical masks against cri, but no other outcomes were significant. the rates of all outcomes were higher in the convenience no-mask group compared to the intervention arms. there was no significant difference in outcomes between the n95 arms with and without fit testing. rates of fit test failure were low. in a post hoc analysis adjusted for potential confounders, n95 masks and hospital level were significant, but medical masks, vaccination, handwashing and high-risk procedures were not. interpretation rates of infection in the medical mask group were double that in the n95 group. a benefit of respirators is suggested but would need to be confirmed by a larger trial, as this study may have been underpowered. the finding on fit testing is specific to the type of respirator used in the study and cannot be generalized to other respirators. the current influenza a h1n1 2009 virus pandemic, 1 the ongoing zoonotic transmission of influenza a h5n1 and the emergence of oseltamivir-resistant seasonal influenza a h1n1 are threats to human health. hospital health care workers (hcws) are key to effective pandemic response and the capacity of health care systems. respiratory protec-tion is one of the key non-pharmaceutical interventions for protection of hcws. nosocomial influenza and other outbreaks result in significant morbidity and costs 2,3 and can occur in the absence of community epidemics. 4 during outbreaks of infectious diseases, hospitals may amplify virus transmission, as demonstrated during severe acute respiratory syndrome (sars). 5 furthermore, anticipated antiviral shortages and original article delays in vaccine development make non-pharmaceutical interventions crucial. there are gaps in knowledge about prevention of influenza by medical masks and respirators. there are several prospective, randomized controlled trials on the use of handwashing, [6] [7] [8] but only two trials on the use of medical masks ⁄ respirators in households. 9, 10 in one of these studies, we showed that medical masks ⁄ respirators in compliant users in the household setting were associated with reductions in the risk of influenza-like illness (ili)associated infection. 10 to date, there is one small randomized controlled trial (rct) of medical masks compared to respirators in hcws 11 which found no difference, but lacked a control arm. medical masks are not designed to provide respiratory protection. 12 they have consistently lower filtration efficiency when compared to respirators, which are designed specifically for respiratory protection. [13] [14] [15] medical masks were designed to prevent wound contamination when worn by the surgeon; however, three rcts failed to show efficacy against their intended design. [16] [17] [18] the aim of this study was to determine the efficacy of medical masks compared to fit-tested and non-fit-tested n95 respirators in hcws in the prevention of disease because of influenza and other respiratory viruses. a prospective, cluster randomized trial of medical mask and respirator use in frontline hcws was conducted from december 2008 to january 2009 in beijing, china. we initially aimed to determine the efficacy of two different kinds of respiratory protection (n95 respirators and medical masks) during the influenza season compared to each other and compared to a no-mask group. however, although we intended to have a randomized control group, this was not acceptable to the chinese irb, who felt it would be unethical to assign hcws randomly to not wear a mask, given mask use was widespread in chinese hospitals that were included in the randomization. as such, we studied a convenience-selected no-mask group of hcws who did not wear a mask. these hcws were selected from other hospitals where mask wearing was not routine during the study period. absence of randomization in the no-mask group meant that we eventually had to restrict the primary analysis of the trial to the comparison of the efficacy of n95 respirators and medical masks with each other. participants were hospital hcws aged ‡18 years from the emergency departments and respiratory wards of 15 hospitals. these wards were selected as high-risk settings in which repeated and multiple exposures to respiratory infections are expected. we also monitored all participating wards by active surveillance for clinically compatible illness, including in the no-mask group, for outbreaks of respiratory infection in patients during the study period, and none was detected. all hospitals were large, tertiary hospitals in urban beijing, and there was no variation in the start of the influenza season within this geographic area. recruitment commenced on the 1 december 2008 and final follow-up was completed on 15 january 2009. the study protocol was approved by the institutional review board and human research ethics committee of the beijing ministry for health. verbal informed consent was provided by participants, and they were provided written information about the study. the nine hospitals in the convenience no-arm group were not part of the randomization, but hcws in those hospitals were selected from the same type of wards as the intervention arms (emergency departments and respiratory wards). they were followed up in the same way as the trial participants for development of infections. the unit of randomization was hospitals. hospitals were randomized to one of three intervention arms: (i) medical masks (3mô medical mask, catalogue number 1820, st paul, mn, usa); (ii) n95 fit-tested mask (3mô flat-fold n95 respirator, catalogue number 9132) and (iii) n95 nonfit-tested mask (3mô flat-fold n95 respirator, catalogue number 9132). figure 1 outlines the recruitment and randomization (using a secure computerized randomization program) process. a pre-study assessment of hospital infection control levels determined that the hospitals had sufficient diversity to warrant stratified randomization by size of hospital and level of infection control. this assessment measured ventilation, spatial dimensions, bedding configuration, handwashing facilities and personal protective equipment use. the ministry of health in 1989 categorizes hospitals in china into three levels (level 3 is the highest) depending on their level of sophistication, equipment and staff ⁄ bed numbers. fifteen hospitals were randomized -five level 2 and ten level 3. (i) clinical respiratory illness (cri), 19 defined as two or more respiratory or one respiratory symptom and a systemic symptom; (ii) ili, defined as fever ‡38°c plus one respiratory symptom (i.e. cough, runny nose, etc.); (iii) laboratory-confirmed viral respiratory infection (detection of adenoviruses, human metapneumovirus, coronavirus 229e ⁄ nl63, parainfluenza viruses 1, 2 and 3, influenza viruses a and b, respiratory syncytial virus a and b, rhinovirus a ⁄ b and coronavirus oc43 ⁄ hku1 by multiplex pcr); (iv) laboratory-confirmed influenza a or b and (v) adherence with mask ⁄ respirator use. the choice of a relatively broad cri definition was dictated by our interest in interrupting transmission of a wide range of respiratory viruses, which in adults may or may not be accompanied by fever. also, all respiratory pathogens share a similar transmission mechanism namely aerosol, droplet and fomite spread, although the relative role of these factors may vary between different viruses and in different clinical situations. other endpoints included adverse effects, measured using a semi-structured questionnaire and adherence. any nurse, doctor or ward clerk who worked full time in the emergency or respiratory wards at the hospital were eligible. hcws were excluded if they: (i) were unable or refused to consent; (ii) had beards, long moustaches or long facial hair stubble; (iii) had a current respiratory illness, rhinitis and ⁄ or allergy and (iv) worked part-time or did not work in the aforementioned wards ⁄ departments. in all participating wards, 100% of eligible health workers participated. participants wore the mask or respirator on every shift for 4 consecutive weeks after being shown when to wear it and how to fit it correctly. participants were supplied daily with either three masks for the medical mask group or two n95 respirators. participants were asked to store the mask in a paper bag every time they removed it (for toilet breaks, tea ⁄ lunch breaks and at the end of every shift) and place the bagged mask or respirator in their locker. all participants were instructed on the importance of hand hygiene prior to ⁄ after the removal of medical masks and respirators. participants in arm two underwent a fit-testing proce-dure using a 3mô ft-30 bitrex fit test kit according to the manufacturers' instructions (3mô, st paul, mn, usa). detailed demographic and clinical details of all participants were collected. this included age, sex, smoking history, comorbidities, seasonal influenza vaccination status, medications, conduct of high-risk procedures (defined as suctioning, intubation, nebulized medications, chest physiotherapy and other aerosol generating procedures), handwashing practices, use of other personal protective equipment (gowns, gloves, eye shields and hair ⁄ foot covers) and results of laboratory tests. use of specific interventions for influenza such as antivirals was also measured. participants were followed for 4 weeks of wearing the masks or respirators and an extra week of non-wearing for development of respiratory symptoms. all participants received a mercury thermometer to measure their temperature at the beginning of each day and at the onset of any symptoms. diary cards were provided for the duration to record daily the (i) number of hours worked; (ii) mask ⁄ respirator usage and (iii) recognized cri encounters. participants were contacted daily by phone or face-to-face contact to actively identify incident cases of respiratory infection. at each ward, the head nurse actively followed up all participants and identified incident illness. staff members from the district cdc also undertook daily monitoring of the sites. if participants were symptomatic, swabs of both tonsils and the posterior pharyngeal wall were collected. we also monitored adherence with mask or respirator use over the 4-week time course by: (i) observation: the head ward nurse observed compliance on the ward on a daily basis and recorded the information on a structured form, (ii) self-report: a diary card with tick boxes was given to each subject, to be carried during the day. adherence to wearing the masks or respirators was monitored by these diary cards and returned to researchers on a weekly basis. exit interviews with participants were conducted after the 4 weeks to gain further insights into adherence and other issues around the use of masks ⁄ respirators including adverse effects. participants with symptoms had two pharyngeal swabs collected by a trained nurse or doctor. double rayon-tipped, plastic-shafted swabs were used to scratch both tonsilar areas and the posterior pharyngeal wall. these were transported immediately after collection to the laboratory, or at 4°c within 48 hours if transport was delayed. pharyngeal swabs were tested with at the laboratories of the beijing centers for disease control and prevention. viral dna ⁄ rna was extracted from 300 ll of each respiratory specimen using the viral gene-spin tm kit (intron biotechnology, inc., seoul, korea) according to the manufacturer's instructions. reverse transcription was performed on 8 ll of rna in a final reaction volume of 20 ll for 1ae5 hours at 37°c, using the revertaid tm first strand cdna synthesis kit (fermentas, burlington, on, canada) to synthesize cdna. multiplex polymerase chain reaction (pcr) was carried out using the seeplex ò rv12 detection kit (seegen, inc., seoul, korea) to detect adenoviruses, human metapneumovirus, coronavirus 229e ⁄ nl63, parainfluenza viruses 1, 2 or 3, influenza viruses a or b, respiratory syncytial virus a or b, rhinovirus a ⁄ b and coronavirus oc43 ⁄ hku1. three microlitres of synthesized first-strand cdna, 4 ll of multiplex primers, 10 ll master mix (hot start taq dna polymerase and dntp are included in the reaction buffer) and 3 ll of 8-methoxypsoralen (8-mop) were added (8-mop, accompanied by uv irradiation for 20 minutes, prevents amplification of contaminated dna). a mixture of 12 viral clones was used as a positive control template, and sterile deionized water was used as a negative control. after preheating at 95°c for 15 minutes, 40 amplification cycles were carried out under the following conditions in a thermal cycler (geneamp pcr system 9700, foster city, ca, usa): 94°c for 30 seconds, 60°c for 1ae5 minutes and 72°c for 1ae5 minutes. amplification was completed at the final extension step at 72°c for 10 minutes. the multiplex pcr products were visualized by electrophoresis on an ethidium bromidestained 2% agarose gel. viral isolation by mdck cell culture was undertaken for some of the influenza samples which were positive by nuclei acid detection. specimen processing, dna ⁄ rna extraction, pcr amplification and pcr product analyses were conducted in different rooms to avoid cross-contamination. the primary endpoints of interest as described above were analysed by intention-to-treat analysis. the two n95 arms were also combined and compared to the medical mask arm, given that there was no significant difference between them and rates of fit test failure were extremely low in the fit-tested arm (5 ⁄ 461 fit test failures). differences in proportions between the trial arms were tested by calculation of pearson's chi-square using sas 9.2 software (cary, nc, usa). the distribution of key potentially confounding variables between study arms was compared. to estimate the odds ratio while adjusting for the clustering effects, we used a random effect logistic regression model. in the model, we added a hospital-specific random intercept in the linear predictors, and maximum likelihood was estimated using adaptive quadrature. 20 the model was fitted using 'xtlogit' command in stata (college station, tx, usa). 21 we also conducted multivariable analysis to adjust for the potential confounders. in the initial model, we included all the variables along with the main exposure variable those were significant (p < 0ae05) in the univariate analysis. we then used a backward elimination method to remove the variables that did not have any confounding effect, that is, could not make meaningful (roughly 10%) change in the effect measure with the main exposure variable. 22 in case of high multi-collinearity because of strong correlation among the potential confounders, we chose the more relevant ones having the highest confounding effect on the association of interest. we analysed compliance as wearing the mask for >80% of the shift. to obtain 80% power at 2-sided 5% significant level for detecting a significant difference of attack rate between the intervention arms, and for an assumed 5% attack rate in the n95 arm and 12% in the medical mask arm, a sample size of 488 participants or five clusters (hospitals) per arm was required for cluster size (m) 100 and intra-cluster correlation coefficient (icc) 0ae01. 23 the design effect (deff) for this cluster randomization trial was 2 (deff = 1 + (m)1) · icc = 1 + (100)1) · 0ae01 = 2). as such, we aimed to recruit a sample size of 500 per arm. a total of 1441 nurses and doctors in 15 beijing hospitals were recruited into the randomized arms and 481 nurses and doctors in nine hospitals were recruited into the convenience no-mask group. figure 1 shows the recruitment process. the distribution of demographic variables was generally similar between arms (table 1) , but was significantly different for anyone smoking in the family, four or more people in family, four or more adults in family, influenza vaccination in 2008 and 2007, public transport, handwashing, hospital level and high-risk procedures. in regards to hand hygiene, 83% (382 ⁄ 461), 87ae8% (428 ⁄ 488) and 88ae6% (435 ⁄ 492) of participants from the n95 fit test arm, n95 non-fit test arm and medical mask arm stated that they washed their hands between patients, respectively. for all outcomes, non-fit-tested n95 respirators had lower rates of infections compared to fit-tested n95s (for all n95 versus medical masks, the rates were 3ae9% versus 6ae7% for cri, 0ae3% versus 0ae6% for ili, 1ae4% versus 2ae6% for laboratory-confirmed virus and 0ae3% versus 1% for influenza) but these differences were not significant. all infection outcomes were consistently higher (approximately double) in the medical mask group compared to the n95 group ( figure 2 ). there were no cases of influenza in the non-fit-tested n95 arm, three in the fit-tested n95 arm and five in the medical mask arm. after adjustment for clustering, non-fit-tested n95 masks were significantly protective compared to medical masks against cri, but other outcomes were not significant between n95 and medical masks ( table 2) . when compared to the convenience no-mask group and adjusted for clustering, n95 non-fit-tested was significantly protective against cri, and all n95 was protective against laboratory-confirmed virus and laboratoryconfirmed influenza (table 3 ). in a post hoc analysis carried out to adjust for potential confounders which were unevenly distributed between arms, all n95 and hospital level remained significant for cri and laboratory-confirmed viral infection, but handwashing, vaccination and high-risk procedures were not significant (table 4) . fit-testing failure rate was very low (5 ⁄ 461, 1ae08%). rates of adherence in all arms of the study were high (figure 3 ). table 5 shows adverse events associated with medical mask or n95 use, and that n95 respirators were associated with higher rates of adverse events. adherence with mask or respirator wearing was high and not significantly different in all arms, with 74% adherence (95% ci 70-78%) in the n95 fit-tested arm, 68% in the n95 nonfit-tested arm (95% ci 64-73%) and 76% in the medical mask arm (95% ci 72-79%). the duration of mask wearing in these arms, respectively, was 5ae2 hours (95% ci 5ae1-5ae4 hours), 4ae9 hours (95% ci 4ae8-5ae1 hours) and 5 hours (95% ci 4ae9-5ae2 hours; figure 3 ). we found that rates of respiratory tract infection were approximately double in the medical mask group compared to the n95 group in health workers who wore masks throughout their shift. however, only the n95 non-fittested arm was significantly protective against cri, and there were no other significant differences between n95 respirators and medical masks for the four primary outcomes in the adjusted analysis. however, it should be noted that under the null hypothesis where there is no difference between groups, the probability that we wrongly find at least one significant difference given the 12 tests undertaken is 46%. the trial may also be underpowered because observed attack rates were lower than expected. the rates of all outcomes were higher in the convenience no-mask group than in the masks groups. *ili definition using fever >38 -note, this is less sensitive than laboratory-confirmed infection. **any respiratory virus. ***odds ratio -medical group as reference. a random effect logistic model accounting for clustering was used to compute odd ratios. p m : p value adjusted for clustering of hospitals using random effect logistic regression model. 29 cri, clinical respiratory illness; ili, influenza-like illness. intention-to-treat analysis, n95 respirators but not medical masks had significantly lower rates of infection compared to no masks. however, the convenience no-mask group was not a randomized control arm and hospitals in this group were actually selected on the basis that most of their staff did not wear masks (which is not the norm in hospitals in beijing), suggesting that conditions in those hospitals were different than those in hospitals from the masks groups. as a consequence, it is not possible to make any definitive judgement on the efficacy of masks on this basis. one possible bias would be if those hospitals had differentially higher risk of infection compared to the intervention hospitals, for example because of the occurrence of outbreaks. however, we monitored all hospitals involved in the study for outbreaks which may have increased apparent attack rates, and none were documented. other than that, possible sources of bias that could have plausibly increased the infection rate in the control arm (namely vaccination, handwashing, hospital level and high-risk procedures) were measured. in a post hoc adjusted analysis, only hospital level and the n95 arm were significant against cri and laboratory-confirmed viral infection. respiratory protection is a key strategy for pandemic control and key to sustaining the health care workforce. the fact that rates of all outcomes were consistently lower in the n95 group suggest that n95 respirators might offer better protection for hcws; but a larger trial is needed to make a definitive judgment about the relative efficacy of respirators and medical masks. a recent, smaller trial found no difference between n95 and medical masks, but was *ili definition using fever >38 -note, this is less sensitive than laboratory-confirmed infection. **any respiratory virus. ***odds ratio -no-mask convenience group as reference. a random effect logistic model accounting for clustering was used to compute odd ratios. cri, clinical respiratory illness; ili, influenza-like illness. bold text signifies statistical significance. probably underpowered to detect any differences. 11 further, the intervention in that study was use of respiratory protection only during care of identified febrile patients with ili or high-risk procedures. this is different from the intervention in our study, which comprised wearing the mask for the entire shift. in addition, that study measured serological evidence of influenza as an outcome, which comprised the majority of outcomes, but did not exclude influenza-vaccinated participants, a flaw that would have resulted in falsepositive cases of 'influenza'. the finding that fit testing did not improve the efficacy of n95 respirators is important, although it could be explained by a lack of power. the value of fit testing varies with the quality of the respirator, and our study used a high-quality respirator. these results would not be generalizable to other respirators, where fit testing may be more important. as such, we still recommend that fit testing be part of the process of using respirators. the small number of randomization units along with the small numbers of cases means that estimation of multivariate models would not necessarily converge. in the post hoc multivariable analysis, we could not adjust for all of the factors because of high correlation among some of them. other limitations of the study include the generalizability of our results to other types of respirators and to other hcw populations in other countries. scoping work with australian hcws showed compliance of 10% with continual mask wearing during a severe influenza season. 24 beijing was selected to maximize the power of the study because of the strong culture of mask wearing among hcws. another limitation of the study is that cluster rcts can be impacted by heterogeneity of behaviours, meaning that we cannot exclude such effects caused by behaviours we did not measure. the cluster design is also strength, as interventions against infectious diseases can have herd effects. in infectious diseases which can spread from person to person, the 'herd effect' is a real and documented phenomenon where protecting some individuals with an intervention (most commonly vaccination, but also applicable to other interventions) can also protect individuals who were not protected by the intervention. therefore, if some individuals are randomized to masks on a ward, the individuals who do not wear masks may also be protected because of the effect the masks have on interrupting the transmission of disease from person to person. this is why it is preferable to use cluster design, where everyone in the cluster gets the same intervention. in our study, masks or respirators were worn during the entire shift. some policies recommend mask ⁄ respirator use only when hcws are conducting high-risk procedures or entering an isolation room. whether masks ⁄ respirators will be protective when used only when an identified episode of exposure occurs depends on whether hcws accurately identify all episodes of risk, whether most transmission occurs after clearly identified exposures and whether there is transmission from asymptomatic or pre-symptomatic infections. there is currently no evidence on how much of a hcws' risk is unidentified or unrecognized. in our study, hcws who conducted high-risk procedures had higher rates of cri, but not of laboratory-confirmed pathogens or influenza. further clinical research is required to determine the efficacy of continuous versus targeted mask use. until now, public health policy for dealing with pandemics has relied heavily on data from a modest number of often old and inadequate studies. data from the sars outbreak showed that masks reduced transmission of sars and other viral respiratory infections. 25, 26 during sars, the use of n95 respirators and medical masks was the major protective infection control measure. 27 however, the relative contribution of each type or the difference between n95 respirators and medical masks cannot clearly be determined from observational data. problems with adherence to mask ⁄ respirator use are also a potential problem. we showed that in australia, less than half of parents who were randomized to wear a medical mask or respirator while their child was ill adhered with mask wearing. 10 there may be adverse effects of wearing masks, which can reduce adherence. [28] [29] [30] our study showed significantly higher reported adverse effects of n95 respirators compared to medical masks, consistent with other studies. 28 interestingly, this population of chinese hcws reported overall similar rates of discomfort with masks as parents in our household study, 10 with higher rates in the n95 group, but it did not affect their adherence with mask ⁄ respirator wearing. this suggests that discomfort is not the primary driver of adherence, and rather, cultural acceptability and other behavioural factors may be the main reason for non-adherence. the past experience of beijing health workers with sars may also be a factor in the high adherence. this level of adherence may not translate to western cultural contexts in a normal winter season, especially for n95 respirators; however, adherence can change with perception of risk. during a pandemic, we would expect hcws to have higher adherence to infection control measures. in summary, our study adds evidence on the use of respiratory protection for hcws, but highlights the need for larger trials and comparison of different policy options. sanofi-pasteur msd on the modelling of varicella zoster virus. the remaining author(s) declare that they have no competing interests. the corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication. prior to the start of this study, nmf acted as a consultant for roche, novartis and gsk biologicals (ceasing in 2007). pandemic potential of a strain of influenza a (h1n1): early findings nosocomial influenza infection among post-influenza-vaccinated patients with severe pulmonary diseases disruption of services in an internal medicine unit due to a nosocomial influenza outbreak a nosocomial outbreak of influenza during a period without influenza epidemic activity epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in hong kong short-and long-term effects of handwashing with antimicrobial or plain soap in the community effect of antibacterial home cleaning and handwashing products on infectious disease symptoms: a randomized, double-blind trial handwashing and risk of respiratory infections: a quantitative systematic review facemasks and hand hygiene to prevent influenza transmission in households: a randomized trial face mask use and control of respiratory virus transmission in households surgical mask vs n95 respirator for preventing influenza among health care workers: a randomized trial novel h1n1 influenza and respiratory protection for health care workers do n95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks? comparison of performance of three different types of respiratory protection devices aerosol penetration and leakage characteristics of masks used in the health care industry is a mask necessary in the operating theatre? surgical face masks in modern operating rooms-a costly and unnecessary ritual? postoperative wound infections and surgical face masks: a controlled study influenza burden of illness: estimates from a national prospective survey of household contacts in france multilevel and longitudinal modeling using stata regression methods in biostatistics: linear, logistic, survival, and repeated measures models an introduction to categorical data analysis design and analysis of cluster randomization trials in health research feasibility exercise to evaluate the use of particulate respirators by emergency department staff during the 2007 influenza season respiratory infections during sars outbreak evaluation of control measures implemented in the severe acute respiratory syndrome outbreak in beijing effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (sars) headaches and the n95 face-mask amongst healthcare providers the physiological impact of wearing an n95 mask during hemodialysis as a precaution against sars in patients with end-stage renal disease a stepwise resampling method of multiple hypothesis-testing we acknowledge the guidance and support we received from the staff at 3m china. this comprised assistance with fit testing for the study, but not financial support. thanks also go to the trial staff at the beijing centre for disease control and surveillance and their affiliated public health units. thanks to the staff from the 15 beijing hospitals which participated. professor raina macintyre designed the study, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. dr simon cauchemez thanks the research council, uk, and neil ferguson thanks the medical research council for centre funding. professor c. raina macintyre: as the lead investigator raina macintyre was responsible for conception and design of the trial, overseeing the whole study, analysing data and writing the report; professor quanyi wang: implementation, contribution to design, analysis and drafting of paper; dr simon cauchemez: statistical analysis and drafting of paper; dr holly seale: study design, form ⁄ database development, monitoring and review of paper; professor dominic e dwyer: study design, clinical and laboratory technical assistance and drafting of paper; dr peng yang: project manager; dr weixian shi: laboratory testing in china; dr zhanhai gao: statistical analysis and drafting of paper; dr xinghuo pang: recruitment and training; dr yi zhang: database management and analysis; dr xiaoli wang: database management and analysis; dr wei duan: recruitment and training; dr bayzidur rahman: statistical analysis and drafting of paper; professor neil ferguson: statistical analysis and drafting of paper. professor raina macintyre: raina macintyre receives funding from influenza vaccine manufacturers gsk and csl biotherapies for investigator-driven research. she has also been on advisory boards for wyeth, gsk and merck. dr simon cauchemez received consulting fees from key: cord-034298-9hpkmjvu authors: palmer, carl l.; peterson, rolfe d. title: toxic mask-ulinity: the link between masculine toughness and affective reactions to mask wearing in the covid-19 era date: 2020-07-09 journal: nan doi: 10.1017/s1743923x20000422 sha: doc_id: 34298 cord_uid: 9hpkmjvu the covid-19 pandemic has altered numerous elements of social, political, and economic life. mask wearing is arguably an essential component of the new normal until substantial progress is made on a vaccine. however, though evidence suggests the practice is a positive for public health and limiting the transmission of covid-19, there is variation in attitudes toward and practices of mask wearing. specifically, there appears to be a sex-based divide in mask wearing, with men more likely to resist wearing masks. utilizing an original survey, we test the correlation between masculinity and mask wearing. we find that identification with norms of masculinity has a significant influence on affective responses toward mask wearing. the newest victim of the culture war, with resistance to mask wearing splitting along political and identity lines (padilla 2020; rozsa et al. 2020) . observers have further argued that the resistance to mask wearing may be rooted in masculinity and the desire to appear "tough" (north 2020) . in this research note, we empirically test the relationship between sex, masculinity, and affective responses to mask wearing. our online study conducted in early june 2020 shows that masculine toughness is consistently related to higher negative feelings and lower positive feelings about mask wearing. the findings have implications for understanding the affective underpinnings of resistance to mask wearing during covid-19. a rich body of literature examines the correlation between masculinity and engaging in risky activities, particularly those relating to health (fowler et al. 2011; iwamoto et al. 2011; levant et al. 2009; mahalik et al. 2007 ). arguably, this stems from social pressures for men to adopt masculine norms such as toughness (morrissey 2008; vandello and bosson 2013) , which are regularly influenced by agents of socialization including the family, peer groups, and school environment. furthermore, men express greater levels of toughness under conditions of threat (fowler and geers 2017) and express differential attitudes toward actions such as help seeking when their embrace of masculine norms deepens (vogel et al. 2011) . with some elites framing the issue of mask wearing as a matter of masculinity and toughness, we approach attitudes toward mask wearing on two dimensions: negative affective reactions toward mask wearing and positive affective reactions toward mask wearing. affect is a key component of information processing, and modern research shows that our affective and intuitive reactions are primary drivers of cognition (haidt 2012; lodge and taber 2013) . prior research leads us to the following expectations: h 1 : respondents who are higher in toughness, regardless of sex, should express significantly more negative attitudes toward mask wearing. h 2 : respondents who are higher in toughness, regardless of sex, should express significantly less positive attitudes toward mask wearing. to test our hypotheses, we utilize data from an original survey conducted using amazon's mechanical turk on june 5, 2020. access to the survey was limited to mturk workers who had a 95% approval rating for a minimum of 50 previously completed tasks. our total sample size was 805 respondents, 61% male and 39% female. we provide a demographic comparison to the 2016 american national election study (anes) to benchmark our sample; unsurprisingly, our sample skews slightly younger and better educated, as is common with mturk samples. such samples have also been able to replicate findings from more representative samples (berinsky, huber, and lenz 2012; goodman, kryder, and cheema 2013) . the survey battery included a series of standard demographic items, measures of individual characteristics (including our measure of masculine ideation), and attitudes toward mask wearing. average time to complete the survey was 12 minutes. analyses excluding the slowest and fastest 1% provide identical results to those reported here. our measure of masculinity is taken from the "toughness" subscale of the masculine role norms index (levant et al. 2010) , which is composed of five items (full wording appears in the online appendix). our sample has an alpha reliability of .89 between the battery components. we rescale the index to run from 0 to 1, with 1 being maximum endorsement of male toughness. although a preliminary analysis shows men to score statistically significantly higher on this index (difference of means 0.60 versus 0.55, p < .01), both men and women in our sample express expectations for men to display toughness. our analyses focus on affective reactions to wearing masks in public: whether respondents react negatively to the act of wearing masks in public and whether individuals react positively to wearing masks. to gauge feelings on mask wearing, respondents were asked whether they felt controlled, weak, scared, silly, brave, caring, strong, and protected when wearing masks, with items presented in random order. reliability for the negative reactions is .78, and for the positive items, it is .87. question wording appears in the appendix. from this battery, we create two indices: one index of positive affective reaction and one index of negative affective reaction. we utilize two scales rather than generate one single scale because we believe the scales are separate rather than opposite ends of a single spectrum, and we seek toxic mask-ulinity to test the degree to which masculinity differentially predicts negative and positive reactions separately. to create the index of negative affective response, the subject's responses to the four negative descriptors (controlled, weak, scared, and silly) are averaged to create a continuous measure from low to high negative reactions. the overall positive affective index is created using the same procedure (averaging responses to brave, caring, strong, and protected). we control for a host of variables from social and political identity to demography and context. to account for individuals' location and threat level, we include a variable that captures their state's policy toward mask wearing at the time of the survey (masks4all 2020). all analyses control for these restrictions (a three-category variable from none to statewide), in addition to measures of partisanship (a 7-point scale, coded from strong democrat to strong republican), ideology (a 7-point scale, coded from extremely liberal to extremely conservative), and measures for education, age, sex (female with male as the reference), race (nonwhite with white as the reference), and context (rural and suburban with urban as the reference). all explanatory variables are rescaled to run from 0 to 1 for ease of comparing effect sizes, and all models cluster errors by state. table 1 presents the ordinary least squares (ols) models for masculine toughness on negative reactions to mask wearing for the full sample and separately for subsamples of men and women. running the models separately for sex categories allows us to see whether masculine toughness operates the same way for men and women. in each model, the effect of masculine toughness is positive and significant; a stronger belief that men should be tough corresponds to greater levels of negativity regarding mask wearing, in line with h 1 . interestingly, while levels of expressed toughness are greater for men than for women, the substantive effect of toughness on negativity toward mask wearing is comparable for men and women. in each case, toughness increases negativity toward mask wearing by slightly less than 1 point, a larger effect than partisanship, education, or any of the contextual measures. we turn next to the effects of masculine toughness on positive feelings of mask wearing. here, we expect greater toughness to be negatively correlated with positive reactions, particularly among men. findings for toughness are again in the expected direction, with greater expressed beliefs in toughness decreasing overall positive reactions to wearing masks, in line with h 2 . we also see that, unlike negative reactions, where the effect of toughness for men and women is roughly identical, there is a notable difference between men and women here, with men's positive reactions lower than women's by 0.33 points. as with the results from table 1 , the effects of masculinity are much larger than partisanship and the contextual variables. popular observers speculate that masculinity and toughness are connected to negative reactions to the wearing of masks. here, we leverage empirical toxic mask-ulinity data to empirically test the connection. broadly, we find that men and women who embrace masculine norms of toughness are equally likely to feel negative affective responses toward the idea of wearing masks, even after accounting for other predictors such as partisanship and ideology. additionally, while toughness predicts positive attitudes toward mask wearing for men and women, the negative effect is larger for men. affective responses and feelings toward mask wearing should predict future behavior. one limitation of this analysis is our inability to examine behavioral outcomes in this survey. because nearly every state had some form of mask requirement and because of the heightened threat of the pandemic, our sample does not have meaningful variation on reported mask wearing, with 75% of respondents stating that they wear masks always or most of the time when in public. even with a to view supplementary material for this article, please visit https://doi.org/ 10.1017/s1743923x20000422 what u.s. states require masks in public using mechanical turk as a subject recruitment tool for experimental research does trait masculinity relate to expressing toughness? the effects of masculinity threat and self-affirmation in college men concept priming and pain: an experimental approach to understanding gender roles in sex-related pain differences data collection in a flat world: strengths and weaknesses of mechanical turk samples the righteous mind: why good people are divided by politics and religion man-ing' up and getting drunk: the role of masculine norms, alcohol intoxication and alcohol-related problems among college men evaluation of the factor structure and construct validity of scores on the male role norms inventory-revised (mrni-r) the relationships between masculinity variables, health risk behaviors and attitudes toward seeking psychological help the rationalizing voter masculinity and perceived normative health behaviors as predictors of men's health behaviors performing risks: catharsis, carnival and capital in the risk society what trump's refusal to wear a mask says about masculinity in america who's wearing a mask? women, democrats and city dwellers the battle over masks in a pandemic: an all-american story hard won and easily lost: a review and synthesis of theory and research on precarious manhood boys don't cry': examination of the links between endorsement of masculine norms, self-stigma, and help-seeking attitudes for men from diverse backgrounds key: cord-031440-0irbypnt authors: arango, lázaro; díaz, claudia; puentes, fabián; sánchez, andrés; jaramillo, mario title: adaptation for endoscopy of a ventilation mask using a glove finger like a filter: trying to reduce aerosols date: 2020-09-04 journal: videogie doi: 10.1016/j.vgie.2020.07.013 sha: doc_id: 31440 cord_uid: 0irbypnt nan adaptation for endoscopy of a ventilation mask using a glove finger like a filter: trying to reduce aerosols lázaro arango, md, fasge, claudia díaz, md, fabián puentes, andrés sánchez, md, mario jaramillo the name of the covid-19 pandemic is derived from the coronavirus disease that started in 2019. it is caused by coronavirus 2 virus of severe acute respiratory syndrome. it was first identified in december 2019 in wuhan city, the capital of hubei province in the people's republic of china. a group of sick people with an unknown type of pneumonia were reported. most affected individuals were linked to workers at the wuhan south china wholesale seafood market. the world health organization recognized it as a pandemic on march 11, 2020. 1 when the disease was studied in more detail, one of the transmission routes was found to be aerosols and drops or secretions. upper digestive endoscopy was determined as a probable transmission route for the virus. for this reason, by recommendation of the different scientific associations around the world and the who, in the initial phases of the pandemic, only emergency endoscopy procedures were performed. as knowledge has grown regarding the safety of medical staff and patients, priority patients have begun being treated in most countries. 2 we believe, medically, that the pandemic will not end quickly; only with a vaccine and the social conscience of the people can the contagion be reduced. in these circumstances, even if the contagion rate decreases, aerosolgenerating procedures should continue to be carried out with all precautions, including programs to create community awareness, use of personal protection elements, social distancing, and hand washing. some publications have shown devices that are being used by endoscopists to decrease aerosol loading, such as the aponte et al 3 face mask and the sabbagh barrier. 4 there are some masks that anesthesiologists use for ventilation. these have 4 pins (fig. 1) . we have adapted them using bands with holes that are anchored to the pins (fig. 2) , thus creating an almost perfect seal with the patient's face. if there is a gap, we reinforce the closure with micropore tapes; however, this occurs in few cases. the mask has a hole in the center that is used for ventilation maneuvers with the ambu (airway mask bag unit); we put a glove finger on this site, which fits perfectly and does not move. we make a small cut with scissors in this glove finger; endoscopes, including duodenoscopes, enteroscopes, and endosonographs, pass perfectly through this, and the glove finger makes an adequate filter. this procedure includes the following steps: 1. we place the endoscopy nozzle and the nasal cannula (fig. 3) ; both are fixed with adhesive tape (fig. 4 ). 2. we place the mask on the patient's face, making an almost complete seal in which the bands perfectly fit the pins (fig. 5 ). 3. we put the mask on the patient. between the mask and the patient's face, we put an aspiration probe, connected to an aspiration instrument. this instrument vacuums drops and aerosols, reducing the contamination risk further (fig. 6 ). 4. in the central hole of the ventilation mask, we place the glove finger (fig. 7) and make a small cut with scissors (fig. 8) . 5. at the end of the procedure, the mask is removed by the endoscopist and placed directly in a red bag. it is then taken to disinfection management, where it is washed with enzymatic soap for 20 minutes and glutaraldehyde for another 20 minutes and then rinsed with water and dried. these masks can thus be reused. as shown in figure 9 , the mask is a handmade accessory that protects against secretions and aerosols, preventing contamination of health personnel working in the unit (video 1, available online at www.videogie.org). all authors disclosed no financial relationships. considerations in performing endoscopy during the covid-19 pandemic covid-19) outbreak: what the department of endoscopy should know use of a new face shield for patients of the endoscopy unit to avoid aerosol exchange in the covid-19 era new protection barrier for endoscopic procedures in the era of pandemic covid-19. videogie. epub copyright ª 2020 american society for gastrointestinal endoscopy key: cord-316126-j51dik7f authors: zhang, x. sophie; duchaine, caroline title: sars-cov-2 and health care worker protection in low-risk settings: a review of modes of transmission and a novel airborne model involving inhalable particles date: 2020-10-28 journal: clin microbiol rev doi: 10.1128/cmr.00184-20 sha: doc_id: 316126 cord_uid: j51dik7f since the beginning of the covid-19 pandemic, there has been intense debate over sars-cov-2’s mode of transmission and appropriate personal protective equipment for health care workers in low-risk settings. the objective of this review is to identify and appraise the available evidence (clinical trials and laboratory studies on masks and respirators, epidemiological studies, and air sampling studies), clarify key concepts and necessary conditions for airborne transmission, and shed light on knowledge gaps in the field. we find that, except for aerosol-generating procedures, the overall data in support of airborne transmission—taken in its traditional definition (long-distance and respirable aerosols)—are weak, based predominantly on indirect and experimental rather than clinical or epidemiological evidence. consequently, we propose a revised and broader definition of “airborne,” going beyond the current droplet and aerosol dichotomy and involving short-range inhalable particles, supported by data targeting the nose as the main viral receptor site. this new model better explains clinical observations, especially in the context of close and prolonged contacts between health care workers and patients, and reconciles seemingly contradictory data in the sars-cov-2 literature. the model also carries important implications for personal protective equipment and environmental controls, such as ventilation, in health care settings. however, further studies, especially clinical trials, are needed to complete the picture. t he world is facing a devastating new infectious disease, with only preliminary scientific data to guide policy. disagreement with the world health organization's stance on personal protective equipment (ppe), guideline changes over time (e.g., european cdc, france) , and inconsistent data on the effectiveness of medical masks have left health care workers (hcws) wondering if they are sufficiently protected. the general consensus is that sars-cov-2 predominantly transmits through droplets and contact (although precise mechanisms for both modes of transmission are yet to be fully understood), but the airborne debate is still raging. this review attempts to summarize current cumulative data on sars-cov-2's modes of transmission and identify gaps in research while offering preliminary answers to the question on everyone's mind: is the airborne route significant and should we modify our covid-19 ppe recommendations for frontline workers in low-risk settings? this review starts by investigating the differences between droplets and aerosols and goes over prerequisites for clinically significant airborne transmission. it then appraises the evidence in support of the airborne hypothesis: trials and experiments on masks, epidemiological studies, data on sars-cov-1, air sampling findings, and aerosol studies. the focus is on low-risk health care settings, in the absence of aerosolgenerating procedures (agps), with a special look at long-term-care facilities where major outbreaks occurred. national and international guidelines are compared, and alternative hypotheses for sars-cov-2's contagiousness are explored, such as presymptomatic transmission, as well as fomite and fecal routes. possible mechanisms behind high hcw infection rates are described, and the limits of the precautionary principle are addressed. finally, a revised model of inhalable particles is proposed to support ppe recommendations and guide future research. determining sars-cov-2's main mode of transmission is essential as it informs clinical guidelines for patient management, prevention practices, and hcw protection. while infectious disease precautions in health care settings are transmission-based (either airborne or droplet), in reality, the distinction is not clear-cut; instead, they are two ends of a spectrum. in the literature, respiratory droplets are usually defined as larger particles (diameter ͼ 5 m) sometimes visible to the human eye, produced during spitting, sneezing, and coughing. these droplets are thought to be the main mode of transmission of covid-19 (1), and they typically travel 1 to 2 m before landing on surrounding surfaces. however, they may be propelled further in the presence of ventilation (2) or forceful ejection (e.g., a violent sneeze) (3) and under certain environmental conditions (e.g., cool and humid) (4) . the sars-cov-2 virus is also thought to be transmitted by direct contact person to person (e.g., exchange of saliva or a handshake) or by indirect contact through intermediate objects (e.g., sharing of cups, doorknobs). generally, contact transmissions occur when contaminated hands are brought to the face and touch mucous membranes (eyes, nose, and mouth). the fate of smaller droplets may be desiccation (evaporation of the liquid) and formation of particles called droplet nuclei, or aerosols, which can contain infectious agents but also secretions, cells, surfactant, and any other product contained in the original droplet. traditionally, aerosols are defined as particles of ͻ5 m that can remain airborne for prolonged periods (several minutes or even hours) and travel long distances with air currents (several meters away). with the potential for direct entry into the lungs, they are the primary mode of transmission for tuberculosis, measles, and varicella. in other communicable diseases, such as influenza, aerosols are considered opportunistic and play a role that is of variable importance depending on the context (5) . conversely, in the field of industrial hygiene, occupational exposure of different body regions to harmful airborne agents is classified into three overlapping categories, according to the median size of penetrating particles (6): 100 m for nose and mouth (inhalable), 10 m for trachea and bronchi (thoracic), and 4 m for alveoli and air exchange regions (respirable). this aerosol classification was recently reviewed and elegantly illustrated by milton (7) . in this model, the concept of aerosol inhalability is defined as the fraction of particles capable of penetrating into the head airways or below, upon inhalation: it excludes larger droplets with ballistic behavior (since inhalation requires suspension in the air) but includes particles that are larger than the traditional 5-m definition of aerosols. throughout our review, this more nuanced conceptualization of airborne transmission will be explored, and the larger inhalable aerosols will be contrasted to the smaller respirable aerosols from the classic airborne model. finally, some procedures, such as intubation, are known to generate aerosols, while others, such as nebulizer therapy, are associated with an uncertain risk of aerosolization (8) . n95s (or similar respiratory protection devices) are unequivocally recommended for hcws working in high-risk settings with agps, although controversy still remains around which interventions constitute an agp. the design protocol for the n95, and the origin of the name, is based on its efficiency at capturing 95% of the most penetrating size range (0.3 m) of respirable aerosols (9) . by default, respirators are therefore capable of blocking the entire spectrum of airborne particles. medical masks, on the other hand, are designed to block droplets and do not undergo aerosol-filtering tests; they are therefore not considered to provide respiratory protection against airborne transmission. given that substantial disagreement persists on the importance of natural aerosol generation by covid-19 patients, and consequently, the necessary level of respiratory protection in non-agp contexts, our review will focus on transmission and ppe in low-risk health care settings. natural respiratory activities such as breathing, talking, and coughing can generate a broad range of particle sizes, from submicron aerosols to large droplets (10) (11) (12) (13) (14) . for the viral aerosols to constitute a clinically significant risk of airborne infection, three conditions are required: viral load (the concentration of infectious particles), infectivity (the ability of a virion to infect a host cell), and tropism (the specificity of a virus for a particular host cell type or tissue). since the amount of sars-cov-2 virus required to infect a host is unknown, and likely varies from one individual to another (preprint article [15] ), it is hard to determine whether typical respiratory activity generates sufficient quantities of infectious aerosols for airborne transmission. in a light-scattering study, stadnytskyi et al. estimated that 1 min of loud speaking generated at least 1,000 virion-containing droplet nuclei that remain airborne for more than 8 min (16) . however, the calculations were based on several theoretical assumptions and data from sputum load was incorrectly applied to saliva, likely overestimating aerosol viral loads. in this model, the probability that a hypothetical speech-generated droplet nucleus of 3 m contains a sars-cov-2 virion is only 0.01%, after aerosolization and desiccation. furthermore, in a mathematical modeling study on viral aerosol emissions, an individual with a high viral load was estimated to emit only modest amounts of virus with regular breathing (1,248 copies/ m 3 ) compared to coughing (7.44 million copies/m 3 ) (17). accordingly, the authors conclude that the infectious risk posed by a typical covid-19 patient is low, especially if symptoms are mild, and only a few individuals with high viral load pose a significant risk. these authors suggest that strict respiratory protection may be needed in the case of prolonged exposure to high emitters in poorly ventilated closed environments. notwithstanding, evidence of aerosol generation during natural respiratory activity or the presence of viral rna in the air are not sufficient to prove that the virus remains infectious once airborne. not all viruses are equally stable in the air, and further aerodynamic and environmental factors may inactivate viruses during aerosolization (18) . therefore, upon detecting sars-cov-2 aerosols, infectivity must then be demonstrated. evaluation of infectivity is usually done with viral cultures: researchers were able to culture rhinovirus (19) and influenza (20) from the fine particles emitted naturally by infected participants, and only recent yet unpublished research has started to achieve the same for sars-cov-2. however, it is important to note that culture methods vary between viruses and false-negative results due to the low sensitivity of commonly used sars-cov-2 cultures could have possibly underestimated infectivity from air samples until now. for instance, clinical samples (e.g., nasopharyngeal swabs) that yield positive cultures typically have low pcr cycle threshold (c t ) values of ͻ25 (samira mubareka, university of toronto, unpublished data), while c t values for environmental samples (including air samples) are often ͼ35. finally, since particles penetrate and deposit in different parts of the respiratory tract depending on size, knowledge of target locations for infection (e.g., viral tropism) can hint at typical size range and mode of transmission. sars-cov-2's main entry into host cells is through ace2 receptors, which seem to be largely expressed in the nose (21, 22) . importantly, the highest and most consistent signs of viral infectivity have been observed for nasal cells, with a gradient along the respiratory tract characterized by a marked reduction in infectivity in the distal bronchioles and alveoli. this may suggest that lower airways are not targets for infection and that transmission via respirable aerosols is not predominant. interestingly, the typical patchy bilateral pneumonia found in covid-19 patients is postulated to be caused by oropharyngeal microaspirations rather than direct viral seeding in the lungs, possibly accounting for the increased risk with age and comorbidities (22) . different types of studies suggest airborne transmission, but their levels of evidence are variable. in this review, given the focus on health care settings and hcw protection, studies are appraised according to clinical relevance: hard outcomes (e.g., morbidity) are markers of higher levels of evidence, while surrogate outcomes (e.g., pathophysiological mechanisms, modeling, and laboratory results) are considered lower levels of evidence, independent of method or design quality (table 1) . the term "mask," as used here, comprises medical masks, surgical masks, procedural masks, fluid-resistant masks, and face masks worn by hcws. the term "respirator" is used interchangeably with n95, which is the equivalent of ffp2 (european standard filtering facepiece) and kf94 (korean filter) respirators. in the absence of clinical trials on sars-cov-2, trials on other viruses with similar infection patterns (i.e., documented droplet and suspected airborne transmission) are the best available alternatives. recent systematic and narrative reviews comparing the effectiveness of respirators versus masks against common viral respiratory infections (including coronaviruses and influenza viruses such as h1n1) come to similar conclusions: both devices offer comparable protection in health care settings (23) (24) (25) (26) (27) (28) (29) (30) (31) . a few reviews (32) (33) (34) favor respirators, on the basis of two randomized controlled trials (rcts) conducted by the same lead authors, macintyre et al. (table 2 ) (35, 36) . individually and in combination (meta-analysis) (33), these two rcts report superiority of continuous n95 use over mask use for a single self-reported outcome: clinical respiratory illness (cri), defined as two or more respiratory symptoms or one respiratory symptom and a systemic symptom. no difference is found for other more rigorous outcomes: influenza-like illness (ili; defined as fever and one respiratory symptom), laboratory-confirmed viral respiratory infection (lvi), or laboratory-confirmed influenza (lci). the difference between the self-reported outcome and the laboratory results could be explained by detection bias in the absence of participant blinding and universal testing: higher symptom reporting rates in the medical mask group, rather than true infection, could have skewed cri results in favor of respirators. furthermore, selection bias is suspected to have occurred during allocation, given the surprisingly uneven distribution of major confounding variables such as agps, age, and handwashing, between the n95 and mask groups. the other two rcts (37, 38) included in the reviews had more robust methodologies and lesser risk of bias (e.g., comparable groups, test results for all participants, and longer follow-up periods). the studies did not find any significant differences between respirators and masks for clinical and laboratory outcomes, in both low and high-risk settings. a recent systematic review of observational studies suggests that "n95 respirators might be more strongly associated with protection from viral transmission than surgical masks" (39) . regrettably, of 10 studies, not a single one directly compared respirators to masks, and nine of them looked at sars or mers rather than sars-cov-2. the lone covid-19 study only compared n95s to no masks and did not include medical masks at all (40) . the researchers drew their conclusions by comparing the pooled results for n95 studies with the pooled results for mask studies, obtaining a p value for interaction by mask type that was borderline significant after partial adjustment. however, the difference between the two groups was not statistically significant (overlapping confidence intervals) and the very high heterogeneity (i 2 ϭ 88%) could have undermined the validity of the meta-analysis. also, the presence of agps was unknown in 7 of 10 studies: since all the studies were done in a hospital setting where agps frequently occur, and n95s are known to be superior in high-risk settings, failure to adjust for agps will skew the results in favor of n95s. finally, all 10 studies were observational and many did not control for important confounding factors, leading the authors themselves to rate the overall certainty for mask data as low. since many trials studied airborne viruses (e.g., influenza) and included exposure to agps, it may seem surprising that the vast majority of reviews, past and present, did not find respirators to be superior to masks. a possible explanation is that, while not designed to filter very fine particles, the medical mask might nonetheless be effective in blocking the low levels of aerosols produced in most health care contexts. a few case reports seem to support this hypothesis. for example, in a study of two severely ill covid-19 patients who were not initially isolated, contact tracing identified 421 hcws, of whom only 8 tested positive (41) . all infected hcws had close and prolonged contact without wearing the mask or ocular protection and had been present during agps. on the other hand, all of the hcws who used droplet and contact precautions did not get infected, leading the authors to conclude that there was no evidence of airborne transmission. similarly, two studies reported on 34 and 41 intensive care hcws exposed to an intubated and mechanically ventilated covid-19 patient: 50 and 85% wore surgical masks, respectively, and the others wore n95s, yet none were infected according to clinical and laboratoryconfirmed results (42, 43) . furthermore, a covid-19 patient who stayed 35 h in an open cubicle of a general ward, coughed frequently, and received high-flow oxygen at 8 liters/min, did not infect any of the 71 staff members and 49 patients, of which 7 and 10, respectively, had close contacts wearing either n95s or masks (44) . finally, strict contact and droplet precautions, as well as the use of masks rather than respirators, completely prevented nosocomial transmission from three community-infected hcws to coworkers and patients in an italian hospital (45) . as for the effectiveness of medical masks as source control (blocking particles emitted by infected individuals), clinical trials are scarce (46) (47) (48) , and they suggest a reduction of clinical but not laboratory-confirmed viral illnesses. therefore, we must turn to lower levels of evidence (e.g., laboratory studies) for further guidance. the ability of protection devices to control either source emission (e.g., infected individuals) or exposure prevention (e.g., hcws) has been the subject of several laboratory studies, whose findings are summarized in table 3 . the majority show high filtration capacity for both masks and respirators. the latter, however, are known to provide better protection against fine particles (ͻ5 m) because of a far superior fit factor. interestingly, source control with masks may be superior to exposure prevention by either respirators or masks. although these studies provide relevant information on the theoretical performances of protection devices, the experimental generation process and particle sizes may not resemble natural respiratory activity. also, many studies suffer from major limitations and inconsistencies in design: the use of different respiratory viruses with distinct behaviors, the lack of information on the size distribution of particles tested, the use of nonstandardized test particles (e.g., in contrast to standard respirator testing protocols), selection bias for ballistic behavior (petri dish sampling) rather than aerosols (air sampling), and confounding biases (e.g., fit factor and variable cough intensities). more importantly, many laboratory studies fail to account for crucial clinical and behavioral factors. for example, studies have reported lower adherence to n95 respirators compared to medical masks, due to higher rates of adverse events (35, 36, 49) . in one study on the tolerability of respirators in hcws, the probability of discontinuing respirator use during an 8-h work shift was around 50 to 70%, despite regular 15-or 30-min breaks every 2 h (50) . other studies show that one of the most challenging steps in donning and doffing is n95 use, which can result in a higher risk of contamination (51, 52) . in addition, an important, yet overlooked factor is the fitting of the device on the face (or the degree of leakage of particles around the edges). the fit factor varies between mask models and is typically very high for respirators, which is probably its main advantage. however, a poorly fitted respirator could perform no better than a loosely fitting mask (53) . seals used in some laboratory studies are poor surrogates for actual fitting on a hcw. finally, during exposure to covid-19 patients, hcws are instructed to wear ocular protection in addition to masks, and yet very few studies examine the combined effects of overall ppe. some experiments have shown that masks integrated with visors (54) and face shields individually (55) are protective not only against droplets but also aerosols (but efficiency decreases with exposure time). the vast majority of epidemiological studies that analyze sars-cov-2 outbreak patterns (case identification, contact tracing, epidemiological curves, and basic reproduction number or r0 estimates), undertaken in a variety of contexts, including health care facilities (41) (42) (43) (44) (45) , homes (56) , churches (57), fitness facilities (58), call centers (59), airplanes (60) , and company conferences and tour groups (61) , are in agreement: contact and droplets were the probable modes of transmission. rather than long-range propagation and frequent mass outbreaks typical of airborne patterns, the distribution of infected individuals was strongly correlated with close encounters and secondary attack rates were estimated be very low, around 5% (62) . rather than high r0 estimates typical of airborne viral pathogens such as chickenpox (5 to 11) (63) and measles (6 to 27) (64), community reproduction numbers fell between 2 and 4 (65, 66) and were easily lowered by droplet and contact precautions (67) . moreover, the who's largescale epidemiological analysis of 75,465 covid-19 patients did not confirm any cases of long-range airborne transmission (68) . in health care settings, the use of medical masks appears to be sufficiently protective of hcws exposed to covid-19 patients, as mentioned previously. several epidemiological reports from hospitals around the world even show little or no nosocomial transmission in the absence of recommended ppe (i.e., no n95s or masks during agps or improper mask use during close contact). combining the findings of six studies, out of a cumulative total of 295 hcws exposed to covid-19 patients without proper protection, only 5 hcws were infected. all five workers either did not wear any mask or used a mask intermittently during an agp or prolonged exposure (ͼ60 min) (69) (70) (71) (72) (73) (74) . these low levels of transmission from nonisolated covid-19 patients to nonequipped hcws are not suggestive of significant airborne transmission and support the effectiveness of basic pci measures beyond ppe. nonetheless, some epidemiological evidence is compatible with short-range airborne transmission. the washington choir outbreak is known for linking aerosolization from loud vocalization (i.e., singing) to rapid spread; however, the index case was symptomatic rather than asymptomatic as reported by the media (75), and multiple opportunities for droplet or fomite transmission were revealed in the published investigation (76) . in turn, the well-known outbreak at the guangzhou restaurant has been the subject of controversy: based on epidemiological data, one research team determined that droplets, expelled further than usual by air conditioning, were the probable source of transmission from an index patient to two neighboring tables (2); a second team, based on computer modeling and a tracer gas (a surrogate for exhaled particles), ruled in favor of airborne transmission (preprint article [77] ). moreover, a recently published study analyzed an outbreak involving two groups who rode separate buses to attend a 128-participant worship event (78) . while no transmission occurred on bus 1, 23 passengers on bus 2 were infected, some of whom were sitting up to 5 m away from the index case. seven other participants who did not ride on the buses were infected, all of whom reported close contact with the index case during the outdoor event. since proximity to source was not correlated with infection risk in the bus, but window and door seats seemed to be protective, the researchers hypothesized that bus 2's closed environment and air recirculation enabled airborne transmission to occur. furthermore, the widely studied diamond princess cruise ship outbreak is still up for debate. based on epidemiological data showing exclusive in-room transmission following imposed quarantine, as well as no correlation between infection patterns and central ventilation system, one research team concluded that close contacts and fomites were the main transmission routes (preprint article [79] ). in support of this view, an environmental study failed to detect any virus in air samples despite widespread positive surface sampling; however, passengers had disembarked at the time of sampling (80) . conversely, a modelization study simulating the cruise ship outbreak found that the epidemic models which best predicted the empirical data suggested predominant short-range and long-range airborne transmission (preprint article [81] ). finally, two studies (82, 83) analyzed the impacts of public health policies on the epidemiological curves of highly impacted regions: the first compared wuhan, italy, and new york city (nyc) while the second compared 15 u.s. states. according to the authors, mask-wearing but not social distancing (quarantine, stay-at-home, and lockdown) policies were effective in curtailing covid-19 outbreaks, suggesting that the main route of transmission is airborne rather than contact and droplets. however, the studies have come under criticism for not accounting for major confounding biases, such as differences between the three regions in terms of timing of lockdown (at ͼ9,000 confirmed cases in italy and nyc [84, 85] compared to 495 confirmed cases in wuhan [86] ), public health policy (e.g., contact tracing efficiency, testing criteria, and access), and population demographics (87) . in addition, using the date of governmentmandated mask-wearing as the start point for regression slopes is misleading, since the impacts of any new policy on epidemiological curves are delayed and nonlinear, especially given uneven compliance to mask-wearing, typically around 50% in the united states. (88) , but variable between states, compared to over 95% in asia (89) . if we further scrutinize nyc (as well as other states), it appears that the number of daily new cases, hospital admissions, and deaths started to fall before the mask-wearing order (84) , thus warranting an alternative explanation for the decline, such as an increasing proportion of immune individuals or the adoption of more aggressive testing. moreover, researchers could not explain why certain states managed to control their outbreaks without mask-wearing policies and others did not show a decline in new or cumulated cases after facemask adoption. beyond the airborne versus droplet debate, there is consensus among epidemiologists: prolonged short-range exposure is the main risk factor. interestingly, the revised airborne model presented in the conclusions: proposed model (below), involving inhalable aerosols, can accurately explain epidemiological observations as well as the dynamics of several contentious outbreaks. despite some caveats, sars-cov-1 studies may be useful to understand sars-cov-2, given that they share around 80% of their genomic sequence (66) . a well-studied outbreak at amoy gardens in hong kong, a high-rise housing estate where ͼ300 tenants were confirmed infected despite little contact between them, was studied by different teams (90, 91) . the majority agree on airborne transmission of sars-cov-1, originating from the aerosolization of feces and urine through hydraulic action (i.e., toilet flushing) of an index patient who presented with diarrhea and high viral load in excrements. this particular outbreak involved primarily environmental and engineering factors such as unsealed floor drain traps, bathroom fans causing negative pressure, bathroom fixtures contributing to drain overload or backflow, and the specific configuration of the exhaust system, which contributed to drawing aerosolized sewer droplets from the plumbing system back into the bathrooms and spreading them throughout the building (92) . the involvement of respiratory aerosols was not hypothesized. more relevant to health care settings is a hong kong hospital outbreak study on medical students exposed to an index sars patient: proximity with the patient was the main risk factor, but the duration of contact did not appear to be associated with transmission. the researchers conclude that the mode of transmission was probably through droplets and contact, but airborne transmission could not be excluded, especially given the presence of a potential agp (30-min nebulizer therapy four times a day) (93) . furthermore, in a canadian study, air samples were collected from 15 sars patient rooms in low-risk and high-risk settings, as well as four adjacent nursing support areas: 2 of the 40 wet air samples and none of the 28 dry air samples were pcr positive (94) . the two positive samples were both from the room of a single recovering sars patient where agps did not appear to be performed. subsequent viral culture; however, turned out negative. as for protection devices, a case-control study in five hong kong hospitals showed no difference in infection rates between hcws wearing a mask or a respirator, when exposed to sars patients (95) . other observational studies (96) (97) (98) done in high-risk settings (including agps) suggest possible n95 superiority, but the studies either did not adequately compare the two equipment types or did not obtain statistically significant results. other lower levels of evidence for sars-cov-1 come to similar conclusions regarding ppe. no nosocomial transmission was found in hcws from eight u.s. hospitals, despite several of them not wearing any masks and 5% of them being exposed to agps (99) . furthermore, no nosocomial transmission was found in vietnamese hcws exposed for 3 weeks to hospitalized cases, wearing only medical masks (100) . however, given the differences between sars-cov-1 and sars-cov-2 (e.g., peak viral load, asymptomatic transmission rates, and mortality rates), direct extrapolations from one virus to the other must be made with caution. similarly to the current pandemic, the significance of airborne transmission for the previous sars remains uncertain to this day, as the prerequisites (viral load, infectivity, and tropism) are not clearly met. unfortunately, sars-cov-1 seems to suffer from the same lack of rigorous clinical trials as its contemporary cousin. data from air and no-touch surface sampling studies (tables 4 and 5) conducted in covid-19 patient rooms and health care facilities are often cited to support airborne transmission. unfortunately, interstudy comparisons are complicated by the diversity of methodological approaches. for instance, positive air samples correlate with patient features (e.g., viral load and symptom intensity and duration), ventilation parameters, and cleaning procedures, but these elements are not always mentioned or detailed. moreover, large variations are reported in terms of total volume of air collected (ͻ100 liters to up to 10,000 liters), flow rates (3.5 to 300 liters/min), sampling duration, and technique (gelatin versus polycarbonate filtration, dry cyclonic sampling versus condensation sampling). furthermore, the sampling of no-touch surfaces, defined as areas typically out of reach of human contact or droplets and therefore assumed to be contaminated by aerosols only, is often poorly described and not always comparable to air samples. given that each design is associated with its own set of advantages and limitations (e.g., longer duration of air sampling may increase detection probability but decrease infectivity), there is no easy conclusion to be drawn when comparing studies. the majority of published and unpublished studies detected viral rna in the air and on no-touch surfaces (table 4 ), but some did not (table 5) . unfortunately, few positive studies included viral cultures. the main limitations of these studies were the lack of information on particle sizes and concentrations, unknown or suboptimal air sampler location, unknown time interval between aerosol production and collection (air or surface), and possible false negatives (e.g., negative pressure, open windows, and insufficient sampling volume or duration). for the studies that calculated viral concentrations from the environmental samples, various protocols, target genes (e.g., orf1ab/ rdrp, e, n, and s), and chemistry detection technology, should caution against direct comparisons. most studies were carried out in both low-and high-risk areas, and frequently in intensive care units (icus) where agps commonly occur and ventilation is optimized. many studies, however, did not specify the general risk level and did not indicate if agps were carried out during sampling. therefore, positive air and no-touch surface samples could not be clearly associated with an emission source (i.e., natural aerosolization versus agps) or risk factors (e.g., ventilation rate). this makes the results hard to generalize to most low-risk health care settings, such as long-term-care facilities. negative results from air sampling studies in home and commercial settings (80, 101) , in the definite absence of agps, also add to the uncertainty. it is worth noting that when researchers modelized aerosol emission during normal breathing, the observed concentrations of airborne particles were low, frequently under the detection limit for most air sampling approaches (102) . this could explain the negative results of many studies (table 5) . nonetheless, air and no-touch surface sampling studies support the presence of natural and/or intervention-generated aerosols in covid-19 health care facilities. however, the infectivity of these aerosols and their significance as a transmission route, beyond the mere detection of viral particles, remain uncertain. indeed, a better understanding of viral resistance to airborne stress is key to estimating infectious risk. three published studies (103) (104) (105) included viral cultures from air samples, all of which were negative; however, the santarpia et al. study (103) observed indirect signs of viral replication in two of their samples, including a mild cytopathic effect upon microscopic inspection after 3 to 4 days. on the other hand, in two unpublished studies, santarpia sars-cov-2 and health care worker protection clinical microbiology reviews et al. (106) and lednicky et al. (107) succeeded in obtaining positive cultures. the former used innovative methods such as detection of viral rna in supernatant and western blotting to yield interesting results. however, data scrutiny is impeded by the absence of c t values in the manuscript. in turn, the latter study would benefit from a thorough peer review process given that its methodology is not clearly detailed, and total and culturable viral counts seem implausible, since they are orders of magnitude higher than previously reported in the literature. the use of a condensation-based air sampler could perhaps explain the unusual results. the fact that few research teams have attempted to culture the virus, and many of those who have did not succeed, could imply that sars-cov-2 aerosols are scarce or weakly infectious. however, multiple other factors could be at play. viral cultures must be done in biosafety level 3 facilities and are therefore not easily accessible to some research teams. even when culturing is possible, viral shedding dynamics may be unpredictable or intermittent, leading to failed detection within the time frame of air sampling (108) . furthermore, the sampling process of aerosols, in itself, may induce substantial damage to viruses and alter their integrity and, consequently, their infectivity (109) . finally, current culture techniques may not be optimal for the low viral concentration found in air samples. increased sensitivity could be achieved with a bioassay or alternative methods such as electron microscopy, detection of viral proteins, and rt-qpcr in culture lysis and supernatants (106) . lastly, studies involving the in vitro generation of sars-cov-2 aerosols with jet collison nebulizers have been widely cited in support of airborne transmission. using this method, the well-known van doremalen et al. letter measured infectious titers per liter of air in a simulated aerosolized environment and showed stability of the sars-cov-2 virus in aerosols for up to 3 h, with a half-life of 1.2 h (110). another similar study made headlines because the aerosols produced were stable for up to 16 h (111) . as with all in vitro models for bioaerosols, while they provide precious information on virus properties in aerosol state, including relative stability (which seems to be high) and comparative viral behavior, it is uncertain whether the mechanically produced sars-cov-2 aerosols exhibit the same properties as naturally generated ones. therefore, such experimental studies are generally considered of low applicability to clinical settings. tragic outbreaks in long-term-care facilities (ltcs) have plagued many countries in europe (112) and north america (113) , with astonishing death tolls. some facilities report 100% resident infection rates, high hcw infection rates, as well as faulty ventilation systems (114), triggering intense debate over potential airborne transmission. while aerosols could have contributed in cases involving inadequate ventilation (115) , other explanations are also conceivable. some have justified the devastating statistics by pointing to higher viral loads (116) or longer infection periods (117) in the elderly, two phenomena likely attributable to the weakening of the immune system with age. notwithstanding, ltcs are fundamentally vulnerable to covid-19 because of an array of predisposing risk factors (118, 119) . unlike the general adult population, covid-infected residents in ltcs are not always capable of communicating their symptoms and frequently have atypical clinical presentations, such as diarrhea, delirium, or falls (120) . on the other hand, between 50 and 75% (121, 122) of them are asymptomatic or presymptomatic at the time of their positive test. these geriatric features complicate and delay case detection. the typical patient profile also leads to poor compliance with infection prevention and control (ipc) practices: most residents have neurocognitive disorders and behavioral symptoms, but some also have mental health disorders or intellectual disability, which means isolation, mask-wearing, and hand hygiene are often impossible. rates of resident noncompliance can reach almost 100% in certain special care units (e.g., wandering ward). moreover, a majority of residents with severe loss of functional autonomy requiring several hours of proximity care per day (e.g., personal hygiene and bath, urinary and bowel elimination, feeding, and medication administration), means close and sustained contact between hcws and infected patients (without source control for the most part) and consequently, higher infection risk on both sides (123) . structural and administrative impediments also come into play. some ltcs have high bed occupancy rates and tight physical spaces (e.g., shared bedrooms and bathrooms), where distancing becomes a challenge and cross-contamination an inevitability (124) . with high population density and limited space, it is very difficult to efficiently segregate patients into zones according to infectious status, leading to mixed units and high infection rates. moreover, some facilities have defective ventilation systems (115) , while others have no mechanical ventilation at all, and must rely on opening windows for air exchange. most importantly, many already understaffed ltcs were hard hit by pandemic-related absenteeism and had to resort to mobilizing staff between units and facilities or calling on lesser-trained external staff to fill in; this element exaggerated all the other risk factors because it hindered the detection and isolation of suspected cases, the deployment of covid-19 units with dedicated staff, the optimal application of ipc practices, and the overall quality of care (125) . unfortunately, despite ltcs being at the epicenter of many regions' epidemic, data are still lacking. studies on transmission modes specific to this geriatric subgroup, where various clinical, administrative, and environmental factors intersect, would be very revealing. most authorities agree with the who recommendations for droplet and contact precautions with covid-19 patients. in the united kingdom (126), canada (127), france (128) , switzerland (30), spain (129), portugal (130) , and australia (131), medical masks are indicated in most situations and respirators are required only in high-risk settings involving agps. recently, the who has acknowledged that "short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out" but specifies that the significance of covid-19 airborne transmission has not been convincingly demonstrated and requires further research (1) . while the european society of intensive care medicine and society of critical care medicine (132) is also in line with who ppe recommendations, the european centre for disease prevention and control began by recommending respirators at all times, but backtracked in recent updates and now states that both equipment types are appropriate outside of agps (133) , in agreeance with the infectious diseases society of america (idsa) (134) . on the other hand, the united states (135), south korea (29), singapore (136) , and china (137) recommend respirators for routine care. the u.s. cdc states that hcws should wear an n95, but a facemask is a suitable alternative if a respirator is not available. in summary, most western countries have adopted similar guidelines in line with who recommendations, but comparisons with countries in other parts of the world were not possible due to language barriers. surprising attack rates have been reported. possible explanations include the high presymptomatic contagion of certain individuals (138) , as well as the many asymptomatic or paucisymptomatic cases (139) who seem to have similar viral loads to their symptomatic counterparts (140) . furthermore, unlike sars-cov-1 which reached peak viral load (and therefore contagion) at day 7 to 10 from the start of symptoms (141), viral load seems to peak right before the advent of symptoms (108) . given these data, certain researchers estimate that 44% of transmission happens in the presymptomatic phase (108) . finally, nasopharyngeal viral load appears to be much (up to 1,000 times) higher than that of the first sars (142) . we are therefore faced with a very contagious virus that can silently infect a large number of people. moreover, another possible mode of transmission that remains to be elucidated is through fomites. few studies look at sars-cov-2 survival on surfaces. a widely cited experiment showed that the virus could subsist between 4 h (on copper) and 72 h (on plastic) (110) . however, the study took place under experimental conditions (laboratory surface inoculation, at a stable temperature of 21 to 23°c) which do not represent droplet deposition on surfaces in clinical contexts nor the variations of typical indoor environments. nonetheless, the potentially prolonged stability of coronaviruses on surfaces (143) , as well as the extensive environmental contamination reported by many surface sample studies in health care settings (108, (144) (145) (146) (147) , needs to be confirmed by future research, including viral cultures for infectivity. possible fecal transmission is also worth considering. a significant proportion of patients declare gastrointestinal symptoms before respiratory symptoms, and it is even a predominant form of presentation in some individuals (148) . in addition, severe covid-19 cases appear to have more gastrointestinal symptoms than mild or moderate cases (149) . a meta-analysis of over 4,000 patients reported 48% pcr-positive stool samples, of which 70% remained positive even after nasopharyngeal pcr had turned negative (150) . endoscopic studies also found rna in the esophagi, stomachs, duodena, and recta of patients with severe gastrointestinal symptoms (151) . finally, two studies showed the toilet was among the most contaminated areas in indoor settings (152, 153) : interestingly, the patient who's toilet air sample was positive had a negative exhaled breath sample, warranting the consideration that detectable airborne sars-cov-2 could originate from fecal rather than respiratory aerosols. as with air, a limited number of studies have been able to culture infectious viruses from stools (154, 155) , supporting infectivity. in theory, fecal transmission could occur through different routes, including contact (e.g., while changing incontinence briefs), short-range aerosolization (i.e., inhalation), or long-range aerosolization due to toilet flushing (156) . the latter was well established in the sars-cov-1 amoy gardens outbreak and was recently considered the main mode of transmission in a sars-cov-2 outbreak involving a high-rise building in china, where the nine infected cases lived in three vertically aligned flats connected by drainage pipes in the master bathrooms (157) . hcws constitute a high-risk population for infection (158) . however, the contribution of nosocomial transmission was perhaps overestimated at the beginning of the pandemic, since recent genome-sequencing studies have highlighted the importance of community-acquired infection among hcws (159) . for instance, with epidemiological and genomic data on 50 hcws and 10 patients at hospitals in the netherlands, researchers linked these infections with three different clusters, two of which showed local circulation in the community (160) . within each cluster, "identical or near-identical sequences in health care workers at the same hospital, and between patients and health care workers at the same hospital, were found, but no consistent link was noted among health care workers on the same ward or between health care workers and patients on the same ward." the authors therefore concluded that the patterns observed were consistent with multiple introductions into the hospitals through community-acquired infections. similarly, studies are pointing to community transmission dynamics and public policies (e.g., universal mask-wearing) as the main drivers of hcws infection (161) (162) (163) . nonetheless, given that hcws can both infect patients and get infected from patients, workplace practices deserve a closer look. in the presence of a contagious virus and extensive environmental contamination in health care settings, any breach in protection, as small as it may be, can lead to infection. hcws who work regularly with covid-19 patients, especially those in close contact (e.g., patient attendants, nurse aides) can hardly maintain constant and perfect compliance with ipc practices. besides, risk exposure not only occurs with patients during ppe violations but also with other staff members in shared areas without ppe (e.g., cafeterias and changing rooms). unfortunately, few studies looked at ppe compliance during the covid-19 pandemic: one study reported very poor adherence to mask recommendations due to lack of use (almost 30%) or improper use (164) . before the pandemic, cornerstone practices such as hand hygiene were already poorly applied according to several studies in a variety of hospital departments (including icus) across different countries (165) (166) (167) . a drastic change in a short lapse of time appears improbable, especially in long-term-care facilities where the culture and philosophy are one of "home setting" rather than health care setting. moreover, hcws appear to have a false perception of their own compliance with hygiene practices: a mers-cov study showed an absence of correlation between staff's self-assessment and their observed behavior (168) . the researchers mention that most hcws understood the importance of hand hygiene but did not consistently apply it. even so, proper ppe use does not only depend on individual compliance and technique; it is a multidimensional issue with organizational, systemic, and political ramifications (169) . more importantly, ppe is neither the only nor the best way to protect hcws. in fact, when it comes to protection from occupational hazards, ppe is the last and least effective measure in the niosh hierarchy of controls (170) (see fig. 1b ). for the current pandemic and future ones, our priority should therefore be elimination strategies (e.g., decreasing bed occupancy rates, source control), engineering controls (e.g., segregated red zones and proper ventilation), and administrative controls (e.g., dedicated staff, adequate training, and strict enforcement of ipc regulations), ending with ppe (29) . unfortunately, we have seen, around the globe, many health care systems fail to meet the structural, human, and material challenges brought on by covid-19, and some hcws have paid the price for our collective unpreparedness. one final potential source for hcw infection could be the combination of risk factors for aerosol accumulation in certain exceptional circumstances, such as an overcrowded and underventilated long-term-care facility (115) , or makeshift hospitals such as we have seen built around the world (171) . while the vast majority of home and hospital environments are probably safe (172) , some care homes are located in old substandard infrastructure which relies on natural ventilation and does not allow for optimization of air exchange. it is plausible that under these specific conditions, normally minimal levels of infectious respirable aerosols could reach a threshold where classic airborne transmission becomes significant. while we wait for future research to confirm this scenario, we must strive to control what we can, eliminating physical, environmental, and administrative risk factors to protect frontline workers (173) . drawing the line between precaution and excess is a fundamentally subjective process. many experts agree that current droplet and contact precautions are adequate in low-risk settings. however, some prefer to exercise precaution by recommending respiratory protection with critically ill patients (e.g., severe desaturation or tachypnea), arguing that these clinical features predict progression to agps such as intubation (174) . others consider that the minimum precautionary practice is universal n95 use. finally, some argue that only drastic measures such as full head hoods and full-body suits, often seen in china, are sufficiently protective. in the presence of diverging opinions on the definition of so-called precaution, it seems reasonable to use an evidence-based approach to ppe recommendations. the bulk of evidence, until now, indicates that the medical mask is protective in low-risk settings and the respirator is required only for agps, although higher levels of evidence in the future may tip the balance the other way. long-term care facilities, where the risk level may at times be considered high despite the absence of agps, deserve special attention from researchers. lastly, one could argue that our collective but rather limited energy, time, and resources should be invested in the most impactful areas: proven practices that achieve broad consensus and transmission routes that appear to be predominant. for sars-cov-2, long-winded debates on the gray zones and the applicability of the precautionary principle sometimes distract from crucial measures, such as hand hygiene, source control, and optimal ventilation (175) , which are uncontroversial and highly effective, yet still unevenly applied in some settings such as long-term-care facilities. we are in favor of a return to core ipc principles, which should dominate the scientific conversation around covid-19 management. beyond the alarming statistics, several success stories around the world prove that much can be achieved quickly and efficiently with basic yet effective practices (45, (176) (177) (178) , without the need to resort to elaborate theories or equipment. this article is an in-depth literature overview attempting to answer frequently asked questions about droplet and airborne transmission. although not a systematic review, it goes deeper than current narrative reviews and has important implications for ipc practices, hcw protection, and future research. however, there are several limitations. the first is the controversial distinction between droplets and aerosols, still commonly used in much of the scientific literature, although deemed arbitrary and inaccurate by many experts. natural generation of particles belonging to a broad range of size, containing various concentrations of infectious agents, is probably concurrent rather than mutually exclusive, and transmission patterns are likely on a continuum rather than dichotomous. our proposed model addresses this issue. going forward, we are in favor of adapting public health policies and ppe recommendations to include a broader industrial hygiene-inspired definition of aerosols, as presented above, in order to lessen confusion and better represent the nuanced and complex reality of sars-cov-2 transmission. the second major limitation is the lack of clinical studies on sars-cov-2 transmission and ppe effectiveness, meaning that many conclusions are drawn from lower levels of evidence, extrapolations from other viruses, and laboratory and experimental studies. the available literature, however, is mostly consistent: while airborne transmission exists under certain conditions, there is limited direct evidence of it, especially in low-risk health care settings. given the very high viral load typical of sars-cov-2 infections, it is surprising that, after several months of pandemic, many air samples turn out negative or weakly positive, and subsequent positive cultures remain scarce. this may be attributed to the many logistical and technical limitations associated with air sampling and viral cultures, as mentioned previously, which could underestimate airborne infectivity. we must therefore rely primarily on clinical evidence (trials on masks and epidemiological studies) to study transmission; for now, it suggests that the classic airborne route is not significant. a broader airborne model, involving the short-range inhalation route, could better explain current observations. third, only a few national and international guidelines are compared because of the lack of translated documents. a thorough search of guidelines from comparable countries across different continents would allow for an unbiased comparison but is very challenging in practice. while impatiently waiting for future studies, especially clinical trials, to dispel remaining uncertainties and provide definitive answers to the questions raised here, we would like to propose a revised model for sars-cov-2 transmission, involving inhalable aerosols and favorable conditions for airborne transmission (fig. 1) . the premises of this model are based on cumulative data and clinical observations. in light of the positive air and no-touch surface samples found in health care facilities, respiratory sars-cov-2 aerosols probably occur, but many of their attributes are yet unknown; studies thus far seem to suggest these aerosols are short-range and dilute with distance (102, 103, 144) . similarly, epidemiological studies do not support the existence of long-distance aerosol propagation: the four outbreaks most often cited as evidence of airborne transmission (the washington choir, the guangzhou restaurant, the eastern chinese bus riders, and the diamond princess cruise ship) all involved individuals who were in relatively close contact for a prolonged period of time, in an enclosed space, with the presence of enabling factors (e.g., crowdedness, air currents, and poor ventilation). indeed, these conditions seem necessary for respiratory airborne transmission to occur. fecal aerosols, on the other hand, may be more common due to toilet flushing, but further studies are needed to clarify their role and distinguish them from respiratory aerosols. worst-case scenario: no protection on either the sick patient (source) or the health care worker (exposure), emission of particles of various sizes (droplets and aerosols) during natural respiratory activity (breathing, talking, and coughing), entry of infectious inhalable aerosols, and impaction in the nose where viral receptors are abundant and infectivity is greatest. (b) best-case scenario and niosh hierarchy of controls: source control (mask-wearing by the sick patient), engineering control (optimal ventilation), and exposure control (droplet-contact ppe worn by the health care worker) to prevent short-range droplet and inhalable aerosol transmission. clinical microbiology reviews moreover, to solve the mystery of particle size, we must first acknowledge that airborne transmission is not exclusive to small aerosols: some larger particles typically classified as droplets may remain airborne, especially if suboptimal airflows contribute to their preservation in suspension and reduce their dilution (179) . thus, inhalable aerosols are the ideal candidate to explain current findings, because they exhibit shorter travel distance and air suspension time than respirable aerosols while having greater potential for infection because of their higher probability of containing virions (16) . furthermore, because inhalable aerosols are larger, they are more likely to deposit proximally in upper airways compared to respirable aerosols (180) , which is in line with the robust data suggesting that nasal cells are the main portal for initial infection, with a gradient of infectivity from the proximal (nose) to the distal (lungs) respiratory tract (21, 22) . therefore, transmission of short-range airborne and inhalable aerosols could explain the seemingly contradictory finding that there are viruses in the air and transmission between individuals without contact, but lack of convincing clinical evidence of classic airborne transmission (i.e., long-distance ranges and superiority of respirators). this size range could exhibit behaviors typical of both droplets and aerosols: higher viral load, airborne behavior, inhalation, and deposition in the nose. despite relatively shorter suspension time, inhalable aerosols become especially significant in the case of prolonged exposure and close proximity. in addition, they are less likely to follow air streams through leaks in the nonfitted mask, nor make it down to alveolar space, because of larger size, but rather will remain in nasal cells due to natural impaction processes. consequently, tight seals and superior filtration would not be required in most low-risk settings, as masks (with the help of face shields) could readily block these airborne particles. however, different categories of hcws may not be exposed to the same level of risk: an attendant who spends an hour feeding, bathing and positioning a patient will be at much higher risk of inhaling aerosols compared to a doctor who questions and examines a patient for 10 min. finally, ventilation parameters (air exchange rate, flow direction, and airflow patterns) would play a role, since they could contribute to enhancing or reducing airborne suspension and transmission (181) . this model is difficult to assess given the short-range distance and the short airborne stability, as well as the alteration of particle size during most air sampling processes (desiccation and impaction in liquid). however, we believe this novel paradigm, which departs from the outdated aerosol/droplet dichotomy, more accurately portrays the reality of naturally generated viral particles and the nuances in transmission patterns. broadening the "airborne" definition to inhalable aerosol exposure in the context of proximity care, and considering inhalation as a significant route of entry for the sars-cov-2 virus, could open up new paths of exploration. in summary, traditional droplets (larger particles with ballistic behavior that deposit onto surfaces), as well as our newly defined inhalable aerosols (particles that can be suspended, breathed in, and impacted at the nose, at the location of highest infectivity), could be the predominant modes of transmission of sars-cov-2. classic respirable aerosols, even if present, seem unlikely to be significant in routine health care contexts, possibly due to insufficient quantity, inactivation during aerosolization or shortly after, inability to colonize lower airways, and/or adequate blockage by masks (especially in combination with face shields). in the light of this revised model and the cumulative data analyzed in this review, in line with several major countries' guidelines, current droplet and contact precautions appear to adequately protect hcws in most non-agp settings, with perhaps the exception of proximity caretakers in poorly ventilated settings. nonetheless, since the health and lives of hcws depend on our better understanding of sars-cov-2, further investigation into all possible routes of transmission-whether airborne, fomite, or fecal-is warranted, especially in settings where they could synergistically contribute to outbreaks (e.g., long-term-care facilities). transmission of sars-cov-2: implications for infection prevention precautions. world health organization covid-19 outbreak associated with air conditioning in restaurant turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of covid-19 covid-19: effects of environmental conditions on the propagation of respiratory droplets recognition of aerosol transmission of infectious agents: a commentary air quality: particle size fraction definitions for health-related sampling a rosetta stone for understanding infectious drops and aerosols aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review niosh guide to the selection and use of particulate respirators visualizing speechgenerated oral fluid droplets with laser light scattering characterization of expiration air jets and droplet size distributions immediately at the mouth opening size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities origin of exhaled breath particles from healthy and human rhinovirus-infected subjects aerosol emission and superemission during human speech increase with voice loudness individual variation in susceptibility or exposure to sars-cov-2 lowers the herd immunity threshold the airborne lifetime of small speech droplets and their potential importance in sars-cov-2 transmission estimation of viral aerosol emissions from simulated individuals with asymptomatic to moderate coronavirus disease 2019 the role of particle size in aerosolized pathogen transmission: a review exhalation of respiratory viruses by breathing, coughing, and talking infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community hca lung biological network. 2020. sars-cov-2 entry factors are highly expressed in nasal epithelial cells together with innate immune genes sars-cov-2 reverse genetics reveals a variable infection gradient in the respiratory tract medical masks versus n95 respirators for preventing covid-19 in healthcare workers: a systematic review and meta-analysis of randomized trials use of n95, surgical, and cloth masks to prevent covid-19 in health care and community settings: living practice points from the american college of physicians (version 1) masks for sars-cov-2 and health care worker protection clinical microbiology reviews prevention of respiratory virus infections, including sars-cov-2, in health care and community settings effectiveness of n95 respirators versus surgical masks against influenza: a systematic review and meta-analysis medical masks and respirators for the protection of healthcare workers from sars-cov-2 and other viruses covid-19 pandemic and personal protective equipment shortage: protective efficacy comparing masks and scientific methods for respirator reuse personal protective equipment for healthcare workers during the covid-19 pandemic risk of sars-cov-2 transmission by aerosols, the rational use of masks, and protection of healthcare workers from covid-19 a scoping review of surgical masks and n95 filtering facepiece respirators: learning from the past to guide the future of dentistry a rapid systematic review of the efficacy of face masks and respirators against coronaviruses and other respiratory transmissible viruses for the community, healthcare workers and sick patients the need of health policy perspective to protect healthcare workers during covid-19 pandemic. a grade rapid review on the n95 respirators effectiveness facial protection for healthcare workers during pandemics: a scoping review a randomized clinical trial of three options for n95 respirators and medical masks in health workers a cluster randomized clinical trial comparing fit-tested and non-fittested n95 respirators to medical masks to prevent respiratory virus infection in health care workers respect investigators. 2019. n95 respirators versus medical masks for preventing influenza among health care personnel: a randomized clinical trial surgical mask versus n95 respirator for preventing influenza among health care workers: a randomized trial on behalf of the covid-19 systematic urgent review group effort (surge) study authors. 2020. physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis association between 2019-ncov transmission and n95 respirator use investigation of nosocomial sars-cov-2 transmission from two patients to health care workers identifies close contact but not airborne transmission events covid-19 and the efficacy of different types of respiratory protective equipment used by health care providers in a health care setting covid-19 and the risk to health care workers: a case report risk of nosocomial transmission of coronavirus disease 2019: an experience in a general ward setting in hong kong low rate of severe acute respiratory syndrome coronavirus 2 spread among health-care personnel using ordinary personal protection equipment in a medium-incidence setting surgical mask to prevent influenza transmission in households: a cluster randomized trial pilot randomised controlled trial to test effectiveness of facemasks in preventing influenza-like illness transmission among australian hajj pilgrims in 2011 cluster randomised controlled trial to examine medical mask use as source control for people with respiratory illness short-term skin reactions following use of n95 respirators and medical masks respirator tolerance in health care workers contamination during doffing of personal protective equipment by healthcare providers cognitive load and performance of health care professionals in donning and doffing ppe before and after a simulation-based educational intervention and its implications during the covid-19 pandemic for biosafety detection of infectious influenza virus in cough aerosols generated in a simulated patient examination room effectiveness of surgical masks against influenza bioaerosols efficacy of face shields against cough aerosol droplets from a cough simulator active monitoring of persons exposed to patients with confirmed covid-19 -united states connecting clusters of covid-19: an epidemiological and serological investigation cluster of coronavirus disease associated with fitness dance classes coronavirus disease outbreak in call center potential transmission of sars-cov-2 on a flight from singapore to hangzhou, china: an epidemiological investigation novel coronavirus outbreak research team. 2020. investigation of three clusters of covid-19 in singapore: implications for surveillance and response measures airborne transmission of sars-cov-2: theoretical considerations and available evidence estimation of basic reproduction numbers: individual heterogeneity and robustness to perturbation of the contact function the basic reproduction number (r0) of measles: a systematic review estimation of the basic reproduction number, average incubation time, asymptomatic infection rate, and case fatality rate for covid-19: meta-analysis and sensitivity analysis coronavirus disease 2019: covid-19 estimation of the time-varying reproduction number of covid-19 outbreak in china report of the who-china joint mission on coronavirus disease 2019 (covid-19). world health organization covid-19 infections among hcws exposed to a patient with a delayed diagnosis of covid-19 transmission of infection from non-isolated patients with covid-19 to health care workers transmission risk of sars-cov-2 to healthcare workers -observational results of a primary care hospital contact tracing escalating infection control response to the rapidly evolving epidemiology of the coronavirus disease 2019 (covid-19) due to sars-cov-2 in hong kong illinois covid-19 investigation team. 2020. first known person-to-person transmission of severe acute respiratory syndrome coronavirus 2 (sars-cov-2) in the usa transmission of covid-19 to health care personnel during exposures to a hospitalized patient a choir decided to go ahead with rehearsal: now dozens of members have covid-19 and two are dead high sars-cov-2 attack rate following exposure at a choir practice evidence for probable aerosol transmission of sars-cov-2 in a poorly ventilated restaurant community outbreak investigation of sars-cov-2 transmission among bus riders in eastern china transmission routes of covid-19 virus in the diamond princess cruise ship environmental sampling for severe acute respiratory syndrome coronavirus 2 during a covid-19 outbreak on the diamond princess cruise ship mechanistic transmission modeling of covid-19 on the diamond princess cruise ship demonstrates the importance of aerosol transmission identifying airborne transmission as the dominant route for the spread of covid-19 understanding transmission and intervention for the covid-19 pandemic in the united states covid-19: data summary. nyc health covid-19 dashboard estimation of local novel coronavirus (covid-19) cases in wuhan, china from off-site reported cases and population flow data from different sources formal request for the retraction of zhang 1,000 us adult citizens the role of community-wide wearing of face mask for control of coronavirus dis-sars-cov-2 and health care worker protection clinical microbiology reviews ease 2019 (covid-19) epidemic due to sars-cov-2 consensus document on the epidemiology of severe acute respiratory syndrome (sars). world health organization evidence of airborne transmission of the severe acute respiratory syndrome virus environmental transmission of sars at amoy gardens cluster of sars among medical students exposed to single patient detection of airborne severe acute respiratory syndrome (sars) coronavirus and environmental contamination in sars outbreak units effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (sars) sars among critical care nurses intubation of sars patients: infection and perspectives of healthcare workers illness in intensive care staff after brief exposure to severe acute respiratory syndrome lack of sars transmission among healthcare workers, united states lack of sars transmission among public hospital workers sars-cov-2 in environmental samples of quarantined households relative contributions of transmission routes for covid-19 among healthcare personnel providing patient care aerosol and surface contamination of sars-cov-2 observed in quarantine and isolation care investigating sars-cov-2 surface and air contamination in an acute healthcare setting during the peak of the covid-19 pandemic in london environmental and aerosolized sars-cov-2 among hospitalized covid-19 patients 2020. the infectious nature of patientgenerated sars-cov-2 aerosol viable sars-cov-2 in the air of a hospital room with covid-19 patients temporal dynamics in viral shedding and transmissibility of covid-19 methods for sampling of airborne viruses aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 persistence of severe acute respiratory syndrome coronavirus 2 in aerosol suspensions as many as half of europe's covid-19 deaths were people in long-term care facilities they're death pits": virus claims at least 7,000 lives in u.s. nursing homes. the new york times investigators look into catastrophic outbreak that infected all residents of tmr seniors' home, killing 70 outbreak of covid-19 in a nursing home associated with aerosol transmission as a result of inadequate ventilation temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by sars-cov-2: an observational cohort study viral load dynamics and disease severity in patients infected with sars-cov-2 in zhejiang province guide covid-19 pour les médecins en chsld usp ϭsharing. accessed 1 nursing homes are ground zero for covid-19 pandemic clinical characteristics of older patients: the experience of a geriatric short-stay unit dedicated to patients with covid-19 in public health-seattle & king county, cdc covid-19 investigation team. 2020. asymptomatic and presymptomatic sars-cov-2 infections in residents of a long-term care skilled nursing facility asymptomatic sars-cov-2 infection in belgian long-term care facilities lessons from mass-testing for covid-19 in long-term care facilities for the elderly in san francisco for-profit long-term care homes and the risk of covid-19 outbreaks and resident deaths restoring trust: covid-19 and the future of long-term care recommended ppe for healthcare workers by secondary care inpatient clinical setting, nhs and independent sector coronavirus disease (covid-19): for health professionals. public health agency of canada french society for hospital hygiene and the high council for public health. 2020. what face mask for what use in the context of covid-19 pandemic? the french guidelines prevención y control de la infección en el manejo de pacientes con covid-19 respiratory and facial protection: current perspectives in the context of the covid-19 pandemic national guidelines for public health units surviving sepsis campaign: guidelines on the management of critically ill adults with coronavirus disease 2019 (covid-19) infection prevention and control and preparedness for covid-19 in healthcare settings infectious diseases society of america guidelines on infection prevention for health care personnel caring for patients with suspected or known covid-19 interim infection prevention and control recommendations for patients with suspected or confirmed coronavirus disease 2019 (covid-19) in healthcare settings transmission modes of severe acute respiratory syndrome coronavirus 2 and implications on infection control: a review current knowledge of covid-19 and infection prevention and control strategies in healthcare settings: a global analysis contact tracing assessment of covid-19 transmission dynamics in taiwan and risk at different exposure periods before and after symptom onset inesss. 2020. covid-19 et détection moléculaire du sars-cov-2 chez les individus asymptomatiques. inesss follow-up of asymptomatic patients with sars-cov-2 infection clinical progression and viral load in a community outbreak of coronavirus-associated sars pneumonia: a prospective study virological assessment of hospitalized patients with covid-2019 persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents aerosol and surface distribution of severe acute respiratory syndrome coronavirus 2 in hospital wards air and environmental sampling for sars-cov-2 around hospitalized patients with coronavirus disease 2019 (covid-19) air, surface environmental, and personal protective equipment contamination by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) from a symptomatic patient environmental contamination by sars-cov-2 in a designated hospital for coronavirus disease 2019 review article: gastrointestinal features in covid᎑19 and the possibility of faecal transmission manifestations and prognosis of gastrointestinal and liver involvement in patients with covid-19: a systematic review and meta-analysis gastrointestinal manifestations of sars-cov-2 infection and virus load in fecal samples from the hong kong cohort and systematic review and meta-analysis sars-cov-2 and health care worker protection clinical microbiology reviews gastrointestinal symptoms of 95 cases with sars-cov-2 infection toilets dominate environmental detection of severe acute respiratory syndrome coronavirus 2 in a hospital covid-19 patients in earlier stages exhaled millions of sars-cov-2 per hour national health commission key laboratory for medical virology, national institute for viral disease control and prevention, chinese center for disease control and prevention, beijing, china. 2020. notes from the field: isolation of detection of sars-cov-2 in different types of clinical specimens can a toilet promote virus transmission? from a fluid dynamics perspective probable evidence of fecal aerosol transmission of sars-cov-2 in a high-rise building coronavirus pandemic epidemiology consortium. 2020. risk of covid-19 among front-line health-care workers and the general community: a prospective cohort study using virus sequencing to determine source of sars-cov-2 transmission for healthcare worker oude munnink bb, kluytmans van den bergh mfq, koopmans mpg. 2020. covid-19 in health-care workers in three hospitals in the south of the netherlands: a cross-sectional study first experience of covid-19 screening of health-care workers in england characteristics and transmission dynamics of covid-19 in healthcare workers at a london teaching hospital universal masking is an effective strategy to flatten the sars-2-cov healthcare worker epidemiologic curve rational use of face mask in a tertiary care hospital setting during covid-19 pandemic: an observational study infection prevention and control compliance in tanzanian outpatient facilities: a cross-sectional study with implications for the control of covid-19 assessing hand hygiene compliance among healthcare workers in six intensive care units systematic review of studies on compliance with hand hygiene guidelines in hospital care comparison of perceived and observed hand hygiene compliance in healthcare workers in mers-cov endemic regions committee on personal protective equipment for healthcare personnel to prevent transmission of pandemic influenza and other viral respiratory infections hierarchy of controls transmission of covid-19 virus by droplets and aerosols: a critical review on the unresolved dichotomy réduction du risque de transmission du coronavirus sars-cov-2 par la ventilation et gestion des effluents des patients. haut conseil de la santé publique how can airborne transmission of covid-19 indoors be minimised? inspq. 2020. covid-19: mesures de prévention et contrôle des infections pour les milieux de soins aigus: recommandations intérimaires. inspq it is time to address airborne transmission of covid-19 the long-term care crisis: how b.c. controlled covid-19 while ontario, quebec face disaster rapid responses in the emergency department of linkou chang gung memorial hospital, taiwan effectively prevent spread of covid-19 among healthcare workers of emergency department during outbreak: lessons learnt from sars preventing intra-hospital infection and transmission of coronavirus disease 2019 in health-care workers aerobiology and its role in the transmission of infectious diseases airborne transmission of communicable infection: the elusive pathway ventilation control for airborne transmission of human exhaled bio-aerosols in buildings grade handbook effectiveness of surgical and cotton masks in blocking sars-cov-2: a controlled comparison in 4 patients effectiveness of surgical, kf94, and n95 respirator masks in blocking sars-cov-2: a controlled comparison in 7 patients respiratory virus shedding in exhaled breath and efficacy of face masks potential utilities of mask-wearing and instant hand hygiene for fighting sars-cov-2 respiratory source control using a surgical mask: an in vitro study influenza virus aerosols in human exhaled breath: particle size, culturability, and effect of surgical masks testing the efficacy of homemade masks: would they protect in an influenza pandemic assessment the protection performance of different level personal respiratory protection masks against viral aerosol quantifying exposure risk: surgical masks and respirators a quantitative assessment of the efficacy of surgical and n95 masks to filter influenza virus in patients with acute influenza infection novel coronavirus outbreak research team. 2020. detection of air and surface contamination by sars-cov-2 in hospital rooms of infected patients aerodynamic analysis of sars-cov-2 in two wuhan hospitals is the coronavirus airborne? experts can't agree exhaled breath condensate: an overview sars-cov-2 rna detection in the air and on surfaces in the covid-19 hospital indoor air quality monitoring for the detection of sars-cov-2 (covid-19) virus environmental contamination of sars-cov-2 on surfaces, air-conditioner and ventilation systems a field indoor air measurement of sars-cov-2 in the patient rooms of the largest hospital in iran aerosol and environmental surface monitoring for sars-cov-2 rna in a designated hospital for severe covid-19 patients we thank magali-wen st-germain for the original design, creation, and development of fig. 1 , as well as patrick lane, sceyence studios, for the final version of fig. 1 . we thank stéphanie langevin, quoc dinh nguyen, luc trudel, and jean barbeau for their contribution in reviewing the original manuscript.both authors substantially contributed to the conception, design, analysis, and interpretation of data, as well as reviewing and approving the final version of the manuscript. we agree to be accountable for the contents.c.d. is holder of tier-1 canada research chair on bioaerosols. for this review article, we received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.we declare that we do not have commercial or financial relationships that could, in any way, lead to a potential conflict of interest with regard to this publication. key: cord-288483-y9fyslgo authors: zorko, david j.; gertsman, shira; o’hearn, katie; timmerman, nicholas; ambu-ali, nasser; dinh, tri; sampson, margaret; sikora, lindsey; mcnally, james dayre; choong, karen title: decontamination interventions for the reuse of surgical mask personal protective equipment: a systematic review date: 2020-07-10 journal: j hosp infect doi: 10.1016/j.jhin.2020.07.007 sha: doc_id: 288483 cord_uid: y9fyslgo background: the high demand for personal protective equipment during the novel coronavirus outbreak has prompted the need to develop strategies to conserve supply. little is known regarding decontamination interventions to allow for surgical mask reuse. aim: identify and synthesize data from original research evaluating interventions to decontaminate surgical masks for the purpose of reuse. methods: we searched medline, embase, central, global health, the who covid-19 database, google scholar, disasterlit, preprint servers, and prominent journals from inception to april 8, 2020 for prospective original research on decontamination interventions for surgical masks. citation screening was conducted independently in duplicate. study characteristics, interventions, and outcomes were extracted from included studies by two independent reviewers. outcomes of interest included impact of decontamination interventions on surgical mask performance and germicidal effects. findings: seven studies met eligibility criteria: one evaluated the effects of heat and chemical interventions applied after mask use on mask performance, and six evaluated interventions applied prior to mask use to enhance antimicrobial properties and/or mask performance. mask performance and germicidal effects were evaluated with heterogenous test conditions. safety outcomes were infrequently evaluated. mask performance was best preserved with dry heat decontamination. good germicidal effects were observed in salt-, n-halamine-, and nanoparticle-coated masks. conclusion: there is limited evidence on the safety or efficacy of surgical mask decontamination. given the heterogenous methods used in studies to date, we are unable to draw conclusions on the most efficacious and safe intervention for decontaminating surgical masks. as the global spread of novel coronavirus (sars-cov-2) continues to escalate, so has the demand for personal protective equipment (ppe), creating global shortages in the supply of n95 filtering face respirators (ffrs) and surgical masks. n95 ffrs are recommended by the world health organization (who) and the centers for disease control and prevention (cdc) for use by healthcare providers (hcps) caring for coronavirus disease (covid-19) patients requiring airborne precautions and during aerosol-generating procedures [1, 2] . therefore, n95 ffrs are most commonly needed for hcps in acute care and inpatient settings. in contrast, surgical masks are recommended for use by hcps to protect against the risk of droplet transmission in a broader range of inpatient healthcare settings, as well as outpatient settings (e.g. covid-19 assessment centres, long-term care facilities, and community care settings) [2] [3] [4] . as the supply of n95 ffrs is threatened, hcps may resort to use of surgical masks for airborne precautions [3, [5] [6] [7] . surgical masks are also recommended for use by patients with suspected or confirmed covid-19 to prevent potential spread in a variety of healthcare settings [2, 4] . several institutions now recommend that everyone entering the hospital setting wear a surgical mask [8] . these practices have created an unprecedented demand for surgical masks; unfortunately, the capacity for surge production of ppe is not sustainable in the long-term [5] [6] [7] . as most facemask ppe are designed for single-use, mask rationing and conservation is now a top priority globally [9] . mask reuse is now suggested as a crisis capacity strategy to conserve available supplies during a pandemic [2, [9] [10] [11] , and much attention has now turned to decontaminating facemasks. several strategies have been evaluated, including ultraviolet germicidal irradiation (uvgi), chemical disinfectants, and microwave-and heat-based methods; however, most of this literature has focussed on the decontamination of n95 ffrs [12] [13] [14] . the evidence on the efficacy and safety of decontamination and reuse of surgical masks is unclear. the objective of this systematic review was to evaluate and synthesize the evidence on decontamination interventions for the purpose of surgical mask ppe reuse. this systematic review protocol was designed a priori, registered on prospero (april 15 th , 2020; crd42020178290), and uploaded as a pre-print on open science framework (april 8 th , 2020; https://osf.io/8wt37/) [15] . the reporting of this systematic review is in accordance with the preferred reporting items for systematic reviews and meta-analyses (prisma) statement (appendix a) [16] . studies were eligible for inclusion if the following criteria were met: 1) the study was original research, including systematic reviews; 2) the study evaluated surgical facemask ppe or their components; 3) the study evaluated any intervention(s) to decontaminate, sterilize or treat surgical masks (applied either before or after their use) for the purposes of reuse as ppe; 4) at least one of the following efficacy or safety outcomes of interest was reported: a) mask performance (i.e. filtration efficiency and airflow resistance); b) reduction in pathogen load; c) in vivo infection rates following use of decontaminated masks; d) changes in physical appearance (i.e. mask appearance or physical degradation); e) adverse effects experienced by the wearer (e.g. skin irritation); or f) feasibility of the intervention (e.g. time, cost, resource utilization). we excluded editorials, case reports, narrative reviews, study protocols, clinical practice guidelines, grey literature, book chapters, and patents. two health sciences librarians (ls, ms) searched the following electronic databases from their dates of inception to april 8 th citations were imported into endnote and duplicates were removed. citations were uploaded to insightscope (www.insightscope.ca) for title/abstract screening and full text review. citation screening for title/abstract and full text review stages was conducted independently and in duplicate by a team of 11 reviewers recruited from mcmaster university, the university of ottawa, and the university of manitoba. prior to gaining access to the full set of citations, each reviewer read the systematic review protocol and was required to achieve a sensitivity of at least 80% when screening a test set of 50 citations (containing five true positives and 45 true negatives). reviewers achieving less than 80% sensitivity on the test set were provided with additional training. at both title/abstract and full text review, citations were excluded only if both reviewers agreed to exclude; disagreements were resolved by the study leads (dz, kc) where necessary. upon completion of full text review, the study co-lead (dz) reviewed all retained citations to identify potential duplicates and confirm eligibility. the reference lists of all citations included for full text review were searched for potential eligible citations that may have evaded the initial database search. data were collected using electronic data extraction forms (microsoft excel) modified from previous systematic reviews [12, 13] for this protocol and piloted by two investigators (dz, sg) on two eligible studies. data was extracted from the full text publication and any related publications, referenced published protocols, or supplementary materials. data extraction was completed in duplicate by two independent reviewers. where necessary, graphical data was extracted using sourceforge plot digitizer (http://plotdigitizer.sourceforge.net) and checked by the second reviewer for accuracy. disagreements were resolved by the study leads (dz, kc), where necessary. we planned to use recommended risk of bias tools where appropriate [17] ; however, in the absence of a standard risk of bias tool for laboratory studies, we applied objective assessment criteria developed for this purpose [14] . risk of bias was assessed by two reviewers independently and in duplicate at the study level by outcome in the following domains: study design, methodological consistency, population heterogeneity, sampling bias, outcome evaluation, and selective reporting (appendix c). the primary outcome for this study was efficacy and safety of the decontamination intervention, as determined by any of the following: mask performance (filtration efficiency [fe] and airflow resistance); reduction in pathogen load; in vivo infection rates following use of treated masks; mask appearance or physical degradation; or adverse effects experienced by the wearer. fe refers to the percentage of particles filtered at either a specific particle size or a range of particle sizes depending on the testing agent and standard used [18] . study results reporting percentage particle penetration were converted to fe units (i.e. fe% = 100 -particle penetration) for comparability [18] . airflow resistance is measured as the pressure drop across the mask, quantifying initial resistance to airflow in millimetres of water column height pressure per square centimeter (mmh 2 o/cm 2 ) [19] . reduction in pathogen load was reported as a log10 reduction factor from a time zero post-inoculation to a subsequently measured time point. if log10 reductions were not reported by the study, we calculated them using the study data provided (e.g. colony counts), where possible. a log10 reduction factor ≥ 3 was used as a reference indicating good germicidal effect [20] . the secondary outcome was feasibility of the intervention, such as the time, cost and resources required to implement the intervention. where results were presented for multiple experimental conditions, we reported the summary of results conducted at the harshest testing conditions, to allow a conservative interpretation of the outcomes evaluated [18] . primary outcome data was analysed descriptively and presented using absolute values and as a percent change where possible. no three studies evaluated the same intervention, nor applied similar test agents or conditions when evaluating outcomes. this precluded our planned quantitative analysis of outcomes [15] ; therefore, selected results from included studies were summarized descriptively. nine of 11 reviewers achieved the 80% sensitivity threshold on the test set. the two reviewers who did not achieve the 80% threshold were provided additional training regarding the screening protocol prior to citation screening. the review team achieved kappa values of 0.38 and 0.43 for title/abstract and full text screening respectively. study leads resolved conflicts in 3.0% title/abstract and 12.1% full text screening citations. of 2191 records identified through the initial database search, 1874 unique citations were reviewed and 33 full-texts were assessed for eligibility. twenty-six full texts were excluded for ineligibility, leaving seven unique studies for inclusion in our analysis (prisma diagram, figure 1 ). no additional citations were identified on review of reference lists. characteristics of included studies are summarized in table i . only one of the seven included studies evaluated interventions applied after surgical mask use (i.e. decontamination interventions) [21] . the remaining six studies evaluated interventions applied to masks or mask components prior to use to enhance antimicrobial properties and/or fe for potential reuse or extended use (i.e. pre-contamination interventions) [22] [23] [24] [25] [26] [27] . interventions in these studied were tested on whole masks, pieces of whole masks (referred hereafter as mask pieces) or pieces of individual mask layers (referred hereafter as mask layer pieces). risk of bias assessments for the included studies are described in appendix d. lin et al. [21] evaluated five decontamination interventions on mask pieces of two surgical mask types commonly used in taiwanese hospitals (gauze double-layer electret masks and oimo spunlace non-woven masks; models unspecified): dry heat (via rice cooker), high-pressure moist heat (i.e. autoclave), and three chemical agents (70% ethanol, 100% isopropanol, and 0.5% sodium hypochlorite [i.e. bleach]). study methods and findings are summarized in table ii . mask pieces were assessed for fe, airflow resistance, and physical characteristics following decontamination. fe was presented graphically for a range of particle sizes (0.0146μm to 0.594μm); we summarized the results for fe at 0.1μm, a standard particle size for particulate fe testing [18] . at baseline, gauze and spunlace mask pieces had fes of approximately 87% and 45%, respectively. fe in both mask pieces decreased after each decontamination intervention, but dry heat decontamination of gauze mask pieces demonstrated the smallest change (absolute fe reduction of 1.3%). moist heat and chemical decontamination interventions all resulted in greater absolute fe reductions (12% to 36%). bleach was the most damaging method, resulting in a 15.3% absolute fe reduction in spunlace mask pieces and destruction of gauze mask pieces. airflow resistance was assessed at a flow rate of 5.95 l/min [21] . statistically significant changes in pressure drop were reported following all decontamination interventions, except for dry heat and ethanol on gauze mask pieces [21] . airflow resistance results were not reported for bleach on gauze mask pieces (mask destroyed), or isopropanol for either mask type. physical characteristics were reported only for gauze mask pieces; the autoclave deformed and caused observable folds in the mask filter, and bleach destroyed the mask. physical characteristics following decontamination with other interventions, or in spunlace mask pieces, were not reported. germicidal effects of the five decontamination methods were not assessed. six studies evaluated five unique pre-contamination methods applied prior to mask use: four were antimicrobial interventions (nanoparticle emulsion [23, 24] , quaternary ammonium agent five studies evaluated the effects of their intervention on fe, airflow resistance, or both, applying different testing techniques (table iii) evaluated fe of gs5-coated mask layer pieces using aerosolized bacteria (0.5μm to 2.1μm particle diameter) and gs5-coated masks using nacl (0.075μm particle diameter), respectively. they found no statistically significant change in fe in gs5-coated masks or mask layer pieces (0.6% to 1.8% fe increase in polypropylene filter layer, 1.8% fe reduction in mask; p=ns). li et al. [24] used a potassium-fluorescein solution (particle size not reported) to evaluate fe in nanoparticle-coated full masks by: 1) the percentage potassium content of each mask layer relative to the potassium content of the whole mask; and 2) a seven point scale rating fluorescent stains on mask users faces. they found that the percentage potassium content of each mask layer was similar compared to uncoated masks (+2%, -3% and +1.5% absolute difference from control for outer, middle and interior mask layers, respectively), and similar ratings of fluorescent stains. airflow resistance was non-significantly increased (+1.4 ml/s/cm 2 ; p=ns). shen et al. [26] used an aerosolized pathogen simulant (1.0μm particle diameter) and also quantified fe as the proportion of particle content on each mask layer to that of the whole mask. they reported significant decreases in particle content on the repellant-coated outer mask layer coated with repellant (p<0.0001), but no changes to particle content on mask layers proceeding the filter layer (suggesting no changes to fe of the mask as a whole). airflow resistance was not assessed. (table iii) however, the germicidal effect of dry heat in surgical masks is unclear. bleach is not a safe method of decontaminating surgical masks; mask performance is significantly altered and safety data from n95 ffr studies suggest potential health risks associated with off-gassing [14] . with respect to pre-contamination interventions, salt film, gs5, nanoparticle emulsion and n-halamine mask coatings were reported not to have detrimental effects on mask performance. n-halamine and nanoparticle emulsion showed strong germicidal effects in masks (log10 reduction factors ≥ 3), which is consistent with their application in medical devices [34] , and food and water treatment [35] . salt films also demonstrated strong germicidal effects, but their application has been experimental to date [25] . an important consideration is that pathogen load was evaluated at different post-inoculation incubation time points in each study (i.e. 5 minutes to 24 hours); it is well-established that viral load reductions can occur by virtue of time [36] . ideal ppe decontamination methods should not only demonstrate effective reductions in pathogen load, but also preserve mask performance without causing any residual chemical hazard to the wearer [37] . results of included studies should be interpreted cautiously for the following reasons: 1) some of the mask types used in these experiments appear to have baseline fes below reference standards which may have affected the results observed [18] ; 2) experiments and test conditions applied to mask pieces or individual layers cannot necessarily be extrapolated to whole masks; and 3) testing methods and outcome assessments were heterogenous. unlike n95 ffrs, surgical masks are not certified under standardized national institute for occupational safety and health regulations. the food and drug administration (fda) recommends that several standards (astm f2101, astm 2299, mil-m369454c, or modified greene and vesley method) may be applied to surgical masks, complicating the evaluation of mask performance in this review [18] . there are many test conditions that can impact fe, such as particle size, particle charge (i.e. whether charge neutralized or not), and face velocity (i.e. flow rate); however, the fda and astm do not have uniform recommended standards [18] . the evidence that we have collated in this systematic review is therefore important and essential. this systematic review reveals that the body of evidence on decontamination interventions for surgical masks is scant compared to n95 ffrs. three recent systematic reviews have revealed 22 unique studies evaluating microwave irradiation, heat, chemical disinfectants, and uvgi for decontamination of n95 ffrs [12] [13] [14] . uvgi and vaporous hydrogen peroxide showed favourable evidence for germicidal effects without significant changes in mask performance; however, we were not able to find any publications evaluating these methods in surgical masks. the lack of research on surgical masks may stem from assumptions that methods effective in n95 ffrs can be extrapolated to surgical masks, and some institutions are already applying the same decontamination methods to both [38] . considering this systematic review demonstrates that mask types can perform differently after decontamination, and that surgical masks and n95 ffrs perform differently with aerosol challenges [21, 39], we cannot conclude that decontamination methods can be effectively or safely applied to all mask types. furthermore, common components of surgical masks such as cellulose-based materials, are known to degrade vaporous hydrogen peroxide and reduce the efficacy of sterilization [40] . there is also limited data evaluating the effectiveness of any ppe decontamination intervention against sars-cov-2 [38, 41] , although more studies are underway. independent research on surgical masks is therefore critical in order to inform clinicians, infection control experts, and public health administrators on how best to advise safe decontamination and reuse practices. our systematic review has several important strengths. to our knowledge, this is the first systematic review of decontamination interventions in surgical mask ppe and provides important information describing the nature of interventions and outcomes evaluated to date. our review highlights the variability in study methods and outcome reporting. as a result, we identified the following core outcomes to consider when conducting research in this field, to encourage consistent methodology and transparent reporting: mask performance (fe, airflow resistance), decontamination effects (germicidal effects, in vivo infection rates), physical characteristics of decontaminated masks, adverse effects to mask users, and intervention feasibility. we also developed a systematic tool with which to assess risk of bias in this body of literature. our review also has limitations. we were unable to conduct any meta-analyses due to the paucity of studies and their heterogeneous methodologies and outcome assessments. outcomes described this systematic review required summarizing study results from multiple experiments; we rationalized the selective reporting of results in our methods to encourage conservative interpretation of the findings. given the rapidly evolving landscape of ppe literature during the sars-cov-2 pandemic, we plan to update this systematic review at regular intervals for new relevant evidence as it becomes available (i.e. living systematic review) [42] . there is inadequate evidence on the safety or efficacy of any decontamination intervention for extended use or reuse of surgical masks in the clinical setting. further research should therefore be conducted specifically in surgical masks, that include decontamination interventions demonstrating promise in n95 ffrs (e.g. uvgi, vaporized hydrogen peroxide). to ensure the safety of hcps and all end users, the same rigorous standard of research should be applied to surgical masks as with n95 ffrs, given its much broader applications as ppe. we recommend that future studies consider applying core outcomes and test conditions that are in accordance with acceptable industry standards in their design, to enable transparency of reporting and comparisons of efficacy between interventions. 1.6 (+0.3), p<0.05 fe, filtration efficiency; ns, not statistically significant. a fe to testing agent used, expressed as a percentage. a higher percentage filtration efficiency indicates better mask performance. results in study were presented as percentage particle penetration, and converted to filtration efficiency (fe % = 100 -particle penetration) for consistency of reporting in this systematic review. b airflow resistance assessed the "breathability" of the mask at tidal breathing. a lower airflow resistance means better breathability. for disease control and prevention. interim infection prevention and control recommendations for patients with suspected or confirmed coronavirus disease 2019 (covid-19) in healthcare settings world health organization. rational use of personal protective equipment for coronavirus disease ( covid-19) and considerations during severe shortages: interim guidance facemasks for the prevention of infection in healthcare and community settings advice on the use of masks in the context of covid-19: interim guidance potential demand for respirators and surgical masks during a hypothetical influenza pandemic in the united states personal protective equipment supply chain: lessons learned from recent public health emergency responses. health secur hospital preparedness for severe acute respiratory syndrome in the united states: views from a national survey of infectious diseases consultants universal masking in hospitals in the covid-19 era centers for disease control and prevention. strategies for optimizing the supply of facemasks sourcing personal protective equipment during the covid-19 pandemic heat-based decontamination of n95 filtering facepiece respirators (ffr): a systematic review decontaminating n95 masks with ultraviolet germicidal irradiation (uvgi) does not impair mask efficacy and safety: a systematic review efficacy and safety of disinfectants for decontamination of n95 and sn95 filtering facepiece respirators: a systematic review decontamination interventions for the reuse of surgical mask personal protective equipment (ppe): a protocol for a systematic review the prisma statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration tools for assessing risk of reporting biases in studies and syntheses of studies: a systematic review a comparison of facemask and respirator filtration test methods american society for testing and materials (astm) f2100-04. standard specification for performance of materials used in medical face masks validation and application of models to predict facemask influenza contamination in healthcare settings the chemistry and applications of antimicrobial polymers: a state-of-the-art review notice -important regulatory considerations for the reprocessing of single use n95 respirators during the covid-19 response n95 mask decontamination using standard hospital sterilization technologies do n95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks? terminal sterilization of medical devices using vaporized hydrogen peroxide: a review of current methods and emerging opportunities detection limit of assay not reported; log10 reduction factor cannot be calculated. f colony-forming unit reduction percentages reported in study. results converted to log10 reduction factors. g absolute values for lung viral titers reported in study (strain not reported) with post-inoculation incubation of 5log10 reduction in lung viral titer g uncoated: 0.0 (n 0 ) 3 mg/cm 2 : 0.6, p <0.005 11 mg/cm 2 : 1.1, p <0.005 19 mg/cm 2 : 1.3, p <0.005all surviving mice had reduced, but detectable, lung viral titers.bdl, below detection limit; cfu, colony forming units; fe, filtration efficiency; gs5, goldshield 5 quaternary ammonium agent; h1n1 ca/09, h1n1 influenza virus (a/california/04/2009); h1n1 pr/34, h1n1 influenza virus (a/puerto rico/08/2934); h5n1 vn/04, h5n1 influenza virus (a/vietnam/1203/2004); kcl, potassium chloride; n 0 , time zero from which log10 reduction factor was calculated; nacl, sodium chloride; ns, not statistically significant. a fe to testing agent used, expressed as a percentage. a higher percentage filtration efficiency indicates better mask performance. b airflow resistance assessed the "breathability" of the mask at tidal breathing. a lower airflow resistance means better breathability. c study reported pressure drop and flow rate in inches of water and cubic feet per minute per square foot, respectively. results converted to si units. d colony-forming units or plaque-forming units reported in study, as applicable. results converted to log10 reduction factors. key: cord-273565-0en2sl3q authors: scarano, antonio; inchingolo, francesco; lorusso, felice title: facial skin temperature and discomfort when wearing protective face masks: thermal infrared imaging evaluation and hands moving the mask date: 2020-06-27 journal: int j environ res public health doi: 10.3390/ijerph17134624 sha: doc_id: 273565 cord_uid: 0en2sl3q individual respiratory protective devices and face masks represent critical tools in protecting health care workers in hospitals and clinics, and play a central role in decreasing the spread of the high-risk pandemic infection of 2019, coronavirus disease (covid-19). the aim of the present study was to compare the facial skin temperature and the heat flow when wearing medical surgical masks to the same factors when wearing n95 respirators. a total of 20 subjects were recruited and during the evaluation, each subject was invited to wear a surgical mask or respirator for 1 h. the next day in the morning at the same hour, the same subject wore a n95 mask for 1 h with the same protocol. infrared thermal evaluation was performed to measure the facial temperature of the perioral region and the perception ratings related to the humidity, heat, breathing difficulty, and discomfort were recorded. a significant difference in heat flow and perioral region temperature was recorded between the surgical mask and the n95 respirator (p < 0.05). a statistically significant difference in humidity, heat, breathing difficulty, and discomfort was present between the groups. the study results suggest that n95 respirators are able to induce an increased facial skin temperature, greater discomfort and lower wearing adherence when compared to the medical surgical masks. coronavirus disease is an infectious mild to moderate respiratory illness caused by a newly discovered coronavirus [1, 2] . this infection is a serious disease in patients with other pathologies, especially in older people with underlying medical problems such as chronic respiratory disease, cancer, cardiovascular disease, and diabetes. these patients develop serious acute pneumonia with a high mortality rate [3] . a primary way in which the virus spreads is through droplets of saliva, produced during coughs or sneezes or through discharge from the nose from an infected person. airborne bacteria or viruses can spread infectious diseases, which can become major public health concerns. in particular, tuberculosis (tb) and influenza are major problems in clinical practice [4] . these diseases can be a hazard which can infect care workers. for this reason, it is important to implement airborne infection control by using a good prevention strategy in health-care sites. in fact, the exhaled air of infected humans is one of the prime sources of ambient contamination by bacteria or contagious viruses. droplets are also particularly dangerous for possible transmission when there is a virus, such as influenza, in high concentrations of airborne particles in closed or small environments [5] . in case of a pandemic involving an airborne-transmissible agent, doctors must use a mask for protection. it is important to evaluate the flow of air through the respirator to understand if there are any points of concern for the health of the doctors. however, the use of protective face masks (pfms) will not be effective if masks are not used appropriately. due to resistance to airflow and discomfort related to buildup of facial heat, especially in hot and humid weather, many people use a pfm with lack of compliance to safety regulations [6, 7] . the direct surgical mask has a low/moderate filter performance with lower levels of airflow resistance, while the high heat and humidity under a pfm can cause moisture to condense on the outer surface of the pfm, which consequently impairs respiratory heat loss and imposes an increased heat burden [8] . the factors that reduce the discomfort of heat on the face are nasal breathing, use of exhalation valves, reduction of pfm dead space parameters, and cup-shaped or duckbill designs. it has been suggested that facial temperature augmentation can trigger a panic disorder caused by elevated co 2 levels under the pfm, with hot flashes and sweating. in fact, wearing a surgical mask or respirator produces a significant increase in skin temperature, especially under the mask. for some subjects in a workplace, this could be sufficient to cause thermal discomfort. a pfm induces a significant augmentation of facial skin effects on thermoregulation. for this reason, many people use an pfm incorrectly, without covering the nose, or, after a few minutes, this can lead to partial uncovering of the nasal area. impatience with the thermal effects of pfm leads to discomfort and can induce a decreased use and concomitant decreased protection for the user. the purpose of the present study was to evaluate facial skin temperature, discomfort and hands moving the mask when wearing surgical masks or n95 respirators, with thermal infrared imaging. during the study period, february 2020, 20 voluntary male workers met the inclusion criteria with a mean age of 50 (45-55) in the department of oral surgery of the university of chieti-pescara, italy. the study was conducted in observance of the helsinki declaration (revised version of tokyo in 2004) and good clinical practice guidelines. all patients gave informed consent to the adopted noninvasive procedure. the inclusion criteria were experience in using respirators and absence of respiratory diseases. the volunteers were all in phototypes ii or iii of the fitzpatrick scale [9] for the facial areas being evaluated. the exclusion criteria were allergic rhinitis and nasal septum deviations, showing facial aging, lax skin, facial treatment antiaging, severe illness, facial skin disease, head and neck radiation therapy, chemotherapy, facial skin resurfacing, and uncontrolled diabetes. all volunteers had all previously experienced using respirators. in the previous hours, they had not undergone athletic training. after a thorough preliminary examination, the volunteers underwent facial temperature evaluation, having been extensively informed about the study procedures. the volunteers were requested to enter a room with a constant temperature for 1 h before the study to allow them to acclimatize. this study was undertaken to investigate the effects of wearing a pfm on facial skin temperature when the subject was not actively working. the perception ratings related to the humidity, heat, breathing difficulty, and overall discomfort of the enrolled subjects were recorded. discomfort was scored by means of a 100-mm scale from 0 (no discomfort) to 100 (worst discomfort imaginable). the infrared thermography evaluation was performed in a climate-controlled environment (temperature: 22-24 • c, relative humidity percentage: 50 ± 5%, without any direct ventilation into the mouths of the subjects). the environmental humidity was measured by a built-in integrated sensor (atmo-tube, san francisco, ca, usa). the sensor provided a measurement of relative humidity (rh) at regular intervals with a resolution of 0.5% and a humidity range from 0% to 100%. the facial temperature of the perioral region was recorded by a 14-bit digital infrared camera (flir sc660 qwip, flir systems, danderyd, sweden). the general acquisition parameters were set with the following specifications: 320 × 240 pixels focal plane array; 8-9 µm spectral range; 0.02 k noise equivalent temperature differences (netds); 50-hz sampling rate; optics: germanium lens; f 20; and f/1.5. the camera was positioned at 0.50 m away from the facial region to obtain the maximum spatial resolution. the thermographic images were recorded at a rate of 10 images per second, and consequently re-aligned by the use of an edge-detection based method implemented with an in-house software package. a thermal video was recorded, and the photos were developed via dedicated software. temperature changes in the perioral and facial areas were elaborated on the realigned thermal images. the complete act of breathing was recorded by a thermal video, and the temperature changes were calculated by the dedicated software using frame-by-frame records. the average temperature for inhalation and expiration acts were considered for the statistical evaluation. for the thermal evaluations, we considered the emissivity of 0.98 for skin, 0.93 for surgical mask and n95 (any color). the emissivity value is the same for both surgical and n95 because both surfaces are roughened and have the same thermal characteristics. thermographic data measurements were performed by the software package flir quickreport v.1.2 (flir systems inc., north billerica, ma, usa), which is able to obtain the maximum, minimum, and average temperature of a perioral region. during the evaluation, the subject was invited to wear a surgical mask or respirator for 1 h and read the newspaper, mainly in silence, speaking aloud for only 10 min. in the first experiment, the volunteer wore a filter type respirator for 1 h. the next day in the morning at the same time of day, the subject wore a n95 mask for 1 h with the same protocol. as a result, there were two variables, no respirator versus respirator, and before and after wearing two different pfm. skin temperature was recorded before wearing the surgical mask or respirator, during 1 h of wearing, and immediately after having removed the pfm, a video record was taken for another 10 min. therefore, during protective mask wearing, was a thermal video recorded for 1 h resulted in 10 by 60 by 60 = 36,000 images per investigated subject. a power analysis was performed using clinical software to determine the number of samples needed to achieve statistical significance for quantitative analysis of facial temperature. a calculation model was adopted for dichotomous variables (yes/no effect) using the incidence effect designed to discern the reasons (85% for the test group and 10% for the control group), with alpha = 0.05 and power = 95%. the optimal number of samples for analysis was 20 patients per group. numerical results are presented as the ±sd means of all the experiments. the data outcome was collected and statistically evaluated by the software package graphpad 6 (prism, san diego, ca, usa). the normal distribution of the study data was evaluated by the shapiro-wilks test to evaluate the normal distribution. the t-student test was performed to compare the study variables means in each group. the level of significance was set at p < 0.05. the videos were converted to infrared images of the facial temperature distribution when wearing the different facemask types. during expiration, the temperature change induced by the airflow appeared in the central area of the mask, while no temperature changes were detected laterally, at the top, or at the bottom of the mask. the superficial area of the surgical mask showed a homogeneous distribution of the heat flow detected by ir during breathing. the n95 respirator group detected a non-homogeneous flow on the mask. the ir images of facial skin temperature distributions were taken during wearing of the mask, immediately after removal of the mask, and 10 min after removal of the mask. the ir thermography images demonstrated significant temperature changes at the perioral region and superior lip immediately after removal of the mask, compared with baseline conditions in both types of pfm. no statistical differences were detected in other regions of the face. differences were detected in the mask-skin contact sites after removal of the mask, compared with baseline conditions (figures 1 and 2) . the temperature of the upper lip recovered almost to baseline readings approximately 10 min after mask removal. no temperature augmentations were observed in the forehead, cheeks, and nose/mouth regions. the surgical mask surface showed large temperature changes during inhalation and exhalation (t inhalation: 28.9 ± 3.1 °c; t exhalation: 31.4 ± 3.6 °c). the n95 respirator surface showed significantly fewer temperature fluctuations during the breathing acts (t inhalation: 26.0 ± 3.6 °c; t exhalation: 29.3 ± 3.8 °c). after the protection device removal, a significant difference in perioral facial temperature was detected (p < 0.05), between the the temperature of the upper lip recovered almost to baseline readings approximately 10 min after mask removal. no temperature augmentations were observed in the forehead, cheeks, and nose/mouth regions. the surgical mask surface showed large temperature changes during inhalation and exhalation (t inhalation: 28.9 ± 3.1 °c; t exhalation: 31.4 ± 3.6 °c). the n95 respirator surface showed significantly fewer temperature fluctuations during the breathing acts (t inhalation: 26.0 ± 3.6 °c; t exhalation: 29.3 ± 3.8 °c). after the protection device removal, a significant difference in perioral facial temperature was detected (p < 0.05), between the the temperature of the upper lip recovered almost to baseline readings approximately 10 min after mask removal. no temperature augmentations were observed in the forehead, cheeks, and nose/mouth regions. the surgical mask surface showed large temperature changes during inhalation and exhalation (t inhalation: 28.9 ± 3.1 • c; t exhalation: 31.4 ± 3.6 • c). the n95 respirator surface showed significantly fewer temperature fluctuations during the breathing acts (t inhalation: 26.0 ± 3.6 • c; t exhalation: 29.3 ± 3.8 • c). after the protection device removal, a significant difference in perioral facial temperature was detected (p < 0.05), between the surgical mask (mean t removal: 35.9 ± 3.4 • c; ∆t: 0.7 ± 0.5 • c) and the n95 (mean t removal: 36.9 ± 4.2 • c; ∆t: 1.2 ± 0.5 • c) (tables 1 and 2). a statistical difference in discomfort was observed (p < 0.01). additionally, statistical differences were observed regarding the number of touches to the facial mask or face during the 1 h (p < 0.05). subjects wearing the n95 touched it 25 times to move it, while those wearing the surgical mask performed this gesture 8 times. this underscores the discomfort that a facial mask with a major airflow resistance causes (table 3) . table 3 . infrared thermal measurements of the perioral region surface. temperature differences between baseline and inhalation, between inhalation and exhalation and between baseline and mask removal. (mean, sd. student's t-test). ∆t b-rem : temperature difference between baseline and inhalation; ∆t in-ex : temperature difference between inhalation and exhalation; ∆t in-ex : temperature difference between baseline and mask removal. the outcomes of the present study indicate that fitting a surgical mask or respirator during 1 h of continuous wearing led to an increase in facial skin temperature under the face mask, while removing the face mask tended to rapidly decrease it after 1 min, returning to the baseline after 5 min. a face mask prevents transpiration and protects against airborne transmitted bacteria or viruses and it is very important to wear one in a health care situation, especially during a pandemic [10, 11] . this may increase skin temperature irrespective of workload. the increases we observed under the mask were between 0.7 ± 3.3 • c and 1.9 ± 3.5 • c in the respirator. these were lower when the volunteers wore surgical masks. for both types (surgical masks and n95 respirators), increased skin temperature was observed at >34.5 • c, a level which may induce slight sensations of thermal discomfort. on this basis, the larger rise in lip temperature seen in these subjects could possibly be a result of increased airflow resistance to both pfms. the study size of 20 subjects is sufficient for basic technical hypotheses but is insufficient for the evaluation of other multifactorial effects. for example, we only enrolled healthy subjects. pulmonary, cardiac, and metabolic pathologies could greatly influence the results of this study. in the present study, we used thermal infrared imaging because this technique is extensively used for evaluating the superficial temperature of bone [12] , facial skin [13] , and oral mucosae [14] . the increased perioral temperature observed in our study could be explained by the fact that wearing a face mask for a certain period of time causes reduction in heat loss from the body by evaporation, conduction, convection, and radiation [15] . a pfm avoids normal transpiration and cooling of the skin, and the space beneath it (dead space) is filled with warm, moist expired air during most of the breathing cycle. additionally, surgical masks may increase airway resistance, and a statistically significant decrease in the blood o2 saturation level of surgeons has been found; however, these data were not confirmed by this new study [16] . in this study, we evaluated the effect of facial masks used for 1 h; however, in many situations, masks are worn for longer periods of time. therefore, a greater effect on the general discomfort of the wearer is conceivable. another interesting study has demonstrated an increase in oral temperature when someone is wearing a face mask for a sufficient time, and this condition can influence a wrong diagnosis of fever [16] . in this study, the authors discovered that the subjects wearing and not wearing masks had intraoral temperature above 37.5 and 37.3 • c, respectively, and when the n95 mask was worn the intraoral temperature was statistically significantly different than when wearing the surgical mask. the face is extremely important for thermoregulation of the body; it is two to five times more effective at suppressing sweating and thermal discomfort than the cooling effect of a similar dermal area elsewhere on the body. in fact, the face accounts for 20% of the total drive from the skin and has a high concentration of thermoreceptors [17] [18] [19] . the facial region and head form an area that is a critical structure for cooling, because is the most sensitive to temperature sensation, whereas temperature sensing is poor on the extremities, with the exception of the fingers, and intermediate in other regions [20, 21] . in moderate environmental conditions, such as other areas of bare skin, the surface temperature is about 2-4 • c lower than the internal temperature [22] , while temperature gradients from the core to the skin in defined regions, such as fingers or toes, are of 7.0 or even 9 • c, which is not uncommon in healthy people. perioral and nasolabial region skin temperature in an adult can be around 35.3 ± 1.4 or 35.2 ± 1.3 • c [23] . body temperature is maintained constant through a combination of physiological mechanisms. in the perioral and nasal region, the pfm that covers the mouth and nose impedes the greater cooling impact of facial skin temperature [24] . moreover, the straps and head harness of a tight-fitting mask can reduce the venous flow from the head. many studies have reported that pfms increase the skin temperature of the lips by 1.9 • c after 15 min without any effect on other regions of the face and little effect on core temperature, and this may have a significant impact on the perception of thermal discomfort [25] . the increase in facial skin temperature induced by pfms has been documented in different studies, and this significantly influences thermal sensations of the whole body, because cutaneous thermal receptor impulses from the face to the central nervous system are more important than from other regions. the face is the most sensitive region, while the lower extremities (i.e., thigh, calf, sole, and toe) are the least, and it has higher sensitivity to warm temperature and could influence maintaining thermal homeostasis. in fact, when the face of a healthy individual was exposed to heating, local sweating on the leg was augmented three times more than when heating was applied on the leg [17, 26] . in this study, we found that the surgical mask produces a slight facial skin temperature augmentation, with more comfort during, and thus increased adherence to, correct use. for this reason, it is better to wear a surgical mask correctly than an n95 which, due to the discomfort, causes displacements with the hands and temporary withdrawals of the mask from the face. a high number of removals of respirators from the face was recorded in the present study, and thermal discomfort may contribute to this. this result should be added to the results obtained by investigators who have shown that wearing a n95 surgical mask does not reduce the risk of infection. in fact, n95 respirators vs. surgical masks as worn by outpatient health care personnel showed no significant difference in the incidence of laboratory-confirmed influenza [11] . the effectiveness of medical masks is not inferior to that of n95 respirators and surgical masks provide similar protection to that of n95 respirators, because respiratory viruses are primarily transmitted by large droplets. n95 respirators are structured to filter against inhaling small airborne particles and fit tightly to the face, while surgical masks are structured against big airborne particles with a loose fit to the face with minor resistance to airflow. n95 respirators appeared to have a larger protective effect than surgical masks, but a recent meta-analysis demonstrated that there were insufficient data to established definitively whether n95 respirators are superior to surgical masks in protecting workers against transmissible acute respiratory infections in clinical settings [27] . in fact, the scientific evidence that n95 respirators are superior to surgical masks is sparse, and findings are insufficient within and across studies [28] . in light of the results reported by our research, a surgical mask presents better adherence and it is better to wear one correctly than an n95, as many studies suggest that the major obstacle against respiratory infections is not the type of pfm worn but the rate of adherence, with a range varying from 10% to 84% [6, 7, 29] . another important consideration is the high frequency of touching the n95 observed, which increases self-infection of microorganisms. in fact, contaminated hands are a route to disseminating respiratory infections [30] . the wearing of n95 while not working over the course of 1 h has a significant impact on facial skin temperature, discomfort, and hands moving the mask, which compromises safety and suggests that in working conditions, there is an increase in these parameters. a limitation of the present study was that all subjects were non-working males and that males present a higher skin temperature than females [31] , and we did not investigate the difference between the two sexes; however, none of the volunteers were affected by nasal or respiratory diseases. this study was conducted during the italian lockdown, and in our department, there were only male patients. another limitation of this study is that all subjects were wearing the filter on day 1 and the n95 mask on day 2, and we did not randomize order across the subjects to reduce systematic errors. we hypothesize that nasal and respiratory diseases or working increase discomfort during wearing and use of the pfm. in conclusion, the n95 mask produces a major increase in skin facial temperature with major discomfort, and volunteers have shown greater adherence in the use of the surgical mask rather than n95. pathogenicity and transmissibility of 2019-ncov-a quick overview and comparison with other emerging viruses a novel coronavirus from patients with pneumonia in china lancet infectious diseases commission preparedness for emerging epidemic threats: a lancet infectious diseases commission transmission routes of 2019-ncov and controls in dental practice consistent detection of 2019 novel coronavirus in saliva a cluster randomized clinical trial comparing fit-tested and non-fit-tested n95 respirators to medical masks to prevent respiratory virus infection in health care workers. influenza other respir a randomized clinical trial of three options for n95 respirators and medical masks in health workers effects of wearing n95 and surgical facemasks on heart rate, thermal stress and subjective sensations the validity and practicality of sun-reactive skin types i through vi the efficacy of medical masks and respirators against respiratory infection in healthcare workers. influenza other respir n95 respirators vs medical masks for preventing influenza among health care personnel: a randomized clinical trial the effects of liquid disinfection and heat sterilization processes on implant drill roughness: energy dispersion x-ray microanalysis and infrared thermography lateral sinus floor elevation performed with trapezoidal and modified triangular flap designs: a randomized pilot study of post-operative pain using thermal infrared imaging eradication of hairy mouth after oncological resection of the tongue and floor mouth using a diode laser 808 nm. postoperative pain assessment using thermal infrared imaging human local and total heat losses in different temperature the effect of wearing a face mask on body temperature differential thermal sensitivity in the human skin temperature sensitivity of the body surface over the life span relative importance of different surface regions for thermal comfort in humans effect of local cooling on sweating rate and cold sensation. pflügers arch regional sensitivity and spatial summation in the warmth sense estimation of mean body temperature from mean skin and core temperature biophysical parameters of skin: map of human face, regional, and age-related differences development of a draft british standard: the assessment of heat strain for workers wearing personal protective equipment the effect on heart rate and facial skin temperature of wearing respiratory protection at work the distribution of cutaneous sudomotor and alliesthesial thermosensitivity in mildly heat-stressed humans: an open-loop approach effectiveness of n95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis effectiveness of masks and respirators against respiratory infections in healthcare workers: a systematic review and meta-analysis time dependent infrared thermographic evaluation of facemasks preventive behaviors and mental distress in response to h1n1 among university students in guangzhou, china thermographic imaging of facial skin-gender differences and temperature changes over time in healthy subjects this article is an open access article distributed under the terms and conditions of the creative commons attribution (cc by) license the authors declare no acknowledgment for the present investigation. the authors declare no conflict of interest. key: cord-258859-iaiosjlu authors: wang, jiao; pan, lijun; tang, song; ji, john s.; shi, xiaoming title: mask use during covid-19: a risk adjusted strategy() date: 2020-06-25 journal: environ pollut doi: 10.1016/j.envpol.2020.115099 sha: doc_id: 258859 cord_uid: iaiosjlu in the context of coronavirus disease (2019) (covid-19) cases globally, there is a lack of consensus across cultures on whether wearing face masks is an effective physical intervention against disease transmission. this study 1) illustrates transmission routes of severe acute respiratory syndrome coronavirus 2 (sars-cov-2); 2) addresses controversies surrounding the mask from perspectives of attitude, effectiveness, and necessity of wearing the mask with evidence that the use of mask would effectively interrupt the transmission of infectious diseases in both hospital settings and community settings; and 3) provides suggestion that the public should wear the mask during covid-19 pandemic according to local context. to achieve this goal, government should establish a risk adjusted strategy of mask use to scientifically publicize the use of masks, guarantee sufficient supply of masks, and cooperate for reducing health resources inequities. globally, countries have utilized precautionary measures against this pandemic. however, 30 there is a lack of consensus across cultures on whether wearing face masks is an effective 31 physical intervention against disease transmission. this study aims to illustrate 32 transmission routes of severe acute respiratory syndrome coronavirus 2 (sars-cov-33 2), address the controversies surrounding mask wearing, and provides suggestions for the 34 use of facial masks during the covid-19 pandemic. 35 the references search was conducted on march 11, using three databases (pubmed, 36 cnki, and web of science) with the search terms "covid-19", "2019-ncov", "novel 37 coronavirus", or "sars-cov-2" and "mask", "facial mask", or "face mask". the team 38 members individually assessed the relevance and validity of each study. non-peer 39 reviewed manuscripts from preprint servers were not considered. we also searched the another important feature of the covid-19 is that asymptomatic cases proportion 86 is high. it is estimated approximately 60% of all infections convert from cases with mild 87 symptom or asymptotic cases and might be passing the virus on to others (qiu, 2020 however, global spread of sars-cov-2 is far greater than mers and sars, which 107 might be associated with cases with mild symptom or asymptomatic cases. according to 108 wrapp et al., the binding of sars-cov-2 to the obligate receptor of angiotensin 109 converting enzyme 2 (ace2) is of higher affinity than that of sars-cov (wrapp et al., 110 2020) , indicating that those with medical comorbidities may be at higher risks. this may 111 also indicate a higher time to infection, even in the absence of masks (pung et al., 2020) . avian influenza, influenza, and haze events. hence, wearing masks has become a 154 pervasive in society as a way to prevent exposure. this is for good reason, as the 155 population density in asian countries is generally higher than that in western countries, 156 and the crowding in a confined place will increase the infection risk or exposure. 157 therefore, during the covid-19 pandemic, the public is encouraged to wear masks in 158 public places and people often comply as a form of health-seeking behavior (greenhalgh 159 et al., 2020) . 160 however, in many western advanced economies, those wearing masks are often met 161 with suspicion in public, even causing panic in certain situation. universal mask use in 162 the community has been discouraged by some health authorities with the argument that 163 masks provide no effective protection against coronavirus infection (feng et al., 2020) . effectiveness studies is mainly due to different study contents, study designs, evaluation 177 methods and endpoints. understandably, good evidence on this topic is difficult to assess. 178 many studies used self-reported questionnaire to quantify mask uptake status, which may 179 introduce subjective bias because the description depends on perception of participants 180 suppose if only symptomatic cases wore masks, we would miss those asymptomatic 261 cases, which increases the possibility of spreading the virus before realization that they 262 carry the virus. however, we should note that requiring the general public to wear masks 263 would put high pressure on mask supply, and insufficient guidance would even trigger a 264 run on medical protection products creating a lack of ppe for medical professionals. 265 therefore, scientific strategy and strategic guidance should be established, and enough 266 mask supply should be guaranteed under the frame of inter-or intra-national cooperation. 267 268 as tedros adhanom ghebreyesus, the who director-general, mentioned on 270 march 18, 2020, "do not assume you will not be infected, prepare as if you will die" 271 (ghebreyesus, 2020) . the government of china has implemented a risk-based mask use 272 strategy for general public, people in public congregated places and confined congregated 273 places, confirmed/suspected cases and close contacts, and occupational exposed workers 274 under various scenarios, which could be used as a reference ( table 1) . as an example, 275 during the covid-19 pandemic, it is suggested to wear the mask in congregated places 276 such as offices, shopping malls, restaurants, conference room, etc. or relatively confined 277 environments such as elevators, transportation vehicles, etc. the mask is generally used 278 by general public, while the respirator or a filtering face piece, which is designed to 279 protect the wearer from exposure to airborne contaminants, is mainly used by health care 280 workers especially during agp (european centre for disease prevention and control, 281 2020). the exhalation valve is sometime used in the respirator in order to reduce the 282 breathing resistance. however, the inhalation valve closes and the exhalation valve opens 283 of the mask when the wearer breathing, implying that the exhaled gas is not filtered and 284 directly discharged into the surrounding environment. as a result, the respirator 285 recommended for suspected cases, confirmed cases, asymptomatic carriers, and close 286 contacts must not contain the valve (cdc, 2020c). moreover, considering the probable 287 insufficient mask production, masks could be repeatedly used under the prerequisite of 288 public health protection in areas with middle to low risks. 289 there is not a single measure that could provide complete protection to the public. 300 therefore, mask use must be combined with hand hygiene, ventilation improvement, 301 reduction of gatherings, and social and physical distancing. to inform the public, the 302 government could 1) invite mainstream press such as tv stations, broadcasts, 303 newspapers, etc. to participate in mask education; 2) spread relevant knowledge via social 304 media (e.g. twitter, facebook, and instagram) or display screens and billboards in public 305 places; 3) hand out mask instruction materials to the public; and 4) carry out training and 306 seminars in places such as hospitals, schools, kindergartens. 307 308 as the use of masks during the covid-19 pandemic would contribute to the rapid 310 consumption of masks in limited time, two essential countermeasures should be taken 311 into consideration. the government should timely stimulate mask production. many 312 countries have been facing a severe shortage of medical resources, including medical 313 masks. in this circumstance, the mask price increased sharply, and the public stole or 314 fought for masks in some regions; in addition, diplomatic disputes even arose. to solve 315 this problem, the government could 1) procure surgical masks globally through different 316 channels and means; 2) distribute masks in accordance with risk level; and 3) explore 317 prospects of local production. research on mask reuse should also be encouraged. for 318 example, song et al. has proposed an approach for medical mask use using hairdryer, and 319 they are still working on further improvement . after the treatment, the 320 medical mask could be used by the public, but the reuse in a hospital settings is still 321 unexplored. 322 323 the face mask distribution priority should be given to healthcare workers providing 326 care services (e.g. front-line healthcare workers, nursing staff in institutions, and 327 healthcare personnel in private clinics); personnel who provide essential services and 328 who are required to have contact with the public at work (e.g. those providing public 329 transport, emergency services and immigration services); and vulnerable groups in the 330 society (e.g. unaccompanied children, elderly people without family support, and 331 disabled persons). 332 the globe is more interconnected than ever; if the countries with weaker health 333 systems fail to control the pandemic, other countries would be re-exposed by the covid-334 19 for the foreseeable future. if the countries with weak health systems fail to control the 335 pandemic, other countries would be exposed in the danger of being harassed by the 336 covid-19 for the long term. as chief of u.n. claimed, "we must create the conditions 337 and mobilize the resources necessary to ensure that developing countries have equal 338 opportunities to respond to this crisis in their communities and economies" (united 339 nations secretary-general, 2020). in mid-february, france took early action to help 340 china, sending 17 tons of similar supplies. under the well control of covid-19, china 341 has sent supplies to italy, the hardest hit among european countries, and to spain (us 342 news, 2020a). case in point, lvmh, the world's biggest luxury goods group, has also 343 ordered 40 million health masks from a chinese supplier to help france coping with this 344 pandemic (us news, 2020b). it could be seen that international cooperation, with 345 manufacturing and distribution logistics may optimize mask resource allocation. 346 in each country, the most vulnerable group should be paid more attention when in the context of rapid spread of covid-19 globally, there is a lack of consensus on 361 the mask use as a npi amide the pandemic. this study summarized that: 1) main 362 transmission routes of sars-cov-2 include droplet, contact transmissions, and possible 363 airborne transmissions, which is characterized by high proportion of cases with mild 364 symptom or asymptomatic cases, strong infectivity, and a large number of clusters; 2) 365 the necessity of wearing masks by the public during covid-19 pandemic has been 366 under-emphasized; and 3) a risk basis mask use strategies and compliance improvement 367 are suggested. 368 369 jw and xs had the idea for and designed the study. jw and lp drafted the paper, and all 371 authors critically revised the manuscript for important content and gave final approval for 372 the version to be published. all authors agree to be accountable for all aspects of the 373 work in ensuring that questions related to any part of the work are appropriately 374 investigated and resolved. jw and lp contributed equally to this work. 375 we declare no competing interests. 377 the authors would like to acknowledge all health-care workers involved in the diagnosis 379 and treatment of patients during the pandemic in the globe. the present perspective has 380 not been subjected to the peer and policy review from china cdc, and therefore does not 381 necessarily reflect the views of the china cdc and no official endorsement should be 382 mask use, hand hygiene, and seasonal 387 influenza-like illness among young adults: a randomized intervention trial analyzing the 390 mers disease control strategy through an optimal control problem uptake and effectiveness of facemask against respiratory infections at 394 mass gatherings: a systematic review medical face masks -requirements and test methods. 397 bureau of disease control and prevention, 2020. scientific guidelines for the wearing of 398 masks by the public covid-19): steps to prevent illness. 400 cdc, 2020b. how to protect yourself & others personal protective equipment: questions and answers the epidemiological characteristics of infection in close contacts of covid-19 in 404 ningbo city modeling influenza epidemics and 406 pandemics: insights into the future of swine flu (h1n1) examination of sars coronavirus in air and air conditioner 409 samples mass gathering-related mask use during 411 2009 pandemic influenza a (h1n1) and middle east respiratory syndrome coronavirus european centre for disease prevention and control rational use of face 416 masks in the covid-19 pandemic. the lancet respiratory medicine who director-general's opening remarks at the media briefing 418 on covid the great lockdown: worst economic downturn since the great 420 depression face masks 422 for the public during the covid-19 crisis physical interventions to 425 interrupt or reduce the spread of respiratory viruses: systematic review physical 429 interventions to interrupt or reduce the spread of respiratory viruses a man was infected by contacting with a confirmed patient for 15 432 seconds without a mask sars transmission, risk factors, and 434 prevention in hong kong substantial 436 undocumented infection facilitates the rapid dissemination of novel coronavirus aerodynamic 439 characteristics and rna concentration of sars-cov-2 aerosol in wuhan hospitals 440 during covid-19 outbreak. biorxiv an epidemiological investigation of 2019 novel 443 coronavirus disease through aerosol-borne transmission by public transport face mask use and control of respiratory virus 447 transmission in households facemasks for the prevention of infection in 449 healthcare and community settings estimating the 452 asymptomatic proportion of coronavirus disease 2019 (covid-19) cases on board the 453 diamond princess cruise ship 455 effectiveness of hand hygiene practices in preventing influenza virus infection in the 456 community setting: a systematic review public health responses to covid-19 outbreaks on cruise ships -460 air, surface environmental, and personal protective equipment contamination 464 by severe acute respiratory syndrome coronavirus 2 (sars-cov-2) from a 465 symptomatic patient predicting support for 467 non-pharmaceutical interventions during infectious outbreaks: a four region analysis 478 investigation of three clusters of covid-19 in singapore: implications for surveillance 479 and response measures covert coronavirus infections could be seeding new outbreaks transmission of 2019-484 ncov infection from an asymptomatic contact in germany evaluation of heat inactivation of virus 487 contamination on medical mask technical specification of daily protective 489 mask note to correspondents: letter from the 491 secretary-general to g-20 members the latest: china sends masks, medical supplies to france. 493 us news, 2020b. lvmh orders 40 million masks from china for france aerosol and surface stability of sars-cov-2 as 497 compared with sars-cov-1 hand hygiene and risk of influenza virus 499 infections in the community: a systematic review and meta-analysis consensus document on the epidemiology of severe 502 acuterespiratory syndrome (sars). department of communicable diseasesurveillance 503 and response ten things you need to know about pandemic 505 influenza (update of 14 world health organization, 2020a. advice on the use of masks in the context of covid-507 19: interim guidance world health organization, 2020b. coronavirus disease (covid-19) situation report -509 142 world health organization, 2020c. modes of transmission of virus causing covid-19: 511 implications for ipc precaution recommendations nonpharmaceutical interventions for 513 pandemic influenza, national and community measures cryo-em structure of the 2019-ncov spike in the prefusion 517 conformation nowcasting and forecasting the potential 519 domestic and international spread of the 2019-ncov outbreak originating in wuhan, 520 china: a modelling study 523 investigation and analysis on characteristics of a cluster of covid-19 associated with 524 exposure in a department store in tianjin comparison of different samples for 527 2019 novel coronavirus detection by nucleic acid amplification tests a large amount of sars-cov-2 was detected by china cdc in 530 huanan seafood market in wuhan mers, sars and other coronaviruses as causes of 532 pneumonia fecal specimen diagnosis 2019 novel coronavirus 534 infected pneumonia protection by face masks against influenza a(h1n1)pdm09 virus 538 on trans-pacific passenger aircraft estimation of the 540 reproductive number of novel coronavirus (covid-19) and the probable outbreak size 541 on the diamond princess cruise ship: a data-driven analysis â�¢ the mask is an effective non-pharmaceutical intervention of covid-19â�¢ the necessity of wearing masks by the public during covid-19 is under â�� the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.â��the authors declare the following financial interests/personal relationships which may be considered as potential competing interests: key: cord-284484-oak1lfmi authors: barratt, ruth; gilbert, gwendolyn l.; shaban, ramon z.; wyer, mary; hor, su-yin title: enablers of, and barriers to, optimal glove and mask use for routine care in the emergency department: an ethnographic study of australian clinicians date: 2019-12-04 journal: australas emerg care doi: 10.1016/j.auec.2019.10.002 sha: doc_id: 284484 cord_uid: oak1lfmi background: the risk of healthcare-acquired infection increases during outbreaks of novel infectious diseases. emergency department (ed) clinicians are at high risk of exposure to both these and common communicable diseases. personal protective equipment (ppe) is recommended to protect clinicians from acquiring, or becoming vectors of, infection, yet compliance is typically sub-optimal. little is known about factors that influence use of ppe—specifically gloves and masks—during routine care in the ed. methods: this was an ethnographic study, incorporating documentation review, field observations and interviews. the theoretical domains framework (tdf) was used to aid thematic analysis and identify relevant enablers of and barriers to optimal ppe use. results: thirty-one behavioural themes were identified that influenced participants’ use of masks and gloves. there were significant differences, namely: more reported enablers of glove use vs more barriers to mask use. reasons included more positive unit culture towards glove use, and lower perception of risk via facial contamination. conclusion: emerging infectious diseases, spread (among other routes) by respiratory droplets, have caused global outbreaks. emergency clinicians should ensure that, as with gloves, the use of masks is incorporated into routine cares where appropriate. further research which examines items of ppe independently is warranted. healthcare-associated infections are an ongoing threat to patients and clinicians, resulting in significant morbidity and economic cost [1] . the risk of infection, for vulnerable hospital patients, their family members and healthcare professionals, increases during outbreaks of novel and re-emerging infectious diseases, such as the highest-risk healthcare professionals for exposure to bloodborne viral infections [8] and respiratory diseases such as influenza [9] . hunter et al. [10] reported an estimated 16% rate of mers among ed clinicians in abu dhabi and, of those infected, 93% had been exposed before the diagnosis was made. personal protective equipment (ppe), including gowns, gloves, masks and protective eyewear, is crucial for protecting clinicians from acquiring, or acting as a vector of infection to other staff and patients [11] . in addition to appropriate use of ppe, as part of transmission-based precautions (contact, droplet or airborne), standard precautions indicate use of ppe when there is a risk of exposure to pathogens: non-sterile disposable gloves if hands are likely to become contaminated and a surgical mask and eye protection when at risk of exposure to aerosols or direct splash with blood and body fluids. n95/p2 masks are usually reserved for a few diseases (chickenpox, measles, tuberculosis) in which pathogencontaminated droplet nuclei (residue from evaporated droplets) or dust particles can remain suspended in air for long periods and enter the upper and lower respiratory tracts. sub-optimal use of ppe (i.e. contrary to the indications for standard and transmission-based precautions) by clinicians has been reported in different hospital settings [12] [13] [14] . while gloves are the most frequently used item, masks are less appropriately used [15] . although clinicians' use of ppe has been shown to increase when an outbreak is declared [3, [16] [17] [18] , routine compliance is typically suboptimal [19, 20] which increases the risk of occupationally-acquired infection and disease. there is limited recent literature examining the use of ppe in eds. following the introduction of universal precautions in the early 1990s [21] , a number of studies reported poor compliance with these measures in the ed [22] [23] [24] . more recently, singh et al. used self-administered questionnaires to determine compliance with (what are now referred to as) standard precautions in the ed, and found that gloves were frequently used, but there was poor compliance with other ppe, especially eye protection [15] . evanoff et al. [25] observed video footage to assess compliance with ppe during 304 invasive procedures in an ed and reported 96% glove use for trauma patient encounters, compared with 68% and 78%, for use of mask and protective eyewear, respectively. in a trauma centre study, the compliance rates for use of masks and eye protection, after an educational intervention, were 16% and 44%, respectively [26] . ed clinicians are regularly at risk of facial contamination during invasive procedures, intubation and other resuscitative measures [27] . they are also exposed to both seasonal and emerging respiratory infectious diseases. in one paediatric ed setting, only 1-12% of clinicians reported that they always or usually wore a mask or eye protection, while assessing febrile respiratory patients during winter [28] . although gloves are worn frequently, patient safety may be compromised by misuse, such as not changing them between dirty and clean tasks on the same patient or between different patients and/or failing to comply with hand hygiene before and after use, which often contaminates the clinician's hands [29] [30] [31] . commonly cited factors contributing to sub-optimal compliance with ppe in healthcare include inadequate knowledge and training, perception of risk, organisational culture and environmental barriers [32, 33] . reid et al. [28] identified knowledge, access to ppe, patient diagnosis and unit culture, in the ed context, as factors influencing ppe compliance. healthcare transmission of novel infectious diseases can occur prior to recognition of an outbreak [10] . while it is difficult to plan in advance for such a rare event, staff who are competent in the principles and practice of routine infection prevention and control (ipc) and ppe use are more likely to be better protected from the start and more prepared to implement high-level precautions rapidly and safely. in this area there is a paucity of literature which examines factors that facilitate or hinder the use of ppe during routine clini-cal care in the ed. most previous studies have focused primarily on compliance with standard precautions during procedures that pose a high risk of exposure to blood and body fluids [25, 26] or on overall compliance with ppe use, without elucidating determinants of those behaviours [15] . they have described 'how' clinicians use ppe, whereas the present study aimed to shown 'why' ppe is, or is not, used by exploring the factors that influence the use-specifically of gloves and masks-during routine care, in one ed. we employed methods that allowed close engagement with clinicians so as to understand their choices and behaviours and utilised the theoretical domains framework (tdf) [34] to assess the relevant enablers and barriers. a better understanding of these practices in this context could assist managers, educators and clinicians to optimise enablers and address barriers, locally, and inform health policy and pandemic planning more widely. this qualitative study used ethnography to explore the use of gloves and masks by clinicians in an ed. this is a suitable methodology for the study of complex social and clinical interactions in the context of healthcare quality and safety [35] as it involves direct observation of the behaviour of people and their social environment using varied data collection methods. the theoretical underpinnings of this research are grounded in behavioural science, in particular the tdf, which was used to inform the interview guide and subsequent data analysis. the tdf synthesises multiple theories of behaviour and behavioural change into 14 domains which provide a framework for examination of cognitive, affective, social and environmental determinants and influences on behaviour [36] . it has been used widely in patient safety research [37] , including clinicians' ipc practices [38] and is particularly useful for informing policy and planning practice improvement. the setting was a busy ed with over 72,000 presentations per year in a major tertiary hospital in sydney, australia. departmental staff were informed about the study through a staff e-newsletter and during several morning staff meetings which are attended by all staff on duty that day. a purposive snow-ball sampling technique [39] was used to recruit clinical and non-clinical staff working in the department for semi-structured interviews, so as to obtain a crosssection of professional roles, experience and clinical expertise. approval for this study was given by the western sydney local health district human research ethics committee. written consent for interview was obtained by the researcher after negotiation with each participant in accordance with the approved study protocol. the researcher attended the ed during day shifts for one to two hours at a time, observing and taking notes on activities directly related to the aim of the study. local and hospital policies, signage, and other documentation relating to use of ppe in the ed context, were examined. reflexive review of field observations and documentation, was used to inform the interview guide [40] but not included in the analysis reported here. twenty-two face-to-face, semi-structured interviews, lasting 10-45 min (average 28 min), were conducted with clinicians (nurses and doctors) and non-clinical support staff at times and places convenient for them during the day. interviewees comprised five senior doctors (dr), seven nurses in senior roles (clinical nurse consultant [cnc]/ nurse manager [nm]/ nurse practitioner [np]), two registered nurses (rn), one enrolled nurse (en), two nurse graduates (ng), two support workers (sw) and two senior external clinicians from the ipc (cnc) and infectious diseases (dr) departments. the questions were guided by the 14 domains of the tdf and focused on the desired behaviours of optimal compliance with glove and mask use. interviews were audio-recorded and subsequently transcribed verbatim. interviewees were invited to review their transcripts for accuracy. the data was analysed using a content and thematic approach in order to gather an in-depth understanding of factors affecting optimal glove and mask use. transcripts were reviewed independently by two researchers, the content was coded into tdf behavioural domains relating to the target behaviours [36] and analysed thematically. no data were lost in the transcription or the interpretive analysis. thirty-one behavioural themes were identified that influenced participants' use of protective masks and gloves. these were mapped against the theoretical domains (table 1 ) and further analysis allowed them to be classified as enablers and barriers to optimal use. the data revealed interdependency between some domains, resulting in natural grouping of the findings. for example, "participants' beliefs about the consequences" (tdf6) of glove and mask use were linked to "emotion" (tdf12) such as anxiety; therefore, the findings are described together. there was also mirroring of themes whereby one could be either an enabler or barrier within the same domain. for example, "knowledge" (tdf1), was an enabler of glove use but a barrier to appropriate mask use. findings are reported under tdf domain titles within the categories of enablers and barriers. in this study, enablers of optimal ppe use were represented in all domains; however, there were more enablers of optimal glove, than protective mask, use. enablers include a variety of factors that encourage, facilitate or are likely to increase glove or mask use (not necessarily appropriately) including internal/personal factors such as self-protection and/or external factors, as detailed next. participants' knowledge and skills, self-efficacy and confidence in the equipment, were interconnected as key enablers of optimal ppe use. all participants reported having received instruction in the use of ppe during either their professional or induction training. optimal use of gloves and masks was further enabled through education provided by the hospital ipc team or by some other clinicians with broader knowledge and/or interest in ipc. participants please cite this article in press as: barratt reported that high-level ppe skills had also been enhanced in recent years through simulation exercises for ebola virus disease. 'look, whenever there's attention to something, like the ebola, we had a lot of in-services regarding donning and doffing.' (doctor [dr] 2) most clinicians' perceived knowledge of ipc policies supported their use of gloves as appropriate for standard and transmissionbased precautions. optimal ppe use had been further promoted recently through the introduction of an ed-specific poster that identified ppe required for specific diseases, which was attached to isolation trolleys and positively received by staff as helpful, particularly in choosing the correct mask. the majority of participants reported they were confident with the protection provided by the equipment and in their ability to correctly don and doff gloves and protective masks. 'i got taught that fitting of the mask, when the ebola . . .. was out. i remember being taught properly then how ppe should be worn.' (enrolled nurse [en]1) the participants' understanding and abilities in ppe use were consistent with their professional responsibilities as described in the next section. an important enabler of optimal glove and mask use was the professional responsibility some clinicians felt towards protecting patients from infections. for example: 'so yeah, the staff should also then be taking on some of that ppe responsibility, infection prevention responsibility.' (dr4) another associated professional responsibility that influenced appropriate glove use was the perception, by several doctors, that when there was no obvious risk of contamination, not wearing gloves facilitated a better doctor/patient relationship. this professional role identity was interconnected with the participants beliefs about the consequences of not using ppe, as outlined next. protecting themselves and not taking infection home to their family were reported to be strong motivators of ppe use. this belief in the negative personal consequences of not using ppe was often emotive: 'my concern is (a) infecting me and then taking it home to my family.' (dr3) glove use in particular was determined by the perception of personal risk, as summarised by this participant: 'personally, i will put gloves on if obviously there's blood, patient's got blood on them, so a trauma patient, i would generally put gloves on. patients who are a bit unhygienic, i'll put gloves on. so, both of these instances are to protect myself.' (dr3) for others, their use of ppe was influenced by previous experiences, such as working in the early days of hiv or having a urine splash to the face. the many participants who described a personal motivation for ppe use may have influenced the overall social culture within the department. the departmental norms and peer behaviour in the ed both reinforced and positively enabled clinicians' use of gloves, but less so for masks. glove use was reported to be embedded in routine tasks and patient encounters and clinicians would wait for, or remind, colleagues to don gloves when attending a patient: 'there's definitely a culture of these are the tools that we use to do our work. . . . and what i do notice is that people wait for you to put your gloves on.' (cnc 1) during the winter respiratory virus season, visual signals such as patients wearing surgical masks or an increase in boxes of masks in clinical areas helped to reinforce mask use. staff were also expected to wear a mask when caring for a neutropenic patient: 'just the only other time when i think about wearing masks, is in patients who are in neutropenic. because that's the other setting where we say that it's required.' (dr1) the behavioural norms within the ed also influenced the individual's routine and habitual practices related to gloves and masks. although some medical staff reported using risk assessment to determine the need for gloves, as described above, the entrenched habit of most staff using gloves routinely for patient contact had the positive effect of facilitating their use when it was indicated as part of standard precautions. as this nurse explains: 'it's an autopilot thing, as soon as they go and get a new patient, straightaway grab a set of gloves and start doing what they need to do.' (registered nurse [rn] 4) while glove use was almost automatic for the participants from the department, clinicians reported making a conscious decision to wear a mask. medical staff in particular reported making a risk assessment for mask use which was prompted by visual cues such as isolation trolleys and signs by the bedside or certain clinical information handed over about the patient: 'like the measles or something along those lines. that would prompt me to think, i need a mask and then let [the] nursing staff as well know. or a tb patient.' (dr2) support staff also chose to wear masks and gloves on occasions when they deemed there to be a risk of infection to themselves, as described by the following support worker: within the physical environment of the ed, staff were generally satisfied with the brand of gloves provided and noted that they were very accessible, which was an enabler of optimal use. the recent introduction of isolation trolleys, for patients in transmission-based precautions in curtained bed spaces, facilitated please cite this article in press as: barratt the support staff also found the isolation trolleys useful to alert them to the infectious status of a patient: 'if they go to enter a room and see the trolley outside they won't bother 99% of the time as not urgent enough to do so. or if they really have to they will put on the type of mask that is on the trolley.' (sw1) behaviour towards ppe was also influenced by the organisational ipc requirements for hospital accreditation. although no specific ppe monitoring was in place, annual training was encouraged. 'so we're trying to instil that they need to do an annual [ppe] competency. it's available, we're definitely not there yet.' (cnc ipc) the introduction of hospital-wide hand hygiene audits helped to promote correct hand hygiene behaviour around glove use and was reported to be an enabler. 'i am more compliant with hand washing prior to glove use than i probably was when i first trained.' (dr1) as illustrated, a range of factors were identified by participants as enablers of optimal ppe behaviour, primarily for glove use. within the same tdf domains, barriers to mask and gloves use were also described. unlike enablers, which mainly related to glove use, barriers to protective mask use were more frequently described by participants. as noted earlier, knowledge of policy was an important enabler of optimal ppe use. however, despite the ready availability of ppe policies and educational resources, participants described mask and glove practices that did not adhere to policy. thus, in this department, information resources and policy were sometimes a barrier because they were confusing. one clinician pointed to the various posters and guidelines as 'information overload', while others suggested that hospital-wide policies were not clear or did not work well in the ed context. 'i think that some of our bad practices, or some of our practices that, where you find someone wearing the wrong mask is all due to the fact that when we're educating and when we're following policy, the policy has been very, very ambiguous.' (cnc1) indications for which type of mask to use are described in the ipc policy relating to transmission-based 'airborne' and 'droplet' precautions. however, as the following participants describe, these terms were not always well understood and indicated a knowledge gap around the functionality and usage of the different types of masks. consequently, both medical and nursing staff reported choosing whichever mask was handy, not necessarily the one required, as the following nurse participants reported: 'if you said droplet or airborne you'd just mostly get a blank face and look at you and they might come up and go, well, maybe i need for the airborne the orange but i'm not sure . . . ' despite a knowledge of hospital policy towards masks, several participants preferred to apply their own professional autonomy in relation to mask use. professionally, some medical staff felt that using a mask restricted their ability to provide good clinical care, as it hindered communication and empathy with patients. the following participant felt that the mask interfered with their clinical assessment: 'the problem is, if you need to communicate with people, the mask can, particularly the n95, can muffle your voice as well.' (dr5) another doctor perceived the mask as an obstacle to establishing a good understanding between themselves and the patient: 'but i don't want to be the one that's wearing the mask and making the patient feel like there's a barrier. (dr6) these aspects of the use of ppe that clinicians presented as barriers to their use, because it interfered with their professional role, were interconnected with their beliefs about the consequences of not using ppe, as outlined next. as described previously, an exaggerated perception of infection risk, leading to overuse, was a potential barrier to appropriate use of gloves: 'i'm probably not the best person because i think i probably overdo gloves. i do not even feel comfortable shaking hands with a patient without gloves.' (dr6) by contrast, minimal concern towards the risk of respiratory infection was a barrier to mask use. one clinician attributed this to her own immunity, while another suggested that he was as likely to get a cough or cold as a member of the general public as when working. 'i never wear a mask during the flu season unless obviously i felt like i had the flu. you know, my view of the flu is i get immunised. i catch a train and everyone coughs on me anyway. and i'm more likely to have immunity against things like that because i never get sick.' (dr2) 'so, yes, if they have a respiratory symptom, if they have a fever, there is a history of overseas travel and i'm suspecting some unusual organisms, yeah then i will . . . but if it's like cough and cold, just minor symptoms, probably not because we get exposed to it when we are out in public and in the shopping centre, anyway, and i wouldn't.' (dr6) another participant suggested that in the absence of visual reminders for infectious respiratory diseases such as a productive cough, they did not perceive enough risk to wear a mask. similarly, participants also felt a lack of personal risk if the patient was wearing a mask, although they acknowledged that it was often not worn correctly by the patient. however, potential consequences for other patients were not reported as a motivation for ppe use outside of caring for the immune-compromised patient. '. . . gloves are really more for our protection, especially, way more than they are for the patient's protection.' (rn2) these common perceptions of risk were re-enforced within the social setting of the unit. unlike glove use, there was no departmental norm for wearing protective masks, except when attending to immunosuppressed patients. although there was a general consensus that mask use could be improved, peer influence or role modelling was limited to a few senior nurses and doctors. 'i mean part of your ppe, you probably should put a mask on, but we generally don't.' (dr3) 'i guess, in general we don't use masks.' (rn3) the absence of a departmental culture of wearing protective mask impacted on the clinicians' intentions and decision-making, as described below. one of the barriers to optimal mask use was the lack of habitual mask use in daily care requiring the individual to make a conscious decision to use a mask as illustrated in this excerpt: 'but because it's not business as usual the only thing that would prompt me initially would be to think, oh i could get a splash here, so therefore i'll wear a mask.' (cnc1) conversely, although glove use was prompted by unconscious behaviours, this could lead to unnecessary glove use: 'but i've noticed that's something that happens a lot nowadays, that just to touch a patient, people will put gloves on, and i encourage them not to do that; that they don't need to, that the patient is not dirty.' (rn2) the individual's decision-making processes were also related to the environment within which they worked, as outlined next. the busy, chaotic context of an ed, was reported by many participants to be a barrier to optimal ppe use: 'and it's just so busy that sometimes you can see that, yeah, something might not be quite by the books because of the pressure and the stress of the environment and the amount of people coming in and out.' (enrolled nurse [en]1) participants cited urgency of care as barriers to performing hand hygiene prior to donning gloves (it took too long for the hands to dry) or mask. 'the fit test can be a bit of a deterrent in a busy environment, to have to make sure it's fitted properly.' (cnc1) '. . . the time to put it on and off, particularly if someone's sick.' (cnc3) there was also a belief that the differences between the ed environment and an inpatient unit allowed for different ppe practices. 'it's culturally acceptable in an emergency to doattend your cares of a patient without those precautions where it's not in the ward.' (np1) the lack of a designated place for boxes of masks -other than isolation trolleys -sometimes made it difficult to locate a mask and was a barrier to the use of masks for standard precautions. the open-plan layout of the department, with only two single isolation rooms, was also identified by several participants as a deterrent to implementing good ipc practices. 'so once they're not in those [isolation] rooms and they're just out in the general acute area, i think [staff are] much less so likely to adhere to those precautions.' (dr3) compared to general satisfaction with the gloves provided, participants described more undesirable qualities with using the masks. some participants reported that the n95/p2 masks were more difficult to don, while others described discomfort and fogging of their glasses or protective goggles when wearing a mask. for one participant the discomfort of wearing a mask interfered with her ability to provide clinical care. 'like i really think it does make me abridge my assessment and examination because my desire to get the mask off is great.' (dr3) unlike hand hygiene audits, participants reported other external ipc monitoring as a barrier to optimal ppe use. this participant changed her behaviour with masks due to expectations of ppe audits: 'i think it's a bit of a throw-back from infection control. they will teach us about this mask and that mask, and then come and audit you, and then you're always afraid you're using the wrong one. so you just choose the higher one.' (cnc1) this ethnographic study explored the behaviour of clinical staff towards use of gloves and protective masks in a busy ed. analysis using the tdf elucidated factors that either promote or impede (occasionally both, in different circumstances) optimal ppe use, some of which have been identified previously in the literature [6] . however, we also revealed ed-specific determinants of glove and mask use that have not been previously described. in addition to providing emergency care of patients, front-line clinicians play a central role in the initial screening, detection and ipc management of suspected but undifferentiated infectious diseases. this role inevitably puts them at personal risk of infection. therefore, protective barriers such as ppe are essential to minimise the risk both to themselves and to other patients. although occu-pational health and safety is important, clinicians should be aware of their professional duty towards patient safety. an important finding in our study was a significant difference, in use, between gloves and masks in that there were more reported enablers of use of the former and barriers to use of the latter. existing research has demonstrated that gloves are the most frequently used item of ppe, much more so than masks [15] . a significant factor associated with frequent glove use idenitified in this study was some participants' motivation to use them for their own protection as a routine precaution. glove use was even more prevalent when there was a higher risk of blood and body fluid contamination, such as in the trauma and resuscitation areas. this aligns with the literature which reports compliance rates of 93-99% for glove use during trauma encounters in ed [25, 26] . less obvious contamination risks, such as an unrecognised mro-colonised patient, were also identified by participants as reasons for glove use. these patients present a significant risk in the ed for environmental contamination and staff acquisition [41] . some participants argued that habitual use of gloves was a barrier to optimal use. it is difficult to ascertain whether the glove use was excessive as there is no published research that explores the indications for and use of gloves in an ed. a recent systematic review of glove use and transmission of infection in other inpatient departments concluded that gloves were often overused and misused [42] . the published literature related to hand hygiene auditing provides some indication of ed rates for glove use. during a hand hygiene observational study in an ed, carter et al. [43] reported that only 32% of hand hygiene opportunities, whether or not hand hygiene was performed, were associated with glove use, indicating that in this setting, the majority of patient encounters did not incur the use of gloves. nevertheless, when optimising behaviour for cross infection, attention should also be focused on hand hygiene practices associated with the use of gloves [29] . in comparison, participants described fewer enablers of mask use, which reflects that they are used much less so than gloves [15] . the apparent under-use of protective masks in this study reflects literature reports of low rates (3-25%) for mask compliance in the ed setting [25, 26, 44] . the optimal use of protective masks by healthcare workers has been shown to reduce transmission of sporadic and epidemic infectious diseases. during the global sars outbreak in 2003, sars-cov transmission in a vietnamese hospital was significantly reduced when protective mask use among clinical staff increased [45] . skowronski et al. [46] attributes the prevention of sars transmission within a vancouver hospital to the prompt implementation of ipc measures, including ppe, in the ed for a traveller returning from asia with severe influenza-like illness. this is in contrast to the outcome for a similar case in toronto, when droplet and airborne precautions were not put in place in the ed for over 21 h, resulting in 14 further cases of cross infection [4] . many participants blamed the chaotic, fast-paced ed environment, as a significant barrier to using a mask. while this argument has been reported previously [44] , the same contextual reasoning could also apply to gloves, which are in fact regularly used and take longer to don and doff-at least if hand hygiene is included. thus, other factors may be more influential determinants of mask use, such as the team behavioural norms in the department or the individual's perception of risk of infectious diseases. one barrier to optimal mask use demonstrated in our research was the strong personal belief about ppe use of some senior medical staff, which overrode ipc policy. this is reflective of a recent study which found that the clinical autonomy of doctors was a significant factor in their ipc practice [47] . in an ed where there are numerous 'leaders', different role models and aberrant behaviour can impact negatively on the ipc culture of the department. participants identified a lack of positive role modelling and leadership which has been shown elsewhere to influence individual behaviour towards ppe [26, 47, 48] . in contrast to our findings, a recent qualitative study that utilised focus groups with nurses and assistants, reported a positive peer culture for encouraging respirator mask use [49] . this may indicate a greater perception of risk associated with diseases that required an n95/p2 respirator mask. in our study, a clinician's reduced perception of risk of infection from facial exposure was a barrier to wearing a mask. furthermore, clinicians perceived less risk to themselves when the patient was wearing a protective mask for a potential respiratory disease and felt protected enough not to wear a mask. public health guidelines recommend that symptomatic persons in hospital waiting rooms and other public spaces are given a mask to wear to prevent transmission of respiratory infection [50, 51] . this measure is largely accepted by the public and has had some success in community settings [52] [53] [54] . however, research is limited on its protective effect for clinicians engaging in direct patient care. the literature also reports the problem of noncompliance with mask use by the public [55] . this risk may increase in the ed setting, where, as identified by participants in our study, patients are unwell and often non-compliant in correct mask use. to prevent early transmission of either routine or outbreak infectious diseases, frontline staff must be vigilant and adhere to routine ipc measures [51] . this study identified the barriers to implementing effective protective mask use, which can be difficult in facilities with few isolation rooms or where staff rely on visual or verbal cues to instigate appropriate precautions [56] . in addition, the placement of boxes of masks was a practical barrier. poor access to masks is also a common finding in the literature [44, 57, 58] . in our study setting the introduction of ten isolation equipment trolleys addressed some of these barriers. applying human factors design principles is one method to address some of the contextual environmental barriers to optimal ipc behaviour such as difficult access to ppe [14, 59] . it is worth noting that in this study an exclusively policy-driven approach to ppe use was not a consistent enabler of optimal practice. although normally viewed as a facilitator, policy in this setting was viewed as a barrier to optimal mask and gloves use. bouchoucha and moor [60] suggest that deviating from ipc guidelines and policy can have serious consequences for patient safety. on the other hand, other authors have recognised that the unique complexity of an ed environment can challenge conventional ipc protocols and practices. for example, liang states that overcrowding, multiple clinician-patient encounters, limited isolation facilities and other factors unique to an ed are barriers to good ipc practice [61] . chen et al suggests that, compared to inpatient settings, it is more difficult to implement ipc measures in an emergency or outpatient department [62] . the study has some limitations. it reports participants' perceptions of the enablers of and barriers to optimal ppe use for routine care in one australia ed. this is a single-site study, and the findings are not expected to be representative in their totality of other eds. other eds will inevitably have characteristics which mediate enablers or, and barriers to, optimal ppe use, although it is expected that those identified in this study have resonance. the study design did not permit verification or otherwise of these findings beyond what was possible to observe during the field immersion. our findings have demonstrated that the determinants of ppe behaviour in an ed differed significantly between gloves and masks. the spread of emerging infectious diseases that have been responsible for global outbreaks recently, has included respiratory droplets. ed clinicians should therefore ensure that, as with gloves, the use of masks is incorporated into routine care where appropriate. these results support the need for further research which examines items of ppe independently. rb, glg, sh and mw conceived and designed the study and prepared the study protocol. glg supervised all data collection and study procedures. all authors contributed to interpretation of the results, preparation of the manuscript and approval of the final version. this work is supported by the australian partnership for preparedness research on infectious diseases emergencies (apprise) of which author glg is a chief investigator and author rb is recipient of a doctoral scholarship. the research presented in this article is solely the responsibility of the authors and does not reflect the views of apprise. rs is editor-in-chief of australasian emergency care but played no role in the peer review or editorial decision-making of the manuscript whatsoever. the authors declare no other conflict of interest. report on the burden of endemic health care-associated infection worldwide scope and extent of healthcare-associated middle east respiratory syndrome coronavirus transmission during two contemporaneous outbreaks in riyadh, saudi arabia healthcare-associated infections: the hallmark of the middle east respiratory syndrome coronavirus (mers-cov) with review of the literature responding to the severe acute respiratory syndrome (sars) outbreak: lessons learned in a toronto emergency department risks to healthcare workers with emerging diseases recognizing and managing emerging infectious diseases in the emergency department a descriptive analysis of occupational health exposures in an urban emergency medical services system risk and management of blood-borne infections in health care workers exposure to influenza virus aerosols during routine patient care transmission of middle east respiratory syndrome coronavirus infections in healthcare settings australian guidelines for the prevention and control of infection in healthcare national health and medical research council compliance with standard precautions: results of a french national audit a review of the evidence for suboptimal compliance of healthcare practitioners to standard/universal infection control precautions improving healthcare worker adherence to the use of transmission-based precautions through application of human factors design: a prospective multi-centre study incompliance in use of universal precautions as a safety measure in emergency department evaluation of respiratory protection programs and practices in california hospitals during the 2009-2010 h1n1 influenza pandemic lack of compliance with basic infection control measures during cardiopulmonary resuscitation-are we ready for another epidemic? facial protective equipment, personnel, and pandemics: impact of the pandemic (h1n1) 2009 virus on personnel and use of facial protective equipment self-reported use of personal protective equipment among chinese critical care clinicians during 2009 h1n1 influenza pandemic. santin m severe acute respiratory syndrome (sars) and healthcare workers centres for disease control and prevention. guidelines for prevention of transmission of human immunodeficiency virus and hepatitis b to health-care and public-safety workers compliance with universal precautions in a university hospital emergency department substantial improvement in compliance with universal precautions in an emergency department following institution of policy a comparison of observed and self-reported compliance with universal precautions among emergency department personnel at a minnesota public teaching hospital: implications for assessing infection control programs compliance with universal precautions among emergency department personnel caring for trauma patients trauma team utilization of universal precautions: if you see something, say something occupational exposure during emergency department thoracotomy use of personal protective equipment in canadian pediatric emergency departments predictors of hand hygiene in the emergency department hand hygiene before donning nonsterile gloves: healthcareworkers' beliefs and practices clinical glove use: healthcare workers' actions and perceptions a review of the evidence for suboptimal compliance of healthcare practitioners to standard/universal infection control precautions instruments for evaluating compliance with infection control practices and factors that affect it: an integrative review validation of the theoretical domains framework for use in behaviour change and implementation research applying ethnography to the study of context in healthcare quality and safety: table 1 a guide to using the theoretical domains framework of behaviour change to investigate implementation problems applying the theoretical domains framework to identify barriers and targeted interventions to enhance nurses' use of electronic medication management systems in two australian please cite this article in press as: barratt r, et al. enablers of, and barriers to, optimal glove and mask use for routine care in the emergency department: an ethnographic study of australian clinicians australasian emergency care xxx (2019) xxx-xxx hospitals does the use of a theoretical approach tell us more about hand hygiene behaviour? the barriers and levers to hand hygiene social research methods coding, sorting and sifting of qualitative data analysis: debates and discussion emergency department environmental contamination with methicillin-resistant staphylococcus aureus after care of colonized patients glove utilization in the prevention of cross transmission: a systematic review environmental factors and their association with emergency department hand hygiene compliance: an observational study behind the mask: determinants of nurse's adherence to facial protective equipment factors associated with nosocomial sars-cov transmission among healthcare workers in hanoi coordinated response to sars the politics and ethics of hospital infection prevention and control : a qualitative case study of senior clinicians' perceptions of professional and cultural factors that influence doctors' attitudes and practices in a large australian hospital nursing students' intentions to comply with standard precautions: an exploratory prospective cohort study health care workers' perceptions and reported use of respiratory protective equipment: a qualitative analysis assessment of hospital emergency department response to potentially infectious diseases using unannounced mystery patient drills the great influenza centennial-what have we learned about the epidemiology and prevention of transmission? mask use, hand hygiene, and seasonal influenza-like illness among young adults: a randomized intervention trial prevalence of preventive behaviors and associated factors during early phase of the h1n1 influenza epidemic impact of non-pharmaceutical interventions on uris and influenza in crowded, urban households facemasks for the prevention of infection in healthcare and community settings respiratory protection policies and practices among the health care workforce exposed to influenza in new york state: evaluating emergency preparedness for the next pandemic current practices and barriers to the use of facemasks and respirators among hospital-based health care workers in vietnam barriers to the use of face protection for standard precautions by health care providers interventions to improve hand hygiene compliance in emergency departments: a systematic review infection prevention and control: who is the judge, you or the guidelines? infection prevention for the emergency department interpretation and clinical practice of regulation for prevention and control of healthcare associated infection in outpatient and emergency department in healthcare facilities key: cord-266123-q75f12vh authors: lin, che-huei; lin, ya-wen; wang, jong-yi; lin, ming-hung title: the pharmaceutical practice of mask distribution by pharmacists in taiwan’s community pharmacies under the mask real-name system, in response to the covid-19 outbreak date: 2020-10-19 journal: cost eff resour alloc doi: 10.1186/s12962-020-00239-3 sha: doc_id: 266123 cord_uid: q75f12vh background: pharmacists hold to their promise to foster, implement and promote the health of the population and to prevent disease, given their knowledge, skills, and proximity to the locals. the objective of this study was to foster equality and cost-effectiveness in the distribution and sale of masks to all taiwanese citizens, in response to the covid-19 pandemic. methods: all 6336 special community pharmacies participating in the nhi (national health insurance) served as mask-selling sites. access to masks by citizens was determined and controlled, based on the weekly rationing of the number of purchasable masks per citizen and the last digit of their nhi card number. masks were available on different weekdays for holders of cards ending with odd and even numbers, except on sundays, when everyone was eligible to buy a mask. results: implementing the program has provided equal access to masks for all citizens across taiwan. it has stabilized the pricing of masks and mitigated the public’s anxiety of a perceived likely market shortage. conclusion: the community pharmacy-based approach to the distribution of prevention face masks to citizens represents a new and innovative engagement of pharmacists in public health promotion and protection initiatives. community pharmacies can greatly improve the efficiency, reliability, and cost-saving of the distribution of public health resources to local communities, especially in the face of an epidemic. at the core of founding an informed public health management strategy, there should be an emphasis on the need to engage and empower individuals and communities to assure their own health, and that of others, while mitigating and responding to the public health risks and related exposure within the population [1] . this is a defining component of the typical health services utilization process and the behavior of all members of society, despite their entry point into the health system [2] . the community pharmacy-based program for the 'mask real-name system' demonstrated the potential competitive value that is inherent in pharmacists who cost effectiveness and resource allocation *correspondence: lmh.roger@msa.hinet.net † wang jong yi and lin ming hung contributed equally to this work 1 department of pharmacy and master program, tajen university, pintung 90741, taiwan full list of author information is available at the end of the article enhance the distribution-related outcomes of scarce public health management resources to target populations and communities. specifically, the active involvement of pharmacists across taiwan in the implementation of public health promotion and disease control efforts is associated with optimizing the outcomes, by enhancing the management of such efforts for the cost-effectiveness and reliability of their reach and impact on society [3, 4] . the prospects for realizing and sustaining a healthy population cannot be assumed where there is no system-wide commitment to embrace and promote wellinformed, value-laden public health and protection strategies by all the relevant stakeholders in public health. at the core of the fundamental features of an informed public health management strategy, there should be an emphasis on the need to engage and empower individuals and communities to assure their own health and that of others, while mitigating and responding to the public health risks and related exposure in the population [1] . national public health efforts, especially in the wake of a pandemic, can be overwhelming to health systems, in terms of the costs and implementation technicalities, among other challenges. to this end, the critical value of investing in innovative population health management strategies, as a safeguard for assuring the sustainable competitive performance of the health system of a country, cannot be over-emphasized. pharmacists boast that they have the knowledge, skills, professional expertise and proximity advantage that are needed to facilitate and contribute value-laden outcomes related to the implementation of the health promotion and disease prevention efforts by the government [1] . they are a defining component of the typical health services utilization process and behavior by all members of the society, despite their entry point into the health system [2] . in taiwan, community pharmacies have proved to be an invaluable resource for the government in helping to implement various health promotion initiatives. from their active involvement in the recovery of residual medicines, discarded medicines, and aids syringe recycling, to anti-drug education and campaigns in primary schools and community drug safety workshops, as well as smoking cessation and advocating the preventation of the betel nut hazard, community pharmacies play an important role in the promotion of public health prevention and treatment in taiwan (additional file 1). during the continuous spread of the novel coronavirus epidemic, which started in february 2020, and its related effect on fueling the global phenomenon of chaotic mask purchases, the taiwanese people were seen lining up overnight to buy masks, which caused panic and a crisis throughout the country. the taiwan government quickly announced a ban on the export of masks (2020 feb 6) and the national mask factories were requisitioned to distribute them uniformly [5] . at the same time, the government announced the implementation of the "mask real-name system" policy for face mask distribution to individuals and families across the nation (additional file 2). this policy was the outcome of a high-profile meeting of government officials from the epidemic prevention bureau and the center for disease control (cdc) of taiwan, experts from the taiwan pharmacists association, as well as representatives from the chunghwa post, concerning the feasibility of the "mask real-name system "amidst the fight against the ongoing covid-19 pandemic. by march (1 month after the implementation), the federation of taiwan pharmacists associations, based on the sale of masks in pharmacies in all the counties and cities, found that adults currently use three, and children use five, masks per week, and each pharmacy receives 250 customers per day. in fact, the national mask coverage rate is merely 40%, on average (statistics of the federation of taiwan pharmacists associations, march 2020). since april 17, when the 'mask real-name system' was put into operation, 6336 community pharmacies across taiwan have seen a total of 9,750,000 customers buying masks under the real-name system per week, and a total of 39,000,000 customers (250 customers per day) per month. in addition, according to statistics from the national health insurance administration of the ministry of health and welfare, 20.41 million people have bought masks since the mask real-name system began on february 6. as of april 29, 20% (about 3.99 million people) have purchased masks from the internet and physical stores, 7% (about 1.45 million people) have only used the internet (including supermarkets) to buy masks, and 73% (about 14.96 million people) have bought masks from physical channels, such as community pharmacies or health clinics (source: ministry of health and welfare). given their proven performance record as being a reliable resource for helping to implement public health promotion initiatives by the taiwanese government, community pharmacies were enlisted to assist in the distribution of face masks to citizens across the country. the objectives were to foster the efficiency, reliability, and cost-effectiveness in the distribution process and to enhance the equality and fairness of access by all taiwanese citizens to face masks. the taiwanese government is on record as having the highest coverage rate (99%) for national health insurance (nhi) and the most comprehensive health insurance database in the world. in total, the 6336 special community pharmacies participating in the nhi were according to the announcement of the ministry of economic affairs, the cost of raw materials for masks rose to 118% in april 2020, and climbed to 150% in may. however, the ministry of health and welfare stipulated that the price of masks sold to the public by community pharmacies should be nt$5 per mask (the price of masks before the pandemic was about nt$2 per mask). besides, all mask factories were dispatched to produce masks. since february 6, when the mask real-name system was launched, the central epidemic command center announced further, on july 1, 2020, that the mask real-name system would be extended to december 31, 2020. at the same time, from june 1, the ministry of health and welfare announced that some masks can be freely traded in supermarkets. however, the selling price varied greatly from nt$6 to nt$10 per mask, while the price of masks under the real-name system was controlled by the government at nt$5 per mask. in addition, to mitigate chaotic mask-purchasing behavior and the related risk of prompting undue face mask shortages in the market, as well as the possibility of creating a public panic and a crisis across the nation, the distribution and sale of face masks to citizens via community pharmacies was based on a rationing system [5] . the ration for the number of face masks available for purchase at the start of the program was two face masks per week for each adult and child in the country, but on february 20, the number was increased to four masks per week per individual, for both adults and children. to purchase masks, individuals needed to take their health insurance card to the community pharmacy and swipe it for the purchase, and the data were uploaded to the nhi cloud system to automatically check whether the masks were being bought repeatedly. the system also displayed the available inventory of the purchases. there was also an ongoing effort by the government, in collaboration with non-governmental organizations (ngos), to develop a "mask map" app to provide details concerning the location of nearby pharmacies and the available inventory. the ministry of health and welfare requires the department of social welfare of local county and city governments to cooperate with the department of health and to manage a list for the physically disabled and the elderly who live alone, and the ministry of health was required to visit and distribute the masks, together with the social workers. village officials may carry out the above affairs on behalf of the ministry of health. the implementation of the program required the collaboration of pharmacists serving within community pharmacies, the finance personnel, information technologists, as well as the producers and distributors of face masks in the nation. the eligible buyers were determined by using the value of the last digit on the nhi card number of each individual and the data of their purchase history from the nhi database. these policy provisions were meant to mitigate the possibility of individuals engaging in multiple mask purchases. pharmacists in the community pharmacies determined and informed the local residents on the availability of masks and the specific times that they could make their purchases. in making this determination, pharmacists had to consider the available mask inventory levels, relative to the demand for masks by health care personnel within their local communities, as well as the timing when the majority, if not all, of the locals were available to make the purchases. the involvement of community pharmacists in selling prevention masks greatly enhanced the control of the distribution of face masks in markets across the nation. notably, this approach to the distribution and sale of masks mitigated the free-market approach to sales, by ensuring that masks were only available for sale to citizens through registered community pharmacies. this eliminated the chaos of having rising market prices, as it offered government authorities the upper-hand in setting and enforcing the mask prices. it was also an effective way of alleviating public anxiety about a likely mask shortage. above all, it provided a competitive means for safeguarding the healthcare system from undue mask shortages, by prioritizing the demands of the healthcare personnel mask during allocation. furthermore, details on the travel history of individuals were also filtered through the nhi cloud system, which, in turn, helped to improve the identification of subjects requiring isolation and those violating the isolation mandates of the taiwanese government in the fight against the covid-19 pandemic. the community pharmacy-based approach to the distribution and sale of prevention face masks to citizens for the ongoing covid-19 pandemic has proven to be a new and innovative engagement of pharmacists in contributing to the efficient, reliable, equitable, and costeffective implementation of public health promotion and protection initiatives by the government. by providing the increased electronic tracking and reporting of face mask sales in the various communities across the nation, community pharmacies provide the nhi with an informed and reliable mechanism for mitigating chaotic incidents in the distribution, selling, and purchasing of masks across the country [6] . this approach provides a quick way of securing and reporting data to be used for the government's planning and decisions on the production and distribution of face masks to meet the underlying objective of safeguarding equal access to pandemic prevention resources by all citizens across the nation. in particular, this approach is valuable for enhancing costsavings by the nhi, as it eliminates the arbitrary setting of mask prices by vendors in the marketplace. the "mask real-name system 2.0" program is based on the revision of the tax filing software of the ministry of finance. it features a stable system and immediate online operation. however, this system needs to be equipped with a card reader to read the health insurance card and it can only operate on a computer, which is inconvenient for mobile phone users and it cannot, therefore, be popularized among the public. to make it accessible for all people, the government immediately introduced the mobile phone app, in order to connect with the national health insurance system. to avoid long night-queues to purchase masks, the "mask real-name system 2.0" has changed the "queuing system" into a "registration system", with the aim of dispersing people, reducing the pressure load on the computer system, and preventing people from queuing up to buy masks. the taiwanese government has been engaged in multiple steps from mask exports, to production, pricing to rationing. such engagement in the real-name system has brought many benefits. the price of masks is stable and people can obtain masks at a lower price than in other countries, thus avoiding the epidemic prevention gap caused by the inequality between the wealthy and the poor. in addition, the government's capital and manpower, such as the army's support for mask production, have also been key in increasing the mask production capacity. therefore, the implementation of the real-name system allows people to acquire a certain number of masks on a regular basis, which effectively reduces the crowds. some of the shortcomings and difficulties faced by the selling of real-name masks in community pharmacies are as follows: (1) community pharmacies need to pack and sell the masks. each pharmacy needs to handle an average of 2000 masks per day. in addition to the daily pharmacy sales, the community pharmacies are required to employ more people; (2) in some community pharmacies, one person is responsible for the whole pharmacy business, and some pharmacists are either in a poor physical condition, pregnant, or unable to provide services for long periods of time, due to family factors, or age; (3) the taiwanese government has extended the mask real-name system till the end of december 2020. pharmacists in community pharmacies are generally exhausted, both physically and mentally, because of irrational people who come to buy masks, so they often suffer abuse and their personal safety is threatened. however, the planned economical mode of the government will definitely stifle the mechanisms and advantages of the free market. under the government pricing control, people can obtain masks at cheaper prices. in addition, a fixed quota seems to be equal for everyone, and it does not reflect the differences in personal and family needs. for example, medical personnel or business sales personnel actually do need a different number of masks every week. it is not feasible to adjust the rations, so as to quantify the differences in lifestyles. moreover, it may also lead to ethnic opposition, occupational discrimination, and other related issues. furthermore, given that the program is integrated with the nhi database, and hence, the electronic health and medical records of patients across the nation, it allows pharmacists in community pharmacies to assist in the tracking and filling of signed prescriptions for local patients with chronic diseases. in particular, it promises to improve the coordination of supplies for critical medicines and related pharmaceuticals to community pharmacies, which is critical for reducing the number of people going to a hospital for non-critical or avoidable healthcare concerns. moreover, given their professional knowledge and skills, pharmacists serving in community pharmacies can also provide professional drug consultation services to locals [2] . all of this has the ultimate value of helping to reduce the number of people having to visit hospitals across the country, which, in turn, reduces the undue spread of covid-19, by mitigating unnecessary travel and overcrowding in hospitals. this is a critical measure for safeguarding the sustainability of the national health system in the successful fight against pandemics. as taiwan is fighting 'covid-19' , we use the advantages of a complete nhi information system and unite it with community pharmacists, in order to penetrate each community. the pharmaceutical practice of community pharmacists distributing masks to real-name buyers, in response to the covid-19 pandemic, is an innovative public health management program that optimizes the value-based exploitation of pharmacists, community pharmacy networks (taiwan telcom vpn), and available technology to allow for an efficient, cost-effective, reliable, and equitable population reach. this program, therefore, enables pharmacists to impact the effective management of population health by collaborating with the government and companies to ensure that there are sufficient mask supplies and well-coordinated sales to citizens across the country. given the technology-centric nature of the program, it provides assurance to pharmacists engaging in population health management initiatives of a competitive return on value (additional files 1 and 2). pharmaceutical care, health promotion, and disease prevention. in: the pharmacist guide to implementing pharmaceutical care engaging with in-need rural patient populations through public health partnerships role of the pharmacist in reducing healthcare costs: current insights effect of a virtual pharmacy review program: a population health case study taiwan plans to donate 100,000 hospital masks to us per week. washington examiner community pharmacists in taiwan at the frontline against the novel coronavirus pandemic: gatekeepers for the rationing of personal protective equipment nity-pharm acist s-taiwa n-front line-again st-novel -coron aviru s-pande mic-gatek eeper s-ratio ning# supplementary information accompanies this paper at https ://doi. org/10.1186/s1296 2-020-00239 -3. springer nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. not applicable. not applicable. not applicable. we have read the policy of journal and the authors of this study have no conflict of interest involved. key: cord-158415-qwxyuuz7 authors: chavda, amit; dsouza, jason; badgujar, sumeet; damani, ankit title: multi-stage cnn architecture for face mask detection date: 2020-09-16 journal: nan doi: nan sha: doc_id: 158415 cord_uid: qwxyuuz7 the end of 2019 witnessed the outbreak of coronavirus disease 2019 (covid-19), which has continued to be the cause of plight for millions of lives and businesses even in 2020. as the world recovers from the pandemic and plans to return to a state of normalcy, there is a wave of anxiety among all individuals, especially those who intend to resume in-person activity. studies have proved that wearing a face mask significantly reduces the risk of viral transmission as well as provides a sense of protection. however, it is not feasible to manually track the implementation of this policy. technology holds the key here. we introduce a deep learning based system that can detect instances where face masks are not used properly. our system consists of a dual-stage convolutional neural network (cnn) architecture capable of detecting masked and unmasked faces and can be integrated with pre-installed cctv cameras. this will help track safety violations, promote the use of face masks, and ensure a safe working environment. rapid advancements in the fields of science and technology have led us to a stage where we are capable of achieving feats that seemed improbable a few decades ago. technologies in fields like machine learning and artificial intelligence have made our lives easier and provide solutions to several complex problems in various areas. modern computer vision algorithms are approaching human-level performance in visual perception tasks. from image classification to video analytics, computer vision has proven to be a revolutionary aspect of modern technology. in a world battling against the novel coronavirus disease (covid-19) pandemic, technology has been a lifesaver. with the aid of technology, 'work from home' has substituted our normal work routines and has become a part of our daily lives. however, for some sectors, it is impossible to adapt to this new norm. as the pandemic slowly settles and such sectors become eager to resume in-person work, individuals are still skeptical of getting back to the office. 65% of employees are now anxious about returning to the office (woods, 2020) . multiple studies have shown that the use of face masks reduces the risk of viral transmission as well as provides a sense of protection (howard et al., 2020; verma et al., 2020) . however, it is infeasible to manually enforce such a policy on large premises and track any violations. computer vision provides a better alternative to this. using a combination of image classification, object detection, object tracking, and video analysis, we developed a robust system that can detect the presence and absence of face masks in images as well as videos. in this paper, we propose a two-stage cnn architecture, where the first stage detects human faces, while the second stage uses a lightweight image classifier to classify the faces detected in the first stage as either 'mask' or 'no mask' faces and draws bounding boxes around them along with the detected class name. this algorithm was further extended to videos as well. the detected faces are then tracked between frames using an object tracking algorithm, which makes the detections robust to the noise due to motion blur. this system can then be integrated with an image or video capturing device like a cctv camera, to track safety violations, promote the use of face masks, and ensure a safe working environment. the problem of detecting multiple masked and unmasked faces in images can be solved by a traditional object detection model. the process of object detection mainly involves localizing the objects in images and classifying them (in case of multiple objects). traditional algorithms like haar cascade (viola and jones, 2001) and hog (dalal and triggs, 2005) have proved to be effective for such tasks, but these algorithms are heavily based on feature engineering. in the era of deep learning, it is possible to train neural networks that outperform these algorithms, and do not need any extra feature engineering. convolutional neural networks (cnns) (lecun et al., 1998 ) is a key aspect in modern computer vision tasks like pattern object detection, image classification, pattern recognition tasks, etc. a cnn uses convolution kernels to convolve with the original images or feature maps to extract higher-level features, thus resulting in a very powerful tool for computer vision tasks. cnn based object detection algorithms can be classified into 2 categories: multi-stage detectors and single-stage detectors. multi-stage detectors: in a multi-stage detector, the process of detection is split into multiple steps. a two-stage detector like rcnn (girshick et al., 2014) first estimates and proposes a set of regions of interest using selective search. the cnn feature vectors are then extracted from each region independently. multiple algorithms based on regional proposal network like fast rcnn (girshick, 2015) and faster rcnn (ren et al., 2015) have achieved higher accuracy and better results than most single stage detectors. single-stage detectors: a single-stage detector performs detections in one step, directly over a dense sampling of possible locations. these algorithms skip the region proposal stage used in multi-stage detectors and are thus considered to be generally faster, at the cost of some loss of accuracy. one of the most popular single-stage algorithms, you only look once (yolo) (redmon et al., 2016) , was introduced in 2015 and achieved close to real-time performance. single shot detector (ssd) (liu et al., 2016) is another popular algorithm used for object detection, which gives excellent results. retinanet (lin et al., 2017b) , one of the best detectors, is based on feature pyramid networks (lin et al., 2017a) , and uses focal loss. as the world began implementing precautionary measures against the coronavirus, numerous implementations of face mask detection systems came forth. (ejaz et al., 2019) have performed facial recognition on masked and unmasked faces using principal component analysis (pca). however, the recognition accuracy drops to less than 70% when the recognized face is masked. (qin and li, 2020) introduced a method to identify face mask wearing conditions. they divided the facemask wearing conditions into three categories: correct face mask wearing, incorrect face mask wearing, and no face mask wearing. their system takes an image, detects and crops faces, and then uses srcnet (dong et al., 2016) to perform image super-resolution and classify them. the work by (nieto-rodríguez et al., 2015) presented a method that detects the presence or absence of a medical mask. the primary objective of this approach was to trigger an alert only for medical staff who do not wear a surgical mask, by minimizing as many false-positive face detections as possible, without missing any medical mask detections. (loey et al., 2021) proposed a model that consists of two components. the first component performs uses resnet50 (he et al., 2016) for feature extraction. the next component is a facemask classifier, based on an ensemble of classical machine learning algorithms. the authors evaluated their system and estimated that deep transfer learning approaches would achieve better results since the building, comparing, and selecting the best model among a set of classical machine learning models is a timeconsuming process. we propose a two-stage architecture for detecting masked and unmasked faces and localizing them. (larxel, 2020) ). it consists of two major stages. the first stage of our architecture includes a face detector, which localizes multiple faces in images of varying sizes and detects faces even in overlapping scenarios. the detected faces (regions of interest) extracted from this stage are then batched together and passed to the second stage of our architecture, which is a cnn based face mask classifier. the results from the second stage are decoded and the final output is the image with all the faces in the image correctly detected and classified as either masked or unmasked faces. a face detector acts as the first stage of our system. a raw rgb image is passed as the input to this stage. the face detector extracts and outputs all the faces detected in the image with their bounding box coordinates. the process of detecting faces accurately is very important for our architecture. training a highly accurate face detector needs a lot of labeled data, time, and compute resources. for these reasons, we selected a pre-trained model trained on a large dataset for easy generalization and stability in detection. three different pre-trained models were tested for this stage: dlib (sharma et al., 2016 ) -the dlib deep learning face detector offers significantly better performance than its precursor, the dlib hog based face detector. mtcnn (zhang, k. et al, 2016 ) -it uses a cascade architecture with three stages of cnn for detecting and localizing faces and facial keypoints. retinaface (deng et al., 2020) -it is a singlestage design with pixel-wise localization that uses a multi-task learning strategy to simultaneously predict face box, face score, and facial keypoints. the detection process is challenging for the model used in this stage, as it needs to detect human faces that could also be covered with masks. we selected retinaface as our stage 1 model, based on our experimentation and comparative analysis, covered in section 3.2. this block carries out the processing of the detected faces and batches them together for classification, which is carried out by stage 2. the detector from stage 1 outputs the bounding boxes for the faces. stage 2 requires the entire head of the person to accurately classify the faces as masked or unmasked. the first step involves expanding the bounding boxes in height and width by 20%, which covers the required region of interest (roi) with minimal overlap with other faces in most situations. the second step involves cropping out the expanded bounding boxes from the image to extract the roi for each detected face. the extracted faces are resized and normalized as required by stage 2. furthermore, all the faces are batched together for batch inference. the second stage of our system is a face mask classifier. this stage takes the processed roi from the intermediate processing block and classifies it as either mask or no mask. a cnn based classifier for this stage was trained, based on three different image classification models: mobilenetv2 (sandler et al., 2018) , densenet121 (huang et al., 2017) , nasnet (zoph et al., 2018) . these models have a lightweight architecture that offers high performance with low latency, which is suitable for video analysis. the output of this stage is an image (or video frame) with localized faces, classified as masked or unmasked. the three face mask classifier models were trained on our dataset. the dataset images for masked and unmasked faces were collected from image datasets available in the public domain, along with some data scraped from the internet. masked images were obtained from the real-world masked face recognition dataset (rmfrd) (wang, z. et al., 2020) and face mask detection dataset by larxel on kaggle (larxel, 2020) . rmfrd images were biased towards asian faces. thus, masked images from the larxel (kaggle) were added to the dataset to eliminate this bias. rmfrd contains images for unmasked faces as well. however, as mentioned before, they were heavily biased towards asian faces. hence, we decided not to use these images. the flickr-faces-hq (ffhq) dataset introduced by (karras et al., 2019) was used for unmasked images. our dataset also includes images of improperly worn face masks or hands covering the face, which get classified as nonmasked faces. the collected raw data was passed through stage 1 (face detector) and the intermediate processing block of the architecture. this process was carried out to ensure that the distribution and nature of training data for stage 2 match the expected input for stage 2 during the final deployment. the final dataset has 7855 images, divided into two classes: we selected an initial learning rate of 0.001. besides this, the training process included checkpointing the weights for best loss, reducing the learning rate on plateau, and early stopping. each model was trained for 50 epochs and the weights from the epoch with the lowest validation loss were selected. based on a comparative analysis of performance, covered in sections 3.1 and 3.3, the weights trained using the nasnetmobile architecture were chosen as our final trained weights. (all images used in section 3 are either selfobtained or belong to the dataset by (larxel, 2020) ) table 3 shows that densenet121 has the best f1-score. however, the other models are not significantly behind. thus, there was a need to measure other aspects of performance comparison like inference speed and model size, to select the final face mask classifier model. we tested three pre-trained models for face detection in stage 1: dlib dnn, mtcnn, retinaface. the average inference times for each of the models were calculated, based on a set of masked and unmasked images. as observed in table 4 , the retinaface model performs the best. it was observed that all three models show good results on images taken from a very short distance, having no more than two people in the image. however, it was noticed that as the number of people in the images increases, the performance of dlib becomes subpar. dlib also struggles to detect masked or covered faces. fig. 9 (a) . dlib good detection on normal faces fig. 9 (b) . dlib poor detection on faces covered by face masks mtcnn and retinaface perform better than dlib and can detect multiple faces in images. both of them can detect masked or covered faces as well. mtcnn has very high accuracy when detecting faces from the front view, but its accuracy heavily drops when detecting faces from the side view. fig. 10 (a) . mtcnn good detection on covered faces on the other hand, retinaface can detect side view faces with good accuracy as well. compared to mtcnn, retinaface significantly decreases the failure rate from 26.31% to 9.37% (the nme threshold at 10%) (deng et al., 2020, page 6). fig. 11 (a) . retinaface good detection on covered faces fig. 11 (b) . therefore, we decided to use retinaface as our face detector for stage 1. nasnetmobile and densenet121 give better results than mobilenetv2 and are almost on par with each other. from the observations in table 5 , it is evident that nasnet performs much faster than densenet121. furthermore, the model size of nasnet is lighter than densenet121 (due to a lesser number of parameters). this leads to faster loading of the model during inference. due to these factors, nasnetmobile is much more suited for real-time applications as compared to densenet121. therefore, nasnetmobile was selected as our final model for the face mask classifier. combining all the components of our architecture, we thus get a highly accurate and robust face mask detection system. retinaface was selected as our face detector in stage 1, while the nasnetmobile based model was selected as our face mask classifier in stage 2. the resultant system exhibits high performance and has the capability to detect face masks in images with multiple faces over a wide range of angles. until now, we have seen that our system shows high performance over images, overcoming most of the issues commonly faced in object detection in images. for realworld scenarios, it is beneficial to extend such a detection system to work over video feeds as well. videos have their own set of challenges like motion blur, dynamic focus, transitioning between frames, etc. in order to ensure that the detections remain stable and to avoid jitter between frames, we used the process of object tracking. we used a modified version of centroid tracking, inspired by (nascimento et al., 1999) , in order to track the detected faces between consecutive frames. this makes our detection algorithm robust to the noise and the motion blur in video streams, where the algorithm could fail to detect some objects. the detected face rois in a given frame are tracked over a predefined number of frames so that the roi coordinates for the faces are stored even if the detector fails to detect the object during the transition between frames. we selected five frames as the threshold in 30 fps video streams for discarding the cached centroids, which gave good results with the least false positive face detections in video streams. after using this method, there was a significant improvement in face mask detection in video streams. the following results show the difference in detection with and without centroid tracking: tracking was added to our algorithm, which helped improve its performance on video streams. in times of the covid-19 pandemic, with the world looking to return to normalcy and people resuming in-person work, this system can be easily deployed for automated monitoring of the use of face masks at workplaces, which will help make them safer. there are a number of aspects we plan to work on shortly:  currently, the model gives 5 fps inference speed on a cpu. in the future, we plan to improve this up to 15 fps, making our solution deployable for cctv cameras, without the need of a gpu.  the use of machine learning in the field of mobile deployment is rising rapidly. hence, we plan to port our models to their respective tensorflow lite versions.  our architecture can be made compatible with tensorflow runtime (tfrt), which will increase the inference performance on edge devices and make our models efficient on multithreading cpus.  stage 1 and stage 2 models can be easily replaced with improved models in the future, that would give better accuracy and lower latency. chollet, f., & others, howard, j., huang, a., li, z., tufekci, z., zdimal, v., van der westhuizen, h., von delft, a., price, a., face masks against covid-19: an evidence review densely connected convolutional networks a style-based generator architecture for generative adversarial networks gradient-based learning applied to document recognition feature pyramid networks for object detection focal loss for dense object detection ssd: single shot multibox detector, european conference on computer vision a hybrid deep transfer learning model with machine learning methods for face mask detection in the era of the covid-19 pandemic an algorithm for centroid-based tracking of moving objects system for medical mask detection in the operating room through facial attributes identifying facemask-wearing condition using image super-resolution with classification network to prevent covid-19 (2020), unpublished results you only look once: unified real-time object detection faster r-cnn: towards real-time object detection with region proposal networks, proceedings of the 28th international conference on neural information processing systems ieee/cvf conference on computer vision and pattern recognition farec -cnn based efficient face recognition technique using dlib visualizing the effectiveness of face masks in obstructing respiratory jets rapid object detection using a boosted cascade of simple features, computer vision and pattern recognition masked face recognition dataset and application britain faces an anxiety crisis as people return to work joint face detection and alignment using multitask cascaded convolutional networks learning transferable architectures for scalable image recognition key: cord-048483-umvrwgaw authors: van der sande, marianne; teunis, peter; sabel, rob title: professional and home-made face masks reduce exposure to respiratory infections among the general population date: 2008-07-09 journal: plos one doi: 10.1371/journal.pone.0002618 sha: doc_id: 48483 cord_uid: umvrwgaw background: governments are preparing for a potential influenza pandemic. therefore they need data to assess the possible impact of interventions. face-masks worn by the general population could be an accessible and affordable intervention, if effective when worn under routine circumstances. methodology: we assessed transmission reduction potential provided by personal respirators, surgical masks and home-made masks when worn during a variety of activities by healthy volunteers and a simulated patient. principal findings: all types of masks reduced aerosol exposure, relatively stable over time, unaffected by duration of wear or type of activity, but with a high degree of individual variation. personal respirators were more efficient than surgical masks, which were more efficient than home-made masks. regardless of mask type, children were less well protected. outward protection (mask wearing by a mechanical head) was less effective than inward protection (mask wearing by healthy volunteers). conclusions/significance: any type of general mask use is likely to decrease viral exposure and infection risk on a population level, in spite of imperfect fit and imperfect adherence, personal respirators providing most protection. masks worn by patients may not offer as great a degree of protection against aerosol transmission. with a potential influenza pandemic looming, governments need to decide how they can best use available resources to protect their people against severe illness and death, and to mitigate health and social effects for society as a whole. much research is being devoted to develop optimal strategies for the use of (pre)pandemic vaccines and of anti-virals. there are only limited data to assess the potential effectiveness of non-pharmaceutical interventions to reduce the risk of transmission, including the effect of different kinds of face-masks worn by the general public or by patients. respiratory infections such as influenza are transmitted through infectious particles, small enough to be suspended in air [1] . influenza transmission can occur via large droplets, which only remain suspended in the air for a short period of time thus requiring close contact, and can occur via small airborne particles, which remain suspended in air for considerable longer periods of time, and can thus be transmitted over larger distances [2] . furthermore, some transmission may occur via direct contact with respiratory secretions such as on hands and surfaces [2] . interruption of transmission may allow containment of major outbreaks, like pandemic influenza. opportunistic data collected during the sars epidemic in asia suggested that population-wide use of face masks may significantly decrease transmission of not only sars but also influenza [3, 4, 5, 6, 7] . as part of pandemic preparedness, many are contemplating the contribution wide-spread use of masks could have [8, 9] . as this has major implications for resource allocation and for communication, there is great need for data to guide such decisions and make them evidence-based. protective effects of face masks have been studied extensively, but usually this involved personal respirators for professionals under idealized conditions, because of specific applications, for instance in military or occupational uses, involving protection of specifically trained personnel. this is different from deployment of masks in the general population during an outbreak of an infectious disease, where anyone may encounter the infectious micro-organism, implying much greater heterogeneity, in training levels (experience and understanding), goodness of fit of a mask, and activities interfering with mask use and thus reducing potential reduction of transmission. the protective effect of masks is created through a combined effect of the transmission blocking potential of the material, the fit and related air leakage of the mask, and the degree of adherence to proper wearing and disposal of masks. personal respirators such as those worn by staff attending tb patients, are used primarily to protect the wearer, and are designed to fit to the face with as tight a seal as possible. their efficiency is graded on the degree of protection the material offers, assuming a perfect fit and optimal compliance. in contrast, surgical masks, as commonly worn in the operating theatre, are primarily used to protect the environment from the respiratory droplets produced by the wearer. with these masks, facial fit is much looser. the fit of home made masks, which could be e.g. made of a tea cloth or other comparable material available in the home, is likely to be even looser. thus personal respirators confer a higher degree of protection than surgical masks, and these are again likely to give a higher degree of protection than home-made masks. in professional situations, ample time might be available prior to use to ensure a perfect fit and to give extensive counselling on adherence, but it is unlikely this will apply to the general population in case of a pandemic. it is possible that the discomfort in wearing associated with a certain type of masks will lead to reduced adherence and thus to a loss in overall protectiveness [10, 11] . indeed a review among health care workers could not determine whether personal respirators conferred better protection for the health care workers than surgical masks [10] . to investigate the levels of protection, and their variation, wearing of face masks could convey to untrained subjects we designed a study in which healthy volunteers would be wearing different types of professional and home-made masks during a selection of activities, in different conditions (inward protection). we also assessed the protection different types of masks could convey when worn by a simulated infectious patient (outward protection). resulting quantitative descriptions of distributions of protection factors may be used for assessing the importance of mask use in respiratory disease transmission. three different experiments were undertaken to assess 1) shortterm protection for different types of masks worn during 10-15 minutes by the same volunteer following a standardized protocol, 2) long-term protection of a specific mask worn continuously by a volunteer for 3 hours during regular activities, and 3) effectiveness of different types of mask in preventing outgoing transmission by a simulated infectious subject. inward protection was defined as the effect of mask wearing to protect the wearer from the environment; outward protection was defined as the effect of a mask on protecting the environment from the generation of airborne particles by a patient (or in this case a mechanical head). in the first short-term experiment, 28 healthy adult volunteers were recruited, as well as 11 children between 5 and 11 years of age. each volunteer followed the same protocol wearing a filtering facepiece against particles (ffp)-2 mask 1872vh (3m); which is the european equivalent of a n95 mask, a surgical mask (1818 tie-onh, 3m; with a filtering efficiency of around 95% for particles of sizes between 0.02 mm to 1 mm; http://jada.ada.org/ cgi/content/full/136/7/877) and a home-made mask (made of td cerise multih teacloths, blokker). in this standard protocol, the volunteer was asked to perform five successive tasks in a fixed sequence 1.5 minute of duration each: no activity-sit still, nod head (''yes''), shake head (''no''), read aloud a standard text, stationary walk. in this sequence of activities, the respiratory rate is gradually increased. throughout this exercise, the concentration of particles was measured on both sides of the mask through a receptor fixed on the facial and on the external side. these were connected to a portable counter of all free floating particles in the air via an electrostatic particle classifier and counter, the portacounth. the portacounth can register particles floating in the air with sizes between 0.02 mm to 1 mm, covering most of the size range of infectious respiratory aerosols [12] . total inward leakage (til) percentage was calculated by dividing the concentrations on the outside and on the inside (til = (concentration inside/concentration outside)6100); the calculated quantitative protection factor was the inverse of the leakage (pf = (til/ 100) 21 ). to ensure small numbers of particles produced by the volunteers would not affect measurements, we checked that at least 10,000 particles per cm 3 particles of this size class (0.02 mm-1 mm) were present in the room which were produced by a number of lit candles. (figure 1 ) in the second long-term experiment, 22 volunteers, all adults, 10 men, 12 women, were divided into 3 groups. each group wore a single type of mask for a period of three hours, being either a ffp2 mask (4 males, 4 females), a surgical mask (3 males, 4 females) or a home-made mask (3 males, 4 females), similar to the masks used in the short-term experiment described above. at the beginning and end of each three-hour period, full series of measurements were taken using the standardised protocol as described for the short-term experiment, and during the three hour period while wearing the masks, participants reported back at regular intervals for a short measurement during rest (absence of activity). for the remainder of the period, participants carried on with their usual daily activities. during regular activities in between measurements, the probes of the masks were plugged which did not involve dislodging of the masks. in the final experiment, we assessed the effectiveness of different types of masks in reducing outgoing transmission from an infectious subject shedding aerosolised particles. this was simulated by fitting the different types of masks to an artificial test head, which was connected to pc-driven respirator (bacouh lama amp, modelref 1520307). breathing frequency was varied to mimic different respiratory rates (15, 25 and 40/minute). only expiration was simulated; twice for each mask at each respiratory rate. the breathing flow was defined as (respiratory rate/minute x volume per breath (2 litres)) resulting in a breathing flow of 30, 50 and 80 litres per minute, which correlates with light (walking), medium (marching with backpack) and strenuous (running) activities [13] . concentrations of particles were measured as described above by a tsi portacount respirator fit tester, model 8020, measuring outward protection, rather than inward protection. all volunteers received written information prior to the experiments and gave oral informed consent. for the children also a parent gave oral informed consent, and a parent remained present during the experiments. the dutch central committee on research involving human subjects (ccmo) informed us in writing that this project did not need to be assessed by an ethics committee. protection factors (pf) calculated from measurements of particle concentration by portacounth devices were reported as the ratio of particle concentrations outside and inside the mask. this is a similar concept to the fit factor as used by the us occupational safety and health administration (http://www.osha.gov/pls/ oshaweb/owadisp.show_document). therefore, a higher pf is better and pf = 1 means complete absence of protection. for statistical analysis, the following transformation was used: the inverse of the pf (1/pf) can be interpreted as a probability (that any particle succeeds in moving through the barrier the mask provides). the logit transformation is a standard transformation to transform the probability scale (0,1) to the real axis (-infinity, +infinity) to allow standard regression techniques (including anova) to test the effects of co-variables (mask type, age class, sex, activity, duration of use) on transformed pfs in a linear model, using the statistical application r (version 2.5.0). the p-values are based on testing the ratio of mean squares for a factor (like 'mask') and the mean square of errors (random fluctuations), assuming that ratio is f-distributed. whenever the p-value (the probability of a greater value of the tested ratio) is greater than 0.05, the ratio is considered significantly different from 1 ( = indifference) at the 95% level. all masks provided protection against transmission by reducing exposure during all types of activities, for both children and adults (table 1) . within each category of masks, the degree of protection varied by age category and to a lesser extent by activity. we observed no difference between men and women. surgical masks provided about twice as much protection as home made masks, the difference a bit more marked among adults. ffp2 masks provided adults with about 50 times as much protection as home made masks, and 25 times as much protection as surgical masks. the increase in protection for children was less marked, about 10 times as much protection by ffp2 versus home-made masks and 6 times as much protection as surgical masks. in these short term experiments, adjusting for covariates, face mask type had a strongly significant independent effect on protection (p,0.001). children were significantly less protected than adults (p,0.001). there was no significant impact of activity on protection. as in the short term experiment, mask type was a strong determinant of protection (table 2 ). protection factors for each type of mask were similar to the protection factors measured in the short term experiments for adults. there was considerable variability between volunteers. the median protection factors measured over a 3 hour period increased for those wearing homemade masks, decreased for those wearing ffp2 masks, and did not show a consistent pattern for those wearing a surgical mask (figure 2 ), but overall protection factors calculated per type of mask were stable over time, and did not change statistically significant with prolonged wearing. overall, protection factors were relatively stable over time for each individual (anova p = 0.4). males and females did not have significantly different protection factors (anova p = 0.9). as in the short term experiment, protection conferred by surgical masks was higher than protection given by a home-made mask, and protection provided by a ffp2 masks was again markedly higher than protection provided by a surgical mask. as in the short term experiment, more strenuous activities (reading and walking) tended to increase the protection of the home-made mask and to a lesser extent of the surgical mask, and decreased the protection by the ffp2 mask, but there was no overall significant effect of type of activity on pf (anova p = 0.1). outward protection experiment in a final experiment, retention of particles expelled inside the masks was studied. here again, mask type was strongly correlated with (transformed) protection factors. protection factors for all type of masks were considerably lower than those observed for inward protection. the home-made masks only provided marginal protection, while protection offered by a surgical mask and an ffp2 mask did not differ ( figure 3) . the simulated breathing frequency did not significantly affect the measured protection factors. adjusting for covariates, mask type and particle concentration, but not flow rate, were significant factors for protection in the reverse flow experiment. in our experiments, the main determinant of the magnitude of protection factors measured by masks was the type of mask, which can be seen as a proxy for potential reduction in infectious disease transmission. the duration of wear and the type of activity did not have a significant impact on exposure reduction. thus, the expected superior protection conferred by a professional ffp2 mask compared to a surgical mask or a home-made mask was maintained when these ffp2 masks were worn by healthy lay people in spite of the increased risk of a poor fit and significant behavioural leakage. children were significantly less protected from exposure than adults, which might be related to an inferior fit of the masks on their smaller faces. although we observed a high degree of individual variability in the degree of protection conferred as reflected in the wide interquartile ranges of the measured pfs, no systematic difference was found between men and women, suggesting a poorer fit only has a noticeable impact on protection when the mismatch between face and mask is considerable. all types of masks provided a much higher degree of exposure protection against inward transmission of particles, then in preventing outward transmission by a mechanical head as a proxy for an infected patient exposing the environment. data from professional users suggest a decrease in protection over time due to a reduction in fibre charges [13] . in our data, this effect was not significantly present, although a tendency towards reduced protection over time was seen for the ffp2 masks. also, our study showed a high degree of individual variation in exposure protection. this is important as it reflects the presence of many different sources of variation, behavioural as well as anatomical, which can also be expected to be present if the general population would be requested to wear face masks in case of a pandemic. furthermore, we do not know from these experiments whether reduced exposure has a linear or non-linear relationship to the reduction of infection risk. although this could imply that individual subjects may not always be optimally protected, from a public health point of view, any type of general face mask usage can still decrease viral transmission. also, it is important not to focus on a single intervention in case of a pandemic, but to integrate all effective interventions for optimal protection. surprisingly, the protection conferred by each of the masks appeared stable over time and was not dependent on activity. this suggests that leakage associated with suboptimal fit and compliance was stable over time. the tendency towards improved protection of the poorer fitting masks with increased activities such as reading, might be attributable to reduced leakage when breathing through the mouth rather than the nose, which could give some overpressure and thus reduce inward leakage. we had assumed that compliance would decrease during the three hours of continuous wearing, in particular with more strenuous activities. indeed, among professionals like cullers, there have been some anecdotal reports that ffp3 masks were associated with poorer compliance than ffp2 masks in wearing. where a reduction in protection was found with the ffp2 mask, the reverse was seen for the home-made mask. it is possible that the experimental situation, sufficient motivation to endure a relatively limited time of discomfort, and the absence of physically challenging activities, has provided more stable protection than might be found in reallife situations. however, overall these experiments show that significant protection against influenza transmission upon exposure can be conveyed also for lay people, including children, in spite of imperfect fit and imperfect adherence. it is also clear that home-made masks such as teacloths may still confer a significant degree of protection, albeit less strong than surgical masks or ffp2 masks. home made masks however would not suffer from limited supplies, and would not need additional resources to provide at large scale. home made masks, and to a lesser degree surgical masks, are unlikely to confer much protection against transmission of small particles like droplet nuclei, but as the reproduction number of influenza may not be very high [14] a small reduction in transmissibility of the virus may be sufficient for reducing the reproduction number to a value smaller than 1 and thus extinguishing the epidemic [15] . greater reduction in transmissibility may be achieved if transmission is predominantly carried by larger droplets. in a typical human cough half of the droplets may be small (,10 mm), but these comprise only a small fraction (2.5*10 26 ) of the expelled volume [12] . smaller droplets may however more easily penetrate the smaller bronchi and be more effective in transmission [1] . a more detailed analysis of aerosol and droplet inoculation and infectivity may provide better insight into the impact of either transmission mode on population spread. the difference in measured protection against inward and outward protection is remarkable, and cannot be explained from the available data as we only measured the overall effect. a differential effect on the amount of leakage seems most plausible. at the same time, we cannot exclude that wearing of face masks, even ffp2 or surgical masks by patients might still significantly reduce transmission. however, the observed limited particle retention in our experiments may still be an overestimate of protection, as it may for instance be challenging to enforce adherence to mask wearing by a patient who is short of breath. wearing of masks by caregivers might be more feasible and more effective, in particular where additional preventive measures are in place as well for caregivers. furthermore, we should bear in mind that this is an experimental study, with relatively small numbers of volunteers, which limits the generalisability of some of our findings. e.g., for masks to have any impact during an actual pandemic, people may need to be wearing masks during several weeks with many shorter or longer mask-free periods. furthermore, the pfs may be an over-or underestimation of the actual protection conferred. and although our simulated patient varied its breathing frequency, we have not assessed the impact of e.g. coughing or sneezing on outward transmission through a mask. a recent analysis of the 1918 epidemic, noted that cities where strict interventions were implemented early on to prevent transmission, were overall worse-off than cities where some degree of transmission occurred early on [16] . given the need for the population to acquire sufficient natural immunity over time, it can not be excluded that the amount of protection conferred by home made masks might sufficiently reduce viral exposure to impact on transmission during the early waves, while allowing people enough exposure to start mounting an efficient immune response. further field studies are needed to assess acceptability and effectiveness of masks worn by people from the general population. also, experimental data are needed to develop dose-response models which may improve understanding of determinants of transmission. a cost-effectiveness analysis might give further insights in the relative benefits of home made masks. review of aerosol transmission of influenza a virus transmission of influenza a in human beings sars transmission, risk factors and prevention in hong kong respiratory infections during sars outbreak risk of respiratory infections in health care workers: lesson on infection control emerge from the sars outbreak risk factors for sars among persons without known contact with sars patients factors influencing the wearing of facemasks to prevent the severe acute respiratory syndrome among adult chinese in hong kong nonpharmaceutical interventions for pandemic influenza world health organisation writing group (2006) non-pharmaceutical interventions for pandemic influenza, national and community measures protecting health care workers from sars and other respiratory pathogens: a review of the infection control literature modelling control strategies of respiratory pathogens towards understanding the risk of secondary airborne infection: emission of respirable pathogens do n95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks? transmissibility of 1918 pandemic influenza mathematical epidemiology of infectious diseases. model building, analysis and interpretation the effect of public health measures on the 1918 influenza pandemic in us cities we thank nicole brienen for preparatory literature searches, rob schimmel and tineke albers for support in conducting the experiments, and all volunteers. volunteers in figure 1 gave written permission for reproduction. key: cord-104138-qagyaegp authors: magee, michelle; lewis, courtney; noffs, gustavo; reece, hannah; chan, jess c. s.; zaga, charissa j.; paynter, camille; birchall, olga; azocar, sandra rojas; ediriweera, angela; caverlé, marja w.; schultz, benjamin g.; vogel, adam p. title: effects of face masks on acoustic analysis and speech perception: implications for peri-pandemic protocols date: 2020-10-08 journal: biorxiv doi: 10.1101/2020.10.06.327452 sha: doc_id: 104138 cord_uid: qagyaegp wearing face masks (alongside physical distancing) provides some protection against infection from covid-19. face masks can also change how we communicate and subsequently affect speech signal quality. here we investigated how three face mask types (n95, surgical and cloth) affect acoustic analysis of speech and perceived intelligibility in healthy subjects. we compared speech produced with and without the different masks on acoustic measures of timing, frequency, perturbation and power spectral density. speech clarity was also examined using a standardized intelligibility tool by blinded raters. mask type impacted the power distribution in frequencies above 3khz for both the n95 and surgical masks. measures of timing and spectral tilt also differed across mask conditions. cepstral and harmonics to noise ratios remained flat across mask type. no differences were observed across conditions for word or sentence intelligibility measures. our data show that face masks change the speech signal, but some specific acoustic features remain largely unaffected (e.g., measures of voice quality) irrespective of mask type. outcomes have bearing on how future speech studies are run when personal protective equipment is worn. face masks (alongside physical distancing) provide some protection against infection from coronavirus disease (chu et al., 2020) . their use in public spaces and healthcare settings is either recommended or mandatory in many jurisdictions internationally. in the united states, the center for disease control (cdc, 2020) recommends mask use to minimize droplet dispersion and aerosolization of the virus (bahl et al., 2020) . clinical trials and healthcare settings continue to assess speech production, which generates respiratory droplets while unrestricted exposure increases the likelihood of disease contraction (stadnytskyi et al., 2020) . risk of transmission increases through behaviors common in many speech assessment tasks including continuous and loud speech (asadi et al., 2019) . at the same time, acknowledgement of the necessity of personal protective equipment to minimize virus transmission has increased internationally (asadi et al., 2019; stadnytskyi et al., 2020; zaga et al., 2020) . masks, however, alter the speech signal with downstream effects on intelligibility of a speaker. the use of personal protective equipment poses some unique challenges for speech assessment. we evaluated the impact wearing a mask has on acoustic output and speech perception. we examined how different face mask types (surgical, cloth and n95), in combination with microphone location variations (headset vs. tabletop), affect speech recordings and intelligibility. four subjects, aged 29.0 ± 5.8 years, range 23-38; 2 males: 2 females, were included in the study. all speakers were english speaking with no dysphonia, cognitive or neurological impairments. one male and female had english as their second language. the speech battery was elicited by trained staff and consisted of sustaining an open vowel /aː/ for approximately six seconds reproduced ten times and reading a phonetically balanced text, the grandfather passage (van riper, 1963) , reproduced five times. the speech battery was repeated under four conditions in a randomized order: 1) no mask; 2) standard surgical mask (regulated under 21 cfr 878.4040); 3) cloth mask (2-layered cotton); and 4) n95 mask (disposable mask made from electrostatic non-woven polypropylene fiber containing a filtration layer). subjects were instructed to speak in a natural manner at a comfortable pitch and pace. speech samples were recorded using two standardized methods: 1) using a head-mounted cardioid condenser microphone (akg520, harman international, united states) positioned 2 inches from the corner of the subject's mouth (minimum sensitivity of -43db, near flat frequency response) and coupled with a quad-capture usb 2.0 audio interface (roland corporation, shizuoka, japan) connected to a laptop computer; and 2) using a blue yeti (blue microphones, united states) tabletop microphone (sensitivity 4.5mv/pa) connected to a laptop computer. the microphone was positioned 5 ft. from the subject to simulate physical distancing measures. standardization of the recording environment was achieved by recording in the absence of traffic, electrical, appliance, or other background noise. all recordings were sampled at 44.1 khz with 32-bit quantization. speech intelligibility was evaluated using the assessment of intelligibility of dysarthria speech (assids) (yorkston and beukelman, 1984) . for each condition subjects read aloud a randomized list of single words (one and two syllables in length) and sentences (5 to 28 syllables in length). two blinded raters transcribed assids words and sentences, with the percentage of correct items calculated for each condition. audio files were screened for deviations and synchronized between microphones to ensure uniformity of length. acoustic analysis of sustained vowel and reading tasks were performed using praat software (boersma, 2002) . two groups of speech features were analyzed, one to describe responsiveness to speech and silence, and another to determine agreement between measurements taken by different microphone conditions. the speech spectrum was used to describe the impact of mask type on the complex voice waveform. the interaction between intensity and frequency was characterized using the power spectral density (psd, db/khz relative 2x10 -5 pa) in the longterm average spectrum on the reading task. psd provides information on how "each frequency" contributes to the total sound power. frequency bands were fixed at 1khz. psd was averaged across subjects for each mask condition and compared between masks not subjects. center-of-gravity (cog, in hz) was calculated from the power spectrum to inform frequency responsiveness of the conditions. cog is the mean power-weighted frequency, i.e. the frequency that divides the power spectrum in equal halves above and below cog. the intensity of background noise (floor) was determined as equal to the average intensity during the quietest three seconds of each files (i.e., in the absence of vocalization). floor intensity was subtracted from the average intensity (during vocalization) for each task (vowel and reading) to determine the speech intensity prominence per mask condition. features of interest included cepstral peak prominence smoothed (cpps), harmonic-to-noise ratio (hnr), local jitter and shimmer for the sustained vowel, and average and standard deviation of pause length for the reading task. fundamental frequency was calculated through autocorrelation within a restricted range (70hz -250hz for males, 100hz -300hz for females) (vogel et al., 2009 ). the analysis window was 43ms and 30ms respectively, and window shift fixed at 10ms. the maximum number of formants was set at 5 with a maximum of 5500hz for formant detection. all other parameters were maintained at default software settings. the detection of silence-speech and speech-silence transitions was done using an energy threshold on the time domain (rosen et al., 2010; vogel et al., 2017) . the threshold was set to 65% of the 95 th percentile, with minimum silence length set to 20ms and minimum speech length to 30ms. to examine differences of each acoustic parameter under each mask condition (no mask, surgical, n95, and cloth), a linear mixed-effects model analysis using restricted maximum likelihood estimation was applied. mask type was modeled as a fixed factor, and subject and order of mask as a random factor. bonferroni corrected post hoc pairwise comparisons were conducted to determine differences in mask type (surgical, n95, and cloth) compared to no mask. to investigate power spectral density, the interaction effect between mask and frequency band was investigated. where the interaction was significant, planned comparisons were made for each 1khz frequency band to determine differences between masks types compared to no mask. spss was used for all statistical analyses (ibm spss version 26.0). intelligibility varied between the speakers and across mask conditions. on average, intelligibility remained above 92% for all mask conditions, irrespective of single words (figure 1a frequency bands were collapsed into 1khz slices to explore differences in psd between mask type. there was a mask × 1khz frequency band interaction effect (f27,755=2.50, p=0.006). post hoc comparisons showed power (db/hz 2 ) was significantly lower between 3-10 khz for n95 mask and 5-10khz for surgical and cloth masks when compared to no mask on recordings made using the head-mounted microphone (figure 2a) . no significant differences were observed between mask conditions on recordings made using the tabletop microphone (f27,757=1.41, p=0.082; figure 2b ). -insert figure 2 about hereshowed that recordings produced with the n95 mask increased percentage of pauses (p=0.023) (table 1) . spectral tilt was lower in recordings produced with the surgical (p=0.016) and n95 masks (p=0.001). for recordings produced with the tabletop microphone, there was a significant effect of mask type for percentage of pauses (f3,7.87=8.17, p=0.008), and spectral tilt (f3,8.39=15.43, p=0.001) ( table 1) . post hoc comparisons revealed that the n95 and cloth masks yielded higher percentage of pauses (n95 p=0.022; cloth p=0.029) no mask. as with the head-mounted microphone, recordings produced with the tabletop microphone yielded lower spectral tilt values with both the surgical (p=0.006) and n95 masks (p=0.002). no significant differences were observed in acoustic parameters extracted from the sustained vowel recorded using either the headmounted or tabletop microphone. -insert table 1 about herethe type of mask affected the speech signal. we observed significant differences in acoustic power distribution across relevant frequency bands for speech in all three mask conditions compared to no mask. the differences were not observed in frequencies below 3khz. differences in signal for higher frequencies led to altered acoustic outcomes including spectral tilt. the masks however did not significantly influence listener-perceived intelligibility or acoustic measures of perturbation (e.g., nhr, cpps). measures of speech rate were lower for n95 and surgical masks, possibly as speakers compensate when wearing masks to improve intelligibility. it is also possible that speech timing differences were related to how speech boundaries are identified in the analysis scripts (i.e., our timing analysis relied on identification of phoneme/word boundaries via intensity thresholds). intelligibility scores varied between raters and between mask condition. intelligibility remained above 92% for words and sentences. anecdotally, it can be difficult to understand people when they wear a mask (goldin et al., 2020) . our small dataset suggests mask type does not systematically impact intelligibility in controlled environments. our recordings were made with high-quality microphones in quiet environments. raters listened to samples in ideal listening conditions away from distractions and background noise but without visual aid (lips and jaw movement) for all mask conditions. in loud environments, communication can be challenging with multiple distractors, background noise, and a lower signal-to-noise ratios (snr). noise in ecological situations may further decrease speech intelligibility, when complementary visual cues blocked by use of face masks play a role in communication. it is clear that face masks change the acoustic speech signal, but some specific perceptual features remain largely unaffected (e.g., acoustic measures of voice quality) irrespective of mask type. these results have implications for clinical assessments and speech research where ppe is required. it is easy to assume that subjects in a speech study will simply remove ppe during assessments; however, subjects and researchers may be reluctant to do so if it leads to potential exposure to airborne viruses. in longitudinal studies with data collection before, during, and after pandemics requiring ppe, researchers should consider how to mitigate against changes to protocols that affect speech (see figure 3 ) (redenlab, 2020) . mean power spectra density displayed between 1-10khz based on mask type. shaded areas represent the standard error of mean. *p≤0.05 no mask vs mask type at each frequency bin. red stars denote significant differences between no mask and n95, blue stars denote significant differences between no mask and surgical masks while orange stars denote significant differences between no mask and n95. *disclaimer: please be advised that nothing completely eliminates bacteria or viruses and the guidelines contained in this document are measures attempting to limit the spread of a virus. further, these guidelines do not supersede medical practitioner recommendations or the covid-19 safety policies implemented by your business or institution. it is your responsibility to follow the recommendations and safety policies applicable to your business or institution. to reduce risk, it is recommended assessors wear masks throughout assessments, the microphone's metal surfaces are sanitized between subjects, and all windscreens are washed at the end of each use. aerosol emission and superemission during human speech increase with voice loudness face coverings and mask to minimise droplet dispersion and aerosolisation: a video case study use of masks to help slow the spread of covid-19 physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis how do medical masks degrade speech reception? guidance on minimizing risk to patients and staff during speech recordings automatic method of pause measurement for normal and dysarthric speech the airborne lifetime of small speech droplets and their potential importance in sars-cov-2 transmission standardization of pitch-range settings in voice acoustic analysis motor speech signature of behavioral variant frontotemporal dementia: refining the phenotype assessment of intelligibility of dysarthric speech speech-language pathology guidance for tracheostomy during the covid-19 pandemic: an international multidisciplinary perspective key: cord-025744-pynqwj5t authors: van der linden, clifton; savoie, justin title: does collective interest or self-interest motivate mask usage as a preventive measure against covid-19? date: 2020-05-14 journal: nan doi: 10.1017/s0008423920000475 sha: doc_id: 25744 cord_uid: pynqwj5t the revised guidance on masks from public health officials has been one of the most significant covid-19 policy reversals to date. statements made at the outset of the pandemic, including those from the world health organization (who), the united states surgeon general, and the chief public health officer of canada, all actively discouraged asymptomatic members of the general public from wearing masks. however, on april 3, 2020, the united states center for disease control and prevention (cdc) issued new recommendations that called for nonmedical masks, such as cloth face coverings, to be worn in public settings where other social distancing measures are difficult to maintain (adams, 2020). canadian public health officials quickly followed with their own guidance for wearing nonmedical masks or face coverings when out in public; however, they have stressed that doing so is optional for asymptomatic persons and should be seen as a complement to existing precautionary measures such as physical distancing and hand hygiene, particularly in cases where physical distancing may not be feasible (public health agency of canada, 2020). emphasis was placed on nonmedical masks serving not to protect the wearer, but rather others who come within close proximity of the wearer. echoing her public statements on the matter, canada's chief public health officer tweeted that “[w]earing a non-medical mask in public settings has not been proven to add any protection to the person wearing it, but it can be an additional way to prevent spread from an infected person to others” (tam, 2020). the revised guidance on masks from public health officials has been one of the most significant covid-19 policy reversals to date. statements made at the outset of the pandemic, including those from the world health organization (who), the united states surgeon general, and the chief public health officer of canada, all actively discouraged asymptomatic members of the general public from wearing masks. however, on april 3, 2020, the united states center for disease control and prevention (cdc) issued new recommendations that called for nonmedical masks, such as cloth face coverings, to be worn in public settings where other social distancing measures are difficult to maintain (adams, 2020) . canadian public health officials quickly followed with their own guidance for wearing nonmedical masks or face coverings when out in public; however, they have stressed that doing so is optional for asymptomatic persons and should be seen as a complement to existing precautionary measures such as physical distancing and hand hygiene, particularly in cases where physical distancing may not be feasible (public health agency of canada, 2020). emphasis was placed on nonmedical masks serving not to protect the wearer, but rather others who come within close proximity of the wearer. echoing her public statements on the matter, canada's chief public health officer tweeted that "[w]earing a non-medical mask in public settings has not been proven to add any protection to the person wearing it, but it can be an additional way to prevent spread from an infected person to others" (tam, 2020) . findings from a multiwave study conducted by vox pop labs indicate that the prevalence of mask usage among canadians rose significantly upon the issuance of revised guidance on the matter from u.s. and canadian public health officials and has since continued its upward orientation (see figure 1 ). given the discursive framing of wearing masks as a common good rather than an individual benefit, we examine the extent to which the rise in mask usage is motivated by collective interest as opposed to self-interest. drawing on recent survey data, we find that the decision to wear a mask is in part a function of collective interest. specifically, the increased propensity among canadians to wear masks is to a limited extent driven by concern for the welfare of others as opposed to oneself. however, the effect of collective interest on mask usage is rather modest by comparison with regional, gender, and partisan dynamics. we find no evidence to indicate that priming self-interest has an effect on mask usage by individuals in the general population. mask usage serves as a useful example of how collective action operates in the context of covid-19. according to olson (1965) , individuals in a group behave as rational egoists and would thus be disinclined to wear a mask if does not offer them additional protection from personally contracting covid-19. even though wearing a mask may indirectly protect the wearer in that increased mask usage by the general public may reduce overall transmission of covid-19, olson's logic asserts that individuals would instead free ride based on the expectation that other group members would adopt mask usage. this view is challenged by theorists who argue that rational self-interest alone fails to appropriately capture the empirically observable dynamics of collective action (mansbridge, 1990) . ostrom (2000, p. 142) argues that a substantial proportion of the population is composed of so-called "conditional cooperators" who are generally willing to act in the collective interest as long as they see a sufficient degree of reciprocation by others. conditional cooperators would be willing to don a mask to protect others so long as they observe a sufficient number of people within their group doing the same. respondents were asked, "what changes, if any, have you made to your normal routine in response to the covid-19 pandemic?" "wearing a mask" was among the response options. respondents to the first three waves of the study were provided with the response options in a multiselect format and asked to select all that applied. subsequent waves transitioned to a binary scale in which respondents were asked to explicitly respond "yes" or "no" to each response option. to ensure that the revised format did not affect self-reported behavioural changes, respondents were randomly assigned either the multiselect or the binary scale for the fourth and fifth waves. as the differences in self-reported behaviours were not statistically significant, the binary scale was adopted for all respondents from the sixth wave onward. we employed data from the fourth wave of a rolling sample survey, which was fielded between april 3 and april 7, 2020 and completed by 2,194 respondents who currently reside in canada. the sample was drawn from the vox pop labs online panel (n ∼ 650,000) as part of its covid-19 monitor initiative, a 24-wave weekly survey on public opinion in relation to the covid-19 pandemic. the sample was pre-stratified according to age, sex, education, partisanship, and region. we tested whether canadians exhibit a higher propensity to wear masks in response to appeals to a sense of collective interest or self-interest. to do so, we designed a survey experiment in which respondents were randomly presented with one of three texts: a control, a collective interest treatment, and a self-interest treatment. the control text read as follows: going forward, how likely are you to voluntarily (i.e., without being required to do so) wear a mask or any sort of protective face covering out in public as a preventative measure against covid-19? the collective interest treatment included the following preamble prior to the control text: some countries have started asking their citizens to cover their faces when in public in order to avoid potentially transmitting the virus to others with whom they come into contact. the suggestion is that, by wearing a mask, you may be protecting others from infection. the self-interest treatment included the following preamble prior to the control text: some countries have started asking their citizens to cover their faces when in public in order to avoid potentially contracting the virus from others with whom they come into contact. the suggestion is that, by wearing a mask, you may be protecting yourself from infection. survey respondents were asked to indicate their response on an 11-point scale ranging from 0 to 10, where 0 meant "no more likely" and 10 meant "much more likely." the mean of this continuous variable serves as our outcome variable. we used linear regression to model the effects of each treatment on the likeliness to wear a mask going forward. the results of the study are summarized in table 1 . model 1 compares each of the two treatments (collective interest and self-interest) against the control group. the coefficients represent the respective averages of the control and each of the treatment groups on the 11-point response scale. in model 2, we include a series of sociodemographic regressors in order to allow for substantive comparison of the effect size of the treatments with those of other independent variables. model 1 indicates that the self-interested treatment is not statistically significant vis-à-vis the baseline control. suggesting that canadians should wear masks as a protective measure against contracting covid-19 does not appear to increase the probability that they will do so. however, we do observe a small but statistically significant effect when it comes to the collective interest treatment. when compared with the control group, the collective interest treatment increases the average respondent's inclination to wear a mask by 0.505 points on the 11-point continuous scale. though a five-percentage-point increase on an 11-point scale is modest, it is non-negligible. the finding is statistically significant when the control is set as the base category, but also when the self-interested treatment acts as the baseline (see the appendix). the results of model 1 demonstrate that canadians are more willing to wear masks as a measure to protect others from covid-19 rather than themselves. figure 2 displays the results of an ordered logit regression so as to examine the note: *p < 0.1; **p < 0.05; ***p < 0.01. distribution of responses across the 11-point scale for the control group and both of the treatments. we observe that the differences in the collective treatment and selfinterest treatments cluster at the ends of the scale, whereas there are similar proportions of respondents in the centre in every case. this suggests that collective interest primers reduce opposition and increase support for wearing masks at the extremes. model 2 adds additional categorical independent variables including sex, age group, region, highest level of educational attainment, and vote choice in the 2019 canadian federal election. the results observed in model 1 are robust to the inclusion of additional regressors included in model 2, both in terms of significance and effect size. though model 2 also serves in principle to support the argument that individuals can act in the collective interest under certain conditions, it behooves us to note both the significance and effect size of several of the included sociodemographic control variables. first, women are more likely than men to wear masks. the effect size is larger than that of the collective interest treatment. second, living in british columbia is associated with a higher likelihood of wearing a mask, while living in quebec is associated with a substantively lower likelihood of doing so. compared to the (alphabetically determined) baseline of alberta, the effect size for quebec is −1.041, which is the largest effect size of any of the variables included in the model and a difference of 1.665 points from bc on the 11-point response scale. further study is required to interrogate this difference, but these differences may be related to the mixed and controversial messaging around the use of masks from premier françois legault and national director of public health horracio arruda (boisvert, 2020; cardinal, 2020) . third, partisan differences have an effect on the adoption of masks insofar as we observe a substantive and significant effect on mask uptake by those who voted for the liberal party and new democratic party in the 2019 canadian federal election. liberal and ndp supporters are more likely to wear masks, whereas the result for conservative party, green party, and bloc québécois voters is not significant. there is likely an ideological dimension at play within these findings, with left-leaning canadians being particularly more receptive to the idea of wearing masks. although in substantive terms the effect size is relatively modest, the findings of this study demonstrate that canadians are significantly more likely to adopt maskwearing in public when doing so is seen as a means to protect others from covid-19 rather than as a means to protect themselves. indeed, at the time of writing, the dominant framing around the utility of wearing masks in public was to prevent the potential transmission of covid-19, rather than as means to prevent oneself from contracting the virus. the survey results suggest that this approach is more likely to induce compliance with directives to wear masks than either a generic appeal or one that speaks to self-interest. although this study focuses exclusively on the adoption of masks, its findings are potentially instructive in terms of framing broader public health advice in relation to covid-19 in such a manner as to elicit compliance. the findings also lend credence to theories of collective action that are critical of the idea of rational selfinterest as the ubiquitous and exclusive motivation of individuals within a group. table 1 reports the effect of the self-interested and collective treatment vis-à-vis the control baseline but does not explicitly compare both treatments. as a robustness check, table a1 contemplates the selfinterested treatment as the baseline. the collective interest treatment remains statistically significant. recommendation regarding the use of cloth face coverings, especially in areas of significant community-based transmission notre erreur sur les masques qu'attend quebec pour imposer le masque self-interest in political life the logic of collective action: public goods and the theory of groups collective action and the evolution of social norms considerations in the use of homemade masks to protect against covid-19 5/9 wearing a non-medical mask in public settings has not been proven to add any protection to the person wearing it, but it can be an additional way to prevent spread from an infected person to others. #protectdontinfect #covid19 #layerupcovid key: cord-000166-36bfeoqv authors: tracht, samantha m.; del valle, sara y.; hyman, james m. title: mathematical modeling of the effectiveness of facemasks in reducing the spread of novel influenza a (h1n1) date: 2010-02-10 journal: plos one doi: 10.1371/journal.pone.0009018 sha: doc_id: 166 cord_uid: 36bfeoqv on june 11, 2009, the world health organization declared the outbreak of novel influenza a (h1n1) a pandemic. with limited supplies of antivirals and vaccines, countries and individuals are looking at other ways to reduce the spread of pandemic (h1n1) 2009, particularly options that are cost effective and relatively easy to implement. recent experiences with the 2003 sars and 2009 h1n1 epidemics have shown that people are willing to wear facemasks to protect themselves against infection; however, little research has been done to quantify the impact of using facemasks in reducing the spread of disease. we construct and analyze a mathematical model for a population in which some people wear facemasks during the pandemic and quantify impact of these masks on the spread of influenza. to estimate the parameter values used for the effectiveness of facemasks, we used available data from studies on n95 respirators and surgical facemasks. the results show that if n95 respirators are only 20% effective in reducing susceptibility and infectivity, only 10% of the population would have to wear them to reduce the number of influenza a (h1n1) cases by 20%. we can conclude from our model that, if worn properly, facemasks are an effective intervention strategy in reducing the spread of pandemic (h1n1) 2009. novel influenza a (h1n1) (hereafter referred to as pandemic (h1n1) 2009 in keeping with the world health organization (who) nomenclature) is a new flu virus of swine, avian, and human origin that was first identified in mid-april 2009 in mexico and the united states [1] . the virus soon spread to the rest of the world and on june 11, 2009 the who declared novel influenza a (h1n1) a pandemic. the virus continues to spread, with most countries reporting cases of pandemic (h1n1) 2009 [1] . even though the who's declaration of a phase six pandemic alert level does not explicitly refer to the severity of the disease, as many people contracting the virus recover without medical treatment, the number of deaths continues to rise [1] . the rapid spread of influenza, due to its short incubation period and lack of strainspecific vaccine, pose a challenge to the implementation of effective mitigation strategies during the expected reemergence of pandemic (h1n1) 2009 in the fall/winter flu season. every year approximately 36,000 people die from seasonal influenza or flurelated causes in the u.s. [2] . however, the number of casualties may increase with a new and more virulent strains of influenza, such as the pandemic (h1n1) 2009. the emergence of an unexpected or new strain of influenza means there are no prepared vaccines and the existing antivirals may be ineffective in combating the spread of infection. vaccination is typically the first line of defense against influenza viruses [3] . the entire vaccine production process takes at least six months to complete [4] and although a pandemic (h1n1) 2009 vaccine became available in the u.s. in october 2009, there are severe shortages in the amount of vaccines available. another concern is that the currently circulating h1n1 strain could mutate, making the vaccine ineffective or less effective. in the recent pandemic (h1n1) 2009 outbreak, non-pharmaceutical interventions such as school closings and thermal screenings at airports were implemented to slow the spread of disease [5, 6] . other common non-pharmecuetical interventions include quarantine, isolation, travel restrictions, closing of public places, fear-based self quarantine, and cancellation of events. these interventions all have economic costs to individuals and society related to lost work, increased school absenteeism, and decreased business revenues. another non-pharmaceutical option is the use of facemasks. in the 2003 sars outbreak many individuals used facemasks to reduce their chances of contracting infection. in hong kong 76% of the residents reported using masks during the 2003 sars epidemic [7] . even though individuals have taken upon themselves to wear facemasks during disease outbreaks, little research has been done to quantify the impact of the use of facemasks during an epidemic. mathematical models of the spread of infectious disease can be useful in assessing the impact of facemasks on reducing the spread of a disease, specifically pandemic (h1n1) 2009. pandemic (h1n1) 2009 spreads through person-to-person contact, airborne particles, coughing and sneezing, and by fomites [1] , therefore, the use of facemasks is a logical line of defense. the centers for disease control and prevention (cdc) have interim recommendations on the use of facemasks and respirators for the current pandemic (h1n1) 2009 virus. the cdc defines the term facemask as a disposable mask cleared by the u.s. food and drug administration (fda) for use as a medical device, such as surgical masks. surgical masks are designed to help stop droplets from being spread by the person wearing the mask, not to protect against breathing in very small particle aerosols that may contain viruses [8] . we will use of the term 'respirator' for an n95 or higher filtering facepiece respirator certified by the cdc/national institute for occupational safety and health (niosh); a respirator is designed to protect the person wearing the mask against breathing in very small particles that may contain viruses [8] . the cdc states that the effectiveness of the use of facemasks and respirators in various settings is unknown and do not generally recommend the use of facemasks or respirators in home or community settings nor in non-medical occupational settings [8] . in certain circumstances the cdc recommends the use of masks for individuals who are at high risk of infection and cannot avoid situations with potential exposure to the disease [8] . there have been a handful of studies that have analyzed the effectiveness of facemasks against nanoparticles in the size range of viruses using manikin-based protocol in which the masks were sealed on the manikin's face so that no leakage would occur [9] [10] [11] . all three studies show similar results in penetration percentage for the n95 respirator. the high fit n95 respirator had penetration percentages from about 0.5% to 2.5% at 30 l/ min and from about 0.5% to 5% at 85 l/min [9] [10] [11] . the low fit n95 respirator had penetration percentages from about 1.5% to 3.5% at 30 l/min and from about 1.5% to 6% at 85 l/min [9] [10] [11] . the surgical masks tested in balazy et al.'s [10] study show a much greater penetration percentage. at 30 l/min one model of surgical mask (sm1) allowed 20-80% of particles to penetrate the mask, while another model (sm2) allowed 2-15% [10] . at 85 l/min sm1 allowed penetration of 30-85% of particles while sm2 allowed 5-21% [10] . the n95 respirator in a sealed manikin test seems to be fairly effective against nanoparticles, almost holding up to its 95% certification. the surgical masks are not as effective, allowing a much greater percentage of particles to pass through to the wearer even when sealed tightly to a manikin. unfortunately, this type of testing does not provide an accurate estimate of the level of protection for everyday use of a mask by a person. while these studies provide data on the actual protection of masks against nanoparticles in a perfect setting, it does not take into consideration that a mask will not be completely sealed on an individual nor will it fit perfectly. furthermore, one must consider that an individual will not always be wearing the mask, for example, a mask will be taken off to eat and sleep, or possibly because it becomes uncomfortable to wear. lee et al. [12] performed a study on n95 respirators and surgical masks using human subjects. the challenge aerosol used was nacl, with particles in the size range of bacteria and viruses (.04-1.3mm). they tested four models of n95 respirators: 1) high protection level, 2) medium protection level, 3) exhalation valve, and 4) exhalation without valve and three models of surgical masks: 1) high protection level, 2) medium protection level, and 3) low protection level. the results from the study showed that the lowest protection offered from n95 respirators is when particles are in the size range of 0.08-0.2mm and for surgical masks when particles are in the size range of 0.04-0.32mm. the size range of influenza virus is in the range of 0.08-0.12mm, which falls into both masks most penetrating particle size range. the n95 respirator was found to be 21.5% effective and the surgical mask was 2.4% effective in protecting against nanoparticles. the n95 respirator provides approximately nine times greater protection than a surgical mask and is clearly a better option in protecting against infection. a university of michigan school of public health study led by dr. allison aiello [13] is evaluating the effectiveness of handwashing and facemasks in preventing influenza from spreading. the study, called m-flu, conducted a randomized cluster intervention trial among students living in dorm housing. the students were randomly separated into two intervention groups, one wearing masks and practicing hand hygiene, one just wearing masks, and also in a control group. the study was carried out over the 2006-2007 influenza season, which was a mild season. the study found that facemasks and hand hygiene were correlated with a 35-51% reduction in influenza-like illness [13] . there are many factors that influence people's willingness to wear a mask. in a study by tang and wong [14] a total of 1,329 . the arrows that connect the boxed groups represent the movement of individuals from one group to an adjacent one. nonmask wearing susceptible individuals (s) can either become exposed (e) or susceptible wearing a mask (s m ). non-mask wearing exposed individuals (e) can either become infectious non-mask wearing (i) or mask wearing exposed (e m ). non-mask wearing infectious individuals (i) can either recover (r), die (d), or become infectious wearing a mask (i m ). mask wearing susceptible individual (s m ) can either become an exposed mask wearer (e m ) or a non-mask wearing susceptible (s). mask wearing exposed individuals (e m ) can either become an infectious mask wearer (i m ) or a non-mask wearing exposed individual (e). a mask wearing infectious individual (i m ) can either recover (r), die (d), or stop wearing the mask while they are still infectious (i). doi:10.1371/journal.pone.0009018.g001 adult chinese residing in hong kong were surveyed on their use of facemasks during the 2003 sars epidemic. overall 61.2% of the respondents reported the consistent use of facemasks to prevent contracting the disease. the study found that women in the age group 50-59 and married respondents were more likely to wear facemasks, suggesting that the aesthetics of wearing a facemask may be a concern. also, the study found that individuals who had a university education or earned more than us$5,000 per month were more likely to wear a mask. tang and wong also showed that perceived susceptibility, cues to action, and perceived benefits, were significant predictors in whether or not an individual consistently wore a mask. following the approached developed in [15] , the population is divided into two subgroups: a mask wearing group (subscript m) and a non-mask wearing group. people move back and forth between the mask and non-mask groups based on the number of individuals infected with pandemic (h1n1) 2009. individuals in each activity group are characterized by their epidemiological status: susceptible, denoted by s and s m , exposed, denoted by e and e m (i.e., people who are infected but not yet fully contagious), and infectious individuals, i and i m . definitions of the eight epidemiological classes are summarized in table 1 and the transfers are shown diagrammatically in figure 1 . because we are evaluating the effectiveness of masks in a single influenza period, we use a closed system with no migration in or out, and births and natural deaths are not included in the model. as seen in figure 1 , the transfer rates of people from the exposed classes, e and e m , to the infectious classes, i and i m , are ve and ve m . infectious individuals can move to group d, at rate mi and mi m , when they die from infection or to group r, at rate di and di m , upon recovery. the mean times in the infectious classes, i and i m , are 1=(dzm). hence, the infectious fraction d=(mzd) recovers and the infectious fraction m=(mzd) dies as a consequence of this disease. we assume that there is homogeneous mixing between groups and that contact activity levels remain normal throughout the epidemic. we define t 0 as the beginning of the epidemic. movement of individuals between mask and non-mask groups depends upon the number of pandemic (h1n1) 2009 cases in the population. a specified percentage of the population starts wearing masks as the number of infected people increases. we define q sm s, q em e, and q im i to be the transfer rates from the s, e, and i classes to the s m , e m , and i m classes, respectively, similarly q s s m , q e e m , and q i i m are the transfer rates from the s m , e m , and i m classes to the s, e, and i classes, respectively. the rate coefficients are modeled by step-functions of the number of infectious individuals: for i = s, e, i, s m , e m , and i m . here the parameters a and b are positive constants that determine the rate of movement and t is the number of pandemic (h1n1) 2009 cases that determines when masks are implemented. for i = s, e, and i, b i is set at 0.1 or 10% of the population. using the transfer diagrams in figure 1 we obtain the following system of differential equations: here l (non-mask group) and l m (mask group) are the forces of infection and ls and l m s m are the transfer rates from the susceptible classes, s and s m , to the exposed classes, e and e m . the infection rates, l and l m , incorporate the probability of transmission per contact, b, the reduced infectiousness due to incubation, a, the reduced number of contacts because of symptomatic infection, h, and 1{g j , (j = s or i), which accounts for the effectiveness of the mask in reducing either susceptibility (g s ) or infectivity (g i ). the transmissibility, b, is defined as the effective reproduction number < con for n95 respirators. notice that < con decreases as a higher percentage of people wear masks as well as when masks are more effective. < con is greatly reduced when 50% of the population wears masks and masks are 50% effective. doi:10.1371/journal.pone.0009018.t005 susceptibility of the population multiplied by the infectivity of the disease multiplied by the average number of contacts an individual has per day. the definitions of the parameters are summarized in table 2 . the forces of infection for the non-mask group and mask group are shown by: where r~n{(1{h)(izi m ) and n is the total population the effective reproduction number, < eff , is the average number of secondary cases produced by a typical infectious individual effective reproduction number, < con , for surgical masks. notice that < con decreases as a higher percentage of people wear masks as well as when masks are more effective. however, < con is not greatly reduced even when 50% of the population wears masks and masks are 50% effective. doi:10.1371/journal.pone.0009018.t006 during the infectious period [16, 17] . the effectiveness of intervention strategies are often measured by their ability to reduce the spread of a disease in a given population. in an epidemic model the magnitude of the effective reproduction number, < eff , determines whether or not an epidemic occurs and its severity [15] . when < eff w1, the number of infections grow and an epidemic occurs, however when < eff v1, the number of infections does not increase and there is no epidemic outbreak [15] . without any interventions the model has an initial effective reproduction number (uncontrolled) < unc given by: this < unc is the product of the average number of people infected per unit time b and the weighted sum of the average infectious period 1=(mzd) plus the average incubation period 1=v. the 'next-generation operator' approach [17] is used to find an expression for the effective reproduction number (controlled) < con for our epidemic model when masks are used as an intervention strategy. the computation is done by linearizing the system of equations (2) around the disease-free equilibrium (dfe). the dfe has e, e m , i, and i m equal to zero with s 0 , s 0 m , and r 0 positive. since there is no immunity from previous infection or vaccination r 0 is also equal to zero. the resulting fourdimensional linearized system is of the form dx dt~( the effective reproduction number < con is the largest eigenvalue of the matrix fv {1 [17] . hence < con is the only non-zero eigenvalue of the matrix fv {1 and is given by the expression: figure 2 with respirators is also seen here: as the masks effectiveness is higher the number of cumulative cases decreases and the number of cases also decreases if a higher percentage of people wear masks. however, the difference in the number of cumulative cases is not nearly as large when surgical masks are worn; this is due to their lower effectiveness. doi:10.1371/journal.pone.0009018.g003 where c 1~qem zv, c 2~qe zv, c 3~qim zdzm, c 4~qi zdzm, and s~s 0 zs 0 m . we use equations 4 and 7 to define the effective reproduction number for the model as: where t is the threshold number of infected individuals at which masks start to be used. the epidemiology of pandemic (h1n1) 2009 is not accurately known since it continues to spread across the world. the parameter values shown in table 2 were chosen based on the best available data. the incubation period for pandemic (h1n1) 2009 has been reported to be 2-10 days with a mean of 6 days [18] . the mean time in the exposed classes e and e m corresponding to the incubation period has been assumed to be 6 days, making the transfer rate to the infectious classes, i and i m , constant at v = 1/6. the infectious period is believed to be between four and seven days, with an average of five days [19, 20] . thus, the baseline value for the recovery rate is constant at d = 1/5. the fatality rate of the pandemic (h1n1) 2009 is thought to be in the range of 0.3%-1.5%, with a mean of 0.46% [21] [22] [23] . the case fatality rate for our model is m=(dzm), setting this equal to 0.0046 results in m~0:0046d=0:9954~0:001. the current estimates on the transmission of pandemic (h1n1) 2009 are that one infected person may typically infects one to two people [24] [25] [26] . the transmissibility, b, is the product of the susceptibility of the population, the infectivity of the disease, and the number of contacts an individual has in a day [27, 28] . the susceptibility of the population is set to one, as it is believed few people are immune to pandemic (h1n1) 2009, and the number of contacts an individual has per day is assumed to be 16 [29] . the infectivity is found by 1:8=(16( a v z h mzd )), so that r 0 = 1.8 in a completely susceptible population and the infectivity is .0141. so b~0:23 gives the transmission rate, the fraction of contacts per day that is sufficient for the transmission of pandemic (h1n1) 2009. the baseline population size n for the model is set at one million people and all are initially in the susceptible class s. the initial infected fraction, i/n, is set at 0.00001 so that when n = 1000000, i = 10. the model scales linearly so that the initial population size n and the initial number of infected individuals i are both scaled up or down by the same factor. we assume that individuals will start wearing masks after 100 people are infected, figure 4 . sensitivity to < unc < unc . the number of cumulative cases is very sensitive to the value of the uncontrolled effective reproduction number (< unc ). higher values of < unc result in a larger number of cumulative cases. a large difference in the number of cases is seen when the < unc is equal to 1.83 and when < unc is equal to 1.7; for such a slight difference in < unc the difference in the number of cases is quite large. doi:10.1371/journal.pone.0009018.g004 (6) once there is enough number of cases in a community to convince people to start wearing masks. we analyzed the impact of masks when 10%, 25%, and 50% of the population wear them. using the studies published on the effectiveness of masks we determined the baseline values for the effectiveness of n95 respirators to be g s = 0.2 and g i = 0.5 and for the surgical masks g s = 0.02 and g i = 0.05 [12] . the effectiveness of masks in decreasing the infectivity of a sick individual is greater because the mask contains the virus particles, preventing them from becoming airborne, and therefore preventing the contamination of surrounding surfaces as well as people [30] . although it is possible that some sick individuals may change their behavior due to the symptoms [15] , we assume that sick individuals will not change their behavior and continue to have the same number of daily contacts as a healthy individual. therefore, we set the baseline value for the reduced number of contacts due to illness h at 1, as people usually do not greatly alter their daily behavior during the incubation period. individuals in the exposed classes, e and e m , are thought to be 50% less infectious due to incubation than those in the infected classes, i and i m , so we set a = 0.5 [19, 31] . we analyzed two scenarios: one in which the n95 respirator is worn and one in which surgical masks are worn; for both types of masks we considered three different variations in mask effectiveness. each case is evaluated with 10%, 25%, and 50% of susceptible and exposed individuals wearing masks, while in each case the fraction of infectious individuals wearing masks is slightly larger. when 10%, 25%, and 50% of susceptible and exposed individuals are wearing masks the fraction of infectious individuals wearing masks is 30%, 40%, and 50%, respectively. all simulations assume that in a population of one million there are initially 10 infected individuals reported and everyone else is susceptible. mask start being used when there have been 100 reported cases of pandemic (h1n1) 2009. the numerical results for the percentage of pandemic (h1n1) 2009 cases are shown in table 3 for the n95 respirator and in table 4 for surgical masks. the effective reproduction numbers for each case are shown in table 5 for n95 respirators and in table 6 for surgical masks. the cumulative number of pandemic (h1n1) 2009 cases can be seen graphically for the varying mask effectiveness and the different fractions of individuals wearing masks in figure 2 and in figure 3 for n95 respirators and surgical masks, respectively. table 3 and table 4 show that when masks are not used, then the total percentage of the population who will be infected is 74.61% in a population of 1 million people. with the implementation of n95 respirators table 3 exhibits a reduction in the cumulative number of cases of almost 200,000, or a 19% decrease, when 10% of the population wears masks and they are 20% effective. table 5 shows the implementation of the n95 respirators' impact on the effective reproduction number < con ; it is reduced from 1.83 to 1.66 when masks are 20% effective in reducing both susceptibility and infectivity and 10% of the population is wearing masks. when effectiveness is increased to 50% < con is reduced even further to 1.4. as the fraction of the population wearing n95 respirators increases, < con is reduced table 4 shows that surgical masks do not have as large of an impact in reducing the cumulative number of cases as does the n95 respirator. table 6 displays the effective reproduction number < con when surgical masks are implemented. the lowest value surgical masks reduce < con to is 1.77. in figure 2 the effectiveness of the n95 respirator in reducing the spread of pandemic (h1n1) 2009 is significant. as the percentage of the population wearing masks increases the number of cumulative cases decreases and when the mask effectiveness is greater, the number of cases is also greatly reduced. the impact of surgical masks is not as large as seen graphically in figure 3 , the reduction in the cumulative number of cases is relatively small compared to that of the n95 respirator. if mask effectiveness is 5% and 50% of the population wears surgical masks the reduction in the number of cumulative cases is 6%. even though the parameter values were estimated from epidemiological data, there is still some uncertainty in their values. since pandemic (h1n1) 2009 is a new virus, there is a wide range of estimated values for the parameters. in our model we chose the averages for our baseline parameters, here we look at a range of parameters and how changing a specific one effects the outcome of the model. this sensitivity analysis examines the effects of changes in the reproduction number (< unc ), mask effectiveness (g s and g i ), index cases (i=n), fraction of population wearing masks (q i ), number of initially infected at which masks are implemented (t), as well as the effect of which epidemiological group wears masks (s or i). unless otherwise stated the other parameters are fixed at their baselines values found in table 2 . effective reproduction number. the effective reproduction number < unc determines the average number of secondary cases resulting from one typical infectious individual during the infectious period without the implementation of facemasks. since there is a delay in the implementation of facemasks the initial growth of the epidemic is affected by < unc . the estimates of < unc for pandemic (h1n1) 2009 vary widely, the common range is assumed to be between 1.2 and 2.2. as the value of < unc increases the number of pandemic (h1n1) 2009 cases increases significantly as shown graphically in figure 4 . mask effectiveness. the effectiveness of the mask greatly affects the number of cumulative cases. the higher the effectiveness the fewer number of cases (shown in the results section). the effectiveness of the masks not only depends upon the type of mask and quality but also proper usage. index cases. the number of initially infected individuals can have a major impact on the size of the epidemic. in figure 5 we vary the number of initially infected individuals in the population. fraction of population wearing masks. we consider variations in the percentage of the population that wears masks. we look at the effect of 10%, 25% and 50% of the population wearing masks. the model shows that the higher the percentage of the population wearing masks the fewer the number of cumulative cases, this is shown in figure 6 . implementation of masks. the epidemic is sensitive to the delay in the implementation of masks as seen in figure 7 . we look at the cumulative number of pandemic (h1n1) 2009 cases for the n95 respirator when 10% of the population is wearing masks. figure 7 shows that the earlier masks are implemented, the bigger the reduction in the cumulative number of cases. who wears masks. the model is sensitive to who wears masks. here we look at the effect if only infected individuals wear masks and if only susceptible and exposed individuals would wear masks. figure 8 shows that it is important for both infected, as well as susceptible and exposed individuals, to wear masks. the standard mitigation strategies used for influenza viruses are vaccines and antivirals. however, in the case of a novel virus these may not be readily available and other mitigation strategies will be needed. as seen during the 2003 sars outbreak and the current pandemic (h1n1) 2009 people are willing to wear facemasks to reduce the spread of disease. we used a mathematical model to examine the possible impact of n95 respirators and surgical masks on reducing the spread of pandemic (h1n1) 2009. when modeled with a low mask effectiveness and a small fraction of the population wearing masks, the implementation of facemasks still has a relatively large impact on the size of the pandemic (h1n1) 2009. the numerical simulation results in the results section show that without any interventions, we predict that a large percentage of the population will be infected with pandemic (h1n1) 2009 influenza strain. this result is not surprising as the population is 100% susceptible and the effective reproduction number < unc is 1.83, which is higher than that of typical seasonal influenza. in reality, the r unc may be lower due to heterogeneous mixing patterns, pre-existing immunity, and other interventions in place. with 10% of the population wearing n95 respirators with effectiveness at 20% in reducing both susceptibility and infectivity there is a 19% reduction in the cumulative number of cases. with the same mask effectiveness but 25% of the population wearing n95 respirators, the total number of pandemic (h1n1) 2009 cases is reduced by almost 30% and with 50% of the population wearing masks, it results in over a 36% reduction in the number of cases. the effectiveness of surgical masks is low, therefore the impact of wearing them during an epidemic is not significant. even at 50% effectiveness in reducing both susceptibility and infectivity and with 50% of the population wearing surgical masks only a 6% reduction in the number of cumulative cases is seen. the sooner an epidemic is recognized and masks are implemented, the bigger the reduction in the number of cases will be. as seen in the results section the epidemic is sensitive to the delay in implementing masks. the difference in the total number of pandemic (h1n1) 2009 cases when masks are implemented at 100 infected individuals and 1,000 infected individuals is over 7%. the implementation of neither n95 respirators nor surgical masks lowered the effective reproduction number < unc below one. however, n95 respirators greatly decreased < unc , in some scenarios very close to one. while facemasks will not stop the pandemic (h1n1) 2009, they could greatly reduce its severity and allow for more time to develop effective vaccines and antivirals. there are currently more trials being conducted on the effectiveness of surgical masks and n95 respirators [32] , which will allow us to refine the assumptions made in the model. however, it must be noted that in order for masks to be effective they must be: (1) available, (2) affordable, (3) worn properly, (4) replaced or sanitized daily, and (5) n95 respirators should be fit-tested. only 10% of the population would have to wear masks in order to reduce the percentage of cases by 20%. facemasks are inexpensive, relatively easy to implement, and would not cause a large economic burden to society. masks are a powerful tool and can be used by countries with limited supplies of antiviral drugs and vaccines. in addition, economically feasible preventative global mitigations will benefit the world as a whole. we can conclude from our model that n95 respirators if worn properly are an effective intervention strategy in reducing the spread of the pandemic (h1n1) 2009. figure 8 . sensitivity to who wears masks. in order to achieve the greatest possible reduction in the cumulative number of cases both infectious individuals and susceptible and exposed individuals should wear masks. if only infectious individuals wear masks the number of cases is not significantly reduced. doi:10.1371/journal.pone.0009018.g008 center for disease control and prevention website. 2. (2009) questions and answers regarding estimating deaths from influenza in the united states mitigation strategies for pandemic influenza in the united states how do they make influenza vaccine? 5. (2009) more airports seek thermal screening for flu school closings jump to over 400 over swine flu fears respiratory infections during sars outbreak, hong kong. emerging infectious diseases 11 interim recommendations for facemask and respirator use to reduce novel influenza a (h1n1) virus transmission manikin-based performance evaluation of n95 filtering-facepiece respirators challenged with nanoparticles do n95 respirators provide 95 percent protection level against airborne viruses, and how adequate are surgical masks? filter performance of n99 and n95 facepiece respirators against viruses and ultrafine particles respiratory performance offered by n95 respirators and surgical masks: human subject evaluation with nacl aerosol representing bacterial and viral particle size range mask use reduces seasonal influenza-like illness in the community setting factors influencing the wearing of facemasks to prevent the severe acute respiratory syndrome among adult chinese in hong kong effects of behavioral changes in a smallpox attack model the mathematics of infectious diseases reproduction numbers and subthreshold endemic equilibria for compartmental models of disease transmission interim guidance for clinicians on identifying and caring for patients with swine-origin influenza a (h1n1) virus infection local and systemic cytokine response during experimental human influenza a virus infection. relation to symptom formation and host defense duration of influenza a virus shedding in hospitalized patients and implications for infection control influenza a (h1n1)-update 44. world health organization website: global alert and response pandemic potential of a strain of influenza a (h1n1): early findings the effect of public health measures on the 1918 influenza pandemic in u.s. cities outbreak of swine-origin influenza a (h1n1) virus infection -mexico update: infections with a swine-origin influenza a virus -united states and other countries, april. center for disease control and prevention website episims los angeles case study transmission dynamics of the great influenza pandemic of 1918 in geneva, switzerland: aassessing the effects of hypothetical interventions mixing patterns between age groups in social networks a schlieren optical study of the human cough with and without wearing masks for aerosol control quantifying the routes of transmission for pandemic influenza surgical mask vs n95 respirator for preventing influenza among health care workers transmission potential of the new influenza a (h1n1) virus and its age-specificity in japan pandemic (h1n1) 2009. world health organization website: global alert and response hhs pandemic influenza plan. us department of health and human services website we would like to thank carlos castillo-chavez and gerardo chowell for their helpful comments. conceived and designed the experiments: smt sdv jmh. performed the experiments: smt. analyzed the data: smt sdv jmh. contributed reagents/materials/analysis tools: smt sdv jmh. wrote the paper: smt sdv jmh. key: cord-017140-k4lzwfge authors: andersen, bjørg marit title: protection of upper respiratory tract, mouth and eyes date: 2018-09-25 journal: prevention and control of infections in hospitals doi: 10.1007/978-3-319-99921-0_13 sha: doc_id: 17140 cord_uid: k4lzwfge pathogenic bacteria and viruses may invade via upper and lower respiratory tract and via eye mucosa. when an infected person coughs or sneezes heavily, small, invisible droplets with the infective agent may reach a good distance from the source. by using the right form of protection at the right time, infection and disease are prevented. the present chapter is focused on the protection against airborne infections. • contact with infectious patients, according to the isolation procedures. • when performing sterile procedures. • when in close contact with patients who are in an infection-prone situation, for example, during operations and patients with compromised immune system. • contact with wounds and tissues and/or in direct contact with sterile equipment used invasively or when present during ongoing invasive procedures. • self-protection against splashes/aerosol of biological material (trachea suction, vomiting, cough, diarrhoea, secretions, diathermy, etc.). • patient with suspected contagious respiratory infection-during transport, examination, treatment, etc.; use a face mask-also on the patient-to protect others and the environment from contamination. • when cleaning and disinfecting contaminated rooms like isolates and when handling used patient equipment/machinery with organic material (ventilator, cpap, etc.) and used patient textiles, infectious waste and bio-organic waste. • during work with plumbing and construction with increased risk of soil, splatter, aerosols or dust particle clouds, such as working with instrument channels in the patient rooms and surgical departments, ventilation systems, sinks, sewer, water leakages with fungal growth, etc. • caps should always be used when putting on masks to protect hair. hospital management should ensure an infection control programme that informs all employees about the standards of hygiene and infection control at the hospital. furthermore, to provide resources to the acquisition, stock reserves and logistics of adequate personal protective equipment (ppe), also for emergency situations [5, 8] . department management is responsible for training, use and control of face masks, respirators and eye protection and that the equipment and written guidelines are available [5] . each user is responsible for the proper use of ppe at the right time and in accordance with current guidelines. the following are available in all relevant departments/posts: • guidelines-written-for the use of a face mask/respirator/eye protection. • surgical masks: put a date on the box when it opens. only surgical masks of good quality are used. other face masks-thin and of poor quality-fastened behind ears should never be used in the healthcare system because of no protective effect. • respiratory protection-p3 mask-with and without valve, separately packed. put the date on the box. • surgical face masks with visor. • face shield. • goggles. single-use or multi-use goggles that can be disinfected and autoclaved between uses. • cap/hood/head or neck protection (phantom hood, operation caps)-always when using masks. • access to good hand hygiene-hand disinfectant-at the place where the ppe is used. when airways, mouth and eyes are protected, the hair and head should also be covered simultaneously. many people have long hair that can come in contact with the patient, bedding or equipment which can lead to transmission of infection to other patients, in addition to themselves becoming a carrier. nb! always use cap/hood/head protection when using surgical mask or other ppe. these may be single-use or multi-use. single-use devices are thrown away immediately after use. surgical mask with visor may protect against direct spills and splashes. a complete face shield protects against direct splashing. the multi-use equipment (check with infection control personnel) is soaked in chloramine 5% 1 h (or household chlorine) before laundered in soapy water or washed in the instrument washing machine by more than 85 °c or autoclaved. it is stated on the package if the goggles may be autoclaved. quality-controlled surgical face mask is disposable and used for: putting on • disinfect your hands. • put on the cap-thin operating hood-that collects all hair. pull it over your ears. • disinfect your hands. • take the mask from the surgical mask box, and take only one mask. the box must have the date of opening. all boxes that have been exposed to infection should be discarded afterwards. • put the face mask over your mouth and nose with a drawstring at the back of the head/top and the other on the neck. • adapt the face mask that has metal string over the nose-so that it fits tightly and comfortably around the mouth and nose. • replace the face mask between each patient/situation/procedure or after 2-6 h if you are with the same patient or when it is wet on the inside. avoid changing the mask if this can cause more contamination and risk, for instance, during surgery. surgical masks are usually not changed during surgery. • never go with a face mask under the chin or around your neck! it is usually heavily contaminated by mouth and nose secretion after use and by splatter from the patient. • perform hand hygiene. • first take hold of the string in the neck and loose this while you bend forward. the lower part of the mask then falls away from the face. then gently loosen the string on the head, and gently put the mask into the waste container. • face masks should not come in contact with hair or clothes. • dispose in regular waste during normal use or infectious waste if infection. • perform hand hygiene afterwards. • grip the cap back and carefully pull it off while bending forward, and put it into the waste container. • perform hand hygiene afterwards. filtering half masks and guidelines for use of respiratory protection should be available at relevant clinical departments. p3 mask is used by the surgical team and during all sterile procedures: in the case of operative treatment of patients with special types of airborne infection such as tuberculosis, etc., see above. if there is an open breathing valve on the p3 mask, surgical mask must be used outside the p3 mask. p3 mask with covered breathing valve can be used instead. p2 mask or surgical mask is put on the patient with defined or suspected airborne infection (e.g. tuberculosis, varicella, etc.) during transport, and stay outside isolation units. putting on • disinfect your hands. • put on the cap-thin operating hood-that collects all hair. pull it over your ears. • disinfect your hands. • take the p3 mask from the surgical mask box, and take only one mask. each mask is usually separately wrapped. the box must have the date of opening. all boxes that have been exposed for infection should be discarded afterwards. • put the respirator over your mouth and nose with a drawstring at the back of the head/top and the other on the neck. the cap hood underneath makes it easier to put the mask on-it does not slip. • adapt the face mask that has metal string over the nose-so that it fits tightly and comfortably around the mouth and nose. • test tightness by blowing vigorously or breathing in; leaks are then sensed on the sides of the mask. • change the p3 mask after 3-6 h or longer or if it is wet on the inside. • avoid change if this may lead to risk of infection. take it off very carefully, as the p3 mask may be used in a serious contagious situation and may be contaminated on the outside. • disinfect your hands. • grasp the band/string posteriorly, bend forwards and remove the mask gently without coming into contact with the clothing, skin or hair. do not touch the mask directly. • loosen the band in the neck first so that the mask falls forwardly away from the face. then carefully loosen the band on the head. • put the mask gently into infectious waste bin. • perform hand hygiene. • grip the cap back, bend forwards and carefully pull it off without coming into contact with the skin or clothes and place the mask in infectious waste bin. • perform hand hygiene afterwards. eye protection is always used when there is a risk of splashing of human biological material to the eyes and for protection against highly infectious diseases. in the event of a risk of severe airborne disease, wear tight protective goggles where you can use regular glasses on the inside. multi-use goggles may be reused after 1 h of treatment in 5% chloramine bath (or household chlorine 10,000 ppm) with subsequent soapy water and rinsing. putting on • perform hand hygiene. • put on the cap-thin operating hood-that collects all hair. pull it over your ears. • in case of severe, dangerous infection, put goggles on outside of a phantom cap that is sitting outside a surgery cap and a p3 mask; see strict isolation. • disinfect your hands. • goggles are retrieved from the box, usually separately wrapped. the box must have the date of opening. all boxes that have been exposed for infection should be discarded afterwards. • put the glasses or shield over the eyes with a rubber band on the occiput. the operation hood under prevents it from slipping. • adapt the goggles-so that it fits tightly and comfortably all around the eyes. • they can be used as long as they are needed. take it off very carefully, as the goggles/face shields may be contaminated on the outside. • disinfect your hands. • grasp the band/string posteriorly, bend forwards and remove the goggles/face shield gently without coming into contact with the clothing, skin or hair. do not touch the devices directly. • if multi-use: put it carefully into the container with 5% chloramine. if single-use: put it into the infectious waste bin. • perform hand hygiene. • grip the cap back, bend forwards and carefully pull it off without coming into contact with the skin or clothes, and place it in infectious waste bin. • perform hand hygiene afterwards. "the employer must ensure that protective equipment made available to the worker, meets requirements of regulations on construction, design and manufacture of personal protective equipment" [5] . this should be in accordance with official regulations for the use of personal protective equipment [5, 9] . already in roman times, it was pointed out by doctor galen that "when many get sick and die at once, we must look for a common cause, the air we breathe". [1, [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] . most cases of these serious, life-threatening diseases may be transmitted via air, droplets and re-aerosols, from patients, carriers and the environment. an adult breathes in at rest 5-8 litres of air per minute, at medium heavy work 30-40 l and at great exertion 70-100 litres of air per minute. in small rooms and with a high air contamination of infectious agents, some contaminants will be drawn into the respiratory tract. it has been demonstrated that when a person coughs or sneezes, drops, droplets and droplet nuclei from the mouth and nose may reach up to 9 m from the source [2] . surgical masks and respiratory protection (filter masks) are defined as "equipment that can help prevent the spread of microbes from one person to another" [2, 3] . the difference between surgical mask and respiratory protection is that surgical masks primarily protect the patient and sterile area/equipment against mouth and nose secretion from healthcare professionals, while respiratory protection protects healthcare workers and others from airborne infections from nearby sources of infection [3-5, 14, 23] . however, surgical masks are not approved as protection against airborne infections: [5, 14, 24, 25] "harmful microorganisms (bacteria, viruses, fungi) or components of microorganisms (e.g. endotoxins) may occur in air, either in dust, smoke or aerosols, or even finer distributed as droplet nuclei where all liquid has dried in. surgical masks only protects against splash and drop, not against airborne infection. therefore, to protect against airborne infection, wear respiratory protection. in most situations, a filtering half mask will provide a good protection. particle filter class p2 protects against most spores of fungi. at risk of exposure to airborne viruses and bacteria, especially tuberculosis, particle filter p3 must be used. in particularly dangerous situations, during prolonged work or if carrying a beard, should special breathing systems be used" [5] (fig. 13.1 ). many human pathogenic bacteria and viruses invade via upper and lower respiratory tract [1] . some viruses may also invade via eye mucosa, such as influenza, hepatitis b and c and hiv. carl schiøtz, a norwegian professor in hygiene and infection control, wrote in the textbook of hygiene in 1937 (80 years ago) that the most important measures against communicable diseases are the following: (1) isolation of the sources of infection (home or hospital), (2) disinfection of the exposed rooms and equipment, (3) vaccination if vaccine-preventable disease, (4) quarantine, (5) food hygiene and (6) insect eradication [26] . he noticed that airborne infection was considered to be "the most important form of transmission of infections at our latitude" [26] . schiøtz meant that drops from the respiratory tracts were large and heavy and went 1.5-2 m away, while saliva droplets went in "up to 20 m distance from high-speaking people and they could stay floating in the air for several hours" [26] . this was important for the spread of "flu, colds, pneumonia, pest-pneumonia, tuberculosis, pertussis, measles, small-pox, chickenpox, scarlet fever, rubella, diphtheria, poliomyelitis, epidemic cerebrospinal meningitis and several other diseases" [26] . he also focused on inhalation of dust containing microbes [26] . the introduction of antibiotics in post-war times and the sharp reduction of lung tuberculosis caused many to forget that it was something that was infected via air. tuberculosis has been "recognized" as an airborne infection at least in 100 years, although some still believe that short-term exposure to the patient does not lead to infection. this perception has led to multiple outbreaks of multiresistant tuberculosis, including in the united states [27] . airborne transmission is most often downgraded by the health authorities to contact and droplet transmission-traditionally within 1 m from the patient. this applies to healthcare professionals who are going to treat patients with severe, deadly infections where surgical masks are estimated "good enough" [10-16, 23-25, 28-31] . droplet transmission is a definition that may put healthcare personnel at risk during dangerous situations since it is still a "form of contact transmission" [17] . the cdc definition from 2007 is upgraded since 2004 but is still very vague and controversial; see the following quotations [17] : droplet transmission is generated when "an infected person coughs, sneezes, or talks -or during procedures such as suctioning, endotracheal intubation, cough induction by chest physiotherapy and cardiopulmonary resuscitation. ---the maximum distance for droplet transmission is currently unresolved,---historically, the area of defined risk has been a distance of ≤3 feet around the patient----investigations during the global sars outbreaks of 2003 suggest that droplets --could reach persons located 6 feet or more from their source. ----thus, a distance of ≤3 feet around the patient is best viewed as an example of what is meant by 'a short distance from a patient' ----it may be prudent to don a mask when within 6 to 10 feet of the patient or upon entry into the patient's room, especially when exposure to emerging or highly virulent pathogens is likely--" [17] . "droplet size is another variable under discussion ---defined as being >5 μm in size. droplet nuclei, particles arising from desiccation of suspended droplets, have been associated with airborne transmission and defined as ≤5 μm in size-----particle dynamics have demonstrated that a range of droplet sizes, including those with diameters of 30μm or greater, can remain suspended in the air" [17] . the worst example until now is the recommendation of "contact and droplet transmission within 1 m" with the use of surgical masks (within 1 m from the patient), by who, the first phase (3 months) of the sars epidemic in 2003, where 90% of those who became ill during this first phase were health professionals [28] . the same was done during the avian influenza epidemic in 2005 and mostly throughout the influenza pandemic in 2009 [29] . who and cdc recommended both "contact and droplet transmission" measures during the first 6 months of the ebola epidemic in 2014 [1, 30] . during some of the most serious global epidemics that have happened in the last 80 years, healthcare personnel were exposed to infection without proper protective equipment and had the highest death rate associated with work-related infection [10-17, 30, 31] . during the sars outbreak in toronto, canada, 169 health personnel were infected with nosocomial sars, and 3 of these died [14, 31] . infection control personnel in toronto insisted that sars was primarily transmitted through large droplets-within 1 m-and that there was lack of evidence-based documentation for airborne infection! [31] despite the fact that health professionals requested it, the respiratory protection (n95) was not handed over to the staff, and the outbreak continued for a long time [31] . a state investigation commission came to the following bottom line conclusion: safety comes first and reasonable measures to reduce the risk of healthcare professionals do not have to wait for scientific evidence [31] . in the event of outbreaks of less severe airborne infections such as common flu, rsv, mycoplasma, adenovirus, metapneumovirus, etc., it is important to protect healthcare professionals from infection. the purpose is that infected personnel should not be "vectors" of infections in the hospital. in addition, a large outbreak among the staff may cause that patients with life-threatening diseases like heart attack, trauma, etc. do not get the necessary treatment. despite all the controversies surrounding airborne transmission, a number of international guidelines for the use of respiratory and face protection equipment have been developed under varying epidemiological conditions and experiences over the past 100 years. recent surveys and experiences show that schiøtz and other researchers had correct facts and guidelines according to airborne infections. secrets from the respiratory tract can go far off 9 m or more, for example, when coughing and sneezing, and pathogenic viruses and bacteria are detected in the air in rooms with infected patients [2, 14, 17, 18, 20, 21, 26, [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] . airborne mrsa and other multiresistant bacteria may be a greater problem than previously thought [17, 18, 20, 42] . even clostridium difficile spores may become airborne under certain conditions [43] . today, it is also known that most microbes are strong, surviving organisms outside the body [1, 44] . they can also survive on the outside of the protective equipment and even re-aerosol from these and even penetrate a wet mask [1, 4, [44] [45] [46] [47] [48] . respirators (half masks) are more expensive (about 4 usd) than surgical mask (<0.1 usd). because of a shortage during large outbreaks, it has been attempted to decontaminate respirators for reuse. however, this is not effective, is not recommended and cannot be done with disposable equipment [49] . most infectious agents are spread through contact, blood, drops, droplets, drop nuclei (aerosol), airborne on dust particles and often in several ways simultaneously [12, 13, 17, 23, [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [50] [51] [52] . transmission of microbes from the respiratory tract to the air occurs by breathing, speech, cough, sneezing, laughing, singing or other aerosol-generating procedures. sneezing usually leads to greater amount of microbes transferred to air than coughing [51] . how long the contaminant stays alive in the air depends on the agent, temperature, humidity, virus dose response, particle size and presence of other material [50] [51] [52] [53] [54] [55] [56] . some larger drops are deposited close to the patient, and smaller dropsdroplet nuclei-pass into a floating phase in the air and are falling slowly over time, such as influenza a virus [2, [50] [51] [52] [53] [54] [55] [56] . transmission of microbes via small particles and droplet nuclei from influenza patients is not adequately controlled by the use of surgical mask [50] [51] [52] . airborne transmission always includes contact transmission and often re-aerosols from the environment [18-21, 39, 42-44, 55-61] . transmission to the air from the skin occurs via the release of millions of skin particles where approximately 10% carry bacteria or virus from the skin or wound. re-aerosols from infectious particles whirled up in the air, for instance, during bed-making, dry mopping of contaminated floor surfaces, from contaminated areas in the room during air currents or when the door is opened or closed quickly [62] . re-aerosols of pathogenic microbes may be important because of a long survival in the environment, for days, months and years [1, 44] . influenza a virus survives on paper, textiles and equipment for more than 3 weeks and can become airborne [55] [56] [57] [58] [59] [60] [61] . influenza a virus is very contagious via aerosols and small airborne droplets [56] . microbial load in the air depends on cleaning and air exchange [5, [10] [11] [12] [13] [14] 63] . proper cleaning and ventilation with a positive pressure of filtered air reduce the load in the operating units or during protective isolation. decontamination and cleaning of rooms, textiles and surfaces and a good air exchange with a negative air pressure are important during isolation of patients with infections. air exchange it has been demonstrated that after aerosol-generating procedures such as bronchoscopy, airway suction and intubation, five fresh air changes in the room can greatly reduce air contamination, provided that the source of infection is gone [13] . respiratory protection prevents people from touching their nose or mouth in an infectious situation and coughing on their own uniforms and thereby exposing themselves to others and to infection [6, 7] . correct use of respiratory protection most microbes survive for hours to days on the outside of a respiratory protection as shown for bacteriophage, influenza virus and coronavirus [45] [46] [47] . this is the reason why respiratory protection should not be reused and why it is not advisable to touch the outside of the mask. during the sars outbreak in canada in 2003, the staff reinfected themselves by handling the mask incorrectly and reusing equipment without decontamination [28] . among 1441 hospital personnel in china, there was a significantly lower incidence of respiratory tract pathogenic microbes among personnel who used respiratory protection with filter n95 (p = 0.02) than among personnel using face mask (p < 0.01) compared to controls [64] . face mask, covering the nose and mouth, has been used since the spanish flu in 1919. it was actually developed to protect patients from postoperative infections from the airway flora of the operating team and protect the team against blood and tissue splash from the patient. there is no standard definition of surgical masks, adaptation, leak test or quality of filter [5, 13, 14] . surgical mask is not approved by the occupational health authorities [3-5, 24, 25] . nevertheless, there are extensive use and purchase of face masks, especially in the national emergency preparedness plans. the combination of good hand hygiene and the use of surgical mask within 36 h after the onset of influenza in an index case may however reduce spread of the flu in the household [65] [66] [67] . volunteer subjects infected with seasonal flu breathed out nearly nine times more virus in small particles, <5 μm, than in larger one, >5 μm, after the onset of the flu [50] . the use of surgical masks reduced particularly the larger particles and showed a 3.4-fold reduction of virus released to the air [50] . using surgical face masks can reduce infection and also had some suppressing effect on the spread of infection by sars [10] . surgical face mask protects the nose and mouth from splashing and saliva particles but does not protect effectively against bacteria and viruses that are, respectively, from 0.2 to 8 μm (0.0002-0.008 mm) and from 20 to 300 nm (0.02-0.3 μm) in diameter. there is no safe protection against aerosol or droplet nuclei, either through the mask or from the sides of the mask [5, 13, 24, 25, 68] . it is not certain that a mask may stop microparticles of the blood that can be formed by certain procedures, like centrifugation accidents, spray from dental treatment or surgery, etc. [36, 68] . in such cases, also eye protection should be used. persons close to sterile areas can contaminate the area by direct drops of saliva and aerosols that are spilled by speech, coughing and sneezing [2, 13] . a good face mask captures these droplets from the respiratory tract and prevents deposition thereof. it catches drops both ways to some extent, but when the surgical mask is wet, it can become less effective, with some growth of bacteria. it is usually effective for at least 2-3 h. face masks with visors protect to some extent both nasal/oral and eye mucosa against infected blood and tissue particles/droplets. airborne microparticles of aerosol, drop nuclei and blood drop-bearing bacteria and viruses can be formed during activities of or around the patient (coughing, sneezing, speech, excessive bodily activity, bed-making, dust cleaning etc.). respiratory protection such as p3 mask or n95 has shown protective effect in highly severe infections such as sars, tuberculosis and pandemic influenza [5, 9-16, 20-23, 56, 64] . respirators are not designed for children or people with beards, and therefore does not provide full protection for these [5, 23] . respiratory protection is filtering half mask, looks almost like surgical mask and is often called filtering face piece (ffp) respirators or dust filter [5] . they are of different quality (ffp1-ffp3) and capture microbes in both ways. the filter is hepafilter/polypropylene filter with static charge to increase the filter power. ffp2 is equivalent to the us n95 masks that are widely used around the world. the european standard is en149: 2001 which is equivalent to ffp3 and has a somewhat higher level of protection [13] . procedures involving large load on the environment around a patient with airborne infection are, for example, bronchoscopy, trachea suction, diathermy aerosol, suction and drilling (orthopaedics, dental treatment, etc.). in such cases, both respirators and eye protection should be used. the p3 mask protects the user and can also be used on patients with specific respiratory infection and then without exhalation valve. protection factor is calculated by reducing the degree of pollution in the air. if there is a pollution of 1000 mg/m 3 air, a respirator with a protection factor of 500 may reduce the pollution to a residue of 2 mg/m 3 . that includes inhalation of air through or on the sides of the respiratory protection, which will almost always happen [69] [70] [71] [72] . "protection factors for filtering half masks ffp1, ffp2 and ffp3 matches the protection factors for half mask with respectively filter classes p1, p2 and p3. motor-assisted filtering air purifying respirators (equipment with a turbo unit) have varying protection factor depending on the equipment design" [5] . a wet filtering mask may be permeable for viruses and bacteria. the norwegian directorate of labour inspection indicates protection factors for filtering respirators as follows [5] : lower protection is expected, because it is often leaked due to poor adaptation; factor 10 is for filtering half mask classes 2 and 3, and factor 100 is for full face masks. "protection factor for both supplied air and air purifying respirators with half and full face masks also require a good fit, and this cannot be expected if beard, glasses or the like, in squeeze along the edge of the mask" [5] . requirements for filtering half masks [5, 12, 13, [69] [70] [71] [72] . p3 has the highest protection factor with 50 times cleaner air inside the mask than outside. the mask's overall efficiency depends on the filter quality of the mask, fitting the face shape (leakage) and leakage through any exhalation [5, 12, 13, [69] [70] [71] [72] . fit test is the control and training using special odour tests that the person perceives within the mask if it is not tight enough [5, 12, 13] . in a study of five models of the n95 mask (3m 1860s cup, 3m 1870 flat fold, kimberly-clark pfr95 duckbill, safelife t5000 cup added with iodine and glaxosmithkline actiprotect cup, added with lemon acid), all five types had more than 95% efficiency: −0.8 μm particles of h1n1 influenza virus and corresponding inert particle sizes [69] . filtration efficiency was largely based on particle size [69] . so-called elastomeric masks appear to be more effective than regular filter masks [70] . studies show considerable variation with regard to protection, and for some dangerous, microbial agents, 95% protection may be too low [71, 72] . • turbo equipment (papr = -powered air-purifying respirators) with p3 filter (protection factor 500-2000) -may have problems concerning the disinfection of battery-operated, recycling systems, and is dependent on a good training [5, 12, 13] . • fresh air/pneumatic equipment (protection factor, 100-100 000) is used for particularly risky situations of special personnel in laboratories and when working in areas with severe epidemics. however, there may be serious infection problems regarding disinfection of reuse systems (filters, mechanical/electrical appliances). during non-epidemic times and with low-virulent microbes, respiratory protection (n95 or p3 masks) are not used for other than special types of respiratory infections and pulmonary tuberculosis. this may influence on the state of readiness for major outbreaks such as pandemic influenza. consumption of masks can be very large as during the sars outbreak in 2003, where a canada-based hospital with sars outbreak used up to 18,000 n95 masks each day [13] . the durability of respiratory protection equipment is good-up to 10 years or more in storage. items made with rubber or rubber parts should be checked, and there should be some systemic rotation in the warehouse [49] . at ouh, ullevål, there has been a strategic stockpile system of such equipment with replacement as required [8] . the experience from norway is that the national health authorities have been unprepared for stockpiling of emergency response requirements for ppe, also during the influenza pandemic of 2009 [29] . the market may soon be empty for respiratory protection masks during serious outbreaks such as sars and ebola virus. using several surgical face masks superposed did not have enough protective effect [73] . during the sars epidemic, the chinese healthcare personnel made their own masks of 12 layers of gauze that supposedly would work well. this is used when there is risk in soil and splatter of biological materials and to protect against highly dangerous infection. if there is a risk of transmission of severe respiratory infection, tight-fitting goggles are used. the goggles can be reused after 1 h of treatment in 5% chloramine, followed by washing with soap and water, and they may also be reprocessed and decontaminated in a washing machine at >85 °c. controversial issues concerning airborne infection and protection against "droplet transmission" should be further studied. particle studies; ventilation variations; kinetics; the effect of humidity, temperature and filter types; re-aerosols from dust; environment and ppe equipment; and the survival of microbes in the environment should be better studied. this is the case for most important microbial agents: bacteria, viruses and fungi. respirators should be preferred over surgical masks when there is suspected droplet or airborne transmission. this choice is essentially a misunderstood price and attitude problem. microbiology and infection control. handbook of hygiene and infection control in hospitals violent expiratory events: on coughing and sneezing protection of workers from the risks when working with biological factors on the protection of workers from the risks related to exposure to biological agents at work (seventh individual directive according to article 16 norwegian directorate of labour inspection. respiratory protection controlling the novel a (h1n1) influenza virus: do not touch your face! european centre for disease prevention and control -swine flu guidelines: "cough hygienically" into your sleeve? serious, communicable disease -personal protective equipment-ppe. in: handbook of hygiene and infection control in hospitals. oslo: ullevaal university hospital respiratory protection. breathing equipment with fresh air hose connected to a full face mask, half mask or mouthpiece means. requirements, testing, mark. ns-en 138 non-pharmaceutical interventions for pandemic influenza, national and community measures interim guidance on infection control measures for 2009 h1n1 influenza in healthcare settings, including protection of healthcare personnel guidance on the use of respiratory and facial protection equipment respiratory and facial protection: a critical review of recent literature controversy: respiratory protection for healthcare workers ecdc health information. personal protective measures for reducing the risk of acquiring or transmitting human influenza respiratory protection for healthcare workers in the workplace against novel h1n1 influenza a guideline for isolation precautions: preventing transmission of infectious agents in healthcare settings air contamination around patients colonized with multi drug-resistant organisms the exposure to hospital room is fed as a risk factor for healthcare-associated infection aerial dispersal of methicillin-resistant staphylococcus aureus in hospital rooms by infected or colonised patients evaluation of bedmaking-related airborne and surface methicillin-resistant staphylococcus aureus contamination guidelines for preventing the transmission of mycobacterium tuberculosis in health-care facilities food and drug administration osha. respiratory protection standard work place safety and health topics: respirator the infectious diseases. textbook in hygiene. oslo: fabritius & sønners forlag mycobacterium tuberculosis. in: bacteria and disease. epidemiology, infection and immunity. oslo: gyldendal academic in: microbiology and infection control. handbook of hygiene and infection control in hospitals. part 1. bergen: fagbokforlaget pandemic influenza. in: microbiology and infection control. handbook of hygiene and infection control in hospitals. part 1. bergen: fagbokforlaget international infection control guidelines may not protect against ebola. hospital healthcare ontario ministery of health and long-term care. sars commission-spring of fear: final report role of ventilation in airborne transmission of infectious agents in the built environment-a multi-disiplinary systematic review virus diffusion in isolation rooms review of aerosol transmission of influenza a virus aiborne dispersal as a novel transmission route of coagulase-negative staphylococci, interaction between coagulase-negative staphylococci and rhinovirus infection the risk of blood splash contamination during angiography aerosol transmission of influenza a virus: a review of new studies transmission of influenza a in human beings detection of bordetella pertussis and respiratory syncytial virus in air samples from hospital rooms an outbreak of influenza abroad a commercial airliner droplet fate in indoor environments, or can we prevent the spread of infection? indoor air air and surface contamination patterns of methicillinresistant staphylococcus aureus on eight acute hospital wards the potential for airborne dispersal of clostridium difficile from symptomatic patients virus survival in the environment corona virus survival on healthcare personnel protective equipment survival of surrogate viruses on n95 respirator material persistence of the 2009 pandemic influenza a (h1n1) virus on n95 respirators re-aerosolization of ms2 bacteriophage from an n95 filtering facepiece respirator by simulated coughing evaluation of five decontamination methods for filtering face-piece respirators influenza virus aerosols in human exhaled breath: particle size, culturability, and effect of surgical masks viral kinetics and exhaled droplet size affect indoor transmission dynamics of influenza infection aerosol transmission is an important mode of influenza a virus spread dynamics of airborne influenza a viruses indoors and dependence on humidity mechanisms by ambient humidity mayaffect viruses in aerosols inactivation of influenza a viruses in the environment and modes of transmission: a critical review high infectivity and pathogenity of influenza a virus via aerosol and droplet transmission survival of influenza viruses on environmental surfaces survival of influenza viruses on banknotes association of private isolation rooms with ventilatorassociated acinetobacter baumannii pneumonia in surgical intensive-care unit an evaluation of hospital special-ventilation-room pressures survival of influenza a (h1n1) on materials found in householders: implications for infection control door-opening motion can potentially lead to a transient breakdown in negative-pressure isolation conditions: the importance of vorticity and buoyancy airflows mopping up hospital infection efficacy of face masks and respirators in preventing upper respiratory tract bacterial colonization and co-infection in hospital healthcare workers face masks and hand hygiene to prevent influenza transmission in households: a cluster randomized trial preliminary findings of a randomized trial of nonpharmaceutical interventions to prevent influenza transmission in households face mask use and control of respiratory virus transmission in households aerosol penetration and leakage characteristics of masks used in the healthcare industry challenge of n95 filtering face-piece respirators with viable h1n1 influenza aerosols comparison of performance of three different types of respiratory protection devices do n95 respirators not provide 95% protection level against airborne viruses, and how adequate are surgical masks? performace of an n95 filtering face-piece particulate respirator and a surgical mask during human breathing: two pathways for particle penetration protecting staff against airborne viral particles: in vivo efficiency of laser masks key: cord-253827-5vodag6c authors: karaivanov, a.; lu, s. e.; shigeoka, h.; chen, c.; pamplona, s. title: face masks, public policies and slowing the spread of covid-19: evidence from canada date: 2020-09-25 journal: nan doi: 10.1101/2020.09.24.20201178 sha: doc_id: 253827 cord_uid: 5vodag6c we estimate the impact of mask mandates and other non-pharmaceutical interventions (npi) on covid-19 case growth in canada, including regulations on businesses and gatherings, school closures, travel and self-isolation, and long-term care homes. we partially account for behavioral responses using google mobility data. our identification approach exploits variation in the timing of indoor face mask mandates staggered over two months in the 34 public health regions in ontario, canada's most populous province. we find that, in the first few weeks after implementation, mask mandates are associated with a reduction of 25 percent in the weekly number of new covid-19 cases. additional analysis with province-level data provides corroborating evidence. counterfactual policy simulations suggest that mandating indoor masks nationwide in early july could have reduced the weekly number of new cases in canada by 25 to 40 percent in mid-august, which translates into 700 to 1,100 fewer cases per week. when government policies to stem the spread of were introduced in early 2020, the best available evidence supporting them was provided by studies of previous epidemics, epidemiological modeling, and case studies (oecd, 2020). even when the efficacy of a given precaution in reducing covid -19 transmission has been established, significant doubts regarding the usefulness of specific policy measures may persist due to uncertainty regarding adherence to the rules and other behavioral responses. for example, even though several observational studies, mostly in medical setting, have shown that face masks reduce the transmission of and similar respiratory illnesses (see chu et al. (2020) for a comprehensive review), a face mask mandate may not be effective in practice if it fails to increase the prevalence of mask wearing (compliance), or if it leads to increased contacts due to a false sense of security. it is therefore important to directly evaluate and quantify the relationship between various policy measures and the rate of propagation of . the low cost and high feasibility of mask mandates relative to other containment measures for has generated keen interest worldwide for studying their effectiveness. this attention has been compounded by substantial variation, across jurisdictions and over time, in official advice regarding the use of masks. figure b1 in the appendix plots self-reported mask usage in select countries (canada, united states, germany and australia) in the left panel, and across canadian provinces in the right panel. the figure shows large differences in mask usage, both across countries and within canada. 1 we estimate and quantify the impact of mask mandates and other non-pharmaceutical interventions (npi) on the growth of the number of covid-19 cases in canada. canadian data has the important advantage of allowing two complementary approaches to address our objective. first, we estimate the effect of mask mandates by exploiting within-province geographic variation in the timing of indoor face mask mandates across 34 public health regions (phus) in ontario, canada's most populous province with a population of nearly 15 million or roughly 39% of canada's population (statistics canada, 2020). the advantage of this approach is that it exploits variation over a relatively small geographic scale (phu), holding all other province-level policies or events constant. in addition, the adoption of indoor face mask mandates in these 34 sub-regions was staggered over approximately two months, creating sufficient intertemporal policy variation across the phus. second, we evaluate the impact of npis in canada as a whole, by exploiting variation in the timing of policies across the country's ten provinces. by studying inter-provincial variation, we are able to analyze the impact of not only mask mandates, but also other npis, for which there is little or no variation across ontario's phus (regulations on businesses and gatherings, schooling, travel and long-term care). in addition, our province-level data include both the closing period (march-april) and the gradual re-opening period (may-august), providing variation from both the imposition and the relaxation of policies. our panel-data estimation strategy broadly follows the approach of chernozhukov, kasahara and schrimpf (2020), hereafter cks (2020), adapted to the canadian context. we allow for behavioural responses (using google community mobility reports geo-location data as proxy for behaviour changes and trends), as well as lagged outcome responses to policy and behavioral changes. our empirical approach also allows current epidemiological outcomes to depend on past outcomes, as an information variable affecting past policies or behaviour, or directly, as in the sir model framework. we find that, in the first few weeks after their introduction, mask mandates are associated with an average reduction of 25 to 31% in the weekly number of newly diagnosed cases in ontario, holding all else equal. we find corroborating evidence in the province-level analysis, with a 36 to 46% reduction in weekly cases, depending on the empirical specification. furthermore, using survey data, we show that mask mandates increase self-reported mask usage in canada by 30 percentage points, suggesting that the policy has a significant impact on behaviour. jointly, these results suggest that mandating indoor mask wear in public places is a powerful policy measure to slow the spread of , with little associated economic disruption at least in the short run. 2 counterfactual policy simulations using our empirical estimates suggest that mandating indoor masks nationwide in early july could have reduced weekly new cases in canada by 25 to 40% on average by mid-august relative to the actually observed numbers, which translates into 700 to 1,100 fewer cases per week. we also find that the most stringent restrictions on businesses and gatherings observed in our data are associated with a decrease of 48 to 57% in weekly cases, relative to a lack of restrictions. the business/gathering estimates are, however, noisier than our estimates for mask mandates and do not retain statistical significance in all specifications; they appear driven by the smaller provinces and the re-opening period (may to august). school closures and travel restrictions are associated with a large decrease in weekly case growth in the closing period. our results on business/gathering regulations and school closure suggest that reduced restrictions and the associated increase in business or workplace activity and gatherings or school re-opening can offset, in whole or in part, the estimated effect of mask mandates on case growth, both in our sample and subsequently. an additional contribution of this research project is to assemble, from original official sources only, and make publicly available a complete dataset of cases, deaths, tests and policy measures in all 10 canadian provinces. 3 to this end, we constructed, based on official public health orders and announcements, time series for 17 policy indicators regarding face masks, regulations on businesses and gatherings, school closures, travel and self-isolation, and long-term care homes. our paper relates most closely to two recent empirical papers on the effects of mask mandates using observational data. 4 cks (2020) and mitze et al. (2020) study the effect of mask mandates in the united states and germany, respectively. cks (2020), whose estimation strategy we follow, exploit u.s. state-level variation in the timing of mask mandates for employees in public-facing businesses, and find that these mandates are associated with 9 to 10 percentage points reduction in the weekly growth rate of cases. this is substantially smaller that our estimates, possibly because the mask mandates that we study are much broader: they apply to all persons rather than just employees, and most apply to all indoor public spaces rather than just businesses. mitze et al. (2020) use a synthetic control approach and compare the city of jena and six regions in germany that adopted a face mask policy in early to mid april 2020, before their respective state mandate. they find that mandatory masks reduce the daily growth rate of cases by about 40%. our paper has several advantages compared to the above two papers. first, we exploit both regional variation within the same province (like mitze et al., 2020) and provincial variation in the whole country (like cks, 2020), and find similar results, which strengthens the validity of our findings. second, we show that self-reported mask usage has increased after introducing mask mandates. we view this "first-stage" result on mask usage as informative, as the effectiveness of any npi or public policy critically depends on the compliance rate. moreover, this result mitigates possible concerns that the estimated mask mandate effect on case growth may be caused by factors other than mask policy. third, a key difference between our paper and cks (2020) is that we evaluate the effect of universal (or community) mandatory indoor mask wearing for the public rather than the effect of mandatory mask wearing for employees only. 5 while other factors such as differences in mask wear compliance between canada and the u.s. may contribute to the different estimated magnitude of the policy impact, our results suggest that more comprehensive mask policies can be more effective in reducing the case growth rate. other related literature abaluck et al. (2020) discuss the effectiveness of universal adoption of homemade cloth face masks and conclude that this policy could yield large benefits, in the $3,000-$6,000 per capita range, by slowing the spread of the virus. the analysis compares countries with pre-existing norms that sick people should wear masks (south korea, japan, hong kong and taiwan) and countries without such norms. 6 in the medical literature, prather et al. (2020) argue that masks can play an important role in reducing the spread of covid-19. howard et al. (2020) survey the medical evidence on mask efficiency and recommend public use of masks in conjunction with existing hygiene, distancing, and contact tracing strategies. greenhalgh et al. (2020) provide evidence on the use of masks during non-covid epidemics (influenza and sars) and conclude that even limited protection could prevent some transmission of . leung et al. (2020) study exhaled breath and coughs of children and adults with acute respiratory illness and conclude that the use of surgical face masks could prevent the transmission of the human coronavirus and influenza virus from symptomatic individuals. meyerowitz et al. (2020) present a recent comprehensive review of the evidence on transmission of the virus and conclude that there is strong evidence from case and cluster reports indicating that respiratory transmission is dominant, with proximity and ventilation being key determinants of transmission risk, as opposed to direct contact or fomite transmission. our paper also complements recent work on covid-19 policies in canada. mohammed et al. (2020) use public opinion survey data to study the effect of changes in mask-wear policy recommendations, from discouraged to mandatory, on the rates of mask adoption and public trust in government institutions. they show that canadians exhibit high compliance with mask mandates and trust in public health officials remained consistent across time. yuksel et al. (2020) use an outcome variable constructed from apple mobility data along period january 3 to february 6, 2020. 9 in ontario, these location data are available for each of the 51 first-level administrative divisions (counties, regional municipalities, single-tier municipalities and districts). 10 we follow the approach of cks (2020), but modify and adapt it to the canadian context. the empirical strategy uses the panel structure of the outcome, policy and behavioral proxy variables, and includes lags of outcomes as information, following the causal paths suggested by the epidemiological sir model (kermack and mckendrick, 1927) . specifically, we estimate the effect of policy interventions on covid-19 outcomes while controlling for information and behaviour. in contrast to cks (2020) and hsiang et al. (2020) , who study variation in npis across u.s. states or across countries, our identification strategy exploits policy variation at the sub-provincial level (ontario's phus) in addition to cross-province variation, and our data captures both the closing down and gradual re-opening stages of the epidemic. 5. controls, w it -province or phu fixed effects, growth rate of weekly new tests, and a time trend. to assess and disentangle the impact of npis and behavioral responses on covid-19 outcomes, we estimate the following equation: where l denotes a time lag measured in days. equation (1) models the relationship between covid-19 outcomes, y it , and lagged behaviour, b it−l , lagged policy measures, p it−l and information (past outcomes), i it = y it−l . for case growth as the outcome, we use l = 14. for deaths growth as the outcome, we use l = 28. 11 the choice of these lags is discussed in appendix d. by including lagged outcomes, our approach allows for possible endogeneity of the policy interventions p it , that is, the introduction or relaxation of npis based on information on the level or growth rate of cases or deaths. also, past cases may be correlated with (lagged) government policies or behaviors that may not be fully captured by the policy and behaviour variables. in appendix table a18 , we also report estimates of the following equation: which models the relationship between policies p it , information, i it (weekly levels or growth of cases or deaths) and behaviour, b it . it is assumed that behaviour reacts to the information without a significant lag. we find strong correlation between policy measures and the google mobility behavioral proxy measure. equation (1) captures both the direct effect of policies on outcomes, with the appropriate lag, as well as the potential indirect effect on outcomes from changes in behaviour captured by the changes in geo-location proxy b it−l . in appendix tables a19 and a20, we also report estimates of equation (1) without including the behavioral proxy, that is, capturing the total effect of policies on outcomes. since our estimates of the coefficient α in equation (1) are not significantly different from zero, the results without controlling for the behavioral proxy are very similar to those from estimating equation (1). outcomes. our main outcome of interest is the growth rate of weekly new positive cases as defined below. 12 we use weekly outcome data to correct for the strong day-of-the-week effect present in covid-19 outcome data. 13 weekly case growth is a metric that can be helpful in assessing trends in the spread of , and it is highlighted in the world health organization's weekly epidemiological updates (see, for example, world health organization (2020)). specifically, let c it denote the cumulative case count up to day t and define ∆c it as the weekly covid-19 cases reported for the 7-day period ending at day t: the weekly case (log) growth rate is then defined as: that is, the week-over-week growth in cases in region i ending on day t. 14 the weekly death growth rate is defined analogously, using cumulative deaths data. policy. in the ontario analysis, we exploit regional variation in the timing of indoor mask mandates staggered over two months in the province's 34 regions ("public health units" or phus). figure 1 displays the gradual introduction of mask mandates across the 34 phus in ontario. the exact implementation dates of the mask mandates are reported in table c2 . mandatory indoor masks were introduced first in the wellington-dufferin-guelph phu on june 12 and last in the northwestern phu on august 17. 15 12 we also report results using the growth rate of deaths as supplemental analysis in section 4.6. 13 figures b9 and b10 in the appendix respectively display the weekly and daily cases, deaths and tests in each canadian province over time. there are markedly lower numbers reported on weekends or holidays. 14 to deal with zero weekly values, which mostly occur in the smaller regions, as in cks (2020), we replace log(0) with -1. we also check the robustness of our results by adding 1 to all ∆c it observations before taking logs, by replacing log(0) with 0, and by using population weighted least squares; see tables a5 and a8 . 15 there is no phu-wide mask mandate in lambton as of august 31, but its main city, sarnia, enacted a mask mandate on july 31. figure 1 : ontario -mask mandates over time 15 in the province-level analysis, we assign numerical values to each of the 17 policy indicators listed in table c1 in appendix c. the values are on the interval [0,1], with 0 meaning no or lowest level of restrictions and 1 meaning maximal restrictions. a policy value between 0 and 1 indicates partial restrictions, either in terms of intensity (see more detail and the definitions in table c1 ) or by geographical coverage (in large provinces). the numerical values are assigned at the daily level for each region (phu or province, respectively for the ontario and national results), while maintaining comparability across regions. many npis were implemented at the same time, both relative to each other and/or across regions (especially during the march closing-down period), which causes many of the policy indicators to be highly correlated with each other (see appendix table a4 ). to avoid multi-collinearity issues, we group the 17 policy indicators into 5 policy aggregates via simple averaging: (i) travel, which includes international and domestic travel restrictions and self-isolation rules; (ii) school, which is an indicator of provincial school closure; (iii) business/gathering, which comprises regulations and restrictions on non-essential businesses and retail, personal businesses, restaurants, bars and nightclubs, places of worship, events, 10 gyms and recreation, and limits on gathering; (iv) long-term care (ltc), which includes npis governing the operation of long-term care homes (visitor rules and whether staff are required to work on a single site) and (v) mask which takes value 1 if an indoor mask mandate has been introduced, 0 if not, or value between 0 and 1 if only part of a province has enacted such policy. 16 the five policy aggregates are constructed at the daily level and capture both the closingdown period (an increase in the numerical value from 0 toward 1) and the re-opening period (decrease in the numerical value toward zero). in comparison, the policy indicators compiled by raifman (2020) for the usa used in cks (2020) are binary "on (1)"/"off (0)" variables. 17 for consistency with the weekly outcome and information variables and the empirical model timing, we construct the policy aggregates p j it used in the regressions (where j denotes policy type) by taking a weekly moving average of the raw policy data, from date t − 6 to date t. figure 2 plots the values of the 5 policy aggregates over time for each of the 10 provinces. travel restrictions, school closures (including spring and summer breaks) and business closures were implemented in a relatively short period in the middle of march. there is some variation in the travel policy aggregate since some canadian provinces (the atlantic provinces and manitoba) implemented inter-provincial domestic travel or self-isolation restrictions in addition to the federal regulations regarding international travel. restrictions on long-term care facilities were introduced more gradually. in the re-opening period (may-august), there is also more policy intensity variation across the provinces, especially in the business and gatherings category, as the different provinces implemented their own re-opening plans and strategies. mask mandates were first introduced in ontario starting from june in some smaller phus and early july in the most populous phus such as toronto, ottawa and peel (see appendix table c2 ). in quebec, indoor masks were mandated province-wide on july 18. nova scotia and alberta's two main cities implemented mask mandates on july 31 and august 1, respectively. there are two empirical challenges specific to our canadian context and data. the first challenge is the presence of small provinces and sub-regions with very few covid-19 cases or deaths. in section 4.3, we perform a number of robustness checks using different ways of handling the observations with very few cases (in particular zero cases). the second data limitation is that there are only 10 provinces in canada and 34 public health units in ontario, unlike the 51 u.s. jurisdictions in cks (2020). to account for the resulting small number of clusters in the estimation, we compute and report wild bootstrap standard errors and p-values, as proposed by cameron et al. (2008) . 18 on the flip side, our data has the advantage of a longer time horizon (march to august) and non-binary, more detailed policy variables compared to raifman et al. (2020). behaviour proxy. we follow cks (2020) and other authors in interpreting the location change indices from the google community mobility reports as proxies for changes in people's behaviour during the pandemic, keeping in mind that location is only one aspect of behaviour relevant to . the general pattern in the data (see figure b3 ) shows sharply reduced frequency of recorded geo-locations in shops, workplaces and transit early in the pandemic (march), with a subsequent gradual increase back toward the baseline (except for transit), and a flattening out in july and august. several of the six location indicators (retail, grocery and pharmacy, workplaces, transit, parks and residential) are highly correlated with each other (see tables a1 and a2 ) and/or contain many missing observations for the smaller provinces. to address these data limitations and the possible impact of collinearity on the estimation results, we use as proxy for behavioral changes the simple average of the following three mobility indicators: "retail", "grocery and pharmacy" and "workplaces". to be consistent with the weekly outcome variables and to mitigate day-of-week behavioural variation, we construct the behaviour proxy b it by taking a weekly moving average of the 1 3 (retail + grocery and pharmacy + workplaces) data, from date t − 6 to date t. 19, 20 as a result, our empirical analysis uses weekly totals (for cases, tests and deaths) or weekly moving averages (for policies and the behaviour proxy) of all variables recorded on daily basis. 21 18 alternative methods for computing the standard errors are explored in section 4.3. 19 we drop the "transit", "parks", and "residential" location indicators because, respectively, 10.6%, 13.7%, and 2.8% of the observations are missing in the provincial data, and 20.7%, 52.1%, and 11.1% are missing in the ontario data. the "transit" and "residential" variables are also highly correlated with the three indicators we include in our aggregate behaviour proxy b it . furthermore, the "parks" indicator does not have clear implication for outcomes. 20 in the ontario analysis, 1.4% of the b it values are imputed via linear interpolation. 21 in estimation equation (1), we take moving average from date t − 14 to date t − 20 for policies and behaviour when the outcome is weekly case growth, and from date t − 28 to date t − 34 if the outcome is tables a3 and a4 display the correlation between our behaviour proxy b it and the five npi policy aggregates p j it . importantly, the behaviour proxy and mask mandate variables are not highly correlated, suggesting that the effect of mask mandates on covid-19 outcomes should be independent of location behaviour changes. information. we use the weekly cases and case growth variables defined above, ∆c it and y it , to construct the information variables i it in equation (1) . specifically, we use as information the lagged value of the weekly case growth rate y it−l (= ∆ log(∆c it−l ) and the log of past weekly cases, log(∆c it−l ). we also use the lagged provincial (ontario analysis) or national (canada analysis) case growth rate and log of weekly cases as additional information variables in some specifications. a two-week information lag l = 14 is used in the baseline results. in the supplementary regressions using the death growth rate as the outcome, we use information on past deaths and a four-week lag (see section 4.6). control variables. in all regressions, we control for region fixed effects (phu or province) and the weekly covid-19 tests growth rate ∆ log(∆t it ), where t it denotes cumulative tests in region i until date t and ∆t it is defined analogously to ∆c it above. we include a time trend: our baseline uses a cubic polynomial in days, but we also report results with no time trend and with week fixed effects. robustness checks also include news or weather variables as controls (see section 4.3). time period. we use the period may 15 to august 13 for the analysis with ontario phu level data and the period march 11 to august 13 for the national analysis with provincial data. the end date reflects data availability at the time of empirical analysis and writing. the start date for the ontario sample (may 15) is approximately two weeks after the last restrictive measures were implemented and four weeks before the first mask mandate was introduced in ontario. robustness checks with different initial dates (may 1, june 1 and june 15) are reported in section 4.3, with our results remaining stable. the initial date for the national sample (march 11) was chosen as the first date on which each province reported at least one covid-19 test (so that cases could be potentially reported). again, alternative initial dates are explored in section 4.3. we start with a simple graphical illustration of the effect of mask mandates on covid-19 cases growth. figure 3 displays the average log case growth, y it = ∆ log(∆c it ) in ontario phus with or without mask mandates. it shows that, on average, the phus with a mask mandate two weeks prior have lower case growth than the phus without a mask mandate two weeks prior. 15 no mask mandate at t -14 mask mandate at t -14 notes: the figure plots the average log weekly case growth ∆log(∆c) in the phus with mask mandate (blue) vs. without (red) mask mandate 14 days prior. table 1 shows the estimates of equation (1), in which we control for other policies, behaviour and information, as explained in section 3.1. 22 we report wild bootstrap p-values clustered at the phu level to account for the small number of clusters. 23 the odd-numbered 22 mask mandates and regulations on business and gatherings vary at the phu level. long-term care policy changed only province-wide. the other policies (schooling and travel) do not vary during the sample period and hence are omitted from the regressions with ontario phu data. 23 table a6 in the appendix reports alternative standard error specifications: regular clustering at the phu level (stata command "cluster"), wild bootstrap standard errors clustered at the phu level, and wild columns in table 1 use lagged cases and lagged cases growth at the phu level as information; the even-numbered columns also include lagged cases and lagged case growth at the province level as additional information variables. in the tables, variable 14 indicates a 14-day lag of variable. we present estimates of equation (1) from three specifications that handle possible time effects differently. columns (1) and (2) in table 1 are the most basic specifications, without including a time trend. the estimates in columns (1) and (2) suggest that, controlling for behavioural changes, mandatory indoor face masks reduce the growth rate of infections by 29-32 log points (p < 0.05), which is equivalent to a 25-28% reduction in weekly cases. 24 in order to control for potential province-wide factors affecting the spread of covid-19 such as income support policies or adaptation to the pandemic over time (so-called covid fatigue), we also estimate (1) with a cubic time trend in days from the beginning of the sample, in columns (3) and (4) of table 1 , and with week fixed effects, in columns (5) and (6) . columns (3)(6) show that our estimates of the mask mandate policy remain robust to the inclusion of a cubic time trend or week fixed effects. the results indicate that, depending on the specification, mask mandates are associated with a reduction of up to 38 log points in weekly case growth or, equivalently, a 31% reduction in weekly cases. the magnitude of the mask policy estimate is not very sensitive to whether lagged province-level data are included as additional information. the results in table 1 suggest that indoor mask mandates can be a powerful preventative measure in the covid -19 context. our estimates of the mask mandate impact across ontario's phus are equivalent to a 25-31% reduction in weekly cases. this estimate is larger than the 9-10% reduction estimated by cks (2020) for the u.s. one possible explanation is that ontario's mask policy is more comprehensive: we evaluate the effect of universal indoor mask-wearing for the public rather than the effect of mask wearing for employees only in cks (2020). differences in the compliance rate may also contribute to this difference; we discuss this potential channel in section 4.4. the results in table 1 also show a statistically significant negative association between information (log of past cases, log(∆c) 14) and current weekly case growth (p < 0.01 in all specifications), indicating that a higher level of cases two weeks prior is correlated with lower current case growth. while b it allows for behavioural responses to information, the negative estimate on log(∆c) 14 in table 1 suggests that our location-based proxy does not capture bootstrap standard errors clustered by both phu and date. our results are robust to alternative ways of calculating standard errors. 24 using equation (3), a coefficient of x translates into a 1 − exp(x) reduction in weekly cases ∆c it /∆c it−7 . 1 and in section 4.2's province-level results), unlike in cks (2020). 25 in appendix table a18 , we find strong contemporaneous correlations between the policy measures, log cases, and the google mobility behavioral proxy from estimating equation (2) . this suggests that the information (lagged cases) and the lagged policy variables included in equation (1) may absorb lagged behavioral responses proxied by b it−l or other latent behavioral changes not captured by b it−l . we next evaluate the impact of npis on covid-19 cases growth in canada as a whole by exploiting variation in the timing of policies across the 10 provinces. here, we examine npis for which there is no variation across ontario's phus (i.e., schooling, travel, and ltc) in addition to mask mandates. also, provincial data contain variation in the timing of policy changes in both the closing and re-opening phases, allowing us to study both the imposition and relaxation of restrictions. figure 4 : canada -mask mandates and weekly case growth 15 no mask mandate at t -14 mask mandate at t -14 notes: the figure plots the average weekly case growth ∆ log(∆c) in the provinces with mask mandate (blue) vs. without mask mandate (red) 14 days prior. 25 we also tried including each location change measure separately and the results are similar (not shown). all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . as in the ontario analysis, we begin with a graphical illustration of mask mandates and covid-19 case growth across canadian provinces, in the period march 11 to august 13, 2020. figure 4 plots the average log weekly case growth in the provinces with vs. without mask mandates. while mask mandates are implemented relatively late in our sample period, average case growth in the provinces with a mask mandate (ontario and quebec) diverged from the average case growth in the provinces without a mandate begin roughly four weeks after the mandates are imposed. 26 table 2 displays the estimates of equation (1) for weekly case growth, along with wild bootstrap p-values, clustered at the province level (see table a9 for other methods of computing the standard errors). the odd-numbered columns use lagged cases and lagged case growth at the provincial level as information while the even-numbered columns include in addition lagged cases and case growth at the national level as additional information variables. as in the ontario analysis, we present in table 2 estimates from three specifications: no time trend (columns (1)-(2)), including cubic time trend in days (columns (3)-(4)) and including week fixed effects (columns (5)(6)). the most robust result is the estimated effect of mask mandates: they are associated with a large reduction in weekly case growth of 45 to 62 log points, which is equivalent to a 36 to 46% reduction in weekly cases across the different specifications. the estimates are statistically significantly different from zero in all cases, with a p-value of less than 0.001 in columns (1)(4) . it is reassuring that these results regarding mask mandates are consistent with the ontario analysis in the previous section. table 2 further shows that restrictions on businesses and gatherings are associated with a reduction in the weekly case growth of 65 to 85 log points or, vice versa, that relaxing business/gathering restrictions is associated with higher case growth. the estimate is equivalent to a 48 to 57% decrease in weekly cases in our sample period. the business/gathering estimates are, however, more noisy than our estimates for mask mandates and do not retain statistical significance in the specifications with week fixed effects (p = 0.15 and 0.14). tables a8 and a15 further suggest that the results on business and gathering npis are driven by the smaller provinces and the re-opening period (may to august). still, these results suggest that lowered restrictions and the associated increase in business/workplace activity or gatherings can be an important offsetting factor for the estimated effect of mask mandates on covid-19 case growth, both in our sample and in the future. we also find that school closures (the school 14 variable in table 2 ) can be negatively 26 figure 4 assumes a july 7 mask mandate implementation date for ontario (when its most populous phu, toronto, adopted a mask mandate, along with ottawa), and july 18 for quebec (province-wide mandate). all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . associated with case growth. however, the estimates are statistically significant from zero only in the specifications with cubic time trend (columns (3) and (4)). as seen in figure 20 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . 2, provincial school closures occurred in a very short time interval during march, so we may lack statistical power to separately identify its effect from other npis (especially the travel-related). hence, we interpret this result with caution. as in table 1 , the level of past cases, log(∆c), is negatively and statistically significantly associated with current weekly case growth in columns (1)(4) . since the specification with cubic time trend in tables 1 and 2 allows for possible nonmonotonic aggregate time trends in case growth in a parsimonious way, we choose it as our baseline specification with which to perform robustness checks in the next section. robustness checks with the other specifications are available upon request. a possible concern about our data for the national analysis is that some npis (e.g. international travel restrictions or closing of schools) were implemented within a very short time interval. 27 thus, we may lack enough regional variation to distinguish and identify the separate effect of each policy. 28 collinearity could also affect the standard errors and the signs of the estimated coefficients. to check robustness with respect to potential collinearity in the npi policies, tables a7 and a10 report estimates from our baseline specification, omitting one policy at a time, for ontario and canada respectively. first, it is reassuring that the mask mandate estimates are hardly affected by omitting any of the other policies. this is expected since mask mandates were imposed during a period where other npis changed little (see figure 2) . similarly, the effects of business/gathering regulations and school closures in table a10 are not sensitive to omitting other policies one at a time, which suggests that there is sufficient statistical power and variation to identify them in the national analysis. another concern for our empirical strategy is that the usual formula for our dependent variable, ∆ log(∆c it ), cannot be applied when the weekly case total ∆c it is zero. we follow cks (2020) and replace ln(0) with -1 in our baseline specifications in tables 1 and 2 . we now check the robustness of our estimates to alternative treatments of zero weekly cases. for easier comparison, the first two columns in table a5 repeat columns (3) and (4) 27 for example, table a4 shows a correlation of 0.61 between the travel and school policy aggregates. 28 aggregating the 17 basic policy indicators into five groups mitigates this issue. here, we test whether any remaining collinearity poses a problem. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . from table 1 for ontario. 29 our main results on mask mandates across ontario phus are robust to replacing log(0) with 0 and to adding 1 to all ∆c it observations before taking logs, as shown in columns (3)-(6) of table a5 . another way to mitigate the issue of phus with very few cases is to estimate a weighted least squares regression where phus are weighted by population. columns (7) and (8) in table a5 show that the resulting mask estimate has a slightly smaller magnitude and, due to the reduced effective sample size, weaker statistical significance. similarly, table a8 shows that our province-level estimates, in particular for mask mandates, are also robust to the same manipulations as above. 30 in columns (9) and (10) of table a8 , we restrict the sample to only the largest 4 provinces (british columbia, ontario, quebec and alberta), which have only 0.3% (2 out of 624) zero observation cases. again, the estimated mask effects are little changed. figure b4 shows that our estimates and confidence intervals for the effect of mask mandates in the ontario baseline regressions do not vary much by the initial date of the sample. similarly, figure b5 shows that, in the national analysis, our results about mask mandates and business/gathering restrictions are also robust to alternative sample start dates. we explore alternative time lags, either shorter or longer in duration, centered around the baseline value of 14 days. figure b6 (with ontario data) and figure b7 (with province-level data) plot the estimates and confidence intervals from the baseline regressions and show that our mask effect estimates remain fairly consistent for different lags. our behaviour proxy variable (google geo-location trends) likely misses some aspects of behaviour relevant for covid -19 transmission. one factor that may meaningfully impact behaviour is weather. for example, good weather could entice more people to spend time outside, lowering the chance of viral transmission. columns (3) and (4) in table a11 report national estimates with lagged weather variables (daily maximum and minimum temperatures and precipitation for the largest city in each province 31 ) as additional regressors. our npi estimates, in particular mask mandates, are little changed from the baseline results in columns (1) and (2) . all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . another possible concern is that our information variables, lagged cases and lagged case growth, may not fully capture the information based on which people react or adjust their behaviour, possibly affecting the observed weekly case growth. columns (5) and (6) in table a11 add a national-level "news" variable to the baseline specification. the news variable is defined as the number of daily search results from a news aggregator website (proquest canadian newsstream) for the terms "coronavirus" or "covid-19" (see appendix c for more details). in column (6), the lagged news variable approaches the 10% significance level (p = 0.103). our estimates on masks and business/gathering remain very close to those in the baseline. the effectiveness of any npi or public policy crucially depends on whether it affects behaviour. in this section, we use self-reported data on mask usage to examine whether mask mandates indeed increase mask use in canada ("first-stage" analysis). we use data from the yougov covid19 public monitor, which includes multiple waves of public opinion surveys fielded regularly since early april in many countries. 32 here, we focus on inter-provincial comparison within canada. our variable of interest is based on responses to the question "thinking about the last 7 days, how often have you worn a face mask outside your home (e.g. when on public transport, going to a supermarket, going to a main road)?" the answer choices are "always", "frequently", "sometimes", "rarely", and "not at all". we create a binary variable taking value 1 if the response is "always" and 0 otherwise, as well as another variable taking value of 1 if the respondent answered either "always" or "frequently" and 0 otherwise. we begin with a simple illustration of self-reported mask usage in canada from april to august 2020. figure b2 plots the average self-reported mask usage (the response "always") in the provinces with and without mask mandates. 33 the figure clearly shows that selfreported mask usage is higher, by up to 50 percentage points, in the provinces with a mask mandate than in the provinces without mask mandates. since figure b2 does not account for compositional changes in the data, we formally estimate equation (2), using self-reported mask usage as the behavioral outcome. 34 notes: the data source is yougov. the outcome is a binary variable taking value 1 if the respondent respectively answered "always" (in the left panel) or "always" or "frequently" (in the right panel) to "thinking about the last 7 days, how often have you worn a face mask outside your home?" the figure plots the estimates from a version of equation (2) where the mask policy variable is replaced by the interaction of the variables corresponding to being in the treatment group (imposed mask mandate) and a series of dummies for each week, ranging from 6 weeks before the mask mandate to 6 weeks after (t = -6 to +5, where t = 0 is the mandate implementation date). the reference point is 1 week before the implementation (t = -1). wild bootstrap (cgmwildboot) standard errors clustered by province with 5000 repetitions are used to construct the confidence intervals. sample weights are used. figure 5 shows a graphical event study analysis on mask mandates and changes in mask usage. the event study approach is appropriate for the mask usage outcome variable, since the policy impact is expected to be immediate, unlike the other outcomes we study, for which any impact is expected to occur with a lag and we use weekly totals or moving averages. we replace the mask policy variable in equation (2) by the interaction of variables corresponding to being in the treatment group (i.e. under a mask mandate), and a series of dummies for each week, ranging from 6 weeks before the mask mandate to 5 weeks after the mask mandate (t = -6 to +5, where t = 0 is the implementation date of the mask mandate). the reference point is one week before the implementation of the mask mandate (t = -1), and we use the same y-axis scale on both panels. the left and right panels of figure 5 present the results from the event study analysis for the "always" and "always" or "frequently" mask usage answers, respectively. we make several observations. first, neither panel shows a pre-trend -the estimates are close to zero before the mask mandates. this addresses the potential concern that provinces that implemented mask mandates may have had a different trend in mask usage than provinces that did not. second, the effect of mask mandates on mask usage is immediate: an increase 24 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . https://doi.org/10.1101/2020.09.24.20201178 doi: medrxiv preprint of roughly 20 percentage points as soon as the mask policy is implemented at (t = 0). third, the effect appears persistent rather than transitory, since mask usage after t = 0 does not revert to its level before t = 0. notes: the time period is april 2 to august 13, 2020. p-values from wild bootstrap (cgmwildboot) standard errors clustered by province with 5000 repetitions are reported in the square brackets. nc denotes national total cases. the data source is yougov. the outcome is a dummy which takes value 1 if the respondent answered "always" to the survey question "thinking about the last 7 days, how often have you worn a face mask outside your home?" sample weights are used. individual characteristics include a gender dummy, age dummy (in years), dummies for each household size, dummies for each number of children, and dummies for each employment status. ***, ** and * denote 10%, 5% and 1% significance level respectively. table 3 displays the estimates on self-reported mask usage (answer "always") in equation (2) along with wild bootstrap p-values clustered at the province level. the odd-numbered columns use lagged cases and lagged case growth at the provincial level as information while the even-numbered columns include in addition lagged cases and case growth at the national level as additional information variables. as in table 1 and table 2 , we present estimates 25 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . without time trend, including cubic time trend (in days), and including week fixed effects. our preferred specification with cubic time trend, column (4) of table 3 , shows that mask mandates are associated with 31.5 percentage point increase in self-reported mask usage (p < 0.001), from a base of self-reported mask usage without mask mandate of 29.8%. 35, 36 these "first-stage" results show that mask mandates exhibit significant compliance in canada and establish a basis for the significant impact of mask mandates on the spread of covid-19 that we find. that said, given that mask mandates do not change everyone's behaviour, our estimates in tables 1 and 2 represent intent-to-treat effects. the full effect of the entire population shifting from not wearing to wearing masks is likely significantly larger. 37 there is a heated debate on whether community use of masks may create a false sense of security that reduces adherence to other preventive measures. we also investigate this question using yougov survey data. as tables a13 and a14 indicate, we find no evidence that mask mandates in canada have had an offsetting effect on other preventive measures such as hand washing, using sanitizer, avoiding gatherings, and avoiding touching objects in public during the period we study. on the contrary, mask mandates may slightly increase social distancing in one out of the eight precaution categories (avoiding crowded areas) (p < 0.10). 38 we evaluate several counterfactuals corresponding to replacing the actual mask policy in a province or canada-wide with a counterfactual policy, including absence of mask mandate. letting t 0 be the implementation date of a counterfactual policy, we set the counterfactual weekly case count, ∆c c it , equal to ∆c it for all t < t 0 . for each date t ≥ t 0 , using the definition of y it from (3), we then compute the counterfactual weekly cases, ∆c c it and the counterfactual 35 similarly, in table a12 , column (4) shows that "always" or "frequent" mask usage increases by 21.5 percentage points. the finding that the increase in mask usage among the "always" respondents is larger than among the "always" or "frequent" respondents is consistent with some people switching from wearing masks "frequently" to "always." 36 hatzius et al. (2020) document that state mask mandates in the us increased mask usage roughly by 25 percentage points in 30 days. the compliance with mask mandates may differ across countries or regions based on social norms, peer effects, political reasons or the consequences of noncompliance (e.g., fines). 37 if we take the increase of about 30 percentage points in reported mask usage induced by mask mandates at face value, the full effect of mask wearing (treatment-on-the-treated effect) would be roughly triple our estimates. it could be larger still if there is desirability bias in answering the mask usage survey question, so that the actual increase in mask use may be smaller than our estimate. 38 consistent with this result, seres et al. (2020) find that wearing masks increased physical distancing based on a randomized field experiment in stores in germany. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . case growth rate, y c it , as follows: whereŷ it is the regression-fitted value of weekly case growth; β m ask 14 is the coefficient estimate on the mask mandate variable mask 14 in baseline specification (4) in table 1 or 2, depending on the counterfactual; mask c 14 is the counterfactual mask policy (e.g. different implementation date, wider geographic coverage or absence of mask mandate); and β log∆c 14 is the coefficient estimate (-0 .227 or -0.209) on lagged cases log(∆c) 14 in table 1 or 2, column 4. the coefficient β log∆c 14 adjusts the counterfactual case growth rate for the negative statistically significant association between the weekly case total two weeks prior and time-t case growth. this effect may be due to people being more careful when they perceive the risk of infection to be higher or less careful vice versa. notes: the left panel assumes that mask mandates were adopted in all phus on june 12 (date of the first mask mandate in on). the right panel assumes that mask mandates were not adopted in any phu. we use the mask estimate (-0.376) from column (4) of table 1. 27 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. notes: the left panel assumes that mask mandates were adopted in all provinces on july 7 (the adoption date in toronto and ottawa). the right panel assumes that mask mandates were not adopted in any province. we use the mask estimate (-0 .376) from column (4) of table 1 . notes: the left panel assumes that mask mandates were adopted in all provinces on july 7 (the adoption date in toronto and ottawa). the right panel assumes that mask mandates were not adopted in any province. we use the mask estimate (-0 .613) from column (4) of table 2 . 28 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . figures 6, 7 and 8 show results from two counterfactual policy evaluations. the first exercise, depicted in the left-hand side panel of the figures, assumes that masks are adopted everywhere at the earliest date observed in the data. specifically, figure 6 considers the counterfactual of all ontario phus adopting mask mandates on june 12, while figures 7 and 8 assume that all provinces adopt a mask mandate on july 7. 39 using our mask policy estimate from table 1, figure 6 shows that an earlier face mask mandate across ontario phus could have lead to an average reduction of about 300 cases per week as of august 13, holding all else equal. for canada as a whole, a nation-wide adoption of mask mandates in early july is predicted to reduce total cases per week in the country by 700 to 1,100 cases on average as of august 13, depending on whether we use the more conservative mask estimate (-0 .376) from column (4) of table 1 (see figure 7 ) or the larger estimate (-0 .613) from column (4) of table 2 (see figure 8 ). in all cases, the indirect feedback effect via β log∆c 14 (lagged cases as information) starts moderating the decrease in cases two weeks after the start of the counterfactual mask policy. in the right-hand side panel of figures 6, 7 and 8, we perform the opposite exercise, namely assuming instead that mask mandates were not adopted in any ontario phu or any canadian province. our estimates imply that the counterfactual absence of mask mandates would have led to a large increase in new cases, both in ontario and canada-wide, especially when using the larger mask coefficient estimate from table 2 (see figure 8 ). finally, in figure b11 in the appendix, we also evaluate the counterfactual in which british columbia and alberta, the third and fourth largest canadian provinces by population, adopt province-wide mask mandates on july 15. the results, using the mask 14 estimate from table 2 , suggest a reduction of about 300 cases per week in each province by mid-august. the counterfactual simulations assume that all other variables, behaviour and policies (except the mask policy and t − 14 cases) remain fixed, as observed in the data. this is a strong assumption, but it may be plausible over the relatively short time period that we analyze. moreover, the counterfactuals assume that regions without a mask mandate would react in the same way, on average, as the regions that imposed a mandate. therefore, these results should be interpreted with caution and only offer a rough illustration and projection of the estimated effect of mask mandates on covid-19 cases. 39 june 12 is the date of the earliest mask mandate in ontario. for the national analysis, july 7, the effective date for toronto and ottawa, is considered ontario's first significant date of mask mandate enactment: phus with earlier mandates account for less than 10% of ontario's population. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . https://doi.org/10.1101/2020.09.24.20201178 doi: medrxiv preprint closing and re-opening sub-periods we investigate whether policy impact varied in different phases of the pandemic by splitting the full sample period into two sub-periods: "closing" (march 11 to may 14) and "reopening" (may 15 to august 13). the dividing date of may 15 (referring to the npis in place around may 1) was chosen because very few policies were relaxed before may 1, and very few non-mask policies were tightened after may 1 in our sample period (see figure 2) . in table a15 , we report estimates and wild bootstrap standard errors using our baseline specification with cubic time trend, separately for the closing and re-opening periods. we find that the imposition of school closures and travel restrictions early in the closing period is associated with a very large subsequent reduction in weekly case growth, as can be also seen on figure b8 -the average observed log growth rate of cases ∆ log(∆c) falls from 2.4 (ten-fold growth in weekly cases) to −0.4 (33% decrease in weekly cases) between march 15 and april 5. long-term care restrictions are also associated with reduced case growth two weeks later during the march to may closing period. we interpret these results with caution, however, since many of these policy measures and restrictions were enacted in a brief time interval during march and there is not much inter-provincial variation (see figure 2 ). no mask mandates were present in the closing period. in the re-opening period, our results in table a15 are in line with our full-sample results for mask mandates and business/gathering regulations (table 2) , with slightly larger coefficient estimates and less statistically significant p-values, possibly due to the smaller sample. travel and school closures are not statistically significant in the re-opening period. this is unsurprising: relaxation of travel policies was minor and endogenous (only re-open to safe areas within canada), and the schools that re-opened (in parts of quebec and, on a part-time basis, in british columbia) did so on voluntary attendance basis, yielding smaller class sizes. we also examine the weekly death growth as an outcome. we only have access to disaggregated deaths data at the province level (not at phu levels in ontario). we thus estimate regression equation (1) using y it = ∆ log(∆d it ) for each province i as the dependent variable. in addition, we use a 28-day lag for the policy, behaviour proxy, and information variables to reflect the fact that deaths occur on average about two weeks after case detection; see appendix d for details and references. 40 40 in table 4 , variable 28 denotes the variable lagged by 28 days. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . table 4 reports the estimates from the same specifications as those for case growth in table 2 . in all specifications, mask mandates are associated with a large reduction in the observed weekly deaths growth rate four weeks later (more than 90 log points, or equivalently more than 60% reduction in weekly deaths). these results are larger than our case growth results, but consistent with them given the substantial uncertainty. see also figure b12 , which plots the average weekly death growth in the provinces without a mask mandate four weeks prior vs. that for ontario, the only province with mask mandate four weeks prior in our sample period. the robustness checks in table a16 , however, show that, unlike for case growth, the mask mandate estimates in table 4 are not robust to weighing by population or to restricting the sample to the largest 4 provinces. this suggests that the estimated effect is largely driven by observations from the small provinces, which have a disproportionately larger number of zero or small weekly death totals. 41 furthermore, given the 28-day lag, there are only 9 days with observations (from ontario only) for which the mask mandate variable takes value of 1. due to these serious data limitations, the relation between mask mandates and covid -19 deaths in table 4 is suggestive at best, and we urge caution in interpreting or extrapolating from these results. that said, our main findings about the growth in cases may have implications about future growth in deaths, particularly if the affected demographics become less skewed toward the young in later periods. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the wearing of face masks by the general public has been a very contentious policy issue during the covid-19 pandemic, with health authorities in many countries and the world health organization giving inconsistent or contradictory recommendations over time. "conspiracy theories" and misinformation surrounding mask wear abound in social media, fuelled by some individuals' perception that mask mandates constitute significant restrictions on individual freedoms. given the absence of large-scale randomized controlled trials or other direct evidence on mask effectiveness in preventing the spread of , quantitative observational studies like ours are essential for informing both public policy and the public opinion. we estimate the impact of mask mandates and other public policy measures on the spread of in canada. we use both within-province and cross-province variation in the timing of mask mandates and find a robust and significantly negative association between mask mandates and subsequent covid-19 case growth -25 to 46% average reduction in weekly cases in the first several weeks after adoption, depending on the data sample and empirical specification used. these results are supported by our analysis of survey data on compliance with the mask mandates, which show that the mandates increase the proportion of reporting as always wearing a mask in public by around 30 percentage points. however, our sample period does not allow us to determine whether their effect lasts beyond the first few weeks after implementation. we conclude that mask mandates can be a powerful policy tool for at least temporarily reducing the spread of mask mandates were introduced in canada during a period where other policy measures were relaxed, as part of the economy's re-opening. specifically, we find that relaxed restrictions on businesses or gatherings are positively associated with subsequent covid-19 case growth -a factor that could offset and obscure the health benefits of mask mandates. past case totals were also found to matter for subsequent outcomes, suggesting that riskier behaviour based on favourable lagged information may limit how low mask mandates and other restrictions -short of a lockdown -can push the number of new cases. we have deliberately abstained from studying the direct economic impacts of , focusing instead on the unique features of the canadian data for identifying the effect of npis, in particular mask mandates, on covid-19 case growth. future research combining epidemiological finding with the economic benefits and costs of various public policies or restrictions would enrich the ongoing policy debate and provide further guidance. 33 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. 38 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (1) and (2) repeat columns (3) and (4) from table 1 where we replace log(0) with -1. columns (3) and (4) replace log(0) with 0, and columns (5) and (6) add 1 to all ∆c it observations. columns (7) and (8) report estimates from a weighted least squares regression with weights equal to the phu population sizes. ***, ** and * denote 10%, 5% and 1% significance level respectively. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . 40 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . (1) and (2) repeat columns (3) and (4) from table 1 . we drop each policy at at time in columns (3)(8) . ***, ** and * denote 10%, 5% and 1% significance level respectively. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . the time period is april 2 to august 13, 2020. p-values from wild bootstrap (cgmwildboot) standard errors clustered by province with 5000 repetitions are reported in the square brackets. nc denotes national total cases. the data source is yougov. the outcome is a dummy which takes one for the respondent who answers "always" or "frequently" to the survey question "thinking about the last 7 days, how often have you worn a face mask outside your home?" sample weights are used. individual characteristics include a gender dummy, dummies for each age (in years), dummies for each household size, dummies for each number of children, and dummies for each employment status. ***, ** and * denote 10%, 5% and 1% significance level respectively. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . notes: the time period is april 2 to august 13, 2020. p-values from wild bootstrap (cgmwildboot) standard errors clustered by province with 5000 repetitions are reported in the square brackets. nc denotes national total cases. the data source is yougov. the outcome is a dummy which takes value 1 if the respondent answered "always" or "frequently" to each survey question in table c4 . sample weights are used. individual characteristics include a gender dummy, age dummy (in years), dummies for each household size, dummies for each number of children, and dummies for each employment status. ***, ** and * denote 10%, 5% and 1% significance level respectively. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the time period is feb 26 to july 30 (two weeks before the march 11 -august 13 sample period). daily province-level data. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . notes: the data source is yougov. the figure plots the average self-reported mask usage by week (the fraction of respondents who answered "always" to the survey question "worn a face mask outside your home") in the provinces with vs. without mask mandates. sample weights used to compute the averages. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . figure b3 : canada -behaviour notes: the behaviour proxy b it is the average of the "retail", "grocery and pharmacy", and "workplaces" google mobility indicators. province-level 7-day moving averages are plotted. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. notes: we plot the coefficient estimates on mask policy, with 95% confidence intervals, from equation (1), for different initial dates of the sample. the initial sample date in the baseline specifications reported in table 1 notes: we plot the coefficient estimates on mask policy, with 95% confidence intervals, in the upper panel and the estimates on business/gathering policy in the lower panel, from equation (1) for different initial dates of the sample. the initial date in our baseline specification (table 2) is march 11. the left panels correspond to column (3) in table 2 ; the right panels correspond to column (4) in table 2 . all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. table 2 ; the right panels correspond to column (4) in table 2 . all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . https://doi.org/10.1101/2020.09.24.20201178 doi: medrxiv preprint figure b8 : canada -weekly cases, deaths and tests (growth rate) 27 week ending preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . https://doi.org/10.1101/2020.09.24.20201178 doi: medrxiv preprint figure b9 : canada -weekly cases, deaths and tests (level) 27 60 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . https://doi.org/10.1101/2020.09.24.20201178 doi: medrxiv preprint figure b10 : canada -daily cases, deaths and tests 27 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . https://doi.org/10.1101/2020.09.24.20201178 doi: medrxiv preprint figure b11 : counterfactuals -mask no mask mandate at t-28 mask mandate at t-28 notes: average log weekly death growth in provinces with vs. without mask mandates 28 days prior. all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . https://doi.org/10.1101/2020.09.24.20201178 doi: medrxiv preprint used hand sanitiser i12 health 6 avoided going out in general i12 health 12 avoided small social gatherings (not more than 2 people) i12 health 13 avoided medium-sized social gatherings (between 3 and 10 people) i12 health 14 avoided large-sized social gatherings (more than 10 people) i12 health 15 avoided crowded areas i12 health 20 avoided touching objects in public (e.g. elevator buttons or doors) notes: the data source is yougov. possible responses to each survey item are "always", "frequently", "sometimes", "rarely", and "not at all". for table a13 , we create a binary variable taking value 1 if the response is "always" and 0 otherwise. for table a14 , we create a binary variable taking value of 1 if the respondent answered either "always" or "frequently" and 0 otherwise. all data used in the paper are available at https://github.com/c19-sfu-econ/data. as discussed in section 3.1, we assume a lag of 14 days between a change in policy or behaviour and its hypothesized effect on weekly case growth, and a lag of 28 days between such a change and its effect on weekly death growth. first, we consider the lag between infection and a case being reported. as most identified cases of in canada are symptomatic, we focus on symptomatic individuals. for most provinces cases are listed according to the date of report to public health. in provinces where the dates instead refer to the public announcement, we shifted them back by one day, as announcements typically contain the cases reported to public health on the previous day. the relevant lag therefore has two components: 2. time between symptoms onset and reporting of the case to public health: the ontario data contain an estimate of the symptom onset date ("episode date") for each case. for our sample period the average difference between the date of report and the episode date is 4.8 days (median: 4 days) including only values from 1 to 14 days, and 6.3 66 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . days (median: 5 days) including only values from 2 to 28 days. we assume that the lags in ontario and in other provinces are similar, and use a value of [5] [6] days between symptom onset and report to public health authorities. adding these together implies that the typical lag between infection and a positive case being reported to public health is around 11 days. second, we consider the effect of weekly averaging on the appropriate lag for our analysis. suppose a policy or behavioural change starts on date t, impacting the daily growth in infections between dates t − 1 and t and in each subsequent day. then, assuming a lag of 11 days between infection and case reporting, case counts c are affected from date t+11 onward. our outcome variable ∆ log(∆c) thus would react to the original policy or behavioral change on date t + 11. the change is complete on t + 23, when the week from t + 17 to t + 23 is compared to the week from t + 10 to t + 16. the midpoint of the change is t + 17. choosing a lag of l days implies that the policy/behaviour variable phases in from t + l to t + l + 6. to match the midpoint of this phase-in to the midpoint of the change in the outcome variable, we set l = 14. the chosen lag matches the lag used by other authors who study policy interventions, e.g., cks (2020). we explore sensitivity to alternative lags in section 4.3. with respect to deaths, our data are, in most cases, backdated (revised by the authorities ex , that is, two weeks longer than our estimate of the time from symptom onset to reporting of a positive test result. we correspondingly set the lag used in our analysis of the death growth rate (section 4.6) to 28 days. 67 all rights reserved. no reuse allowed without permission. preprint (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this this version posted september 25, 2020. . https://doi.org/10.1101/2020.09.24.20201178 doi: medrxiv preprint the case for universal cloth mask adoption and policies to increase supply of medical masks for health workers incubation period of 2019 novel coronavirus (2019-ncov) infections among travellers from wuhan, china bootstrap-based improvements for inference with clustered errors causal impact of masks, policies, behavior on early covid-19 pandemic in the physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and meta-analysis face masks for the public during the covid-19 crisis the effect of large-scale anti-contagion policies on the covid-19 pandemic a contribution to the mathematical theory of epidemics the incubation period of coronavirus disease 2019 (covid-19) from publicly reported confirmed cases: estimation and application respiratory virus shedding in exhaled breath and efficacy of face masks early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia incubation period and other epidemiological characteristics of 2019 novel coronavirus infections with right truncation: a statistical analysis of publicly available case data community use of face masks and covid-19: evidence from a natural experiment of state mandates in the us transmission of sars-cov-2: a review of viral, host, and environmental factors face masks considerably reduce covid-19 cases in germany public responses to policy reversals: the case of mask usage in canada during covid-19 flattening the covid-19 peak: containment and mitigation policies reducing transmission of sars-cov-2 covid-19 us state policy database high contagiousness and rapid spread of severe acute respiratory syndrome coronavirus 2 face mask use and physical distancing before and after mandatory masking: evidence from public waiting lines table 17-10-0009-01 population estimates, quarterly estimates of the severity of coronavirus disease 2019: a model-based analysis weekly epidemiological update, coronavirus disease 2019 (covid-19) estimating clinical severity of covid-19 from the transmission dynamics in wuhan, china log(∆c) -2.545 *** -2.062 *** -1.935 *** -1.537 *** -1.387 ** -0.912 * -1.956 *** -1.504 *** 1 we show mask usage for the u.s. and germany because related work by chernozhukov et al. (1) and (2) repeat columns (3) and (4) from table 2 where we replace log(0) with -1. columns (3) and (4) replace log(0) with 0, and columns (5) and (6) add 1 to all ∆c it observations. columns (7) and (8) report results from a weighted least squares regression with the province populations as weights. finally, columns (9) and (10) (3) and (4) report estimates with lagged weather variables as additional controls. columns (5) and (6) add a "news" variable to the baseline specification (see appendix c for more details). ***, ** and * denote 10%, 5% and 1% significance level respectively. weather -we downloaded historical weather data for the largest city in each province from the weather canada website. the data provide daily information on 11 variables: maximum temperature (c), minimum temperature (c), mean temperature (c), heating degreedays, cooling degree-days, total rain (mm), total snow (cm), total precipitation (mm), snow on the ground (cm), direction of maximum wind gust (tens of degrees), and speed of maximum wind gust (km/h). we only use the temperature and precipitation data in table a11 as possible factors determining outside vs. inside activity.news -we collected data from proquest canadian newsstream, a subscription service to all major and small-market daily or weekly canadian news sources. we recorded the number of search results for each day from feb 1, 2020 to aug 20, 2020 by searching the database for the keywords "coronavirus" or "covid-19". we only counted the results with source listed as "newspaper" since other sources, such as blogs or podcasts, tend to duplicate the same original content. key: cord-035203-dnoc0xcv authors: vaňková, eva; kašparová, petra; khun, josef; machková, anna; julák, jaroslav; sláma, michal; hodek, jan; ulrychová, lucie; weber, jan; obrová, klára; kosulin, karin; lion, thomas; scholtz, vladimír title: polylactic acid as a suitable material for 3d printing of protective masks in times of covid-19 pandemic date: 2020-10-29 journal: peerj doi: 10.7717/peerj.10259 sha: doc_id: 35203 cord_uid: dnoc0xcv a critical lack of personal protective equipment has occurred during the covid-19 pandemic. polylactic acid (pla), a polyester made from renewable natural resources, can be exploited for 3d printing of protective face masks using the fused deposition modelling technique. since the possible high porosity of this material raised questions regarding its suitability for protection against viruses, we have investigated its microstructure using scanning electron microscopy and aerosol generator and photometer certified as the test system according to the standards en 143 and en 149. moreover, the efficiency of decontaminating pla surfaces by conventional chemical disinfectants including 96% ethanol, 70% isopropanol, and a commercial disinfectant containing 0.85% sodium hypochlorite has been determined. we confirmed that the structure of pla protective masks is compact and can be considered a sufficient barrier protection against particles of a size corresponding to microorganisms including viruses. complete decontamination of pla surfaces from externally applied staphylococcus epidermidis, escherichia coli, candida albicans and sars-cov-2 was achieved using all disinfectants tested, and human adenovirus was completely inactivated by sodium hypochlorite-containing disinfectant. natural contamination of pla masks worn by test persons was decontaminated easily and efficiently by ethanol. no disinfectant caused major changes to the pla surface properties, and the pore size did not change despite severe mechanical damage of the surface. therefore, pla may be regarded as a suitable material for 3d printing of protective masks during the current or future pandemic crises. covid-19 (coronavirus disease 2019) is the designation of the disease caused by the sars-cov-2 infection. the world health organization (who) declared this epidemic a global pandemic affecting the whole world on 11 march 2020. the infection by sars-cov-2 was confirmed for the first time in wuhan, china, but had a huge impact also in europe and later in north and south america. lombardy, italy was the most severely affected region in europe. due to the risk of health care system collapse, the italian government ordered a nationwide lockdown (spinelli & pellino, 2020) . several studies showed that sars-cov-2, similarly to sars-cov-1, remains infectious for hours and days in aerosols and on surfaces, respectively (chin et al., 2020; kampf et al., 2020; van doremalen et al., 2020) , emphasizing the need for efficient virucidal disinfection. the number of patients suffering from covid-19 disease and the enormous rate of infection spread caused serious complications in many countries, including a desperate lack of protective equipment (swennen, pottel & haers, 2020) . sufficient production and distribution of protective equipment has been crucial for sustaining patient care during the pandemic. the current unsatisfactory situation regarding protective equipment in the usa has been described by ranney, griffeth & jha (2020) . because of the lack of protective equipment including face masks, extended manufacturing facilities have become very important for supporting the health care system. in this regard, the production of protective masks using 3d printing has proven very promising. this technology, often based on fused deposition modelling (fdm) due to its cost and technical benefits, has found various applications in the manufacturing of medical devices such as prosthetic and dental implants or scaffolds in tissue engineering (roopavath & kalaskar, 2017; tack et al., 2016) . the properties of 3d-printed objects render this technology attractive for manufacturing of protective masks. fdm provides adequate dimensional control, good surface finish and adaptability to use a variety of thermoplastic polymer filaments. the technology is based on high-temperature sintering of filaments and subsequent solidification of the printed product at room temperature. the polymers most commonly used for fdm are acrylonitrile-butadiene-styrene copolymers, polycarbonate, polyethylene terephthalate glycol (petg) and polylactic acid (pla) (chadha et al., 2019; ngo et al., 2018) . due to its unique properties, pla is one of the most attractive materials for 3d printing. its main advantages include low printing temperatures of 200-210 c, smooth appearance, low toxicity and favorable mechanical properties, especially a low warping effect and high geometric resolution (pajarito et al., 2019; vicente et al., 2019) . pla is a biodegradable linear aliphatic polyester produced from renewable natural resources such as corn, wheat or sweet sorghum (nampoothiri, nair & john, 2010) . nagarajan, mohanty & misra (2016) comprehensively reviewed its properties and applications. this polymer is produced by acid-catalyzed polycondensation of lactic acid monomers. lactic acid of any chirality can be used, resulting in either poly-l-lactic acid, poly-d-lactic acid or poly-l,d-lactic acid (consisting of both isomers). since l-lactic acid is the most common isomer in nature and is easily produced by lactic fermentation of various bio-wastes by bacteria (e.g., lactobacillus spp.), it is also the most commonly used precursor for pla manufacturing. the possibility of biotechnological production of the monomer significantly decreases its price, making the production of pla very cheap. the glass transition temperature of pla ranges between 50 and 80 c, and the melting temperature reaches approximately 175 c. due to its natural precursor, pla is easily biodegradable, for example, by thermal decomposition, enzymatic digestion, oxidation or photolysis. ghorpade, gennadios & hanna (2001) studied the outcome of placomposting for 90 days and found that the compound was degraded by 70 %. the use of pla is limited by its poor thermal stability and easy hydrolysis-it degrades more easily than other aliphatic polyesters. nevertheless, pla has found many applications in diverse areas including the packaging industry as a food packaging polymer for short shelf life products, the pharmaceutical industry for controlled drug delivery formulations and for tissue regeneration, and agriculture for better herbicide delivery management without negative effects on crop yield (auras, harte & selke, 2004; aziz, haq & raina, 2020; farto-vaamonde et al., 2019) . protective masks made by 3d printing from pla are designed for repeated use, requiring frequent cleaning and disinfection. the low glass transition temperature and relatively low melting point of pla makes heat sterilization in an autoclave at 121 c impossible (mckeen, 2014) . the polymer can be sterilized using ethylene oxide, gamma radiation (fleischer et al., 2020) or dry heat below 80 c for no more than 20 min (zou et al., 2011 ). fleischer et al. (2020 examined the changes of pla properties after cleaning with chemical disinfectants such as cidex opa (johnson & johnson) or chlorine solutions. although these substances caused minor changes in stiffness and strength of 3d-printed pla, 3d printing at appropriate conditions makes pla objects mechanically amenable to cleaning and reuse. however, surface porosity of 3d-printed pla medical tools should be minimized to prevent exposure of users to residual disinfectants by inhalation or skin contact. oth et al. (2019) studied pla object sterilization by low-temperature hydrogen peroxide gas plasma in the commercially available sterrad ò apparatus (johnson & johnson). they observed only sub-millimeter deformations induced by this process, rendering it suitable for sterilization in different areas including surgical applications. in contrast to conventional steam autoclaving, sterilization by hydrogen peroxide prevents deformation of 3d-printed objects made from pla or petg. swennen, pottel & haers (2020) presented a prototype of reusable custom-made 3d-printed face masks (produced by a selective laser sintering technique) from polyamide composite components. the authors proposed cleaning by 15 min exposure to a broad-spectrum antimicrobial solution, anios clean excel, containing didecyldimethylammonium chloride and chlorhexidine digluconate. nevertheless, material leakage and virus decontamination of the reusable face mask components have not been tested upon one or more disinfection cycles. in the present study, we have investigated fdm 3d-printed pla structure and porosity after exposure to common chemical disinfectants including ethanol, isopropanol and a commercial disinfectant containing sodium hypochlorite, which are easily accessible. in addition, we examined the efficiency of pla disinfection after artificial contamination with bacteria (staphylococcus epidermidis, escherichia coli), a yeast fungus (candida albicans), viruses (sars-cov-2 and human adenovirus -hadv) or natural contamination by wearing the masks. polylactic acid (pla) was purchased in the form of filament for fdm 3d printing from shenzen creality 3d technology co., ltd, china. protective masks, circular plates (diameter of 10 cm and height of 0.2 cm, printed vertically) and square carriers (1 × 1 cm, 0.2 cm high) ( fig. 1) were prepared using a 3d printer (prusa i3 mk3, czech republic). the printing template was designed with trimble sketchup pro, exported in a stereolithographic (stl) file (freely available at https://www.facebook.com/groups/ 1346383268879783/files/) and used to print the objects of investigation. the printing parameters were as follows: layer height = 0.3 mm, shell thickness (perimeter) = 0.4 mm, bottom/top thickness = 0.2 mm, fill density = 10 %, print speed = 90 mm/s, extrusion temperature = 215 c, platform temperature = 60 c, filament flow = 95%, machine nozzle size 0.4 mm, the infill pattern was grid (i.e., linear tilted 45 ) and the total layers = 338. visualization of pla mask structure using scanning electron microscopy the structure and porosity of pla 3d-printed masks were examined using a scanning electron microscope (sem) nova nanosem 450 (fei, usa). approximately 1 × 1 cm pieces cut from printed masks were completely air-dried and visualized by sem. since the material is very sensitive to electron exposure, mild conditions had to be used, that is, voltage of 5 kv and low vacuum. images of each visualized position were captured by lvd detector at gradual magnifications 2,000×, 1,000×, 500×, 100× (focusing on identical position), dwell time 5 µs and spot size 4.5. the size of the pores between pla filaments was measured and marked using a sem operating software (xt microscope control v6.3.4 build 3233), provided by the sem manufacturer (fei, usa). the sem images shown in this study were selected as representative visualizations of the pla microstructure. the sem analysis merely illustrates the 3d-printed pla surface morphology, and gap width measurements are not analyzed statistically. visualization of pla mask structure under stress conditions using scanning electron microscopy to investigate the impact of possible stress factors for pla masks, cleaning with chemicals was performed and exposure to wearing-associated contamination was simulated, as outlined below. the effect of immersing in three chemical disinfectants (96% ethanol, 70% isopropanol and the commercial disinfectant and bleach savo original, unilever čr s.r.o., czech republic containing 0.85% sodium hypochlorite diluted with water (2:9)) was tested by repeated (5 × 15 min) cycles and long-term (24 h) exposure. the simulation of human impact on the pla structure was performed as follows: extensive exposure to fingers (to simulate incorrect application of the mask), abrasion with paper (minor mechanical stress) and dining fork (strong mechanical stress), immersion in 1.9% sodium chloride solution for 4 h (to simulate perspiration). short rinsing with 100% acetone was examined to investigate its effect on pla surface properties. after each treatment, completely dried pla carriers were examined using sem, as described above. surface contamination (and potential surface penetration) with infectious agents was simulated by an aerosol generator and a photometer (lorenz meβgerätebau fmp 03) with a differential pressure sensor (fig. s1) , providing a suitable test system with stand for facial masks and flat filter materials. the device was certified as a test system according to the standards en 143 (respiratory protective devices-particle filters-requirements, testing, marking), and en 149 (respiratory protective devices-filtering half masks to protect against particles-requirements, testing, marking). a sample of the pla material was attached in the standardized testing cartridge and was sealed with silicone to prevent false positive detection of penetrating particles passing along the edge of the pla panel (fig. s2 ). the cartridge was mounted into the lorenz meβgerätebau fmp 03 device, between the aerosol generator and photometer. the aerosol generator produced a defined amount of aerosolized paraffin oil, the test system passed it through the material, and the photometer situated on the other side of the pla sample measured the aerosol concentration, thereby indicating the retention efficiency. an integrated differential pressure sensor was used to determine the pressure loss during passage through the sample. the particle size distribution was approximately 0.1-2 µm (geometric mean 0.44 µm), which is close to the most frequently observed penetrating particle size (fig. s3 ). the output of the aerosol generator was set to 150% with flow 95 l/min, atomizer pressure 5 bar and oil temperature 60 c. the test was performed for 270 s. wild strains of s. epidermidis, e. coli and c. albicans were used as representatives of gram-positive and gram-negative bacteria or yeast fungus, respectively. the concentration of bacteria was adjusted to approximately 1 × 10 7 colony forming units (cfu) per ml, the fungus concentration was 1 × 10 6 cfu/ml. each pla carrier with a size of 1 × 1 cm was contaminated with 10 µl of microbial suspension applied to the surface of carriers in 1 µl droplets for 1 h. the disinfection of contaminated carriers was carried out by immersing in three ml of 96% ethanol, 70% isopropanol, or 0.85 % sodium hypochlorite (savo original, unilever čr s.r.o., czech republic) for 15 min. after evaporation of disinfectant solutions, the carriers were immersed in one ml of sterile 0.9% saline, vortexed, and the obtained suspensions were inoculated onto appropriate agar plates. blood agar was used for s. epidermidis, müller-hinton (oxoid, czech republic) agar for e. coli and sabouraud agar (oxoid, czech republic) for c. albicans. samples not exposed to treatment by disinfectants were used as controls. the inoculated plates were incubated at 37 c for 48 h. each experiment was done in triplicate, and results were obtained by counting the average cfu/ml. sars-cov-2, the causative agent of the covid-19 pandemic, was isolated in a biosafety level 3 laboratory from a nasopharyngeal swab by inoculating vero ccl81 cells (ecacc 84113001) and subsequent expansion by two additional passages in vero ccl81 cells. passage 3 was cleared by centrifugation at 1000 g for 5 min, passed through a 0.45 µm filter, and stored at −80 c until use. in addition to sars-cov-2, inactivation of a stable dna virus, the human adenovirus 2 atcc vr-846 (hadv) obtained from the american type culture collection (atcc) was assessed. similar to the previous set of experiments, pla carriers of 1 × 1 cm size were contaminated with 20 µl of a sars-cov-2 suspension displaying a median tissue culture infectious dose (tcid50) of 10 6 iu/ml, which was applied to the surface of carriers in 1 µl droplets. an additional set of carriers was covered with 50 µl of hadv suspension (10 6 virus copies) spread evenly over the entire surface. the contaminated carriers were then immersed in 96% ethanol, 70% isopropanol or 0.85% sodium hypochlorite for 15 min. subsequently, residual viruses-if present-were washed from the dried surface using 180-200 µl pbs. the solution was used directly for infection of vero-e6 cells (atcc crl-1586), in case of sars-cov-2, or a-549 human lung carcinoma cells (dsmz acc107 from german collection of microorganisms and cell cultures), in case of hadv, respectively. recovered sars-cov-2 was titrated by an immunofluorescence (if) assay using a 1:2.5 serial dilution of vero-e6 cells starting from 10 µl. vero-e6 cells were incubated for 72 h at 37 c in a co 2 incubator prior to the if assay. briefly, medium was washed out, cells were fixed using 4% paraformaldehyde (pfa), cell membranes were perforated with 0.2% triton-x100, and sars-cov-2 was labeled with primary mouse anti-sars-cov-2 antibody. secondary anti-mouse antibody was conjugated with a cy3 fluorophore and a fluorescent microscope (olympus ix 81, germany) was used for signal detection. in the case of hadv, serial dilutions of virus inoculum were used to infect a-549 cells and the cytopathic effect (cpe) was determined using motic ae21 inverted phase contrast microscope (zeiss, germany). the titers of both recovered viruses infection particles were determined as tcid50 and calculated using the spearman-kärber method (kärber, 1931; spearman, 1908) . in addition, recovered hadv genome copies were determined by real-time quantitative pcr (rq pcr) as described previously (lion et al., 2003) using the abi prism fast 7500 instrument (thermo fisher scientific, ma, usa). to investigate the feasibility of disinfecting pla protective masks in practical use, three volunteers wore the protective masks of the same type for 4 h. thereafter, smears from one half of the inner (approximately 80 cm 2 ) or outer surface (approximately 83 cm 2 ) of each mask were performed using sterile cotton swabs. these samples served as a control for natural mask contamination by manual handling, direct skin contact and exhalation. each cotton swab was transferred into one ml of 0.9% saline in a microtube, vortexed and inoculated onto a blood agar plate. thereafter, the filters were removed from masks and the pla skeletons of the masks were immersed in 96% ethanol for 15 min. after ethanol evaporation, cotton swab smears were taken from the second halves of the inner and outer mask surfaces, inoculated onto agar plates, and incubated at 37 c for 48 h. the results were averaged and expressed as cfu/ml. the structure and porosity of pla masks produced by 3d printing were investigated by sem. scanning electron micrographs of gaps between the pla filaments were captured at four different magnifications (fig. 2) . the pla filament size determined was 312.8 µm (fig. s4 ) and its surface appeared macroscopically very smooth ( fig. 2a) . further magnification showed only slight roughness of the surface and very small gaps between filaments (figs. 2b and 2c). additional increase of magnification revealed connecting filaments of pla, resulting from the high temperature during 3d printing, with only very small pores (6.049 µm in size) in between. the pores appeared to be completely closed deeper in the carrier, as observed at the highest magnification used (2,000×) (fig. 2d ). vaňková (2020) to further test whether the pores were indeed closed and prevented particles from passing through the printed mask, we determined the number of paraffin oil aerosol particles displaying a size of 0.1-2 µm using the aerosol generator and photometer, certified as a test system according to the common standards. maximum pressure loss of the generated aerosol was detected, and absolutely no penetration occurred even though the pla sample was printed with a diameter of 10 cm (corresponds approximately to the printed height of the masks) in the vertical position, simulated printing at a lower temperature in the upper layers (on the z-axis). effect of ethanol, isopropanol and sodium hypochlorite on disinfection of pla material contaminated with bacteria, yeast fungus or viruses the results of disinfection of artificially contaminated pla are summarized in tables 1 and 2 . although the untreated pla carriers were contaminated by highly concentrated bacterial suspensions of 1 × 10 5 cfu/ml, complete decontamination by all disinfectants used was achieved. single colonies were observed in the samples of s. epidermidis and e. coli disinfected by isopropanol, but these isolated findings can reasonably be considered a contamination that occurred after treatment of the samples. the disinfection of pla carriers contaminated with c. albicans (4 × 10 4 cfu/ml) was complete in all cases. titers of sars-cov-2 and hadv recovered from disinfected or untreated carriers were determined by if-and cpe-based assays, respectively. all disinfection agents tested showed complete virucidal effects against sars-cov-2. disinfectants per se exhibited a cytotoxic effects on vero-e6 cells (table s1 ), but this effect was eliminated by serial dilutions during virus titer determination. hadv infectivity was reduced by ethanol and isopropanol, and completely abolished by sodium hypochlorite. similar trends were observed by rq-pcr performed for detecting the hadv genome copy numbers (table s2 ). the effect of disinfectants on the pla structure was investigated using sem. pla structure, gaps between filaments, and the structure of pores after five 15 min cycles of immersing the carrier in different disinfectants are shown in fig. 3 . treatment with ethanol ( fig. 3b ) resulted in slight melting of the pla filaments, as compared with untreated pla (fig. 3a) . the overall pla structure and surface did not change, but, interestingly, the gap size between the filaments was reduced from the original 6 µm to approximately 850 nm (fig. 3b ). this indicates that ethanol treatment may improve the pla mask properties with regard to structure density. similarly, isopropanol treatment did not significantly affect the pla structure (fig. 3c ). only slight melting was detectable, resulting in decreased gap size to 3.3-4 µm, in comparison to 6 µm in control samples. moreover, the surface of filaments remained undamaged. figure 3d depicts the effect of sodium hypochlorite, which did not alter the surface of filaments, but precipitated disinfectant filled the gaps between them, while the gap size remained almost the same as in the control sample (5-7 µm). long-term treatment of pla by immersion in disinfectants for 24 hours was also investigated using sem (fig. 4) . the effect of long-term treatment with ethanol ( fig. 4b ) was similar to repeated exposure to sodium hypochlorite (fig. 3d) , that is, the gaps between filaments were significantly enlarged to 23.84 µm (fig. 4b ), possibly filled with etched polymer. investigation of aerosol particle passage through the pla material after 24 hours in ethanol confirmed that the enlarged gaps were sealed, as no penetration was detected. pla melting was also observed after prolonged isopropanol treatment (fig. 4c) . the gaps between filaments were sealed with the polymer in an irregular manner, resulting in variable gap sizes ranging from 1.3 to 4.1 µm. as in all previous tests with ethanol, the surface of pla filaments remained unaffected. in contrast, long-term treatment with sodium hypochlorite damaged the surface of pla filaments and revealed precipitation of the disinfectant on the surface (fig. 4d) . similarly to short treatment with sodium hypochlorite, the gaps between filaments, ranging from 2 to 3.5 µm, were completely filled with precipitated sodium hypochlorite (fig. 3d) . to complement the results of disinfection upon artificial contamination (tables 1 and 2) , disinfection of pla masks after natural use was investigated. the disinfection efficiency with ethanol (96%) is summarized in table 3 . the microbial load detected on the inner surface of untreated masks varied significantly between different users, ranging from hundreds to thousands cfu/ml. despite this variation, an average of 7 cfu/ml remained detectable after immersing the masks in ethanol for 15 minutes (short rinsing with ethanol was not sufficiently effective; fig. s5 ). on the outer surface of untreated masks, 50-150 cfu/ml were detected, and an average of 2 cfu/ml remained detectable after disinfection (fig. 5 ). the impact on the pla material by finger contact, abrasion by paper or metal and treatment by sodium chloride solution (mimicking perspiration) was analyzed using sem (fig. 6) . although fingers may be greasy or sweaty, the contact did not cause any marks or alterations on the pla surface (fig. 6a) . similarly, gentle mechanical abrasion with paper did not affect the material (fig. 6b ). by contrast, intensive mechanical scraping with a dining fork significantly damaged the pla structure (fig. 6c) , leading to compression of pla filaments, reduction of inter-filament gaps, and shedding of pla pieces (fig. 6d) . however, neither loosening of filaments, nor increase in gap size or other deformations were observed. soaking in sodium chloride solution did not affect the structure, but salt crystals were present in the gaps between filaments (fig. 6e ). in addition, the effect of acetone, which is known to damage pla, was evaluated. virtually no gap was visible between filaments upon treatment, indicating that even short exposure to acetone smoothens the structure and seals the pores (fig. 6f ). the unexpected and sudden spread of sars-cov-2 infection, which resulted in the covid-19 pandemic, has led to a desperate shortage of personal protective equipment, especially among the frontline workers. because of this problem, many people started helping each other by manufacturing facial protection equipment from commonly available resources. an intriguing possibility is the production of protective face masks using fdm, the most widespread technique of 3d printing. a variety of polymers are suitable for fdm, including biodegradable pla as the most affordable and environmentally friendly material because of its natural origin (ngo et al., 2018) . despite the potential benefits, the suitability of pla-based materials for protection against viruses was questioned due to their possible high porosity. to the best of our knowledge, this report provides the first data addressing this issue by testing 3d-printed pla masks (fig. 1) . the surface and other mechanical properties of products made from pla or composite filaments were investigated previously (graupner, herrmann & müssig, 2009; chi et al., 2018; ivanov et al., 2019; wang et al., 2016) . however, the microstructure of 3d-printed pla objects is highly dependent on the printing parameters, and it is not possible to predict the structure and porosity of a particular object based on published data. to investigate the surface properties of protective face masks made from pla, examination of structure and porosity is required. we showed by sem that 3d-printed pla masks have a compact structure, with small gaps between filaments. the gaps between individual filaments were 6 µm wide, but higher magnification showed that the pores were not continuous within the pla carrier (fig. 2d ) and were actually completely closed. this finding was supported by measurements of the filtering efficiency of pla, which revealed completely blocked passage of nanometer-sized paraffin aerosol particles. the mask material can therefore be considered impermeable for particles displaying the size range tested, including the fungus, bacteria, and viruses investigated. in combination with the obligatory single-use filters complying with ffp2/3 standards, which are inserted into the mask, spreading of the smallest viruses can also be prevented. moreover, short exposure to acetone resulted in smoothening of the pla surface (fig. 6f) . a similar 3d-printed reusable face mask prototype was reported by swennen, pottel & haers (2020) . the material (polyamide composite) and the printing method used (selective laser sintering technique) differ from the approach presented, but it provided a proof of principle for 3d printing of individualized 3d face masks with ffp2/3 filter membranes as a feasible and valuable alternative source for protective equipment. however, the authors of the cited study did not perform any virus decontamination testing of the reusable components of the face masks and were hence unable to assess the impact of repeated cycles of disinfection on the properties of the material. it was important therefore to determine the possibility of disinfecting the reusable face mask matrix. while sars-cov-2, being an enveloped rna virus, belongs to the less challenging pathogens in terms of disinfection, hadv (non-enveloped dna virus) is highly resistant to commonly used disinfectants (gordon et al., 1993; lion & wold, 2020) . adenoviruses mostly cause infections with only mild symptoms in immunocompetent hosts (lion, 2019) , but due to their exceptional stability provide a perfect model for testing the inactivation efficiency. in addition, we examined the disinfection of pla material from contamination with bacteria (s. epidermidis and e. coli) and yeast fungus (c. albicans). these microorganisms are part of the human microbiome and their persistence on the protective mask surface poses a risk for infection and a health threat to mask users , peerj, doi 10.7717/peerj.10259 14/20 (fisher & shaffer, 2014) . all bacterial and fungal microorganisms studied were successfully disinfected using either 96% ethanol, 70% isopropanol or 0.85% sodium hypochlorite, after immersing contaminated pla carriers in the respective disinfectant for 15 min (table 1) . ethanol disinfected the pla masks contaminated from using by humans (fig. 5) . in comparison to bacteria or fungi, viruses tend to be 1-2 orders of magnitude smaller, making them prone to enter deep into pores of the pla material. nevertheless, our data show that efficient disinfection of the pla carriers from virus contamination is possible, as all tested disinfectants completely inactivated sars-cov-2 (table 2) . treatment with sodium hypochlorite for 15 minutes also completely inactivated the highly resistant hadv, while ethanol and propanol only led to reduced loads of infectious virus (table 2 ). these data are in agreement with the reported sensitivity of both sars-cov-2 (chin et al., 2020; kampf et al., 2020) and hadv to specific disinfectants (gordon et al., 1993; lion & wold, 2020) . the present findings therefore provide evidence that pla material disinfection can be performed with comparable efficiency to other surfaces by appropriate exposure to individual disinfectants. the results obtained can conceivably also help design efficient disinfection protocols for protective face masks made from different materials. fleischer et al. (2020) examined the changes of pla material after cleaning with chemical disinfectants (cidex opa, johnson & johnson and chlorine solutions), revealing mild alterations in the stiffness and strength of 3d-printed pla samples. however, the authors concluded that high-quality 3d-printed surfaces generated with appropriate printer settings permit cleaning and reuse of 3d-printed medical tools, without compromising their mechanical properties. the authors also stated that immersion in cleaning agents can lead to their absorption into the pla structure. thus, additional research is needed to establish efficient and safe chemical cleaning of various 3d-printed surfaces, to prevent health risks associated with tactile and inhalation exposure to chemically cleaned materials. in general, we observed that five cycles of pla treatment for 15 min with alcoholbased disinfectants resulted in decreased gap size between pla filaments, without any remnants of disinfectant visible by sem. by contrast, sodium hypochlorite precipitate was retained in the pla structure, filling the gaps between pla filaments. disinfection of pla masks with 0.85% sodium hypochlorite therefore requires further medical investigation to determine whether exposure to the precipitate might be associated with any health risks. long-term (24-h) treatment of pla material with disinfectants resulted in partial melting of the filaments, but no erosions of the material were observed (fig. 4) . ethanol seems to be best suited for the disinfection of pla masks because it evaporates and does not require removal by rinsing. moreover, the barrier properties of the mask were not compromised even after long-term exposure, as determined by aerosol challenge. although the surface of protective equipment should remain intact, inadvertent contacts with the hands and fingers often occur, and the possibility of inappropriate handling has to be considered. the pandemic setting requires medical staff to wear extensive protective equipment (e.g., overalls, gloves, protective shields and face masks). such equipment, together with high workload and stress, increases the body temperature and leads to excessive sweating. we mimicked such conditions by mechanical and chemical treatment in order to evaluate alterations of the protective masks. touching the surface of the pla material with fingers had no impact, but intensive mechanical stress caused alteration of the pla filament surface, without affecting the inter-filament gap area. treatment with sodium chloride (imitating perspiration and sweat) showed salt crystallization in the gaps between filaments (fig. 6e) . crystallized salt compounds, such as sodium chloride or sodium hypochlorite (figs. 3d and 4d), can cause discomfort by skin irritation and itching. this issue was described in detail by payne (2020) and wollina (2020) who stated that especially front-line workers obliged to wear a single face mask all day suffer from these problems. the exploitation of pla may solve this issue, because the fast and cheap manufacturing of protective masks made from this material permits production on a large scale, thereby facilitating more frequent mask changes. additionally, 3d-printed protective pla masks are biodegradable, with relatively short decomposition time, thereby providing an environmentally friendly solution. this study shows that pla material is suitable for protection against various microorganisms as it is not permeable for submicroscopic particles. pla can be efficiently disinfected from bacteria, yeast fungus, and sars-cov-2 by commonly available chemical disinfectants such as ethanol, isopropanol or sodium hypochlorite. however, contamination with hadv, a highly resistant representative of non-enveloped viruses, could only be completely removed with sodium hypochlorite. pla material is not altered by the immersion in disinfectant or by manual handling. possible skin irritation after the use of certain disinfectants needs to be carefully evaluated. single-use filters meeting the ffp2/3 standards are inserted into the mask structure and will be subject of further research and optimization. overall, pla can be recommended as suitable material for the manufacturing of protective face masks at times of epidemic spread of infections, such as the ongoing covid-19 pandemic. an overview of polylactides as packaging materials effect of surface texturing on friction behaviour of 3d printed polylactic acid (pla) effect of fused deposition modelling process parameters on mechanical properties of 3d printed parts effect of high pressure treatment on poly(lactic acid)/nano-tio2 composite films stability of sars-cov-2 in different environmental conditions post-manufacture loading of filaments and 3d printed pla scaffolds with prednisolone and dexamethasone for tissue regeneration applications considerations for recommending extended use and limited reuse of filtering facepiece respirators in health care settings the effect of chemical cleaning on mechanical properties of three-dimensional printed polylactic acid laboratory composting of extruded poly (lactic acid) sheets prolonged recovery of desiccated adenoviral serotypes 5, 8, and 19 from plastic and metal surfaces in vitro natural and man-made cellulose fibre-reinforced poly (lactic acid)(pla) composites: an overview about mechanical characteristics and application areas pla/graphene/mwcnt composites with improved electrical and thermal properties suitable for fdm 3d printing applications persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents beitrag zur kollektiven behandlung pharmakologischer reihenversuche adenovirus persistence, reactivation, and clinical management molecular monitoring of adenovirus in peripheral blood after allogeneic bone marrow transplantation permits early diagnosis of disseminated disease cold atmospheric plasma (cap) surface nanomodified 3d printed polylactic acid (pla) scaffolds for bone regeneration challenges of covid-19 pandemic for dermatology effect of wet-heat and dry-heat processing on mechanical properties of pla fibers we thank the volunteers from the organization called "3d tiskem proti viru" (eng. version "3d printing against the virus") as well as pavel kubíček, who printed 3d protective masks for people free of charge during the covid-19 pandemic. we also thank václav čeřovský and jiří rybáček from iocb of the cas and avec chem s.r.o. for providing the laboratory environment and equipment enabling the project to be conducted. the authors received no funding for this work. the authors declare that they have no competing interests. the following information was supplied regarding data availability: raw data depicting background microbial experiments and from sem images are available in the supplemental files. supplemental information for this article can be found online at http://dx.doi.org/10.7717/ peerj.10259#supplemental-information. key: cord-134278-pe41vebc authors: kuhl, niklas; martin, dominik; wolff, clemens; volkamer, melanie title: "healthy surveillance": designing a concept for privacy-preserving mask recognition ai in the age of pandemics date: 2020-10-20 journal: nan doi: nan sha: doc_id: 134278 cord_uid: pe41vebc the obligation to wear masks in times of pandemics reduces the risk of spreading viruses. in case of the covid-19 pandemic in 2020, many governments recommended or even obligated their citizens to wear masks as an effective countermeasure. in order to continuously monitor the compliance of this policy measure in public spaces like restaurants or tram stations by public authorities, one scalable and automatable option depicts the application of surveillance systems, i.e., cctv. however, large-scale monitoring of mask recognition does not only require a well-performing artificial intelligence, but also ensure that no privacy issues are introduced, as surveillance is a deterrent for citizens and regulations like general data protection regulation (gdpr) demand strict regulations of such personal data. in this work, we show how a privacy-preserving mask recognition artifact could look like, demonstrate different options for implementation and evaluate performances. our conceptual deep-learning based artificial intelligence is able to achieve detection performances between 95% and 99% in a privacy-friendly setting. on that basis, we elaborate on the trade-off between the level of privacy preservation and artificial intelligence performance, i.e. the"price of privacy". the covid-19 disease has evolved into a global pandemic at the beginning of 2020. in order to fight the spread of the virus, different measures, so-called non-pharmaceutical interventions (npis), were taken. one of these measures, which a large share of countries adopted, was the recommendation to wear masks in public spaces [1] . for our work, we define public spaces as any inside or outside area which is generally accessible to people, including publicly operated areas like libraries, tram stations, or public authority buildings, but also privately owned spaces, including restaurants or stores. while it is discussed controversially how high the impact of such a policy is, greenhalgh et al. (2020) [2] conclude that it does help in reducing the viral transmission. for instance, the czech republic was one of the first european countries to enforce mask wearing and first analyses point towards that npi having a major impact on the low number of covid-19 cases [3] . however, it remains of interest whether citizens comply with the directive to wear masks for various reasons-including hesitation to get more evidence whether the mask policy contributes successfully to contain the pandemic, for enforcement reasons and/or to fine none-compliance. while manual inspections, e.g., at the entrance of restaurants or stores, are a possibility, these actions require manual labor, do not scale well and are difficult to enforce on larger spaces. in order to allow for an automated examination of the compliance, one could imagine to use surveillance solutions in combination with artificial intelligence (ai) [4] . while this solution entails many upsides, e.g., scalability and automation capabilities, it needs to be in-line with the privacy regulations such as the general data protection regulation (gdpr) and it needs to be understood by citizens to trust and accept the approach: the protection of personal data, e.g., video streams revealing individuals' faces, is regionally required by legal regulations, such as the gdpr in the european union [5] 1 . as numerous studies show, people feel more insecure when their personal steps are highly traceable and they compromise on their privacy while being recorded [6, 7, 8] . therefore, we propose an end-to-end ai-based surveillance artifact which ensures both (a) privacy and (b) high performance of mask recognition. the proposed solution could be used in diverse application scenarios, for instance to contribute to a rigorous reporting of mask coverage used for research purposes. for instance, it could be implemented as a monitoring capability for impact analyses. as simulation models of pandemics depend on a multitude of parameters as input, a precise assessment of the mask coverage would prove helpful and could improve predictions of pandemic developments, e.g. to analyze the effectiveness of npis [9] . on another note, it could be implemented for private store owners, e.g. to ensure a rigorous reporting of mask coverage to authorities in their privately-owned spaces. note, one aspect we do not regard in this work are countermeasures if citizens or customers do not comply with wearing a mask, as we solely propose a monitoring option at this stage. with our research, we contribute to the body of knowledge with three core aspects: first, we develop a novel artifact which can be utilized to allow for a privacy-preserving monitoring of mask coverage during a pandemic. second, we evaluate different design choices on how to build the artifact and elaborate on their performances, strengths and weaknesses. third and finally, we theorize on the trade-off between privacy preservation and ai performance-as ai performance decreases with increased privacy preservation and vice-versa. as an overall research design, we choose design science research (dsr) and base our approach on hevner and chaterjee (2010) [10] . the authors suggest that a dsr project should cover at least three cycles of investigation, a relevance cycle (targeting the practical problem, see section 2), a rigor cycle (elaborating on the existing knowledge base, see section 3), and one or multiple design cycles (building and evaluating the research artifact, see sections 4 and 5). we finish our work with a discussion on the broader impact (section 6) as well as a summarizing conclusion (section 7). [11, p. 1] . however, more evidence and more insides on the level of influence are missing. to get these insides, it is necessary to monitor the mask coverage rate (and put the results in relation with other factors). but, especially in public spaces, a monitoring of the mask coverage proves difficult by manual means. therefore, first countries experiment with automated, ai-based closed-circuit television camera (cctv) solutions for monitoring. for instance, france is reportedly testing ai-based surveillance tools to check whether people are wearing masks on public transport. to allow for this functionality, the country updated their existing surveillance setup with additional software to allow for monitoring mask-wearing, but also social distancing [12] . however, we lack information on where the analyses was performed, whether and how this complies with the regulatory requirements of the national gdpr implementation-as well as details on the utilized ai technology. while ai-based surveillance would in fact be a technically feasible solution to monitor mask recognition, any type of cctv typically raises privacy concerns [13] . the mass surveillance in the wake of china's social credit system raised extensive concerns [14] . individual examples of misuse of cctv exist as well, for instance, investigations were launched after a museum guard used cctv to spy on angela merkel's private apartment [15] . to account for privacy in surveillance we, therefore, aim to design artifacts ensuring both, privacy-preservation and a high-performing recognition of masks. to do so, we lay out different options as depicted within section 4. initially though, we are interested in existing work in the vicinity of our proposed approach. in this section, we ensure rigorous research by elaborating on related work. to that end, we specifically focus on privacy protection within the european union (eu) and algorithms to preserve privacy in video-based surveillance systems. in 2018, the eu implemented the gdpr. among its primary objectives are the control of individuals over their personal data as well as on simplifying the regulatory environment for international organizations by unifying the regulation within the eu [5] . with regard to privacy, one important requirement is that any processing of personal data must be justified. to that end, simplified speaking, any data that can be linked to an individual has to be regarded as personal data. furthermore, in order to process data, legal grounds or individual consent reflect a justification. according to a ruling of the european court of justice, a video stream containing faces corresponds to containing personal data, and, accordingly, underlies the gdpr regulation [16] . if, however, a video stream shows no personal data, the gdpr does not apply and no consent or legal basis is required in that regard. one common approach to remove personal data from any data to prevent the application of the gdpr is its anonymization, i.e., the removal of any link to an individual person. once anonymized, the data does no longer link to an individual person and does not underlie the gdpr regulation. at the same time, however, the general interest and the concerns to privacy of an individual need to be traded-off. in this case, the general interest is usually considered as high, whereas the concerns to privacy are considered low, since the processing merely serves the purpose of allowing processing of data whilst ensuring privacy on an individual level. accordingly, no consent is required. to that end, one option to approach this task is to perform anonymization on the device itself. thus, no unanonymized data is available to any party and that the unanonymized data is not stored. in this case, anonymization is be performed on edge. therefore, to conclude, if the raw data leaves the camera, it underlies the gdpr and a consent or legal basis is required for its processing. on the other hand, if data remains on the device or the transferred data is anonymized, it does not underlie the gdpr regulations. this understanding serves as a design guidance and will be picked up later again. in the following, we explore technical approaches that preserve privacy in video-based surveillance systems. most approaches to ensure privacy in video surveillance are based on anonymizing the video feed, i.e. removing any data that may reveal an identity. to that end, a two-step process is usually deployed: first, identity revealing image segments (e.g. faces) are identified and, second, modified. whilst we acknowledge that there are many identity-revealing segments within an image, we focus on faces throughout this work. thus, the above depicted two-step process corresponds to face recognition and its anonymization. the task of face recognition has been widely addressed in research. indeed, especially since the rise of deep learning, face recognition is increasingly addressed through neural networks. publications addressing face recognition through deep learning are omnipresent and indicate good results [17] . once faces are identified, commonly-used distortion approaches to ensure privacy are masking, pixelation and blurring [18, 19] . in masking, the identity-revealing segments of an image are covered with a neutral element, as, for example a black box [20, 21] . whilst those approaches most certainly address the issue of privacy, they are not applicable to the design challenge of this work, since a black box also removes any data on whether a mask is worn or not. second, pixelation refers to the substitution of squared blocks of pixels with its average [18] . given its simplicity, it is commonly used, as, for example, in television news in order to ensure privacy of individuals within the image. third, in blurring, segments of the picture are blurred, i.e. making the segments less distinct [22] . a common approach for blurring is the application of a gaussian low-pass filter. evidently, the mentioned approaches align with the general concept of privacy-enhancing technologies (pets) [23] . as such, pets are aimed at protecting an individual's privacy by the use of technical means [24] . indeed, the provision of anonymity, pseudonymity, unlinkability and unobservability of data subjects is a core component of pets [25] . as such, the above described approaches contribute to and reflect pets. aligned with the idea of pet, fitwi et al. (2019) [26] propose a lightweight solution to preserve privacy with a special focus on the internet-of-things and edge computing. as such, the authors argue that privacy measures should already be built into camera equipment, eventually making the camera a smart device only transmitting privacy-preserving video signals. in their approach, the authors rely on pre-trained machine learning models that are loaded onto the camera to compute privacy-preserving video streams on the fly. similar research is conducted by a number of researchers (e.g., [27, 28] ). to that end, those approaches comply with anonymization approaches required to bypass gdpr regulations. on that note, we could also identify research aimed at preserving privacy that are not suitable for the purpose of this work. chi and hu (2015) [29] and carillo et al. (2008) [30] , for example, propose algorithmic approaches to encrypt parts of an image that can be decrypted at a later stage in time. thus, the requirement of irreversible removal of identity-revealing data is not met. furthermore, boyer and veigl (2015) [31] purpose a system that allows for privacy-preserving video surveillance. the authors propose a system that allows access to video surveillance for police investigations. whilst this use case does underlie the gdpr, the authors introduce an authentication and data protection instance in order to prevent misuse of the video. in conclusion, this section shows the importance of privacy and how it can be enabled in video-based surveillance. the question on how privacy can be ensured in video-based monitoring systems is well addressed, however, to the best of our knowledge, the intersection of privacy-preservation and mask recognition has not yet been addressed in rigorous research. precisely, we were not able to find any peer-reviewed work covering the ai-based mask the artifact should not reveal personal data. dp1a: implement a designated privacy preserving service. df1a: implement bluring of faces. dp1b: do not forward personal data required within the analysis (e.g., raw pictures), but only the result of the analysis. df1b: perform all calculations on edge. the artifact should reach superior mask recognition performance. dp2: implement an ai-based mask recognition service. df2: implement a deep neural network for mask recognition. in accordance with the design science research paradigm, we first elaborate on our overview of design choices [32] which are depicted in table 1 . as elaborated, we are confronted with two fundamental design requirements (drs) for the artifact: privacy preservation (dr1) and recognition performance (dr2). regarding dr1, we regard two different design principles (dps) addressing the removal of personal data of raw video/image data. we can either implement a designated privacy-preserving service locally (e.g. integrated in the camera) which removes any personal data before forwarding the adjusted video data to the potential user / web service (dp1a), or run the analyses locally and only forward the result to the potential user / web service (dp1b). dp1a and dp1b are exclusive. for the precise implementations, so-called design features (dfs), we make two choices. for the privacy preserving service (dp1a), we choose to implement a blurring of faces (df1a). the utilization of pixelation would be another valid option, however lander et al. [33] show that if already familiar with a face, blurring provides better anonymization performance. blurring is state-of-the-art in literature as well as in real world applications as there are multiple privacy friendly configurations [34] . in the case of not forwarding any personal data, we choose to perform all calculation on edge, i.e., directly on the (camera) hardware-and only output the result of the analysis (df1b). no personal data is saved on the device and no personal data leaves it. thus, the gdpr requirements are satisfied. even if there are malfunctions in the mask recognition service, no violations of gdpr are possible since only a numeric feature on the share of people wearing masks is forwarded. regarding dr2, demanding a superior mask recognition performance, we choose to utilize state-of-the art ai techniques (dp2). precisely, we train a deep neural network to detect masks on images showing people (df2). deep neural networks have been proven to achieve close-to-perfect performances in image classification [35] . the resulting possible combinations of dfs leaves us with three viable combinations, which are depicted in table 2 . we have to differentiate on two dimensions: which df is utilized and where the df is deployed. in terms of deployment, it is either possible to host each of the required services (privacy preservation / ai recognition) on edge / directly on the hardware ("provider side") or to host the ai recognition service figure 1 . overview of the overall approach, illustrating the different process steps as well as the two options for deployment at each step. externally ("customer side") 2 . privacy is violated if there are options for the external / customer side to access personal data from the received information. to gain an understanding of the performances of the deep neural net, we start by calculating the baseline performance. we require this initial benchmark to later calculate the loss of performance with the raise of privacy. option centralized is a combination of df1a and df2. the privacy preservation, in our case blurring of the faces (df1a), is performed directly on edge [36] and only the edited images are put forward to an external, centralized service. in this option, the mask recognition (df2) is deployed externally. the privacy preservation is non-liftable as only the preprocessed data is available to the customer. on the downside, it might lead to worse mask recognition, which we will analyse in the upcoming evaluation. option decentralized is a combination of df1b and df2. the privacy preservation is guaranteed as the camera hardware only outputs the numerical results of the on edge mask recognition, e.g. the percentage of people wearing masks. no image data is transmitted. in this option, every aspect is embedded within one encapsulated functionality, i.e. decentralized. on the downside, the artifact does not leave any flexibility, e.g., the option to use the camera output for other analyses. the overview of the options is summarized in table 1 while the resulting overall approach is depicted in figure 1 on page 5. whilst option decentralized most certainly has the highest privacy preservation, it has one major drawback when considering a fleet of cameras: a holistic statement over all cameras is not possible. this can be illustrated using the following example: suppose there is a fleet of cameras aimed at computing the overall percentage of people wearing a face mask at a train station. using option decentralized , each camera computes the percentage of people wearing a face mask within its video stream and only forwards this percentage to a central server. this server collects the percentage of people wearing a face mask of all cameras and aggregates those to an overall percentage. a single person, however, may appear in multiple video streams. therefore, the overall percentage of people wearing a face mask may be biased. this aspect could better be accounted for using option centralized . as a next step, we implement the previously described artifact design and evaluate two aspects, the performance of each option (centralized and decentralized) as well as the influence of the blurring factor, i.e. the "degree of anonymization", on the ai's detection performance. as described in section 4, there are two possible options for designing a privacy-preserving mask recognition artifact. option centralized ensures in a first step that no personal image data (i.e., facial features which make a person identifiable) is transmitted, e.g. to external web services. faces are detected on edge (regardless of whether a person is wearing a mask or not) and blurred by applying gaussian blur. gaussian blurring is achieved by convolving each pixel of a recognized face with a gaussian kernel of variable size (factor f indicates the ratio of the kernel size to the image size) in order to create a blurred face. figure 2 on page 6 depicts an exemplary face without blurring (left) as well as the same face (second image from left to right) disguised with different blurring factors. while widely used [37] , face anonymization with gaussian blur is discussed controversially, as de-anonymization is possible under certain circumstances [38] ; e.g. dufaux and ebrahimi (2010) [18] report in the case of applying a gaussian factor of 8 and while clear (not anonymized) pictures are available to a potential attacker, recognition might be possible. to counter de-anonymization attempts, it is important to choose a low blur factor (leading to high anonymization, see figure 2 ) [39] as we do in the remainder of this work. therefore, our proposed artifact uses gaussian blurring for the moment, but alternatives should be kept in mind. in a subsequent step, the anonymized image data is processed by a separate externally deployed mask recognition service, which is capable of detecting masks even on anonymized image data. the degree of blurring, and therefore, anonymization, is dicussed in section 5.4. option decentralized performs mask recognition directly on the edge. thus, a person's privacy is preserved by not passing image data to external services at all, but only transferring aggregated indicators such as the ratio of persons wearing masks to persons without wearing masks. thus, in this case, anonymizing of image data is not necessary, since images are not transmitted to an external party anyway. from a technical point of view, option decentralized therefore is equivalent to the baseline, where raw data is directly transferred to an externally deployed service, which then takes care of mask recognition without addressing any privacy aspects. the evaluation of the artifact is based on image data of persons who either wear a mask or do not-with the aim of being able to distinguish them with the highest possible performance, measured by the metric of accuracy. the accuracy indicates the overall proportion of correctly (=true) predicted observations a classifier achieves. it reaches its best value at 1.0 (100%) and its worst at 0 (0%). while there are several publicly available data sets depicting persons' unmasked faces, data sets including persons wearing (medical) masks are rare. note, as there is no data of mass surveillance footage publicly available, we assume-as existing work shows [40, 41] -that images showing individuals can be retrieved from pictures showing multiple individuals. our evaluation is based on two different data sets showing individuals. the first originates from the machine learning platform kaggle and contains 1, 000 images, equally shared among masked and unmasked persons [42] . additionally, we utilize a data set of persons from [43] without wearing masks and automatically place an artificial mask in front of 50% of the persons' faces. an example of an artificially placed mask is displayed in figure 1 . this artificially created data set contains a total of 686 images per class. to obtain a baseline performance, we train a deep convolutional neural network based on the mobilenetv2 architecture [44] and pre-trained it on the imagenet database [45] , assigning each input image depicting a person's non-blurred face to the classes mask or no mask. we use mobilenetv2 because on the one hand it is a common architecture for this kind of application and on the other hand it is optimized for edge computing. we also fix the number of epochs at 15 to keep the training time within reasonable limits. for training-test split, we use a common 75/25 ratio. option decentralized is technically equivalent to the base case, at least in terms of modeling, and therefore its performance equals the baseline. only the kind of deployment and, thus, the aggregation of the model output ensures that privacy is maintained in comparison to the baseline. for option centralized , however, we use images with blurred faces to train a deep neural network with the same architecture as in the base case. to blur the faces we apply the state-of-the-art dlib face recognition model based on the resnet architecture [17] combined with a gaussian filter which is applied to the rectangular facial section identified by the recognition model. table 3 compares the performances. the accuracy of option centralized decreases only a few percent on both data sets when using a blur factor of 5. overall, the performance loss between baseline option decentralized and option centralized is therefore only minimal. this implies that an increase in privacy (due to the blurring factor 5) causes only a small loss in model performance. the aim of the paper is to show that mask recognition and privacy preservation do not contradict each other. for this purpose we show the overall feasibility and the difference between two different options, but do not put a strong focus on tuning the models used. in the absence of data sets with self-sewn, colored or printed everyday masks as they are worn quite often, we additionally validate a model trained on both data sets (see section 5.2) on a small number of self-recorded images. we collect 50 images of people wearing colored masks to provide a basis for demonstrating that our proposed approach is generalizable and that everyday masks can be reliably recognized. the results show that an accuracy of 90.32% is achieved with a blurring factor of 5, although we have tried to select masks that are intentionally difficult to detect (e.g., painted mouth or skin-colored). however, with a higher blurring factor, the accuracy of the model becomes progressively worse, especially due to a drastically decreasing rate of true positives. results illustrated in the previous subsection show that instant mask recognition (baseline and option decentralized ) performs slightly better than anonymizing faces in advance (option centralized ). even if these differences are still very small at a blurring factor of 5 (as depicted in table 3 ), it can be assumed that the performance of mask recognition decreases with increasing blur. therefore, we have trained the mask recognition model on faces with varying degrees of blurring (see figure 2 ). the degree of privacy preservation corresponds to the inverted blur factor. this assumption is based on the underlying mechanism of the blurring factor itself. at very large values and thus a very small kernel size, this factor causes an almost non-blurred face. in contrast, a factor of 1 corresponds to a kernel size that is equal to the image size, causing a maximum blurred face. . empirical results illustrating the trade-off between privacy-preservation and ai performance with the two implemented data sets figure 3 shows how the model performance of mask recognition actually decreases on both data sets with increasing blur. the more a face is disguised and, thus, the higher the privacy preservation, the more the model performance decreases. we call this loss of performance "price of privacy". we theorize this observation could be generalized into the tradeoff between ai performance and privacy preservation as qualitatively illustrated in figure 4 . in our case, however, despite the maximum possible blur (f = 1), it is still within an acceptable range of 6% to 11% loss of model accuracy depending on the data set. based on the promising results we include a statement of the broader impact of our work, including confounding factors, the artifact's potential ethical aspects and future societal consequences. if we imagine an option centralized -based system being in place on a large scale, possible benefits and disadvantages arise from our research. on the upside, we would be able to allow a recognition of masks coverage for research purpose, e.g. in order to monitor whether people reduce infection risks. as, for this option, we propose a removal of personal data on edge, it is not possible for consumers of the service to trace back individuals-as the raw image is not accessible. however, we need to discuss two types of errors: first, the privacy preservation service failing and, second, the mask detection service failing. although we were able to show accuracy rates are fairly high throughout our experiments, no system is perfect. the question of the data quality, in this case camera resolution, positioning angle and ability to capture a space holistically, are essential for our approach. as we only used data of high quality, results might be inferior with other data. furthermore, we did not test it within a real scenario, but on pictures only showing single persons-the segmentation of large crowds would need to be performed by a different service (on edge, as suggested by wang et al. (2020) [41] ). in any case, if the system would fail, it might be possible to trace back individuals, as there is no guarantee of correct face blurring. reasons for failure could be many, e.g., technical errors in the camera image, but also biases due to training. the latter could lead to discrimination of certain groups which were not included in the initial training. if the mask recognition service fails, different problems might be the result. on the one hand, if the service detects too many masks being worn (when in fact less are actually worn), situations might be classified as "safe" by the system, when they are, in fact, not safe. on the other hand, when the system does not detect all masks (although they are worn) it could issue wrong alarms, or, depending on the ability of the system and the severity of the alarm, lock down areas. we, therefore, encourage further research in the reliance and fairness of ai-based systems, especially in the area of surveillance. for instance, as previous work has shown, the compas system used by us courts to assess defendants' risk of recidivism, was unfair towards black people-although it was in productive use [46] . in addition to those errors, we also see a confounding factor in case one person appears in multiple video streams-as already mentioned in section 4. in detail, each video stream provides a sample of the overall population and one person within the population may appear in multiple samples (i.e. video streams). overall, this results in a prediction bias. if option decentralized is applied, no association between multiple video streams are possible and less accurate results due to the bias have to be accepted. if option centralized is applied, however, one may add an additional process step aimed at identifying the same person (yet, still anonymous) on multiple video streams, as, for example, through the clothes they are wearing. without further investigation, we believe that an additional processing may reduce, but will not completely remove the risk of less accurate results. in 2020, the covid-19 disease has evolved into a global pandemic-and governments all over the world reacted by taking different measures, so-called non-pharmaceutical interventions (npis). one of these npis, in line with current research [2] , constitutes the obligation to wear masks in public spaces like stores, restaurants, etc. [1] . one option to monitor the compliance of citizens wearing masks is to rely on video surveillance, e.g., closed circuit television (cctv). this option would have the benefit of being fully scalable and possibly automatable. however, the general data protection regulation (gdpr) has strong requirements on the handling of personal data (including clearly visible faces) [5, 16] and citizens might feel a violation of their privacy when being surveillanced [8] . to address this gap, this work proposes an ai-based surveillance artifact which ensures both (a) privacy and (b) high performance of mask recognition. we demonstrate different options of privacy-preserving methods (in-line with gdpr) and their resulting performances. depending on the chosen option, e.g., on edge or as an external service, our results show accuracies between 95% and 99%. in conclusion, we show that privacy-preserving mask recognition is well-feasible. by designing, implementing and evaluating our artifact we contribute to the body of knowledge in three meaningful ways. first, our novel artifact can be utilized to allow for a privacy-preserving monitoring of mask coverage during an epidemic like the flu or a pandemic like covid-19. second, we evaluate different design choices on how to build the artifact and elaborate on their performances and capabilities to preserve privacy. finally, we theorize on the trade-off between privacy preservation and ai performance-as ai performance decreases with increased privacy preservation and vice-versa. our findings indicate that even with the highest degree of privacy preservation we applied, the loss of ai performance does not exceed 11%. the generalizability of these results is subject to certain limitations. one shortcoming of our work is the fact that we utilize only images containing single faces. to address this issue, recent work examines the possibility to pre-process larger images to extract single images with one person per image, so-called segmentation [40, 41] . this step could be easily implemented on-edge as well. additionally, under certain circumstances recent research shows the possibility to de-anonymize blurred pictures [38] . to counter that, we use high blurring in our presented option centralized , while option decentralized does not require blurring at all. apart from these limitations, further research should be undertaken to investigate other aspects of the endeavor. engaging in a dialogue with hardware providers on the (technical) possibilities of implementing privacy-preserving measures would be worthwhile. especially in our presented option centralized , where only the blurring of faces occurs on chip the options for other applications (apart from mask recognition) are manifold. as there is no traceable personal data left as the output of the camera system, the video stream could be utilized for other cases. for instance, following the introductory example [12] , the systems could additionally be used to monitor distance rules, count the total amount of people, etc. in any of these cases, a convenient user interface would need to be designed, which we did not address in this work. depending on the use case, it would be important to build user centric interfaces for end users to ensure the technology can be put to practice. in regards to the case presented in this work, mask recognition, different applications are possible; it could be utilized to simply count how many citizens are compliant (e.g., for research purposes) or as a "red alert" warning system, i.e., within smaller and crowded places. in the latter, it would need to be discussed which actions would be undertaken as a countermeasures if people do not comply, e.g., automatic announcements over speakers or else. future work will hopefully give insights into these suggestions, as a promising field of research lies ahead. which countries have made wearing face masks compulsory face masks for the public during the covid-19 crisis face masks against covid-19: an evidence review machine learning in artificial intelligence: towards a common understanding general data protection regulation public privacy: camera surveillance of public places and the right to anonymity i spy with my little eye: the use of cctv in schools and the impact on privacy beyond 'nothing to hide': when identity is key to privacy threat under surveillance utilizing adaptive ai-based information systems to analyze the effectiveness of policy measures in the fight of covid-19 design science research in information systems face masks for the general public coronavirus france: cameras to monitor masks and social distancing situating the concern for information privacy through an empirical study of responses to video recording the road to digital unfreedom: president xi's surveillance state privacy in video surveillance reference for a preliminary ruling -directive 95/46/ec -protection of individuals -processing of personal data -concept of 'in the course of a purely personal or household activity' case c-212/13 deep residual learning for image recognition a framework for the validation of privacy protection solutions in video surveillance towards optimal distortion-based visual privacy filters preserving privacy by de-identifying face images implementation of the privacy protection in video surveillance system third ieee international conference on secure software integration and reliability improvement respectful cameras: detecting visual markers in real-time to address privacy concerns privacy-enhancing technologies for the internet a taxonomy for privacy enhancing technologies it-security and privacy: design and use of privacy-enhancing security mechanisms a lightweight blockchain-based privacy protection for smart surveillance at the edge proceedings of the second acm/ieee symposium on edge computing enabling live video analytics with a scalable and privacy-aware framework face de-identification using facial identity preserving features compression independent object encryption for ensuring privacy in video surveillance privacy preserving video surveillance infrastructure with particular regard to modular video analytics designing a requirement mining system evaluating the effectiveness of pixelation and blurring on masking the identity of familiar faces learning to anonymize faces for privacy preserving action detection imagenet large scale visual recognition challenge an extensible edge computing architecture: definition, requirements and enablers image filtering algorithms and techniques: a review defeating image obfuscation with deep learning face de-identification detecting masked faces in the wild with lle-cnns using computer vision to enhance safety of workforce in manufacturing in a post covid world mask datasets v1 covid-19: face mask detector with opencv, keras/tensorflow, and deep learning inverted residuals and linear bottlenecks mobile networks for classification, detection and segmentatio imagenet: a large-scale hierarchical image database machine bias the research reported in this paper has furthermore been supported by the german federal ministry of education and research within the framework of the project kastel ski in the competence center for applied security technology (kastel). key: cord-102315-ncjdsbn4 authors: nazeeri, a. i.; hilburn, i. a.; wu, d.-a.; mohammed, k. a.; badal, d. y.; chan, m. h. w.; kirschvink, j. l. title: an efficient ethanol-vacuum method for the decontamination and restoration of polypropylene microfiber medical masks & respirators date: 2020-04-16 journal: nan doi: 10.1101/2020.04.12.20059709 sha: doc_id: 102315 cord_uid: ncjdsbn4 a critical shortage of respirators, masks and other personal protective equipment (ppe) exists across all sectors of society afflicted by the covid-19 pandemic, placing medical staff and service workers at heightened risk and hampering efforts to reduce transmission rates. of particular need are the n95 medical face respirators that filter 95% of all airborne particles at and above 0.3 um in diameter, many of which use meltblown microfibers of charged polypropylene (e.g, the 3m 8200). an intensive search is underway to find reliable methods to lengthen the useful life of these normally disposable units. it is currently believed that these masks and respirators cannot be cleaned with 70 to 75% alcohol-water solutions, as past wet/dry experiments show that filtration efficiency can drop by ~40% after the first such treatment. this has been interpreted as the liquids disrupting the surface charge on the fibers and has led to a recent cdc/niosh advisory against using alcohol for their decontamination. we have replicated the drop in efficiency after alcohol treatment. however, we find that the efficiency can be recovered by more effective drying, which we achieve with a vacuum chamber. drying at pressures of < ~6 mbar (0.6 kpa) restores the measured filtering efficiency to within 2% or so of the pre-washing value, which we have sustained for 5 cleaning-drying cycles so far in three models of n95 masks. the mechanism seems to be the removal of water molecules adsorbed on the fiber surfaces, a hypothesis which is supported by two independent observations: (a) the filtering efficiency increases non-linearly with the weight loss during drying, and (b) filtration efficiency shows an abrupt recovery as the vacuum pressure drops from 13 to 6 mbar, the range physically attributable to the removal of adsorbed water. these results are not compatible with the electrostatic discharge hypothesis, and rather suggest that water molecules adsorbed to the fiber surface are reducing the filtration efficiency via surface tension interactions (e.g., wicking between the fibers and coating their surfaces with a film). such a degradation mechanism has two implications: (a) respirators decontaminated by a soak in 70% v/v ethanol regain their filtration efficiency once they are fully dry. we employ vacuum chambers in this study, which are inexpensive and commonly available. (b) this mechanism presents the possibility that mask filtration performance may be subject to degradation by other sources of moisture, and that the mask would continue to be compromised even if it appears dry. the mask would need to be vacuum-dried to restore its performance. this study introduces a number of methods which could be developed and validated for use in resource-limited settings. as the pandemic spreads to rural areas and developing nations, these would allow for local efforts to decontaminate, restore, monitor, and test medical masks. the covid-19 pandemic has created a shortage of masks in hospitals and communities. inexpensive ways of locally disinfecting and testing masks are of great importance, especially as the pandemic spreads to rural areas and developing nations. we have discovered a method to clean hospital-grade face masks by first soaking masks in an ethanol solution, air-drying them, then vacuum-drying them. our study has found that this cleaning process can be used on a mask at least five times without altering the filter rate of the mask by more than one per cent. vacuum-drying the masks removes a thin layer of water that still sticks to the fibers in the mask after air-drying. this layer of water is probably what causes the mask efficiency to drop (that is, how well it filters particles from the air). there is a danger that if the mask gets wet in other ways that it will not filter the air as well. this could also be fixed with the vacuum-drying procedure. our study may lead to inexpensive designs that would allow hospitals to build their own face-mask testing rigs to measure the filtration efficiency of equipment that they have purchased online from unverified sources as well as those being reused. we built a simple mask testing rig from items that are cheap and easy to obtain, though the current design relies on a calibrated $2,500 laser particle meter. we are working to adapt cheaper laser particle meters into the design. medical respirators and masks are in critically short supply across the globe, in particular the n95 variety that removes 95% of particles at and greater than 0.3 μm in diameter. most of these masks produced in the us today consist of meltblown microfibers of polypropylene, which are designed to be disposable 1 . during use in clinical settings, the filters may become contaminated with active viral or bacterial particles, necessitating that any efforts to refurbish them should employ decontamination techniques in addition to cleaning. such techniques could ease the supply demand and immediately aid medical personnel treating covid-19 patients, many of whom currently have no choice but to reuse dirty devices that have unknown filtering efficiency. there is a need for simple methods for using equipment commonly available in most hospital and clinical environments to enable safe reuse of masks. if found, such methods would rapidly ease this critical shortage even in resource-constrained settings. one of the simplest methods for decontamination is to rinse or soak materials in 60-80% ethanol, which is a potent virucidal agent inactivating all of the lipophilic viruses 2 . unfortunately, previous results 3, 4 found that the performance of n95 respirators degrades by ~28% to 40% after a single immersion in a solution of 70-75% alcohol when followed by drying in air. tsai 4 postulated that the mechanism for this deactivation might be the penetration of the alcohol into the polypropylene microfibers, permanently disrupting the electrical charges on the surfaces which trap aerosols. these studies have prompted a warning from the cdc/niosh to avoid using alcohol for their decontamination 5, 6 . we report here the discovery that decontaminating polypropylene microfiber filters in a 70% v/v solution of ethanol and deionized (di) water, using standard medical procedures including air drying, does not permanently damage the microfibers as has been suggested 3, 4, 7 . instead, this washing procedure appears to leave a film of water molecules adsorbed hygroscopically on the surface that reduces the particulate absorption efficiency; approximately 2-4 g of water remains firmly on a typical respirator even after extensive air drying due to the large surface area of the fibers. we found that this layer of adsorbed water can be removed by further drying in a partial vacuum to below 6 mbar (0.6 kpa), after which we observe the filtration efficiency returning to within 2% of the original values. as shown in table 2 , we have repeated this on three different types of n95 respirators for five cycles and see no long-term degradation at this time. we describe the easily constructed experimental setup that we use for measuring filtration efficiency, present results with 70% v/v ethanol treatment and the effectiveness of vacuum drying on . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 16, 2020. . https://doi.org/10.1101/2020.04.12.20059709 doi: medrxiv preprint mask efficiency, and discuss our proposed adsorption mechanism of action and two experimental tests of it. in order to measure the efficiency of various medical masks and respirators, it is necessary to monitor the drop in particulate concentration for air that is passing through the filters under conditions that mimic those under natural use. commercial units for doing this that follow formal ashrae (american society of heating, refrigerating and air-conditioning engineers) aerosol standards cost upwards of $65k, with delivery lead times longer than that expected for the covid-19 pandemic. however, our present analytical needs are more limited as we simply need to measure the filtration efficiency, not achieve formal certification. prior to the pandemic we routinely monitored air quality in a magnetically-shielded, biomagnetic clean lab 8 in the 0.3, 0.5, 1 and 10 μm size bins using a metone tm aerocet 531s laser particle counter, which is nist-referenced and meets or exceeds ce and iso 21501 certifications. these units sample air at ambient pressure with a small pump, running it through the laser detectors and counting particles in the four size bins. in order to use this to sample the air passing through a filter, we constructed a testing facility as shown in fig. 1 . we wrapped a styrofoam bust of a human head (previously used as an eeg blank) in three layers of ordinary kitchen plastic wrap to give surface friction and pliancy, drilled a vent hole "mouth", and placed the n95 respirators over the opening. this setup was housed inside a plexiglass box, which was then pressurized with 'dirty' pasadena air (the pressurized box reached ~2,000,000 particles > 0.3 μm/cf) using an industrial heat gun dryer (a gilson tm ma-290f) in non-heat mode, mounted to the side. air passed through the filters and then exited through a pvc pipe, which was sampled by the particle counter at ambient pressure. the air then flowed through a 2 m length of plastic hose to minimize backflow of outside air into the counter from turbulence. the flow rate through the mask was adjusted using the intake manifold on the heat gun to ~23 l/min. we found that minor deviations in flow rate had no noticeable effect on the efficiency measure. every two minutes the particle counter inlet was switched between the mask port (post-filtration) and a box port (unfiltered background air in the box), and the ratios of the total particle counts were used to calculate the filtration efficiency. the data were transmitted via usb serial link and stored to file on a local computer. this computer system both collected data from the particle counter and controlled the device via custom-built software in c#, adapted from software developed for monitoring air quality in the aforementioned clean lab 8 . the 70% v/v ethanol solution was prepared with 200 proof laboratory grade ethanol and deionized (di) water, which is within the cdc guidelines for disinfection 2 . approximately 50 ml of ethanol solution was poured over each mask, such that every part of the mask was saturated. excess liquid was blotted off with a paper towel, and the masks were allowed to air dry for 2-3 hours before the vacuum experiments were conducted. the error in the filtration efficiency was split into two different types: error introduced by variations in the fit of the mask and error introduced by the particle counter set up. error from the fit was addressed by refitting the mask 3-4 times and calculating the standard deviation from the mean of the measurements. error from the particle counter setup was found by taking 2-3 measurements in steady state per mask fitting and calculating the standard deviation from the mean of the measurements. the total error in the filtration efficiency was found through quadrature. the error in the masks' masses in fig. 2 was found through the difference in mask mass before and after the efficiency measurement (this difference is due to some of the adsorbed water being removed by airflow during testing). . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 16, 2020. . https://doi.org/10.1101/2020.04.12.20059709 doi: medrxiv preprint results: table 1 lists the medical masks and respirators that we have examined so far. new n95 respirators from 3m tm typically gave filtration readings above 95% (consistent with their n95 rating from niosh), and other mask types with lower ratings gave similarly consistent results. although we did not use standard ashrae aerosol procedures, data from the experimental setup, shown in fig. 1 , are in agreement with those procedures and verify the utility of our experimental setup. similarly, the n95 respirators dropped in efficiency by 20-30% following alcohol cleaning; this is consistent with previously reported results 3, 4 . table 2 shows the results from five cycles of alcohol decontamination / drying that were conducted on three varieties of 3m tm n95 respirators (3m tm 8200, 8210 and 8511 masks). after these cycles, all masks remained at or above 95% filtration efficiency. as of this writing have conducted 18 wet/dry/vacuum cycles on 6 different masks, all of which drop in performance after wetting, but return to within 99% of their initial filtration efficiency after vacuum treatment to < 6 mbar. data for the effect of mass loss on filtration efficiency for two of the 3m tm n95 respirators are shown on fig. 2 . the large error in the mass measurements during the main drying interval was due to continued evaporation during the time the masks were on the testing rig with air being forced through them, as shown in fig. 1 . in both cases, the filtration efficiency approached its initial value as the mask weight approached its initial values, indicating that liquid adsorbed in the washing process reduced filtration efficiency. direct measurements of filtration efficiency, as a function of vapor pressure, for these same masks are shown in fig. 3 . in both cases, the major change in filtration efficiency occurred as the pressure dropped between 13 and 6 mbar with the efficiency of both masks returning to close to the initial measurements. this range is compatible with the removal of bound water molecules as considered in the discussion section below. an additional experiment on one 3m tm 8200 respirator soaked in pure di water showed a similar drop in efficiency followed by full recovery to 96.5 ± 0.2% after vacuum drying, supporting the bound water hypothesis. two generic masks of unknown composition and filter efficiency, one of which was labelled as "n95 style" on amazon, were not measured as having filter efficiency comparable to niosh rated n95 masks. this underscores the need for more distributed mask testing capacity as an increasing number of respirators and masks with untested characteristics are brought into medical and professional use. proposed mechanism of action: previous studies have assumed that the observed loss of filtering efficiency is due to the neutralization of surface charges on the polypropylene microfibers 3,4,7 . our data point to a mechanism based on surface wetting, which is reversible by drying. it is well known that in order to remove water molecules that are trapped or adsorbed on solid surfaces the pressure of the vacuum chamber must be reduced to a value that is below the saturation vapor pressure of water; lower pressures will thin the adsorbed water layer. we note that the saturated vapor pressure of ethanol and water at 20˚c are 58 and 23 mbar respectively. when water molecules are adsorbed to surfaces in vacuum chambers, pressures as low as 1-20 mbar are needed to remove them 9 . hence, our data suggest that water bound to the surface of the fibers is responsible for the loss in filtering efficiency, as evidenced by our observation of the same effect in a respirator soaked in di water. this surface wetting mechanism for performance degradation is consistent with the nature of the mask materials. the active material of the 3m tm n95 masks is melt-blown, fibrous polypropylene modified by corona discharge to contain embedded charges 4, 10 . sem indicates that the diameters of the fibrous strands are on the order of ~1 μm 11 , giving the filter a huge specific surface area. when the fibers are cleaned and rinsed with the ethanol solution, thin liquid films are introduced onto the material. the surface tension of the liquid film causes the fibers to wick together and form bundles, thereby opening gaps. in addition, the clumping of individual fibers significantly reduces the surface area available for . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 16, 2020. . https://doi.org/10.1101/2020.04.12.20059709 doi: medrxiv preprint capturing the particles. assuming the diameter of the polypropylene fibers are ~1 μm, a monolayer of water (~0.1 nm thick) would increase the mass of a mask by around 25% 12 . we have observed this experimentally: when a mask is treated and left to air dry overnight, a residual of several grams is left. hence, it is not surprising that the n95 face masks become ineffective after even one rinsing process. furthermore, as the 70% ethanol adsorbs onto the surface of polypropylene fibers and its surface tension should cause fibers to wick together, similar to how the hairs on a fine paint brush stick together when wet. this wicking should decrease the surface area available for particle adsorption and allow pores to form in the filter material: this would then cause the filtration efficiency to drop drastically. when allowed to dry, the mixture evaporates with ethanol preferentially being in the vapor. the result of several hours of air drying is a thin film of primarily water deposited evenly over the surface of the fibers. for fibers that are wicked together, a thin layer of water keeps the fibers bonded. this final layer of water, while not contributing a large amount of mass, decreases the mask efficiency considerably. furthermore, due to the low surface area available for evaporation for water stuck between two fibers, it takes stronger conditions (drying the mask under vacuum) to decrease the partial pressure of water and increase the mean free path of water molecules needed for their removal. our results indicate that mask performance scales with how well the masks are dried, as measured both by the mass of the masks and the vacuum level used to dry them. a mask soaked in 70% v/v ethanol and dried in air overnight weighs 2-4 g more than it did originally and has substantially reduced filtration efficiency (fig. 2) . furthermore, our data show that the filtration efficiency scales inversely with the amount of water adsorbed. vacuum treatment of masks at pressures between 15 and 6 mbar restored the filtering efficiency (fig. 3) . the mechanism for this would simply be the reverse of the previously stated clumping effects, and the subsequent increase in effective surface area for the capture of particles. we note that a mechanism based on surface wetting raises the possibility that losses in filter efficiency might also be caused by other sources of moisture. spills, accidents, sweat, or moisture from the wearer's breath can become absorbed by the mask. however, due to surface tension, some of the water content might remain as microdroplets harmlessly trapped between the fibers. if some of the water is actually adsorbed onto the fibers, though, then this would cause the wicking and other effects. while absorbed microdroplets may evaporate easily due to their large surface area, the adsorbed water will not dry so easily. thus a mask that seems to have dried may actually be compromised by adsorbed water and require vacuum treatment. it remains to be seen what conditions lend to absorption vs. adsorption. adsorption may also be a propagating effect, such that a single adsorption event may draw neighboring microdroplets onto the surface. liao et al. 3 observed a peculiar feature in that steam cleaning cycles only reduced the efficiency of n95 masks slightly over the first 4 cycles, but the 5th cycle abruptly degraded their efficiency by 13%. our adsorbed water mechanism would explain this result. in the first cycles, moisture would have accumulated harmlessly at lower levels, with the water retained as microdroplets between the fibers. by the fifth cycle, a critical point may have been reached, with droplets merging and adsorbing onto the fibers, causing them to 'wick' together. based on this mechanism, it is likely that the loss of filtration performance stemming from steam cleaning would also be reversed with vacuum-drying. other methods of decontamination that are being suggested include heating in a dry oven at 70˚ c for 30 minutes 3 , and hydrogen peroxide vapor treatment 13 . the thermal treatment is well below the 160˚c for 2 hours recommended for medical sterilization by dry heat 14 . low heat methods have not been tested on coronavirus outside of solution, nor for effectiveness against covid-19 specifically 3 . the cdc warns of the uncertainty of the disinfection efficacy of moist heat methods for various pathogens 5 . the effect of such heat levels on the thermoplastic mask seals and other fixtures is unknown. the material data sheet from 3m tm for their n95 8200, 8210 and 8511 particulate respirator masks cautions against temperatures over 30˚c 1 . the hydrogen peroxide vapor treatment requires bulk specialized equipment unlikely to be available at the scale of a local hospital or medical clinic, though it might be practical on a large scale 15, 16 ; additionally, repeated treatments degrade the elastic bands and plastics commonly used in . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 16, 2020. . https://doi.org/10.1101/2020.04.12.20059709 doi: medrxiv preprint face masks, impeding their ability to form an adequate face seal [15] [16] [17] . in contrast, the materials used to make the masks and respirators that we tested are inert to 70% ethanol, water exposure, and vacuum. while several studies have demonstrated how certain methods may minimally damage filter material, we are unaware of any other study that documents the restoration of a mask from a compromised state. the vacuum drying process removes moisture in general, which would be effective not only for the water left from ethanol-based decontamination, but also for moisture that masks might accumulate during extended use. a moisture-based mechanism for efficiency loss and recovery would suggest that performance degradation might accompany normal use, due to water vapor from the users' breathing. if that is the case, then any procedure for processing masks for reuse should include a vacuumbased or other deep drying stage. otherwise, water vapor would continue to accumulate with each reuse. vacuum pumps of sufficient strength to reach the pressure levels needed are common industrial products available from a few hundred dollars, are often used in high-school science demonstrations, and are present in many research labs around the globe. these could be used easily during this pandemic in virtually any clinical environment. such vacuums are also used on industrial scales for a variety of processes, and could be added easily to other major decontamination procedures like the hydrogen peroxide treatment 15, 16 . our mask testing setup costs around $3k, much lower than the $65k for an industry-standard testing rig with similar functionality but using ashrae aerosol standards. we discuss these limitations in the next section. even our current figure could be pushed down to less than $500 if cheaper particle counters can be validated, as our setup uses an expensive particle counter that we happened to have on hand. although our design is less expensive, it is quite accurate within its domain, and has several advantages over established testing methods. in particular, conventional testing rigs do not test the impact of mask fit on performance. the standard procedure is to seal the mask onto the flat surface of the device with beeswax or other adhesive, even deforming the mask if necessary. this is unfortunate because studies have shown that the leakage around the mask, not through the medium, is the main determinant of total mask efficiency 18 . poor fit can reduce an n95 mask from 95% to below 60% efficiency, which is below that of some masks made from commercial fabric 19, 20 . in contrast, our testing setup uses a head model, upon which the mask is "worn", and is remarkably quick and easy to seal completely against the plastic film wrapped around the head model. we are seeking to improve upon this with 3d-printed head models and synthetic skin coverings (e.g. 21 ). such an improved version could then be used to validate inexpensive head forms for testing rigs. the issue of fit is of particular concern in the current situation. hospitals are now on their own, searching for masks on the global market. it is difficult to evaluate how a given mask intended for use in one country will fit the range of face shapes present in another. it is also unknown how various disinfection techniques will impact fit. application of heat as suggested by liao et al. 3 , for example, may impact the thermoplastics that line the edges of many masks. use of uv, bleach, or other chemicals may degrade the lining in other ways. all of these fit factors need to be taken into account in determining the best masks to use and the best ways to disinfect them. we avoided the use of tap water in our alcohol mixture because of the previous suggestions of interactions with surface charges on the microfibers. although our findings support surface tension mechanisms instead, we do not know if ions in tap water have an effect. this remains to be tested. it is not known how generalizable these results are across other types of masks or similar decontamination procedures. for example, both ethanol and isopropanol are known to be effective decontaminants, but whether our method extends to isopropanol is unknown. unlike ethanol, isopropyl alcohol damages polyester 17 and may degrade other components of the masks and respirators. the effect of vacuum desiccation on cotton fiber-based masks is also unknown. the procedure outlined here for regenerating mask filtering efficiency has not yet been approved by the fda, niosh, or any other relevant regulatory agencies, although the use of the alcohol solution is . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 16, 2020. . https://doi.org/10.1101/2020.04.12.20059709 doi: medrxiv preprint a well-vetted technique for disinfection 2 . we believe the methods and techniques used here are simple enough to implement and verify by other research groups. our testing station tests filtering performance on particles in ambient air, rather than ashrae aerosol standards. however, our particle counter directly measures particle sizes, based on calibrations that are nist-referenced and meet or exceed ce and iso 21501 certification. the distribution of particle sizes was appropriate, with 90% of particles falling in the 0.3 µm bin, and our analyses were based on data from that bin. further, our tests produced the expected results on certified masks, and replicated the results from other experiments using standard methods. ultimately, we would like to determine the extent to which measurements from inexpensive, accessible designs can be validated as equivalent or correctable to standard. performance degradation in n95 face respirators is likely caused partially by moisture on the polypropylene fibers. we identify an effective disinfection and restoration method: rinsing the face masks in a 70% v/v ethanol solution, then air drying, followed by pumping on them in a vacuum chamber to a pressure below 6 mbar. we replicated previous reports that alcohol-based decontamination could result in a decrease in efficiency of ~40% after air-drying. as of this writing, we have conducted 18 wet/dry/vacuum cycles on 6 different masks, all of which drop in performance after wetting, but return to within 98% of their initial filtration efficiency after vacuum treatment to < 6 mbar. in addition, this restoration has been verified for up to 5 cleaning cycles on the n95 rated 3m tm 8200, 8210 and 8511 masks. we attribute the degradation of mask performance to the presence of adsorbed moisture that causes the micron scale electrostatic polypropylene fibers to clump together, significantly reducing the effective surface area of the filtering material. in addition, water adsorbed on the surface of the microfibers might interfere with their electrostatic interactions. the vacuum treatment fully dries the mask, allowing the fibers to spring back to their original arrangement, and restores the available surface area so that the electrostatic fibers are effective in capturing the micron and submicron size particles. because moisture can accumulate in masks as they are used, mask performance might degrade even absent a decontamination treatment. if so, conditioning processes for extending the usable life of masks, even ones that do not involve water, should completely dry the masks in order to counteract any adsorbed water that may have accumulated during extended use. in addition to the decontamination and restoration treatment, this study suggests that it would be worth exploring a number of simple and accessible procedures that could potentially be employed by institutions of limited means. the filtration testing setup we used can be assembled at low cost, and the decontamination and drying protocols also use low-cost methods. further development may lead to methods for small and resource-limited medical facilities to test, decontaminate, and recondition masks in order to extend the lifespan of existing ppe. further testing is currently underway to reduce costs, optimize accuracy, and validate potential designs which could be implemented quickly and cheaply. tables: figure 1 : left, schematic diagram of the experimental medical filter testing chamber. right: image of the current system with the top removed. the hand-held air blower forces ambient dirty air (~2 million particles at and above 0.3 μm/cuf) into the chamber, which exits either through the mask/head plumbing system or through the background port. the ratio of the particle counts at and above 0.3 μm between the two ports gives a direct measure of the mask efficiency. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 16, 2020. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the copyright holder for this preprint this version posted april 16, 2020. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 16, 2020. . https://doi.org/10.1101/2020.04.12.20059709 doi: medrxiv preprint v/v ethanol solution, then allowed to air dry for 2.5 hours until the weight had stabilized. the original dry weight of the masks were 9.88g (a) and 15.46g (b). soaking and then air drying increased that weight of the masks to ~20.6g (a) and ~22.8g (b). the masks were then pumped on and removed at intervals to record the masks' mass and efficiency. as the mass of water in the mask decreased, the mask's efficiency increased. post-rinsing efficiency prior to vacuum treatment for the respirator in (a) was not measured and for (b) was 75.2% at 1000 mbar. this confirms the hypothesis that the mass of adsorbed liquid is adversely influencing filtration efficiency. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 16, 2020. . https://doi.org/10.1101/2020.04.12.20059709 doi: medrxiv preprint masks were soaked with 70% v/v ethanol solution and progressively dried with a vacuum. the rapid increase in filtering efficiency as pressure drops below ~13 mbar is evidence for the removal of water molecules adsorbed to the surface of the microfibers; many studies of moisture removal from vacuum systems have shown that pressures in this range are necessary for this 9 . error bars for pressures below 10 mbar are smaller than the symbol size. these data are consistent with the hypothesis that adsorbed water molecules on the surface of the microfibers are responsible for the loss in filtering efficiency. . cc-by-nc-nd 4.0 international license it is made available under a is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. (which was not certified by peer review) the copyright holder for this preprint this version posted april 16, 2020. . https://doi.org/10.1101/2020.04.12.20059709 doi: medrxiv preprint technical specifications sheet 3m partriclate respirator 8200/07023(aad), n95. 3m corporation us government can n95 facial masks be used after disinfection? and for how many times information and faqs on the performance, protection, and sterilization of face mask materials decontamination and reuse of filtering facepiece respirators recommended guidance for extended use and limited reuse of n95 filtering facepiece respirators in healthcare settings loading and filtration characteristics of filtering facepieces sensory perception of the geomagnetic field in animals & humans. in: blank m, ed. electromagnetic fields: biological interactions and mechanisms removal of water from unbaked vacuum system direct probing of solvent-induced charge degradation in polypropylene electret fibres via electrostatic force microscopy preparation of polypropylene micro and nanofibers by electrostatic-assisted melt blown and their application measuring sub-nm adsorbed water layer thickness and desorption rate using a fused-silica whispering-gallery microresonator cleaning and decontamination of reusable medical equipments, including the use of hydrogen peroxide gas decontamination sterilization by dry heat hydrogen peroxide vapor sterilization of n95 respirators for reuse. medrxiv preprint doiorg/101101/20200324200410872020. 16. final report for bioquell hpv decontamination for reuse of n95 respirators fit factors for quarter masks and facial size categories fitting characteristics of n95 filtering-facepiece respirators used widely in china testing the efficacy of homemade masks: would they protect in an influenza pandemic development of an advanced respirator fit-test headform we thank mr. masamoto horikawa, mr. hironori hidaka and dr. atsuko kobayashi of the tokyo institute of technology for the early version of the control software for the laser particle counter. key: cord-225145-m5udub60 authors: kai, de; goldstein, guy-philippe; morgunov, alexey; nangalia, vishal; rotkirch, anna title: universal masking is urgent in the covid-19 pandemic: seir and agent based models, empirical validation, policy recommendations date: 2020-04-22 journal: nan doi: nan sha: doc_id: 225145 cord_uid: m5udub60 we present two models for the covid-19 pandemic predicting the impact of universal face mask wearing upon the spread of the sars-cov-2 virus--one employing a stochastic dynamic network based compartmental seir (susceptible-exposed-infectious-recovered) approach, and the other employing individual abm (agent-based modelling) monte carlo simulation--indicating (1) significant impact under (near) universal masking when at least 80% of a population is wearing masks, versus minimal impact when only 50% or less of the population is wearing masks, and (2) significant impact when universal masking is adopted early, by day 50 of a regional outbreak, versus minimal impact when universal masking is adopted late. these effects hold even at the lower filtering rates of homemade masks. to validate these theoretical models, we compare their predictions against a new empirical data set we have collected that includes whether regions have universal masking cultures or policies, their daily case growth rates, and their percentage reduction from peak daily case growth rates. results show a near perfect correlation between early universal masking and successful suppression of daily case growth rates and/or reduction from peak daily case growth rates, as predicted by our theoretical simulations. our theoretical and empirical results argue for urgent implementation of universal masking. as governments plan how to exit societal lockdowns, it is emerging as a key npi; a"mouth-and-nose lockdown"is far more sustainable than a"full body lockdown", on economic, social, and mental health axes. an interactive visualization of the abm simulation is at http://dek.ai/masks4all. we recommend immediate mask wearing recommendations, official guidelines for correct use, and awareness campaigns to shift masking mindsets away from pure self-protection, towards aspirational goals of responsibly protecting one's community. pirical data set we have collected that includes whether regions have universal masking cultures or policies, their daily case growth rates, and their percentage reduction from peak daily case growth rates. results show a near perfect correlation between early universal masking and successful suppression of daily case growth rates and/or reduction from peak daily case growth rates, as predicted by our theoretical simulations. taken in tandem, our theoretical models and empirical results argue for urgent implementation of universal masking in regions that have not yet adopted it as policy or *this collective work grew out of a kinnernet discussion group about covid-19 initiated by guy-philippe goldstein. all authors contributed to the overall design and writing. additionally, goldstein formulated overall study goals and analysed policy data, morgunov ran the seir simulation and collected policy data, de kai created the online interactive abm simulation, nangalia contributed with medical expertise and to the model design, and rotkirch and de kai first drafted the report. as a broad cultural norm. as governments plan how to exit societal lockdowns, universal masking is emerging as one of the key npis (non-pharmaceutical interventions) for containing or slowing the spread of the pandemic. combined with other npis including social distancing and mass contact tracing, a "mouth-and-nose lockdown" is far more sustainable than a "full body lockdown", from economic, social, and mental health standpoints. to provide both policy makers and the public with a more concrete feel for how masks impact the dynamics of virus spread, we are making an interactive visualization of the abm simulation available online at http://dek.ai/masks4all. we recommend immediate mask wearing recommendations, official guidelines for correct use, and awareness campaigns to shift masking mindsets away from pure selfprotection, towards aspirational goals of responsibly protecting one's community. with almost all of the world's countries having imposed measures of social distancing and restrictions on movement in march 2020 to combat the covid-19 pandemic, governments now seek a sustainable pathway back towards eased social restrictions and a functioning economy. mass testing for infection and serological tests for immunity, combined with mass contact tracing, quarantine of infected individuals, and social distancing, are recommended by the who and have become widely acknowledged means of controlling spread of the sars-cov-2 virus until a vaccine is available. against this backdrop, a growing number of voices suggest that universal face mask wearing, as practiced effectively in most east asian regions, is an additional, essential component in the mitigation toolkit for a sustainable exit from harsh lockdowns. the masks-for-all argument claims that "test, trace, isolate" should be expanded to "test, trace, isolate, mask". this paper presents crossdisciplinary, multi-perspective arguments for the urgency of universal masking, via both new theoretical models and new empirical data analyses. specifically, we aim to illustrate how different degrees of mass face wearing affects infection rates, and why the timing of introduction of universal masking is crucial. in the first of two new theoretical models, we introduce an seir (susceptible-exposed-infectiousrecovered) model of the effects of mass face mask wearing over time compared to effects of social distancing and lockdown. in the second of two new theoretical models, we introduce a new interactive individual abm (agentbased modelling) monte carlo simulation showing how masking significantly lowers rates of transmission. both models predict significant reduction in the daily growth of infections on average under universal masking (80-90% of the population) if instituted by day 50 of an outbreak, but not if only 50% of the population wear masks or if institution of universal masking is delayed. we then compare the two new simulations presented here against a new empirical data set we have collected that includes whether regions have universal masking cultures or policies, their daily case growth rates, and their percentage reduction from peak daily case growth rates. since little precise quantitative data is available on cultures where masking is prevalent, we explain in some depth the historical and sociological factors that support our classification of masking cultures. results show a near perfect correlation between early universal masking and successful suppression of daily case growth rates and/or reduction from peak daily case growth rates, as predicted by our theoretical simulations. to preview the key policy recommendations that our two new seir and abm predictive models and empirical validation all lead to: 1. masking should be mandatory or strongly recommended for the general public when in public transport and public spaces, for the duration of the pandemic. 2. masking should be mandatory for individuals in essential functions (health care workers, social and family workers, the police and the military, the service sector, construction workers, etc.) and medical masks and gloves or equally safe protection should be provided to them by employers. cloth masks should be used if medical masks are unavailable. 3. countries should aim to eventually secure mass production and availability of appropriate medical masks (without exploratory valves) for the entire population during the pandemic. 4. until supplies are sufficient, members of the general public should wear nonmedical fabric face masks when going out in public and medical masks should be reserved for essential functions. 5. the authorities should issue masking guidelines to residents and companies regarding the correct and optimal ways to make, wear and disinfect masks. 6. the introduction of mandatory masking will benefit from being rolled out together with campaigns, citizen initiatives, the media, ngos, and influencers in order to avoid a public backlash in societies not culturally accustomed to masking. public awareness is needed that "masking protects your communitynot just you". masks indisputably protect individuals against airborne transmission of respiratory diseases. a recent cochrane meta-analysis found that masking, handwashing, and using gowns and/or gloves can reduce the spread of respiratory viruses, although evidence for any individual one of these measures is still of low certainty (burch and bunt, 2020) . currently, the lowest recorded daily growth rates in covid-19 infections appear to be found in countries with a culture of mass face mask wearing, most of whom have also made mask wearing in public mandatory during the epidemic, and most of whom are not currently locked downan observation that we study systematically in section 5. outside of east asia, support for universal masking is emerging elsewhere across the globe. the czech republic was the first non-asian country to embrace and impose mandatory universal masking on march 11, 2020. the czech policy swiftly inspired various initiatives from citizens, journalists and scientistse.g., de kai (2020), howard and fast.ai team (2020) , manjoo (2020) , abaluck et al. (2020 ), feng et al. (2020 , fineberg (2020), tufekci (2020)and created global movements such as #masks4all and #wearafuckingmask. their arguments build on the ability of the covid-19 virus to spread from pre-and asymptomatic individuals who may not know that they are infected, and to linger in airborne droplets. leading political and medical experts who early were advocated masking included chinese cdc directorgeneral prof. george fu gao (servick, 2020) , former fda commissioner scott gottlieb and prof. caitlin rivers of johns hopkins , and the american enterprise institute's roadmap . in early april 2020 a rapidly increasing number of governments from countries without a previous culture of mask wearing require or recommend universal masking including the czech republic, austria and slovakia. additionally, public health bodies in the usa, germany, france (acadmie nationale de mdecine, 2020) and new zealand have moved toward universal masking recommendations (morgunov et al., 2020) , as shown below in figure 6 . the world health organization (2019) previously issued guidelines discouraging the use of masks in the public. however in early april 2020 the world health organization (2020) modified the guidelines, allowing selfmade masks but rightly stressing the need to reserve medical masks for healthcare workers (nebehay and shalal, 2020) , and to combine masking with the other main npi needed to combat the pandemic. the policy shifts of the who and other cdcs reflect advances in our scientific understanding of this pandemic, and help legitimise the altruistic "mask resistance" of civil society in this global effort against covid-19. in the first of our two new theoretical models, we employed stochastic dynamic network based compartmental seir modeling to forecast the relative impact of masking compared to the two main other societal nonpharmaceutical interventions, lockdown, and social distancing. the seir simulations were fit to the current timeline in many western countries, with a lockdown imposed march the 24th (day 1) and planned to be lifted on may 31st. universal masking is introduced in april. the simulation continues for 500 days from day 0, or around 17 months. the experimental results strongly support the need for universal masking as an alternative to continued lockdown scenarios. for this strategy to be most effective, the vast majority of the population must adopt mask wearing immediately, as most regions outside east asia are rapidly approaching day 50. in a seir model, the population is divided into compartments which represent different states with respect to disease progression of an individual: susceptible (s), exposed (e), infectious (i) and recovered (r). a susceptible individual may become exposed if they interact with an infectious individual at rate β (rate of transmission per s-i contact per time). from e , the individual progresses to being infectious (i) and eventually recovered (r) with rates σ (rate of progression) and γ (rate of recovery), respectively. additionally, individuals in i are removed from the population (i.e., die of the disease) at rate µ i (rate of mortality). we used a seir model implemented 1 on a stochastic dynamical network that more closely mimics interactions between individuals in society, instead of assuming uniform mixing as is the case with deterministic seir models. furthermore, such approach allows setting different model parameters for each individual, which we use to model masking. in a network model, a graph of society is built with nodes representing individuals and edgestheir interactions. each node has a state s, e, i, r, or f (the latter added to represent dead individuals). adjacent nodes form close contact networks of an individual, while contacts made with an individual from anywhere in the network represent global contacts in the population. varying the parameters affecting the two levels of interaction, as well as setting network properties such as the mean number of adjacent nodes ("close contacts") allows us to model the degree of social distancing and lockdown measures. formally, each node i is associated with a state x i which is updated based on the following probability transition rates: where δ xi=a = 1 if the state of x i is a , or 0 if not, and where c g (i) denotes the set of close contacts of node i . we implemented seir dynamics on a stochastic dynamic network with a heterogeneous population. we assumed an initial infected population of 1% and modelled the assumed effects of social distancing, lockdown, and universal masking over time on the rates of infection in the population. all seir models were built using the seirs+ modelling tool 2 , version 0.0.14. the baseline model parameters are fit to the empirical characteristics of covid-19 spread, as documented in the seirs+ distributed covid-19 notebooks. specifically, we set β = 0.155, σ = 1/5.2 and γ = 1/12.39. this parameterisation describes a seir model with best estimates for covid-19 dynamics. the initial infected population (init i ) was set to 1%, and all others to 0%. the size of the total population was set to 67,000 (a representative typical case, that is a factor of 1,000 from the population of the uk). social distancing. in the model, social distancing was defined as the degree distribution of the contact network of an individual. default interaction networks were used, constructed as barabasi-albert graphs with m = 9 and processes using the package function custom exponential graph with different scale parameters. normal graph (scale=100) with mean degree 13.2, distancing graph (scale=10) with mean degree 4.1 and lockdown graph (scale=5) with mean degree 2.2. lockdown stringency. lockdown stringency was modelled considering no stringent lockdown (i.e. only figure 1 : simulation results for a representative scenario: universal masking at 80% adoption (red) flattens the curve significantly more than maintaining a strict lockdown (blue). masking at only 50% adoption (orange) is not sufficient to prevent continued spread. replacing the strict lockdown with social distancing on may 31 without masking results in unchecked spread. social distancing) or stringent lockdown using the locality parameter p, which was set to 0.02 during lockdown and 0.2 during social distancing phases. this dictates the probability of individuals coming into contact with those outside of their immediate network. assuming that individuals have around 13 contacts in normal everyday life, social distancing will reduce this to 4 and lockdown to only 2. mask wearing. a gradual increase in mask wearing was modelled using a linear increase in the proportion of individuals randomly allocated with a reduced rate of transmission. the factor by which β was reduced was conservatively set to 2. the period of time over which the mask wearing went from 0 to maximum % was set to 10 days. 50% and 80% maximum values were considered. date fitting. the progression in the number of deaths was used to fit the model to an approximate calendar date representing day 0. for the representative typical case of the uk, this corresponded to mar 23. figure 1 shows the simulation results for a representative scenario: universal masking at 80% adoption (red) flattens the curve significantly more than maintaining a strict lockdown (blue). masking at only 50% adoption (orange) is not sufficient to prevent continued spread. replacing the strict lockdown with social distancing on may 31 without masking results in unchecked spread. our model suggests a substantial impact of universal figure 2 : simulation results for a representative scenario: universal masking at 80% adoption (red) results in 60,000 deaths, compared to maintaining a strict lockdown (blue) which results in 180,000 deaths. masking at only a 50% adoption rate (orange) is not sufficient to prevent continued spread and eventually results in 240,000 deaths. replacing the strict lockdown with social distancing on may 31 without masking results in unchecked spread. masking. without masking, but even with continued social distancing in place once the lockdown is lifted, the infection rate will increase and almost half of the population will become affected. this scenario, rendered in grey in figure 1 , would potentially lead to over a million deaths in a population the size of the uk. a continued lockdown, illustrated in blue colour, does eventually result in bringing the disease under control after around 6 months. however, the economic and social costs of a "full body lockdown" will be enormous, which strongly supports finding an alternative solution. in the model, social distancing and masking at both 50% and 80% of the populationbut no lockdown beyond the end of mayresult in substantial reduction of infection, with 80% masking eventually eliminating the disease. figure 2 shows the simulation results for a representative scenario: universal masking at 80% adoption (red) results in 60,000 deaths, compared to maintaining a strict lockdown (blue) which results in 180,000 deaths. masking at only a 50% adoption rate (orange) is not sufficient to prevent continued spread and eventually results in 240,000 deaths. replacing the strict lockdown with social distancing on may 31 without masking results in unchecked spread. in the second of our two new theoretical models, we employed stochastic individual agent based modelling (abm) as an alternative monte carlo simulation technique for understanding the impact of universal masking. agent based models have roots in various disciplines. a stochastic agent program can be defined as a agent function f : p → pr(a) which maps possible percept vectors to a probabilistic distribution over possible actions (or to states that influence subsequent actions). in ai, russell and norvig (2009) summarise five classes of intelligent agents: simple reflex agents, model-based reflex agents, goal-based agents, utility-based agents, and learning agents; note, however, that agents may also be sus-ceptible to imperceptible environmental factors such as viruses. holland and miller (1991) discuss artificial adaptive agents for modeling complex systems in economics. bonabeau (2002) surveys agent based models for simulating human systems. as in other disciplines, abm approaches in epidemiology (see, e.g., hunter et al. (2017) . tracy et al. (2018 ), or hunter et al. (2018 ) have several advantages compared to compartmental models which group undifferentiated individuals into large aggregates (like in the above seir simulation). first, because the behavior and characteristics of each agent is independent, they can simulate complex dynamic systems with less oversimplification of rich variation among individuals. second, because agents can be simulated in physical two-or three-dimensional spaces, they can better simulate the geometry of contact between individuals, which is highly relevant in epidemiology. third, the randomization on each run makes the statistical variance more apparent than in the sir family of models, whose smooth curves often misleadingly convey more certainty than warranted. fourth, abms lend themselves well to visualization, as seen in figure 5 , which helps convey the non-linear behavior of complex dynamic systemsan especially relevant advantage when the exponential effect of masking can be counterintuitive in many cultures due to pre-existing cultural biases (leung, 2020) and unconscious cognitive biases (de kai, 2020). the abm approach allows us to put masks on individual agents and to assign properties to those masks, to shed light on the question of how face maskseven nonmedical cloth maskscarry the promise to be so surprisingly effective. the objective is to examine how even a small barrier to individual infection transmission can multiply into a substantial effect on the level of communities and populations. face masks work in two ways: they can protect an infected person from spreading the virus (transmission), and they can limit how much the non-infected individual is exposed to the virus (absorption). traditionally, masks are worn to protect the wearer from being infected by an ill person when in close and prolonged contact. in such classic situations, for instance in hospitals and elderly homes, only medical masks combined with other protective equipment provide protection. comparing different mask materials, medical masks have been found to be up to three times more effective in blocking transmission compared to homemade masks (davies et al., 2013) . surgical masks most efficaciously reduce the emission of influenza virus particles into the environment in respiratory droplets. still, although masks vary greatly in their ability to protect, using any type of face mask (without an exploratory valve) can help decrease viral transmission (sande et al., 2008) . however, the effect of universal masking does not require full protection from disease to be effective in lowering infection rates of covid-19. masks may be especially crucial for containing the covid-19 pandemic, since many infections appear to come from people with no signs of illness. for instance, around 48% of covid-19 transmissions were pre-symptomatic in singapore and 62% in tianjin, china (ganyani et al., 2020) . this suggests that masking needs to be universal and not restricted to individuals who think they may be infected. furthermore, the sars-cov-2 virus is known to spread through airborne particles and quite possibly via aerosolised droplets as well according to service (2020) , van doremalen et al. (2020), santarpia et al. (2020) , and liu et al. (2020) . it may linger in the air for and travel several meters, which is why social distancing rules require at least 2 meters between individuals to be effective. as a contrastive baseline we employed a compartmental seir model with the same parameters as given for our seir experiments of section 3. for the new agent based model, we implemented an environment consisting of a square wraparound twodimensional space, within which a population of individual agents reside in four states: susceptible (s), exposed (e), infectious (i) and recovered (r). the wraparound space means that agents who move outside a border reenter the square from the opposite side. as in our seir models, the initial infected population (init i ) was set to 1%, and all others to 0%. the size of the total population was set to 200, but the wraparound feature of the twodimensional space in effect represents arbitrarily larger figure 3 : three successive randomised runs of the agent based model for 300 days, with no mask wearing. blue is susceptible, orange is exposed, red is infected, and green is recovered. the contrastive seir baseline model's predicted curves are shown in thinner, fainter lines. the abm runs produce curves with a fine granularity of randomisation, centering on average around the ode based seir curves. spaces that are approximated by replicated square tiles, thus giving more accurate dynamics without boundary effects from small spaces. to best fit the same empirical characteristics of covid-19 spread as our seir models, we again set σ = 1/5.2 and γ = 1/12.39. note that β is inapplicable in the abm since infection transmission between individuals arises from physical proximity, which is more realistic than randomly infecting other individuals anywhere with some probability β with no regard to their physical location. in the baseline monte carlo simulation, agents decide on a random destination location within a parameterised radius of their current point, then proceed at a parameterised speed to move there, and then repeat the process iteratively. we adjusted such abm-specific parameters, as well as physical exposure distance, to optimise fit to the baseline seir model curves, assuming none of the population to be wearing masks. again, this was done so as to best approximate known covid-19 dynamics. abm runs were for 300 days from the onset of the out-break since empirically, the emergent seir curves stabilise before the 300th day. to model the impact of masking, the following masking parameters can be varied: mask wearing. gradual increases (or decreases) in mask wearing can be modelled using parameterised rates of masking m (or unmasking u ) in the proportion of unmasked (or masked) individuals. the parameters m min and m max also allow modelling the minimum and maximum absolute numbers of masked agents. these masking parameters can be dynamically adjusted any time during any abm run, to simulate varying policy decisions and cultural mindset shifts. mask characteristics. varying degrees of mask effectiveness are modelled by the mask transmission rate t and mask absorption rate a, which denote the proportion of viruses that are stopped by the mask during exhaling (transmission) versus inhaling (absorption), respectively. we set t = 0.7 and a = 0.7 to model the use of inexpensive, widely available, and even nonmedical or homemade masks with only 70% effectiveness for universal masking, and not higher quality n95, n99, n100, ffp1, ffp2, or ffp3 masks which in many regions need to be reserved for medical staff. abm simulation shows that universal masking can significantly reduce virus spread if adopted sufficiently early, even if the masks are nonmedical or homemade. figure 3 shows three successive runs for the baseline m = 0 case with zero mask adoption. each dot (which is in motion during simulation runs) represents an individual agent, who may become exposed to the virus through proximity to other agents who are infectious. blue dots are healthy susceptible agents, orange dots are exposed agents, red dots are infected agents, and green dots are recovered agents. a dot with a white rectangle on it represents an agent who is wearing a mask. the three baseline abm runs show how chance plays a significant role in the dynamics of virus spread. since each simulation run is randomised, to decrease variance requires observation over multiple runs. on average, the baseline case with zero mask adoption adheres to the simpler seir model's predicted curves. figure 4 compares typical runs for four scenarios that simulate how covid-19 spreads among individual agents under different masking scenarios, with the contrastive baseline seir model curves shown in thin lines as a reference: (a) m 0 = 100% meaning that the entire population adopts mask at the onset of the outbreak on day 0; (b) m 0 = 0%, m 50 = 90% meaning that none of the population is wearing masks at the onset but that nearly universal masking is instituted on day 50; and (c) m 0 = 0%,m 50 = 50% meaning that none of the population is wearing masks at the onset but that half of the population adopts masks on day 50, and (d) m 0 = 0%, m 75 = 90% meaning that none of the population is wearing masks at the onset but that nearly universal masking is instituted on day 75. in scenario (a), a dramatic decrease in the number of infections is evident as a result of universal masking at the onset of the outbreak. unfortunately, most regions outside east asia missed the time window for scenario (a). in scenario (b), even though the population is not initially wearing masks, if universal masking is instituted by day 50, good chances of dramatic suppression of infection rates can still be achieved. fortunately, this option is within reach of most regions at the time of writing. in scenario (c), again the population is not initially wearing masks. on day 50, half the population dons masks, but unlike scenario (b) which succeeds with 90% universal masking, unfortunately 50% is an insufficient level of mask adoption to suppress infection rates to a significant degree. in scenario (d), the population again is not initially wearing masks, but unlike scenario (b) the 90% universal masking is not instituted until day 75, instead of day 50. waiting too long unfortunately greatly decreases the degree to which infection rates can be suppressed. to help policy makers and the general public gain a more concrete feel for how masks impact the dynamics of virus spread, we have made available online 3 an interactive visualisation tool for the abm simulation model, as shown in figure 5 . the default view allows direct adjustment in real time of the percentage of masked individual agents through a slider control. optional advanced controls allow playing with various scenarios: whether masking is used, the adoption rate of masking, virus transmission and absorption rates through masks of varying quality, as well as other modelling parameters such as the initial numbers of susceptible, exposed, infected, or recovered agents, and the contrastive baseline seir model parameters. we collected a new data set describing the degree of success in managing covid-19 by countries or regions segmented by the prevalence or enforcement of universal masking. the data set covers (a) a selection of 38 countries or provinces in asia, europe and north america that have similar, high levels of economic development (based on world bank gdp purchasing power parity per capita), (b) detected covid-19 cases from jan 23 to april 10, 2020, and (c) characteristics of universal masking culture and/or universal masking orders or recommendations by governments. from our data set's 38 selected countries, we computed (a) the daily growth of confirmed cases, as well as (b) reduction from peak of new cases. sorted in increasing order of the daily growth, figure 6 presents these figures alongside features extracted from our data set denoting each country or region's (c) masking culture, (d) universal masking policy, and (c) lockdown policy. additional clarification on definitions of a couple of these features follow. masking culture is defined as an established practice by a significant section of the general population to wear face masks prior to the start of the covid-19 pandemic. a cursory review of the scientific literature and the general press has identified japan, thailand, vietnam (burgess and horii, 2012) , china's urban centers (kuo, 2014 ), hong kong (cowling et al., 2020 , taiwan, singapore and south korea (yang (2014) , jennings (2020)) as countries with such a consistent practice, at least in the decade predating the covid-19 pandemic. nevertheless, the notion of "culture" should not imply that the practice of face mask wearing has been extensive and consistent throughout time. for example, though this practice figure 6 : epidemic daily growth and reduction from peak daily growth, together with masking culture, universal masking policy, and lockdown policy, from january 23 to april 10, 2020 for selected list of countries or provinces with high gdp ppp per capita in asia, europe and north america. universal masking was employed in every region that handled covid-19 well. sources: john hopkins, wikipedia, voa news, quartz, straits times, south china morning post, abcnews, time.com, channel new asia, moh.gov.sg, reuters, financial times, yna.co.kr, nippon.com, euronews, spectator.sme.sk may have fit with preexisting taoist and health precepts of chinese traditional medicine, its actual emergence may be relatively recent, starting with the industrialization of japan at the start of the xxth century and both the flu pandemics of the xxth century as well as the rise of particle pollution (yang, 2014) . the rest of the above-listed east asian countries has followed the same course in the second half of the xxth century, including china as it was confronting a severe particle pollution crisis in the first part of the 2010s (kuo (2014) , li (2014) , hansstein and echegaray (2018)). beyond price, availability and government recommendation, the actual practice of masking in the asian general population may be mediated by factors such as social norms or peer-pressure, perception of one's competence, past behaviors or perception of the danger (hansstein and echegaray, 2018). as an example of the latter, in hong kong, masking was practiced by 79% of the general population during the 2003 sars outbreak, but by only a maximum of 10% of the general population during the influenza a pandemic in 2009 . universal masking policy. additionally, to the extent that government recommendations or mandatory orders may shape perceptions and assist in masks availability, it may amplify the masking practice in the general population. it can thus be assumed that the maximum potency of universal masking in the context of epidemics may be reached when a government issues a mandatory or highly recommended order to the general population, issued at an early date, supported by the availability of face masks and amplified by a pre-existing "masking culture". in that case, we make the reasonable assumption that such national situations may be used to validate our seir and abm predictive models at maximum values (80-90%) for the percentage of the general population wearing masks. we also computed two additional meta-features to classify successful management of the epidemic outbreak. these meta-features help to highlight both (a) success in suppressing growth from the start (e.g., hong kong or taiwan) or (b) success in managing the epidemic by reducing the number of new cases after a peak (e.g., south korea). successful suppression of daily growth is defined as being below 12.5% daily growth (equivalent to number of cases doubling at the slower pace of 6 days or more) once the number of detected cases first reached 30. these daily successful reduction from peak is defined as a recent, significant (>60%) reduction of new cases calculated as the average of the last five days before april 10, 2020 compared to the average of the three highest number of daily new cases up to april 10, 2020 starting from the date when the number of detected cases first reached 30. again, these reductions from peak are highlighted in green in figure 6 . results bear out the predictions made by our seir and agent-based models as described in sections 3 and 4. in figure 6 , the green (successful supression of daily growth and/or reduction from peak) areas show that as of april 10, 2020, an overwhelming majority of countries or regions that have best managed covid-19 out-breaks were countries or regions with either (1) established universal masking cultures or (2) mandatory orders or government recommendations supported by significant and early mask production destined for the general population. these countries or regions include taiwan, south korea, singapore, japan, autonomous special administrative regions such as hong kong or macau, and chinese provinces such as beijing, shanghai, or guangdong. in effect, masking in public has been required in taiwan, metropolitan areas in china such as shanghai and beijing (as well as guangzhou, shenzhen, tianjin, hangzhou, and chengdu), japan, south korea, and other countries (morgunov et al., 2020) . on the other hand, the red (strict lockdown without universal masking) areas show that most of the countries which have adopted mass testing, tracking and quarantining, but lack a universal masking culture and clear recommendations and availability for universal masking, have not achieved an equiv-alent level of covid-19 epidemic control as of april 10, 2020. this nearly perfect correlation between early universal masking and successful management of covid-19 outbreaks bears out our seir and abm predictions. in figure 7 , daily growth curves were extracted from our data set in order to reveal the impact of universal masking on epidemic control on a time axis. results show that universal masking is nearly perfectly correlated with lower daily growth rates of covid-19 cases over time, again validating the predictions from our seir and agent based models. in figure 8 , daily growth was plotted against versus percentage reduction from peak daily daily growth. green points, representing countries or regions with early universal masking, disproportionately fall within the two lower quadrants which represent successful management of covid-19 outbreaks. red points, representing countries with strict lockdowns but not universal masking, nearly all fall in the two upper quadrants which represent less successful management of covid-19 outbreaks. light green points, representing countries or regions with late universal masking, tend to fall in the middle regions. again, the strong correlation of universal masking with successful control of covid-19 case growth bears out our seir and agent based models' predictions. validation of the need for universal masking. these validations highlight the gradual nature of the protection against covid-19 achieved with a higher fraction of the population practicing masking, as observed in the seir and abm simulations when comparing situations with 80-90% universal masking versus only 50% masking or none. in countries or provinces with masking culture and universal masking orders or recommendations before march 15, 2020, the average daily growth was 5.9% and the reduction from peak was 74.6%. in the countries without masking culture and universal masking orders or recommendations after march 15, 2020, the average daily growth was 14.2% and the reduction from peak was 45.8%. finally, for the rest of the other countries, the average daily growth was 17.2% and the reduction from peak was 37.4%, the lowest results of the sample. the latter group includes countries that have gone into "strict lockdown" (or mass home quarantine) for 20 out of 27 countries (74%). this is much higher than for the intermediate group of countries without masking culture and "late" universal masking orders (2 out 4, or 50% of the sample), or the first group of countries and provinces with masking culture and "early" universal masking orders. in that first group, no countries or provinces had to endure "strict lockdown". validation of the need for early universal masking. yet even within this first group, the strength of early universal masking recommendations from the government may impact the proportion of the general population actually wearing masks and thus the level of epidemic control, as per our models' seir and abm predictions. for example, singapore initially encouraged people to wear masks only when feeling unwell. then, on april, 5, the government changed policy and decided to distribute reusable face masks to all households (cheong, 2020) . on the other end, hong kong decided by january 24, 2020 to advise the general population to wear surgical masks in crowded places and public transports (hong kong department of health, 2020). as can be observed from figure 6 , as of april 10, 2020, the characteristics for epidemic control in terms of daily growth and peak from reduction are better for hong kong than for singapore. these variations may be related to levels of adherence to masking by the general population. though there are no available data as of april 10, 2020 as per adherence to universal masking in singapore, telephone surveys in hong kong done in february 11-14, 2020 and then in march 10-13, 2020, both after department of health public advice, have shown declared masking adherence at the very high levels of 97.5% and 98.8% respectively when going out . assuming the adherence level to masking was lower in singapore since the general population order came much later, this would support our seir and abm predictions of the need for early institution of universal masking. although these correlations may also be sensitive to other unobserved factors, the theoretical seir and abm predictions as empirically validated in the various ways described here call for urgent policy and public action even as further enquiry is pursued into the effects of masking. our results also confirm and amplify other previous findings. a recent macro-level regression analysis by economists at yale university, taking into account masking cultures and times of country covid-19 policy responses, estimated that growth of covid-19 rates only half that of mask wearing countriesthe growth rate of confirmed cases is 18% in countries with no pre-existing figure 8 : visual representation of epidemic daily growth versus percentage reduction from peak daily daily growth in quadrants showing the impact of universal masking on epidemic control: and reduction from peak, from january 23 to april 10, 2020 for selected list of countries or provinces with high gdp ppp per capita in asia, europe and north america. masking is nearly perfectly correlated with lower daily growth or strong reduction from peak growth of covid-19. sources: john hopkins, wikipedia, voa news, quartz, straits times, south china morning post, abcnews, time.com, channel new asia, moh.gov.sg, reuters, financial times, yna.co.kr, nippon.com, euronews, spectator.sme.sk mask norms and 10% in countries with such norms, while the growth rate of deaths is 21% in countries with no mask norms and 11% in countries with such norms. the authors note that such a 10% reduction in transmission probabilities could correspond to a per capita gain of $3,000-6,000 per each additional cloth mask, and that the economic benefits of each medical mask for healthcare personnel could be substantially larger (abaluck et al., 2020) . our seir and abm models suggests a substantial impact of timely universal masking. without masking, but even with continued social distancing in place once the lockdown is lifted, the infection rate will increase and almost half of the population will become affected. this scenario would potentially lead to over a million deaths in a population the size of the uk. social distancing and masking at both 50% and 80-90% of the populationbut no lockdown beyond the end of mayresult in substantial reduction of infection, with 80-90% masking eventually eliminating the disease. moreover, for a significant chance of mitigating infection growth rates, universal masking must be adopted earlyby day 50 from the onset of covid-19 outbreaks. without masking, lifting lockdown after nine weeks while keeping social distancing measures will risk a major second wave of the epidemic in 4-5 months' time. however, if four out of five citizens start wearing cloth masks in public before the lockdown is lifted, the number of new covid-19 cases could decline enough to exit lockdown and still avoid a second wave of the epidemic. if only every second person starts wearing a mask, infection rates would also decline substantially, but likely not by enough to prevent the second wave. combined with the correlational empirical evidence, our results highlight the need for mass masking as an alternative to a continued lockdown scenario. for this strategy to be most effective, the vast majority of the population needs to adopt mask wearing immediately. when a well-timed "mouth-and-nose lockdown" accompanies the current "full body lockdown", both the human and economic costs of the covid-19 pandemic can be significantly lowered. our theoretical and empirical results are in line with previous studies suggesting that a high rate of masking may be needed in a population to provide efficient protection from influenza (yan et al., 2019) and that masking can be an effective intervention strategy in reducing the spread of a pandemic (tracht et al., 2010) . furthermore, universal masking can reduce stigmatization of ethnic groups, risk groups, or the sick and contribute to public solidarity (feng et al., 2020) . we urge governments and international bodies who have not yet done so to consider masking as one of the key tools in population policy after the covid-19 lockdowns and until the virus is under control. the analysis presented here supports recent studies (abaluck et al., 2020) , suggesting that the effectiveness of universal masking is comparable to that of social distancing or a societal lockdown with closed workplaces, schools, and public spaces and limited geographical mobility. the results from our simulation help explain the dynamics behind the perplexing advantage in the asian experience of tackling covid-19 compared to the situation elsewhere. our analyses lead to the following key policy recommendations: 1. masking should be mandatory or strongly recommended for the general public when in public transport and public spaces, for the duration of the pandemic. 2. masking should be mandatory for individuals in essential functions (health care workers, social and family workers, the police and the military, the service sector, construction workers, etc) and medical masks and gloves or equally safe protection should be provided to them by employers. cloth masks should be used if medical masks are unavailable. 3. countries should aim to eventually secure mass production and availability of appropriate medical masks (without exploratory valves) for the entire population during the pandemic. 4. until supplies are sufficient, members of the general public should wear nonmedical fabric face masks when going out in public and medical masks should be reserved for essential functions. 5. the authorities should issue masking guidelines to residents and companies regarding the correct and optimal ways to make, wear and disinfect masks. 6. the introduction of mandatory masking will benefit from being rolled out together with campaigns, citizen initiatives, the media, ngos, and influencers in order to avoid a public backlash in societies not culturally accustomed to masking. public awareness is needed that "masking protects your communitynot just you". the effectiveness of universal masking in a given population is likely to depend on (a) the type of masks used, (b) the acceptance of masking in the population, (c) the level of contagion of the virus, and (d) what other interventions have been applied. from this perspective, the central european experience will be highly informative, since it represents the first major shift to universal masking in a formerly non-masking culture. the effects of this pioneering intervention on infection rates and fatalities will appear only in the forthcoming weeks, although slovakia and slovenia are currently showing early indications of progress (see figure 7) . in any case, they illustrate that a country with no prior history of mask wearing in public may rapidly change course, and quickly adopt masks as a non-stigmatisedeven street smartway to express caring and solidarity in the community. the medical and social risks of increased infections need to be countered by proper advice in the public domain. some studies do indicate negative effects of naive improper cloth mass use, for instance higher risks of infection due to moisture retention, reuse of poorly washed cloth masks, and poor filtration in comparison to medical masks (macintyre et al., 2015) . to address concerns that lay individuals may use both medical and/or cloth and paper masks incorrectly, masking techniques and norms need to be taught with targeted information to different demographics, just as proper handwashing and social distancing techniques have been taught. the case for universal cloth mask adoption and policies to increase supply of medical masks for health workers pandmie de covid-19 : mesures barrires renforces pendant le confinement et en phase de sortie de confinement proceedings of the national academy of sciences of the united states of america can physical interventions help reduce the spread of respiratory viruses? risk, ritual and health responsibilisation: japans safety blanket of surgical face mask-wearing. sociology of health and illness coronavirus: most workplaces to close, schools will move to full home-based learning from next week, says pm lee. the straits times impact assessment of non-pharmaceutical interventions against coronavirus disease 2019 and influenza in hong kong: an observational study. the lancet public health testing the efficacy of homemade masks: would they protect in an influenza pandemic? the disastrous consequences of information disorder erupting around covid-19: ai is preying upon our unconscious cognitive biases rational use of face masks in the covid-19 pandemic ten weeks to crush the curve | nejm estimating the generation interval for covid-19 based on symptom onset data. medrxiv but a fast, coordinated response to covid-19 is essential national coronavirus response: a road map to reopening exploring motivations behind pollution-mask use in a sample of young adults in urban china artificial adaptive agents in economic theory press release, scientific committee on emerging and zoonotic diseases and the scientific committee on infection control under the centre for health protection (chp) of the department of health make and wear a homemade mask to slow the spread of covid-19. #masks4all kelleher. a taxonomy for agent-based models in human infectious disease epidemiology an open-data-driven agent-based model to simulate infectious disease outbreaks not just coronavirus: asians have worn face masks for decades. voice of america chinese urbanites are spending millions on anti-pollution masks-and most of them don't do anything respiratory virus shedding in exhaled breath and efficacy of face masks why face masks are encouraged in asia, but shunned in the china's face mask industry under scrutiny as pollution worsens. reuters aerodynamic characteristics and rna concentration of sars-cov-2 aerosol in wuhan hospitals during covid-19 outbreak | biorxiv. biorxiv a cluster randomised trial of cloth masks compared with medical masks in healthcare workers its time to make your own face mask status of face mask wearing around the world who opens door to broader use of masks to limit spread of coronavirus. reuters artificial intelligence: a modern approach professional and home-made face masks reduce exposure to respiratory infections among the general population transmission potential of sars-cov-2 in viral shedding observed at the university of you may be able to spread coronavirus just by breathing, new report finds would everyone wearing face masks help us slow the pandemic? science mathematical modeling of the effectiveness of facemasks in reducing the spread of novel influenza a (h1n1) agent-based modeling in public health: current applications and future directions. annual review of public health emmie de wit, and vincent j. munster. aerosol and surface stability of sars-cov-2 as compared with sars-cov-1 world health organization. coronavirus disease (covid-19) advice for the public: when and how to use masks. world health organization advice on the use of masks in the context of covid-19: interim guidance modeling the effectiveness of respiratory protective devices in reducing influenza outbreak a quick history of why asians wear surgical masks in public