key: cord-257698-ed2tqn35 authors: wong, raymond s.m.; hui, david s. title: index patient and sars outbreak in hong kong date: 2004-02-17 journal: emerg infect dis doi: 10.3201/eid1002.030645 sha: doc_id: 257698 cord_uid: ed2tqn35 during the global outbreak of severe acute respiratory syndrome (sars) in 2003, treatment was empiric. we report the case history of the index patient in a hospital outbreak of sars in hong kong. the patient recovered after conventional antimicrobial therapy. further studies are needed to address treatment of sars, which has high attack and death rates. s evere acute respiratory syndrome (sars), a new disease that is highly contagious, has caused a major impact worldwide. treatment of this disease remains empiric. this report describes the natural history of a case of sars in a young, previously healthy patient who received no specific therapy for infection with sars-associated coronavirus (sars-cov). he was the index patient in a large hospital outbreak in prince of wales hospital in hong kong (1) . in early march 2003, a 26-year-old man was admitted to a general medical ward of the prince of wales hospital; he had been ill for 1 week with fever, chills, and rigor. he had had a cough productive of whitish sputum for 2 weeks. he also had diarrhea and had vomited several times before his admission. his previous health had been good, and he had no history of recent travel. physical examination showed a temperature of 40.2°c and bronchial breath sounds at the right upper zone lung field. chest x-ray confirmed right upper lobe consolidation ( figure, part a) . a complete blood profile on admission showed a leukocyte count 3.1 x 10 9 /l, absolute neutrophil count 2.0 x 10 9 /l, lymphocyte count 0.7 x 10 9 /l, platelet count 112 x 10 9 /l, and hemoglobin 14.7 g/dl. the patient had mild renal impairment, with a creatinine of 119 µmol/l, urea and electrolytes within normal limits, and alanine transaminase mildly elevated at 90 iu/l (normal <58 iu/l). bilirubin, alkaline phosphatase, and albumin levels were normal. c-reactive protein was 6.5 mg/l (normal <9.9 mg/l). a diagnosis of atypical or viral pneumonia was suspected because of the low leukocyte count and normal c-reactive protein. other laboratory tests were performed, including blood, sputum, and urine cultures, nasopharyngeal aspirate for influenza and parainfluenza, indirect immunofluorescence for respiratory syncytial viral antigen detection, and atypical pneumonia titer (for adenovirus, chlamydia psittaci, q fever, influenza a and b, and mycoplasma). the patient received treatment with intravenous amoxicillin-clavulanate and oral clarithromycin. the patient was housed in a general medical ward with no specific isolation facility. after admission his high fever and productive cough, now with thick, yellowish sputum, persisted. he also complained of progressive dyspnea, headache, dizziness, generalized malaise, and myalgia. his pulse and blood pressure were normal, and his oxygen saturation was approximately 98% on room air. a sputum culture yielded normal oral flora, and sputum smears were negative for acid-fast bacilli. nasopharyngeal aspiration was negative for influenza viruses a and b, respiratory syncytial virus, adenovirus, and parainfluenzavirus types 1, 2, and 3, with the use of commercial immunofluorescence assay. a chest radiograph on day 4 showed progression of pneumonia, with consolidation changes over the right upper and lower lobes (figure, part b) . a repeat complete blood profile showed a leukocyte count of 5.4 x 10 9 /l with persistent lymphopenia and a platelet count of 98 x 10 9 /l. amoxicillin-clavulanate was therefore changed to intravenous cefotaxime, 1 g every 8 h; clarithromycin (500 mg twice a day) was continued. as the patient's condition deteriorated progressively and he had difficulty in expectorating sputum, salbutamol, 0.5 g four times a day, driven by a jet nebulizer at 6 l of oxygen per min, was given to assist mucociliary clearance. his oxygen saturation remained normal without supplemental oxygen. starting from day 6, the patient's fever and chest condition gradually improved. however, over the next 2 weeks, 138 persons (mostly healthcare workers) who had been in contact with him had onset of a similar illness with high fever and pneumonia. the patient was subsequently con-firmed to be the index case-patient in this hospital outbreak of sars (1). three family members were also infected. further history showed that he had visited a hotel in kowloon, hong kong, where a 64-year-old physician from southern china had stayed for 2 days; this physician later died of severe atypical pneumonia 10 days after admission to a regional hospital in kowloon (2) . the cause of the illness was not known at the time of the physician's death. our patient was identified as the index case-patient 5 days after the onset of this large outbreak at the prince of wales hospital, as he was the first patient who had the characteristic clinical, radiologic, and laboratory features of sars and had epidemiologic links with other infected persons. after 8 days, use of the nebulized bronchodilator was stopped because of the possibility of enhancing sars transmission, and the patient was isolated in a private room with negative-pressure ventilation. healthcare workers entering the room wore disposable gloves and n95 masks. after the patient completed a 7-day course of cefotaxime and a 10-day course of clarithromycin, his pneumonia recovered gradually, and serial chest radiographs confirmed resolution of his consolidation (figure, part c) . his diarrhea and other systemic symptoms also resolved spontaneously. an immunofluorescence test for antibody against sars-cov subsequently confirmed an elevated titer of 1:5,120 in convalescent-phase serum collected on day 21 of illness. polymerase chain reaction of nasopharyngeal aspirate was negative for coronavirus. convalescent-phase serum was negative for other atypical pneumonia organisms, including adenovirus, c. psittaci, q fever, influenza a and b, and mycoplasma. repeat complete blood count showed that lymphocytes and thrombocytes had returned to normal, along with serum creatinine and alanine transaminase levels. the patient was isolated in a private room until day 27 of his hospital stay, when his nasopharyngeal aspirate and urine samples were confirmed to be negative for sars-cov. repeat chest radiograph at follow-up 2 weeks later showed no residual parenchymal opacity, and the patient remained asymptomatic. this report describes the index patient responsible for the hospital outbreak in the prince of wales hospital (2). he was linked to spread of the virus to more than 100 persons (1). this outbreak, together with similar events in canada (3), singapore (4) and other cities where the source of infection was also related to the chinese physician (5), led to increased awareness of this emerging global infection caused by a novel coronavirus (6) a b c patient was related to failure to apply isolation precautions, as the disease had not been recognized during the early part of his admission. the use of a nebulized bronchodilator may also have enhanced the spread of the virus in the ward, and this practice was stopped for patients with suspected sars after this incident (7). this case report illustrates the natural history of sars in a young, previously healthy patient who received no specific therapy. his clinical features and laboratory parameters were similar to those of other patients with sars (2) (3) (4) (5) . his clinical course followed a typical pattern with progression of pneumonia during the 2nd week of his illness (8) . he was treated presumptively for bacterial community-acquired pneumonia with conventional antimicrobials (9), without antiviral agents or corticosteroids. he started to improve by the 3rd week and subsequently recovered uneventfully. during the global outbreak in 2003, treatment of sars was empiric. several groups have reported the use of ribavirin (2) (3) (4) (5) 7, 8) and corticosteroids (2, 3, 7, 8, 10, 11) with generally favorable outcomes. ribavirin has been associated with substantial adverse reactions, including hemolytic anemia, elevated transaminases, and bradycardia (4) , and has demonstrated no in vitro activity against sars-cov (12) . further studies, preferably with a randomized, placebo-control design, are needed to address treatment of this disease, which has high attack rates and is frequently fatal. the sars epidemic in hong kong a major outbreak of severe acute respiratory syndrome in hong kong clinical features and short-term outcomes of 144 patients with sars in the greater toronto area severe acute respiratory syndrome (sars) in singapore: clinical features of index patient and initial contacts a cluster of cases of severe acute respiratory syndrome in hong kong identification of a novel coronavirus in patients with severe acute respiratory syndrome sars: experience at prince of wales hospital, hong kong clinical progression and viral load in a community outbreak of coronavirus-associated sars pneumonia: a prospective study guidelines for the management of adults with community-acquired pneumonia. diagnosis, assessment of severity, antimicrobial therapy, and prevention development of a standard treatment protocol for severe acute respiratory syndrome our strategies for fighting severe acute respiratory syndrome (sars) critics slam treatment for sars as ineffective and perhaps dangerous key: cord-289908-7itwc8tm authors: zhu, shuying; tao, jun; gao, huizhi; he, daihai title: age, source, and future risk of covid-19 infections in two settings of hong kong and singapore date: 2020-07-13 journal: bmc res notes doi: 10.1186/s13104-020-05178-z sha: doc_id: 289908 cord_uid: 7itwc8tm objective: to explore and compare the age, source and future risk of covid-19 infection in hong kong sar china and singapore as of march 5, 2020. results: we find significant difference in age patterns of confirmed cases in these 2 localities early in the pandemic. conclusion: we highlight the potential importance of population age structure in confirmed cases, which should be considered in evaluation of the effectiveness of control effort in different localities. the coronavirus disease 2019 (covid-19) pandemic first broke out in wuhan, china in december 2019, and was declared as a global pandemic by the world health organization (who) on 11 march 2020 [1] . as of 15 june 2020, more than 7,000,000 confirmed cases and approximately 5.5% mortality were identified worldwide [2] . the control experience in china showed that the isolation of infected persons, the tracking and quarantine of susceptible individuals, and other social distancing measures could contain this epidemic [3] . singapore and hong kong are both praised as having taken "very effective" measures to intervene in the transmission of new coronavirus by a who official [4] . as of march 5, there were 112 cases in singapore and 106 cases in hong kong. it seemed that there was no significant difference in these 2 numbers given the fact that the measures adopted by singapore were not as strict as those adopted by hong kong but both cities were at high importation risk due to the high proportion of mainland chinese population flow. therefore, some media held the view that singapore adopted a plausibly proper but very effective strategy. in order to scientifically investigate the difference in the effectiveness of singapore and hong kong, we performed several statistical tests of the new coronavirus cases of singapore and hong kong in regard to their age distributions as of march 5. we found that the situation in singapore at this early point in the pandemic may have attributed to the relatively large proportion of infection in the younger generations of its population. however, no significant differences between the effectiveness of the measures adopted by hong kong and singapore government at this time period were noted. we obtained the data of the covid-19 cases of singapore and hong kong from singapore and hong kong's governmental websites [5, 6] . the imported cases and local cases of both districts were studied separately. and we obtained the age structure data of hong kong and singapore separately from public websites as of march 5. in order to compare the difference of age distributions of the 2 infected population and the effects of age structure. we performed the wilcoxon rank-sum test to compare the age distributions of the infected patients in hong kong with those in singapore. and then we divided age into age groups, and we counted the number of cases in each age group. we then used the wilcoxon rank-sum test to compare the difference of age-specific incidence between the 2 populations. lastly, we obtained the agespecific incidence rate by dividing the number of cases in each age group by the population of that group and then compared the age-specific incidence rate by the chisquare test. from the onset of covid-19 to march 5, there have been 23 imported cases in singapore and hong kong, respectively. the age distribution of imported and local cases can be seen in additional file 1: table s1 and figure s1, which was similar to an epidemiological analysis using outsourced data in mainland china [7] . considering that hong kong has a total population of 7.45 million and is more geographically close to mainland china, the risk of importing covid-19 cases should be higher than singapore which has a total population of 5.64 million and less pressure of population mobility with mainland china. results by wilcox test reported a significant difference in age patterns of both imported cases and local cases between the 2 places, with hong kong taking up a higher percentage of elderly cases. nevertheless, this difference is no longer significant after the standardization of imported and local case numbers by each age category in hong kong and singapore respectively, shown in table 1 and fig. 1 . therefore, it is reasonable to assume that the variation in age distribution of the cases might arise from the age structure of the population per se. appropriate travel restrictions may delay the introduction of covid-19 infection. health authorities can provide advice or warnings to travelers. the formulation of the policy must weigh the potential serious economic consequences and the effect of the pandemic control. since the elderly are more vulnerable to get infected after exposure and develop into severe cases, thus the population age structure, among other factors, should be considered when comparing the effectiveness of control measure in different localities. the situations of covid-19 change fast worldwide. the covid-19 data of singapore with age information has been unavailable for public after we first submitted this work. hence, our work performed on merely the data of singapore and hong kong as of march 5. although the patterns of infected cases may stay similar to some extent, the age structures of infected cases in both locations may be different now. supplementary information accompanies this paper at https ://doi. org/10.1186/s1310 4-020-05178 -z. additional file 1: table s1 the cases of hong kong and singapore by march 5. figure s1 histogram of local/imported case numbers by age distribution in hk and singapore by march 5. covid-19: coronavirus disease 2019; who: world health organization. who director-general's opening remarks at the media briefing on covid-19-11 coronavirus disease (covid-19) pandemic how will country-based mitigation measures influence the course of the covid-19 epidemic? singapore for 'very effective' measures to suppress transmission of disease coronavirus: who escalates risk assessment of covid-19 to "very high"-as it happened covid-19: cases in singapore early epidemiological analysis of the coronavirus disease 2019 outbreak based on crowdsourced data: a population-level observational study publisher's note springer nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations none. authors' contributions sz, jt, gh, dh conceived the study, carried out the analysis, discussed the results, drafted the first manuscript, critically read and revised the manuscript, and gave final approval for publication. all authors read and approved the final manuscript. council of hong kong and alibaba (china) co. ltd. collaborative research project (p0031768). the funding agencies had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication. all data and materials used in this work were publicly available. the ethical approval or individual consent was not applicable. not applicable. key: cord-008841-r17qhfsj authors: tomlinson, brian; cockram, clive title: sars: experience at prince of wales hospital, hong kong date: 2003-05-03 journal: lancet doi: 10.1016/s0140-6736(03)13218-7 sha: doc_id: 8841 cord_uid: r17qhfsj nan the lancet • vol 361 • may 3, 2003 • www.thelancet.com commentary the prince of wales hospital (pwh) has been at the forefront of the outbreak of severe acute respiratory syndrome (sars) in hong kong. 1 we relate our experience at this hospital. a working definition of sars is important, 2 although clinical conditions rarely remain within artificial boundaries. some patients might not have all features, others may present unusually. fever is a cardinal symptom but not always so, and is sometimes absent in elderly patients. some patients have presented with diarrhoea or, in at least two cases, with severe acute abdominal pain requiring exploratory laparotomy. all these patients developed typical sars. patients presenting with other respiratory infections must now all be regarded as potential sars cases until proven otherwise. contact with a known case is an important discriminator but, if emphasised too strongly in the diagnostic process, may lead to false positives or negatives. the difficulty of making a firm diagnosis until chest radiographic changes appear has important implications for health-care personnel and for surveillance. three major reasons for spread of infection to health-care workers have been: failure to apply isolation precautions to cases not yet identified as sars, breaches of procedure, and inadequate precautions. every patient must now be assumed to have sars, which has major long-term implications for the health-care system. another reason for spread among health-care workers is infected workers continuing to work despite symptoms, such as mild fever. such individuals must now cease working. however, staying at home can also have disastrous consequences for exposed family members. potential cases therefore require early isolation from both workplace and household. extreme measures are required to protect health-care workers, who account for about 20% of cases. early diagnosis by virus isolation or serological testing is essential to halt the spread of sars. progress has been made with the isolation of the coronavirus. [3] [4] [5] a metapneumovirus was also identified in canada 4 and in many of the cases at pwh. coronavirus appears to be the main pathogen, but dual infections may be possible. such situations are uncommon in human disease, apart from hiv-related infections, but in veterinary medicine combined infections with coronavirus and other agents have been described. 6, 7 the first cases probably occurred in guangdong province in southern china in november, 2002. 8 the term sars appears to have been first used for a patient in hanoi who became ill on feb 26, 2003, and was evacuated back to hong kong where he died on march 12. the physician who raised the alarm in hanoi, carlo urbani, subsequently contracted sars and died. the first case in hanoi had stayed at a hotel in kowloon, hong kong, at the same time as a 64-yearold doctor who had been treating pneumonia cases in southern china. this doctor was admitted to hospital on feb 22, and died from respiratory failure soon afterwards. 9 he was the first known case of sars in hong kong and appears to have been the source of infection for most if not all cases in hong kong as well as the cohorts in canada, vietnam, singapore, usa, and ireland, and subsequently thailand and germany. 10 the index patient at pwh was admitted on march 4, 2003, and had also visited this hotel. he had pneumonia which progressed initially despite antibiotics, but after 7 days he improved without additional treatment. 1 on march 10, 18 health-care workers at pwh were ill and 50 potential cases among staff were identified later that day. further staff, patients, and visitors became ill over the next few days and there was subsequent spread to their contacts. by march 25, 156 patients had been admitted to pwh with sars, all traceable to this index case. 1 one important factor in the extensive dissemination of infection appears to have been the use of nebulised bronchodilator, which increased the droplet load surrounding the patient. overcrowding in the hospital ward and an outdated ventilation system may also have contributed. the second major epicentre in hong kong, accounting for over 300 cases, has been an apartment block called amoy gardens. the source has been attributed to a patient with renal failure receiving haemodialysis at pwh who stayed with his brother at amoy gardens. 11 he had diarrhoea, and infection may have spread to other residents by a leaking sewage drain allowing an aerosol of virus-containing material to escape into the narrow lightwell between the buildings and spread in rising air-currents. sewage also backflowed into bathroom floor drains in some apartments. spread to people in nearby buildings also occurred, probably by person-to-person contact and contamination of public installations. although the rapid spread of the disease in some situations may have been explained, many uncertainties remain. why the disease spread in the kowloon hotel has not been clarified, and there are many other important issues. "super-spreaders" may be prone to carry a high viral load because of defects in their commentary sars: experience at prince of wales hospital, hong kong immune system, as could be the case in the patient with end-stage renal failure implicated in the amoy gardens outbreak and another with renal failure at the centre of an outbreak in singapore. subclinical infections may also occur and will not be recognisable until reliable diagnostic tests are available. procedures causing high risk to medical personnel include nasopharyngeal aspiration, bronchoscopy, endotracheal intubation, airway suction, cardiopulmonary resuscitation, and non-invasive ventilation procedures. cleaning the patient and the bedding after faecal incontinence also appears to be a high-risk procedure. treatments have been empirical. initial patients were given broad-spectrum antibiotics but, after failing to respond for 2 days, were given ribavirin and corticosteroids. patients who continued to deteriorate with progression of chest radiographic changes or oxygen desaturation, or both, were given pulsed methylprednisolone. 1 steroids were used on the rationale that progression of the pulmonary disease may be mediated by the host inflammatory response, similar to that seen in acute respiratory distress syndrome, and produced by a cytokine or chemokine "storm". the clinical impression is that pulsed steroids sometimes produce a dramatic response. however, apparent benefits of steroid treatment have proven to be incorrect before, as in infection with respiratory syncytial virus. 12 lack of knowledge of sars' natural history adds to the difficulty of determining the effectiveness of therapy. some patients have a protracted clinical course with potential for relapses continuing into the second or third week, or beyond. long hospital stays, even in less ill patients, are required, and the high proportion of patients requiring lengthy intensive care, with or without ventilation (23% in the 138 cases from pwh 1 ), and the susceptibility of health-care workers bodes ill for the ability of health-care systems to cope. even when the acute illness has run its course, unknowns remain. continued viral shedding and the possible development of long-term sequelae, such as pulmonary fibrosis or late post-viral complications, means that patients will require careful surveillance. this commentary is dedicated to the frontline health-care staff who have shown courageous devotion to duty throughout this epidemic. department of medicine and therapeutics, chinese university of hong kong, prince of wales hospital, hong kong sar, people's republic of china (e-mail: btomlinson@cuhk.edu.hk) world health organization. case definitions for surveillance of severe acute respiratory syndrome (sars) centers for disease control and prevention. cdc lab analysis suggests new coronavirus may cause sars identification of severe acute respiratory syndrome in canada coronavirus as a possible cause of severe acute respiratory syndrome coronavirus and pasteurella infections in bovine shipping fever pneumonia and evans' criteria for causation viral agents associated with poultry enteritis and mortality syndrome: the role of a small round virus and a turkey coronavirus severe acute respiratory syndrome (sars): multi-country outbreak-update a cluster of cases of severe acute respiratory syndrome in hong kong cdc update: outbreak of severe acute respiratory syndrome-worldwide main findings of an investigation into the outbreak of severe acute respiratory syndrome at amoy gardens a randomized, double-blind, placebo-controlled trial of dexamethasone in severe respiratory syncytial virus (rsv) infection: effects on rsv quantity and clinical outcome the dietary fibre debate: more food for thought this issue of the lancet contains two important papers that associate high intake of dietary fibre with a decreased risk of either colonic adenomas or colorectal cancer. the usa-based study done by the prostate, lung, colorectal, and ovarian cancer screening project team (plco) compared the dietary fibre intake of 33 971 people who on sigmoidoscopy showed no polyps with 3591 people who had at least one histologically-verified adenoma in the distal large bowel. the study involved ten different us centres, with very different dietary practices. the european prospective investigation into cancer and nutrition (epic) consortium used a different approach to reach the same conclusion. they prospectively examined the dietary-fibre intake and incidence of colon cancer in 519 978 people recruited from ten european countries. the findings of both research teams contrast with those of at least three other studies that have been published in the past 4 years, 1-3 all of which found no protective effect of dietary-fibre intake on the development of either colonic adenomas or colorectal cancer. the new results give fresh impetus to fundamental research to determine the reasons for the protective action of dietary fibre, or to establish the definitive clinical trial.the us nurses health study 1 was based on numbers of cases of colorectal cancer as large as in epic, and had a considerable impact on thinking. after its publication, 1 doubts were expressed not only about population recommendations for health but even about the need for continued research. for example, santani-rim and dashwood 4 posed the question about whether it was "time to discontinue antigenotoxicity studies of dietary fibre". of equal concern was the downturn in interest of commercial food companies to do applied research in such areas as high-fibre food products.why did these two groups of studies give such different results? although this question is obviously important, it is very difficult to answer. random variation is unlikely, given the numbers in the population groups involved. conflicting studies would be more difficult to explain if dietary fibre was a wellkey: cord-268789-9b4quuqx authors: zhou, y.; ng, d.m.w.; seto, w.-h.; ip, d.k.m.; kwok, h.k.h.; ma, e.s.k.; ng, s.; lau, l.l.h.; wu, j. t.; peiris, j.s.m.; cowling, b. j. title: seroprevalence of antibody to pandemic influenza a (h1n1) 2009 among healthcare workers after the first wave in hong kong date: 2011-08-31 journal: journal of hospital infection doi: 10.1016/j.jhin.2011.02.017 sha: doc_id: 268789 cord_uid: 9b4quuqx summary during the first wave of an influenza pandemic prior to the availability of an effective vaccine, healthcare workers (hcws) may be at particular risk of infection with the novel influenza strain. we conducted a cross-sectional study of the prevalence of antibody to pandemic influenza a (h1n1) 2009 (ph1n1) among hcws in hong kong in february–march 2010 following the first pandemic wave. sera collected from hcws were tested for antibody to ph1n1 influenza virus by viral neutralisation (vn). we assessed factors associated with higher antibody titres, and we compared antibody titres in hcws with those in a separate community study. in total we enrolled 703 hcws. among 599 hcws who did not report receipt of ph1n1 vaccine, 12% had antibody titre ≥1:40 by vn. there were no significant differences in the age-specific proportions of unvaccinated hcws with antibody titre ≥1:40 compared with the general community following the first wave of ph1n1. under good adherence to infection control guidelines, potential occupational exposures in the hospital setting did not appear to be associated with any substantial excess risk of ph1n1 infection in hcws. most hcws had low antibody titres following the first pandemic wave. prior to the availability of an effective vaccine, healthcare workers (hcws) may have faced particular risk of pandemic influenza a (h1n1) 2009 (ph1n1) infection. infection of hcws during a pandemic is of public health concern not only because of the impact of infection and illness on the hcws themselves but also because hcws have frequent contact with patients who could be predisposed to serious illness if infected with influenza, and substantial rates of absenteeism among hcws could have adverse effects on the healthcare system. 1 in 2009 the institute of medicine and the centers for disease control and prevention recommended that all healthcare workers who would have contact with suspected or confirmed ph1n1 patients should use n95 respirators. recommended practice in hong kong followed world health organization (who) guidelines under which surgical masks should be routinely worn by all healthcare workers, standard droplet precautions should be implemented during contact with influenza patients, and greater precautions including face shields and n95 respirators used when performing aerosol-generating procedures. 2 the first imported ph1n1 case arrived in hong kong on april 30 and, after sporadic imported cases through may, local transmission was identified in mid-june. 3 the first wave peaked in september and had subsided by november. 3, 4 ph1n1 was a notifiable condition throughout the first wave, and 36 000 laboratory-confirmed cases were notified including 1400 hcws, from a local population of 7 million including 150 000 hcws. the hong kong government provided ph1n1 vaccine (sanofi pasteur) for five target groups including hcws starting 21 december 2009, and about 10% of local hcws had received influenza vaccine by march 2010. the infection attack rate among hcws is likely to be greater than that suggested by the notification rate (1400/150 000, 0.9%) because many symptomatic cases did not receive laboratory testing, while a fraction of ph1n1 infections are subclinical. since few individuals aged <60 years had detectable antibody to ph1n1 prior to the pandemic, 4e6 serological studies provide a straightforward way to infer infection attack rates. 4, 5 we conducted a crosssectional study of ph1n1 antibody among hcws in hong kong following the first epidemic wave. we recruited hcws between 11 february and 31 march 2010 in six public hospitals comprising the hong kong west cluster of the local hospital authority, with a total workforce of around 7000 hcws in one acute care teaching hospital and five non-acute hospitals. we established fixed study locations in each hospital, and participants were invited to attend our study site and participate in our study by open advertisement to all cluster employees. hcws were eligible to participate if they were hong kong residents and had worked in the cluster for at least one month. we aimed to recruit at least 500 hcws who had not received ph1n1 vaccine so that we could estimate the prevalence of antibody titre !1:40 to within ae3.5% overall and to within ae8% within 10-year age groups. the study protocol was approved by the institutional review board of the university of hong kong/hospital authority hong kong west cluster. serum specimens collected from participants were kept in a refrigerated container at 2e8 c immediately after collection and delivered to the laboratory at the end of each working day for storage at e70 c prior to testing. sera were tested for antibody responses to a/california/04/2009 (h1n1) by a viral microneutralisation (vn) assay using standard methods. 4, 7 because the vn assay was found to have greater sensitivity for ph1n1 infection than haemagglutination inhibition (hai) in our previous study 7 we used the vn assay as the primary serological test in this study. a titre of !1:40 was taken as the threshold for seropositivity because in a previous study conducted in the same laboratory around 90% of patients with confirmed infection reached a titre of !1:40 by vn at convalescence 8 whereas few individuals had a titre !1:40 by vn before the first pandemic wave. a randomly selected subset of specimens plus all specimens from participants who reported laboratory-confirmed ph1n1 infection were also tested by hai using standard methods. 7 we compared the differences in the proportion of hcws with ph1n1 antibody titre !1:40 between groups with c 2 -tests or fisher's exact test. we compared age-specific proportions of hcws with ph1n1 antibody titre !1:40 with antibody seroprevalence among blood donors determined from a separate community study also conducted after the first wave. 4 we used logistic regression to explore factors associated with antibody titre !1:40. factors that were statistically significant in univariate analyses were included in multivariate models. multiple imputation was used to allow for a small amount of missing data on some characteristics. 9 a total of 703 hcws were recruited; 104 hcws who reported receipt of ph1n1 vaccine were excluded from the following analyses. among the 599 hcws who reported that they had not received ph1n1 vaccine, 74 (12%) had ph1n1 antibody titre !1:40 by vn. in a random sample of 59/599 tested by hai, 9 (15%) had antibody titre !1:40. there was a significant difference in the proportion of hcws with antibody titre !1:40 by age, with greater proportion among younger hcws, and by occupation, with greater proportion among doctors compared with nurses (table i) . in a multivariate analysis, age remained significantly associated with an antibody titre !1:40 and hcws working in the emergency room had a marginally significant higher probability of antibody titre !1:40 (p ¼ 0.06) (table ii) . among the 599 hcws, 19 (3.2%) reported laboratory-confirmed ph1n1 infection during the first wave, and 58% (95% ci: 34e80) of those 19 had antibody titre !1:40 by vn, and 74% (95% ci: 49e91) had antibody titre !1:40 by hai. among the 574 hcws who did not report laboratory-confirmed ph1n1 infection, 11% (95% ci: 8.5e14) table iii shows the comparison of ph1n1 antibody seroprevalence in hcws versus blood donors at the hong kong red cross involved in a separate community study. 4 there was no statistically significant difference in seroprevalence by age between hcws and the community population in march 2010 apart from a marginally significant difference in hcws aged 25e34 years (p ¼ 0.09). in a multivariate logistic regression model for the hcw and community data combined (assuming that none of the community blood donors were hcws), the probability of antibody titre !1:40 varied significantly by age, but not by hcw status (or: 1.40; 95% ci: 0.94e2.08; p ¼ 0.09). the first wave of ph1n1 infection occurred between july and november 2009 in hong kong. 3, 4 the community infection attack rate in the first wave was estimated at around 11%, with much higher attack rates among children. 4 in our study 19/599 (3.2%) unvaccinated hcws reported laboratory-confirmed pandemic h1n1 infection compared with an overall rate of 1% in hcws in hong kong, while 12.4% of unvaccinated hcws had antibody titre !1:40. assuming that the baseline seroprevalence in hcws was similar to the community, the estimated infection attack rate in hcws would have been around 4e15% in different age groups (table iii) , suggesting that the majority of ph1n1 infections in hcws were not laboratory-confirmed. among unvaccinated hcws, 85% of hcws who had pandemic influenza antibody titre !1:40 reported febrile influenza-like illness during the pandemic. whereas some hcws may have had antibody titre !1:40 prior to the pandemic, and others may have had a febrile illness not associated with influenza infection, these data are consistent with most ph1n1 infections being symptomatic. therefore the who recommendation that hcws should withdraw from work while suffering acute respiratory illness appears to be a reasonable precaution to reduce the risk of nosocomial transmission. we did not identify statistically significant age-specific differences in seroprevalence in march 2010 between unvaccinated hcws and blood donors from the general community (table iii) , noting that vaccine coverage in the latter population was very low in march 2010 in hong kong. thus our data are not consistent with an increased risk of ph1n1 infection in hcws, which is in agreement with previous data indicating no excess risk of pandemic influenza in hcws in singapore 10 or seasonal influenza infection in hcws in germany. 11 we also found that there was no significant difference in seroprevalence between hcws in an acute care hospital versus non-acute hospitals, between hcws who did or did not have contact with suspected or confirmed ph1n1 patients, or by presence of school-age children at home (table i) . one study reported higher prevalence of ph1n1 antibody in hcws in taiwan compared with that the general community, although age was strongly associated with seroprevalence, and age distributions differed between the hcw and community samples, possibly explaining the differences in seroprevalence. 12 infection control procedures in hong kong followed the who guidelines. it is likely that the guidelines for the appropriate use of personal protective equipment were stringently adhered to following previous experiences with severe acute respiratory syndrome in 2003 as well as intensive control efforts from dedicated infection control teams. 2 although we did not collect detailed data on adherence to infection control measures, another study reported that failure to comply with standard precautions such as wearing a surgical mask during contact with suspected influenza patients was associated with an increased risk of ph1n1 infection. 2 factors associated with a higher risk of antibody titre !1:40 among unvaccinated hcws included younger age and working in the emergency room, whereas other factors such as occupation (after adjustment for age), number of occupational contact with influenza patients, and seasonal influenza vaccination history were not significantly associated with risk of antibody titre !1:40 (tables i and ii) . younger hcws were more likely to have antibody titre !1:40, consistent with higher population attack rates in younger age groups, 4 although potentially confounded by differences in age-specific ability to mount antibody response to infection. as the first point of contact with most influenza patients in a hospital setting is the emergency room, it is plausible that hcws in the emergency room could face the highest and most frequent risk of infection e even though many patients with influenza-like illness are not admitted. in addition, hcws in the emergency room would tend to see patients earliest in their course of disease, when they might be most infectious. 13 influenza vaccination is the best primary prevention measure against infection, and hcws are often one of the target groups to receive vaccine not only for their direct protection both in the healthcare setting as well as in the community, but also to indirectly protect patients against nosocomial transmission. 1, 11 in hong kong, hcws were one of the target groups for ph1n1 vaccine, but coverage was low following intense media coverage of a series of adverse events potentially associated with ph1n1 vaccine. around 15% of hcws in our study reported receipt of one dose of ph1n1 vaccine, compared with overall vaccine coverage of around 10% of hcws in hong kong. although our results suggest that following who guidelines for infection control was sufficient to prevent substantial excess risk of ph1n1 associated with occupational exposures in a hospital setting, vaccination is still important for protection of hcws against infection in other settings. it is important to note several limitations of our study. first, we conducted a cross-sectional seroprevalence study following the first ph1n1 wave, and we did not have baseline (pre-pandemic) data to enable us to infer accurately attack rates among hcws. analysis of serological data may misclassify the infection status of some individuals. however, few adults in hong kong had antibody to ph1n1 at titre of !1:40 prior to the first wave (table iii) , 4 whereas most individuals infected with ph1n1 did go on to develop antibody titres !1:40. 5 second, although we did not observe any substantial excess risk of ph1n1 infection in hcws compared with the general community, it is possible that a smaller excess risk did exist but may have been masked by community exposures in our study. larger and more detailed studies of hcws are certainly warranted to help understand the risk of nosocomial infection and the effectiveness of preventive measures. third, participants in our study were a convenience sample covering hcws in both acute and non-acute hospitals; a random sample would have been ideal albeit more difficult to implement with a high response rate. finally, we recruited hcws who were working in six public hospitals on hong kong island and our results may not generalise to hcws working in other regions of hong kong or local private hospitals and outpatient clinics. our data suggest that generally hcws in hospitals in hong kong, operating under the who infection control guidelines, did not have a higher risk of infection associated with their occupation compared with the general community. furthermore, following the first pandemic wave, most hcws did not have antibody titres at levels that would typically be considered protective against infection, since vaccine uptake was very low. requiring influenza vaccination for health care workers: seven truths we must accept prevention of nosocomial transmission of swine-origin pandemic influenza virus a/h1n1 by infection control bundle the effective reproduction number of pandemic influenza: prospective estimation the infection attack rate and severity of 2009 pandemic influenza (h1n1) in hong kong incidence of 2009 pandemic influenza a h1n1 infection in england: a cross-sectional serological study cross-reactive antibody responses to the 2009 pandemic h1n1 influenza virus comparative epidemiology of pandemic and seasonal influenza a in households effect of clinical and virological parameters on the level of neutralizing antibody against pandemic influenza a virus h1n1 multiple imputation for missing data in epidemiological and clinical research: potential and pitfalls influenza a(h1n1) seroconversion rates and risk factors among distinct adult cohorts in singapore seasonal influenza risk in hospital healthcare workers is more strongly associated with household than occupational exposures: results from a prospective cohort seroprevalence of antibodies to pandemic (h1n1) 2009 influenza virus among hospital staff in a medical center in taiwan viral shedding and clinical illness in naturally acquired influenza virus infections we thank p. ching, s.k. pang, a. wong and a. yuen for facilitating our study, and l. chan, q. liao, t. so and j. wong for assistance with the fieldwork. we thank v. fang for technical assistance. key: cord-297618-9ka3y2y1 authors: chau, pui hing; li, wei ying; yip, paul s. f. title: construction of the infection curve of local cases of covid-19 in hong kong using back-projection date: 2020-09-21 journal: int j environ res public health doi: 10.3390/ijerph17186909 sha: doc_id: 297618 cord_uid: 9ka3y2y1 this study aimed to estimate the infection curve of local cases of the coronavirus disease (covid-19) in hong kong and identify major events and preventive measures associated with the trajectory of the infection curve in the first two waves. the daily number of onset local cases was used to estimate the daily number of infections based on back-projection. the estimated infection curve was examined to identify the preventive measures or major events associated with its trajectory. until 30 april 2020, there were 422 confirmed local cases. the infection curve of the local cases in hong kong was constructed and used for evaluating the impacts of various policies and events in a narrative manner. social gatherings and some pre-implementation announcements on inbound traveler policies coincided with peaks on the infection curve. the world health organization (who) declared the coronavirus disease (covid-19) as a pandemic [1] . it has been demonstrated that social distancing, contact tracing, patient isolation, early diagnosis, city lockdown, and travel restrictions were effective measures in slowing down the spread of covid-19 [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] . for the public to be prepared for dramatic changes, both physical and mental, a pre-implementation announcement is usually made. depending on the actual time of the announcement, the time gap ranges from less than 24 h to a couple of days. to date, the impact of this window of infection and its unintended consequences have not been investigated. apart from using simulations under the susceptible-exposed-infectious-removed (seir) model, an examination of the trajectory of the epidemic curve provides some insight into the impacts of various policies and events in a narrative manner. with one exception [14] , to date, those investigations on the effectiveness of preventive measures were based on epidemic curves mainly constructed using the date of diagnosis or onset [2, 6, [8] [9] [10] [11] [12] [13] . the estimated mean incubation period of the covid-19 varies from 4.9 to 7.4 days across studies [15] . the epidemic curve based on the infection date, however, would be more accurate to assess the effectiveness of various measures and the impacts of the events. as the date of infection is unobservable, it has to be estimated. the back-projection technique was originally developed to construct the infection curve for the human immunodeficiency virus (hiv)/acquired immune deficiency syndrome (aids) epidemic [16, 17] . in 2003, the authors applied the back-projection method to the severe acute respiratory syndrome (sars) epidemic [18] . the current study constructed an epidemic curve based on the date of infection estimated by the back-projection method to minimize the effects of the incubation time and reflect the possible impacts of various measures and events better. up until 31 august 2020, hong kong had 4811 confirmed covid-19 cases with 89 deaths. from january to april 2020, most of the cases were imported and clustered with known sources, and were considered as the first two waves of the infection. the third wave started in july, still continuing at the time of this publication. most of those cases were local, and the sources of many of which were unknown. the present study focused on the first two waves of local infections in hong kong. all the government announcements were systematically recorded on the official website, thus providing reliable information on the pre-implementation announcement dates and the implementation dates of the preventive measures. this provided a trusted source to examine the possible association between the pre-implementation announcements and the infection curve in a narrative manner. our objective was to estimate the infection curve of the local cases of the first two waves of covid-19 in hong kong using the back-projection method and explore the effectiveness of the preventive measures, including the possible impacts of the pre-implementation announcements by the local government. the daily number of confirmed cases of covid-19 reported by 30 april 2020 was obtained from the website of the centre for health protection, hong kong (https://www.chp.gov.hk/). a confirmed case was defined as a person with laboratory confirmation of covid-19 infection, irrespective of clinical signs and symptoms [19] . as the date of infection of the imported cases cannot reflect the impact of the preventive measures implemented locally, all imported cases were excluded from the analysis. until 30 april 2020, there were 1038 confirmed cases in hong kong, of which 422 were local cases and included in this study. among the 422 cases, 46 were asymptomatic and the date of onset was proxied by the date of report in the primary analysis. a sensitivity analysis was performed by excluding the asymptomatic cases. an infected person goes through an incubation period before the onset of the symptoms. the time when the symptoms appear is the onset time. the term "onset cases" was used to refer to the cases with onset of the symptoms on a particular day. there was also a delay between the onset of symptom(s) and the confirmation of cases. figure 1 shows the temporal relation between infection, onset, and confirmed cases. in this study, daily onset cases were used for the back-projection method. let t = 1, 2, . . . , τ denote the days, where t = 1 denotes 12 january 2020. as the earliest onset date was 22 january 2020, it was assumed that there was no infection 10 days prior to that date. furthermore, this was consistent with the fact that the earliest arrival date of imported cases was 14 january 2020. as the last time point was 30 april 2020, τ had been set to 110. the daily mean number of onset covid-19 cases (µ t ) was expressed in terms of the daily mean number of infection (λ s , s=1, . . . , t) by the convolution equation: where f t-s,s is the probability function of the incubation period, that is, the probability that an individual infected at time s developed a symptom after a period of length t-s. in other words, infected cases on day 1 went through an incubation period of t-1 days with the probability specified by the probability function of the incubation period and had onset of symptoms on day t; then infected cases on day 2 went through an incubation period of t-2 days; infected cases on day 3 went through an incubation period of t-3 days and so on, up to infected cases on day t that went through an incubation period of 0 days. the sum of all these cases was the total number of onset cases on day t. based on a recent meta-analysis on the incubation period established from eight studies [15] , the probability function of the incubation period of covid-19 was taken as a log-normal distribution with scale and shape parameters of 1.63 and 0.5, respectively. this corresponded to a mean of 5.8 days, a median of 5.1 days, and a 95th percentile of 11.7 days. the ems (estimate-maximize-smooth) algorithm was used to estimate the daily number of infection and pointwise 95% confidence interval was constructed by the bootstrap procedure. details of the back-projection method are reported elsewhere [16, 17] . python was used for running the algorithm [20] . the estimated infection curve was closely examined in relation to the major events and policies announced and/or implemented by the local government. the major events and policies were obtained from the official websites (www.info.gov.hk/gia/ and www.news.gov.hk). table s1 shows the selected government policies and major events in the period under examination. the number of covid-19 infections over this period was estimated to be 422. figure 2 gives the estimated daily number of covid-19 infections, the pointwise 95% confidence intervals on the estimated infection number, and the observed daily number of onset cases for the period from 12 january 2020 to 30 april 2020. it was estimated that the first infection occurred around 18 january 2020, roughly four days after the arrival of the first imported case on 14 january 2020. the highest peak was estimated around mid-march 2020, which was in the middle of the second wave of infection which started in march. zero infection was estimated since 4 april 2020. in the first wave, the estimated infected cases in late january 2020 could be mainly attributable to the social and family gatherings around the chinese new year. it was reported from contact history tracing that 6 infected people attended a family dinner in north point on 26 january 2020, 11 infected people attended a family gathering at a party room in kwun tong on 26 january 2020, and 13 infected people visited a buddhist worship hall in north point between 25 january and early february 2020. in the second wave, it was reported that there were two large-scale gatherings on 14 march 2020, one involved 80 guests at a wedding party and the other involved over 100 guests at a private party. a total of 14 confirmed cases were reported from those two gatherings. this was consistent with the peak in the infection curve on 14 march 2020. furthermore, 72 staff and customers of some pubs and bar areas were infected, and 31 more confirmed cases had epidemiological link to these cases. the onset date of this infection cluster was reported to be from 10 march to 13 april 2020, implying infection from around early march to early april. on 24 march 2020, it was reported that 7 people went to a karaoke and all were infected. on 26 january 2020, an announcement was made to ban inbound travelers who had visited the hubei province in the past 14 days prior to its actual implementation at midnight on 27 january 2020. from 25 to 29 january 2020, numerous policies were announced and implemented, including activation of the emergency response level, cancellation of large-scale events, quarantine of close contacts of confirmed cases, health advice to residents returning from the hubei province and other parts of china, suspension of non-emergent government services, closure of public facilities, home office arrangement for civil servants, and substantial reduction of traffic between mainland china and hong kong. as the peak of the first wave around 24-28 january 2020 was dominated by cluster infections during social gathering, it was difficult to observe potential influence from these policies. the announcement on 28 february 2020 about mandatory quarantine for inbound travelers who had been to emilia-romagna, lombardy, or the veneto regions in italy or iran in the past 14 days coincided with a local maximum. the curve, however, slightly went down after implementation of the policy on 1 march 2020. there was also an announcement on 6 march 2020 about the health declaration requirement on all inbound travelers effective from 8 march 2020. the curve declined slightly forthwith. the peaks on 13-15 march and 18-21 march 2020 were the key features of the second wave. during 2-22 march 2020, some non-emergent government services and public facilities resumed, and civil servants returned to work in the office. various policies on inbound travelers were announced and implemented during that period. however, their associations with the infection curve might be masked by the cluster infections in the wedding party, private party and the pubs and bar areas during the same period. on 10 march 2020, the government announced mandatory quarantine on inbound travelers from the whole of italy, france (bourgogne-franche-comte and grand est), germany (north rhine-westphalia), japan (hokkaido), and spain (la rioja, madrid, and pais vasco). this announcement coincided with the rise on the infection curve. on 13 march 2020, the government further announced mandatory quarantine on inbound travelers who had visited the schengen area countries. moreover, on 15 march 2020, mandatory quarantine was announced on all inbound travelers who had traveled to ireland, the united kingdom, the united states, and egypt. then, on 17 march 2020, mandatory quarantine was announced for all inbound travelers from all overseas places, which activated the downward trend again. starting from 20 march 2020, inbound travelers with symptoms of upper respiratory symptoms were tested at designated test centers and they had to wait for the results. for the second time, non-emergent government services and public facilities were closed from 23 march 2020, and the civil servants resumed to home office arrangement again. after implementation of these policies, the infection curve declined. against the declining trend, the infection number rebounded on 30 march 2020. however, the increase appeared to be not related to the pre-implementation announcements on 27 march 2020, which involved (i) strict operational instructions on the catering business (limiting the number of seats to half of the capacity, minimum distance of one and a half meters between tables, and a maximum of four seats per table); (ii) closure of scheduled premises (including amusement game centers, bathhouses, fitness centers, places of amusement, places of public entertainment, and party rooms); and (iii) ban of groups over four people in public places. the first two policies were implemented on 28 march 2020 and the third policy was implemented on 29 march 2020. furthermore, closure of karaoke, mahjong-tin kau, and nightclub establishments was announced on 1 april 2020 and closure of bars and pubs was also announced on 2 april 2020, and implemented on 1 and 3 april 2020, respectively. after implementation of all those policies, the infection number continued to fall to zero by 4 april 2020. the sensitivity analysis that excluded the asymptomatic cases ( figure s1 ) gave a similar trajectory of the infection curve. it was noted that the local maxima from 28 february to 1 march 2020 and from 29 march to 3 april 2020 were not observed in the sensitivity analysis that excluded the asymptomatic cases. the peak on 19 march 2020 in the sensitivity analysis was lower than that which included the asymptomatic cases. it might be that those infected in those periods were mostly asymptomatic. the current study constructed the infection curve of local confirmed covid-19 cases in hong kong. from studying the estimated curve closely with the major events and preventive measures, it was observed that a strict mandatory quarantine order on inbound travelers coincided with the decline from the peak in the infection number. however, some pre-implementation announcements of such policies and social gatherings corresponded with sharp increases in the infected cases. the closure of public facilities and home office arrangement might have helped to slow down the spread. it is common practice around the globe to pre-announce government policies. in hong kong, the press conference was usually held at 4:30 pm. for policies to be implemented the following day, such an announcement would only leave several hours before the actual implementation. to stir up reactions, such a short period may not be sufficient. for transportation from overseas countries to hong kong, more time is needed for preparation. thus, the announcements of mandatory quarantine on people returning from overseas were made over 24 h prior to implementation. instead of using the time to well plan for the 14-day quarantine, those from overseas, however, rushed back to hong kong to avoid the mandatory quarantine. it was reported that 46 confirmed imported cases (the largest daily imported cases) entered hong kong on 18 march 2020, just before implementation of the mandatory quarantine policy. to make things worse, social gathering still went on during that period when cluster infections related to some bars and pub areas were reported. it is understandable though for the government to announce the policies in advance to allow the people to be better prepared. however, in hong kong, many residents rushed back before the implementation to avoid the mandatory quarantine, thus increasing the risk of transmission in the community. to minimize the opportunity of infection, pre-implementation announcements should be made as close to the implementation date as possible. meanwhile, comprehensive support plans for those being quarantined and groundwork should simultaneously be in place. quarantines on inbound travelers appeared to be effective. according to a study in singapore, rapid identification and isolation, quarantine of close contacts, and active monitoring of other contacts were effective measures in controlling covid-19 [6] . nevertheless, it should be noted that quarantine should be combined with other public health measures to achieve the best result [7] . quarantine polices are important and overall well-being should be catered for too. during the sars epidemic, people felt isolated and hopeless, which resulted in a rise in the suicide rate [21, 22] . while controlling the spread of the epidemic, the mental well-being of the residents should also be taken care of [23] . fortunately, with the many social media devices, social connectedness and emotional closeness can still be maintained when practicing physical distancing. it is important to ensure those quarantined do not feel left out or forgotten. meanwhile, it appeared that screening for covid-19 at the airport might not be effective enough in catching a significant proportion of cases [24] . however, sample testing for all inbound travelers seemed to work well in preventing the cases from entering the hong kong community. since such a policy was in force together with the mandatory quarantine policy, its effect alone could not be evaluated. the suspension of non-emergent government services, closure of public facilities, and home office arrangement for civil servants at the end of january coincided with the drop in the number of covid-19 infections at the end of january. moreover, resumption of these services and work at the office in early march seemed to correlate with an increase in the infection. subsequently, the suspension of these services and home office arrangement were implemented again at the end of march. the implementation of other policies included the suspension of education and schools. however, as these policies were implemented concurrently, an evaluation on the individual effectiveness of each policy was not possible. indeed, a review suggested that the effect of school closure was less than that of other social distancing interventions [25] . this could be true in view of an example in taiwan where schools and offices were not closed, yet the infection could still be maintained at a low level. it has also been reported that highly effective contact tracing and case isolation were sufficient to control a new outbreak of covid-19 [3] . in this regard, hong kong has been performing contact tracing exceptionally well, nonetheless, its effect also could not be assessed in the current study. the strength of this study was the estimation of the infection curve based on the back-projection method. the limitation of this study was that the date of onset was subject to recall bias, and a proxy date of onset was assumed on 46 asymptomatic patients. a sensitivity analysis was conducted by excluding the asymptomatic cases, and the trajectory of the infection curve remained roughly the same. an assumption made on the incubation period might also affect the estimated infection curve. nevertheless, this study utilized the pooled estimate from a meta-analysis based on eight studies [15] . this study was a narrative study, and causality cannot be assessed. in addition, if there were more than one policy or event occurring in parallel, it would be difficult to distinguish their impacts. at the same period, there were also social events such as healthcare on strike, protests for various reasons, and panic purchase of food and toilet paper, which involved the gathering of people and reduced social distancing, yet this study did not analyze their impact. future studies might consider using the estimated infection curve to assess the effectiveness of various preventive measures and events using the quantitative approach. to conclude, the infection curve of covid-19 could be constructed by the back-projection method. the findings of this study were consistent with previous studies on the effectiveness of some preventive measures. this study suggests that social gatherings and policy announcements and implementation sometimes coincide with changes in the infection curve; however, prospective studies designed to evaluate causality are needed to further understand this observation. rolling updates on coronavirus disease (covid-19) impact assessment of non-pharmaceutical interventions against coronavirus disease 2019 and influenza in hong kong: an observational study feasibility of controlling covid-19 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social and religious challenges backcalculating the incidence of infection with covid-19 on the diamond princess incubation period of covid-19: a rapid systematic review and meta-analysis of observational research a method of non-parametric back-projection and its application to aids data reconstructing the incidence of human immunodeficiency virus (hiv) in hong kong by using data from hiv positive tests and diagnoses of acquired immune deficiency syndrome monitoring the severe acute respiratory syndrome epidemic and assessing effectiveness of interventions in hong kong special administrative region global surveillance for covid-19 caused by human infection with covid-19 virus (interim guidance) python 3 reference manual; createspace the impact of epidemic outbreak a revisit on older adults suicides and severe acute respiratory syndrome (sars) epidemic in hong kong physical distancing and emotional closeness amidst covid-19 ncov working effectiveness of airport screening at detecting travellers infected with novel coronavirus (2019-ncov) school closure and management practices during coronavirus outbreaks including covid-19: a rapid systematic review key: cord-000617-8m7spnxj authors: kim, jean h.; lo, fung kuk; cheuk, ka kin; kwong, ming sum; goggins, william b.; cai, yan shan; lee, shui shan; griffiths, sian title: knowledge of avian influenza (h5n1) among poultry workers, hong kong, china date: 2011-12-17 journal: emerg infect dis doi: 10.3201/eid1712.110321 sha: doc_id: 617 cord_uid: 8m7spnxj in 2009, a cross-sectional survey of 360 poultry workers in hong kong, china, showed that workers had inadequate levels of avian influenza (h5n1) risk knowledge, preventive behavior, and outbreak preparedness. the main barriers to preventive practices were low perceived benefits and interference with work. poultry workers require occupation-specific health promotion. in 2009, a cross-sectional survey of 360 poultry workers in hong kong, china, showed that workers had inadequate levels of avian infl uenza (h5n1) risk knowledge, preventive behavior, and outbreak preparedness. the main barriers to preventive practices were low perceived benefi ts and interference with work. poultry workers require occupationspecifi c health promotion. i n 1997, a zoonosis in humans caused by a highly lethal strain of avian infl uenza virus (h5n1) was reported in hong kong. live-poultry markets were the source of this outbreak (1) . as one of the world's most densely populated regions (16,000 persons/mile 2 [>6,300 persons/km 2 ]) (2), hong kong is a city at high risk for a large-scale outbreak of avian infl uenza caused by live poultry in large-volume wholesale markets and within neighborhood wet markets (open food stall markets). because members of the average household in hong kong shop in wet markets on a habitual basis, these markets are located in the most densely populated areas ( figure) and are commonly multistory complexes or in basement levels of shopping centers. because poultry workers are a potential bridge population (3, 4) , the government has instigated voluntary avian infl uenza training since 2001 that reviews regulations for workplace disinfection, waste disposal, poultry storage, and personal hygiene measures (5,6). despite occupational risk for exposure to avian infl uenza (7, 8) , there have been few studies of poultry workers (8) (9) (10) (11) (12) . most studies were conducted in rural settings in developing countries (9) (10) (11) (12) , but fi ndings cannot be readily extrapolated to cities such as hong kong because of differences in food-handling practices and occupational settings. knowledge, perceptions, and work practices of live-poultry workers in hong kong have not been examined. therefore, a survey of these workers is timely and warranted, given confi rmed persistence of avian infl uenza in asia. (13) the study an anonymous, cross-sectional survey was conducted during june-november 2009. interviewers approached 132 licensed live-poultry retail businesses in wet markets and 23 wholesale establishments. the fi nal sample was 360 poultry workers (194 retailers and 166 wholesalers; response rate 68.1%). respondents were asked about their demographics, past month's work and preventive behavior, and avian infl uenza-related knowledge on the basis of a world health organization factsheet (14) . we asked perception questions based on the health belief model and the likelihood of adopting certain behavior patterns in the event of a local bird-to-bird or bird-to-human outbreak of avian infl uenza. summative scores were computed for avian infl uenzarelated knowledge, current preventive behavior patterns, outbreak preparedness, and various perception domains. higher scores refl ected more benefi cial levels of each domain. unconditional multilevel regression indicated no evidence of clustering effect by poultry market. standard multivariable linear regression was conducted by using sas version 9.1.3 (sas institute, cary, nc, usa) with knowledge, practice, and preparedness scores as outcomes and potential predictors showing p<0.25 in unadjusted analyses as input variables. distribution of standardized residuals and their association with predicted values were examined to assess model assumptions. most (208, 60.1%) respondents were men 35-54 years of age, of whom 192 (55.3%) had worked a mean of 16.1 years in the poultry industry. respondents showed low mean summative scores for knowledge of avian infl uenza (online appendix incorrectly believed that a human vaccine for avian infl uenza was available. most (208, 89.9%) respondents were familiar with infl uenza-like symptoms of avian infl uenza virus (h5n1) infection such as fever, but fewer workers were aware of respiratory and gastrointestinal symptoms of virus infection. the internet and other sources (e.g., health talks) of information about avian infl uenza were strong independent predictors of greater knowledge. however, training did not result in higher knowledge levels. poultry workers reported low-to-moderate levels of compliance with hand hygiene and other preventive measures (ranging from 7.3% [36] using eye protection to 65.2% [245] using handwashing with soap after slaughtering poultry). working in the poultry industry ≥10 years, lower perceived barriers to preventive behavior, and retail poultry work were independent predictors of higher preventive behavior scores. with regard to avian infl uenza-related perceptions, lack of training (277, 83.4%) and the view that compliance with all infection regulations is diffi cult during peak hours (218, 64.9%) were the most frequently cited barriers to adoption of preventive behavior. a total of 154 (46.4%) workers believed that face masks reduced business, and 153 (46.1%) believed that vaccination was expensive. low anxiety about illness was reported by 242 (76.6%) respondents. in the event of a local outbreak, workers expressed various levels of acceptance for precautionary actions, ranging from 15.8% (56) for reducing work hours to 82.4% (290) for seeking medical care for infl uenza-like symptoms. ninety-six (27.4%) respondents anticipated taking oseltamivir. greater perceived benefi t of preventive behavior was the strongest independent predictor of higher preparedness scores (online appendix table 2 , wwwnc.cdc. gov/eid/article/17/12/11-0321-ta2.htm). similar to other regions (8) (9) (10) (11) , poultry workers in hong kong showed low risk perceptions for avian infl uenza, inadequate knowledge, and a wide range of compliance with preventive measures. because training (6) was not associated with overall preventive behavior or preparedness, there may be an unmet need for occupationspecifi c health information. higher levels of knowledge demonstrated by workers who accessed health information sources (e.g., internet) that provide detailed information suggest that comprehensive, occupation-relevant information should be more widely accessible. however, occupational practices of animal workers might not be amenable to change solely on the basis of improvements in knowledge. only 129 (42.1%) respondents reported that poultry workers could realistically adhere to all government guidelines (6) . interference with work, high cost, and reduction of business were repeatedly cited as impediments to the adoption of preventive behavior. even in the event of local outbreaks of avian infl uenza, most workers were not amenable to actions having adverse economic effects such as reducing work hours. animal workers are thereby unlikely to widely adopt preventive behavior if these measures confl ict with their economic interests. despite the ongoing government regulations regarding avian infl uenza in hong kong (6), a complete ban on live poultry is unrealistic because of the culturally entrenched demand for fresh poultry. increasing knowledge and risk perceptions while simultaneously reducing occupational barriers to preventive behavior thereby continues to be the cornerstone of effective zoonotic infection control among animal workers. implications of these fi ndings extend to other poultryborne pathogens, such as campylobacter spp. and emerging infectious diseases • www.cdc.gov/eid • vol. 17, no. 12, december 2011 salmonella spp., which share common preventive measures. close adherence to workplace measures will likely reduce outbreak risk for other poultry-borne diseases. therefore, a framework for greater integration of risk management strategies and worker education of these poultry-borne infections tailored to the local context is worthwhile and cost-effective. in the spirit of the one health commission, which calls for an integrated, interdisciplinary approach to human-veterinary-environmental health challenges (15), the fi ght against global pandemics, such as those of avian infl uenza virus (h5n1), necessitates greater dialogue and collaborative leadership between governments and livestock industries. development of realistic occupational safety measures is an ongoing challenge for national governments. confi rmed human cases of avian infl uenza a (h5n1) census and statistics department, the government of the hong kong special administrative region. key statistics of the 2006 population census. hong kong: the government wet markets: a continuing source of severe acute respiratory syndrome and infl uenza? risk of infl uenza a (h5n1) infection among poultry workers, hong kong, 1997-1998 training for prevention of avian infl uenza risk for infection with highly pathogenic infl uenza a virus (h5n1) in chickens case-control study of risk factors for avian infl uenza a (h5n1) disease, hong kong knowledge, attitudes, and practices of avian infl uenza, poultry workers poultry-handling practices during avian infl uenza outbreak attitudes, and practices regarding avian infl uenza (h5n1) avian infl uenza risk perception among poultry workers environmental sampling for avian infl uenza virus a (h5n1) in livebird markets avian infl uenza ("bird fl u"): fact sheet one health commission we thank the poultry workers for participating in the study and terry wong for assisting with preliminary data collection. key: cord-016551-5vwgg8e6 authors: anis, mohab; altaher, ghada; sarhan, wesam; elsemary, mona title: construction and building applications date: 2016-12-09 journal: nanovate doi: 10.1007/978-3-319-44863-3_2 sha: doc_id: 16551 cord_uid: 5vwgg8e6 the construction industry is a particularly attractive industry for nanotechnology applications. since it employs a diversity of building materials, nanomaterials can be employed to enhance the materials’ performances, durability, longevity and sustainability. the construction and building practice is detrimental to the environment in various aspects such as electricity consumption, landfill accumulation, unhealthy aesthetics and neighborhoods. this chapter shows how nanotechnology-based building materials are playing an important role in green architectural design and construction, which has become a growing trend in many countries. nanomaterials could be integrated with cement, concrete, or windows to conserve energy, minimize electricity bills and sanitize the surrounding atmosphere. nevertheless, the industry is still facing many hurdles towards the wide application of nanomaterials in a cost effective manner. construction and building are major contributors to the rising carbon emissions and the global climate change. in addition, the construction industry is a rapidly growing industry. the nature of the construction industry involves the application and use of a diversity of building materials. this leads to nanotechnology being rapidly adopted by the construction market in several aspects like coatings, insulation materials, and building materials (steel, cement, asphalt, glass, polymers, etc.). nanomaterials are currently employed in cements, steel, and even windows to render buildings greener, more cost effective and safer. green construction has become the dominant trend in the construction industry, which means that buildings should meet certain specifications in the materials used, the processes employed, and in the behavior of the residents. these specifications aim at reducing co 2 emissions and reducing the negative impact of the construction industry on the environment. green architectural design and construction has shifted dramatically since the evolution of nanotechnology. many people are now seeking healthy lifestyles and environmentally friendly neighborhoods. green building is currently experiencing a growing demand by governments, architects, and people, especially after many cities have adopted strict regulations regarding green construction. globally buildings consume around one third of the worldwide electricity [1] , with cement alone contributing to the global co 2 emissions by around 5 % [2]. one way nanotechnology is used in construction is the concept of nanoreinforcements which involves reinforcing the body by adding dispersions that are in the nano-size scale. for example, nanoreinforcements in steel have rendered steel stronger and lighter. nanoreinforcements in cement have rendered it more durable and cost effective. another application of nanotechnology in the market involves making ultra violet (uv) absorbing, self-cleaning, and depolluting coatings for windows. moreover, nanotechnology has been rapidly adopted in air and water purification systems. the next generation of nanotechnology applications in construction has begun to involve building integrated photovoltaics (bipv), which are solar cells that can be integrated within buildings in smart designs without affecting the buildings' aesthetics, as well as being a clean source of energy and electricity. even electronics and sensors are being developed to be integrated with buildings. smart curtains or windows are expected to change the way people are experiencing the way they live (imagine walls that change colors with just a click!) [1] . it is important to note that there are still a lot of barriers to the adoption of nanotechnology in building, however, there are certain drivers and enablers that if emphasized and executed will overcome such barriers. nano-enhanced materials are more expensive than conventional materials. they yield high performances using small amounts of the materials. thus, it is expected that with the continuous r&d (research and development) efforts to improve nanomaterials' performances at lower costs, the construction market will continue to increasingly adopt the nanomaterials. proper education of the construction industry about the potential benefits associated with nanotechnology is the starting point towards the rapid adoption of nanotechnology in building materials. although nano-based construction materials are not economically competitive compared to conventional materials, continuous efforts are undertaken to render them cost effective. in addition, strict regulations have proved to be an important surge to the adoption of nanotech in green construction. one significant example is the us leed (leadership in energy and environmental development) which has developed strict minimum standards to simultaneously force and encourage builders to conserve energy and reduce carbon emissions. hong kong fights germs in subways. a japanese antimicrobial nanocoating that had long lasting efficiency offered maximum protection and elevated hygiene levels in hong kong subway stations. • owing to their nanosize, antimicrobial nanoparticles offered the potential to maximize public protection against germs in the highly populated hong kong subway stations. • nano silver-titanium dioxide coating (nstdc): a coating containing tiny particles of silver and titanium that are very active in killing microbes. • the nano-formula has been successfully applied by mtr (mass transit railway) in hong kong subways, and has been continuously monitored to expand its application in other facilities inside and outside hong kong. sars outbreak. in the spring of 2003, a large outbreak of severe acute respiratory syndrome (sars) occurred in hong kong and other asian countries. the contagion rapidly spread throughout the world. its rapid transmission and high mortality rate made sars a global threat for which no efficient therapy was available and proactive empirical strategies had to be developed to treat the patients and protect healthy individuals. high risk zones. around 2.5 million commuters use hong kong railway and subway stations daily, and they are highly susceptible to dangerous microbes adhering on floors, handrails and buttons. more cost and lower sustainability. regular disinfection of railway stations uses harsh cleansers, which are expensive and some of which are not environmentally friendly. public misconception. the us national institute for occupational safety and health (niosh) has classified tio 2 as a "potential occupational carcinogen", which produces a public misconception regarding its safety-workers need to wear protective clothes while spraying nstdc, but once dried it is completely safe. silver resistance. there are recent investigations that are addressing issues related to microbes that can develop resistance against silver nanoparticles, which can compromise its long term effectiveness. no international standardized testing. lack of standardized tests to assess the long term potential environmental impact of nanoparticles (because there are different formulations of different compositions using different synthetic techniques). efficiency on a broad spectrum. nstdc is certified to be effective in killing a wide range of bacteria, viruses, and mold including the h1n1 influenza virus. huge investment. mtr corporation attempted to invest 1.5 million dollars in nanotechnology products to enhance the hygiene levels of hong kong stations, especially that nanoparticles maximize effectiveness. regulated materials. nstdc's main component, titanium dioxide (tio 2 ), has been approved for use in foods by the fda and under the public health and municipal services ordinance in hong kong. promising results. preliminary tests on hong kong subway cars coated by nstdc showed 60 % reduced bacterial infections. durability. the nstdc nano formula is stable and does not require frequent replacement; therefore it is sprayed every 3 years and is checked regularly every 8 months. wider adoption. nstdc, promising antimicrobial efficiency, makes it suitable to be applied in mtr-managed shopping malls, staff offices and recreational facilities to ensure the highest cleanliness standards for passengers, customers and staff. what's next? mtr plans to monitor the coatings in hong kong in attempts to apply them in its two new uk rail franchises-london rail and west midlands. palais royale: india's first green super-tall residential building. hydrophobic concrete plays an important role in the rapidly growing building industry in india. • concrete is porous and by time, it absorbs water causing it to corrode and crack. hycrete admixtures (chemical mixtures added to concrete) are hydrophobic nanostructured mixtures that create a waterproofing seal on the concrete's internal capillaries preventing water penetration. similarly, they protect steel reinforcement bars by creating protective coatings around them. nanotechnology • nanostructured cement in liquid admixtures: when the concrete hardens, the admixture turns from liquid to a solid bonded to concrete. • "palais royale" is the first skyscraper to achieve the platinum leed certificate from the indian green building council. rapidly emerging market. the construction boom and the damp environment in india make it an ideal customer for hycrete. it is worth mentioning that in 2008 alone, around 30 projects made use of hycrete. cost of corrosion. the us spends 276 billion dollars annually on corrosion related problems and the federal republic of germany spends 4 % of its gross national product on corrosion [1] . leed motif. builders and architects all over the world seek to earn leed credentials. india has become an advanced entrant in the leed race. environmental impact. external protective coatings on concrete are usually petroleum based and thus compromise the ability to recycle concrete. in addition, they release vocs (volatile organic compounds) into the surrounding environment. still needs to be greener. hycrete technology does not play too impactful of a role in reducing carbon emissions associated with making concrete. very slow adoption rate. the construction market is somewhat conservative and diffuse, especially in india: high quality construction is not yet fully appreciated on a large scale. risky investment. the construction market in developed countries is well established. consequently, developing countries are the main target. however, the concepts of green nanotechnology innovations are not easily implemented or understood in most developing countries. uncertain feature. some studies on hycrete suggested that its compressive strength is reduced by 10-20 % yet is still suitable for most construction applications [3]. india is getting rich. the construction boom in india was mainly triggered by the rapid growth in the middle-income class as well as the increasing wealth of the country. high level testing. hycrete went through over 10 years of independent and sponsored tests, mostly funded by us federal highway administration. all of these tests showed promising results. according to the british standard absorption test bsi 1881-122, hycrete had less than 1 % water absorption [4] . gold certificate. hycrete is the first material certified by cradle-to-cradle gold certification because it is easy to recycle and it adds leed points to projects. cost and time saving. the admixture is built within the concrete that is batched at the plant not at the job site. thus it saves costs of extra containers and materials compared to the case of applying external coatings at the job site. business boom. the palais royale project greatly boosted the hycrete business. the project required 100,000 gal of hycrete and the company gained more than one million dollars. cost efficiency. the installation process of hycrete in the "palais royale" project was fast and cost effective because the amount of hycrete needed per square feet was 40 % less than the amount needed for the external waterproofing membrane solutions. operational impact. implementation of nanostructured admixtures in hycrete decreases the amount dosed in concrete (1 gal per cubic yard of concrete) reducing the time, cost, and waste of operations [4] . internal impact. the application of hycrete is expected to enhance the longevity and durability of the skyscraper's infrastructure. what's next? the underdeveloped construction market in india along with hycrete's success in indian projects is driving private equity firms to joint venture with hycrete, inc. hycrete's achievement in india is setting it as a role model for the emerging construction markets in the middle east. bioni paints dubai discovery gardens. a 40,000 square meter residential community in dubai "discovery gardens" decided to use the antimicrobial bioni paints. bioni using nanotechnology, managed to stabilize and integrate silver nanoparticles in paints. it used the smallest possible microbicidal amount to prevent yellowish discoloration of paint. silver nanoparticles bound to paint: tiny particles of silver that are very active in killing microbes. the residential community is built with an antimicrobial durable nanocoating that is resistant to cleansing chemicals and is nonflammable [1] . greener long lasting alternative. traditional antimicrobial coatings containing biocides have short life spans and slowly diffuse into the environment posing human and environmental risks. metropolitan growth. in dubai, there is a continuously growing construction activity with buildings of truly immense proportions, which makes it a valuable customer for bioni antimicrobial paints. desert kingdom. although dubai employs high quality construction work, the hot climate and high humidity create an ideal medium for the growth and propagation of mold and microbes inside buildings. sbs. the sbs (sick building syndrome) is strongly related to contaminants and pollutants released from indoor sources [1] . aesthetics and efficiency. the difficulty of maintaining a high enough concentration of nanosilver to efficiently exert an antimicrobial effect yet low enough to prevent yellowish discoloration. high cost. although bioni antimicrobial paints in hospitals are 25 % more cost effective because they decreased the frequent use of biocides, they are more expensive in residential buildings. superbugs. even though tests have shown that bioni antimicrobial paints killed more than 99 % of staphylococcus aureus on the paint surface, still there were no appropriate field tests carried out to test activity against superbugs (microbes resistant to multiple antibiotics). applied materials research in bremen) and in bioni cs have spent more than 10 years developing processes for manufacturing the antibacterial nanosilver particles and for incorporating them successfully into paint solutions. broad microbicidal effect. bioni antimicrobial paints are volatile organic compounds, free of antiallergic, antiviral and antibacterial effects. nanosafety. the nanotechnology innovation in the paint ensures nanosafety by trapping the nanoparticles in a polymeric matrix, thus there is no fear of release into the surroundings. furthermore, the coating is certified by tüv rheinland signet ensuring that it is emission free and does not release any substances into the environment. dubai municipality testing. the national building authority of dubai-the dubai municipality-conducted its tests on bioni products yielding promising results. maintain building integrity. the innovative paints proved to be the best fit with building materials because they are resistant to abrasion (wet abrasion resistance class 2) and disinfection chemicals. additionally, they are not flammable (building material class a2). extra cost efficiency. according to dubai municipality testing, bioni's nanosilver technology has low thermal conductivity and can reflect up to 93 % of the incident light, thus lowering air conditioning bills. growing market in dubai. on july 13th 2009, bioni was officially recorded in the emirate's commercial register marking an excellent opportunity for bioni to expand its activities in the gulf region. what's next? although bioni antimicrobial paints were designed to target medical facilities, bioni they can find applications in other sensitive buildings such as children's bedrooms, schools, kindergartens, bathrooms, showers and toilets, the food industry, and retirement homes for the elderly. société générale bank in switzerland utilized 3 m nano-based uv absorbing window films to solve the problems of its overheated indoor working environment. hundreds of ultra-thin layers made of advanced nanoceramics that can reduce heat and ultraviolet light transfer were installed. at the same time, they preserve interior and exterior window views. nanotechnology nano-based advanced ceramics: they filter out 25−99 % of infrared (ir) and uv radiations, while maintaining the transfer of visible radiations [5] . the new windows reduced cooling costs, contributed to the environment, and maintained their healthy indoor environments. nowadays' impractical alternatives. conventional reflective films are either metal based, which interfere with electronic signals and corrode in coastal regions changing the window color, or dye-based, which fade over time. sustainability. energy costs are increasing, and there is a great need for sustainable energy efficient solutions especially from the building sector which is one of the main detrimental influences on the environment. first patency. 3 m is the first company to earn the world's first patency in window films over four decades ago. since then, the company has been producing reliable solutions to lower customers' energy costs and to provide an accelerated return on investment. year commercial warranty, encouraging its rapid commercialization and adoption. leed. 3 m window films are components of leed sustainable design where buildings can earn 2-11 points [6]. indoor environment. up to 99 % of total uv energy and more than 80 % of the heat producing ir energy were rejected. the bank had better and sustainable indoor temperature control. furthermore, fabrics and furnishings were protected against uv induced damage. cost effectiveness. société générale bank enjoyed a unique and green approach to reduce energy consumption with a valuable return on investment. mission accomplished. the bank managed to improve the indoor working environments without compromising the specific historic and aesthetic features of the old building. green impact. the building industry is a top contributor to worldwide carbon emissions. building insulations could save around 42 % of energy consumption and consequently reduce carbon emissions [1] . what's next? the growing regulations on the building sector to save energy drive the growth for solar control window films, which is forecast to be an 863 million dollars market by 2018. first technology providers like 3 m are likely to be market leaders, and early adopters in the construction market will enjoy a unique position [7] . cleaning using forces of nature. an innovative glass makes use of rain and sun to self-clean and resist dirt. • innovation pilkington developed nano-films made of a photocatalyst that can interact with ultraviolet (uv) rays to break down organic dirt. the innovative film also contains a hydrophilic (water loving) component that can attract water or rain on its surface forming sheets that dry without spotting. the technology used nano films (15−20 nm) made of microcrystalline titanium dioxide. titanium dioxide in the presence of uv produces radicals that degrade organic pollutants to nontoxic products. ever since pilkington introduced their self-cleaning glass windows, they have been experiencing accelerated adoptions of their windows and a growing customer base. environment friendliness. pilkington self-cleaning windows eliminate the need for noxious chemicals that are washed off into the environment after the cleaning process. consumer convenience. self-cleaning windows are forecasted to be more rapidly adopted in construction compared to other types of smart windows: consumers can rapidly see the cost efficiency associated with the decreased frequency of cleaning windows compared to that associated with energy savings in other types of smart windows. emerging market. the market for self-cleaning windows is not yet mature, with few players, thus, there is a great opportunity for growth and expansion for early entrants. regional limitation. the photocatalytic material used will not function properly in the presence of inorganic dirt, long spells, coastal areas and internal windows because it needs daylight. since self-cleaning technologies in windows are new features and no quality standards are there to assess their efficiency, a consumer's decision will be reliant only on the manufacturer's claims. high cost. pilkington self-cleaning windows are 15-20 % more expensive than conventional glass, which can negatively influence the buyer's purchasing decision. market upset. glass cleaning companies are an important component of the glass windows "value chain". thus, the introduction of self-cleaning windows will affect their businesses negatively. enablers r&d. pilkington's expertise through 5-7 years of extensive r&d on thin film technologies enabled it to successfully transform them from laboratory samples to the market. safe material. titanium dioxide is publicly and governmentally accepted because it has been widely used in food related materials, cosmetics, and toothpastes. attraction of unique customers. saint pancras station in the united kingdom is one of the customers that has applied the self-cleaning glass. it installed the glass on its roof and building structure to reduce maintenance costs. technology appreciation. pilkington was one of the four finalists for the royal academy of engineering's macrobert prize that rewards technological and engineering innovation. new added benefit. pilkington photocatalytic effect could naturally also depollute the surrounding air by decomposing some pollutants such as formaldehyde and ground level ozone. pilkington is working with other glass manufacturers, universities, and standards' institutes to develop standards that assess and measure the self-cleaning properties of nanocoatings in an attempt to increase the public trust (so as not to be only reliant on the manufacturer claims) and the commercial adoption of these products. moreover, self-cleaning glass can be integrated with solar panels to reduce their frequent cleaning costs, and to make use of the same solar radiations. lumotone invented new transparent shutter films that are stuck on window made opaque by the click of a button. lumotone inc. has designed a film that can be applied to a glass surface and can be converted to opaque color upon switching it off. it can also be tailored to be colored or be used to show a projection, switched on and off using a mobile device. the innovation is based on a film containing polymer dispersed liquid crystals (pdlc) i.e. small nanoparticles of liquid crystals dispersed in a polymer as shown in fig. 2. 1. how such liquid crystals work: in a typical pdlc, there are many crystals with different orientations and configurations that scatter light giving an opaque appearance. these crystals become aligned when an electric field is applied allowing the light to pass through and giving a transparent appearance. an efficient invisible window blind that can be turned on and off by the press of a button. the need for privacy. window blinds are important house amenities to prevent people from prying into other people's lives. new décor trends. the new futuristic décor trends constitute less furnishings, wide spaces and invisible blinds instead of curtains that can be controlled by the press of a button. the need to save energy. by controlling the amount of light entering the room, you can ensure the room stays cool in the summer and warm in the winter thereby reducing the energy needed to maintain a room's temperature. the need for automation. since the advent of remote controls, computers and mobile phones people have come to rely more and more on automation. this is further increased by the modern fast pace of life. numerous people nowadays install home automation systems to make their life more comfortable and easy. uv blockade. nanoshutters block 99 % of uv light entering through the glass. this in turn is healthier as well as crucial to preventing the fading of colors of the interior décor and fabrics of furnishings inside the house. installation. the difficulty of installation of the nanoshutter will definitely affect its success. however, lumotone, inc. has made the nanoshutters easy to install-as easy as putting up a poster on the wall. they also provide certified professionals who can install them for their customers. automation. how to make these smart windows automated and be controlled by your mobile device remotely when you are away from home. durability. the durability of the nanoshutter film and whether it can withstand cleaning by household solvents is a limitation. this explains why such films are protected by an upper layer to prevent them from being scratched or destroyed. in addition, the company provides directions as how to clean such smart windows; which solvents are allowed or not allowed. research. the founders of the company were originally researchers and engineers in the field of nanotechnology in the university of waterloo, canada, giving them credible backgrounds to design such products. nanoshutters that can be integrated with home automation systems. lumotone developed their nanoshutters to be compatible with any home automation system. mobile applications for the nanoshutters. lumotone has also designed mobile applications and computer software that enable the users to control their shutters in or away from their homes. auto-scheduled nanoshutters. lumotone has made its shutters to be schedulable by computer or mobile application so a user can sleep in shaded windows and wake up in bright sunlight early in the morning to go to work. the efficiency of nanoshutters made them invade other market sectors including automotive and aircrafts. these smart windows help to control the inside cabin temperature as well as prevent screen glare when watching videos. what's next? lumotone is further developing its technology to produce pixels and transparent electronic displays. nanotechnology for green building. green technology forum 2 environmentally intelligent integral waterproofing and corrosion protection for concrete. clean technology opportunities and challenges for solar control films key: cord-258307-nsdhvc8w authors: maki, dennis g. title: sars revisited: the challenge of controlling emerging infectious diseases at the local, regional, federal, and global levels date: 2011-10-20 journal: mayo clin proc doi: 10.4065/79.11.1359 sha: doc_id: 258307 cord_uid: nsdhvc8w nan i n 1992, a blue-ribbon panel was commissioned by the institute of medicine of the national academy of sciences to advise the us government on emerging infectious diseases that posed a threat or potential threat to the health of people living in the united states and assist in the federal allocation of public health resources. 1,2 emerging infections were defined as infections caused by newly identified human pathogens-such as the legionella bacillus, 3 the reemergence of previously controlled pathogens-such as measles, 4 or the appearance of anti-infective resistancesuch as methicillin-resistant staphylococcus aureus, 5 the incidence of which had increased significantly within the past 2 decades or threatened to increase in the near future. since the outbreak of severe pneumonia in us veterans attending a convention at the bellevue-stratford hotel in 1976, found 6 months later to have been caused by a previously unknown and remarkably ubiquitous waterborne bacterium, legionella pneumophila, 3 more than 3 dozen human pathogens have been identified as agents of emerging infectious diseases in the united states (table 1) . the most recent and perhaps most fearsome emerging infections are the appearance of west nile virus encephalitis in new york city in 1999 and its rapid spread westward 6 ; inhalation anthrax, deriving from use of bacillus anthracis spores as a biologic weapon against the us civilian population in 2001 7 ; the global outbreak of severe acute respiratory syndrome (sars) in 2003 8 ; and the looming threat of pandemic influenza, especially global disease caused by the highly virulent avian subtype a (h5n1). [9] [10] [11] during the past 16 months, mayo clinic proceedings has published reviews of diseases caused by 3 of these emerging pathogens, west nile virus, 12 the sars coronavirus (sars-cov), 13 and avian influenza virus. 14 efforts to better inform readers about the consequences of emerging infectious diseases continue in this issue of the proceedings, in which chiang et al 15 report a study of 14 cases of nosocomial sars acquired in 3 taipei hospitals during 2003. most of the 14 patients, 13 of whom were followed up for at least 8 months, were health care workers, and because few had underlying diseases, all except 1 survived; thus, this study provides some of the best data on the long-term effects of sars on the lung. the clinical features and natural history of sars encountered by chiang et al are similar to those reported in much larger cohorts. 16, 17 all their patients had fever, and most had cough and dyspnea as well; however, 79% had diarrhea, and 64% had myalgias, indicative of the severe systemic immunoinflammatory response to this unique new human infection. 18, 19 similarly, all their patients had lymphopenia, and most had elevated levels of lactate dehydrogenase, now well-defined surrogate laboratory markers for patients presenting with sars. 16, 17 however, chiang et al also found that patients with a very high c-reactive protein or lactate dehydrogenase level at the outset were far more likely to have progression to a severe stage of disease requiring mechanical ventilatory support, information of value to clinicians who might be called on to manage patients with sars in the not-too-distant future. most interestingly, chiang et al show that whereas bilateral fibrotic changes were demonstrable by high-resolution computed tomographic imaging 6 to 8 months after the acute infection, most of the survivors showed near-normal spirometric lung volumes (forced vital capacity, forced expiratory volume in 1 second), albeit one third with reduced diffusion capacity, but none required home oxygen. it is likely that most of these individuals will have recovery of normal lung function. these findings are very similar to the well-documented long-term pulmonary effects of garden-variety acute respiratory distress syndrome, stemming from overwhelming pneumonia, gastric aspiration, near drowning, trauma, pancreatitis, or systemic sepsis, in which most survivors have gratifying recovery of lung function in the early years after the acute episode. [20] [21] [22] because sars is such a unique human viral infection and induces such an unusually severe systemic inflammatory response, 18, 19 it will be important to closely follow survivors of severe sars for considerably longer to be certain that latently expressed progressive pulmonary fibrosis does not occur. between the first reports from the world health organization and the centers for disease control and prevention (cdc) that defined sars as a global threat in march 2003 23,24 and control of the epidemic in southeast asia and north america 5 months later, more than 8000 persons in the republic of china, hong kong, singapore, vietnam, taiwan, and canada became infected, and 774 (9.6%) died of the infection 8 ; mortality exceeded 50% in patients older than 60 years. 16, 17 since the last communication on sars in the proceedings in april 2004, there have been extraordinary advances in our understanding of the disease in terms of its pathogenesis, epidemiology, management, and control: editorial • like many of the emerging human pathogens such as borrelia burgdorferi (mice, deer), us hantavirus (mice), west nile virus (wild birds), variant creutzfeldt-jakob prions (cattle, potentially free-ranging cervids), monkeypox virus (exotic african rodents and primates, us prairie dogs), and avian influenza virus a (h5n1) (edible birds), infection by sars-cov can legitimately be considered a zoonosis, and wild mammals formed the initial reservoir of the virus-sars-cov has been isolated from palm-top civets and raccoon dogs in the live animal markets in southern china, 25 and purveyors of these animals commonly show asymptomatic sars-cov seropositivity. 25, 26 the genomic evidence that sars-cov is an animal-human recombinant is compelling, [27] [28] [29] [30] and sars-cov appears to have had a biologic origin remarkably similar to the human influenza a viruses and human immunodeficiency virus. although the sars virus originated in animals and made the leap to humans, once established in the human population, the virus has spread rapidly person-toperson, and the major reservoir of human disease is humans in the early stage of infection, before they have been diagnosed as having the virus and placed in respiratory and barrier isolation. 31 • elegant molecular epidemiology has traced the origins of sars-cov to foshan in guangdong province, southern china, from whence it spread to beijing, then to hong kong, and from hong kong to vietnam, singapore, and canada. 32,33 a 65-year-old chinese physician who traveled to hong kong on march 21, 2003 , where he spent only 1 day, appears to have been the source of sars-cov that ultimately resulted in thousands of cases of sars in 26 countries and 5 continents. 34 • sars-cov is a new human pathogen to most of the world. studies by the cdc have shown no serologic evidence of past infection in more than 400 specimens from us residents collected long before the sars epidemic. 35 • as a new human pathogen, there is, understandably, little if any natural immunity. virtually all persons who became infected by sars-cov became symptomatic, 31 and studies of exposed health care workers show that less than 1% to 2% of those infected experience mild or subclinical infection. 36 • sars spreads almost exclusively person-to-person by respiratory droplets, rarely by the airborne route 31 ; the roles of contact or fecal-oral transmission are less clear but probably occur. 16, 37 the puzzling large outbreak in amoy gardens in hong kong was recently traced to virus-laden aerosols generated from sewage, using sophisticated airflow-dynamic studies and computational fluid-zone modeling. 38 however, whereas the outbreak in the amoy gardens complex represents distant airborne spread, distant spread is probably rare, as evidenced by the very low risk of infection in patients with no plausible face-to-face exposure to a patient with symptomatic sars, by the effectiveness of simple isolation measures in hospitals that did not have sophisticated negative-pressure air-controlled rooms with separate roofline exhaust, and by the relatively few secondary cases on commercial airliners. 31, [39] [40] [41] in an investigation of 3 flights in which an airliner transported 1 or more symptomatic infected passengers, 16 laboratory-confirmed cases of secondary sars were detected on 1 flight, with the greatest risk to other passengers close to the index case (seated within 3 rows, relative risk 3.1); on 1 flight carrying 4 symptomatic infected persons, possible transmission occurred to only 1 other passenger, and no secondary illness was documented on another flight that carried 1 person with early sars. 39 • simple control measures, most importantly the use of a high-quality filtration mask, ideally an n-95-type mask but even a surgical mask, 42 combined with full-barrier precautions in a single room were highly effective in preventing spread to other patients and health care workers where it was most carefully studied, in hong kong, singapore, and canada. 16, 17, 31, 42 • patients with early sars do not pose a risk to others until they become symptomatic and start to cough, 31 but there is considerable variability in contagiousness, probably based on the quantity of virus in the respiratory secretions 43 and the degree of coughing. very close proximity to an infected patient who is coughing heavily poses the greatest risk. 16 it appears that most spread of the virus can be linked to "super spreaders," and most infected persons are probably not very contagious. 31, 34, [44] [45] [46] [47] understandably, the risk of acquisition of sars-cov is far higher in the hospital than in the community. 31, 46 • the mean incubation period of sars is approximately 6 days 48 (range, 2-10 days) and is considerably longer than that for most other human respiratory viral infections, such as the common cold or influenza a, which permits case-contact investigations and quarantine of exposed contacts before those destined to become infected and contagious can spread the disease to others. • because so few persons develop clinical sars more than 10 days after exposure, there is no need to extend quarantine of exposed persons beyond 10 days. 31 • fever is so ubiquitous in sars that monitoring the body temperature of quarantined contacts and health care workers caring for patients with sars is a sensitive and specific method for detection of early infection, especially for health care workers before they become symptomatic and contagious. 49 all health care workers caring for patients with suspected or proven sars should be monitored 3 to 4 times daily; fever constitutes grounds for quarantine and diagnostic studies. 50,51 for personal use. mass reproduce only with permission from mayo clinic proceedings. • to control sars, early diagnosis is essential. clinical predictors for sars, based on study of large cohorts of patients in hong kong, 52 suggest that fever, myalgia, malaise, an abnormal chest radiograph, lymphopenia, thrombocytopenia, and, most importantly, previous contact with a patient with sars are each associated with a greatly increased likelihood of sars. in contrast, in a newly symptomatic patient older than 65 years or younger than 18 years without a plausible face-to-face exposure who has a cough productive of sputum, abdominal pain, sore throat, rhinorrhea, or leukocytosis, sars is unlikely. • modern-day virology has shifted rapidly during the past decade, from tissue cultures and serologic techniques to detection of the viral genome in clinical specimens by nucleic acid amplification techniques, such as polymerase chain reaction (pcr) or, for rna viruses, reverse transcriptase-pcr (rt-pcr). 53 highly sensitive and specific rt-pcr assays were developed in most of the countries afflicted by sars, most notably in hong kong, singapore, and canada, and were invaluable in early confirmation of sars-cov infection. the sensitivity of second-generation assays has been as high as 80% in the first 3 days of illness. [54] [55] [56] [57] whereas a pcr assay developed at the cdc was given immediate investigational device exemption approval by the food and drug administration, no commercial pcr assay has yet been licensed for clinical use in the united states. if sars returns and spreads in the united states, it will be essential that reliable real-time pcr assays are available in us hospitals. public health laboratories are not clinical service laboratories and are unlikely to be able to meet the need if sars reappears on a major scale. private companies should be given access to clinical strains of sars-cov and, if available, clinical specimens from infected patients in order to test and validate commercial assays that hopefully will be as accurate as, perhaps more accurate than, the current cdc assay. • ribavirin was used empirically in many patients with sars in southeast asia with the impression that it was effective therapeutically; however, in vitro studies have shown that sars-cov is not susceptible to ribavirin at concentrations achievable clinically. 58 hence, it is unlikely that the drug is active therapeutically. uncontrolled trials suggest that interferon alfa may be of benefit. 59, 60 there are a number of compounds and antiviral drugs with in vitro activity against sars-cov, including interferon alfa, interferon beta, and glycyrrhizin (licorice-root extract). theoretical rna virus targets, such as protease inhibitors and fusion inhibitors, also need to be assessed for efficacy. if sars returns on a major scale, it will be essential that the efficacy of antiviral drugs, such as commercial interferons, is tested in randomized, double-blind trials. • whereas uncontrolled studies of treated cohorts in asia have suggested that using moderate doses of corticosteroids, 1 to 2 mg/kg of a prednisone-equivalent daily, at the first evidence of severe sars, specifically hypoxemia, may improve survival, 59,61,62 corticosteroid therapy for sars has had serious adverse effects, 63 and a single randomized trial of preemptive pulse corticosteroid therapy did not show benefit. 64 if sars returns, it will also be essential that efforts are made to determine the efficacy of corticosteroids in a large prospective, randomized, doubleblind trial. • advancing age (>50 years) and coexisting illnessespecially diabetes or heart failure-greatly increase the likelihood of severe sars (requiring mechanical ventilatory support) and the risk of death. 16, 17, 43 inexplicably, sars is usually very mild in children, 65 who do not appear to be very contagious. 31 also, maternal-fetal transmission does not appear to occur. 66 • while coronaviruses are more resistant than most other respiratory viruses, 67 sars-cov appears to be susceptible to the commercial microbicides used for surface decontamination in hospitals. 31 • most importantly, outbreaks in hong kong, singapore, vietnam, canada, and elsewhere in the world were successfully controlled, but only by an intensive, coordinated effort in which the national public health authorities worked very closely with the regional public health agencies and, especially, hospital infection control officers and clinicians caring for patients with sars. [68] [69] [70] [71] the measures needed for control of sars are clear 31, 50, 51 : (1) earliest detection of cases, having at-risk individuals isolated and queried about their face-to-face contacts during the 10 to 14 days before the onset of illness; (2) expeditious contact tracing, with uncompromising home quarantine for all contacts of suspect and proven cases; and (3) stringent isolation of symptomatic suspect and proven cases, focusing most heavily on techniques to prevent droplet and airborne spread (eg, single negative-pressure rooms, ideally with separate roofline exhaust or filtration of outlet air; fit-tested high-filtration mask respirators and a face shield or goggles or a powered air-purifying system for all health care workers and others entering the room of the case, as well as the use of nonsterile gloves and gowns to prevent contact transmission). 50,51 the value of border screening and temperature monitoring of travelers is questionable. 71 the resources needed to control an outbreak in a city or a country are huge. in north america, the toronto outbreak consisted of 246 documented cases in 4 hospitals. 70 to control sars in toronto required home quarantine of more than 23,000 contacts and an informational hotline that handled more than 300,000 calls; the economic cost of the epidemic to the city and the city and provincial governments was estimated at $1.13 billion (canadian). the longterm psychological impact of sars on patients, families, and health care workers was also very substantial. [72] [73] [74] • efforts are now under way to test candidate sars vaccines. 75 the national tragedy of september 11, 2001, was followed by the most serious instance of bioterrorism involving the us civilian population in history, the spread of anthrax through the us mail. 7 these events coincided with growing awareness that weaponized smallpox virus almost certainly yet exists in the world, with strong suspicion that the former soviet union, 76 as well as countries that have sponsored international terrorism, such as iran and north korea, 77,78 retained smallpox virus as a potential weapon. the unthinkable has become plausible: weaponized smallpox virus in the hands of international terrorist groups. as a consequence, the federal government has undertaken major steps to greatly improve emergency preparedness at all levels, especially the capacity to respond to the use of biologic agents such as smallpox or anthrax as weapons against the civilian population as well as our military (table 2) . 79,80 billions of dollars have been appropriated to improve the capacity of public health and clinical laboratories to reliably detect infectious agents that might represent biologic weapons; to improve the likelihood that emergency department physicians and all primary care providers could recognize anthrax, smallpox, and other infectious diseases that might denote bioterrorism; to establish and coordinate surveillance programs at the regional, state, and federal levels; and to train more than a million public protection personnel and greatly improve preparedness of the 7000 us hospitals. 81 at my center, we have spent hundreds of person-hours identifying and retrofitting a 35bed patient-care unit for the potential accommodation of patients with smallpox or other highly contagious infections such as sars or pandemic influenza caused by a new strain. this local effort has focused on air control and negative-pressure isolation rooms, which have the capacity for supporting mechanical ventilation, and developing comprehensive guidelines for health care workers who would staff the unit. for the first time in our generation, there has been a major injection of federal dollars into the public health sector at the state, regional, and municipal levels. 81 the challenge will be to provide sustained support, rather than a limited bolus of supplemental funding. hopefully all this effort will never be needed to control smallpox-or an even more terrifying engineered pathogen 76, 82 -that might be used as a biologic weapon. if it is not, the effort will not have been wasted because it is likely that all the planning and resource allocation will prove invaluable for controlling the spread of natural emerging pathogens, such as sars-cov or a new strain of influenza virus, which are probably far more likely to pose a serious threat to human and animal health in the united states and worldwide. the greatest and most immediate threat is the longoverdue reappearance of pandemic influenza a. the leading and most dreaded candidate for the new pandemic subtype is avian influenza a (h5n1), recently reviewed in this journal, 14 which was first recognized in a large poultry outbreak in the live-animal markets of hong kong in 1997, where the virus had acquired the capacity to spread from infected birds to humans and killed 6 of 18 infected persons. 83 to control the outbreak, authorities killed nearly 2 million chickens to eliminate the reservoir of infection. since that time there have been contained outbreaks of different subtypes of avian influenza-h9n2, h7n2, and h7n7-that have caused disease in poultry, with secondary infections reported among pigs and humans, but infrequent and mild human disease, such as conjunctivitis or mild influenza-like illness. 14 there was only 1 human death among 89 cases in a large h7n7 outbreak in the netherlands in 2003. 84 in january 2003, a highly pathogenic strain of avian influenza a (h5n1) was identified in south korea and spread rapidly over the succeeding months to 7 other asian countries, cambodia, china and hong kong, indonesia, japan, laos, thailand, and vietnam. [9] [10] [11] to date, there have been 43 confirmed cases in humans, nearly all in children or young adults; 31 (72%) have proved fatal. 11 more than 100 million edible birds have been slaughtered by governmental authorities. all species of domestic birds appear to be susceptible to the h5n1 strain, which is probably transmissible to all species of wild birds, some of which migrate transcontinentally. the epidemic a (h5n1) strain appears to be gaining virulence 85 and was recently shown to have acquired the capacity of infecting mammalian species, domestic cats and wild felines within zoos 86 and pigs. most alarmingly, there is growing evidence that person-to-person spread can occur, 87 albeit yet rarely. the epidemic strain further shows high-level resistance to amantadine and rimantadine but is thus far susceptible to neuraminidase inhibitors, such as oseltamivir or zanamivir. 14 if the strain acquires recombinant genes that facilitate human infection and person-to-person transmission, pandemic disease could prove more catastrophic than the great h1n1 influenza epidemic of 1918. even more concerning has been the challenge of developing an avian influenza vaccine. current influenza vaccines are unlikely to provide any protection against the new h5n1 avian strain. the standard method for manufacturing influenza vaccines, growing the vaccine strain in chicken embryos, does not work because the avian a (h5n1) strain is so virulent that it kills the embryo before there is sufficient virus to harvest. novel genetic techniques, under way in the united kingdom, 88 will be needed to alter the strain's phenotypic features so that it can be grown in sufficient quantities in fertilized eggs and an effective vaccine can be constructed. vaccine manufacturers are understandably reluctant to make the investment to develop and manufacture a new vaccine, particularly in large quantities, when there is uncertainty whether the avian strain will indeed spread and necessitate administration of hundreds of millions of doses. 89 similarly, the sole manufacturer of the only oral neuraminidase inhibitor likely to be effective against avian influenza (oseltamivir) has very limited production capacity, and less than 2 million doses are currently available in us pharmaceutical stocks; the director of the cdc has stated that it would be desirable to have at least 100 million doses available. 89 in summary, 22 cases of cutaneous or inhalation anthrax traced to domestic bioterrorism and the global sars outbreak represent ill winds that have blown considerable good. the greatly expanded us federal effort to improve national preparedness for bioterrorism has strengthened public health at every level, and whereas we are far from being able to consider the united states as fully prepared, we are better prepared than only 3 years ago. 90 the recent us epidemic of monkeypox, 91 traced to importation of infected exotic african rodents and the burgeoning domestic trade in us prairie dogs, could be considered a live tabletop exercise-with a relatively innocuous pathogen-for the recognition and containment of smallpox. similarly, the global sars emergence has proved the enormous power of modern-day molecular biology to identify and characterize new pathogens, to detect clinical infections far more rapidly than in the past, and to quickly unravel the epidemiology of new infectious diseases-the scientific foundation for strategic control. the sars outbreak was contained only by unprecedented international cooperation under the leadership of the world health organization 68 and successful coordination within the affected countries between national and regional public health agencies and health care providers. controlling the next influenza pandemic, especially if it is caused by a highly virulent subtype such as the current a (h5n1) avian influenza virus, will require even greater international collaboration and vertical coordination in public health within the involved countries. it will also require an unprecedented commitment by the industrialized countries of the world to meet the needs of afflicted developing countries with limited public health resources. we are all in this together: it is in every country's self-interest to work collaboratively toward a common goal-the prevention of communicable disease and improvement of health of every citizen of the world. methicillin-resistant staphylococcus aureus: interstate spread of nosocomial infections with emergence of gentamicin-methicillin resistant strains update: investigation of bioterrorism-related anthrax and adverse events from antimicrobial prophylaxis world health organization. summary of probable sars cases with onset of illness from 1 world health organization international avian influenza investigative team world health organization. cumulative number of confirmed human cases of avian influenza a (h5n1) since 28 west nile virus: epidemiology, clinical presentation, diagnosis, and prevention sars: epidemiology, clinical presentation, management, and infection control measures avian influenza: a new pandemic threat? eight-month prospective study of 14 patients with hospital-acquired severe acute respiratory syndrome clinical features and short-term outcomes of 144 patients with sars in the greater toronto area plasma inflammatory cytokines and chemokines in severe acute respiratory syndrome analysis of serum cytokines in patients with severe acute respiratory syndrome pulmonary function and health-related quality of life in a sample of long-term survivors of the acute respiratory distress syndrome canadian critical care trials group. one-year outcomes in survivors of the acute respiratory distress syndrome world health organization. severe acute respiratory syndrome (sars)-multi-country outbreak-update isolation and characterization of viruses related to the sars coronavirus from animals in southern china prevalence of igg antibody to sars-associated coronavirus in animal traders characterization of a novel coronavirus associated with severe acute respiratory syndrome the genome sequence of the sars-associated coronavirus mosaic evolution of the severe acute respiratory syndrome coronavirus phylogenomics and bioinformatics of sars-cov comparative full-length genome sequence analysis of 14 sars coronavirus isolates and common mutations associated with putative origins of infection coronavirus genomic-sequence variations and the epidemiology of the severe acute respiratory syndrome severe acute respiratory syndrome (sars) in singapore: clinical features of index patient and initial contacts sars working group. a novel coronavirus associated with severe acute respiratory syndrome prevalence of asymptomatic infection by severe acute respiratory syndrome coronavirus in exposed healthcare workers [abstract cluster of severe acute respiratory syndrome cases among protected health care workers-toronto evidence of airborne transmission of the severe acute respiratory syndrome virus low risk of transmission of severe acute respiratory syndrome on airplanes: the singapore experience assessment of in-flight transmission of sars-results of contact tracing expert sars group of hospital authority. effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (sars) clinical progression and viral load in a community outbreak of coronavirusassociated sars pneumonia: a prospective study transmission dynamics of the etiological agent of sars in hong kong: impact of public health interventions transmission dynamics and control of severe acute respiratory syndrome modeling the sars epidemic epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in hong kong nosocomial transmission of the severe acute respiratory syndrome (sars) [abstract abstract k-1313. 50. world health organization. severe acute respiratory syndrome (sars): who guidelines/recommendations/descriptions. available at: www.who.int/csr/sars/guidelines/en. accessibility verified hospital authority sars collaborative group. a clinical prediction rule for diagnosing severe acute respiratory syndrome in the emergency department molecular and diagnostic clinical virology in real time early diagnosis of sars coronavirus infection by real time rt-pcr detection of sars coronavirus in plasma by real-time rt-pcr detection of sars coronavirus in patients with suspected sars centers for disease control and prevention. severe acute respiratory syndrome (sars) and coronavirus testing--united states description and clinical treatment of an early outbreak of severe acute respiratory syndrome (sars) in guangzhou, pr china preliminary results on the potential therapeutic benefit of interferon alfacon-1 plus steroids in severe acute respiratory syndrome :11. abstract k-1315e development of a standard treatment protocol for severe acute respiratory syndrome high-dose pulse versus nonpulse corticosteroid regimens in severe acute respiratory syndrome fatal aspergillosis in a patient with sars who was treated with corticosteroids the use of corticosteroids in sars clinical presentations and outcome of severe acute respiratory syndrome in children sattar sa. microbicides and the environmental control of nosocomial viral infections world health organization. a multicentre collaboration to investigate the cause of severe acute respiratory syndrome the international response to the outbreak of sars in 2003 public health measures to control the spread of the severe acute respiratory syndrome during the outbreak in toronto world health organization working group on prevention of international and community transmission of sars. public health interventions and sars spread the immediate psychological and occupational impact of the 2003 sars outbreak in a teaching hospital post-traumatic stress disorder and quality of life in patients diagnosed with sars [abstract severe acute respiratory syndrome-related psychiatric and posttraumatic morbidities and coping responses in medical staff within a primary health care setting in singapore canadian researchers testing sars vaccine in china the chilling true story of the largest covert biological weapons program in the world, told from the inside by the man who ran it the looming threat of bioterrorism available at: www.bt.cdc.gov/planning/tprstrategy/index.asp. accessibility verified october 8, 2004. 81. public health security and bioterrorism preparedness and response act of expression of mouse interleukin-4 by a recombinant ectromelia virus suppresses cytolytic lymphocyte responses and overcomes genetic resistance to mousepox human influenza a h5n1 virus related to a highly pathogenic avian influenza virus transmission of h7n7 avian influenza a virus to human beings during a large outbreak in commercial poultry farms in the netherlands the evolution of h5n1 influenza viruses in ducks in southern china avian h5n1 influenza in cats. science [serial online thais suspect human spread of bird flu uk 'developing bird flu vaccine experts confront major obstacles in containing virulent bird flu hospital preparedness for severe acute respiratory syndrome in the united states: views from a national survey of infectious diseases consultants the detection of monkeypox in humans in the western hemisphere key: cord-022158-32pe8ou0 authors: yuan, chao title: empirical morphological model to evaluate urban wind permeability in high-density cities date: 2018-01-16 journal: urban wind environment doi: 10.1007/978-981-10-5451-8_2 sha: doc_id: 22158 cord_uid: 32pe8ou0 in this chapter, a high-resolution frontal area density (fad) map that evaluates urban permeability was produced using an empirical model, which takes into account the heterogeneous urban morphology and local wind availability. using the mm5/calmet model, the wind data of hong kong was simulated, the fad map of three urban zones were calculated: podium (0–15 m), building (15–60 m), and urban canopy (0–60 m). wind tunnel test data was used to correlate the fad understanding of the three zones with pedestrian-level wind environment. linear regression analysis indicated that a lower urban podium zone yielded the best correlation with the experimental data, and 200 × 200 m was the reasonable resolution for the fad map. this study further established that the simpler two-dimensional ground coverage ratio (gcr) that is readily available in the planning circle can be used to predict the area’s average pedestrian-level urban ventilation performance of the city. working with their in-house gis team using available data, the gcr will provide the planners a way to understand the urban ventilation of the city for decisions related to air paths, urban permeability, and site porosity. . stagnant air in urban areas has caused, among other issues, outdoor urban thermal comfort problems during the hot and humid summer months in hong kong. stagnant air has also worsened urban air pollution by restricting dispersion in street canyon with high building-height-to-street-width ratios. the hong kong environmental protection department (hk epd) has reported the frequent occurrence of high concentrations of pollutants, such as no 2 and respirable particles (rsp) in urban areas such as mong kok and causeway bay (yim et al. 2009 ). these areas also have some of the highest urban population densities in hong kong. the 2003 outbreak of the severe acute respiratory syndrome (sars) epidemic in hong kong had brought attention to how environmental factors (i.e., air ventilation and dispersion in buildings) played an important role in the transmission of sars and other viruses. since the outbreak, the planning community in hong kong started to pay more attention to the urban design process in order to optimize the benefits of the local wind environment for urban air ventilation. as a result, the hong kong government had commissioned a number of studies on this regard; the most important project among the government-commissioned studies is entitled "feasibility study for establishment of air ventilation assessment system" (ava), which began in 2003 (ng 2009 ). the primary purpose of this comprehensive chapter is to establish the protocol that assesses the effects of major planning and development projects on urban ventilation in hong kong (ng 2007) . the importance of wind environment on the heat, mass, and momentum exchange between urban canopy layer and boundary layer has been studied by urban climate researchers (arnfield 2003) . two modeling methods have been frequently applied to study wind environment of the city: wind tunnel tests and computational fluid dynamics (cfd) techniques. the united states environmental protection agency (us epa) conducted numerous urban-scale wind tunnel tests to understand the dispersion of particulate matters smaller than 10 µm in aerodynamic diameter (pm 10 ) (ranade et al. 1990 ). williams and wardlaw (1992) conducted a large-scale wind tunnel study to describe the pedestrian-level wind environment in the city of ottawa, canada, and identified areas of concern for planners. plate (1999) developed the boundary-layer wind tunnel studies to analyze urban atmospheric conditions, including wind forces on buildings, pedestrian comfort, and diffusion processes from point-sources of the city. kastner-klein et al. (2001) analyzed the interaction between wind turbulence and the effects induced by vehicles moving inside the urban canopy. wind velocity and turbulence scales throughout the street canyons of the city were analyzed using smoke visualization (perry et al. 2004) . in 2004, the us epa's office of research and development (epa-ord) conducted a city-scale wind tunnel study to analyze the airflow and pollutant dispersion in the manhattan area (perry et al. 2004 ). kubota et al. (2008) conducted wind tunnel tests and revealed the relationship between plan area fraction (λ p ) and the mean wind velocity ratio at the pedestrian level in residential neighborhoods of major japan cities. in hong kong, the wind/wave tunnel facility has conducted numerous tests at the city, district, and urban scale to understand the wind availability and flow characteristics of hong kong (hkpd 2008) . apart from wind tunnels, cfd model simulation can be applied at the initial urban planning stage in providing a "qualitative impression" of the wind environment. mochida et al. (1997) conducted a cfd study to analyze the mesoscale climate in the greater tokyo area. murakami et al. (1999) used cfd simulations to analyze the wind environment at the urban scale. kondo et al. (2006) used cfd simulations to analyze the diffusion of no x at the most polluted roadside areas around the ikegami-shinmachi crossroads in japan. letzel et al. (2008) conducted studies of urban turbulence characteristics using the urban version of the parallelized large eddy simulation (les) model (palm), which is superior to the conventional reynolds-averaged models (rans). using the earth simulator, ashie et al. (2009) conducted the largest urban cfd simulation of tokyo to understand the effects of building blocks on the thermal environment of tokyo. ashie et al. noted that the air temperatures around ginza and jr shimbashi are much higher than in the surrounding areas of hama park and sumida river. ashie et al. argued that the high air temperature can be attributed to the bulky buildings at ginza and jr shimbashi that obstruct the incoming sea breezes (ashie et al. 2009 ). yim et al. (2009) used cfd simulation to investigate the air pollution dispersion in a typical hong kong urban morphology. in general, using cfd for urban-scale investigation has been gaining momentum in the scientific circle. two important documents that provide guidelines for cfd usage have been published: architectural institute of japan (aij) guidebook (aij 2007; tominaga et al. 2008 ) and cost action c14 (frank 2006 ). while the application of wind tunnels and cfd model simulations to analyze the interaction between the urban area and the atmosphere has made important contribution to the understanding of urban air ventilation of the city, such applications are costly, and may not be able to keep up with the fast design process in the initial stages of the design and planning decision-making process. instead, the outlined and district-based information based on urban morphological data parametrically understood may be more useful for planners. this chapter employs the understandings of urban surface roughness to establish the relationship between heterogeneous urban morphologies and urban air ventilation environment. a new method with cross-section areas, which takes into account the site-specific wind information measured at 60 m height using the mm5/calmet model simulation, was used to calculate the frontal area density (λ f ). using the site-specific wind information, the new calculation method of λ f focuses on the effects of the built environment to the wind field, which provides a spatially averaged understanding of wind permeability at the urban scale. in addition, the new calculation method of λ f considers the unique urban morphology of the podiums and towers in hong kong (i.e., many tall and slender buildings stand on large podiums), which shows that taking the urban morphology of podiums into consideration is important. therefore, the podium layer is defined within the urban canopy layer as shown in fig. 2 .2. the spatial characteristics of the large podiums provide much larger drag force on airflow nearer to the ground than the upper layers, and thus can greatly affect the wind environment at the pedestrian level. this study first correlates the pedestrian-level wind environment with λ f calculated at the podium layer, and then establishes an understanding of surface roughness and urban morphology based on ground coverage ratio (gcr), a term familiar to urban planners, with λ f to simplify the practical application of the understanding for professional use. the roughness properties of urban areas affect surface drag, scales and intensity of turbulence, wind speed, and the wind profile in urban areas (landsberg 1981) . the total drag on a roughness surface includes both a pressure drag (τ tp ) on the roughness elements and a skin drag (τ ts ) on the underlying surface (shao and yang 2005) . in this study, only the pressure drag is considered, since skin drag is relatively small and is not a factor that can be controlled at the urban scale. oke (1987) provided the logarithmic wind profile in a thermally neutral atmosphere, which is a semiempirical relationship that acts as a function of two aerodynamic characteristics: roughness length (z 0 ) and the zero-plane displacement height (z d ). the reliable evaluation of such aerodynamic characteristics of urban areas is significant in depicting and predicting urban wind behaviors (grimmond and oke 1999) . currently, three methods can be used to estimate the surface roughness: davenport roughness classification (davenport et al. 2000) , morphologic, and micrometeorological methods (grimmond and oke 1999) . the davenport classification is a surface-type classification based on the assorted surface roughness values, using high-quality observations (davenport et al. 2000) , which covers a wide range of surface types. this method is not too helpful to describe urban permeability in highdensity cities, because most of the urban areas could only be described in class 8 "skimming: city centre (z 0 ≥ 2)". compared with the micrometeorological method, the morphometric method estimates the aerodynamic characteristics, such as z 0 and z d , using empirical equations (lettau 1969; macdonald et al. 1998; raupach 1992; bottema 1996; kutzbach 1961) . grimmond and oke (1999) validated the empirical models by kutzbach, lettau, raupach, bottema, and macdonald. while reasonable relationships between z 0 and frontal area index (λ f(θ) ) for low-and medium density forms have been found, there is a tendency of overestimation of z 0 for higher density cases (bottema 1996) . grimmond and oke (1999) calculated λ f(θ) in the context of the urban morphology of north america cities. ratti et al. (2002) calculated λ f(θ) of 36 wind directions in london, toulouse, berlin, and salt lake city. by incorporating a spatially continuous database on aerodynamic and morphometric characteristics, such as λ f(θ) , z 0, and z d , morphometric estimation methods can be helpful to urban planners and researchers in depicting the distribution of the roughness of the city. using bottema's model equation, gál and unger (2009) mapped z 0 and z d to detect the ventilation paths in szeged. wong et al. (2010) mapped λ f(θ) to detect the air paths in the kowloon peninsula of hong kong. the frontal area index λ f(θ) is a function of wind direction of θ , which is an important parameter of the wind environment. the λ f(θ) in a particular wind direction of θ is defined (raupach 1992 ) as where a f represents the front areas of buildings that face the wind direction of θ , a t represents the total lot area, l y represents the mean breadth of the roughness elements that face the wind direction of θ , z h represents the mean building height, and ρ el represents the density (number) of buildings per unit area. λ f(θ) has been used widely by researchers in plant canopy and urban canopy communities to help quantify drag force. frontal area density, λ f(z,θ) , represents the density of λ f(θ) at a height increment of "z" : where a(θ ) proj( z) represents the area of building surfaces that approaches a wind direction of θ for a specified height increment " z" and a t represents the total lot area of the study area. compared with λ f(θ) , which is an average value that describes the urban morphology of the entire urban canopy, λ f(z,θ) represents a density that describes the urban morphology in the interested height band. burian et al. (2002) conducted frontal area density calculations in a height increment of 1 m in phoenix city, and found that λ f(z,θ) is a function of land uses because the buildings in different land uses have different building morphologies. due to the morphological difference between the podium layer and building layer in hong kong, as shown in fig. 2 .2, the respective λ f(z,θ) of the layer is expected to be better than λ f(θ) in capturing and describing the complicated urban morphology in hong kong. using a high-resolution (1 × 1 m) three-dimensional building database with building height information and digital elevation model (dem), a self-developed program embedded as a vba script in the arcgis system was applied to calculate the frontal area density (λ f(z) ) at different height bands. λ f(z) accounts for the annual wind probability from 16 main directions: where λ f(z,θ) represents the frontal area density at a particular wind direction (θ ), and can be calculated with eq. 2.2. p θ represents annual wind probability at a particular direction (θ ). to identify the height of the podium and urban canopy layer in high-density urban areas of hong kong, a statistical study was conducted based on three-dimensional building database provided by the hong kong government. twenty-five urban areas have been sampled as shown in fig. 2. 3. mean and upper quartiles of the building and podium height at metropolitan and new town areas were calculated. according to the height distribution shown in fig. 2 .4, the urban canopy layer and podium layer at the metropolitan areas were identified as 60 and 15 m, respectively. in hong kong, the local topography and land-sea contrast impose significant influence on the wind direction in the immediate vicinity of the urban canopy layer, as shown in fig. 2 .5. therefore, to focus on the impact of building drag force on airflow, site-specific wind roses for annual non-typhoon winds at 60 m height in 16 directions were used to calculate the corresponding local values of λ f(z) . due to the complex topography of hong kong, the territory is divided into subareas, with various area-specific wind roses ( fig. 2.6 ). the data on site-specific wind roses were obtained from the fifth-generation ncar/psu mesoscale model (mm5) that incorporates the california meteorological (calmet) system (yim et al. 2007 ). mm5 is a limited-area, non-hydrostatic, and terrain-following mesoscale meteorological model. mm5 is designed to simulate mesoscale and regional-scale atmospheric circulation (dudhia 1993; yim et al. 2007 ). calmet is a diagnostic three-dimensional meteorological model that can interface with mm5 (scire et al. 2000) . the terrain in hong kong is complex; hence, the resolution used in mm5 simulations (typically down to 1 km) cannot accurately capture the influence of topology characteristics on wind environment. therefore, calmet, a prognostic meteorological model capable of higher resolutions (down to 100 m), was used. combining the data obtained from mm5 and the data obtained from an upper air sounding station, maintained by the hong kong observatory, in 2004, the calmet model adjusts the estimated meteorological fields for the kinematic effects of terrain, slope flows, and terrain blocking effects to reflect the impact of a fine-scale terrain on resultant wind fields at 100 m resolutions (yim et al. 2007) . in the calmet model simulation, the vertical coordinates were set with 10 levels: 10, 30, 60, 120, 230, 450, 800, 1250 10, 30, 60, 120, 230, 450, 800, , 1750 10, 30, 60, 120, 230, 450, 800, , and 2600 10, 30, 60, 120, 230, 450, 800, m (yim et al. 2007 ). in this chapter, λ f(z) was calculated in uniform grids. each grid represents a local roughness value. the calculating boundary (grid boundary) was so small that large commercial podiums and public transport stations can be larger than the grid cell and cross the grid boundaries, as shown in fig. 2.7 . values of λ f(z) for the cells at the middle of such large buildings may be underestimated. therefore, to estimate the local roughness of every grid when buildings cross grid cells, a new method of which the cross-section areas (red areas) were included in the frontal areas of the corresponding grid cell was proposed. compared with the map in polygon units (gál and unger 2009) , this new calculation with uniform grid allows an exploration of mapping with a better explanatory power. compared with the conventional calculation of λ f(z) , the nonexisting cross-section walls in the new calculation method could result in unrealistic surface roughness. however, such cross sections may be needed to avoid underestimation of the surface roughness at the high-density urban areas covered by large and closely packed buildings. thus, the correlations between the vr_ w,j and between the new method of λ f(z) with cross section and the traditional method of λ f(z) without cross section were compared. wind velocity ratios were obtained from wind tunnel tests for hong kong (hkpd 2008) . the values of vr_ w,j of 10 study areas in wind tunnel tests were used as shown in fig. 2 .8. in the wind tunnel tests, test points were uniformly distributed in each study area. vr_ w,j for each test point has been described by (hkpd 2008) : where p i represents the annual probability of winds approaching the study area from the wind direction (i), and vr_ 500,i,j represents the directional wind velocity ratio of the jth test point, the mean wind speed at 2 m above the ground with respect to the reference at 500 m (hkpd 2008). vr_ 500,i,j is defined as (hkpd 2008): where v_ p,i,j represents the mean wind speed of the jth test point at the pedestrian level (2 m above the ground) for wind direction (i), and v_ 500,i represents the mean wind speed of the jth test point at 500 m for wind direction (i). as emphasized in fig. 2 .9, if study areas in wind tunnel experiment were crossed by grids in the map, the average of λ f(z) for the study areas is calculated by where λ f i(z) represents the frontal area density in the ith grid, s i represents the area of the ith grid in the study area, and s t represents the area of the study. the λ f(z) in the podium layer (λ f(0-15 m) ) that corresponds to the four grid sizes (resolutions), namely 50, 100, 200, and 300 m, were calculated. the r 2 values in table 2 .1 illustrate that the new calculation method can be as accurately predict the wind velocity ratio as the traditional method without cross section. as expected, in accordance with values of the λ f(0-15 m) including the unreal flow-confronting areas were larger than the ones calculated by the traditional method, and their correlations with vr_ w,j were similar (fig. 2.10) . on the other hand, the λ f(0-15 m) values in the kowloon peninsula calculated by the two methods were compared. in high-density urban areas with large and closely packed buildings, the λ f(0-15 m) values calculated by the traditional method without cross section were less than 0.1; some of them were even close to 0. this is a serious underestimation to the surface roughness. highlighted in fig. 2.11 , the new method with cross section in this chapter efficiently alleviates these underestimations by including the cross sections. based on the regression analysis result, following understandings can be stated: the new calculation method with cross sections can correctly predict the wind velocity ratio. furthermore, compared with the traditional method of calculating frontal area density, the new method can alleviate the underestimation of mapping urban surface roughness in high-density cities with large and closely packed buildings. as shown in table 2 .1, the values of r 2 decrease along with the reduction of the grid sizes. choosing a larger grid size would have a positive effect on depicting the urban wind environment. however, r 2 should not be the only criterion for selecting one grid size over another. for mapping roughness, the explanatory power of the map should not be totally traded off for the sake of the correctness of λ f(z) . after weighing the considerations, the resolution of 200 × 200 m was adopted in mapping urban permeability in hong kong. the skimming flow regime is normally found at the top of compact high-rise building areas (letzel et al. 2008) . similarly, due to the signature urban morphology of hong kong (i.e., high-density and tall buildings), the airflow above the top of the urban canopy layer may not easily enter the deep street canyons to benefit the wind environment at the pedestrian level. thus, the wind velocity ratio at the pedestrian level mostly depends on the wind permeability of the podium layer. a statistical study was conducted to validate the above assumption by comparing the sensitivities of vr_ w,j to changes of λ f(z) calculated at different layers. the cross-comparison results are plotted in fig. 2.12a, b , which indicate that vr_ w,j has a higher correlation with λ f(z) at the podium layer (0-15 m). this illustrates that pedestrian-level wind speed depends on the urban morphology at the podium layer (0-15 m), rather than the building layer (15-60 m) or the whole canopy layer (0-60 m). this understanding is important to support the evidence-based urban planning and design in order to improve the pedestrian-level wind environment at high-density urban areas. compared with front area index, which was used to detect the air paths in hong kong (wong et al. 2010 ), λ f(0-15 m) has been proven to be a better morphological factor in depicting the wind environment at the pedestrian level. as shown in fig. 2 .13a, the map of the frontal area density (0-15 m) depicts the local wind permeability at the podium layer in the kowloon peninsula and hong kong island. the continuous belts of high surface roughness on the northern coastline of the hong kong island and both sides of the kowloon peninsula, referred to as the wall effect of the kowloon peninsula, are evident (yim et al. 2009 ), whereas the wind permeability is very low. the maps of the frontal area density (0-60 m and 15-60 m) are also presented, as shown in fig. 2. 13b, c. these two maps are important for describing the wind permeability at the urban canyon layer. the turbulent mixing at the urban canyon layer is essential to improve urban air ventilation, alleviate air pollution, and dissipate the anthropogenic heat. compared with λ f(z) , ground coverage ratio (gcr) is a two-dimensional parameter commonly used by urban planners. gcr is defined as where a t represents the site area, a b represents the built area, w represents the average building width, and n represents the number of buildings. a statistical study was conducted to convert the frontal area density analysis to a practical design and planning tool; this was accomplished by investigating the relationship between λ f(0-15 m) and gcr. local values of λ f(0-15 m) and the gcr of the 1004 test areas (200 × 200 m) in the kowloon peninsula and the hong kong island were calculated. figure 2 .14 shows a good linear relationship of both (r 2 = 0.77). however, it should be noted the presence of outlier values of local surface roughness of large podiums and industrial buildings. equation 2.8 indicates the relationship between gcr and λ f(z) , which depends on k, the ratio between the averaged building width (w) and podium layer height, i.e. 15 m. if the building width of urban areas is much larger than that of other areas with normal building morphology, the correlation between gcr and λ f(0-15 m) in such areas can be significantly different from other areas. four examples of such sites, points a-d, are shown in figs. 2.14 and 2.15. w (2.8) based on the above discussion, following understandings can be stated: (1) there is a good linear relationship between λ f(0-15 m) and gcr (r 2 = 0.77) in most of the test points. for planners, using gcr to predict the wind environment at the pedestrian level is reasonable. compared with other traditional maps (gál and unger 2009; wong et al. 2010) , the proposed gcr map is more applicable to urban designers and planners due to its accessibility to the planners in the planning process. (2) local values of some areas may deviate due to the extremely large building widths (large commercial podiums and industrial buildings). in this type of areas, the wind permeability cannot be predicted in gcr. however, the occurrence of this type of extreme examples is very small (approximately 2%). an urban-level wind environment of hong kong was mapped using gcr information in this section. kubota et al. (2008) and yoshie et al. (2008) conducted an earlier investigation on the relationship between gcr and the spatial average of wind veloccoupled with the classification, the effect of different gcrs on the wind permeability can be identified. as shown in fig. 2 .16, three classification values are assigned: "class 1", "class 2", and "class 3", which denote good, reasonable, and poor pedestrian wind performance, respectively. based on this classification, the map of wind performance at the podium layer in hong kong was generated as shown in fig. 2 .17. compared with the roughness map without classification, the map in this study is more intuitive; in addition, it allows urban planners to better modify building morphology in order to improve the urban air environment. such map can be the spatial reference for urban planners. after incorporating the respective site-specific wind roses, the areas with low wind permeability are depicted in fig. 2 .17. these areas block wind and worsen the wind environment at the pedestrian level of their leeward districts. potential air paths in the podium layer are also marked out in this map. the potential air paths would play an important role to improve the urban ventilation and environment quality by fig. 2.16 relationship between ground coverage ratio and spatial average of wind velocity ratios in mong kok and cities in japan (kubota et al. 2008; yoshie et al. 2008 , edited by authors). the number of the point pairs is 11 fig. 2.17 map of wind permeability at the podium layer. the wind permeability at the podium level is depicted in the map: class 1: gcr = 0-30%, class 2: gcr = 31-50%, and class 3: gcr > 50%. based on the respective annual prevailing wind direction, the areas with low wind permeability are pointed out. these areas could block the natural ventilation and worsen the leeward districts' wind environment at the pedestrian level. potential air paths in the podium layer are also marked out in this map (for interpretation of the references to color in the text, the reader is referred to the electronic version of this book) podium designs as in the hkpsg bringing fresh airflow into the urban areas for the purpose of dissipating air pollutant and mitigating urban heat island intensity. the chapter has highlighted a number of important points that should be considered by city planners. first, one of the most significant factors is urban morphology, especially the podium layer, and its implication to the urban air ventilation environment. according to chap. 11, sects. 9-13 of the hong kong planning standards and guidelines (hkpsg) (hkpd 2006), a number of urban forms deemed to be conducive to the urban air ventilation environment have been proposed: … it is critical to increase the permeability of the urban fabric at the street levels. compact integrated developments and podium structures with full or large ground coverage on extensive sites typically found in hong kong are particularly impeding air movement and should be avoided where practicable. the following measures should be applied at the street level for large development/redevelopment sites particularly in the existing urban areas: • providing setback parallel to the prevailing wind; • designating non-building areas for sub-division of large land parcels; • creating voids in facades facing wind direction; and/or this chapter shows that the qualitative understanding of the podium structure, as mentioned in the hkpsg, is valid. in hong kong, some areas of high podium coverage can be identified. these areas require the most significant design, planning intervention and improvement. for building block disposition, the chapter has emphasized that city planners need to factor in the prevailing wind understanding to street layout and building disposition design as shown in fig. 2 .20. this understanding is in line with the concerns of the so-called "wall buildings", wherein a line of tall buildings screen the waterfront from the inland areas, thereby blocking the incoming urban air ventilation from the sea. based on the gcr information readily available to planners working on their gis system, the chapter has shown that planners can easily generate an urban wind permeability map, thereby enhancing the possibility to identify problem areas and, more importantly, to emphasize on potential air paths. the map also enables the interconnectivity of open spaces for urban air ventilation, and allows planners to take urban breezeways into account and design in accordance with the recommendations of the hkpsg (hkpd 2006) , as shown in fig. 2 .21: for better urban air ventilation in a dense, hot-humid city, breezeways along major prevailing wind directions and air paths intersecting the breezeways should be provided in order to allow effective air movements into the urban area to remove heat, gases and particulates and to improve the micro-climate of urban environment. breezeways should be created in forms of major open ways, such as principal roads, interlinked open spaces, amenity areas, non-building areas, building setbacks and low-rise building corridors, through the high-density/high-rise urban form. they should be aligned primarily along the prevailing wind direction routes, and as far as possible, to also preserve and funnel other natural airflows including sea and land breezes and valley winds, to the developed area. the disposition of amenity areas, building setbacks and non-building areas should be linked, and widening of the minor roads connecting to major roads should be planned in such a way to form ventilation corridors/air paths to further enhance wind penetration into inner parts of urbanized areas. for effective air dispersal, breezeways and air paths should be perpendicular or at an angle to each other and extend over a sufficiently long distance for continuity. breezeway and air path design as in the hkpsg using the urban wind permeability map of the territory, city planners can initially estimate the possible urban air ventilation environment of the urban areas with the average velocity ratios. adjusting the pedestrian-level wind speeds and predicting the bioclimatic conditions of the city have become possible. overall, the chapter has demonstrated a practical and reliable way for city planners to quickly obtain district-level urban air ventilation information for their board-based design works at the early stages. conceptually, avoiding wrong decisions that may be difficult to rectify later is, therefore, possible. aij guidebook for practical applications of cfd to pedestrian wind environment around buildings two decades of urban climate research: a review of turbulence, exchanges of energy and water, and the urban heat island effects of sea breeze on thermal environment as a measure against tokyo's urban heat island roughness parameters over regular rough surfaces: experimental requirements and model validation morphological analyses using 3d building databases 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core districts. the government of the hong kong special administrative region institute for the environment (ienv) (2010) study of ventilation over hong kong a wind tunnel study of organised and turbulent air motions in urban street canyons numerical analysis of diffusion around a suspended expressway by a multi-scale cfd model wind tunnel tests on the relationship between building density and pedestrian-level wind velocity: development of guidelines for realizing acceptable wind environment in residential neighborhoods investigations of the modifications of wind profiles by artificially controlled surface roughness high resolution urban large-eddy simulation studies from street canyon to neighbourhood scale an improved method for the estimation of surface roughness of obstacle arrays cfd analysis of mesoscale climate in the greater tokyo area cfd analysis of wind climate from human scale to urban scale feasibility study for establishment of air ventilation assessment system (avas) policies and technical guidelines for urban planning of high-density cities-air ventilation assessment (ava) of hong kong wind tunnel simulation of flow and pollutant dispersal around the world trade centre site methods of investigating urban wind fields-physical models wind tunnel evaluation of pm10 samplers analysis of 3-d urban databases with respect to pollution dispersion for a number of european and american cities drag and drag partition on rough surfaces a user's guide for the calmet meteorological model (version 5) a scheme for drag partition over rough surfaces aij guidelines for practical applications of cfd to pedestrian wind environment around buildings determination of the pedestrian wind environment in the city of ottawa using wind tunnel and field measurements a simple method for designation of urban ventilation corridors and its application to urban heat island analysis developing a high-resolution wind map for a complex terrain with a coupled mm5/calmet system air ventilation impacts of the "wall effect" resulting from the alignment of high-rise buildings experimental study on air ventilation in a built-up area with closely-packed high-rise building key: cord-334612-lxqcvqca authors: rao, nirmala title: sars, preschool routines and children’s behaviour: observations from preschools in hong kong date: 2006 journal: int j early child doi: 10.1007/bf03168205 sha: doc_id: 334612 cord_uid: lxqcvqca all schools in hong kong were closed in april 2003 to prevent the spread of sars. this paper considers the influence of the sars epidemic on children’s routines and behaviour when preschools re-opened, after a six-week closure. observations were made in 20 kindergartens and principals of another 10 kindergartens completed questionnaires. the influence of sars was evident in all preschools, be it through teachers and students wearing masks, notices on hand washing or the provision of alcohol dispensers for hand disinfection. the outbreak impacted noticeably upon children’s routines and social exchanges. in all schools, physical contact among children and sharing of food were not allowed. children were also prohibited from talking to their peers when they had removed their masks. the sars outbreak provided us a “natural experiment” to consider the influence of epidemics on preschools. las manos o se instaló una gran cantidad de dispensadores con alcohol para desinfectarse las manos. el brote y las medidas de prevención, afectaron en forma perceptible la rutina y el intercambio social de los niños. en todas las escuelas, se prohibió el contacto físico entre los pequeños, los que tampoco podían compartir alimentos. además, a los niños no les estaba permitido hablar con sus pares si se habían quitado la máscara. el brote de sars nos proporcionó un "experimento natural" para analizar la influencia de las epidemias en los establecimientos preescolares. during the past 100 years, there have been five killer viruses, including the spanish flu (1918) , the asian flu (1957), the hong kong flu (1968), severe acute respiratory syndrome (sars) (2003) and the avian flu (2004) (dunne, 2005) . flu pandemics have led to the closure of schools as it is assumed that infectious diseases can be rapidly transmitted in school premises. previous research indicates that school closure reduces the incidence of viral respiratory diseases among children during an influenza outbreak (heymann, chodick, reichman, kokia & laufer, 2004) . it has been suggested that one of the reasons that hong kong flu (1968) was less deadly than the spanish and asian influenzas is that it peaked during the school holidays and children did not spread the virus in school. research also indicates that upper respiratory infections (uris) are much more common in preschool children in centre-based care than those who are looked after at home (nichd eccrn, 2005) . hence, medical research indicates that preschool closure prevents the spread of viral respiratory diseases and that children in centre-based care are more susceptible to uris. on the other hand, because of the nature of transmission mechanisms, there is an extremely small likelihood that viruses like hiv/aids will be spread in preschools. schools were closed in britain and the united states during the spanish flu (billings, 1997) . more recently, in 2003, schools were closed in canada, mainland china, singapore and hong kong to prevent the spread of sars. five schools were closed in ontario, canada (health canada, 2003) . on the other hand, there were mass school closures in asia. in singapore, all schools were closed on march 27 and re-opened in phases after april 14 (singapore government, 2003) , and in hong kong, schools were closed for at least 6 weeks and also re-opened in phases with secondary schools re-opening before primary schools. preschools in hong kong were officially closed between march 29 and may 18, 2003. appendix 1 provides the who report on the course of the sars outbreak in hong kong. there were a total of 1,755 sars cases in hong kong and 399 deaths occurred because of sars (government of hong kong, 2003) . it should be noted that there were many unknowns about the transmission of sars at the height of the outbreak. the high population density of hong kong puts her at risk for the rapid spread of infectious diseases. further, since hong kong is used as a gateway between mainland china and the rest of the world, control of the epidemic was a top priority for the hong kong government. in hong kong, preschool institutions are in the private sector. they include child-care centres which serve children from 6 weeks to 6 years and kindergartens which enrol children ranging in age from 2 years 8 months to 6 years. most kindergartens offer bi-sessional classes of around three hours each, while most child care centres offer whole-day programs. about 95% of children over 3 years of age in hong kong attend preschool programmes. the extent of coverage reflects both government policy and the value that chinese parents traditionally attach to early childhood education. the government determines, monitors, and enforces standards for preschools. adult-child ratios are currently about 1:10 in kindergartens and curriculum guidelines are issued by the government. the 1996 guide to preprimary curriculum advocates a child-centred approach and stresses all-round development (government of hong kong, 1996) . it espouses contemporary views on effective early teaching and learning, and provides suggestions for facilitating intellectual, communicative, personal, physical and aesthetic development. the hong kong government was concerned that some kindergartens went too far in presenting formal academic curricula, using inappropriate teaching methods for children below the age of six. hence, in 1999, a list of 'dos and don'ts' for kindergartens was published (government of hong kong, 1999) . the list of 'dos' includes having a curriculum that covers moral, cognitive, physical, social, and aesthetic aspects of development by organizing activities that promote all-round development; organizing various child-centred learning activities; using the mother tongue as the language of instruction, and respecting individual differences. good programs in any country achieve all these goals, but some are especially pertinent to hong kong idiosyncrasies. for example, chinese culture emphasizes moral development, and it is recommended that the curriculum attends to this perspective. as in other societies, pedagogical practices in hong kong preschools are influenced by cultural beliefs about early learning. in the past, the chinese teacher was characterised as a fountain of knowledge who force-fed peking ducks. however, children spend more time in play-based learning now than in the past and there has been a corresponding decrease in expository teaching. it appears that traditional chinese cultural beliefs about early learning have taken a back seat to what is considered as good educational practice. cultural beliefs about childhood and education also influence pedagogy. for example, kindergartens tend to have highly structured days. this is partly due to children's age, but also a reflection of chinese cultural beliefs about the early years being a time for training young children to be disciplined and behave properly (rao, mchale & pearson, 2003) . during visits to preschools when they re-opened after the mandatory closure, the author was struck by the marked changes in preschool routines. hence this study was undertaken to provide an objective documentation of these changes. the main objectives of the study were to (i) consider the influence of the sars epidemic on children's routines and behaviour when preschools reopened after a six-week closure; and (ii) consider principals' perspectives on the lessons that had been learned about promoting children's learning and managing preschools during an epidemic. a retrospective study was conducted. the sample, although not randomly selected, was representative of hong kong preschools in terms of location, sponsor, status, size, and tuition fees. surveys were completed by observers in 20 preschools (18 kindergartens and 2 child care centres), and principals in another 10 preschools completed questionnaires. survey completed by observers. items on the survey fell into 6 categories including: information about the preschool and children (21 questions); routines before the sars outbreak (4 questions); learning during school closure (2 questions); preparing the kindergarten for re-opening (2 questions); students return to kindergartens (18 questions); lessons from sars (4 questions); and demographic information about the observers. the 18 items on students' return to kindergartens included questions on daily routines (3 questions); health issues (2 questions); social interaction among children (6 questions); preschool management (3 questions); and school holidays (4 questions). the majority of questions required responses in a fixed choice format. examples of items are presented in the appendix. questionnaires were completed by principals of 10 kindergartens. these addressed similar categories as those in the survey given to the observers but reflected their different perspectives and access to information. the questions to principals included ones on: learning during school closure (18 questions); preparing the kindergarten for re-opening (5 questions); students return to kindergartens (25 questions); and lessons from sars (5 questions). we were particularly interested in gathering information from principals about learning during preschool closure. this is because schools in hong kong and mainland china took particular advantage of the information and communication technology available to ensure that learning could take place even though schools were closed. the questions on "learning during school closure" included those related to: decisions about when to close and re-open the school (4 questions); teaching and learning (5 questions); contacting students (2 questions); homework (3 questions); and computer-supported learning (4 questions). government guidelines and regulations for preschools issued between march and may 2003 were perused. the survey for observers and the questionnaire for principals were developed in english and the observers, all of whom were completely bi-lingual (english-chinese), completed the english version of the survey. the questionnaire for principals was translated into chinese and a back-translation procedure was used to ensure accuracy of the translation. principals completed chinese versions of the questionnaire. surveys of 20 preschools (18 kindergartens and 2 child-care centres) were conducted by 3 experienced lecturers, who were responsible for the practicum supervision of students in early childhood teacher education programmes. they were given training in the use of the survey, in which to record their observations and they consulted with the student-teacher they were supervising in completing the survey. surveys were conducted within a month of preschools' re-opening. questionnaires were distributed to principals in july and returned by late august. the aim of this study was to document the influence of the sars epidemic on children's routines and behaviour, and consider principals' perspectives on promoting children's learning and managing preschools during an epidemic. in the following section, information garnered from the survey is presented under the following headings: school closure; learning during school closure; school re-opening; changes in routines; change in curriculum/pedagogy; and changes in social interactions. principals' perspectives are presented in the last section. as noted earlier, preschools were officially closed between march 29 and may 18, 2003. however, 15 % of the preschools closed before that date. the majority of preschools re-opened on may 19, 2003. teachers in all schools contacted students at least once per week during school closure and 15% of teachers contacted children twice a week or more often. the mode of contact varied from telephone calls (4 preschools), circulars (4 preschools) and e-mail (3 preschools). in the preschools which were observed, a variety of assignments were distributed for home-based learning. these included worksheets (18 preschools); exercise books (12 schools); reading assignments (8 schools); suggested parent-child activities (5 schools); cd roms for demonstrated teaching (3 preschools); and suggested websites for home learning (8 preschools). according to the observers, many changes were apparent in the school environment when children returned to preschool. all schools had visual displays about hygiene and the preschool environment was much cleaner. disinfection kits were located in most rooms. further, in many schools, teachers wore aprons to hold alcohol spray and extra masks. observers reported that 85% of the preschools instituted a moderate change in routine. in keeping with government guidelines, children's temperature was measured when they came to preschools and they washed their hands several times a day. in 15% of the preschools, there was a drastic change in routines, including a shortening of the length of school day. free play was curtailed and snack time was cancelled in some schools. in schools where it was continued, children had to face the wall while eating their snack. physical education (p.e.) and music lessons were cancelled and group size decreased in all schools. a specific example of a change in routine comes from the requirements for children when they entered preschool. in several preschools, children stepped on the disinfection mat outside the main door of the preschool and had their temperature and hands checked. they then had to remove their shoes and wash their hands. in fact, in some schools children had to wash hands up to 5 times within a 3-hour period. during the sars outbreak, the education and manpower bureau of the hong kong government issued a curriculum for children ranging in age from 3-6 years. this included the following 7 independent lessons: learning about sars; personal hygiene (1); personal hygiene (2); concern and respect for a sars patient; sars symptoms, wearing masks and washing hands; learning to prevent sars. in all preschools, the curriculum was modified to include sars education. all preschools talked about protection from sars, proper washing of hands, not touching face, and not sharing food. there was a decrease in instructional time in all preschools. some preschools introduced new themes and did not address previously planned themes. activities and games to raise awareness about the prevention of sars and the importance of personal hygiene were included in some schools. observations indicated that some schools accelerated teaching in order to "finish" all themes. teachers typically did not initiate activities such as circletime or story-telling with the whole class. instead more activities were conducted with small groups of children and there was more small group teaching. the latter is considered more developmentally and pedagogically appropriate in the early years (bredekamp & copple, 1997) . the sars outbreak influenced interactions between the teacher and children and those among children. children and teachers could not see each others' facial expressions because of masks and both children and teachers experienced discomfort when talking while wearing masks. there was also a reduction in social interaction among peers. sharing of toys was prohibited. children were given individual toy packs in some schools and toys/equipment were sterilized every time they were used. it should be noted that physical contact among children was prohibited. this was a function of the government guidelines which specified that physical contact among children should be discouraged. observations revealed that in 30% of the preschools, desks were moved into rows and children had to face the wall during snack time. there were fewer opportunities to interact in large groups as group sizes were reduced. for example, there was less interactive teaching and opportunities for learning in groups. school activities were affected by sars. field trips were cancelled and outdoor play was suspended or restricted to small groups. observers brought back photographs from the preschools which they visited. all children were wearing masks, and children had individual "stationery" and "toy" kits as sharing was prohibited. in some preschools, teachers wore aprons with pockets which contained alcohol spray, tissues and gloves. as mentioned earlier the education and manpower bureau of the hong kong government developed a programme for preschool children on sars. this was disseminated to all preschools. reports indicate that about 20 per cent of parents refused to pay preschool fees during the school closure. this, coupled with the decrease in demand for preschool education in hong kong because of the falling birth rate, caused financial hardship to many kindergartens. the permanent secretary of education and manpower urged property owners to reduce rents for kindergartens and child care centres, and in an open letter to parents of preschool children, pleaded with them to pay the school fees. the letters to parents were sent out on april 30 and may 7, 2004. some principals felt that that the government's response to the sars outbreak was too slow. they believed that the decision about mandatory school closure came too late and some preschools had closed before that date. interactions among adults were affected and this possibly indirectly affected children. principals reported that there was more staff teambuilding and better communication between the school and parents. one principal reported that since many social activities were cancelled, preschool children had the opportunity to spend more time at home with their families. they also felt that children developed an awareness of news and community events. by september 2003, preschools appeared to revert to their previous routines. however, the government continued to issue circulars on preventing the resurgence of sars. the aim of this study was to objectively document changes in preschool routines as a result of the sars outbreak in hong kong. some of the changes are similar to those made in singapore when it was confronted with a potential epidemic. for example, the singapore government (2003) issued the following guidelines to keep kindergartens sars free: clean and disinfect kindergarten premises; educate children, teachers and parents on precautionary measures against sars; daily temperature screening procedures for all children; and children who had travelled to sars-infected areas had to stay away from kindergartens for 10 days after their return to singapore. others changes in routines in hong kong preschools are a reflection of their specific circumstances and broader chinese beliefs of learning. all schools were closed during the mandatory period while some closed even before this. the latter reflects the autonomy given to preschools. preschool education in hong kong is not part of the main compulsory education system although over 90 per cent of children ranging in age from 3 to 5 years are enrolled in some form of preschool education (wong & rao, 2004) . the government does, however, ensure and monitor standards of service and through a fee remission scheme, the government seeks to ensure that no child is deprived of early childhood education because of its financial reasons (rao, koong, kwong & wong, 2003) . preschools prepared a variety of assignments for children during school closure. eighteen out of 20 preschools which were observed distributed worksheets while others sent exercises and reading assignments home. some preschools burnt cds so children could watch their teacher's instruction. summer holidays were also curtailed so children could "make-up" for missed classes. the provision of assignments and the longer school year reflect the relatively high academic focus prevalent in kindergartens in hong kong and the emphasis placed on completing the syllabus prescribed by the preschool. there were fairly marked changes in children's routines. while all would agree that children's temperature should have been taken before they came to school and they should wash their hands soon after they get there, the drastic changes in some of the routines may be considered excessive. was it necessary for children to wash hands 5 times within 3 hours? did preschool teachers really need to wear aprons with carry alcohol spray, tissues and gloves? did children really need to face the wall while eating their snack? however, these behaviours must be considered in the light of the general context. at the time of the sars outbreak, there were many unknowns about the transmission of sars, and there was panic in the general population. hong kong's typically crowded streets were less so, and about 30% of the population was wearing surgical masks. a 14-year-old boy played a prank on the internet and indicated that the territory was going to be quarantined. this led to panic buying and supermarkets ran out of basic supplies. it is also important to re-iterate that hong kong is a very densely populated city and this can lead to fairly rapid transmission of viruses. all preschools modified their curriculum to include education about sars and the government should be credited for the speed at which it prepared curriculum guides and materials for preschools. however, the emphasis on early pre-academic skills evident in some preschools in hong kong is reflected in the fact that some preschools accelerated their teaching in order to finish their syllabus/themes. further all local schools delayed the summer holidays by at least two weeks to make up for the school closure. on the other hand, nearly all international schools in hong kong closed on schedule for the summer holidays. one of the most dramatic changes noticeable was the decrease in social interaction among children. children experienced discomfort when talking while wearing a mask and teachers and students could not read each others' facial expressions because of the masks. children's desks were moved into rows and they were not allowed to change seats during the day. group size was decreased and there was less interactive teaching. there was an increase in solitary play and children were not allowed to share toys and physical contact among children was prohibited. all the changes in social interaction reflected government guidelines. in conclusion, the hong kong government acted efficiently and effectively during the period of school closure. guidelines on the preschool environment were issued, and curriculum materials relevant to sars were available to schools before they re-opened. however, some principals felt that the decision to close schools was made too late. there were moderate to drastic changes in children's routines when preschools re-opened after the closure. sars led to modifications in school activities, and all extra-curricular activities such as school trips were cancelled. there was, not surprisingly, an increased awareness about sars and how to prevent it as a result of visual displays and curriculum changes. there was more small-group teaching and less social interaction among children. in hindsight, we can consider whether some of the changes which resulted in decreased social interaction among children were really necessary. however, it is clear that preschool educators were very resourceful and tried to ensure that the suspension of school did not mean the suspension of learning. …."sars was first carried out of southern china into hong kong, and then on to hanoi, toronto, and singapore in late february. some 16 visitors and guests to the ninth floor of a hong kong hotel became infected through contact, in ways that remain mysterious, with a symptomatic medical doctor from guangdong province, who stayed in the hotel's room 911. the index case for hong kong's first outbreak, in the prince of wales hospital, visited an acquaintance staying on the same floor during the critical days in february. additional clusters were also subsequently linked to the hotel. sars had not yet been identified as a dangerous new disease when the outbreak hit hong kong's hospitals. doctors and nurses, unaware of the need to isolate patients and protect themselves, became the first victims as they struggled to save lives. in a particularly unfortunate incident, the index patient at prince of wales, admitted on 4 march, was treated four times daily with a jet nebulizer, which probably aerosolized the virus and greatly increased opportunities for spread. in late march, hong kong suffered a major setback when a large cluster, eventually numbering more than 300, of almost simultaneous new cases was traced to a single building in the amoy gardens housing state. that event, which raised the possibility of an environmental source of infection or even airborne spread of the virus, was investigated by teams of local specialists. the outbreak was attributed to an "unlucky" convergence of environmental conditions that allowed the contamination of vertically-linked apartments. this conclusion, subsequently confirmed by additional studies, calmed fears that the sars virus might be airborne. from the day when the first cluster of cases was recognized, hong kong officials have provided open, honest, and abundant information about sars to both the public and the media. hong kong also benefited from the contribution of its outstanding scientists, epidemiologists, and clinicians, who were at the forefront of efforts to track down source cases in the various clusters, identify the causative agent, develop diagnostic tests, and work out treatment protocols. faced with the largest outbreak outside mainland china, hong kong also pioneered many of the control measures used to successfully contain smaller outbreaks elsewhere. it is gratifying that these measures have now brought hong kong to the point of victory over the virus, although continued vigilance remains vital. on 2 april, who advised the public to consider postponing all but essential travel to hong kong. that recommendation was removed more than 7 weeks later, on 23 may". source: world health organization (june 23, 2003) update 86 -hong kong removed from list of areas with local transmission http://www.who.int/csr/don/2003_06_23/en/ the influenza pandemic of 1918 developmentally appropriate practice in early childhood programs (rev guide to the pre-primary curriculum list of dos and don'ts for kindergartens. schools curriculum circular no. 4/99. government of hong kong, education department: government printer. government of hong kong learning from sars: renewal of public health in canada. government of canada: health canada (publication number: 1210) influence of school closure on the incidence of viral respiratory diseases among children and on health care utilization child care and common communicable illnesses enhancing preschool education in hong kong predictors of preschool process quality in a chinese context. early childhood research quarterly links between socialization goals and child-rearing practices in chinese and indian mothers preschool education thanks are expressed to ms. maggie koong for her help in all stages of the project and to dr. emma pearson. portions of this paper were presented at the omep world conference (2003), kusadasi, turkey and the meeting of the international society for the study of behavioral development (2004) in ghent, belgium. key: cord-017080-erbftqgh authors: lau, stephen s.y. title: physical environment of tall residential buildings: the case of hong kong date: 2010-12-12 journal: high-rise living in asian cities doi: 10.1007/978-90-481-9738-5_3 sha: doc_id: 17080 cord_uid: erbftqgh increasing urban populations, scarcity of urban land, depletion in resources and severe impact of urban development on sustainability are critical contemporary issues. such issues have vast implications on the desirability of compact, high-rise high-dense built forms. yet, the environmental quality and social acceptance of these forms remain barely studied. this chapter reviews some of the critical environmental implications posed by the closely packed high-rise building and high urban densities. to the physical form, urban morphology would also study social forms, which are expressed in the physical layout of a city, and conversely, how physical form produces or reproduces various social forms. urban morphology is at times considered as the study of urban fabric, as a means of discerning the underlying structure of the built landscape. this approach challenges the common perception of unplanned environments as chaotic or vaguely organic through an understanding of the structures and processes embedded in urbanization. it is widely accepted that there is a close relationship between shape, size, density and uses of a city and the sustainability of that city. however, this chapter is limited to the characteristics of a high-rise, high-density compact urban environment: hong kong and its environmental implications. it is said that urban intensification creates frequent walking trips and better accessibility to facilities (masnavi, 2000) . in a compact city the reduction in car ownership, vehicular trips and increase of pedestrian and transit use alleviate the environmental consequences associated with the automobile. compact city has many advantages such as conservation of countryside, reduced need to travel by car and thereby reduction in fuel and pollution, support for public transport, walking and cycling, better access to services, more efficient utility and infrastructure provisions, and revitalization and regeneration of urban areas (burton, 2000) . in contrast to compact city, dispersed cities suffer from inefficient transport management and long commuting trips, which lead to a high dependency on automobile high energy consumption and pollution (newman & kenworthy, 1992) . although high density combined with mixed use allows for high accessibility to a majority of users, the mixing and co-location of incompatible uses such as housing, community, recreational and public spaces near commercial, industrial and transport can have consequences on the physical quality of the living environment. greater intensification has implications on urban green space. even though a valuable contributor to urban quality, urban greenery provision is often reduced under pressure from other land use development. research claims that compact city suffers from a perceived lack of greenery, open spaces and parks which provision is seen to be better in low-density environment (masnavi, 2000) . however, urban sprawl results in unsustainable levels of resource use and inequitable lifestyles (williams, burton, & jenks, 2000) . in comparison with urban sprawl, the compact city is a dominant model for sustainability (jenks, 2000) . yet, evidence on the impact of higher and lower densities on sustainability, the impact of centralized decentralized city form on sustainability are lacking. review of some city forms indicates both advantages as well as disadvantages in sustainability. for example, forms that reduce travel and are fuel-efficient may be harmful to the environment and have social inequities. they may be locally beneficial but not city-wise beneficial (williams et al., 2000) . the effects of urban density on the total energy demand of a city are complex and at times conflicting (givoni, 1998) . compactness of land use patterns will bring benefits to energy distribution and transport system design, but crowded conditions may create congestion and undesirable local microclimate (hui, 2000) . the compact city challenges are mainly associated with environmental quality and social acceptability (williams et al., 2000) . a multiple intensive land use development in hong kong is formed by an intensification of land use through mixing residential and other uses at higher densities at selected urban locations, together with an efficient transport and pedestrian network (lau & coorey, 2007; lau, ghiridharan, & ganesan, 2003) . hong kong is one of the asian cities that have evolved as a compact urban form. situated at the south-eastern tip of china, hong kong is ideally positioned at the centre of rapidly developing east asia. with a total area of 1,103 km 2 , it covers hong kong island (80.41 km 2 ), the kowloon peninsula just opposite (46.93 km 2 ), and the more rural section of hong kong new territories and 262 outlying islands (976.38 km 2 ). the central part of both hong kong island and kowloon are hilly rising to a height of 3,050 m. only 21.8% of hong kong land is built up, concentrating on the triangular tip of kowloon and the coastal strip of northern hong kong island. the total population in hong kong is 6,864,346 with the median age rising from 30 in 1988 to 36 in 2006 (census and statistics department, 2006) . the median monthly household income is hk$15,000. a population growth rate of approximately 1 million is observed in every 10 years in the last decade and the population forecast for 2,030 is 9 million (fung, 2001) . although the total population density is 6,380 persons per km 2 , urban areas hold a staggering population density of over 55,000 persons per km 2 where certain districts rank among the most densely populated places in the world. the density of public housing reaches at least 2,500 residents per ha, which is twice the density of the most crowded residential areas in mainland china (xue, manuel, & chung, 2001) . high-density in a land limited country like hong kong is the norm. cities often respond to development pressure by setting targets for increased urban densities, and the establishment of high-rise cityscape and compact urban settings is unavoidable (hui, 2000) . a chronological classification of tall building types in hong kong can be observed. the typology includes the verandah type from the 1920s, the cantilevered living quarters type from the 1950-1960s, the rectangular mass type from the 1970s, and the podium type from the 1980s onwards. among the rectangular mass type and podium type buildings, several shapes of building forms are observed such as the rectangular, "y" shape, clusters and crucifix shapes. when observing the pattern of development at a district scale, two significant variations in development is observed, namely, the clusters of multiple intensive land use developments around the mass transit nodes and the linear multiple intensive land use development alongside main roads and streets in the older parts of hong kong. the cluster of a high-density multiple intensive land use (milu) 2 development is mainly observed along (under) the three main rail lines of mass transit railway, namely, the airport railway, urban lines and tseung kwan o lines. they are three-dimensional distribution of density and land uses integrated by three parallel (2007), and wikipedia (2008) commuting levels, namely, the mass transit rail (mtr), kowloon-canton railway, subways below ground, buses, taxis, light rail transit and tramways on ground and walkways above ground which are then vertically connected via ramps, stairways, elevators and escalators. such developments are built above or connected in close proximity to mass transit railway and other public transport modes. as seen in fig. 3 .1, when several milu nodes are developed in close proximity, an interdependency is formed among these developments where land use functions and services are shared, thus creating primary, secondary and tertiary interdependent zones (lau et al., 2003) . plot ratios, also known as floor area ratios, of up to 15 for commercial uses and up to 10 for residential uses have led to buildings of up to 80 storeys built above 3-4 level podiums. the podium levels incorporate the secondary supporting functions such as commercial, recreational, government, institutional and community (gic) land uses while the primary residential, office or hotels/serviced apartments are located above as seen in fig. 3 .2. four major types of milu developments can be discerned according to its mix of land use types: 1. the primary use being office and/or hotel/serviced apartments with supporting secondary commercial, gic and transport uses; 2. primary use being residential supported by secondary commercial, gic and transport uses; 3. primary use being both residential and office supported by secondary commercial, gic and transport uses; 4. primary uses being office, residential, hotel/serviced apartments and secondary commercial, gic and transport uses. lau and coorey (2007) these development clusters are defined as primary milu nodes (lau et al., 2003) . table 3 .1 illustrates some examples of the four types of primary milu developments that are commonly seen in hong kong. in hong kong where the buildable land resources are scarce due to hilly terrain and scarcity of usable land, tall buildings serve as an optimal option to maximise development potentials and best returns. reduction in travel time due to intensification of mixed land uses contributes to efficiency and economic viability of the city (wu, 2005) . the concept of home-work-play gives the residents efficiency, convenience and savings in time. tall buildings also provide a heuristic device to meet the housing demands for the increasing population. additionally, the mixed use nature of developments creates places that are active and lively for longer duration of time, providing safe neighbourhoods and additional time for use of urban spaces for its residents. rich, vibrant urban spaces are created within neighbourhoods. urban intensification and compactness also provides savings in infrastructure and services, and high penetration of infrastructure and services for all residents. for example, it results in an overall reduction in energy use and traffic fumes (wu, 2005) . high-rise building rather than urban sprawl reduces the use of woodlands and forest areas for development, saving valuable land resources for future use and recreation purposes. in hong kong such country parks and woodlands can be easily accessed. yet, there are some consequences associated with tall residential built forms arising from the very high population and extreme density. both social and environmental implications are prevalent in such conditions. this chapter is specifically focused on the environmental implications and various measures and solutions that may mitigate the environmental consequences of tall residential buildings taking hong kong as a case study. high-density living in hong kong is strongly linked with significant air, water and noise pollution. drastic environmental implications such as living in busy urban centres with high air and noise pollution, poor lighting and ventilation in individual housing units, urban heat island and wind tunnel effects are observed in hong kong's high-rise building developments. one of the problems related to mixed land use developments at very high intensities is the incompatibility of uses. this problem is particularly apparent in the old built-up areas because of a lack of comprehensive planning in the past (fung, 2001) . examples include those residential developments that face environmental nuisance due to its location adjacent to industrial areas. another example is where highways pass through residential areas, posing the threat of noise and air pollution. probably due to poor ventilation and lighting conditions, as high as 50% of all electricity used in hong kong is for lighting and space conditioning (wu, 2005) . air conditioning accounts for one-third of the total power consumption of hong kong each year and costs hk$10 billion (ching, 2005) . high space conditioning further aggravates the outdoor climate conditions creating a vicious cycle of environmental pollution such as urban heat island. table 3 .2 outlines the positive and negative effects of high density on city's energy demand as identified by hui (2000) . current air pollution levels in hong kong are high due to the high intensity of emissions from industry and traffic as well as a lack of proper environmental planning in the past. the number of motor vehicles is increasing due to population growth and demands. many areas in hong kong are topographically confined by hills and the air pollution dispersion in these areas is inhibited (hong kong use of solar energy -roof and exposed areas for collection of solar energy are limited planning department, 2006a). hong kong has been facing two air pollution issues: local street-level pollution caused by motor vehicles; and regional smog problem caused by motor vehicles, industry and power plants both in hong kong and in the pearl river delta. street level pollution is mainly caused by the large number of motor vehicles in highly dense urban areas. the emissions are trapped in between the very tall buildings along the streets. the tall stacks of building towers create urban walls that are barriers to wind circulation and vistas in the city. further, it causes wind tunnel effects and unsafe environments at street levels. walking at street levels in compact cities is no longer safe for the pedestrian. the high flow of vehicular traffic damages the quality of the street environment, with their high noise and air pollutants. therefore, whether within enclosed spaces or outside in the public areas and streets, the quality of the living environment is being damaged, affecting the overall quality of life. furthermore, since 2006, there has been an increasing concern on the "wall effect" caused by uniform high-rise developments, which adversely impact air circulation. a survey carried out by the environmental group, green sense revealed that 104 of 155 housing estates surveyed have a "wall-like" design (yueng, 2006) . the survey found the estates of tai kok tsui and tseung kwan o as the best examples of this kind of design. in may 2007, citing concern over developments in west kowloon, and near tai wai yuen long railway stations, some legislators called for a law to stop developers from constructing tall buildings which adversely affect air flow in densely populated areas, but the bid failed (wong, 2007) . more recently, in december 2008, a protest against "wall-effect" for a dozen of current and planned constructions was held at central government offices (ng, 2008) . these protesters were also concerned about the development plans for nam cheong and yueng long stations. tall buildings also pose threats to public safety and health in terms of easy spread of disease and viruses, fire risks and domestic accidents. adequate ventilation and building maintenance are therefore an important issue for high-rise buildings in order to avoid the spread of disease and accidents associated with dilapidated structures (wu, 2005) . study on residents' satisfactions and aspirations of high-rise living in hong kong shows that better view, less noise, better air quality are the major reasons for people to opt for high-rise living (lau, 2002) . the higher selling prices for apartments on higher floors are also attributed to better views, less noise and better environmental quality. this trend may seem to suggest that residents who choose living on higher floors are seeking an escape from the environmental problems since living on higher floors allows one to be further way from the city surface. but, opting for taller buildings alone may not be a solution to the problem. there exists a strong pressure from people to improve air quality and environment. the government has acknowledged this requirement and taken measures to improve the environment. for example, it has implemented vehicle emission and fuel standards, cleaner alternatives to diesel, emission inspection and enforcements such as controlling smoky vehicles, etc. and promoting vehicle maintenance and ecodriving. in his 2006-2007 policy address, the chief executive of hong kong has emphasized the importance of addressing these issues in order to secure sustainable development for future generations. he has outlined some of the measures, to reduce air pollution, we have formulated the pearl river delta (prd) regional air quality management plan. this plan, prepared in partnership with the guangdong provincial government, aims to achieve specific emissions reduction targets by 2010. we have now set up a 16-station air quality monitoring network in the prd. based on the data collected, the prd regional air quality index is released everyday on the internet to keep the public informed of the actual regional air quality. the data collected will also help us assess the effectiveness of our pollution reduction measures . . . in hong kong, we have imposed emission caps on power plants at castle peak, black point and lamma island. these emission caps will be progressively tightened to meet the 2010 emission reduction targets. (chief executive, 2006 . in 2006, particulates and nitrogen oxides levels on the street have dropped by 13 and 19% respectively since 1999. the number of smoky vehicles on the road has also reduced by about 80% (environmental protection department, 2006) . increased use of mass transport and reduction in private car and taxi could help to reduce the air pollution levels caused by vehicular traffic. in addition to policy measures, urban design measures are suggested for improving air ventilation (chinese university of hong kong, 2005; hong kong planning department, 2006b) . recent study identifies the following urban design issues as a means to a better quality and comfortable urban environment: lack of breezeways air paths; tall and bulky buildings closely packed causing undesirable wind breaks to urban fabric; uniform building heights resulting in wind skimming over the top of buildings and not being re-routed into the fabric; tight narrow streets not aligned with prevailing wind with tall buildings resulting in urban canyons; lack of urban permeability-with few open spaces, minimal gaps between buildings, excessive podium structures reducing air volumes at ground levels; large building blocks forming wind barriers; projections from buildings and obstructions on narrow streets and general lack of soft landscaping, shading and greenery as contributing to poor air ventilation and environmental quality in high-rise, compact built areas (chinese university of hong kong, 2005; hong kong planning department, 2006b) . for better urban air ventilation breezeways in the forms of roads, open spaces, and low-rise building corridors are suggested to allow air penetration to inner parts of urbanized areas. breezeways, roads, main streets and avenues should be aligned either parallel or 30 â�¢ to the prevailing wind directions. open spaces must be linked and aligned to form unobstructed wind corridors with low-rise structures alongside them. space between buildings must be maximized, especially in large sites with dense developments. the longer frontages of blocks may be aligned parallel to wind corridors, and non-built areas and setbacks may be introduced to further allow for good wind penetration. to maximise the penetration of sea breezes and land breeze water front sites may take special precautions to avoid blockages in wind paths (chinese university of hong kong, 2005) . street patterns, building heights, open spaces, density, and landscape will determine the air ventilation, solar radiation, day lighting and air temperature in compact high-rise built forms having implications on indoor and outdoor environmental quality. to illustrate, reference is made to the natural ventilation study conducted for a proposed luxury residential development in shenzhen, china. an assessment of air flow, solar energy and daylighting is done using computer based simulation tools such as airpak (usa), ecotect (uk) and radiance (usa) (lau & li, 2006) . table 3 .3 shows the airflow study and wind velocities within the compact high dense residential site. all three graphs in table 3 .3 show high age of air, indicating low ventilation and increased stagnated air. in the surrounding areas of the high-rise towers the age of air reduces when elevation height increases from 5 to 40 m, indicating better ventilation and cleaner air in the upper floors. the low age of air is also spread in larger proportions when the elevation height increases. as seen in the graphs, both low-and high-rise buildings form a wall that is oriented perpendicular to the prevailing wind patterns. this creates a barrier to the southeast winds and creates stagnant air in the leeward sides of the buildings. ideally, these built forms must be oriented parallel to the prevailing wind direction to ensure better ventilation and cleaner air. lower age of air and better ventilation is observed surrounding the smaller fragmented in the three diagrams above concentrated areas denote higher wind velocities. the short arrow strokes indicate low and long arrow strokes indicate high velocities. the red, yellow, green and blue strokes denote wind velocity in descending order building shapes and footprints. the areas surrounding larger blocks show high age of air and comparatively poor ventilation. in all three graphs, the row of high-rise building further away from the wind direction have a higher age of air spread in larger compositions compared to the row of buildings closer to the wind direction. observations confirm that the block size, orientations, building heights and distance from wind source affect the age of air, ventilation and air quality surrounding those buildings especially on the leeward side. the analysis can be further substantiated by the qualitative data gathered among occupants in high-rise living in hong kong (lau, 2002) . the general conceptions of occupants are that the apartments in higher floors are preferred due to better quality of environment -such quality can be specifically referred to as the air quality and reduced noise levels. the wind velocity graphs further confirm the observations made on the age of air distributions at varying heights. lower wind velocities are observed at low height levels. low wind velocities are also observed in the leeward sides of high-rise buildings, causing high age of air, poor ventilation and air quality in those areas. also, when the distance from wind source increases, the velocities decrease indicating the higher age of air surrounding built forms further away from the wind source. in order to enhance the wind environment in hong kong, an air ventilation issue has been included in the hong kong planning standards and guidelines. a set of qualitative guidelines and a framework for carrying out air ventilation assessment have been formulated on the basis of the air ventilation assessment study recommendations. the guidelines incorporated in the hong kong planning standards and guidelines are to strengthen the urban design guidelines for better air ventilation. the guidelines were developed according to the results of "feasibility study for establishment of air ventilation assessment system" (the ava study) was conducted and completed in 2005. in addition to the guidelines, a technical guide for air ventilation assessment (ava) has been issued by the planning department of hong kong (2005) . ava can be used to compare the air ventilation impacts of different design options and to identify the potential problem areas for design improvements. this technical guide specifies three steps in conducting ava, i.e. expert evaluation, initial study and detailed study. the expert evaluation is a qualitative assessment based on the guidelines provided in hong kong planning standards and guidelines, while the initial study will refine the expert evaluation and the detailed study will conclude the ava. the ava technical guide recommends using wind tunnel as the tool for carrying out both initial and detailed study. however, the use of computational fluid dynamic (cfd) will be permitted in the initial study (hong kong planning department, 2005) . the examples of using cfd simulation in ava study are presented in table 3 .4. this study highlighted the air ventilation benefits of raising the podium level of residential buildings. the table shows the comparison of mountain and valley breezes for base case and proposed designs. according to the mountain/valley breeze simulations, we can find that the mountain can create local winds that vary from day to night if there is no background wind, which can also increase the air flow around the buildings in the mid-level. during the daytime, the air near the mountain surface can be heated up and higher than the free air far away at the same height due to the solar radiation. thus the warm air moves up along the slopes. while during the night-time, as the mountain surfaces cool down, the cold breezes can be formed and flow down the slopes. the proposed new podium can enhance the air flow through the building. it can be imagined that the building region can benefit from the mountain breezes by bringing the cooled air at night-time on hot days. the thermal environment can be improved and energy can be saved (li & yang, 2008) . the air ventilation and daylight penetration into individual housing units play an important role in high-rise residential building designs. many factors determine the daylight quality within housing units. study done by the students of the final year bachelor of arts in architectural studies, department of architecture university of hong kong (2006 kong ( /2007 reveals several factors that determine the daylight quality within housing units. table 3 .5 illustrates the types of building footprints found in high-rise residential buildings in hong kong and the evaluation of the lighting quality within a selected individual housing unit. a qualitative appraisal of the lighting quality in individual rooms of the housing unit is done by its occupant. this is combined with a quantitative -daylight simulation for the residential units showing the distribution of lighting within the spaces. the distribution of lighting quality significantly varied across the building types and spaces/rooms within the individual units. lack of sufficient lighting and ventilation in the kitchen and washrooms were a common observation. obstructions to light due to windows being covered for better privacy and furniture layout were also observed as barriers to daylighting within the spaces. some spaces have no windows at all and may be for the purpose of storage. but due to the lack of sufficient living space such spaces are also used for habitation. on most occasions, occupants use artificial lighting in such spaces even during day-time. small window sizes and fixed glazing were also commonly noted as causes for poor light and ventilation. further, it can be observed that most kitchen and toilet spaces in high-rise buildings are ventilated via "re-entrant light wells". these are equivalent to a light well with the main purpose of bringing in light and ventilation . residents most often use the window opening into re-entrants for drying clothes, etc. the inlet and outlet water pipes to kitchen and toilets are located along the re-entrant spaces. the mechanical ventilation outlets are also located along these re-entrants that act as a shaft for bringing in fresh air as well as outlets for foul air from toilets and kitchen. the building shapes play a major role in determining the re-entrant shapes (see table 3 .5 for building shapes and re-entrant shapes). most often, the reentrants are too narrow and inadequate for bringing in light and ventilation. wider, more open re-entrant shapes are needed for sufficient light and ventilation. the size, number and positioning of windows, the floor area of space, windowfloor area ratio, the shape of the room and depth of space from window, internal reflectance of materials and finishes, the building footprint shape, external obstructions, building orientation, obstructions caused by neighbouring towers and distance between towers, external barriers to wind and daylight such as hills and internal furniture layouts all affect the quality of ventilation and daylighting within residential units in high-rise towers (final year bachelor of arts in architectural studies students, 2006 students, /2007 . a common issue is windows placed within the visibility range from neighbouring blocks cause lack of privacy. as a result, most windows are kept closed and covered using opaque materials such as shades, curtains, etc. blocking light and ventilation into the housing units. tables 3.6 and 3.7 illustrate the case studies and respective daylight analyses. uneven day light distribution in several spaces within the block is caused due to window sizes and numbers, the floor area, window-floor area ratio, the location of windows, shape of building foot print, interior furniture layout and distance between blocks and block layout, contextual barriers such as hills, obstructions from other buildings also determine the lighting quality and ventilating inside housing units of high rise blocks. windows facing neighbouring blocks are being constantly kept closed due to lack of privacy, thereby does not serve the purpose of brining in light and ventilation table 3 .6 day light study of high rise housing. sources: chan (2006 ), cheung (2006 , kei (2006 ), wong (2006 in addition, investigated the effect of relaxation of room height as a means for improving daylight conditions. the study investigated the relaxation of room heights from 2,800 to 3,650 mm and sustainable design features of proposed residential building located at mid-levels, hong kong. when window size remains the same and the room height is increased the day light within the room is improved but not a very significant improvement is seen. but when window size and room height is increased there is a significant increase in the daylight quality within the room. also graph shows that in room 2 with higher room height and larger window size the day light factor shows significant increase the simulations were carried out based on the parameters: date 21 dec (winter solstice), time 9:00 am, sky condition: overcast sky, design sky 8,500 lux. this analysis is regarded as the worst-case scenario for daylight calculation. three cases are presented in table 3 .8. the study revealed that an increase in room height has some effect on improving the daylight quality within a room. in addition, the increase of window height can make a significant contribution to the daylight quality within the room. outdoor living space of high-rise residential buildings is equally important. adequate provision of open space, greenery, vistas and visual corridors is a critical issue in the light of high land prices and the general lack of space between and around tall buildings. open spaces and landscaping on podiums are design measures taken to improve resident perceptions of open spaces, views and greenery. open spaces located close to highways, roadways, and transport nodes create poor environmental quality due to noise, dust and smoke emissions. in other words, it can be argued that even if open spaces are provided within residential blocks or outside in close proximity to homes, if its quality does not meet the demands and satisfaction of its users, such open spaces may not be efficiently utilised. podium open spaces and sky gardens create a barrier from traffic and pollution at road levels. yet, being surrounded by high-rise buildings these spaces have a tendency to trap pollutants due to a lack of cross ventilation and high building mass. the lack of green cover, trees and hard landscaping may contribute to poor micro climatic conditions in the outdoor spaces of high-rise developments (tan & fwa, 1992; wilmers, 1990 wilmers, /1991 . but, people are forced to use these open spaces despite its poor environmental quality. study by davies (1998) has shown that the most popular form of recreation among hong kong residents is the use of passive local open spaces. it is observed that the majority of users of such open spaces are elderly, low income groups whose accessibility to district open spaces and country parks may be limited. study of open space satisfaction among occupants of high-rise public residential estates in hong kong by coorey (2007) shows that satisfaction of open space is primarily dependent on the physical qualities as opposed to its social qualities. the physical qualities such as climatic comfort, maintenance, facilities and provisions were identified as having important implications on their overall satisfaction. the study involved 600 questionnaire interviews conducted in 6 high-density public housing estates in hong kong. respondents evaluated the physical and social quality of open space and their levels of satisfaction in 15 open spaces including those on podiums and ground level in the six high-rise developments. a comparison of open spaces located within public housing of varying density showed that occupants in higher density developments considered the physical qualities of open space such as climatic comfort, provision for open space and maintenance as having higher impact on their overall open space satisfaction. respondents living in the lower density cases tend to consider the social qualities such as safety, crowding, privacy and interaction to have a higher implication on their open space satisfaction (coorey, 2007) . the study highlighted the importance of environmental quality for optimum satisfaction of open spaces located within high-rise residential developments. it further highlighted that open space satisfaction among occupants living in higher density cases was significantly influenced by its environmental quality as opposed to its social qualities. such open spaces play a critical role in the lives of residents living in high-rise buildings as they are their only means of escape from the otherwise built up urban setting. additionally, its importance for the elderly and low-income groups, specifically draws on the need for optimizing the environmental quality of open spaces in high-rise developments. an increase in respondents' satisfaction with climatic comfort in open space is shown when the number of trees, the proportion of greenery is higher and the sky view factor is low due to taller buildings adjacent to smaller narrower open spaces (coorey, 2007) . noise pollution is a common environmental quality issue associated with mixed use and high connectivity with transport networks. taller buildings with residences in the higher floors are preferred due to less noise in the higher floors (lau, 2002) . also, elevated walkways and podiums serve as design principles for segregating pedestrian routes from noise and pollutant sources at street and ground levels. the podiums act as buffers from noise at ground level. the building clusters in hong kong are well integrated through elevated walkways subways and podiums that induce people to walk through buildings rather than being exposed to the fumes and noise of vehicular traffic at road levels. study of external noise measurements in the surrounding areas of an arts performing school showed that high traffic noise reflectance was caused by the faã§ade effect and canyon effect due to high-rise built forms running parallel to the roadways (lau, 2006) . measurements were taken alongside two roadways on opposite sides of the arts school. one roadway has high-rise buildings located alongside it while low-rise buildings frame the roadway on the opposite side. higher noise levels are observed from the roadway with high-rise buildings. the facades of high-rise built form act as reflectors for noise sources from vehicular traffic. the taller building forms create a canyon effect causing higher noise levels. it can be suggested that the building facades, orientations with the noise sources and its noise reflectance and absorption values must be manipulated. this can be done by orientating the buildings so that it does not obstruct and reflect noise. instead, it disseminates the noise and avoids a canyon effect. the materials of the facades should be of less reflectance and higher absorption values. in addition, trees and shrubs can be introduced as noise screens alongside roadways. zoning at planning stage must be done with an awareness of the noise sources and noise reflectors in the surrounding context. habitable spaces can be buffered by elevating the units above the noise source levels. soft landscaping features such as water fountains can be used to mask and create distraction from traffic noise. although tall residential buildings have many social and environmental implications, hong kong's topography and continuous increase in population have propelled the planning and design of hong kong's built form clearly in the direction of tall buildings. but how tall and how to design such tall building is the question of concern. the general policy and regulations provoke taller buildings. but the regulations and attention of hong kong designers are turned towards more sensitive design measures that will balance the demand for taller buildings with more sensitive, sustainable and liveable design features. the critical implications for building tall are mainly associated with poor air quality, lack of wind ventilation in a macro context of a high-rise city as well as the micro context within the residential units or apartments. poor daylighting quality within tall buildings is a pressing issue for tall buildings. the lack of open space and the poor environmental quality in such open space is another issue that impacts the quantity and quality of open space among highrise occupants. the noise levels due to reflectance from high-rise towers caused by faã§ade and canyon effects are also a challenge for zoning, orientations and design. such issues bring about specific criteria for zoning, planning and design in tall building contexts. this chapter highlighted some of the design issues and possibilities. the compact city: just or just compact? a preliminary analysis unpublished bachelor of arts in architectural studies final year projectwork unpublished bachelor of arts in architectural studies final year projectwork 2006-2007 policy address by chief executive. hong kong: hong kong sar government. last accessed feasibility study for establishment of air ventilation assessment system-executive summary. hong kong: department of architecture sustainable development of tall buildings in hong kong. paper presented at the tall buildings: from engineering to sustainability unpublished bachelor of arts in architectural studies final year projectwork design of open spaces in high density zones: case study of public housing estates in hong kong study of leisure habits and recreation preferences and review of chapter four of the hong kong planning standards and guidelines. final report, planning department final year bachelor of arts in architectural studies students -department of architecture university of hong kong planning for high density development in hong kong. hong kong: the planning department of hong kong climate consideration in building and urban design ifc, kornhill, telford, union square images in google earth milunet: multi functional intensive land use -principle, practices, projects, policies -towards sustainable area development. harbiforum foundation daylight analysis: residential buildings in hong kong outbreak of severe acute respiratory syndrome (sars) at amoy gardens, kowloon bay, hong kong -main findings of the investigations. department of health air quality in hong kong mtr properties. hong kong mass transit railway corporation, hong kong. last accessed technical guide for air ventilation assessment for developments in hong kong. hong kong planning department, hong kong. last accessed planning department annual report hong kong planning standards and guidelines. hong kong planning department low energy building design in high density urban cities sustainable urban form in developing countries daylight analysis: residential buildings in hong kong a survey on residents' responses to high rise living in hong kong. centre for architecture and urban design for china and hong kong traffic noise measurement for the school of performing arts sustainable building design: residential development reconsidering daylighting design parameters for tall buildings in densely built city hong kong: milu and how it is perceived policies for implementing multiple intensive land use in hong kong environmental performance analysis: proposed luxury residential development in shenzhen ventilation study of residential development at il 2510 & extension, 15 magazine gap road, mid-levels the compact city in practice: the new millennium and the new urban paradigm is there a role for physical planners technical guide for air ventilation assessment (ava) for developments in hong kong. planning department of hong kong, hong kong. last accessed influence of pavement materials on the thermal environment of outdoor spaces achieving sustainable urban form effects of vegetation on urban climate and buildings daylight analysis: residential buildings in hong kong. unpublished bachelor of arts final year projectwork call for law against 'wall effect' fails, south china morning post policies and planning of tall buildings in hong kong. paper presented at the tall buildings: from engineering to sustainability public space in the old derelict city area -a case study of mong kok, hong kong asia's walled city' leaves -residents longing for air, the standard key: cord-254340-e1x0z3rh authors: cruz, christian joy pattawi; ganly, rachel; li, zilin; gietel-basten, stuart title: exploring the young demographic profile of covid-19 cases in hong kong: evidence from migration and travel history data date: 2020-06-26 journal: plos one doi: 10.1371/journal.pone.0235306 sha: doc_id: 254340 cord_uid: e1x0z3rh this paper investigates the profile of covid-19 cases in hong kong, highlighting the unique age structure of confirmed cases compared to other territories. while the majority of cases in most territories around the world have fitted an older age profile, our analysis shows that positive cases in hong kong have been concentrated among younger age groups, with the largest incidence of cases reported in the 15–24 age group. this is despite the population’s rapidly aging structure and extremely high levels of population density. using detailed case data from hong kong’s centre for health department and immigration department, we analyze the sex and age distribution of the confirmed cases along with their recent travel histories and immigration flows for the period january to april 2020. our analysis highlights hong kong’s high proportion of imported cases and large overseas student population in developing covid-19 hotspot areas such as the united kingdom. combined with community action and targeted and aggressive early policy measures taken to contain the virus, these factors may have contributed to the uniquely younger age structure of covid-19 cases in the city. consequently, this young profile of confirmed cases may have prevented fatalities in the territory. recent research has highlighted the importance of a demographic approach to understanding covid-19 transmission and fatality rates. the experience in hong kong shows that while an older population age structure may be important for understanding covid-19 fatality, it is not a given. from a social science perspective at least, there is ‘no easy answer’ to why one area should experience covid-19 differently from another. the hong kong special administrative region of the people's republic of china (hereafter hong kong) is a city and special administrative region of china in the eastern pearl river delta by the south china sea. in 2019, hong kong had roughly 7.5 million people in a 1,104-square-kilometre (426 square miles) territory while in kowloon, where more than three in ten residents reside, population density is at 48,930 persons per square kilometer. this makes it one of the most densely populated territories in the world [1] . apart from being a rapidly aging society [2, 3] , hong kong is also a migration destination. for the period 2015 to 2020, the net migration number was 147,000 or a net of four in-migrants per 1,000 of the population [1] . hong kong faces the challenge of infectious diseases as a consequence of various factors, including high population density, increasing environmental pollution, high migration inflows and outflows, the emergence of new infections as well as the changing lifestyle and behavior of its residents [4, 5] . the most recent significant outbreak was the severe acute respiratory syndrome (sars) outbreak which reached hong kong in march 2003 [5] . based on world health organization (who) data until july 11, 2003 , a total of 1,755 sars cases had been identified in the territory, of which 298 people died of the disease [6] . at that point, it was largely believed that hong kong was unprepared to be one of the epicenters of the sars epidemic. from this recent experience, did hong kong learn from the hard lessons of the past? the who officially declared the novel coronavirus infections (hereafter covid-19) outbreak as a pandemic on march 11, 2020, after it had spread to more than 100 countries and resulted in tens of thousands of cases within a few months. in hong kong, however, the first case was reported on january 23, 2020. in early february, the government was strongly criticized for policy responses related to a variety of issues, including the legality of, and access to face masks; border closure; medical fees and quarantine policy [7] . during this early period, unfavorable comparisons were made with other regional governments (especially macau and singapore) who appeared to be managing the crisis more effectively [8, 9] . however, by the time of writing in june 2020, new cases being reported in hong kong-especially local transmissions-are very rare [10] . that this has occurred without the general lockdown policies seen in other parts of the world is even more remarkable. our study includes an examination of the age and sex distribution of the covid-19 confirmed cases in hong kong and an exploration of how the different measures to combat this outbreak resulted in a relatively low number of cases and deaths. specifically, as demographers, we wished to explore the extent to which insights from demographic science could assist in explaining the nature of the hong kong experience of covid-19. in this paper, we highlight the potential impact of the young profile of the confirmed cases on the total number of mortalities and the effect of early, aggressive policy measures including travel bans, enforced quarantines and contact-tracing imposed by the hong kong government as early as january 27, 2020 in containing the spread of the covid-19. data on confirmed covid-19 cases were taken from the centre for health protection (chp) of the hong kong department of health. we assessed the age and sex distribution of the confirmed cases, discharge status (discharged, hospitalized or died) and type of transmission. we obtained the data regarding cumulative cases by age group from january 23 to april 16, 2020, which allowed us to determine the age group that registers the highest number of confirmed cases over time. daily migrant inflows and outflows data was retrieved from the hong kong immigration department showing arrivals at each border checkpoint into hong kong broken down by citizenship status. in addition, we retrieved detailed archived datasets pertaining to the travel histories of confirmed covid-19 cases, which are updated on an almost daily basis by the chp. we excluded travel histories pertaining to domestic travel (buses, trains and ferries) and a small number of journeys pertaining to outbound from hong kong. we linked travel histories to confirmed case identifications (ids) in order to examine the age structure and timing of cases where the apparent source of infection was not in hong kong (i.e. not a community infection). these include cases with a travel history from countries with widespread infection or where infection from a confirmed case who traveled occurred. by doing so, we highlight the importance of returnee hong kong residents from overseas hotspots on the relatively young age structure of confirmed cases during the second wave in march 2020. we also gathered data on policy measures implemented by the hong kong government in order to highlight the possible impact of major border closures and quarantine arrangements imposed by the hong kong government in reducing further numbers of imported covid-19 infections. we also utilized secondary data for comparative demographic analyses from the hong kong census and statistics department, united nations population division and the chinese center for disease control and prevention. compared with the aging hong kong population [1] , the covid-19 confirmed cases have an entirely different distribution. fig 1 shows [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] . less than a tenth (7.9%) are aged 65 and over. this age distribution of the local covid-19 confirmed cases does not fit the general profile of other territories wherein the infections are more concentrated among those in the older age groups. although, of course, this may be related to testing patterns by age, rather than true differences in incidence. the who coronavirus disease 2019 situation report 89 shows that as of april 13, 2020, there were a total of 716,570 confirmed cases with reported information on age and sex coming from 113 countries, territories and areas; of these confirmed cases, the median age for males is 52 (interquartile range, iqr: 35-64) years and for females 50 (iqr 35-64) years [11] . examples of territories with an older profile of confirmed cases are mainland china where the majority of confirmed cases (54.0%) as of february 11, 2020 belong to the older age groups, at least 50 years old [12] , and the philippines wherein as of march 25, 2020, the majority of the confirmed cases are in the age group 50 and older [13] . there is also an imbalanced sex ratio among the covid-19 confirmed cases in hong kong with a higher proportion of male cases, representing 54% of the total. the number of male cases outnumbered females in almost all age groups, except in the 25-34 age group where they made up only 47% of cases. for all other age groups, male cases were between 50 to 60% of the total; an exception was for those aged under 15 of which 68% of cases were male, however, the total number of cases at this age was extremely small (25 out of the total 1,017 cases). this sex profile with a higher prevalence of male cases is similar to the outbreaks in other territories [12, 13] the youngest confirmed cases in hong kong were two males under one-year-old while the oldest confirmed case is a 96-year-old female. nearly half of the 1,017 confirmed cases (48.0%) had already been discharged from the hospital as of april 16, 2020. in short, covid-19 confirmed cases in hong kong were found primarily among the working and school-age groups, and to a certain degree, among men. by april 16, 2020, almost three months after the first reported case on january 23, 2020, four deaths among confirmed covid-19 cases were reported in hong kong. three such deaths were over 70 years old (two males and one female) while the fourth was the case of a 39-year old male. it is possible that this young age structure of confirmed cases in hong kong contributed to the extremely low numbers of fatalities compared to other territories. a large proportion of hong kong's confirmed cases were 'imported'. three in five confirmed cases (61.0%) have travel history from countries with widespread infection or were directly infected by a confirmed case who travelled; hence, they are considered cases with imported transmission (see fig 2) . two-fifths of these imported confirmed cases (41.1%) are young adults in the age group 15-24 years old. the proportion of imported versus local cases differs significantly based on age group. nine in ten of the confirmed cases in the 15-24 age group (91.4%), the group with the largest incidence of covid-19, were in fact imported. in contrast, 59.7% of cases aged 55-64 and less than half of those in other age groups are considered imported. most of hong kong's cases in the younger age groups occurred in a second wave of infections during march. before march 18, 2020, the age group with the highest frequency of covid-19 cases was 55-64 followed closely by the 65 and over age group (see fig 3) . however, after march 18, 2020 the number of new cases in hong kong sharply increased, most of these being imported cases in younger age groups. this timing of these imported cases is similar to that experienced by china wherein the imported cases more than doubled starting from march 18, 2020, mostly coming from countries with high outbreak of covid-19 infections like the united kingdom (uk), united states of america (usa) and spain [14] . however, age-specific data about imported cases is not available in china. analysis of the travel histories of hong kong cases suggests that the majority of imported cases in the 15-24 age group may be hong kong residents who are studying or working abroad. the travel history data collected and archived by the chp over the study period was matched to case numbers from the case data to study the travel history and age profile of all known imported cases. the data collected by the chp contains the travel histories of all confirmed covid-19 cases up to fourteen days before the case was reported and formed part of attempts of the government to track and trace the movements of all newly reported cases. this is done in order to contact and isolate anyone with whom they had close contact in the days before the onset of symptoms, including those whom they may have sat close to on flights. of the 508 covid-19 cases with an overseas travel history tracked by the chp, 47.4% were imported from the uk, 9.1% from the usa and 3.9% each from qatar, canada and switzerland. by far the largest age group with a travel history was those aged 15-24 with 205 cases, of which the majority were from the uk (62.4%), 8.3% from the usa, and 4.4% to 5.4% each from switzerland, qatar and the netherlands. the next largest group with travel histories was those aged 25-34 with 86 cases, nearly half of these coming from the uk (48.8%). we are not able to ascertain the employment or other characteristics of these cases. hong kong has a large population of mobile residents who hold citizenship or permanent residency but work, study or are retired overseas. according to the 2016 by-census, just under 220,000 permanent residents of hong kong were deemed 'mobile', meaning they had spent between one to three months in the city of the previous six [15] . in 2016, the largest population of mobile residents was those aged 15-24, with a total of 47,938 most of whom were registered as students. we were not able to obtain the country of temporary overseas residency from the census data. the next largest population of mobile residents were those aged 65 and over (42, 299 ) who were mostly registered as retired, while a further 40,926 were aged 55 to 64 mostly employees or retirees. in addition, according to the 2016 by-census hong kong is home to a sizable number of non-permanent residents; many of these residents may return to their home countries on a regular basis for study, work, or family visits. the largest groups of non-chinese nationals were filipinos (186,000) and indonesians (159,901), most of whom work as domestic workers on temporary foreign-worker permits. hong kong was also home to 35,069 british citizens, almost 15,000 americans and 66,690 citizens from south asian countries (india, nepal and pakistan), while a further 121,775 hong kong chinese were registered as being domiciled overseas in 2016 [15] . the large increases in newly confirmed cases in the younger age groups, the majority of which were imported, occurred from march 10, 2020 onward (fig 4) . this was in tandem with a large increase in confirmed cases and deaths throughout multiple countries in europe, usa and canada. on march 13, 2020, the hong kong security bureau had announced a 'red outbound travel alert' ('red ota') for the schengen area, announcing a mandatory 14-day home quarantine for all arrivals from the schengen area. this was followed by a 'red ota' for ireland, united kingdom and the usa on march 15, 2020 with the announcement of home quarantine arrangements for all travelers from the three states to begin four days later (see s1 table for a full timeline of policy events). fig 4 shows the arrivals into hong kong over the period from january 24 to april 16, 2020. most arrivals were hong kong residents travelling via the airport. on february 4, 2020, all land and sea border points were closed except for two control points-the shenzhen bay control point and hong kong-zhuhai-macao bridge. daily arrivals into the city fell dramatically after the end of the chinese lunar new year holidays at the end of january 2020, and took another dramatic fall after the home quarantine arrangements for all arrivals from china were put into place on february 8, 2020. arrival numbers followed a relatively steady pattern at under 25,000 per day until dropping off sharply from march 19, 2020, when the new 14-day home quarantine arrangements were put in place for all arrivals into the city, regardless of whether or not they were residents. from march 25, 2020, all non-residents were barred from entering the city except for nationals of macau, taiwan or mainland china. these border closures and sharply lower inbound-travel movements together with hong kong's aggressive policy of testing, contact-tracing and quarantine of confirmed cases and their close contacts (see s1 table) undoubtedly contributed to the sharp decline in newly confirmed cases during the month of april [16] . on april 20, 2020, hong kong recorded its first day without a confirmed case, from a peak of more than 60 cases per day in late march. social distancing and rapid population behavioral changes also likely played a role, with measures such as wearing masks, working from home and school closures leading to an estimated 44.0% reduction in seasonal influenza incidence [16] . the containment of a severe local outbreak of covid-19 in hong kong thus far, and the very high incidence of confirmed cases in younger age groups mostly among hong kong residents returning to the city from overseas hotspot areas, have surely contributed to the very low number of fatalities in the city-state, with only four deaths reported by april 23, 2020 out of 1,030 confirmed cases. one death occurred in the 80 years and over age group, out of twelve total cases. in italy, china and south korea, vastly higher case fatality rates were recorded for those in the older age groups; as at march 31, 2020 case fatality rates for those above 80 years old were at 27.7% in italy and 18.3% in south korea [17, 18] . this paper takes a social scientific approach to illustrate the particularities of covid-19 outcomes in hong kong up until now. the paper is a simple, descriptive analysis of the available data on hand. a recent paper highlighted the importance of a demographic approach to understanding covid-19 transmission and fatality rates [18] . the paper suggested that 'the age structure of a population may help explain differences in fatality rates across countries and how transmission unfolds.' fig 5 shows the full population pyramid for hong kong in 2016. observing the discrepancy in the shapes of the pyramids in figs 5 and 1, it is clear the experience from hong kong suggests that age structure alone is not a universal factor in shaping transmission and fatality rates. despite having more than 18.0% of the population 65 and over and an extremely high population density, a package of policies designed to contain the virus spreading from younger imported cases and becoming a sustained local outbreak ensured that case and mortality numbers stayed low. a further difference between hong kong and other settings characterized by higher rates of infection (and fatality) is the lower levels of distribution of residential care and support among older persons. there is strong evidence that people living in residential/nursing homes are particularly vulnerable to not only infection and its rapid spread, but to severe covid-19 infection and fatality [19] [20] [21] ; so much so that the who referred to care home infection and fatality rates as an "unimaginable human tragedy" [22] . in a study of official data in ten countries, deaths in care homes account for between 19-72% of all deaths [21] -although international comparison is difficult because of differences in cause of death reporting as testing procedures. in common with other parts of the world, the hong kong government has issued guidelines to support residential care homes in preventing infection [23] , as well as offering other support in terms of provision of personal protective equipment (ppes) and infection protection services [24] and a switch to online care support for those who would ordinarily visit day care centers [25] . there may thus be institutional reasons for the low levels of transmission among older people. the size and percentage of the older population resident in care homes differs widely around the world [26] . in the uk, where a high percentage of infections and fatalities have occurred in care homes [19, 20] , it is estimated that around 5.3% of the population aged over 70 is resident in care homes [27, 28] . in addition, a further 6.9% of that population receive care support in their own homes, including from carers making multiple home visits in a day-potentially another area of risk for infection [27, 28] . in contemporary hong kong, meanwhile, the proportion of over 70s in residential/nursing homes is estimated to be around 3.6% [1, 29] . these lower rates of care home residence may have contributed to lower overall transmission and fatality numbers among the elderly by creating lower opportunities for sustained local spread within the elderly population. low-income migrant workers, an already neglected group in terms of health and other support mechanisms during this pandemic [30] , represent a further group often characterized by communal living. highly elevated transmission rates have been seen in some settings where such migrant workers often live in cramped, unsanitary conditions [31] . in singapore, for example, over half of the purpose-built and factory-converted dormitories have been affected [32] ; a factor held primarily responsible for the 'second wave' of infections in the city-state. it has been estimated that some 80% of all cases have been linked to such dormitories. compared to singapore, such 'dormitories' are rare in hong kong. perhaps the primary, related housing issue in hong kong is 'subdivided housing'; home to up to 209,000 poor, urban individuals [33] and sometimes referred to as 'coffin houses' because of their very small sizes [34] . while often characterized by poor hygiene, low environmental [35] and safety standards [36] , it appears that policy measures in hong kong, which succeeded in stemming local transmission chains, meant these quasi-communal units were not left exposed to rapid covid-19 transmission. a final possible factor mentioned by dowd et al. [18] concerns the possibility that 'intergenerational interactions, co-residence, and commuting may have accelerated the outbreak in italy through social networks that increased the proximity of elderly to initial cases.' this would be derived from a mechanism whereby the younger population most susceptible to initial infection [37] transmit to the elder population through such contact. in hong kong, multi-generational residence is common [38] , where around 50% of those aged 65 and over live with their adult children [39] -much higher than in italy (or, indeed, any other setting in europe or north america characterized by high transmission rates) [40] . the extremely high population density of hong kong coupled with short distances and highly efficient transport systems means that there is a high degree of residential proximity as well regular contact between older parents and their children. a further dimension of intergenerational, intrahousehold interaction involves migrant domestic workers, who increasingly operate a major means of care support within the household. there is little evidence in hong kong that such workers were responsible for transmission within the household. as such, the hypothesis suggested for italy appears inconsistent with the hong kong case at least. the general quality of population health data in hong kong is generally accepted to be high, not least because of the centralized healthcare system in the territory. furthermore, in this case a very high degree of health surveillance and monitoring was in force throughout the period. this analysis relied heavily on secondary data for both the information on the confirmed cases and travel histories. given this, there are possible concerns for under diagnosis and under reporting especially during the start of the outbreak until before its first peak as have also been observed in other countries [41] . the unique age and sex distribution of the cases in hong kong may also be affected by testing patterns. there may, of course, have been unreported and/or asymptomatic cases in hong kong which will have escaped our analysis. however, there is no current consensus on such rates of asymptomatic infection and, therefore, how one might either estimate or correct in the hong kong case [42] . finally, the challenge of ascertaining primary cause of death and the role played by covid-19 interacting with other factors [43] [44] [45] is not a significant issue in hong kong given the very small number of deaths. a major limitation is that the spread of covid19 has not yet ended. any observations of a 'case in progress' are prone to future, unexpected changes which will change the narrative already described. of course, by the time this paper is published it is eminently possible that events have taken a turn for the worse and a third wave of infections occur. despite this, hong kong has clearly demonstrated a capacity to control both the transmission and fatality of covid-19 until this point. as of june 11, 2020 there have been no covid-19 ascribed deaths since march 14, 2020. furthermore, as of april 29, 2020, hong kong has reported no new cases for the sixth time in ten days [10] , and there were just five cases of local transmission in the month of may. from the start of may, public facilities began to reopen, some border restrictions were lifted, and civil servants returned to work in their offices. as of mid-june, public facilities such as beaches, libraries, museums, swimming pools have largely reopened, as have the last group of commercial leisure/entertainment facilities (karaoke lounges, nightclubs, bathhouses and party venues). clearly, much more research is required to concretely establish both the epidemiological and social factors contributing to the hong kong experience. the data which will allow such analysis will only come on stream in the future. at this point more complex statistical analysis will be able to be performed. furthermore, it will then become possible to link data on transmission and fatality through to other clinical and vital records (including the planned census in 2021). such data will also need to be complimented by survey data and qualitative research to provide a broader sense of the hong kong context. policy interventions, institutional systems, household and living arrangements each played a role in a complex, interwoven way. however, we must not overlook the role played by the community itself who, through behavioral change and increased vigilance, appear to have been equally instrumental in shaping hong kong's covid-19 experience. it may be in this way that the greatest lessons of sars have been learned [5] . supporting information s1 table. timeline world population prospects: the 2019 revision the population problem in pacific asia remeasuring ageing in hong kong sar; or "keeping the demographic window open prevention and control of communicable diseases in hong kong. government printer the sars epidemic in hong kong: what lessons have we learned? who. cumulative number of reported probable cases of sars. in: who [internet 7 reasons hongkongers are angry about the gov't response to the coronavirus macau's last covid-19 patient recovers, with no new cases for a month why did singapore have more coronavirus cases than hong kong? in: south china morning post another day of no new covid-19 cases in hong kong situation report-89. world health organization the epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (covid-19)-china demographic research and development foundation, inc. (drdf). covid-19 and the older filipino population: how many are at risk? uppi/ drdf research brief weekly assessment of the covid-19 pandemic and risk of importation-china population by-census impact assessment of non-pharmaceutical interventions against coronavirus disease 2019 and influenza in hong kong: an observational study. lancet public health the epidemiological characteristics of 2019 novel coronavirus diseases (covid-19 demographic science aids in understanding the spread and fatality rates of covid-19 death toll in uk care homes from coronavirus may be 6,000, study estimates. financial times number of deaths in care homes notified to the care quality commission, england. in: office for national statistics mortality associated with covid-19 outbreaks in care homes: early international evidence. international longterm care policy network unimaginable human tragedy" in europe's care homes, says who. japan times guidelines for residential care homes for the elderly or persons with disabilities for the prevention of coronavirus disease (covid-19) (interim) online day care keeping elderly hongkongers active during isolation nursing homes in 10 nations: a comparison between countries and settings how big is the problem in care homes? bbc office for national statistics kong ngo shows care homes they can stop keeping elderly in restraints. south china morning post the neglected health of international migrant workers in the covid-19 epidemic migrant workers in cramped gulf dorms fear infection current situation on migrant workers in dormitories-home thematic report: persons living in subdivided units tiny affordable housing in hong kong air and hygiene quality in crowded housing environments-a case study of subdivided units in hong kong a brief discussion on fire safety issues of subdivided housing units in hong kong social contacts and mixing patterns relevant to the spread of infectious diseases solidarity, ambivalence and multigenerational co-residence in hong kong. contemporary grandparenting: changing family relationships in global contexts living arrangements and older people's labor force participation in hong kong intergenerational co-residence during later life in europe and china level of underreporting including underdiagnosis before the first peak of covid-19 in various countries: preliminary retrospective results based on wavelets and estimating the extent of asymptomatic covid-19 and its potential for community transmission: systematic review and meta-analysis. medrxiv pathological findings of covid-19 associated with acute respiratory distress syndrome autopsy in suspected covid-19 cases case-fatality rate and characteristics of patients dying in relation to covid-19 in italy we would like to thank the academic editor and reviewers for their helpful and constructive suggestions. we would also like to thank professor stéphane helleringer for his comments on an earlier draft. the authors have declared that no competing interests exist. key: cord-017995-azqjvxtu authors: kwong, kim-hung; lai, poh-chin title: spatial components in disease modelling date: 2010 journal: computational science and its applications iccsa 2010 doi: 10.1007/978-3-642-12156-2_30 sha: doc_id: 17995 cord_uid: azqjvxtu modelling of infectious diseases could help gain further understanding of their diffusion processes that provide knowledge on the detection of epidemics and decision making for future infection control measures. conventional disease transmission models are inadequate in considering the diverse nature of a society and its location-specific factors. a new approach incorporating stochastic and spatial factors is necessary to better reflect the situation. however, research on risk factors in disease diffusion is limited in numbers. this paper mapped the different phases of spatial diffusion of sars in hong kong to explore the underlying spatial factors that may have interfered and contributed to the transmission patterns of sars. results of the current study provide important bases to inform relevant environmental attributes that could potentially improve the spatial modelling of an infectious disease. acute respiratory infections were transmitted through aerosol transmission of respiratory secretions from coughing and sneezing. conditions such as overcrowding and poor personal hygiene tend to facilitate the transmission of respiratory diseases [1] . education about personal hygiene and simple intervention measures such as washing hands can help to minimize disease incidence [2] [3] [4] . a model of sars transmission by riley et al. [5] suggested that the spread of sars is highly geographical and localized such that a complete ban on travel between local districts could expect to reduce the transmission rate by 76%. therefore, a closer examination of the sars occurrences in space and time could provide a better understanding of the spatial diffusion patterns and possible environmental factors contributing to such patterns. besides, an enhanced understanding of the spatial spread could extend knowledge on the detection of epidemics and help advice infection control and intervention measures. it is also known that conventional disease transmission models are inadequate in considering the diverse nature of a society and its location-specific factors [6] [7] [8] . this research made an attempt to map different phases of the spatial diffusion of sars in hong kong to identify the underlying spatial factors attributing to its transmission patterns. results from the study offer useful guidance about the selection of environmental risk factors for inclusion in the spatial modelling of an infectious disease. various efforts have been made to simulate the outbreaks of sars using mathematical methods [5] [9][10] [11] [12] . many of the models were based on the deterministic approach, such as seir, which incorporates the susceptible population (s), exposed/infected population (e), infectious population (i), and the recovered (immune) / removed (death) population (r) [5] [10] [12] . seir models explain the diffusion of a disease among the four population groups. seir and other related models often require little data, are relatively easy to set up, and can generally simulate infectious disease dynamics among the population [13] . such models, however, do not consider dynamic elements transpired by population mobility and social mixing; both of which are largely influenced by socioeconomic and environmental factors. small and tse [14] explained that these conventional models have an underlying assumption that each member of the entire population has an equal chance of being infected. such an assumption ignores the complex socio-demographic and environmental factors afflicting the transmission course of a disease among various subgroups (e.g., the wealthy, middle class, and the disadvantaged). a typical mathematical model suggests that a disease epidemic would ultimately infect the entire population [10] [12] . the reality is that certain communities may be affected less by an epidemic. for example, sars cases seemed to cluster in several disease "hot spots" in hong kong [15] . jefferson et al. [16] also reported that simple physical interruptions, such as systematic education on personal hygiene and isolation of infected patients, were effective in preventing the spread of respiratory diseases. hence, dye and gay [9] concluded that the next generation of disease models should include spatial processes and stochastic factors to tender a better solution to the problem. the geographic information system (gis) technology is well suited for analysing epidemiological data and characterising the spatio-temporal patterns of epidemics [15] [17] . epidemiological data often have a spatial context, such as the residential or work addresses of patients and the spatial patterns associated with a disease. efforts have been made to incorporate the dimension of space into disease simulation. sattenspiel and dietz [7] , for example, created an epidemic model that accounts for geographic mobility of the population in different regions. despite the assumptions of a single trip and a static population, their model was regarded superior to the conventional seir models because it considered in calculating the transmission risk both epidemic and behavioural processes, as well as environmental factors. small and tse [8] modelled the spread of sars using a small world model to simulate its spatial diffusion using the network structure. however, their model assumed that the environmental factors and population composition within the small world were homogenous. meng et al. [18] tried to employ spatial analysis to investigate and understand factors affecting the spatial transmission process of sars in beijing. they identified population density as a significant factor for the spatial diffusion in this case. however, "population density" alone may not reveal overcrowding conditions at the micro-level, especially in places like hong kong where a mixed land use is not uncommon and where non populated country parks are adjacent to urbanized areas. riley [17] documented four kinds of models (patch, distance, group and network) for the transmission of infectious diseases. he applied these models to simulate various disease outbreaks in the uk and found the group model to be the most suitable for human-to-human transmission of influenza. watkins et al. [19] also tried to model infectious disease outbreaks using a gis to incorporate traditional seir models in their simulations. their examples also showed that the establishment of a spatial model for contagious diseases (such as sars) was essential in understanding how the disease spread through time and space. furthermore, hsieh et al. [20] highlighted the importance of creating distinct and explicit spatial models for the understanding of the specific patterns of transmission of sars in each region or country. a new approach seems necessary to address the location-specific as well as environmental and socio-demographic risk factors for communicable diseases. however, only a limited number of studies (such as lau et al. [3] ) has identified some risk factors for the sars transmission in hong kong. this study is an attempt to isolate risk (or stochastic) factors to model the transmission dynamics of a disease in space. the study is based on data collected for the 2003 sars outbreak of hong kong. our approach attempts to extract features in space that contribute towards social mixing. we argue that social mixing is a function of transport infrastructures and can also be reflected through certain social-economic indicators. the study area covers the whole territory of hong kong and the data include 1,707 confirmed cases of sars occurring between february and june 2003. we divided the sars epidemic into four phases and by spatial units of 18 districts to explore its spread across space and time. our research hypotheses are as follows: 1) h 0 : there is no relationship between disease spread and transport infrastructure h a : disease spread follows the pattern of transport infrastructure 2) h 0 : there is no relationship between disease incidence and various socioeconomic characteristics (refer to section 3.3 for such characteristics) h a : disease incidence correlates with various socio-economic characteristics we obtained the sars data from the hong kong hospital authority. a patient record includes an identifier, residential address, hospital admission date, onset date of symptoms, hospital admitted to, as well as health conditions at admission. personal particulars of individuals were stripped and their residential addresses were replaced with geo-coordinates, with no information about flat numbers and building names, to ensure data privacy. we employed the 2004 geographical data (b5000 for the whole of hong kong) acquired from the lands department the hong kong special administrative region (hksar) government for spatial analysis and spatial modelling of sars. the ar-cgis 9.0 geographic information system software was used as a platform for data input and manipulation. maps were created to reveal the locations of sars cases. aggregation of cases to the 18 districts level was also made to extract potentially risky districts during various phases of the sars epidemic in 2003. demographic and census data of the general population were abstracted from the 2001 population census (in street block or small tertiary planning unit levels (stpu)) compiled by the census and statistics department of the hksar government [21] . we incorporated such data to investigate possible socio-economic factors that might have affected the spatial distribution of sars. as the human-to-human transmission of sars is through close contacts, variations in the socio-economic constructs by different spatial units might influence its spatial distributional patterns [4] . grids of 150m x 150m were created. sars data and census data were spatially joined to the grid level for analysis. we examined the relationship between the sars incidence and the following socio-economic characteristics as stipulated in hypothesis 2 above. a) percentage of population with tertiary level education b) percentage of population aged under 15 c) percentage of population aged over 65 d) non-working population e) median household income f) median personal income g) average number of rooms per household h) net residential density we followed the irish government's guidelines [22] when defining net residential density because there is no such guideline in hong kong. non populated areas (such as country parks) were excluded in our analysis. the reason for not using population density directly is because many areas in hong kong are of the mixed land use type (e.g. inner city areas of kowloon and northern hong kong island where residential areas are mixed with commercial / retail uses). moreover, some residential areas are also situated adjacent large plots of non populated country parks (please refer to figure 3 for such situations in kowloon and the hong kong island) which are often included in the total area of specific administrative districts or planning units. population density in these areas will therefore be under-represented and not reflecting truly how crowded a place is. statistical methods, including pearson's correlation co-efficient, were employed to determine the significance of various environmental and demographic factors contributing to the spatio-temporal transmission of sars. figures 1c and 1d) when sars became widespread throughout the whole territory of hong kong. an interesting point to note is that the north-south linear spread pattern in the early stages of the epidemic, as illustrated in figures 1a and 1b , corresponds to the east rail line which is a heavily used mass transit railway connecting kowloon and the northeast new territories (figure 2 ). it appears that transport might have an essential role in facilitating disease spread. a previous study of sars transmission in china also confirmed that modern public transport has a vital part in spreading contagious diseases like sars [23] . the study reported that sars had two major hotspots in guangdong and provinces near beijing. intersections of national highway, in particular, were a high risk factor for the spatial diffusion of sars. while an appropriate test of significance is not available, the visual evidence derived of the sars data in our study does suggest that the null hypothesis 1 is not substantiated. medical facilities could be another important contributor to the diffusion of sars. more than 10 workers in room 8a of the prince of wales hospital (pwh), where the first sars patient was admitted, were infected with sars in early march [24] . figure 1 shows that the sha tin district, where the pwh is located, was most severely affected by sars during the first two phases of the epidemic in 2003. confirmed cases in sha tin for phases 1 and 2 accounted for 34.9% (15 out of 43) and 28.2% (42 out of 149) of total sars cases in hong kong. the close proximity of residents in sha tin to the pwh, which is the primary source of nosocomial infection, meant that they were at a higher risk of contracting sars in the early phases of the epidemic. this is in line with lau et al. [2] [3] who suggested that more than a quarter of the sars patients in hong kong in 2003 were health care workers and hospital visit was a risk factor for contracting sars. similar conclusions were made by meng et al. [18] that medical care resources affected the spatial contagion of sars in beijing. socio-economic factors found statistically significant against sars incidence included the following: c) percentage of population aged over 65, g) average number of rooms per household, and h) net residential density ( table 1 ). all other variables did not exhibit a statistically significant relationship with the occurrence of sars. table 1 also shows that net residential density had a significant positive correlation with the occurrence of sars. figure 3 is a map of sars cases plotted over residential density in the city centres of hong kong (kowloon and the hong kong island). it illustrates that disease cases were concentrated mostly in areas of high residential densities. areas with lower residential densities in figure 3 (such as 1 -kowloon tong, 2 -southern district, and 3 -mid-levels) had fewer cases throughout the 2003 epidemic as shown in figure 1 . this observation matches that of a study by meng et al. [18] who demonstrated that population density was an important factor affecting the spatial diffusion of sars in beijing. the average number of rooms per household was also found to have a statistically significant negative correlation with sars because this factor is likely associated with residential density. people must share a room with their family members given fewer rooms per household in places with a high residential density. the percent of elderly population (over 65 years old) was statistically significant at the less stringent 95% instead of 99% confidence level. while the elderly have been found more susceptible to various types of infectious diseases including sars [25] [26] [27] , their less active social role could have ameliorated the chance of contracting a contagious disease. the results indicate that the null hypothesis 2 can be rejected for socio-economic characteristics of net residential density, average number of rooms per household, and elderly population. in other words, these three characteristics exhibited statistically significant correlation with the occurrence of sars in hong kong. these socialeconomic factors could be used to explain the transmission patterns of the 2003 sars epidemic. new and re-emerging of infectious diseases post challenges and threats to the health systems of many countries. while medical treatment of patients with contagious diseases has been top priority in curtailing epidemics, surveillance and early warning are equally important [1] . deterministic and mathematical models of communicable diseases are not adequate as a decision tool because they fall short of providing information about an epidemic form the spatial perspective. moreover, these models are not able to account for stochastic factors that influence the spatial dispersion of a disease outbreak. previous studies of the diffusion of sars in hong kong and beijing have shown evidence of geographical concentrations of sars cases [15] [18] . further efforts to incorporate stochastic events in modelling the spatio-temporal transmission of an infectious disease such as sars are therefore necessary. gis provides an integrated platform for the examination of spatio-temporal diffusion of a disease. this research studies sars diffusion in space and various temporal phases of the 2003 epidemic using the gis technology. we have identified some environmental and demographic factors deemed important in affecting the spatial transmission of sars. obtaining results that are in line with similar studies in other places, our study concluded that environmental factors (in this case, transport infrastructure and hospital locations) played a key role in shaping the diffusion pattern of 1 2 sars. certain socio-economic factors (i.e., average number of rooms per household, percentage of elderly population, and net residential density) were found to correlate positively with the occurrence of sars in hong kong, indicating their potential influence in the disease transmission. the research findings set the groundwork for the construction of a combination of stochastic and geographical-based models to simulate the transmission patterns of an infectious disease in space and time. previous studies have documented deficiencies of deterministic models in addressing spatial differences and severity of an epidemic. this research mapped different development phases of the sars epidemic in hong kong and employed the pearson's correlation to isolate environmental factors and socio-economic factors of significant pertinence to the disease. the results are useful in paving the ways forward to study disease transmission in space and time. future studies may take heed of our research findings to construct spatial models of disease transmission. the risk factors identified in this study could be incorporated in the modelling process to improve model predictability. communicable diseases in complex emergencies: impact and challenges probable 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2020-08-16 journal: j emerg med doi: 10.1016/j.jemermed.2020.06.048 sha: doc_id: 306910 cord_uid: qwaoe5du nan what is the relationship between freedom and health in an era of viral crisis? i write to share my perspective on responses to the coronavirus disease 2019 (covid-19) pandemic as an american emergency physician living in hong kong who was recently required to wear a tracker wristband and subjected to mandatory home quarantine. i did my residency training in new york city and have watched with dismay as the covid-19 pandemic has engulfed my former home and forced many colleagues to work on the frontlines with inadequate supplies of personal protective equipment. what hopes might hong kong's approach to infection control offer for new york and other cities in the united states? i returned to hong kong on march 19, the first day of the city's mandatory 14-day home quarantine policy for all incoming travelers. this home quarantine policy was part of a broader infection control system in hong kong involving universal hospitalization of all positive covid-19 cases, exhaustive social contact tracing, and selective quarantining of high-risk individuals. despite a recent ban on face coverings enacted last october in response to political protests, wearing face masks has also become a universal social practice in hong kong since the first covid-19 patient was diagnosed here on january 23 (1). not surprisingly, everyone i encountered on my arriving flight and throughout the airport was wearing a face mask, and some even donned hazmat suits or rain ponchos. after recording my body temperature, no fewer than three different centre for health protection (chp) workers asked me about my recent travel history. compare this with my entry into the united states a week earlier at los angeles international airport (lax), where no temperature checks or forms were provided and i was asked only a single question prior to being admitted to the country: ''you haven't been to china recently, have you?'' i also felt social pressure to remove my face mask to avoid attracting unwanted attention while going through passport control at lax (over 3 weeks prior to the centers for disease control's about-face recommendation on april 3 that all americans wear cloth face masks) (2) . when i arrived in hong kong, all adults and children older than age 6 years who had traveled anywhere other than taiwan, macau, and mainland china during the standard incubation period were required to undergo a mandatory 14-day home quarantine (this has since been upgraded to include mandatory testing) (3). i was instructed to fill out a quarantine order form in duplicate, which requested a home address and mobile phone number. i was then fitted with a ''quarantine tracker'' wristband-a strip of waterproof paper printed with a unique serial number and matching qr code and affixed around my wrist with a plastic clasp (figure 1 ). the chp officer instructed me to expect a short message service (sms) notice on my mobile phone for guidance on my next steps. the sms finally arrived on the second day, instructing me to download and install the ''stay home safe'' application on my mobile phone. after scanning my qr code, the app then informed me i would have 1 minute to walk slowly around the perimeter of my home to mark the boundaries of my confinement in ''cellular'' space. unfortunately, the app stopped tracking after 30 seconds, leaving me midway through my perambulation with my bedroom unscanned. this turned out to be quite significant: every time i ventured out of the scanned zone for the next 13 days, this triggered a loud warning and i was given 15 seconds to tap ''validate'' on the app and confirm my presence at the place of quarantine by scanning the qr code on my wristband. home quarantine violators risked being sent to mandatory government quarantine camps, a maximum fine of 25,000 hong kong dollars (hkd), and imprisonment for 6 months (4). tracker wristbands, monitoring apps, and threats of law enforcement seem anathema to most americans and other citizens of western liberal democraciesperhaps too high a price to pay for public health. yet i would argue that this dichotomy between freedom and health is a false one. i returned to hong kong knowing that i would be placed under quarantine for a defined period. i willingly accepted this mandatory confinement with the knowledge that i would be released in 14 days (or if i fell ill, that i would be guaranteed full medical treatment). people in the united states and europe are experiencing even greater infringements on personal liberty, as national lockdowns and shelter-in-place orders continue to get extended. in hong kong, the quarantine wristbands are a sign of a functioning public health system-even if they are merely strips of paper. by quarantining the most at-risk individuals (including travelers and close contacts), hong kong's approach enables most of the population to maintain freedom of movement-including the confinees after their 14-day stint. after completing my home quarantine, i was able to venture out from my apartment (with my mask on)-confident in being disease free and that most of those around me were also disease free. i am not saying that hong kong's situation is ideal, as the city faces significant political problems that are simply on hold during the pandemic. but hong kong's experiments with quarantine provide important lessons for other places currently facing lockdowns. the logic in the united states focuses on ''flattening the curve'' and avoiding overwhelming an already overburdened medical system. but this is not enough. in hong kong, quarantining works in tandem with a broader public health system that offers universal health care regardless of employment status, and an integrated set of infection control policies. by quarantining the few for a set period (the 14-day incubation period), the many can go about daily life with the relative assurance that they will likely not encounter someone infected by covid-19. i hope that the extreme measures taken elsewhere will not just ''flatten the curve,'' but also allow time to ramp-up public health responses. i believe that a functioning public health system is what will ultimately secure both freedom and health. government of the hong kong special administrative region. chp announces latest situations and measures on imported cases of novel coronavirus infection recommendation regarding the use of cloth face coverings government of the hong kong special administrative region. dh strengthens health quarantine and testing arrangements for inbound travellers government of the hong kong special administrative region. compulsory quarantine of persons arriving at hong kong from foreign places regulation gazetted clockwise from top right: quarantine wristband, quarantine app detection-in-process, short message service (sms) received on the last day of quarantine, and the ''stay home safe key: cord-290965-7qs4w9xh authors: kwok, w. c.; wong, c. k.; ma, t. f.; ho, k. w.; fan, w. t. l.; chan, k. p. f.; chan, s. k. s.; tam, c. c. t.; ho, p. l. title: border restriction as a public health measureto limit outbreak of coronavirus disease 2019 (covid-19) date: 2020-11-03 journal: nan doi: 10.1101/2020.10.29.20222190 sha: doc_id: 290965 cord_uid: 7qs4w9xh background: coronavirus disease 2019 (covid-19) led to pandemic that affected almost all countries in the world. many countries have implemented border restriction as a public health measure to limit local outbreak. however, there is inadequate scientific data to support such a practice, especially in the presence of an established local transmission of the disease. method: a novel metapopulation susceptible-exposed-infectious-recovered (seir) model with inspected migration was applied to investigate the effect of border restriction between hong kong and mainland china on the epidemiological characteristics of covid-19 in hong kong. isolation facilities occupancy was also studied. results: at r0 of 2.2, the cumulative covid-19 cases in hong kong can be reduced by 13.99% (from 29,163 to 25,084) with complete border closure. at an in-patient mortality of 1.4%, the number of deaths can be reduced from 408 to 351 (57 lives saved). however, border closure alone was insufficient to prevent full occupancy of isolation facilities in hong kong; effective public health measures to reduce local r0 to below 1.6 was necessary. conclusion: as a public health measure to tackle covid-19, border restriction is effective in reducing cumulative cases and mortality. conclusion: as a public health measure to tackle covid-19, border restriction is effective in reducing cumulative cases and mortality. 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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint article summary a novel metapopulation seir model with inspected migration was developed to investigate the epidemiological characteristics of covid-19 in hong kong, guangdong and the rest of china (excluding hubei) in the presence or absence of border restriction. the presented model is also suitable for further analysis of other emerging infectious diseases. border restriction is an effective public health measure in reducing cumulative cases and mortality for covid-19. interaction was assumed to be well-mixed within patch. the spatial effect in disease transmission within each patch is ignored, which can have a non-trivial effect on the dynamic of infectious disease. the proposed model is deterministic in nature which ignores the randomness in migration and in the interactions among people; a stochastic model would be more realistic especially early in the disease. 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. whereas later cases were predominantly mediated by human-to-human transmission (3) . transmission through asymptomatic contact also seemed highly probable (4), a feature that was not previously seen with sars-cov or mers-cov. clinical spectrum of sars-cov-2 infection ranges from flu-like illness to pneumonia with rapid progression to acute respiratory distress syndrome (ards) and death (1, (5) (6) (7) . among hospitalized patients, 32% to 51% had underlying disease and 26% to 32% of them required intensive care unit admission. the fatality rates for hospitalized covid-19 patients varies between 0·6% to 15% (1, 6, 7) but the true disease-specific mortality rate is unclear because the proportion of asymptomatic and mild infections remains uncertain. 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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint covid-19 rapidly evolved and became a pandemic. as of 20 th july 2020, there were more than 14 million covid-19 over the world (8) . to limit the scale of local disease outbreak, many countries implemented travel restriction towards travellers from regions with severe covid-19 outbreak and even all other countries, despite the world health organization (who) advising against implementing travel restriction as a public health measure to tackle covid-19. hong kong is a special administrative region of the people's republic of china and border control exists between the two regions. owing to the tight geographical and socio-economic ties, more than forty-million individuals travelled from mainland china to hong kong in a year (9) . china was the earliest country with covid-19 outbreak. on 23 rd january 2020, hong kong confirmed its first imported case of covid-19 from hubei (10). in the subsequent weeks, the number of imported cases rapidly rose despite initiation of various public health measures. medical professionals and the general public repeatedly urged the hong kong government to close the hong kong-chinese border to stop further influx. however, some questioned the effectiveness of such measure as there was already sign of local transmission in hong kong. some believed that border restriction is not useful in the presence of established local transmissions as the final disease burden might be primarily driven by local transmission instead of importing of foreign 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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint to date, there is inadequate scientific data to support border restriction as a public health measure to limit local outbreak of an emerging infectious disease in the presence of an established local transmission. the objective of this study is to assess the impact of border restriction on cumulative caseload and hospital occupancy with a novel metapopulation susceptible-exposed-infectious-recovered (seir) model with inspected migration. projection of covid-19 epidemiology in hong kong and mainland china will be performed as an illustration. 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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint in this study, a novel metapopulation seir model with inspected migration was applied to investigate the epidemiological characteristics of covid-19 in hong kong, guangdong and the rest of china (excluding hubei) in the presence or absence of border restriction. guangdong was separately analyzed from the rest of china because guangdong province had significantly higher confirmed cases per population (11·7 per million) than the rest of china (excluding hubei) (9·5 per million) as of 20 th february 2020. hubei province, with the highest case density in china (1048·4 per million), was excluded from analysis as all hubei-hong kong travel was banned after the wuhan lockdown on 23 rd january 2020. real world data up to 8 th february 2020 was used. seir type models are commonly adopted to simulate epidemiology of infectious disease of a single region over time. it is based on a system of ordinary differential equations (ode) that governs the number of 4 types of individuals: susceptible (s), exposed but latent (e), infectious (i), and recovered (or death) (r). conventional single-patch seir models are not suitable for studying the impact of border restriction of an emerging infectious disease. a novel modified metapopulation seir model with inspected migration was used in this study. in addition to simulating population migration, parameters such as efficiency of custom inspection in blocking infected travellers were also being incorporated. details of the model were described in appendix 1. assumption 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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint it was assumed that there were no vital dynamics and well-mixed within patch for simplicity. disease transmission between patches was assumed to be contributed by migra the mean incubation and infectious period was taken as 5·2 and 5·0 days respectively (3) . coronavirus transmissibility has been hypothesized to reduce as temperature rises (13), hence ܴ 0 is set to be inversely correlated with temperature. (which was not certified by peer review) is the author/funder, who has granted medrxiv a license to display the preprint in perpetuity. the hong kong public health system had a maximum of 952 isolation beds in 490 isolation single rooms according to the data from hospital authority press conference on 1 st march 2020. it was assumed that all isolation facilities were used exclusively for covid-19 purposes. 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 november 3, 2020. of 1·6 -2·1, complete border closure was projected to cause a 11·54 -13·71% reduction in cumulative cases and mortality ( figure 1 and table 2 ). the results suggested that even in the presence of established local transmission, travel restriction remains an effective measure to reduce the cumulative cases in the recipient region. covid-19 associated mortality can also be decreased with this measure. maintaining complete border closure and having effective public health measures to keep ܴ 0 below 1.6 is required to allow hong kong to meet its isolation room require-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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint ment. other permutations are shown in table 3 , and graphically represented in figure 2 . countries or cities with a high population density and aged population including hong kong is at risk of severe outbreak of emerging infectious diseases such as covid-19. as the disease is spreading rapidly in multiple continents, many countries implemented border restrictions towards regions with severe outbreak in order to reduce local case number and mortality. this is particularly important for developing countries with inadequate medical resources to tackle massive local outbreak. however, the who advised against utilizing travel restriction as an infection control measure. furthermore, it is particularly challenging to implement border restriction in certain regions due to political, social and economical reasons. to date there is inadequate scientific data to support border restriction as a public health measure to limit the scale of local outbreak in the presence of an established local transmission. using hong kong and mainland china as an example, we quantitatively illustrated border restriction is effective in reducing cumulative caseload, mortality and healthcare facility occupancy with a novel metapopulation seir model with inspected migration. it was projected that complete border closure will result in meaningful reduction of cumulative cases (4079 cases at ܴ 0 of 2·2), mortality (57 deaths at 1·4% in-patient mortality) and a delay in isolation facility overload in hong kong. it is important to emphasize that in our projection, border closure alone is insufficient to prevent healthcare overload, as measured by isolation facilities occupancy. effective 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 november 3, 2020. in the past few months, multiple regions had exponential rise in covid-19 cases which caused extreme stress to their local health care system. in wuhan, which was the epicenter of the covid-19 outbreak in china, severe shortage in isolation facilities urged urgent construction of multiple temporary hospitals. covid-19 related mortality in regions with severe outbreak tend to be higher due to relative shortage of medical resources outweigh demand. advanced life support facilities such as intensive care unit, ventilators, extracorporeal membrane oxygenation (ecmo) machines and anti-viral 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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint medications were essential in severe covid-19 cases but their availability is limited. in addition, covid-19 also severely hinder other non-covid-19 related medical services. in hong kong, although the total confirmed covid-19 cases is less than the available isolation facilities at the moment, a significant proportion of other less urgent medical services include elective investigations and surgeries have been suspended to reserve resources for covid-19. in less resourceful regions, the effect may even be more pro the spread of infectious disease is closely related to the migration of population between regions (19, 20) . conventional single-patch seir models are not suitable for such analysis. a novel metapopulation seir model with inspected migration was specifically developed for this purpose. in addition to covid-19, the developed model can be used to perform projection for other emerging infectious diseases in the future. furthermore, parameters such as effectiveness of custom inspection were included to improve 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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint accuracy of projection. the presented model is also suitable for further analysis of other emerging infectious diseases. firstly, interaction was assumed to be well-mixed within patch. the spatial effect in disease transmission within each patch is not directly addressed in the model, which can have a non-trivial effect on the dynamic of infectious disease (21) . secondly, the proposed model is deterministic in nature which ignores the randomness in migration and in the interactions among people; a stochastic model would be more realistic especially early in the disease. thirdly, key parameters such as rate of spread is still unclear so we assumed a parametric form of the rate of spread with reference to 2003-sars. in general, parameter calibration can be performed by some criteria, for example, minimizing residuals sum of square between the historical and fitted infected cases. meanwhile, missing information, such as travel history across regions, leads to crucial statistical uncertainty. a stochastic metapopulation migration model to explore the corresponding statistical properties with data would be a fruitful direction in the future. while the above shortcomings may be the expected tradeoff between computation time and model simplicity, it will not negate the signal that core message that border restriction reduces cumulative case, mortality and delay healthcare system exhaustion. lastly, economic impact is beyond the scope of this study. while full border closure can have a negative impact on the economy, one cannot ignore the negative economic impact from an otherwise preventable major outbreak. at time of writing, covid-19 was perceived to have developed into a pandemic situation and global stock market plummeted with the dow jones index and hang seng index both fell more than 9% percent since 2/1/2020. 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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint as a public health measure to tackle covid-19, border restriction is effective in reducing cumulative cases and mortality. hospital occupancy can be reduced but effective public health measures to achieve significant reduction in ܴ 0 would be necessary to prevent full occupancy of available isolation facilities. 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 november 3, 2020. ; https://doi.org/10.1101/2020.10.29.20222190 doi: medrxiv preprint this research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. no potential conflict of interest was reported by the authors. the lead author (the manuscript's guarantor) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained. ethical approval is not required as this study does not involve patients. our study is reported according to the gather statement. · data sharing: no additional data available. 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 november 3, 2020. ; (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 november 3, 2020. ; clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in wuhan a pneumonia outbreak associated with a new coronavirus of probable bat origin early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia. the new england journal of medicine transmission of 2019-ncov infection from an asymptomatic contact in germany. the new england journal of medicine a familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster clinical features of patients infected with 2019 novel coronavirus in wuhan epidemiologic and clinical characteristics of novel coronavirus infections involving 13 patients outside wuhan 2019-novel coronavirus (2019-ncov): estimating the case fatality rate -a word of caution centre for health protection of the department of health h. latest situation of cases of novel coronavirus infection centre for health protection of the department of health h. severe respiratory disease associated with a novel infectious agent 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 clinical characteristics of coronavirus disease 2019 in china impact of public health interventions in controlling the spread of sars: modelling of intervention scenarios population biology of infectious diseases: part ii cities and villages: infection hierarchies in a measles metapopulation 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 understanding the spatial clustering of severe acute respiratory syndrome (sars) in hong kong 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 hospitalized patients with 2019 novel coronavirus-infected pneumonia in wuhan, china a pneumonia outbreak associated with a new coronavirus of probable bat origin early transmission dynamics in wuhan, china, of novel coronavirus-infected pneumonia. the new england journal of medicine transmission of 2019-ncov infection from an asymptomatic contact in germany. the new england journal of medicine a familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster clinical features of patients infected with 2019 novel coronavirus in wuhan epidemiologic and clinical characteristics of novel coronavirus infections involving 13 patients outside wuhan 2019-novel coronavirus (2019-ncov): estimating the case fatality rate -a word of caution centre for health protection of the department of health h. latest situation of cases of novel coronavirus infection 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 clinical characteristics of coronavirus disease 2019 in china key: cord-274112-6t0wpiqy authors: webby, rj; perez, dr; coleman, js; guan, y; knight, jh; govorkova, ea; mcclain-moss, lr; peiris, js; rehg, je; tuomanen, ei; webster, rg title: responsiveness to a pandemic alert: use of reverse genetics for rapid development of influenza vaccines date: 2004-04-03 journal: lancet doi: 10.1016/s0140-6736(04)15892-3 sha: doc_id: 274112 cord_uid: 6t0wpiqy background: in response to the emergence of severe infection capable of rapid global spread, who will issue a pandemic alert. such alerts are rare; however, on feb 19, 2003, a pandemic alert was issued in response to human infections caused by an avian h5n1 influenza virus, a/hong kong/213/03. h5n1 had been noted once before in human beings in 1997 and killed a third (6/18) of infected people.1, 2 the 2003 variant seemed to have been transmitted directly from birds to human beings and caused fatal pneumonia in one of two infected individuals. candidate vaccines were sought, but no avirulent viruses antigenically similar to the pathogen were available, and the isolate killed embryonated chicken eggs. since traditional strategies of vaccine production were not viable, we sought to produce a candidate reference virus using reverse genetics. methods: we removed the polybasic aminoacids that are associated with high virulence from the haemagglutinin cleavage site of a/hong kong/213/03 using influenza reverse genetics techniques. a reference vaccine virus was then produced on an a/puerto rico/8/34 (pr8) backbone on who-approved vero cells. we assessed this reference virus for pathogenicity in in-vivo and in-vitro assays. findings: a reference vaccine virus was produced in good manufacturing practice (gmp)-grade facilities in less than 4 weeks from the time of virus isolation. this virus proved to be non-pathogenic in chickens and ferrets and was shown to be stable after multiple passages in embryonated chicken eggs. interpretation: the ability to produce a candidate reference virus in such a short period of time sets a new standard for rapid response to emerging infectious disease threats and clearly shows the usefulness of reverse genetics for influenza vaccine development. the same technologies and procedures are currently being used to create reference vaccine viruses against the 2004 h5n1 viruses circulating in asia. in february, 2003, two family members were admitted to intensive care wards in hong kong special administrative region with influenza-like respiratory illness. avian-like h5n1 influenza viruses were isolated from both patients, one of whom succumbed to infection. this was the first time since 1997 that h5n1 viruses had been identified in human beings, and who responded by issuing a pandemic alert. candidate vaccines were immediately sought. the recent outbreak of severe acute respiratory syndrome (sars) had been a striking example of the rapid and global spread of an emerging infectious disease. however, even the effects of sars could be dwarfed by those that could arise with the emergence of an influenza pandemic. infection caused by the influenza a virus is a zoonosis, and the animal reservoir of this virus is the aquatic bird populations of the world. the compelling epidemiological link between the presence of the virus in poultry in live-bird markets and the appearance of h5n1 in human beings in 1997 suggested that influenza a viruses can be transmitted directly from avian species to man and can cause severe respiratory disease. [1] [2] [3] although control of the 1997 outbreak was achieved by culling millions of birds in the hong kong markets, 4 this episode demonstrated that the capability for an effective global response to emerging influenza threats was poor because of technical, legislative, and infrastructural limitations. a disturbing finding that emerged from this event was that the scientific community was unable to produce an effective vaccine even after several years. the inactivated human influenza vaccines in use today are derived from essentially modified viruses. by exploiting the segmented nature of the influenza a genome, vaccine manufacturers and the laboratories of the who influenza network have produced a reassortant virus carrying the circulating virus's gene segments that encode haemagglutinin and neuraminidase, the major targets of neutralising antibodies. the remaining six-gene segments are supplied from pr8, a laboratoryadapted avirulent h1n1 strain. 5 the resulting reassortant virus has the antigenic properties of the circulating strain and the safety and high-yield properties of pr8. the first batch of inactivated material against the 1997 h5n1 virus was not ready for clinical trial until 7 months after the second case of human infection arose, and even today the effectiveness of vaccine against this virus has not been proven. 6 a key reason for this delay in the production of an h5n1-specific vaccine was the nature of the virus itself. the h5n1 virus is highly pathogenic in human beings and poultry. the agent must be handled only under conditions of at least biosafety level 3 (bsl3), and it can kill fertilised chicken eggs, the standard medium for the reassortment and responsiveness to a pandemic alert: use of reverse genetics for rapid development of influenza vaccines propagation of influenza virus before its inactivation and formulation for use in vaccines. these same traits are present in the 2003 h5n1 virus. the pathogenic nature of these h5n1 viruses is linked to the presence of additional basic residues in haemagglutinin at the site of cleavage, a step required for haemagglutinin activation and, thus, for virus entry into cells. [7] [8] [9] to overcome the high pathogenicity of the virus, polybasic aminoacids have to be eliminated. a rapid, reproducible system to achieve these modifications-ie, plasmid-based reverse genetics-has been developed only in the past 4-5 years [10] [11] [12] the potential benefits of reverse genetics for the generation and attenuation of vaccine candidates against highly pathogenic and low pathogenic influenza viruses are enormous. [13] [14] [15] however, the host specificity of the rna polymerase i promoter used in the influenza reverse-genetics systems and the required use of an approved cell line limits the practical options for the system's use in the manufacture of human vaccines. the vaccine-candidate reference virus stock described in this report has been produced entirely on a cell substrate licensed for the manufacture of human vaccine, and as such, is-to our knowledge-the first reverse genetically derived influenza vaccine suitable for testing in clinical trials. we describe the construction of a vaccine reference virus in good manufacturing practice (gmp)-grade facilities in less than 4 weeks from the time of virus isolation. our findings highlight the speed with which new technologies can be implemented in response to influenza pandemic alerts. we obtained who-approved vero cells (who-vero, x38, p134) from the american type culture collection (manassas, virginia, usa). passage-142 cells (five passages since their removal from a working cell bank) were used for the rescue of the vaccine-candidate virus. the plasmids containing the genes from pr8 have been described elsewhere. 13 virus propagation, rna extraction, pcr amplification, and haemagglutinin and neuraminidase gene cloning we obtained a/hong kong/213/03 (h5n1) that had been passaged in eggs from the who influenza network. the virus was isolated and propagated in 10-day-old embryonated chicken eggs. total rna was extracted from infected allantoic fluid with use of the rneasy kit (qiagen, valencia, ca, usa) in accordance with manufacturer's instructions. reverse transcription was carried out with the uni12 primer (5ј-agca aaagcagg-3ј) and amv reverse transcriptase (roche, indiana biochemicals indianapolis, usa). the removal of the connecting peptide of the haemagglutinin was done with use of pcr with the following primer sets: (1) bm-ha-1 (5ј-tattcgtctcagggagcaa aagcagggg-3ј) and 739⌬r (5ј-taatcgtc tcgtttcaatttgagggctatttctgagcc-3ј); and (2) 739⌬f (5ј-taatcgtctctgaaa ctagaggattatttggagctatagc-3ј) and bm-ns-890r (5ј-atatcgtctcgtattagtag aaacaagggtgtttt-3ј). we amplified the neuraminidase gene of a/hong kong/213/03 using the primer pair ba-na-1 (5ј-tattggtctc agggagcaaaagcaggagt-3ј) and ba-na-1413r (5ј-atatggtctcgtattagtagaaacaag gagtttttt-3ј). pcr products were purified and cloned into the vector phw2000 as described previously. 11 the rescue of infectious virus from cloned cdna was done under gmp conditions. vero cells were grown to 70% confluency in a 75 cm 2 flask, trypsinised (with trypsin-versene), and resuspended in 10 ml of opti-mem i (invitrogen, carlsbad ca, usa). to 2 ml of cell suspension we added 20 ml of fresh opti-mem i; then, we added 3 ml of this diluted suspension to each well of a six-well tissue culture plate (about 1ϫ10 6 cells per well). the plates were incubated at 37°c overnight. the next day, 1 g of each plasmid and 16 l of transit lt-1 transfection reagent (panvera, madison, wi, usa) were added to opti-mem i to a final volume of 200 l and the mixture incubated at room temperature for 45 min. after incubation, the medium was removed from one well of the six-well plate, 800 l of opti-mem i added to the transfection mix, and this mixture added dropwise to the cells. 6 h later, the dna-transfection mixture was replaced by opti-mem i. 24 h after transfection, 1 ml of opti-mem i that contained 1 g/ml l-(tosylamido-2phenyl) ethyl chloromethyl ketone (tpck)-treated trypsin (worthington biochemicals, lakewood, nj, usa) was added to the cells. about 72 h after the addition of tpck-trypsin, the culture supernatants were harvested and clarified by low-speed centrifugation; we then injected 100 l of the clarified supernatant into the allantoic cavity of individual 10-day-old pathogen-free embryonated research grade eggs (charles river spafas, north franklin, ct, usa). ten 4-week-old chickens received intravenous injections of 0·1 ml diluted virus (dilution ratio, 1/10). we monitored chickens for signs of disease for 10 days using the intravenous pathogenicity index, approved by the office of international epizooites (oie). additionally, we took tracheal and cloacal swabs (in 1 ml of media) 3 days and 5 days after infection, and we did assays for the presence of virus by injection of 0·1 ml into all of three 10-day-old embryonated chicken eggs. haemagglutination activity in the allantoic fluid of these eggs was assessed after incubation at 35°c for 2 days. pathogenicity testing in ferrets we tested pathogenicity of the vaccine in five young adult male ferrets (marshall's farms, north rose, ny, usa) aged 4-8 months (weight about 1·5 kg) that were shown by haemagglutination inhibition assays to be seronegative for currently circulating human influenza a viruses (h3n2, h1n1) and h5n1 viruses. we anaesthetised the ferrets with inhaled isoflurane, and they were then infected intranasally with 10 6 50% egg infectious dose (eid 50 )/ml of vaccine reassortant virus or wildtype virus. we monitored the ferrets once per day for signs of sneezing, inappetence, and inactivity, and we recorded rectal temperatures and bodyweights. 3, 5, and 7 days after infection, the ferrets were anaesthetised with ketamine (25 mg/kg), and we collected nasal washes using 1 ml of sterile phosphatebuffered saline (pbs) containing antibiotics. we measured titres of virus in these washes with eid 50 assays. to further assess the pathogenicity of the viruses, we collected tissue samples from lungs, brain, olfactory bulb, spleen, and intestine for virus isolation and histopathological analysis at the time of death or in the case of three ferrets, after euthanasia at day 3 after infection. the tissues were fixed in 10% neutral buffer formalin, processed and embedded in paraffin, sectioned at 5 g, stained with haematoxylin and eosin and examined by light microscopy in a blinded fashion. to test the stability of the vaccine virus on propagation, we made 16 consecutive passages of the virus in embryonated chicken eggs. a 10 -4 dilution of the virus was made in pbs, and 0·1 ml of the solution was injected into the allantoic cavities of all of four 10-day-old embryonated chicken eggs. eggs were incubated at 35ºc for 1·5-2 days. after incubation, each egg was candled to determine embryo viability before chilling at 4ºc. we harvested 2 ml of allantoic fluid from each egg harvested, and samples were pooled together, tested for haemagglutination activity, and then reinjected into another four eggs. the sponsor had no role in study design, in the collection, analysis, and interpretation of data, in the writing of the report or decision to submit this manuscript for publication. the first challenge we faced in producing a vaccine against a/hong kong/213/03 (h5n1) was to attenuate the virus in preparation for mass production. previous experiences have shown that removal of the basic aminoacids at the haemagglutinin cleavage site substantially attenuates pathogenic influenza viruses. [15] [16] [17] using a pcr-based mutagenesis approach, we replaced the cleavage site encoded by the haemagglutinin gene of a/hong kong/213/03 (h5n1) with that of the avirulent a/teal/hong kong/w312/97 (h6n1) (figure 1); this modified haemagglutinin gene and the neuraminidase gene of a/hong kong/213/03 (h5n1) were cloned individually into the vector phw2000. 11 the two resulting plasmids and the six plasmids encoding the remaining proteins of pr8 13 were transfected into whoapproved vero cells under gmp conditions to rescue the vaccine seed virus, ⌬213/pr8. 36-48 h after transfection, isolated areas of cytopathic effect could be seen on the vero monolayers. although addition of further 1 g aliquots of tpck-treated trypsin every 24 h led to a proportional increase in the cytopathic effect, it was not required for successful virus rescue. the candidate vaccine strain grew to high titres on subsequent amplification in eggs (haemagglutination titres of 1024-2048) and did not cause embryo death. the vaccine seed virus was unable to form plaques on madin-darby canine kidney (mdck) cells in the absence of trypsin, a trait consistent with that of influenza viruses that lack the polybasic cleavage site, and was antigenically indistinguishable from the parental h5n1 virus in haemagglutination inhibition assays. the rescued virus was fully sequenced and was identical to the plasmids used in its creation. to assess the pathogenicity of the h5n1 vaccine seed virus, we compared the properties of this virus with those of the wildtype a/hong kong/213/03 (h5n1) in ferrets and in chickens. by stark contrast with the wildtype virus, which was lethal to all chickens within 48 h of infection, intravenous administration of a 1/10 dilution of ⌬213/pr8 did not result in any signs of infection in chickens, and we were unable to detect any virus in swabs of cloacae or tracheae from inoculated birds. compared with a/hong kong/213/03 (h5n1), ⌬213/pr8 was attenuated in ferrets that had been inoculated intranasally with 10 6 eid 50 of virus. ferrets infected with a/hong kong/213/03 had inappetence and weight loss (figure 2), with one infected animal dying 6 days after infection and a second killed 10 days after infection because of hind-limb paralysis. infection in these animals was characterised by viral shedding until 7 days after infection and replication of virus in the lower respiratory tract and olfactory bulb (as determined by virus isolation). in the a/hong kong/213/03 infected animals, there was a mild mononuclear cell infiltrate in the meninges and tracheal submucosal mucous glands and an extensive bronchopneumonia. the pneumatic infiltrate progressed in severity from the bronchi to the pleura. the bronchi and bronchioles contained sloughed necrotic epithelial cells, numerous mononuclear cells, and a few neutrophils. the alveoli were consolidated with inflammatory cells and fibrin (figure 3). by contrast, those ferrets infected with ⌬213/pr8 did not lose weight (figure 2) and seemed to remain healthy during the study (14 days) ( figure 3) . virus was detected in the nasal washes of these animals at 5 days but not 7 days after infection, and virus was recovered from the upper respiratory tract only. by light microscopy, the meninges and trachea of the ⌬213/pr8 infected ferrets did not have an inflammatory infiltrate and only a few neutrophils were noted occasionally in pulmonary bronchi. our results clearly show that ⌬213/pr8 was attenuated. in view of our findings, this virus can be safely handled with standard precautions in bsl2 containment facilities. because the mechanisms and requirements for the accumulation of basic aminoacids at the haemagglutinin cleavage site are not entirely understood, we wanted to confirm that the altered cleavage site remained stable on multiple passages in embryonated chicken eggs. such passaging in eggs would occur in transition and amplification of the reference virus to vaccine stock. the rescued virus was stable on continued serial passage in embryonated eggs, and we did not detect any change in nucleotide sequence of the haemagglutinin cleavage site after 16 passages. there was no evidence of changing pathogenicity of the virus and we noted only one dead embryo at passage 15. no haemagglutination activity was evident in this egg and no embryo death was seen in passage 16, which strongly suggests that the death was not related to virus replication. haemagglutination titres at each passage ranged from 512 to 2048 with no apparent trend of increasing or decreasing titres in subsequent passages. the rapid response in terms of potential vaccine reference virus production to the 2003 h5n1 outbreak differs strikingly from the response to the 1997 episode. this difference is attributable to the new scientific technology available in 2003 and, just as importantly, to the infrastructure for virus surveillance in hong kong developed since 1997. the first case of h5n1 influenza in hong kong was in may, 1997; yet several months elapsed before this virus was finally characterised as an h5n1 virus. in 2003, the causative agent was identified only hours after admission of the patients to the hospital. the increased awareness, surveillance, and availability of reagents to identify influenza viruses of all subtypes bode well for the rapid identification of viruses that arise from future interspecies transfer events and for the coordination of international vaccine development by who. the timely distribution of candidate viruses is a very important step in the development of vaccines for pandemic emergencies. despite the heightened security and documentation requirements for shipping and receiving potential bioterrorism agents, the h5n1 and sars outbreaks have shown that in true emergencies, global distribution is feasible. although it is pertinent to prepare for future pandemics by stockpiling potential vaccine strains, the h5n1 situation in 2003-and the ongoing h5n1 outbreaks throughout asia in 2004 (http://www.who.int)-have highlighted the fact that some of the focus of pandemic planning must go into the implementation of technology to rapidly produce vaccines from field isolates. although viruses similar to a/hong kong/213/03 (h5n1) had been circulating in bird populations, these viruses were antigenically distinct, despite high genetic similarities (guan y and peiris js, unpublished data). that the aminoacid differences are on the globular head of haemagglutinin and seem to be responsible for much of the antigenic difference means that even a vaccine previously prepared from genetically similar precursor viruses might not provide adequate protection. we may well be faced with potential pandemic situations in the future and the rapid production of a matched vaccine will be needed-a point again highlighted by h5n1 outbreaks in 2004. although the reference virus described in this report was prepared from a virus isolated in a similar geographic region and only a year earlier, it shares only limited antigenic cross-reactivity to the 2004 h5n1 viruses. hyperimmune sheep serum samples produced against the purified haemagglutinin of ⌬213/pr8 has at least a six-fold reduced haemagglutination inhibitory activity against a/vietnam/1203/04 as compared with a/hong kong/213/03. as our findings show, we have the technical capabilities to respond rapidly to outbreaks with a safe and stable reference virus, but there is still much to be accomplished before such viruses can be fully used in pandemic and interpandemic influenza vaccine production. the use of reverse genetics introduces a number of new processes into influenza vaccine manufacture that are not encountered with standard reassortment methods. one of the most obvious is the need for cultured cells. although both vero 18 and mdck 19, 20 cells are in development as substrates for the growth of influenza vaccine, there are additional requirements for the use of cells in reverse genetics. unfortunately, the number of suitable cell lines is very small. in addition to the regulatory requirements, the choice of cell is also limited by the technology. the plasmid based reverse-genetics systems 10 necessitates the use of cells from primate origin. the vero cell line is probably the only option currently able to meet both regulatory and technical demands. we have shown that vero cells can be used to successfully rescue h1n1, h3n2, h6n1, and h9n2 viruses on the pr8 backbone using the 8-plasmid system. 21 others have demonstrated the suitability of vero cells for alternative influenza virus reverse-genetics systems. 10 although cultures of vero cells are easily obtained, only cells from fully tested and licensed cell banks are likely to be acceptable for vaccine manufacture. this issue must be acknowledged and access to such cells must be incorporated as part of future pandemic plans. that future threats of influenza pandemics will be addressed by the use of the technology described in this report seems inevitable. despite the presence of low pathogenic surrogate strains, the recent human death from influenza-like illness caused by highly pathogenic h7n7 virus in the netherlands 22 reinforces the fact that future outbreaks will probably occur in which this reversegenetics technology provides the logical-and, possibly, the only-way to respond rapidly and effectively. although our response to the outbreak of h5n1 influenza in 2003 has shown that current scientific capabilities are sufficient to respond to the threat, there are still legal and infrastructural barriers to be overcome. 23 these barriers include licensing and intellectual property issues surrounding what is, essentially, a genetically modified organism. yet, these difficulties are not insurmountable and pandemic scares such as the 2003 and ongoing 2004 h5n1 outbreaks are forcing commercial and regulatory parties to address these issues with some urgency. with the development of the 2003 h5n1 vaccine reference virus, and ongoing attempts to create the same for the 2004 virus, the challenge in responding to a threat of an influenza pandemic must now be supported by the largescale manufacture of the vaccine and by clinical trials of a new vaccine manipulated by reverse genetics. r j webby, d r perez, j s coleman, j h knight, e i tuomanen, r g webster designed the study; r j webby did much of the construction of the vaccine seed virus; d r perez developed and constructed plasmid templates; y guan and j s peiris characterised and isolated the initial h5n1 virus; j e rehg participated in the design and analysis of animal safety testing of the candidate h5n1 vaccine seed virus; e a govorkova participated in the safety testing of the candidate h5n1 vaccine seed virus; l r mcclain-moss participated in the preparation of gmp documentation of the process and was involved in the reconstitution of the vaccine seed virus. a pandemic warning? characterization of an avian influenza a (h5n1) virus isolated from a child with a fatal respiratory illness characterization of avian h5n1 influenza viruses from poultry in hong kong interspecies transmission of influenza viruses: h5n1 virus and a hong kong sar perspective future influenza vaccines and the use of genetic recombinants developing vaccines against pandemic influenza the structure of the hemagglutinin, a determinant for the pathogenicity of influenza viruses proteolytic cleavage of influenza virus hemagglutinins: primary structure of the connecting peptide between ha1 and ha2 determines proteolytic cleavability and pathogenicity of avian influenza viruses molecular analyses of the hemagglutinin genes of h5 influenza viruses: origin of a virulent turkey strain rescue of influenza a virus from recombinant dna a dna transfection system for generation of influenza a virus from eight plasmids generation of influenza a viruses entirely from cloned cdnas eight-plasmid system for rapid generation of influenza virus vaccines plasmid-only rescue of influenza a virus vaccine candidates evaluation of a genetically modified reassortant h5n1 influenza a virus vaccine candidate generated by plasmid-based reverse genetics recombinant influenza a virus vaccines for the pathogenic human a/hong kong/97 (h5n1) viruses preparation of a standardized, efficacious agricultural h5n3 vaccine by reverse genetics development of a vero cellderived influenza whole virus vaccine influvac: a safe madin darby canine kidney (mdck) cell culturebased influenza vaccine safety and immunogenicity of a trivalent, inactivated, mammalian cell culture-derived influenza vaccine in healthy adults, seniors, and children generation of high-yielding influenza a viruses in african green monkey kidney (vero) cells by reverse genetics avian influenza a virus (h7n7) associated with human conjunctivitis and a fatal case of acute respiratory distress syndrome pandemic influenza and the global vaccine supply we thank todd hatchette, katherine sturm-ramirez, and scott krauss for expert advice; ashley baker, christie johnson, yolanda sims, patrick seiler, jennifer humberd, and kelly jones for excellent technical assistance; julia hurwitz for access to the vero-cell banks. editorial assistance was provided by julia cay jones. these studies were supported by grant ai95357 from the national institute of allergy and infectious disease, by cancer center support (core) grant ca21765 from the national institutes of health, and by the american lebanese syrian associated charities (alsac). none declared. the corresponding author has had full access to all the data in the study and has had the final responsibility for the decision to submit this manuscript for publication. key: cord-307307-b5yl88mh authors: lau, joseph tf; griffiths, sian; choi, kai chow; tsui, hi yi title: avoidance behaviors and negative psychological responses in the general population in the initial stage of the h1n1 pandemic in hong kong date: 2010-05-28 journal: bmc infect dis doi: 10.1186/1471-2334-10-139 sha: doc_id: 307307 cord_uid: b5yl88mh background: during the sars pandemic in hong kong, panic and worry were prevalent in the community and the general public avoided staying in public areas. such avoidance behaviors could greatly impact daily routines of the community and the local economy. this study examined the prevalence of the avoidance behaviors (i.e. avoiding going out, visiting crowded places and visiting hospitals) and negative psychological responses of the general population in hong kong at the initial stage of the h1n1 epidemic. methods: a sample of 999 respondents was recruited in a population-based survey. using random telephone numbers, respondents completed a structured questionnaire by telephone interviews at the 'pre-community spread phase' of the h1n1 epidemic in hong kong. results: this study found that 76.5% of the respondents currently avoided going out or visiting crowded places or hospitals, whilst 15% felt much worried about contracting h1n1 and 6% showed signs of emotional distress. females, older respondents, those having unconfirmed beliefs about modes of transmissions, and those feeling worried and emotionally distressed due to h1n1 outbreak were more likely than others to adopt some avoidance behaviors. those who perceived high severity and susceptibility of getting h1n1 and doubted the adequacy of governmental preparedness were more likely than others to feel emotionally distressed. conclusions: the prevalence of avoidance behaviors was very high. cognitions, including unconfirmed beliefs about modes of transmission, perceived severity and susceptibility were associated with some of the avoidance behaviors and emotional distress variables. public health education should therefore provide clear messages to rectify relevant perceptions. the who raised the influenza alert level to the highest pandemic 'phase 6' level on june 11, 2009 . as of june 19, 2009 , 44,287 confirmed h1n1 cases were detected in 88 countries, territories and areas and 180 deaths had been reported [1] ; the number of death increased to 15,292 as of february 7, 2010. a preliminary study showed that the new h1n1 virus is more infectious than seasonal influenza [2] . in hong kong, the first confirmed case, a traveler from mexico, was reported on may 1, 2009, leading to the closure and isolation of the metropark hotel and to the quarantining of 350 guests and staff from may l to may 8, 2009 . during the h1n1 outbreak, the hong kong hospital authority raised the alert level to the highest 'emergency response level'. the government maintained its confinement strategy till 12 june, 2009, when it became obvious that cases were spread in the community, and the response thus became mitigation. as of june 27, 2009 , there are 629 confirmed cases in hong kong and no h1n1-related death was recorded and as of february 10, 2010, there were 67 h1n1-related deaths. the lessons learned from the sars experience in hong kong [3] and other countries demonstrated the importance of understanding community responses [4, 5] . surveillance of community responses at the initial phase of an emerging epidemic is useful to inform both policy makers and the public about the state of preparedness. in hong kong, at the time of the sars epidemic, the perceptions and behaviors changed dramatically during the course of the outbreak [4, [6] [7] [8] . panic and worry increased and became widespread during the epidemic and remained high in the post-sars period [4, 9] . at the height of the epidemic, the general public avoided going out, traveling to other countries and gathering for social activities [4] . scholars estimated that a loss of hk$15 billion in spending on goods and services in hong kong domestic economy was attributable to the sars epidemic [10] . similar studies were conducted to investigate community responsiveness to the threat of human-to-human h5n1 avian flu transmissions in hong kong [11] [12] [13] [14] . previous studies on human avian flu or sars in different countries also suggested that widespread distress occurred in affected areas and nationwide populations even at the early phase of the outbreak, causing serious social and economic disruption [15, 16] . a study was conducted to investigate community behavioral and emotional responses at the very initial phase after the identification of the first few h1n1 cases in hong kong [17] . a few other studies have investigated community's attitudinal and behavioral responses toward the early phase of the h1n1 pandemic in countries including the u. k. [18] , australia [19] , malaysia and europe [20] , france [21] , japan [22] . avoidance behaviors have been prevalent in a number of countries or cities, such as hong kong and malaysia but not in the u. k. mild emotional distress was observed in hong kong but the public in japan perceived overwhelming fear. the majority of the respondents in the hong kong study washed their hands more often than usual, but only around 30% of those in the u. k. did the same. variations in perceived susceptibility and perceived efficacy over preventive measures have also been reported in these studies. therefore, community responses to the h1n1 pandemic are likely to be country-specific, possibly determined by previous experiences of epidemics such as sars, the health system, risk communication patterns and even culture [22] . this study investigated whether the general population in hong kong avoided visiting different places (going out, visiting crowded places and visiting hospitals) and assessed some negative psychological responses to h1n1, including whether people were much worried about contracting h1n1 and their level of emotional distress (panicking, depression or emotional disturbance) due to h1n1. factors in association with the outcome variables on avoidance behaviors and negative psychological responses were investigated, including variables such as socio-demographic characteristics, confirmed knowledge and unconfirmed beliefs about modes of h1n1 transmission, evaluation towards governmental preparedness/ performance, perceived availability of treatment, and risk perception (perceived severity and susceptibility related to h1n1). the study period of this report covers almost the entire pre-pandemic and pre-community outbreak phase of the h1n1 epidemic in hong kong. the study population comprised all chinese adults who were 18 years old or above in hong kong. anonymous telephone interviews were conducted by well-trained interviewers, using an identical structured questionnaire, from may 7 to may 9 (day 7-9, n = 550), from may 14 to may 17 (day 14-17, n = 201), and from june 4 to june 6 (day 34-36, n = 248), 2009. there were respectively 1, 2 and 30 imported cases (and no community non-imported cases) detected at the beginning date of these 3 surveys. preliminary data from the survey conducted from may 7 to may 9 have previously been reported [17] . the first local community-infected case with an unknown source of infection was reported on june 11, 2009 , so that the surveys (may 7 to june 6, 2009) therefore covered almost the entire 'pre-community outbreak phase' (may 1 to june 10, 2009) of the local epidemic. random telephone numbers were selected from an up-to-date telephone directory and the last two digits of the selected telephone number were randomized to include some unlisted telephone numbers; over 95% of the households in hong kong have a fix-line telephone at home [23] . the interviews were conducted from 6:30 to 10 pm to avoid overrepresenting the non-working population. one member was selected by the last-birthday-rule from each of the contacted households. at least 3 phone calls were made at different hours and days before an unanswered number is considered invalid. verbal consent was sought and the study was approved by the ethics committee of the chinese university of hong kong. a total of 2,583 phone numbers were made and being answered by someone (2,906 calls were unanswered with at least 3 attempts made), out of which 1,621 were eligible households were identified and being invited to join the study. of these 1,621 eligible respondents, 95 (5.9%) could not be contacted after 3 attempts, 525 (32.4%) refused to join or withdrew from the study, and 999 (61.6%) participated in the study. previously, preliminary data from the may 7 to may 9 survey have been reported elsewhere [17] . dependent variables included current avoidance behaviors: 1) 'avoided going out', 2) 'avoided visiting crowded places' and 3) 'avoided visiting hospitals', and exhibition of negative psychological responses: 1) worried very much that oneself or one's family would contract h1n1 and 2) emotional distress ('panicking very much' or 'felt much depressed' or 'felt much emotionally disturbed' due to h1n1). socio-demographic characteristics were recorded. correct knowledge and unconfirmed beliefs about modes of h1n1 transmission were assessed. respondents were asked about perceived availability of treatment. risk perception questions include those related to perceived severity of h1n1 (fatality and severe irreversible bodily damages), the relative chance for hong kong to have a large-scale h1n1 outbreak as compared to other countries, and perceived susceptibility (oneself, one' family and the general public). questions were also asked to evaluate relevant actions taken by the government (6 items), their ability to control the epidemic (2 items), as well as the health system's preparedness toward the h1n1 pandemic (3 items: adequacy of medicine, vaccines and personal protection equipments). these items are listed in tables 1, 2 and 3. they were modified from the questionnaires which had been used in some avian flu studies [11] [12] [13] [14] and sars studies [4, 9, 24, 25] . they have also been used in the published baseline h1n1 study [17] . associations between the independent variables and the dependent variables (avoidance behaviors and negative psychological responses) were assessed by using univariate odds ratios (or) and their respective 95% confidence intervals (ci). variables that were significant in the univariate analysis were used as candidates for fitting logistic regression models. multivariate or and their 95% ci were reported. spss 16.0 was used for the data analyses with p < .05 as the level of statistical significance. of all respondents (n = 999), 43.4% were males; 54.8% were of age 40 years old or above; 35.1% received some post-secondary education; 65% were currently married or were cohabitating with someone; 56% were currently employed full time; and 1.9% were health care workers. the age and gender distributions did not vary across the 3 surveys and were similar to those of the census data (footnote of table 1 ). of all respondents, 61.8% held at least one of the unconfirmed beliefs that h1n1 could be transmitted through airborne spread across long distance (e.g. from a building to another building; 36.7%), via water sources such as reservoirs (35.7%), via insect bites (22.9%) or via eating well cooked pork (41.6%). respectively, 97.5%, 74.2% and 77.8% of the respondents correctly knew that h1n1 is transmittable via droplets, touching the body of infected person or contaminated objects; about 60.3% were correct in all these three items ( table 2) . around 30-40% of all respondents believed that the local health system currently did not have enough medication (36.2%), vaccine (41.1%) or personal protection equipments (30.2%) to deal with the h1n1 epidemic, with 52.6% holding at least one of such 3 beliefs ( table 2 ). the majority (92.3%) of the respondents was confident in the public's or governmental ability to control the epidemic, i.e., either agreeing with the statements 'hong kong would be able to control the h1n1 epidemic' (83.6%) or with the statement that the 'hong kong government would be able to control a large-scale h1n1 outbreak' (79.5%). the majority (89.3%) of the respondents gave a passing score >5 for the governmental performance in dealing with h1n1 (range = 0 to 10, with 5 as the passing mark; table 2 ). about 39% (38.9%) of the respondents believed that there was so far no effective drug available to treat h1n1 ( table 2) . around 20% of the respondents believed that h1n1 is highly fatal (20.6%) or could cause severe irreversible bodily damages (18.9%; table 2 ). respectively, 7.1% and 47.6% believed that hong kong has a higher or a lower chance of having a large scale h1n1 outbreak in the future year, as compared to other countries. close to 10% of the respondents perceived a high or very high chance for himself/herself (8.6%), his/her family members (8.7%) or the general public (12.5%) to contract h1n1 in the next year ( table 2) . respectively 54.9%, 44.0% and 63.4% of the respondents currently avoided going to crowded places, avoided going out or avoided visiting hospitals. around 15% (15.8%) of the respondents were currently much worried that either they or their family members would contract h1n1; 6.0% showed signs of emotional distress (i.e. panicking very much or felt much depressed or were very much emotionally disturbed due to h1n1). females, older respondents, those with >= 1 unconfirmed beliefs about modes of h1n1 transmission, those who knew that h1n1 could be transmitted 'via droplets', 'bodily contact with infected person' or 'touching contaminated objects', those who were very worried that either they or their family members would contract h1n1, those expressing emotional distress (in panic or feeling very depressed or being highly emotionally disturbed due to h1n1) were more likely than others to avoid visiting crowded places (multivariate or = 1.42 to 3.90, p < .05; table 4 ). females, older respondents, those with >= 1 unconfirmed beliefs about modes of h1n1 transmission, those who knew that h1n1 could be transmitted 'via droplets', 'bodily contact with infected person' or 'touching contaminated objects', those who believed that h1n1 would cause severe irreversible bodily damage, and those expressing emotional distress (in panic or feeling very depressed or being highly emotionally disturbed due to h1n1) were more likely than others to avoid going out (multivariate or = 1.42 to 3.66, p < .05). those who were full-time employed were less likely than others to avoid going out (multivariate or = 0.72, p < .05; table 4 ). the respondent 8.6% family members 8.7% the general public 12.5% * governmental performance was assessed by 6 items: timeliness of measures taken; effectiveness of implemented measures; clear explanations made to citizens; adequacy of implemented measures; coordination across governmental departments; overall performance of the government. (score range = 0 to 10, with 5 as the passing mark). an average was calculated for the 6 item scores. # less than 2% missing cases exist for the listed variables. (score range = 0 to 10, with 5 as the passing mark). an average score was calculated for the 6 item scores. variables that were not significantly associated with any of the dependent variables in the univariate analysis were not tabulated. these variables include being current health care practitioner, perceived availability of drugs, perceived high chances of contracting the disease for himself/herself, his/her family members and the general public. respondents who were married/cohabited, those with >= 1 unconfirmed beliefs about modes of h1n1 transmission, those who believed that h1n1 would cause severe irreversible bodily damage, and those who were very worried that either they or their family members would contract h1n1 were more likely than others to avoid visiting hospitals (multivariate or = 1.47 to 1.81, p < .05; table 4 ). the results of the multivariate analysis showed that those who believed h1n1 would cause severe irreversible bodily damage and those who believed that they themselves had a high chance of contracting h1n1 were more likely than others to be much worried that either they or their family members would contract h1n1 (multivariate or = 1.95 and 3.31 respectively, p < .05; table 5 ). those who believed either that the general public and/or the local government would be able to control a large scale local h1n1 outbreak were less likely to show the worry (multivariate or = 0.51). in the multivariate analysis, females, those who doubted about adequacy of governmental preparedness (inadequate vaccine or medication or personal protection equipments in hong kong), those who associated h1n1 with a high fatality, and those who believed that their family members had a high chance of contracting h1n1 were more likely than others to indicate emotional distress (panicking or much depressed or much emotionally disturbed) due to h1n1. the significant multivariate or ranged from 1.94 to 3.68 (p < .05; table 5 ). around 77% of the respondents showed some avoidance behaviors. the studies covered the entire early 'pre-community outbreak phase' of the h1n1 epidemic in hong kong during which all confirmed cases were imported. during the study period, the local government had not given any public health advice about avoiding going to different places, though a previous analysis of our may 7 to may 9 data showed that 31.6% of the public misconceived that such an advice was given [17] . avoidance of visiting hospital may be due to the fear of getting infected in hospitals, which was prominent during the sars period [9] . the government only started advising people to avoid crowded places at the 'community outbreak phase' of the epidemic. there seemed to be no serious immediate public health threat for going out or visiting different places. such avoidance behaviors were associated with negative psychological responses; emotional elements may therefore be strongly involved in making the decisions. experience from sars showed that such avoidance behaviors among large numbers in the popula-tion potentially damages the economy and disrupts daily lives. about half of the respondents believed that hong kong has a lower chance of having an h1n1 outbreak as compared to other countries, whilst only less than 10% held the opposite belief. there were signs of underestimating the risk of having a community outbreak in hong kong [17] . the shift into the pandemic phase as announced by the who and the explosion of non-imported community cases in hong kong (629 as of june 27, 2009) may change the picture completely. the direction of change is however uncertain. a few international studies also documented strong levels of anticipated anxiety and avoidance behaviors at the early phase of human avian flu outbreaks or pandemic influenza [15, [26] [27] [28] . the impact of pandemics and unknown emerging infections has not been widely studied. avoidance behaviors and emotional distress may have been under-emphasized in the preparedness plans. it is seen that females, older people and those who were not full-time employed were more likely than others to show avoidance behaviors or signs of emotional distress. the results are consistent with those reported during the sars period [9] . a recent study exploring people's emotional and behavioral responses to an avian flu outbreak also showed that females and older people were, respectively, more likely to express negative emotional responses and exhibit avoidance behaviors (e.g., avoiding leaving their residence, avoiding crowds and avoiding visiting hospitals) in response to avian flu [26] . attention should therefore be given to avoidance behaviors and psychological needs of these subpopulations at times of a pandemic. perceptions still count in this context. there were substantial unconfirmed beliefs about the mode of h1n1 transmission (61.8% had at least one unconfirmed belief ). around 1/4 of the respondents did not know that the virus could be spread by touching contaminated objects. the aforementioned unconfirmed beliefs about transmission mode were significantly associated with avoidance behaviors. unconfirmed beliefs about modes of transmission were also documented in h5n1 studies [12] , suggesting that similar unconfirmed beliefs exist in general for emerging respiratory infectious diseases. rectification of misconceptions is important -and may decrease and reduce unwarranted anxiety. around 20% of the respondents believed that h1n1 would result in high fatality or severe irreversible bodily damages. such beliefs may be affected by the sars experience. perceived high fatality was associated with emotional distress (e.g. panic) due to h1n1 and perceived severe irreversible bodily damage was associated with 3 of the 5 outcome variables on avoidance behaviors and negative psychological responses. up-to-date information about the clinical properties of h1n1 should be disseminated to the public in layman terms. the actual fatality associated with h1n1, both local and international, remains low. the cost of assurance by hong kong government is however, high -with early summer closure of all primary schools and kindergarten and a number of secondary schools, 10 billion hong kong dollars being spent (1.2 billion us$) to purchase h1n1 vaccines and reorganization of the health services to accommodate escalating infection figures are not insubstantial. tourism may be adversely affected. a substantial proportion of the public may be overestimating its fatality and physical damages. since public understanding of risk and of these mitigation measures will help to reduce unnecessary concern and changes in lifestyle amongst the population, public education is important. as expected, perceived personal/family susceptibility for contracting h1n1 was associated with negative psychological responses due to h1n1. the association between perceived personal/family susceptibility and avoiding going out was non-significant. the results suggest that the public did not avoid going out because of feeling susceptible. avoidance behaviors may involve an irrational element. it is speculated that the sars experience of avoiding going to different places [29] might have a spill-over effect. the general public evaluated the government highly in the performance and ability to control the pandemic. they however, showed reservations about the availability of medicine and vaccine and protective equipments, possibly because h1n1 was a new disease and it was not certain whether effective medicine, vaccine and equipments were then available. the positive evaluations of governmental performance and perceived ability for hong kong or the government to control the h1n1 outbreak were significantly associated with the outcome variables in most of the univariate analyses. nonetheless, most of these associations were statistically non-significant in the multivariate analysis. the associations between such variables and the outcome variables (avoidance behaviors and negative psychological responses) were hence mediated by other variables, such as worry about contracting h1n1 or perceived susceptibility. these potential mediators were multivariately associated with either the avoidance variables or the negative psychological response variables. the study has some limitations. first, this was a crosssectional baseline study. second, the response rate was comparable to those of other relevant published studies but some non-responder bias may still exist [9, 14, 30] . some telephone numbers are unlisted and we randomized the last two digits to cover some of the unlisted numbers. moreover, the gender and age distributions were comparable to those of the census population data. third, results were self-reported and social desirability bias may exist. the study was however anonymous. fourth, hong kong went through unique sars experience, the results may not be comparable with those of other countries. fifth, the measures on negative psychological responses were based on those used in previous studies, rather than derived from some validated scales. finally, the study was not intended to track changes within the short study period of a month -interactions between time and various independent variables were not explored. similar data obtained from other countries are becoming available and can be compared with ours. in sum, the results of this study documented that a noticeable proportion of the public exhibited avoidance behaviors that had not been advised by the government and negative psychological responses at the early 'precommunity outbreak phase' of the h1n1 outbreak. with the relatively mild nature of the h1n1, and with all the hygiene and public health measures continually reemphasized, an open debate on whether the public should avoid going out during the h1n1 outbreak should be encouraged. it would facilitate appropriate responses and daily lives of people in hong kong, one of the most densely populated cities in the world, remain undisrupted. the study is part of an ongoing surveillance program, which is in place in hong kong. hong kong is now in the pandemic and 'community outbreak phase'. the public needs to be better informed about the modes of transmission and clinical consequences of the disease to make rational behavioral choices. early detection of mental health problems and primary preventions are warranted. comparisons with other parts of the world, such as mainland china, would be very informative. this study provides a better understanding of the factors associated with negative psychological responses due to h1n1, which would give useful insights to designing primary prevention of mental health distress at the initial phase of this and outbreaks of other emerging respiratory infectious diseases. the opinions expressed by authors contributing to this journal do not necessarily reflect the opinions of the centre for health behaviours research or the institutions with which the authors are affiliated. world health organization: influenza a(h1n1) -update 51 who rapid pandemic assessment collaboration: pandemic potential of a strain of influenza a (h1n1): early findings severe acute respiratory syndrome(sars) expert committee: sars in hong kong: from experience to action monitoring community responses to the sars epidemic in hong kong: from day 10 to day 62 a tale of two cities: community psychobehavioral surveillance and related impact on outbreak control in hong kong and singapore during the severe acute respiratory syndrome epidemic the impact of community psychological responses on outbreak control for severe acute respiratory syndrome in hong kong factors influencing the wearing of facemasks to prevent the severe acute respiratory syndrome among adult chinese in hong kong longitudinal assessment of community psychobehavioral responses during and after the 2003 outbreak of severe acute respiratory syndrome in hong kong sars-related perceptions in hong kong. emerging infectious diseases economic impact of sars: the case of hong kong a serial of 6 surveillance surveys of anticipated behavioral and psychological responses to avian influenza pandemic in humans among the hong kong general public (sf-04). oral presentation at the 40th apacph annual conference perceptions about status and modes of h5n1 transmission and associations with immediate behavioral responses in the hong kong general population anticipated and current preventive behaviors in response to an anticipated human-to-human h5n1 epidemic in the hong kong chinese general population perceptions related to human avian influenza and their associations with anticipated psychological and behavioral responses at the onset of outbreak in the hong kong chinese general population differences in public emotions, interest, sense of knowledge and compliance between the affected area and the nationwide general population during the first phase of a bird flu outbreak in israel crisis prevention and management during sars outbreak widespread public misconception in the early phase of the h1n1 influenza epidemic public perceptions, anxiety, and behaviour change in relation to the swine flu outbreak: cross sectional telephone survey the community's attitude towards swine flu and pandemic influenza swine flu") lay perceptions of the pandemic influenza threat responses to the outbreak of novel influenza a (h1n1) in japan: risk communication and shimaguni konjo a population-based study of depression and three kinds of frequent pain conditions and depression in hong kong impacts of sars on health-seeking behaviors in general population in hong kong prevalence and factors of sexual problems in chinese males and females having sex with the same-sex partner in hong kong: a population-based study predicting the anticipated emotional and behavioral responses to an avian flu outbreak pandemic influenza in australia: using telephone surveys to measure perceptions of threat and willingness to comply realities and enigmas of human viral influenza: pathogenesis, epidemiology and control sars preventive and risk behaviours of hong kong air travellers an outbreak of the severe acute respiratory syndrome: predictors of health behaviors and effect of community prevention measures in hong kong the authors would like to thank all participants of this study. thanks are extended to mr. nelson yeung for his help in the early drafts of the manuscript, mr. tony yung and mr. johnson lau for their assistance in the preparation of the questionnaire, ms. mw chan, mr. mason lau, and ms. cheri tong for coordination of the telephone survey and all colleagues who served as telephone interviewers of this study. the study was supported by the research fund for the control of infectious diseases from the food and health bureau. the authors declare that they have no competing interests. jtfl designed and oversaw the study and wrote the manuscript. sg and hyt proposed suggestions to improve study and revised the manuscript intellectually. kcc performed the data analysis. all authors read and approved the manuscript. the pre-publication history for this paper can be accessed here: key: cord-316860-60mrbgwg authors: keck, frédéric title: birds as sentinels for pandemic influenza date: 2014-05-28 journal: biosocieties doi: 10.1057/biosoc.2014.9 sha: doc_id: 316860 cord_uid: 60mrbgwg nan how can animals send signals of future threats to humans? this question has always fascinated humans and anthropologists, but it gains a new meaning in the contemporary world of biosecurity where health issues are considered as security priorities and coming epidemics are the objects of anticipatory knowledge. understanding how non-humans are enroled in anticipatory knowledge and how this transforms their relations with humans is a key concern for social scientists. a microbiological article that is of particular interest to this body of scholarship was written in 2003 by shortridge, peiris and guan: "the next influenza pandemic: lessons from hong kong". published in the journal of applied microbiology, it addresses a broader audience and draws lessons from 7 years of mobilisation against influenza as a public health concern. when microbiologists learn from history, as they have done for aids (dodier, 2003) , they write in the language of viruses. because of the high mutation rate of the flu virus, new forms of the disease constantly emerge and can become pandemic, as was the case in hong kong in 1968. the question raised by shortridge et al is which flu virus was the candidate for the next pandemic and how it could be detected before spreading widely. for a 'global clinic' (king, 2002) it is necessary to know what candidate vaccines must be prepared for a future outbreak. however, we have learned from hong kong that stockpiling vaccines is not the only way to prepare for a pandemic. shortridge et al's article draws lessons not only from history but also from geography. being a british colony in 1968, hong kong was the place where the last pandemic flu virus was effectively detected, but it may have emerged in southern china, where little information was available at that time. trained in australia, kennedy shortridge joined the department of microbiology of hong kong university in 1972 to provide data on flu viruses to the world health organization. he proposed a hypothesis explaining the role of south china as an 'epicentre' of flu pandemics (shortridge and stuart-harris, 1982) . flu viruses mutate in waterfowl, particularly ducks, where they develop in the digestive tract without killing the animals. they are transmitted to domestic poultry and pigs, which serve as 'mixing vessels' between birds and humans. influenza is a zoonosis: a disease transmitted from animals with unpredictable effects on humans because of their lack of immunity. south china has a high concentration of waterfowl, poultry, pigs and humans, which speeds up the rate of mutations of flu viruses: it is an "avian influenza virus melting pot" (p. 72s). serving as a hub between east and west, hong kong is the place from where these new viruses are transmitted to the rest of the world. hence, shortridge's idea is that it should be possible to map flu viruses in their 'animal reservoir' to detect in advance those which will 'jump the species barriers' between birds, pigs and humans. but this raises a new question: how, among all the flu viruses that can be found in animals, to bet on the right 'candidate virus' that will actually cross the species barrier? if this question sounds 'speculative', notice that the only gambling activity allowed in hong kong is horse racing. this is where history comes back in. in 1997, a new flu virus emerged, killing 6 persons out of the 18 it infected. it also killed 5000 chickens in poultry farms, and it was estimated that 20 per cent of chickens in the markets had been infected. what was surprising about this virus was its high lethality and the fact that it had jumped directly from birds to humans since it was not found in pigs. this changed the scenario: it was not possible to make a vaccine for this new virus because it killed the chicken embryos used for conventional vaccines ("recombinant and genetically engineered vaccines are being explored", shortridge et al added). but it became possible to imagine a world where this new lethal virus would become pandemic and kill more humans than the 1918 'spanish flu'. it could spread either through humans (although its inter-human transmission had not been proved), through migratory birds (but can sick birds fly?) or through the poultry industry (a factor emphasised by the article). flu viruses are classified by their haemagglutinin (h) and neuraminidase (n) proteins, that allow them to enter and exit from cells. this new virus, called h5n1, was thus considered as the first candidate for a new pandemic. circulating in birds, h9n2 and h6n1 followed suit. ordering viruses by the range of their pandemicity was not based on probability of genetic mutation but on their actual capacity to jump the species barrier with catastrophic consequences. "it might be possible, for the first time, to have influenza pandemic preparedness at the baseline avian level", wrote shortridge et al (2003, p. 70 ): this idea is repeated several times in the article. it means that microbiologists can detect mutations at the species barrier and send out 'early warnings' on those that may become pandemic. the image of a fire is evoked when the authors describe the emergence of h5n1 as "smouldering": if pandemic viruses are detected early enough, they will be like a fire without a flame. this had powerful political consequences. in 1997, in the context of the handover of the british colony to the people's republic, the claim that birds coming from china could start a pandemic from hong kong stirred up tensions. shortridge et al noted: "the incident was the first issue the fledging special administrative region (sar) had to deal with since hong kong's reunification with china. in a sense, the sar felt vulnerable, acutely aware of its international responsibility and that it was being tested" (p. 76s). in this context, preparing for the pandemic took a military turn, characteristic of 'biosecurity interventions' (lakoff and collier, 2008) . on 29 december 1997, all the live poultry on the territoryaround 1.5 millionwere killed to eradicate the h5n1 virus from its animal reservoir (the term 'incident' may here appear as a euphemism). commenting on 'the controversial slaughter policy', the authors argue that "it is reasonable to believe that this intervention prevented an incipient pandemic progressing to an actual pandemic and thus a pandemic was averted" (p. 72s). the article thus mixes different registers of anticipatory knowledge: prevention, precaution and preparedness. shortridge et al attributed the idea that a pathogen is detected before it causes a disease to ancient epidemiological principles of prevention in chinese medicine. but the 1997 event was analysed as a failure of prevention: it "gave rise to a precautionary principle, essentially a watching brief of preparedness". in the absence of certainty on the h5n1 virus, it was necessary to eradicate it in its animal reservoir "as a preemptive measure" (p. 73s). if the pandemic had been averted and not prevented, it was certainly imminent: "each year brings us closer to the next pandemic" (p. 75s). the failure of prevention (building a vaccine for viruses before they become lethal) forced the hong kong government to use precautionary measures, that is, to kill all live poultry, and to strengthen its preparedness by closely monitoring virus mutations in animals. the question for shortridge et al was how hong kong could act as a 'sentinel post'a vocabulary derived from the militarynot only by gathering information on flu viruses on both sides of the human/animal divide, but also by intervening in a situation of uncertainty. if the public and the media, they argued, "could not cope with the uncertainty" (of viral mutations), they would understand public health measures by their impact on food. hence the stress on live poultry markets as a traditional practice that had a major impact on the risk of flu transmission, even if the virus was killed in the process of cooking. the spectre of a coming pandemic became credible to the public when related to the uncertainties of contact with live poultry. this relation between public health and food safety is one of the main drivers for building 'sentinel posts' for avian influenza. if a sentinel post is sensitive to emerging events at the human/animal interface, it can also overreact when betting on the wrong virus (keck and lakoff, 2013) . it is remarkable that the discussed article was published in 2003 just after the outbreak of severe acute respiratory syndrome (sars) in hong kong. the two coauthors of shortridge discovered the human coronavirus responsible for sars (peiris) and its animal origins in south china (guan). but the team initially lost two weeks as it tested for h5n1, which gives rise to the same symptoms as sars. sars strengthened the position of hong kong as a 'sentinel post' sensitive to diseases emerging from animals and spreading to the rest of the world, but it also showed its vulnerabilities: a biosecurity intervention is a bet on the human/animal interface and its potential outcomes. the article thus concludes: "given the genetic unpredictability of the influenza a viruses, there probably will be many influenza battles to be fought, some to lose some hopefully to win, in the foreseeable future" (p. 77s). the 'lessons from hong kong' were that the genetic knowledge accumulated on emerging viruses were not enough to face the uncertainties of epidemic outbreaks: hence the need of new relations between humans and animals as 'sentinel devices' where these uncertainties could be converted into early warning signals.t as an anthropologist of science, nature and culture bookend my reading and my thinking, from lévi-strauss to ortner and strathern, from haraway's naturecultures to latour's nature-culture hybrids, from nature/culture as a foundational dichotomy in human thought to the destabilizing of universal binaries, and from stable categories to complexity, gray areas and blurred boundaries. nature/culture has been one of the most provocative conceptual pairings in the social sciences, and sts has challenged the idea of nature versus nurture from the outset. my research focuses on twin studiessometimes described as the 'gold standard' for distinguishing between genetic and environmental influences on health and behaviorso questions about nature and nurture are ever-present, both in my informants' work and my own. scholarship in sts and anthropology challenged me to think about the ongoing work that goes into separating nature from nurture, but reading the work of francis galton, the infamous 'father of eugenics', is what helped me understand the enduring role of twins in the construction of a porous boundary between nature and nurture. galton's research took him in many strange directions, and he made contributions in areas as varied as statistics, fingerprints and family resemblance. he was the first researcher to propose studying twins to differentiate between the effects of 'nature and nurture', a phrase he coined in his influential article "the history of twins, as a criterion of the relative powers of nature and nurture", first printed in fraser's magazine in 1875. he is still cited today by scientists using twins to study the effects of genes and environments, and i first came across his work through tracing alison cool is a mellon sawyer postdoctoral fellow in the department of anthropology at new york university. her research is based in sweden and focuses on collaborations between life scientists and economists who are using twin studies to investigate genetic influences on economic behavior. leçons politiques de l'épidémie de sida security, disease, commerce: ideologies of postcolonial global health an influenza epicentre? the history of twins, as a criterion of the relative powers of nature and nurture. fraser's magazine 12 quoted from the reprint in key: cord-269213-tsm6zoe3 authors: slaughter, laura; keselman, alla; kushniruk, andre; patel, vimla l. title: a framework for capturing the interactions between laypersons’ understanding of disease, information gathering behaviors, and actions taken during an epidemic date: 2005-01-30 journal: j biomed inform doi: 10.1016/j.jbi.2004.12.006 sha: doc_id: 269213 cord_uid: tsm6zoe3 this paper provides a description of a methodological framework designed to capture the inter-relationships between the lay publics’ understanding of health-related processes, information gathering behaviors, and actions taken during an outbreak. we developed and refined our methods during a study involving eight participants living in severe acute respiratory syndrome (sars)-affected areas (hong kong, taiwan, and toronto). the framework is an adaptation of narrative analysis, a qualitative method that is used to investigate a phenomenon through interpretation of the stories people tell about their experiences. from our work, several hypotheses emerged that will contribute to future research. for example, our findings showed that many decisions in an epidemic are carefully considered and involve use of significant information gathering. having a good model of lay actions based on information received and beliefs held will contribute to the development of more effective information support systems in the event of a future epidemic. there is a great deal of current interest in preparing for outbreaks of infectious disease. both national and international efforts are aimed at developing strategies for rapid containment in the event of an outbreak [1] . government officials seek to contain an infectious disease through the cooperative efforts of the public by providing information either directly (pamphlets, web sites, posters, etc.) or through mass media news. the public also finds information concerning an outbreak from television programs and newspaper articles as well as from various ''non-official'' sources (e.g., socially through word-of-mouth). recent initiatives [2] show support for research that concerns tailoring public health messages during an outbreak disaster to the lay public ''with care so that information reported is easy to understand, is appropriate and is relevant. '' in this paper, we propose a qualitative methodological framework that characterizes human behavior during epidemics. this methodological framework, based on narrative analysis, is a tool for learning about how laypersons use information to build representations of an epidemic situation and how the results of this process influence their decisions to act. two factors, social influences and emotional triggers, are considered as mediators of actions and are therefore also of concern to this work. the methods we use allow insights into actions taken that are interpreted within the partici-pantõs situation (i.e., from the participantõs own viewpoint). this type of work is essential for tailoring health messages that are useable by people during an epidemic and effective at changing risky behaviors. we outline our methods using illustrative examples from data collected during the sars epidemic of 2003 [3] . section 1 discusses theoretical background with a specific focus on lay information gathering, lay understanding of disease, and lay health decision actions in a naturalistic setting. in section 2, we outline the basis for our methodological approach and describe our techniques used for capturing the interactions between the informational influences on lay actions. the data analysis techniques are also presented in section 2. an illustrative example using data collected during the sars outbreak of 2003 is discussed in section 3. our methodology was refined through application of the framework to the analysis of these data. in section 4, we summarize the lessons learned and provide direction for future research. the authors of this paper argue that a qualitative approach is necessary in order to obtain a macroscopic view of lay reactions to an epidemic crisis and to map out variables for large-scale studies. the related work we cite in support of this study does not fit neatly into the boundaries of a single field. health-related information seeking theories [4] and guidelines for constructing health messages for the public [5] have not been explicitly connected to lay explanations of illness and their behaviors during an epidemic. the main purpose of presenting our methodology is to demonstrate how the data analysis techniques can characterize the relationships between lay information gathering, understanding of information received, and actions taken. we briefly review literature related to information seeking, perceiving information needs [6, 7] , and emotional effects that play into lay perceptions of information [8] . we also point to cognitive theories related to lay comprehension and reasoning about illness [9, 10] in addition to theories of naturalistic decision-making [11, 12] . we have defined ''information gathering'' in the broad sense, to include both passive reception of informational messages in the environment and active searching [13] . general models of active information seeking [6, 7] describe the process of how a person seeks information, from an emerging awareness of a ''gap'' in current knowledge to communication of this information need as a query that will locate the missing information. within the domain of health information seeking, the models that relate to a gap in knowledge alone were found to be insufficient because they focus exclusively on rational processes. they cannot explain information-seeking behavior when patients do not seek medical information even though they are aware of gaps in their knowledge [4] . for health-related information seeking, theories of stress and coping have been integrated with two cognitive states that have been proposed as central to understanding an individualõs response to an adverse health-related situation: orientation towards a threat (referred to as monitoring) and turning attention away from the threat (referred to as blunting) [14] [15] [16] . the first studies that incorporated stress/coping theories with monitoring/blunting divided people according to personality types, as measured by the miller behavioral style scale (mbss). van zuuren and wolfs [17] studied 47 undergraduate students using the miller scale to assess whether a person is a monitor or a blunter. they found a direct association between problem-focused coping and monitoring. this study also showed that monitoring is related to unpredictability. they concluded that monitoring was positively related to the perceived degree of threat in a situation, that is, the higher the perceived threat the more information would be sought. using van zuuren and wolfõs techniques of dividing a sample based on the mbss, researchers such as baker [18] studied the information preferences of health consumers (in bakerõs study using women with multiple sclerosis). her results indicated, ''monitors were more interested in information about ms than were blunters and further, that their interest occurred earlier in the disease than did the interest of blunters.'' in recent articles, the notion of personality type influencing information seeking has been challenged. rees and bath [19] studied information seeking behaviors of women with breast cancer with results indicating that individuals may fluctuate between seeking and avoiding information, with the process being dependent on situational variables, such as how controllable the threat is perceived to be. due to the results given above, our data analysis attends to participantõs discussions about risk perceptions that are connected with information seeking acts. our expectation is that narrative data will reveal how information-seeking behaviors are affected by emotional stress and fear of infection (high risk perception). this idea is further supported by the literature from the field of public health that examines how heath information disseminated during a crisis is interpreted by laypersons [5, 20] . after information is gathered, it must be understood in order to be useful. gaining an understanding, or mental representation, occurs through the process of comprehension [21] . research on lay mental representations has shown that knowledge about disease consists of a combination of representations constructed from both informal social channels (i.e., traditional remedies learned from extended family) and formal instruction of scientific knowledge [10] . these two types of knowledge may be partly overlapping and contradictory when they deal with different aspects of the same disease. in cases where more than one model is used, a person tries to satisfy the requirements of each model even though this results in some redundant activity. research by keselman et al. [43] concerning adoles-centsõ reasoning about hiv provides an example of contradictory and overlapping models. they found that middle and high school students often relied on practical knowledge of disease, rather than on known facts about hiv. for example, one student acknowledged known facts about hiv, such as the fact that it is incurable. however, other explanations of the disease process later came into play while reasoning through a scenario about hiv. the scenario asked the student to discuss whether it was possible to expel hiv from the body. the same student who acknowledged the fact that hiv was incurable also believed that by drinking and exercising heavily it would be possible to expel hiv from the body. this student stated, ''cause people can stop it like that. by exercising, like they said. like that lady, like i told you, she exercised her way out of cancer, so i think this is true, you can exercise your way out of hiv probably.'' informally learned remedies and cultural beliefs sometimes play a major role in determining lay interpretations of epidemic events. for instance, raza et al. [24] examined lay understanding of the plague with persons belonging to the economically weaker sections of society in delhi and gurgaon india. in identifying the factors that influence the public understanding of science, they found significant amount of lay understanding based on ''extra-scientific belief systems'' (e.g., sins committed by people contributed to the outbreak), which were prevalent in the context of the plague epidemic. other studies have also looked specifically at the use of mental representations in relationship to decision-making. patel and colleagues [44] showed how physicians with different levels of expertise construct dissimilar problem representations on the basis of the same source information, which leads them to differing diagnostic decisions. as another example, sivaramakrishnan and patel [10] showed how understanding of pediatric illnesses influenced mothersõ choice of treatment for their children. their study showed how mothers interpreted concepts related to biomedical theories of nutritional disorders. they found that traditional knowledge and beliefs played an important role in interpretation and reasoning, which lead to decisions that were influenced by nonscientific traditional ideas. our work focuses on comprehended representations that are constructed by laypersons based on the information received during the epidemic (e.g., mass media, conversations with friends). we are interested in how these resulting representations lead to actions. the naturalistic approach to decision-making investigates decisions made in constantly changing environments, with ill-structured problems and multiple players [11] . these studies are conducted in real-life settings and investigate high-stakes decisions by looking at how people assess the situations they face, determine the problems they need to address, then plan, make choices, and take actions. this approach is related to our work since the actions taken by laypersons during an outbreak occur in an uncertain environment, with information changing over time, and with a highly personal threat. blandford and wong [12] has taken the key features of naturalistic decisions and combined them to form his integrated decision model. he used this framework for investigating decision processes and strategies of ambulance dispatchers. the ambulance dispatcher study used retrospective narrative data to build a model of decision-making in a dynamic, high-stakes environment. in summary, this model is based on the decision features: (1) situation assessment is important to decision making, (2) feature matching and story building are key to situation assessment because of missing information and uncertainty about available information, (3) piecing together the situational information is difficult because it arrives over a period of time and not in the most optimal manner, and (4) analytically generating and simultaneously evaluating all possible actions does not occur in dynamic environments. instead decision makers seek to identify the actions that best match the patterns of activities recognized in the situation assessment, one option at a time. although the framework provided by this study was formed from investigations of medical per-sonnelõs decisions, we believe that these observations will apply to our work and can be extended to layper-sonsõ actions in a high stress health-related situation. in our study, the infectious disease we are concerned with is severe acute respiratory syndrome (sars), which is a highly contagious respiratory illness that emerged in the guangdong province of china during the winter of 2003. the sars virus caused widespread public concern as it spread with exceptional speed to countries in asia, the americas, and europe. there were 55 confirmed cases in march 2003 when the world health organization (who) officially announced the global threat of a sars epidemic. in one month, the number of cases jumped to 3000 with more than 100 deaths. the sars epidemic had been halted by july 2003, with a total of 8427 cases reported to who and 813 deaths [3] . the countries affected by the outbreak of sars launched mass media campaigns to educate the public. information about what actions to take, the symptoms of sars, and other essential news changed on a daily basis as scientists and doctors treating sars cases reported new findings. the publicõs ability to understand and react to the information they obtained played a key role in stopping the spread of sars. the multifaceted control efforts including quarantine, tracing the contacts of sars patients, travel restrictions, and fever checks were essential to containment. all of these required that the public understand the sars-related information being conveyed and take actions to help protect themselves and others from spreading the disease. the sars epidemic provided a useful test case for our work and provided us with an opportunity to refine our narrative analysis-based methodology. there have been various methodologies used to study human behavior during epidemics and these offer different perspectives on lay response patterns. one approach is to study historical accounts [21] [22] [23] . these are usually told from a single personõs perspective on a groupõs response. while conclusions drawn from these types of texts might lend themselves to a global picture of an epidemic situation, there are potential drawbacks to using these as a basis for our present day outbreak preparation efforts. for instance, the occurrence describes peo-pleõs reactions during a different time period (not living in our current culture) and these texts might be biased towards the view of the author. another method of understanding lay reaction is through questionnaires/ surveys following a real-life episode [24] or a simulation of an outbreak [25, 26] . these questionnaires use pre-defined categories leading to large amounts of data on select variables of interest (e.g., whether or not people believe they would follow quarantine restrictions). the questionnaires impose a pre-determined structure onto the respondent and force the respondent to reply using the investigatorsõ categories. in our work, participants discuss events occurring during a recent outbreak that directly affected their life (occurring in close proximity to their home). a ''storybased'' interview allows data analysis of what information was obtained through the environment (e.g., media, web searches, rumors, and conversations with friends), reactions to the information, and the actions taken in the context of the participant who experienced it. these personal accounts, or narratives, of first-hand experience are a valuable source of data that can offer insight into a situation as it unfolded over time. by studying a sequence of events told as a retrospective narrative, an investigator can see how individuals temporally and causally link events (episodes) together. this approach falls under the qualitative paradigm and is referred to as narrative analysis [27] ; these methods have to do with the ''systematic interpretation of interpretation [28] .'' narrative analysis is commonly used as a methodological tool in health psychology [29, 30] and anthropology [31] . stories people tell are based on their mental representations of illness or ''learned internalized patterns of thought-feeling that mediate both the interpretation of ongoing experience and the reconstruction of memories'' [32] . narratives tell us something about how individuals understand events and construct meaning out of a situation. illnesses are often explained by reconstructing events in a cohesive story-like manner. for example, garro [33] discusses how people talk about illness; they link their experiences from the past with present concerns and future possibilities. narrative analysis is best used for exploratory purposes, for helping a researcher understand how individuals view a particular situation, and also for illustrating (but not by itself validating) theory. it is based on inductive techniques, rather than deductive hypothesis testing. this means that the researcher outlines top-level questions, which will be elaborated on and altered as the process of data analysis proceeds. personal narratives tell us a great deal about social, cultural, and other beliefs that cannot be accounted for at the onset of the study. the questions used to begin a study are broadly stated and are used, along with background literature, to focus on the initial set of boundaries delimiting the research. we ask how and why (i.e., meaning we are asking for a description) rather than what (e.g., a list of factors) questions. the main idea is to characterize the inter-relationships between laypersonõs information needs/gathering, comprehension of information received, and actions during an epidemic. participants in qualitative studies, narrative analysis included, are usually selected based on specifically defined criteria. in a study of lay reactions to an epidemic, it is therefore important to select participants who lived in close proximity to the outbreak. the participants should tell their stories to the researcher as close in time to the actual experience as possible (perhaps while the outbreak is still ongoing). depending on whether the researcher wants to do comparative analyses, participants might be selected by and grouped according to various dimensions such as age, socio-eco-nomic status, ethnicity, and/or geographical location. the number of participants selected is dependent on the number of comparisons to be made, and whether the researchersõ goals are to continue capturing narratives until the majority of the data contain overlapping experiences (almost all of the possible reactions to the epidemic have been uncovered). narrative data are usually collected through the use of an interview. we advocate a semi-structured interview [27] that lists a pre-determined set of ''loosely ordered'' questions or issues that are to be explored. the guide serves as a checklist during the interview so that the same types of information will be obtained from all participants. the advantage of this approach is that it is both systematic and comprehensive in delimiting the issues to be taken up in the interview. the interviews can remain conversational while at the same time allow the researcher to collect specific data. in many qualitative studies an interview is usually. in many qualitative studies an interview is usually organized around question-answer exchanges, but narrative studies require the use of free openended ''tell me'' questions as the most effective way to elicit a story-like response. it is important to avoid the use of closed, ''yes/no'' questions in order to facilitate narrative, rich descriptions. decisions about how to transcribe data and conventions used for analysis are driven by current theory, the research questions of interest, as well as the personal philosophy of the researcher. our analytic interpretations of epidemic narratives progress through three stages: (1) thematic coding of the factors emerging from the stories told concerning the epidemic, (2) organization of various aspects of the story according to chronological order, and (3) ''influence diagrams'' of factors influencing actions taken. thematic coding [34] is a type of content analysis and this technique is based on grounded theory (using a bottom-up procedure to identify categories present in the text). narratives may also be coded according to categories deemed theoretically important by the researcher. initially, a set of categories can be derived in conjunction with the semi-structured interviews based on theory from related literature (an initial top-down approach to coding), and this list of categories can grow as the rich descriptive data (a bottom-up procedure) is analyzed. one of the purposes of the ''thematic coding'' stage is to support the subsequent analyses. the categories are used to help untangle the interrelationships between information, understanding, emotions, social factors, and actions taken and systematically map our observations. in addition, an accuracy check can be done to determine whether participants are correct about their understanding of the disease. actions participants stated they have taken can be compared with guidelines from official sources (e.g., cdc). when participants speak freely in telling stories about the events happening this results in quite a bit of ''jumping around'' in time. people do not always begin their stories with the first event that occurred. researchers frequently find it helpful to organize the narrative according to temporal sequence (see labovõs work [36] ). for this work, classifying the temporal order of events is a necessary process leading to proper analysis of informational and comprehension-of-situation influences on actions taken. data are temporally coded in order to consolidate events participants expressed as occurring at the same time period (according to the participantõs perception of events). to illustrate, ''time 001'' is assigned to link together the segments 01-10 shown below and the same code ''time 001'' is assigned to segments of text lines 101-104 found later in the interview. 01 and i spoke to my girlfriend and she said that she was going to leave hong kong 02 and i was really shocked because she was the one that was like myself, 03 just kind of sticking around and saying oh itõs not a big deal 04 and weõll manage and uh she um felt that she just got into a panic herself. 05 and what happened around that time at the end of march that there was a rumor 06 that a teenager actually started on the internet, 07 he put it on he like, he said that the airport had been closed 08 and that people couldnõt get in or out of hong kong 09 and they later deemed of course it was a hoax. 10 but at the time my girlfriend heard this, she didnõt know, she panicked and she was leaving. . . . later in the interview . . . 100 i did a bit more internet grocery shopping because i did not want to go to the grocery stores. 101 usually, it was really strange because right around, right. . . a week or so before i left i would go to the market. 102 it was actually; it was right around the time that that rumor came out that the hong kong airport had shut down. 103 the store was so packed it was unbelievable. 104 i thought it was a holiday, and i even asked a friend. i said, what is going on with the market? the construction of causal-link maps, sometimes referred to as ''influence diagrams,'' is used for modeling interactions between events [37] . these types of diagrams formalize laypersonsõ explanations into connected logical structures that can be examined as an overview of all the events occurring for a subset of time during an epidemic. this process maps the influences on actions taken for each time period identified (following chronological organization of the data described in section 2.4.2). figs. 3-5 are each influence diagrams. an example of how we created these diagrams is given using data from the taiwanese participant (see fig. 1 ). we first identify the associative ''participantstated'' relationships between coded themes. in these data segments, we can see that officials are promoting (successfully) washing hands and we can also see that family pressures have an influence on hand washing behaviors. thus, ''informational: officials <promotes> action: washing hands'' and ''social: family pressure <leads_one_to>action: washing hands.'' the categories of interaction labels (e.g., <promotes>) must be standardized for consistency. this process facilitates asking research questions across conditions (e.g., comparisons by socio-economic status) for numerous participants. eventually, the objective is to be able to make generalizations about the interactions between factors/events that influence layperson reactions during an epidemic. what are laypersonsõ decisions based on? how does social pressure affect decisions? what motivates active searching of information? the evaluation of the validity (or trustworthiness) of a narrative analysis is a critical issue that does not have an easy solution. one way to test whether the results are valid is related to persuasiveness. an analysis can be said to be persuasive when ''the claims made are supported by evidence from the data and the interpretation is considered reasonable and convincing in light of alternative possible interpretations'' [27] . another way of checking validity is to conduct what is called a ''member check'' [38] . during a member check, participants in the study are given copies of the research report and asked to appraise the analysis conducted by the researcher, interpretations made, and conclusions drawn. these two measures of validity assess whether the interpretations of the data reflect the views held by the participant; there is no way to compare the results obtained with an objective truth. however, a community of scientists validates knowledge as they share results obtained across multiple studies. as the sars epidemic unfolded, we were in the process of exploring methodologies that would focus on the interactions among the information requirements of laypeople concerning an outbreak of infectious disease, their understanding of that disease, and their actions taken during an outbreak (or during a simulated outbreak). the sars epidemic was used as a test study to refine the narrative analysis-based methodology. in the following sections, we show how these methods were applied and what we learned in the process. our specific research objective is to characterize lay-personsõ reactions during an epidemic. specifically, we ask why participants take certain actions (or recommended actions stating what should be done) and how their actions are linked to (1) their understanding of epidemic/sars infection, (2) the influential informational events (including information gained from a social situation), and (3) other factors such as feelings that come into play. other research questions can be answered using the data that report on what happened during the sars outbreak. for example, the interview texts also result in a list of information needs expressed by the lay public concerning an outbreak as well as a general list of actions taken for sars prevention. we interviewed eight residents from three sars outbreak regions. two of them were living in asia (1 from hong kong and 1 from taiwan) and six were from toronto, canada. participants recalled events taking place from the time when news began about the ''mysterious'' illness until the time of the interview, a time span of approximately 90-120 days. none of the participants had a medical background or a degree in biology, or related fields. all of the participants except for the taiwanese male were native english speakers. the interviews with the residents from asia took place in the late spring of 2003. these interviews were conducted in the united states by the first author. the hong kong resident was an american caucasian female who had been living in hong kong for the past four years. she decided in late march to return to the united states temporarily because of the sars outbreak. she was 37, married and had a one-year-old daughter at the time of the interview. she was interviewed in her home in washington, dc. the other resident of asia was a taiwanese male, aged 24, of chinese descent, who was living in taipei, taiwan for the entire duration of the epidemic. the interview took place in new york city while he was vacationing. both participants had an undergraduate degree from a university in the united states. the interviews with the toronto residents took place during the early summer of 2003. these interviews took place in toronto and were conducted by a research assistant from the information technology division, department of mathematics and statistics, york university, toronto. toronto resident 1 was a 31-year-old male, resident 2 was female (no age recorded), resident 3 was a 35-year-old female, resident 4 was a 38-yearold female, resident 5 was a 42-year-old male, and resident 6 was a 45-year-old male. toronto residents all had bachelorõs degrees, and residents 3 and 6 also had a masterõs degree. the complete semi-structured interview is presented in appendix a. the procedure for using this interview guide is to allow for flexibility when probing the respondent. when interviewing, we stressed the importance of keeping in mind the purpose behind each of the probes. we linked lay understanding to information sources using probes, for example, ''how does sars affect a personõs body?'' followed by ''can you tell me how you learned about this?'' we asked about the action of seeking information and connected this with the partic-ipantõs current information needs. the two-part probe ''what questions did you have about sars and what caused you to look for information about [fill in with the topic of the question asked]'' is of this type. other actions concerning self, family, or community protection were connected to understanding of sars using probes such as ''for example, did you buy a facemask, vitamins, or do something else?'' ''why did you decide to [repeat preparation given by respondent]?'' and ''how is [repeat preparation given by respondent] going to help prevent sars?'' this instrument design was based on our research goals to link interactions between understanding, information received, and actions taken. the questions ask about the participantõs sars experience over time, from the time prior to the outbreak and then ask the participant to project their own scenario about what they believe will happen in the coming weeks following the interview. the arrangement of the interview into time periods (before, during, and upcoming events related to the epidemic) facilitates the data analysis when looking at the interactions and influences between informa-tion received, lay understanding, and actions taken. we believe that this type of interview could be used during any epidemic outbreak. the strategy we used for the reduction and interpretation of our narrative data consisted of three stages. in the first stage, we identified the categories of sars epidemic-related events and concerns discussed by our participants. we did thematic coding, in which we ''let categories emerge from the data rather than assign them from a pre-defined list'' [34] . using the qualitative software program, nvivo [35] , we iteratively coded emergent categories by marking segments of text that are instances of actions the participant said they took, explanations given concerning sars, information sources used, and information needs expressed. the second stage consisted of reorganizing the events in the narrative into the correct chronological order. this was necessary because participantõs stories and anecdotes were not always told in the same order that they occurred during the epidemic. the last stage used the time-ordered data from phase two in order to evaluate influences on actions taken. for each action identified during thematic coding (stage one), we looked at partic-ipantõs explanations, reasoning process, and emotional state prior to the action. we began the process of coding by constructing a rudimentary coding scheme based on the interview probes and by reading through the first transcript. for example, we could anticipate that participants would discuss ''wearing face masks'' and ''washing hands'' as actions taken and these were included in the initial scheme. this coding scheme changed incrementally as we carefully scrutinized all the interview texts (from hong kong, taiwan, and toronto) resulting in the final version of the coding scheme in appendix b. this process is clarified using an illustrative example. the transcripts, in rough form, are read and the researchers specify codes at the phrase level, sentence level or paragraph level. for example, the code ''risk assessment of sars'' was assigned to the phrase 02 (from participant 1): 01 in march, early march i started to hear about the sars virus that was in hong kong 02 but it did not seem very, ahhh quite epidemic mode after seeing similar texts concerning the same type of expression, we assigned a more general code called ''sars risks'' to all similar instances in all interviews, such as in phrase 01 (from participant 4): 01 however, it was on the news but they didnõt put a lot of seriousness into the broadcast. each category was defined for further coding consistency. for example, ''information need: containment status'' was defined as ''an information need or question stated that is about any topic related to control of the outbreak (e.g., ''has the virus peaked?''). multiple codes could be assigned to the same text. spreads because itõs in a really tight confined area [location: tightly confined area] like a hospital room [location: hospital room]'' the double underline is used when overlapping categories (i.e., [location: tightly confined area]) are assigned to text already coded in another category (i.e. ''really tight confined area''). the process of thematic coding resulted in a list of instances of actions, explanations, and information needs expressed by participants in our data. we also looked for ''new'' categories of entities and events that would help us to make sense out of what people were experiencing during the sars outbreak and what factors influenced their perceptions of the epidemic response. although not initially themes in our work, we also coded policy, location of events, persons involved, and other major categories that emerged from the data. from the codes that emerged, we get a sense of: (1) the types of actions people took (e.g., avoiding others), (2) social situations they observed during the epidemic (e.g., people are banned from entering someplace because of elevated temperature), (3) types of actions the participants recommend doing for sars prevention (e.g., get proper rest), (4) types of explanations described by participants about sars (e.g., cultural influences and cultural factors), (5) the information needs participants expressed (e.g., participants wanted to know what the potential outcome was for a person who contracted sars), (6) what emotions people expressed concerning sars (e.g., ''eerie feeling/freaked out''), and what information sources people consulted (e.g., tv media). we began to see some patterns emerging from our eight personal narratives. within the list of explanations of sars, there are none concerning the physiological processes of a virus within the body (because we did not observe a single instance in the data). the sars participants in the asian cities seemed to have a great knowledge of certain facts (about what actions to take). this is not surprising since they were living in places where the threat is presented on a daily basis (e.g., everyone wearing masks on the street) and they were bombarded with information in the media. what was interesting was that these two people felt a need for further information about the mechanisms behind the viral processes and not just a superficial list of what to do. another pattern observed was the expression of suspicion by participants from canada. many of the emotions that were expressed in the coding scheme inventory are related to fear and anxiety. participants, notably the toronto residents, expressed suspicion about a possible cover-up of outbreaks, (i.e., ''why did this occur in toronto and not in the us?''). these participants had questions and concerns about government policy [39] . to illustrate how the thematic data can be employed to evaluate current guidelines, we used the coded narrative texts to further conduct a comparison of partici-pantsõ knowledge of sars symptoms, treatment, transmission, and preventions with cdc web site information [40] . we made this comparison using guidelines from the same time period as when the interviews occurred. to do this, we coded cdc guidelines using the same methodology described in section 3.4.1. we then took each sentence from interviews that were coded as a symptom, transmission mechanism, treatment or prevention, and compared those with sentences from the cdc guidelines. overall, participants had beliefs that were consistent with current understanding of sars, with almost 95% (155/164) of the sentences from the interviews concerning symptoms, transmission mechanism, treatment, or prevention of sars corresponding to those found in the cdc guidelines. such a high level of consistency would be very unlikely in a larger more diverse sample. reorganization of events was necessary to facilitate data reduction and to assist in the interpretation of the narratives. one result of this time ordering was unexpected and resulted in further separation of each personal narrative into several time segment blocks. for each participant, we found that some events were mentioned multiple times and signaled major changes in the participantõs emotional state, actions taken, understanding, or informational needs and we marked these as ''trigger'' points for change. for example, as the outbreak in hong kong became more serious and more people were infected, the participantõs behavior and reaction naturally changed leading to new actions taken, a greater understanding, and more attention focused on the daily news report. the data were separated for each narrative so that the end of each time segment block signals major shifts in thinking about the epidemic (e.g., ''and at that point it really got into my consciousness about this virus and that it was very serious''). examples of the ''triggers'' that propelled the participant to change their viewpoint and signaled the beginning of each new time period are marked in italic type in figs. 4 and 5 shown in the section below. we then performed the analysis described in section 2.4.3 to capture the connections between the events in order to organize and standardize the relationship between information, lay understanding, and actions. we found that constructing visual representations of interactions was very useful for characterizing each overall causal explanation. to illustrate with an example, we use our hong kong participant. figs. 3-5 correspond to time segment blocks for that participant from the start of the epidemic (time period 1) until the time the participant decided to leave hong kong (time period 3). in fig. 3 , we show that she was passively watching the news and did not feel that there was a heavy emphasis on the ''mysterious illness'' that was occurring in the ''new territories.'' her understanding of the disease was generated from these reports and primarily consisted of a belief that ''it was not affecting us.'' (because she is a westerner in hong kong) she did take one precaution, that is, to wash her hands more often and wipe her childõs hands. this was based on her concern over her childõs well being to; nevertheless, take precautions against the illness that she thought was ''like a cold or pneumonia.'' in the second time period, fig. 4 , we began to see her concern increasing. this change was triggered by the the trigger leading to increased concern is shown in italic type. fig. 5 . example of coded interactions from the hong kong participant: time period 3 (from an increased awareness of sars as an epidemic to a decision to leave the region). the trigger leading to increased concern is shown in italic type. realization that her neighborhood bank teller lived at amoy gardens and that it could possibly spread to her family. she builds her understanding of sars, focusing on the model of transmission. all of her actions taken are based on this model. for the most part, she followed the guidelines presented in the media, except that she did not wear a mask, in spite of the fact that there was social pressure ''people wearing masks on the street,'' and that she also avoided walking past people because ''i didnõt want somebody to sneeze or cough on me and me get caught in the drift of that and get it on me' ' we see major changes in anxiety level, actions taken (precautions), understanding, and informational factors in the third time period, shown in fig. 5 . many interactions were recorded that form larger ''influence interrelationships.'' for instance, she made a decision to leave hong kong. this was strongly related to a friendõs decision to leave as well. the friendõs decision increased her anxiety and shock, pushing her to make the same choice. she stated that her friend (but she did not state she felt panic) was panicked due to an internet hoax that stated the airports of hong kong were closed and no one could get out. across all the narrative data, we looked at peopleõs reasons for actions. the major influences on actions are in table 1 below. one important influence on actions was the vocabulary used by an information source (in particular, mass media), which served as a catalyst for major changes in lay reaction. as an example, use of the word ''epidemic'' caused emotional and behavioral changes. a toronto resident stated that seeing the word ''epidemic'' was key ''uh, i wanted to know how fast it was spreading because if i thought it was an epidemic i would make the decision to stay home and not go to work.'' the hong kong resident provides another example of this. after seeing the headline ''sars an epidemic in hong kong,'' this lead her to conduct web searches, which in turn lead to further learning about transmission. she therefore updated her understanding of the virus through the web searches, learning that the ''virus lives on surfaces up to 3 hours.'' these were considered a specific type of ''trigger'' based on source. these media triggers are ''emotionally loaded'' words that caused participants to experience major shifts in thinking about the epidemic. they were identified while reorganizing the narratives to consolidate all events (according to the participantsõ perceptions) that happened in the same time period. participants stated certain media events (i.e., ''triggers'') over and over again in separate stories, linking different aspects of their experience. we found that there were several primary types of influences on expression (or realization) of an information need. these are listed in table 2 . although partici''it kinda freaked me out'' --concern over family ''but since i did have a child'' perception of safety ''so that leads me to believe that the general public is somewhat safer'' because ''you have to'' (social pressure) ''so you have to wear the mask'' we considered line 05 an ''information need'' statement. types of information need statements in the data were consolidated as table 2 . this methodology leads to emerging hypotheses from our data that can be explored in subsequent work. these suggestions were derived after examination of the participant-stated relationships between coded themes (as described in section 3.4.5). the descriptions of these emerging ideas refer back to figs. 4 and 5. in fig. 4 , we begin to see that epidemic decisions were not based on quick emotional reactions (panic) or social influences entirely. rather, they were based on strong connections between knowledge building, information gathering, and making decisions (e.g. whether to wear a mask). the participantõs understanding of disease transmission and epidemic status (containment) influenced decisions either directly, or indirectly (through increasing negative emotions). evidence that many decisions in an epidemic are carefully considered and involve use of significant information gathering prior to the actual decision is consistent with some of the literature in public health [39] -but not in the literature related to decisions in emergency situations [12] . we found that as concern increased, participants became more aware of information until they felt the need to move beyond scanning to searching databases for information (passive viewing switched to active as fear increased). thus, we hypothesize (1) that future studies will show this relationship between reactions of concern and increasing use of information sources to investigate the various actions to take during an epidemic. contrary to the effortful, and systemic information seeking described by participants that related to increasing concern, we saw several occurrences in the data when social factors lead to quick and resolute precautionary actions. for example, the participant described a change in her understanding of risk between time periods two (fig. 4) and three (fig. 5) ''and i spoke to my girlfriend and she said that she was going to leave hong kong and i was really shocked because she was the one that was like myself, just kind of sticking around and saying oh itõs not a big deal and weõll manage . . . and once i heard that she was leaving, then it put me into motion thinking i need to get out of here. this is not the place to be right now.'' social aspects tend to highly ''personalize'' the risk involved and alter thinking ''it can affect me.'' the hypothesis (2) that emerges from this data is that information that personalizes the epidemic can affect the actions taken, leading to quick decisions to protect against infection. in terms of information seeking, the results we have found related to hypothesis 1 are similar to those of van zuuren and wolfs [17] and rees and bath [19] described in section 1. as the personõs concern (perceived degree of threat) increases during an epidemic, so does information seeking. however, we did not find any intentional avoidance of information that occurs in patients with a serious illness. in the epidemic situation, lack of information seeking was only observed when there was a perceived need to make a quick decision. the two observations made in the above paragraphs are consistent with dual-process models of social reasoning; the elaboration likelihood model [41] , and the heuristic-systematic model [42] . these models predict that there are two routes of information processing. in one route information is processed and decisions are made fast and superficially, and in the other route people engage in more time consuming, effortful, and systematic information processing and problem solving. these models, specifically, chaiken et al. [42] predict that the fast and superficial (like hypothesis 2) information-processing route is used in situations when people are not motivated and/or do not have the ability for making decisions. in the case of people in an epidemic situation, future work may pinpoint the situational factors that result in thoughtful versus hasty actions. we have outlined a methodology for characterizing factors that affect information gathering, comprehension, and preventative behavior by lay people during epidemics. we approached the task using literature from all three areas as a framework, where the cognitive aspects underlying acts (behavior) is given a major focus. this perspective suggests that decisions and actions are largely based on individualsõ cognitive representations of events, which are in turn shaped by prior knowledge and new information, as well as by social and emotional factors. given the complexity of the influencing factors, and the interconnections among these variables, a structured qualitative approach was considered as most appropriate for gathering data. public health guidelines concerning ways to tailor communication describe aspects of messages that are effective during a crisis event [5] . the goal of this methodology is to be able to specify ways to increase compliance with guidelines and how to reduce behaviors that increase risk. use of this methodology captures the major themes that emerge related to information needs and actions. this allows officials to address the publicõs concerns and learn about the actions they are taking. yet, the major contribution of this methodology is related to developing detailed causal/temporal models showing the influences between factors. with this, it is possible to identify problematic situational variables and intervene when they may lead people to make rash decisions. this methodology was applied to study lay reactions to the sars virus outbreak of 2003 but might be applied to other viral infectious disease outbreaks, either naturally occurring or through terrorism. having a better understanding of the reactions of the layperson will lead to developing information support systems as well as guidelines for preparedness in the event of a future epidemic. information provided through guidelines or ''just-in-time'' (depending on the needs) could help the lay public to respond appropriately during future epidemics. results from studies using these methods can also be used to educate professionals (e.g., hospital administrators, the media, and government policy makers) by providing models to explain, for example, what strategies laypersons use to assess the situation during outbreaks of an infectious disease. buy supplies (e.g., anti-bacterial wipes) centers for disease control (cdc) press release. cdc announces new goals and organizational design cdc imperative 8: timely, accurate and coordinated communications outbreak of severe acute respiratory syndrome in hong kong special administrative region: case report on user studies and information needs communication for health and behavior change: a developing country perspective question-negotiation and information seeking in libraries ask for information retrieval models in information behaviour research emr: re-engineering the organization of health information reasoning about childhood nutritional deficiencies by mothers in rural india: a cognitive analysis naturalistic decision making: where are we now situation awareness in emergency medical dispatch looking for information: a survey of research on information seeking, needs, and behavior attention and avoidance: strategies in coping with aversiveness. seattle: hogrefe and huber interesting effects of information and coping style in adapting to gynaecological stress: should a doctor tell all monitoring and blunting coping styles in women prior to surgery styles of information seeking under threat: personal and situational aspects of monitoring and blunting a new method for studying patient information needs and information seeking patterns information-seeking behaviour of women with breast cancer a first look at communication theory the story of the great influenza pandemic of 1918 and the search for the virus that caused it the coming plague: newly emerging diseases in a world out of balance how to vaccinate 30,000 people in three days: realities of outbreak management kaleidoscoping public understanding of science on hygiene, health, and the plague: a survey in the aftermath of a plague epidemic in india community reaction to bioterrorism: prospective study of simulated outbreak the public and the smallpox threat narrative analysis. newbury park: sage publications acts of meaning introducing narrative psychology, self, trauma, and the construction of meaning narrative psychology narrative and the cultural construction of illness and healing models and motives cultural knowledge as resource in illness narratives: remembering through accounts of illness basics of qualitative research techniques and procedures for developing grounded theory the nvivo qualitative project book some further steps in narrative analysis. the journal of narrative and life history qualitative data analysis. california naturalistic inquiry understanding public response to disasters communication and persuasion; central and peripheral routes to attitude change heuristic and systematic information processing within and beyond the persuasion context you can exercise your way out of hiv and other stories: the role of biological knowledge in adolescentsõ evaluation of myths cognitive psychological studies of representation and use of clinical practice guidelines this work is supported in part by nlm training grant lm07079-11. we thank david kaufman for reading and reviewing the manuscript. key: cord-269612-pmzdovna authors: pennington, hugh title: politics, media and microbiologists date: 2004 journal: nat rev microbiol doi: 10.1038/nrmicro846 sha: doc_id: 269612 cord_uid: pmzdovna severe acute respiratory syndrome (sars) took everybody by surprise. its emergence was one of the most significant microbiological events of 2003. it challenged microbiologists to identify the aetiological agent and satisfy koch's postulates — in so far as they ever can be met for a virus — in real time. not only were the patients' respiratory secretions and the agents grown in cultured cells put under the microscope, but so were the actions of politicians. what lessons can we learn from sars? acquired 6 , and of the 1,755 sars infections in hong kong, 386 (22%) were in healthcare workers -320 of whom were hospital staff who were infected while on duty 7 . a low degree of transmissibility relative to other viruses is not the only property of the sars virus that was an important factor in the success of the response to the outbreak. the ease of propagation and identification of sars by well-established, standard virological methods were also of significance. the causative virus was grown without particular difficulty or problems with detection in readily available standard cell-culture systems. within a month of the identification of sars as a new clinical entity of uncertain aetiology -in late february 2003 in hanoi, vietnam -the virus had been grown in several laboratories. researchers at the university of hong kong 8 cultured the virus using foetal rhesus monkey kidney cells challenged with material from an open lung biopsy from a 53-year-old male hong kong resident, and a nasopharyngeal aspirate from a 42-year-old woman. researchers at the bernhard nocht institue for tropical medicine, hamburg 9 used vero cells inoculated with sputum from a 32-year-old male physician who had fallen ill in new york, after travelling from singapore where he had treated a patient. finally, at the centers for disease control and prevention (cdc), atlanta 10 , researchers cultured the virus in vero cells inoculated with oropharyngeal samples from a 46-year-old male physician working in vietnam, sputum from a 49-year-old male, a kidney sample from a 46-year-old male and oropharyngeal washings from an adult vietnamese patient. in hong kong and atlanta the results of thinsection and negative-staining electron microscopy showed unequivocally that the cytopathic effect was being caused by a coronavirus. in all three laboratories, reverse transcription pcr and comparison with known coronavirus sequences revealed the same sequence identity; this work also showed that the sars virus was new, because its sequences were only distantly related to those from the wide range of previously sequenced coronaviruses that infect humans, dogs, cats, pigs, bovines, rats, mice, turkeys and chickens. louis pasteur said that "chance favours the prepared mind". the relevance of this explanation of scientific success to the sars virus, and in particular to the rapid initiation of collaborative work to understand and control it, is very clear. influenza had prepared the way. ever since the 1918-1919 influenza pandemic -which killed many millions, and was the low r 0 value for sars indicates that controlling the spread of infection should be easier to achieve than for many other respiratory viruses. the only other virus spread by the respiratory route with an r 0 value approaching that of sars is smallpox. for isolated pre-twentieth century populations with negligible immunity, gani and leach 3 estimated the r 0 value for smallpox to be 3.5-6.0 and, for 30 importations into europe between 1958 and 1973, to be about 5.5 for community-acquired disease. although an r 0 value of this magnitude means that without control measures an outbreak would grow exponentially, in the case of smallpox outbreaks it was always possible to rapidly reduce the value of r 0 during the progress of an outbreak. maintaining the r 0 value below 1 prevented the development of secondary cases; it was achieved by locating and isolating cases, and creating a ring of immune individuals around the outbreak by vaccination. outbreaks lasted only for weeks, with case numbers rarely exceeding double figures; more than three-quarters of outbreaks ended with the generation that was infected immediately after the detection of infection. r 0 is a function of k,b and d ; where k is the number of contacts each infectious individual has per unit time; b is the probability of transmission per contact between an infectious case and a susceptible person; and d is the mean duration of infectiousness 4 . in the case of infectious patients in hospital, their physical proximity to other patients and regular -often close and prolonged -contact with medical staff and nurses means that k and b will be greater than in the community or in domestic settings, particularly if transmission is only effective over short distances -centimetres rather than metres. this was the case for both sars and smallpox, and nosocomial transmission was indeed a characteristic feature. in 45 outbreaks of variola major in europe between 1950-1971, reviewed by mack 5 , transmissions in hospital settings far outnumber those in any other category. of the 680 cases, 339 (49.8%) contracted the disease in hospital, and 128 cases (18.8%) were in staff. in singapore, 206 (76%) sars cases were nosocomially severe acute respiratory syndrome (sars) took everybody by surprise. its emergence was one of the most significant microbiological events of 2003. it challenged microbiologists to identify the aetiological agent and satisfy koch's postulates -in so far as they ever can be met for a virus -in real time. not only were the patients' respiratory secretions and the agents grown in cultured cells put under the microscope, but so were the actions of politicians. what lessons can we learn from sars? the common cry uttered after crises is that 'lessons must be learned' . what lessons does sars teach? the crisis is over, at least for the time being, but how certain can we be that the german philosopher hegel was wrong when he said "what experience and history teach is this -that people and governments have never learned anything from history, or acted upon principles deduced from it"? before attempting to answer these questions using sars as an appropriate example, it is necessary to consider the sars virus itself and ask another question. how severe a test did sars pose? were we lucky? the answer is 'yes, we were' . this is qualified by the number of deaths that it caused; however, it is due, at least in part, to the properties of the virus. most important is the low r 0 value -the basic reproductive number -for the sars virus, which represents the number of secondary infectious cases that are generated by an average infectious case in a susceptible population. the r 0 value predicts the likelihood that an infectious agent will start an outbreak, the amount of transmission that can be expected in the absence of control measures and the ability of these control measures to reduce spread. studies on the sars outbreak in hong kong 1 -after the exclusion of two 'superspread' events where special circumstances allowed index cases to infect many individuals (at the prince of wales hospital and at the amoy gardens estate) -gave an estimated r 0 value of 2.7. this is much lower than for any other virus that is spread by the respiratory route; r 0 values for such infections in england and wales have been estimated to be 16-18 for measles, 10-12 for chickenpox, 11-14 for measles and 6-7 for rubella 2 . national influenza centres in 83 countries also had an extremely important role 13 . reports in early february 2003 from guandong province, china, of 305 cases and five deaths owing to an atypical pneumonia of unknown aetiology, coupled with the isolation of an avian influenza virus a subtype h5n1 from two members of a family that had visited fujian province, china, in january, caused the activation of the pandemic plan. from analyses of samples taken from vietnam, singapore and hong kong, laboratories in the network ruled out the possibility of infection by any of the known influenza virus strains or other established causes of pneumonia, and concluded that sars was new. on 15 march 2003, the who issued emergency travel advice and, using the influenza network as a model, set up a network of scientists from 11 laboratories around the world to identify the causative agent and develop diagnostic tests. laboratories were chosen owing to their experience in detecting a wide range of microorganisms, a history of collaboration in international investigations coordinated by the who, their technical capacity to fulfil koch's postulates and their access to sars samples. rules governing the confidentiality of data were set -shared data and information would only be used to advance the project in a collaborative way, data would only be shared outside the network with the approval of the originating laboratory, and caused by a virus of subtype h1n1 -the possibility of the emergence of a virus strain capable of causing a similar event has, of necessity, been contemplated. the world health organization (who) initiated its international cooperation coordination programme in 1947. pandemics with significantly lower mortalities occurred in 1957 (asian flu, subtype h2n2), 1968 (hong kong flu, subtype h3n2) and 1977 (russian flu, subtype h1n1) (table 1). although none have occurred since, the influenza outbreak that occurred in hong kong in 1997, although local and small in case numbers, had such a high mortality rate in confirmed cases that it stimulated a review of pandemic response policies both in hong kong and internationally. it meant that the hong kong department of health, hospital authority and laboratory surveillance facility 11 , and the who, were particularly well prepared to respond to the sars outbreak. in march 1997, an outbreak of avian influenza caused by the a virus subtype h5n1 killed several thousand chickens in three rural hong kong chicken farms. in may 1997, a 3-year-old boy in hong kong contracted an influenza-like illness and died 12 days later from reyes' syndrome -a paediatric complication that is associated with salicylate medication, which he had received. the virus strain resisted characterization with the available reagents; by august, detailed study in the netherlands and the united states had revealed that the virus was closely related to the avian strains that were prevalent in march. in november, human cases caused by this virus began to occur; by late december, there had been 17 cases, of which five were fatal. contact with chickens had occurred in all confirmed cases. on 28 december 1997, the slaughter of all chickens in hong kong (a total of 1.6 million) began, their import was stopped and the outbreak ceased. in 1999, a group of influenza specialists reviewed the responses to the outbreak and drew several lessons from them 12 . some were influenza-specific, but others had wider relevance. regarding the actions that were taken in response to the outbreak, they reported that, at the time the outbreak started, the who was developing formal guidelines for addressing pandemic situations. these guidelines were revised after the hong kong influenza epidemic to include two strategic steps that were important in the outbreakrisk assessment (data collection and data evaluation) and risk management (continuously considering and reviewing the stages of a response, defining the risks and benefits, and making recommendations for the next steps to be followed). these principles underpinned the who response to sars. the who global influenza surveillance network of four collaborating centres (in atlanta, london, melbourne and tokyo) and 112 committee was charged with the identification of lessons to be learned and with making recommendations for future epidemics. they focused on seven principles: a strengthened epidemiology capacity, systems for early detection and reporting, contingency planning, clear command and control structures, integrated responses, a surge capacity and transparency and effective communication. although it is impossible to disagree with these principles and their importance in outbreak control, a striking feature of the 279page report is that, with the exception of a box describing the isolation of the virus in hong kong entitled 'ground-breaking discovery' early in the report, there is little comment, favourable or unfavourable, about virology, virology laboratories or virologists. it could be said that this might be a reflection of the backgrounds and interests of the committee that generated the report -the two co-chairs (both from the united kingdom) were experts in hospital management and administration and in public health, respectively. but it is very probable that it reflects another problem -the lack of regard that is paid to the importance of microbiology in the response to microbiological threats to public health. reforming and improving healthservice administrative structures and information systems, and planning for unexpected rises in the number of contagious patients are all necessary, but by themselves they are insufficient. the flaw in hegel's aphorism about lessons from history is that microorganisms evolve in real time; learning lessons from past failures (and successes) will be insufficient because evolution throws up new challenges. in their review 18 , maclehose, mckee and weinberg state that "one of the greatest challenges facing surveillance systems is awareness of the unexpected, recognizing when things seem not quite right. nipah virus was thought to be japanese b encephalitis, west nile virus in new york was thought to be st louis encephalitis, and prions were thought not to cross species barriers. focusing surveillance systems on the diseases of today fails to address the challenges of an uncertain future". we were lucky with sars due to the existence of a network of laboratories that were looking for new influenza viruses and which were linked by the mature surveillance network run by the who. other microbiological networks also exist. for food-borne pathogens there are, for example, pulse net 19 in the united states (which uses standardized pulsed-field gel electrophoresis (pfge) protocols to generate and compare profiles of escherichia coli o157, salmonella spp. and listeria monocytogenes), and enternet more than £8 billion. the conclusions of the 'lessons to be learned inquiry' 16 regarding the role of british virologists before and during the outbreak speak for themselves. the report states that, although the pirbright laboratory is the world reference laboratory and holds data on reported outbreaks throughout the world, "there is no coherent assessment of the full range of work undertaken by pirbright in relation to the national surveillance and control strategies" and "the service arrangements in place in 2001 covered the processing of 300 samples a year…but contained no procedure for increasing the level of provision in an emergency". in addition, "the laboratory was not consulted when the fmd contingency plans were drawn up". the same failure to consult and use scientific expertise was evident in the handling of bovine spongiform encephalopathy (bse) -politics came before science. not long after the first occurrence of bse, an attempt to describe a case in the scientific literature was firmly quashed by the head of the veterinary investigation service of england and wales owing to "possible effects on exports and the political implications" 17 . the phillips inquiry into bse and variant creutzfeldt-jacob disease (cjd) reported the lessons that had been learned; the largest number of which addressed one topic -the improved use of scientific advisory committees. their failure to use the full range of expertise available -even within the united kingdom -contrasts sharply with the inclusive approach adopted by the who in the case of the sars epidemic. the united kingdom was lucky with sars as there were no reported outbreaks. however, the situation was very different in hong kong, which had 1,755 cases and 300 deaths. an expert review committee appointed by the government of the hong kong special administrative region reported its findings in october 2003 (ref. 7 ). among other things, the samples would be regularly exchanged. there were daily teleconferences and a secure who website. on 16 april 2003, the participating laboratories collectively announced the conclusive identification of a new coronavirus as the causative agent. the who had performed well 14 . owing to its low r 0 value and ease of cultivation, the challenge that sars posed to the who was less difficult than it might have been. however, not everything was straightforward; for laboratories, epidemiologists and international organizations to react they must be told that there is a problem. the reaction to sars was delayed because initially it was unclear that there was a problem. the first cases of sars probably occurred in guangdong province, china, in november 2002. on 23 january 2003, the health authority in guangdong province produced an expert report on the outbreak. many of the conclusions that the health authority reached would have been of significant use to policy makers elsewhere, but circulation of this expert report was limited. neither the who nor the hong kong authorities received a copy. whether an early reversal of the denial of sars by the chinese authorities during the early part of the epidemic would have had a significant effect on later events can only be a matter for speculation. however, the who was not able to investigate the situation in china until april 12, by which time sars had spread worldwide. a key factor in this spread had been the overnight stay in room 911 of the metropole hotel, hong kong, of a professor from guangzhou in guangdong, which triggered outbreaks in hong kong, singapore, canada and vietnam. the lesson for microbiologists is a stark one -they operate in a political environment, and it can be unhelpful. other examples of the poor handling of infections by political systems are, unfortunately, not hard to find. there is a tradition in the united kingdom of responding to disasters by holding rigorous inquiries afterwards, which are expected to leave the public feeling "confident that a searching investigation has been held, that nothing has been swept under the carpet and that no punches have been pulled" 15 . although this is good, the pity is that the need for such inquiries seems to recur far too often. in 2001, the united kingdom suffered a serious outbreak of foot and mouth disease (fmd). millions of animals were slaughtered, and the overall costs totalled "the lesson for microbiologists is a stark one -they operate in a political environment, and it can be unhelpful." (which uses phenotypic data for typing), salmgene and pulsenet europe (both of which use pfge) in europe. the european commission has proposed the creation of a european centre for disease control and prevention 20 to standardize surveillance methods, ensure data compatability, provide scientific assessments, technical support, information to officials and to the public, and to assume responsibility for existing networks and early warning and response systems. however, it is proposed that it will only have a staff of 15. the european health commissioner david byrne explained that "it will be a hub, an intelligence centre. the core is already in place". in this way it will be utterly reliant on national laboratories, national microbiologists and national infrastructures. is this 'core' up to the job? consider the united kingdom. its core is at least as effective as that of any other large european country. in universities, for example, it has many microbiologists of international rank 21 . however, recent inquiries have identified serious problems. the recent report of the house of lords select committee on science and technology, 'fighting infection' 22 , concluded that the infectious disease services in england that are "expected to protect the population from both common and more unusual infections are under-resourced and over-stretched…there is not enough surge capacity". the report went on to predict that "without improvements we fear that this country will suffer from major epidemics". the academy of medical sciences inquiry 23 into 'academic medical bacteriology in the twenty-first century' focused on research. the inquiry concluded that although bacteriology has recently undergone a transformation with the introduction of several new techniques, "medical microbiology departments in the united kingdom, with a few exceptions, are in a state of torpor…". so microbiologists need to get their act together, and it will not do to rely on the bursts of funding and political approval that result from the panic engendered by disease outbreaks. hegel was right; history tells us that this kind of support is short-lived. sars proves the point. in july 2003, the who declared the world to be free of sars, and in august 2003, klaus stöhr, its sars research coordinator, stepped down and returned to influenza work owing to a lack of money 24 . the ability to respond rapidly to new pathogens is not cheap. the next pathogen might have a high r 0 value and be as elusive as a prion. the past tells us to be prepared. european budgets pale into insignificance compared with the $6.5 billion of the us cdc. obviously, european microbiologists have lessons to learn about getting political support! but funding is not the whole answer. the united kingdom, for example, has plenty of microbiological talent. recent experiences with bse and fmd indicate the need for big improvements in how policy makers get scientific advice. this problem persists. doctors, veterinarians, civil servants, politicians and scientists must come out of their boxes, learn to speak their different languages and communicate more effectively. if they fail, sooner or later there will be a heavy price to pay. evolution says so. coronavirus as a possible cause of severe acute respiratory syndrome identification of a novel coronavirus in patients with severe acute respiratory syndrome a novel coronavirus associated with severe acute respiratory syndrome up close and personal with sars the next influenza pandemic: lessons from hong kong world health organization multicentre collaborative network for severe acute respiratory syndrome diagnosis. a multicentre collaboration to investigate the cause of severe acute respiratory syndrome report of the uk academy of medical sciences working group on sars the merchant shipping act formal investigations 1894. (the stationery office report of the 'lessons to be learned' inquiry report when food kills responding to the challenge of communicable disease in europe the national molecular subtyping network for foodborne disease surveillance european equivalent of us centers for disease control proposed research assessment exercise: the outcome house of lords select committee on science and technology session 2002-2003 fourth report. fighting infection academic medical bacteriology in the twenty-first century search for sars origins stalls transmission dynamics of the etiological agent of sars in hong kong: impact of public health interventions infectious diseases of humans transmission potential of smallpox in contemporary populations transmission dynamics and control of severe acute respiratory syndrome smallpox in europe, 1950-1971 severe acute respiratory syndrome: lessons from singapore sars in hong kong: from experience to action the author declares that he has no competing financial interests. http://www.bt.cdc.gov centers for disease control and prevention: http://www.cdc.gov/ pulse net: http://www.cdc.gov/pulsenet/ society for general microbiology: http://www.sgm.ac.uk access to this interactive links box is free online. key: cord-276820-l7bd5y8y authors: so, winnie k.w.; chan, sophia s.c.; lee, angel c.k.; tiwari, agnes f.y. title: the knowledge level and precautionary measures taken by older adults during the sars outbreak in hong kong date: 2004-11-30 journal: international journal of nursing studies doi: 10.1016/j.ijnurstu.2004.04.004 sha: doc_id: 276820 cord_uid: l7bd5y8y abstract the study aims to examine the knowledge and the practice of the precautionary measures taken by older adults in hong kong against the outbreak of severe acute respiratory syndrome (sars). overall, more than half the participants responded correctly that droplet transmission is one of the main transmission routes of sars. those who received formal education demonstrated that they acquired greater knowledge of the sources and precautionary measures for sars. the types of precautionary measures used and the factors affecting their behaviours were discussed. the results of the study could help the health-care professionals develop appropriate health promotion and disease prevention programmes for older adults. severe acute respiratory syndrome (sars) has endangered populations worldwide (united states department of health and human service, centers for disease control and prevention, 22 may 2003) . it has infected over 8000 people and caused more than 900 deaths (hong kong sars expert committee (hksarsec), 2003) . in the early days of the outbreak, the source and mode of transmission were unknown (hksarsec, 2003) . older adults and the chronically ill were particularly susceptible to sars with a disproportionably large number of deaths occurring in these groups (hksars, 2003) . the emerging nature of sars has meant that there are few studies that have explored the perceptions of the hong kong community as they have passed through this crisis. the aim of the study is to describe the knowledge about sars and precautionary measures taken by older adults in hong kong. the world health organization (who) identified sars by name on 15 march 2003 (hksarsec, 2003 . based on clinical and epidemiological data, and laboratory test, the who updated cases definition for surveillance of sars (who, 1 may 2003) . clinical features of sars at the prodrome stage include: (1) incubation period usually 2-7 days; (2) fever (>38 c); (3) chills and rigors; and (4) other symptoms including headache, malaise, and myalgias may appear. at the later stage, respiratory symptoms including dry and non-productive cough, dyspnoea, and hypoxemia, may occur. chest radiographs may show pneumonic changes such as signs of infiltration and consolidation (who, n.d.) . it was determined that sars was mainly transmitted by respiratory droplets or by direct contact with an infected person's secretions (hong kong department of health (hkdh), 2003) . the sars epidemic in hong kong lasted almost 5 months (10 february-23 june 2003) . it gained to public awareness through the hong kong news media on 10 february 2003 as an atypical pneumonia outbreak in a nearby province (guangdong) in southeastern mainland china. the outbreak began in hong kong on 21 february 2003, when an infected professor from mainland china (the index case) arrived with his wife; they stayed in a local hotel (hksarsec, 2003) . one day after his arrival, he was admitted to a hospital in hong kong with severe pneumonia and subsequently died. this hotel was later identified as the original hong kong site from which local and international (hanoi, singapore, and toronto) transmission occurred (hksar-sec, 2003) . the first hospital outbreak began on 10 march 2003 when 11 healthcare staff was reported on sick leave from a public hospital. outbreaks in other hospitals and a housing complex were also identified in april. (major events in the sars epidemic were summarized in table 1 (hksarsec, 2003) . over the course of the outbreak, 1755 cases were reported including 300 deaths. adults 65 years of age or older were 17.6% of the sars cases; however, 63.9% of the deaths were within this age demographic and 78.2% of the deaths in this population were persons with a history of chronic illnesses (the university of hong kong clinical trial centre (hkuctc), 26 october 2003) . the aging population is growing in hong kong, as it is elsewhere. approximately 11.1% (n=747,052) of the total population is aged 65 years old or above (hkcsd, 26 october 2001a) . this situation presents many challenges for health promotion and disease prevention activities, as many of the usual methods of disseminating health information are not appropriate for this population. in hong kong, older adults can receive primary health care in both public and private health sectors. in the public sector there are two choices, the elderly health services or the general outpatient clinics, both of which provide low-cost government subsidized services and both may be used concurrently. the department of health operates the elderly health services, which provides primary health care and health promotion for older adults once they enroll (hkdh, 2001) . the annual enrolment fee is hk$110 (i.e. us$14.10/ukd 10.00) and curative services cost hk$45 (i.e., us$5.77/ukd 4.09) per consultation. older adults may also go to the hospital authority's general outpatient clinic (gopc) for medical advice and treatment (hong kong hospital authority, n.d.) . at the gopc, the treatments including x-rays and laboratory cost hk$45 (i.e. us$5.77/ukd 4.09) and medications cost only hk$10 (i.e. us$1.28/ukd 0.91). if the patient cannot afford the payment for any of these services, the service charge is waived (hkdh, 2001; hong kong hospital authority, n.d.) . in the private sector, older adults can obtain primary and secondary health care from general practitioners (grant and yuen, 1998) . usually, fees are higher and charges vary, depending on the prestige of the physician and the location of the practice. medications and laboratory tests will be charged separately and clients are usually referred to other clinical facilities for these. older adults are able to buy prescribed medications, over-the-counter western medications and traditional chinese medicines/herbs at pharmacies. during mid-may, the hong kong government launched a campaign, which was led by the chief secretary, to keep the city healthy and clean. precautionary measures to prevent the transmission of sars related to personal hygiene and environmental sanitation were publicized daily in the media as a way to minimize the possibility of becoming infected with sars. the presence of functional impairments resulting from chronic illnesses or knowledge deficits due to low literacy levels may have influenced what older adults were able to do to comply with the recommended infection control measures. thus, great concern about older adults living alone was expressed by health care providers and in the media (kong, 2003) . older adults, who may not have reacted promptly and appropriately to the government's recommendations to prevent the transmission of sars, could have been at higher risk for contracting sars and potentially for presenting a higher risk of transmission to others. understanding older adults' knowledge level and adherence to the government's recommended precautionary measures to prevent transmission of sars is an essential step in being able to design similar promotion programmes for this population in the future. the research questions examined in this study were: (1) what demographic variables influenced older adults' knowledge level, beliefs, and precautionary measures taken to prevent transmission of sars? (2) what was the knowledge level of older adults about the transmission routes of sars? (3) what were the beliefs of older adults about the possibility of becoming infected with sars? (4) what precautionary measures were taken by older adults to prevent the transmission of sars? (5) does the level of knowledge or beliefs about sars affect the types of precautionary measures used by older adults? a descriptive cross-sectional design was chosen. potential subjects were recruited from registered members of a government subsidized social service centre in the southern district of hong kong. this centre provides services such as home visits, social activities, and meals-on-wheels to the elder members of this working-class district. the eligibility criteria were: (1) aged 65 or above, (2) able to speak in cantonese, (3) no hearing impairment, and (4) reachable by telephone. initially, 295 registered members of the social service centre were contacted by telephone to determine their eligibility; 207 older adults met the criteria. of these, 163 people were willing to participate in the study (response rate=78.74%). an additional 51 participants did not answer all the questions in the questionnaire and their data were not used in the analysis; therefore, the final sample size was 112. a survey instrument developed by leung et al. (2003) was used in this study. the original survey instrument composed of 60 questions and is divided into five parts: (1) self-perceived general health status; (2) use of health services; (3) possibility of contacting diagnosed sars cases; (4) knowledge of transmission of sars and beliefs of contracting sars; (5) precautionary measures taken to prevent transmission of sars; and 6) sociodemographics. in this paper, the last three parts of the instrument were described as these parts were used for analysis and discussion. the other parts of the instrument have been described elsewhere (leung et al., 2003) . participants were asked to choose the main transmission routes of sars by answering ''yes/no'' or ''do not know'' for each of five possibilities. these five possible transmission routes reflected the current state of the knowledge about sars at the time of the survey (hkhwfb, 22 april; 20 june, 2003) . three questions aimed at determining the participants' beliefs about their likelihood of contracting sars were developed: (1) how likely is it that you will become infected sars? (2) how likely is it that you would survive if you were infected with sars? (3) how confident are you in your doctor's ability to diagnose sars? each question required a choice from a 4-point likert scale (i.e., very likely=1 to very unlikely=4) and 'do not know' response. this section was composed of 8 questions based on the widely publicized government recommended behaviours for preventing transmission of sars (hkhwfb, 17 april, 2003) . the participants indicated how often they had implemented eight precautionary measures (e.g., wearing a face mask, covering your mouth when sneezing) during the past 3 days. three of the questions asked were about hand washing behaviours (after sneezing/coughing, after touching possibly contaminated materials and the use of liquid soap instead of bar soap). the remaining three items asked about behaviours that are traditionally practised in hong kong, which required some alternation to avoid spread of sars. for example, sharing dishes at meals is common in the chinese culture. use serving spoon or chopsticks, rather than each individual each using their own chopsticks to take food from commonly shared dishes was recommended as a precautionary measure, but is not widely used (hkdh, 29 november, 2003) . another common practice is to leave the toilet seat up while flushing; however, contact with urine or feaces is one of the transmission routes, so lowering the toilet cover before flushing may prevent contaminated water from splashing out (hkdh, 29 november, 2003) . thirdly, a common serving towel is often used during meals and this practice may also transmit the disease. a 4-point likert scale ranging from 1 (always) to 4 (none) and a choice of ''do not know'' was added for the participants who did not know how to answer the questions. demographic data collected were used to examine whether the demographic variables were associated with the precautionary measures used in fighting against the infection of sars. the institutional review board of the university of hong kong/hospital authority hong kong west cluster approved this study. all the potential subjects were approached via telephone during the period between 15 and 25 may, 2003 to determine their eligibility. twenty-six nursing students from the university of hong kong were trained as interviewers. the training programme included: (1) the purpose of the research including the research questions; (2) how to conduct a telephone survey (e.g., communication techniques, how to obtain an informed consent, consistent use of the study procedure, and data recording) and (3) assessment of their learning and ability to appropriately follow the study protocols were done by observation during role play. demographic variables were grouped by gender and chi squared test performed to determine if differences occurred due to gender. correct and incorrect responses on the knowledge questions about the transmission routes of sars were grouped by participants' education level and chi squared test performed. additional chi squared analysis was done on the remaining demographic characteristics. an alpha of 0.05 or less was considered significant. mean scores on the likert scales were calculated for each of the three beliefs about sars items and for each of the eight possible precautionary measures used to prevent transmission. the 'do not know' responses for these variables were not scored or included in the means. the mean scores and the total number of 'very often' responses to the precautionary measures and were then compared to the demographic variables to determine if demographics affected the level of precautionary behaviours undertaken by the participants. information about the demographic characteristics of the participants grouped by gender is presented in table 2 . although 64.30% (n=54) of the participants were parents, 59.80% (n=65) did not live with the family and 53.30% (n=57; male=21; female=36) lived alone. more than half of the participants (55.90%) did not have any formal education. the majority of the participants (85.20%) were born outside hong kong and most of them (75.90%) were from mainland china. the percentage of participants' who gave the correct answers on the three main transmission routes of droplets, direct physical contact, and urine/feaces ranged from 42.00% to 55.90% (table 3) . demographic characteristics were compared with the participants' answers of the main transmission routes of sars. significant differences were found between education level and droplet transmission (po0.05), and between a history of visiting the mainland china within the past 3 months and direct physical contact (po0.05). participants' beliefs about the likelihood of contracting sars are presented in table 4 . more than 20% of the participants reported that they were likely or very likely to contract sars; while, 22.60% reported it was unlikely or very unlikely that they would survive if they contracted sars. overall, most participants had confidence in their doctor in terms of diagnosing sars. between 20% and 35% of participants gave the response 'do not know.' demographic characteristics were compared with the participants' beliefs about the likelihood of contracting sars and no significance was found. the frequency of taking precautionary measures varied among the participants (table 5) . means for the 3 hand-washing precautionary measures, covering the mouth while sneezing or coughing and wearing a mask were low, indicating that most participants often had practised these behaviours. in contrast, three precautionary measures (i.e., using serving spoons or chopsticks, lowering the toilet lid, and avoid using serving towels) that contradicted common cultural practices were not as frequently done. the participants who lived with their families were significantly more likely (t=2.06, po0.05) to take preventive measures than those who did not live with their family. mean scores on eight precautionary measures were compared among demographic variables. significant differences were also found between: (1) attaining education and the use of serving spoons or chopsticks at meals (po0.05); (2) place of birth and wear mask (po0.05) and wash their hands after contact with possible contaminated materials (po0.05); and (3) living with the family and to cover their mouth while sneezing or coughing (po0.05) and wash hands afterwards (po0.05). participants who received formal education were more likely to use serving spoons or chopsticks at meals. for those born outside hong kong, were more likely to wear mask and note: missing values are: use serving chopsticks=4; wash hands once contacted contaminated materials=1. a using serving spoon or chopsticks, rather than individuals each meal time. b lowering the toilet cover before flushing can prevent contaminated water from splashing out. c avoid using a common serving towel at meal time. wash hands after contact with possible contaminated materials. participants who lived with the family were more likely to cover their mouth while sneezing or coughing and wash hands afterwards. the perceptions of older adults in one district in hong kong about sars transmission routes, the likelihood of contracting and the precautionary measures taken to prevent transmission of sars were explored. the affect of demographic variables also was determined. significant differences occurred between the males and females in terms of educational attainment only, indicating that women were less educated than men. although no significance difference was found on other demographic variables, women were generally older, more likely to live without a partner, but to live with family members. more than half of the participants responded correctly by saying that transmission by droplets is one of the main transmission routes of sars. however, less than half of them provided correct answers for the rest of the questions. the timing and sequence of identifying the possible routes of sars transmission may have been a factor in whether or not the older adult acquired this information promptly. perhaps, participants had a better understanding of droplets transmission because it was the first route to be discovered and this occurred at an early stage of the outbreak (hksarsec, 2003) . it was later found that direct physical contact with sars patients and contact with urine or feaces was another route of transmission (hksarsec, 2003) . older adults usually take a longer time to acquire new knowledge and information (eliopoulos, 2001) . in addition, participants might not have received the information promptly due to a limited social network. another demographic variable that may have affected some participants' knowledge about transmission routes was the education level and travel to mainland china. when comparing the droplets transmission and education attainment, a significant difference occurred in the group of participants who answered incorrectly and who received less formal education. other significant differences were not found between knowledge and educational level. the participants' experience of traveling to and from the mainland china without contracting sars may be the reason why they did not recognize that direct physical contact was a major transmission route. knowledge about the transmission of sars may have affected participants' behaviours of taking precautionary measures. throughout the outbreak, the main route of transmission was a direct contact of the mucous membrane (eyes, nose, and mouth) with infectious respiratory droplets (weekly epidemiological record, 24 october, 2003) . under certain circumstances, contact with urine or feaces was also reported as another route of transmission. the public awareness about the ''fecal droplet'' as a transmission route of sars was increased after the community outbreak in a private housing complex in hong kong (inadequate plumbing systems, 26 september, 2003) . the who technical consultation concluded that inadequate plumbing systems also contributed to the spread of infectious diseases (inadequate plumbing systems, 26 september, 2003) . therefore, it was essential to maintain good plumbing systems and take appropriate precautionary measures such as to lower the toilet lid before flushing. however, insufficient knowledge about transmission route of sars may have affected participants' awareness of adequate precautionary measures. this was evidenced by more than half of the participants reporting that they did not lower the toilet lid before flushing. although feacal droplet transmission has been less commonly identified as the main transmission route among the infected cases when compared with respiratory droplet transmission (the university of hong kong, n.d.) , insufficient knowledge among the older adults could have led to a higher risk of contracting sars. it is important for those who develop public health messages during crisis situations, such as the one sars presented in hong kong, to identify vulnerable populations that may not be literate and to target health promotion messages in appropriate methods, which have a high probability of reaching these populations. although the proportion of sars cases among the older adult population was low (17.6%) compared with the young adult (61.2%) and the middle-aged population (21.2%), the fatality rate was the highest (63.9%) in the older adult population (hkuctc, 26 october, 2003) . the participants' responses may have reflected this reality, as many believed that it was unlikely that they would contract sars; however, they were less positive about their ability to survive if they did contract it. confidence in their physicians was expressed by over half of the participants. the rate of participants answering 'do not know' was high for all three questions in this section of the survey. this may reflect participants' uncertain knowledge level or their lack of understanding of the questions asked. these findings reinforce the importance of teaching older adults, who may be less easily reached by traditional methods due to the education level and social isolation, how to take precautionary measures and why they are important. the frequency of taking precautionary measures varied among the participants. interestingly, the means on hygiene measures related to hand washing and covering the face to prevent spread by droplets were low, indicating that these measures were practised by most participants; however, means on precautionary measures that required changing traditional cultural behaviours were much higher. most of the participants did not use serving chopsticks at mealtime and did not avoid using serving towels including their home and at restaurants. several possible explanations exist. older adults may find it harder to change ingrained cultural behaviours, they may not have known that these were important ways to prevent transmission or these behaviours may not relevant for them because they live alone; therefore, have meals alone. additional research is needed to clarify the lack of compliance to these measures. participants who were born outside hong kong may be more likely to go to mainland china or their place of birth. since they may have higher risk of infection when they travel around or their relatives and friends visit them, they may increase their alertness to take precautionary measures to prevent transmission of sars. family support has been shown to influence older people's health beliefs and self-care behaviours (hsu and gallinagh, 2001) . participants who lived with their families were more likely to use a higher number of the precautionary measures than those who did not live with their families. family support in terms of reinforcing and educating the participants to take preventive measures may influence the older adults' health behaviours. this finding supports previous findings in a similar hong kong population (hsu and gallinagh, 2001) . although no new case of sars has occurred since 12 june 2003 (hkhwfb, 23 june 2003) in hong kong, the possibility of another outbreak of sars still exists. health care professionals must understand how to deliver important health-related information to all segments of society, particularly when these types of public health crises arise. older adults, who are socially isolated or those who have low literacy rates, require health professionals to use alternative methods of dissemination of essential information; for example, inperson out-reach activities to district social services settings rather than relying on broadcast media. when acute disease outbreaks occur, a number of epidemiologic investigations are immediately undertaken; they provide essential information for managing and stopping the outbreak. however, smaller scale descriptive studies also need to be undertaken during these times to provide the needed insights concerning vulnerable populations (e.g., who is least likely to be knowledgeable) and culture-specific information (e.g., use of serving spoons/chopsticks). it is important that nurses become involved in this type of research because of the perspective they bring and that this type of research is conducted while people are still experiencing the crisis. these studies can provide nurses direction for planning and implementing appropriate health promotion and education programmes for older adults. several limitations were inherent in the methodology used in this study. the cross-sectional design provides information about one point in time. the convenience sample recruited from only one district in hong kong, limited the external validity of the findings among the older adult population. data were collected by phone interview, leaving the possibility that older adults who did not have phones may have different responses on study instruments. other variables such as social network that may have influenced older adults' beliefs or possibility of contracting sars were not included. a more representative and randomly chosen sample with the use of alternate data collection method (e.g. mailing, face-to-face interview) in future studies would improve the generalizability of findings. the telephone survey was used with content and face validity which was established by an expert panel; now that it has been used, some modifications could be made, which might clarify the participants' response so that fewer 'do not know' responses would occur. also, it is possible that the students collecting the data could have altered the study protocol causing some inaccuracy in the data unknown to the researchers. another factor that could have affected the responses given by participants was specific to hong kong culture. in chinese traditions, older adults do not feel comfortable discussing issues such as death and diseases. these traditions might hinder older adults in providing answers to some questions considered culturally sensitive (i.e., the possibility of contracting sars and the survival rate after contracting sars). the sars outbreak in hong kong presented unusual challenges for health care providers and citizens. before the outbreak had been contained, older adults' perceptions about sars and their preventative health behaviours were explored. this was the first systematic study to describe the knowledge, beliefs and sars precautions taken by the older adult population in hong kong. the participants' knowledge about the main transmission routes of sars was consistent with the precautionary measures they practised. nurses are in an ideal position to develop and implement studies of the learning needs of vulnerable sections of the population. gerontological nursing 5th edition the hong kong health care system population census: hong kong resident population aged 15 and over by quinqennial age group and educational attainment (highest level attended) population census: population by age group elderly health services. retrieved health advice for people who have been in contact with sars patients severe acute respiratory syndrome (sars)-preventive measures welfare and food bureau (hkhwfb sars bulletin. retrieved welfare and food bureau (hkhwfb) sars bulletin. retrieved welfare and food bureau (hkhwfb) sars bulletin. retrieved fees and charges for public health services sars in hong kong: from experience to action. retrieved 3 october hksars, 2003) fatality rate same as overseas the relationships between health beliefs and utilization of free health examinations in older people living in a community setting in taiwan inadequate plumbing systems likely contributed to sars transmission message from the president. the hong kong geriatrics society newsletter the impact of community psychological responses on outbreak control for severe acute respiratory syndrome in hong kong sars statistics for hong kong: specific updates for hong kong-age & gender specific fatality rate world health organization (who), 1 may 2003. case definitions for surveillance of severe acute respiratory syndrome (sars) the university of hong kong funded this study. the authors would like to thank the staff of the aberdeen kai fong welfare social center for their help during the process of subject recruitment; the nursing students of the university of hong kong for assistance during data collection; and dr. joan dodgson for assistance during preparation of the manuscript. key: cord-283537-49ic7p3u authors: chong, ka chun; goggins, william; zee, benny chung ying; wang, maggie haitian title: identifying meteorological drivers for the seasonal variations of influenza infections in a subtropical city — hong kong date: 2015-01-28 journal: int j environ res public health doi: 10.3390/ijerph120201560 sha: doc_id: 283537 cord_uid: 49ic7p3u compared with temperate areas, the understanding of seasonal variations of influenza infections is lacking in subtropical and tropical regions. insufficient information about viral activity increases the difficulty of forecasting the disease burden and thus hampers official preparation efforts. here we identified potential meteorological factors that drove the seasonal variations in influenza infections in a subtropical city, hong kong. we fitted the meteorological data and influenza mortality data from 2002 to 2009 in a susceptible-infected-recovered model. from the results, air temperature was a common significant driver of seasonal patterns and cold temperature was associated with an increase in transmission intensity for most of the influenza epidemics. except 2004, the fitted models with significant meteorological factors could account for more than 10% of the variance in additional to the null model. rainfall was also found to be a significant driver of seasonal influenza, although results were less robust. the identified meteorological indicators could alert officials to take appropriate control measures for influenza epidemics, such as enhancing vaccination activities before cold seasons. further studies are required to fully justify the associations. hong kong, a city located in the south china sea, has a humid subtropical climate with winter (december-february) temperatures that usually range from 10 to 20 °c, warm springs and autumns, and hot summers (june-september) with daytime temperatures in the low to mid 30 s and nighttime temperatures in the high 20 s. in temperate regions, influenza has a clear seasonal pattern with an exponential increase in infections in the winter, which is followed by a fade-out period of a few months. in subtropical regions, there is no sufficient understanding of the seasonal pattern of influenza and its relationship with meteorological factors. the number of epidemic peaks can differ across various subtropical regions, with the peaks usually occurring at different periods within a year [1] [2] [3] . according to the world health organization (who), influenza epidemics result in 250 to 500 thousand deaths worldwide annually [4] . in hong kong, the influenza hospitalization rate and the pneumonia and influenza (p&i) associated mortality were estimated to be 29 and 4.1 per 100,000 person-years respectively [5, 6] . hong kong was also regarded as an epicenter of pandemic influenza in southeast asia. insufficient information about viral activity creates difficulties in forecasting the disease burden and thus hampers official preparation efforts. despite numerous researches that have discovered meteorological factors associated with various activities of influenza, little is known about the drivers of transmission or its seasonal variations for different climates. a small variation in influenza transmission could result in amplification and damping of infection oscillations over time and thus sustain a seasonal pattern [7] . possible drivers of influenza transmission include meteorological variations [8] , susceptible numbers [9, 10] , and social mixing [3] . recently, shaman et al. employed a mathematical model to demonstrate that the seasonal pattern of influenza in the united states could be drawn based on the process of simulations driven by the absolute humidity [8] . this finding motivated a further investigation of potential meteorological drivers for subtropical climates. in this study, meteorological determinants that could drive the seasonal variations of influenza in hong kong were investigated by a mathematical model. we hypothesized that the transmission rates in a population-level model, as well as the infection oscillations of seasonal influenzas, are affected by meteorological factors. identification of the drivers will help to improve the understanding of influenza transmission and to alert officials to implement preemptive control measures for seasonal influenza. data on deaths from p&i from 2002 to 2009 in hong kong were obtained from the hong kong census and statistics department (figure 1 ). the mid-year population (nyear) from 2002 to 2008 was collected from the hong kong census and statistics department [11] . we separated each wave of p&i deaths by year from week 35 to week 34 of the following year. as the wave of 2007 was stopped earlier, it would start from week 35 until week 23 of 2008. the 2008 wave is from week 24 to week 16 of 2009, in order to prevent the overlap of cases after the outbreak of the 2009 h1n1 pandemic. the weekly average of meteorological parameters: air temperature, relative humidity, total rainfall, total solar radiation, wind direction, and wind speed from 2002 to 2009 were collected from the hong kong observatory. the time series of the data is shown in figure 2 . actual vapor pressure (e) was calculated as a metric for absolute humidity by the teten's formula [12, 13] : where es(ta) is the saturation vapor pressure (hpa), rh is the relative humidity (%), and ta is the air temperature (°c). the es was calculated as follows: ta ta ta e s 7 . 237 27 . 17 exp 105 . 6 ) ( the saturation vapor pressure in the teten's formula can also be obtained by the integration of clausius-clapeyron equation and is acceptable for most meteorological purposes [12, 14] . as the wind data was in the polar coordinate scale, we develop wind velocity variables in the cartesian scale that encompasses wind direction and wind speed, thus preventing the problem of northerly bearings being split at true north. two parameters of wind velocity (east-to-west and north-to-south) were used as metrics for wind data in the analysis. we extended the susceptible-infected-recovered (sir) model from chowell et al. [15] to describe the dynamic system of seasonal influenza. in this model, a population is comprised of four compartments: susceptible (s(t)); infectious (i(t)); recovered (r(t)); and dead (d(t)), at each time point t. the sir model consists of four differential equations that describes the rates of subject movements for each of the time steps. we assumed homogeneous mixing, meaning that each individual has the same chance of contacting another individual within the population. in the compartmental model, once susceptible individuals in compartment s(t) get infected, they will move to compartment i(t) and stay there for the infectious period. when the infectious period is over, the individuals in compartment i(t) will recover and move to compartment r(t) or will die and move to compartment d(t). in this model, the time-varying transmission rate per individual is βt and the force of infection for time t is βti. we denote s(t), i(t), r(t), and d(t) as s, i, r, and d as the subpopulations in each compartment for time t. the deterministic system of equations are as follows: we assumed that the length of the generation interval (gi) follows an exponential distribution with mean = 1/(γ + δ). suppose cfp is the average case fatality proportion, the mortality rate is δ = (cfp/(1 − cfp)) and δi is the influenza deaths generated by the differential equations. to make the model coefficients more comparable to each other, meteorological variables are transformed by subtracting the mean and divided by the standard deviation (sd) over their sampling period. let xt i be a particular i-th independent variable (e.g., air temperature at time t), the transformed form would be: where i x is the sample mean and σ i x is the sd for the sampling period. the meteorological effects are related to βt using the following linear component: where n is the number of independent variables. the model will determine the significant drivers to the influenza transmission rate. in the differential equations, we assumed a 5-day length of gi [16] and a 0.2% cfp [17] . to account for the variation of partial immunity to the seasonal influenza, we followed previously published procedures [15, 18] . the initial number of susceptibles in equation (3) was calculated by where d(0) was set to be the number of p&i deaths in the first epidemic week. thus, the initial number of recovered individuals can be calculated as rather than fixing a value, mid-year population (nyear) was used for each wave, so as to reduce the impact from natural mortality and birth. the weekly p&i death data was fitted to model generated deaths (i.e., δi) and the meteorological time series data consisted of the variables (xt i ) for each epidemic wave. parameters i(0), b0, b1,…,bn could be estimated by least-squares fitting to the data. as weekly data was used, t was measured in weeks. statistically significant meteorological parameters (p-value of bi < 0.05) were declared as potential drivers to seasonal variations of influenza. a stepwise variable selection approach was adopted and the best fitted model was chosen as the one with all statistically significant variables and the lowest akaike information criterion (aic) [19] : where m is the number of data points, p is the total number of parameters, and sse is the sum of square errors. instead of sampling, all possible parameter combinations were assessed by a grid search. as the absolute humidity was derived from the temperature and relative humidity, they could not be included in the same variable pool during the stepwise variable selection, due to the co-linearity problem. the variable set with temperature, relative humidity, plus other variables and the set with absolute humidity plus other variables were separately adopted in the variable selection in order to draw two final models. the best fitted model was then chosen based on aic value (lower being better). adjusted r-square (adj-r 2 ) is the measure of proportion of variance explained by the model after the parsimony adjustment. the difference of adj-r 2 between the null model and fitted model (δadj-r 2 ) was interpreted as the proportion of variance explained by the meteorological factors. we conducted a sensitivity analysis addressing two aspects: (1) model parameters: sensitivity analysis was performed by varying the length of the gi for 3 days and 7 days [16] and the cfp for 0.1% and 0.4% [17] . (2) model structure: in addition to the linear form of equation (5), a multiplicative exponential form was also adopted in model fitting to test whether this would produce different results: table 1 summarizes the results of the best fitted models with lowest aic and all statistical significant meteorological parameters. compared with the null models (βt = constant), models with meteorological parameters had better goodness of fit in terms of their aic (figure 3 ). no null model was found to be the best fitting model after the stepwise variable selection. with the exceptions of the 2003 and 2005 p&i waves, adj-r 2 was always greater than 40%, indicating that models with selected meteorological parameters explained more than 40% of the variance in p&i mortality after the adjustment of number of parameters. except for 2004, the models with significant meteorological factors could account for more than 10% of variance in addition to the null model (i.e., δadj-r 2 > 10%). for the 2008 epidemic, the meteorological parameters accounted for more than 50% of the variability in the p&i data. nevertheless, the p&i data of the 2004 epidemic could not be well explained by the best fitted models. as shown in table 1 , air temperature and rainfall were the most common significant variables driving the seasonal variations of the p&i waves from 2002 to 2008. the air temperature was negatively associated with the time-varying transmission rate βt in six of the seven epidemics; for one sd decrease in temperature, the transmission rate would increases by 4.1, 9.8, 2.6, 2.9, 5.2, 3.7 (×10 −9 ) for the years 2002, 2003, 2004, 2006, 2007 and 2008 respectively. moreover, rainfall was positively associated with the transmission intensity in five of the seven epidemic waves. when there was a sd increase in rainfall, the transmission rate would increases by 10.7, 4.5, 2.3, 9.8, 5.5 (×10 −9 ) for the years 2003-2006, and 2008 respectively. a negative association was found for 2007. surprisingly, relative humidity and absolute humidity did not show much contribution to the variance of βt among all the p&i epidemics. a sensitivity analysis was conducted to test the impact of our results from different parameter settings. in brief, varying the cfp (0.1% and 0.4%) and gi (3 and 7 days) only produced a slight effect on the goodness of fits. as shown in figures 4 and 5 , the best fitting curves were highly similar. in terms of aic and adj-r 2 , no significant differences were produced as a result of using different cfp and gi settings (tables 2 and 3 ). the fitness of the models with either cfp = 0.1% or gi = 3 days were worse than the other models in several epidemic waves. the effect of temperature was only slightly sensitive to the variation in cfp and gi. in most situations, air temperature continued to be identified as a common driver of seasonal variations. when gi = 3 days, air temperature significantly drove the variations in all epidemics. whereas the effect of rainfall was moderately sensitive to variations in cfp and gi. rainfall was identified as the significant driver of four of the studied influenza epidemics. the decrease of rainfall's significance may be due to the model variance shared with relative humidity. the meteorological variable selection was not sufficiently sensitive, even if the model structure was changed to the exponential form (table s1 ). recent studies have demonstrated that environment factors account for a proportion of the seasonality, as well as infection oscillations, of influenzas in temperate regions [8, 9] . here we used a mathematical model to explore the potential meteorological drivers for seasonal oscillations of influenza in a subtropical city, hong kong. through modulating the transmission rates by the meteorological factors in an infectious disease model, the seasonal variations of influenza infections could be well-depicted. according to our results, although no meteorological parameters dominated the seasonal variations for all epidemics, air temperature significantly modulated the fluctuations of transmission rates for most of the epidemics between 2002 and 2009. rainfall was also found to be a significant driver for most of the epidemics, although its direction of association was not unidirectional and it was moderately sensitive to changes in the model parameters. in many laboratory and epidemiological studies, air temperature is often found to be associated with influenza transmissions [1, [20] [21] [22] [23] [24] . an epidemiological study from chan et al. [1] found that temperature and relatively humidity were associated with the activity of seasonal influenza in hong kong; a cold and humid climate was related to higher activities of both influenza a and b. lowen et al. [21] conducted an experimental study using a guinea pig model to demonstrate that cold temperature favored to the spread of the influenza virus. our study extended these findings by showing that cold temperature was associated with the mechanism driving seasonal oscillations at a population level. this is perhaps due to prolonged survival of viral particles under colder conditions. nevertheless, the effect of temperature could be confounded by other factors [25] . for example, a decrease in temperature could enhance crowding at indoor activities, and would thus increase the contact, aerosol and droplet transmission intensity. in our study, we could not identify any strong evidences that absolute humidity drove the seasonal variability in hong kong, even though experimental and modeling studies have shown that absolute humidity was related to viral survivorship and was capable of driving the seasonality of influenza in temperate regions [9, 10, 25] . one possible explanation for this is that the absolute humidity in hong kong was high all year around, compared to temperate areas. like other tropical and subtropical regions, use of air conditioning is common in hong kong when the temperature is high. one could argue that, using air conditioning would lower the indoor absolute humidity and thus modulate the survivorship of the influenza virus. the effect from air exchange would indeed offset the impact of disease transmission. in addition to cold temperature, experimental studies have indicated that a low relative humidity could enhance the influenza transmission [21] . according to our results, relative humidity was not identified as a significant driver for the seasonal variation of influenza infection. this might be accounted for by the relative unpopularity of indoor heating in hong kong compared to temperate regions. moreover, the predominant mode of influenza virus spread was proposed to be different between temperate and tropical regions [26] . relative humidity would be more insensitive for transmissions by the contact route than by the aerosol route. previous studies shown that rainfall could be used as a predictor to forecast influenza infection rates for sub-tropical regions, but not in all temperate regions [27] . these authors also indicated that rainfall was correlated with seasonal influenza transmission in hong kong [20] , and this finding was in line with other tropical areas [28] . nevertheless, there remains no clear and definitive explanation for the mechanism of rainfall driving the influenza seasonality. although low temperature and dry air have been proven to be favorable for survival of viral particles [22] , no study has investigated the relationships between rainy conditions and bulk aerosol transport. one plausible mechanism is that rainfall could affect human social behaviors, such as indoor activities, and therefore influence the number of contacts and the risk of exposure to contaminated environments or infected individuals. in our study, we found that rainfall significantly drove some epidemics but that its direction of association was not unidirectional, likely due to the problem of multicollinearity, which has been investigated in our association analysis (table s2) . solar radiation could cause seasonal variations in vitamin d photosynthesis that may affect immune responses as well as playing a role in the influenza seasonality [29, 30] . the preventive efficacy of vitamin d supplementation against influenza infections has also been demonstrated in trial studies [31] . our study did not identify solar radiation as a driver for the seasonality of influenza infection. this result was not surprising because the effect of solar radiation on the population of the subtropics is not as well documented as in temperate regions. in addition, influenza a would be more likely affected by vitamin d status than influenza b [31] . this factor might confound our findings when p&i data was adopted in the study. nevertheless, the role of solar radiation in seasonality remains controversial because it has been difficult to explain the influenza dynamic in outdoor environments; most transmissions occur in indoor environments through airborne transmission or contact [32] . rather than pooling all of our data, the purpose of conducting the analysis by seasons was to investigate the meteorological effects independent of the between-season variations. the between-season effect was made up by "nuisance variables", which could result from variations of reporting rate and other potential factors that affected the susceptibility numbers [10] , such as the vaccination effectiveness. although the partial immunity of the seasonal influenza was adjusted in our analysis, some factors are difficult to measure and interpret. analysis by seasons could confound the relationship between meteorological factors and transmission rate, and thus generate inconsistency for the estimated coefficients (e.g., a negative association of rainfall in 2007). an additional analysis was conducted using the pooled data and the results were summarized in supplementary table s3 . by this approach the main finding was unchanged (i.e., a low temperature drove the influenza transmission). it should be noted that between-season effect accounted for 20% of the total variance in addition to the meteorological determinants. in our study, there is undoubtedly some degree of correlation between meteorological variables. hence, we additionally conducted a correlation analysis in which the pearson correlation coefficients and variance inflation factors (vif) were drawn from the pooled data, with the results summarized in supplementary table s2 . although positive correlations were found between temperature and solar radiation, and between rainfall and humidity, no serious effect of multicollinearity was found for any of the predictors based on a simple rule-of-thumb (i.e., all vifs were less than 3). one limitation of our study is that we only investigated the environmental drivers for disease transmission and could therefore not completely rule out confounding factors. according to some studies [8] [9] [10] 22] , some seasonal changes of host behavior (e.g., international travel [33, 34] and school holidays [35] ) might also affect the transmission dynamics. it has been shown that the closure of kindergartens and primary schools was able to reduce the disease transmission rate by around 25% for the 2009 influenza a/h1n1 pandemic. nevertheless, its effect upon the seasonal variation of influenza is controversial. some studies [10, 36] pointed out that no substantial effect on the transmission reduction could be detected when schools were closed. in addition, our results were undoubtedly affected by the demographics of the population (e.g., age and gender). subjects with different clinical status, such as chronic obstructive pulmonary disease, may also have confounded the likelihood of p&i deaths. the sufficiency of details to address these issues requires a huge effort in data collection, which remains difficult to achieve at this stage. further research is warranted to investigate the effects of seasonal social/behavior patterns. a limitation to our study is that the use of p&i mortality to represent the influenza activity may not be completely adequate and could potentially bias the findings. although some studies have preferred using p&i mortality [15] , we also analyzed the p&i excess mortality to test the robustness of the study finding. we adopted the traditional serfling approach to estimate the excess mortality [37, 38] . the serfling method is a linear regression model using harmonic terms to calculate the expected mortality in the absence of influenza virus activity. the number of excess deaths attributable to influenza was estimated as the difference between the observed and the upper 95% limit of the prediction interval of baseline deaths. the details were noted in supplementary table s4 . from the results, the principal finding was unchanged (i.e., air temperature remained a significant driver of the seasonal patterns). it should be noted that no climatic variables can be fitted into the year 2003 due to few p&i excess mortality. this might be due to the mitigation measures for the severe acute respiratory syndrome (sars) epidemic that potentially also reduced the number of influenza cases [39] . undoubtedly, it has been widely recognized that the disease severity of influenza, in terms of excess p&i deaths and hospitalization, tended to be higher in the influenza a dominant seasons than in those with influenza b as the dominant virus strains [5] . moreover, some influenza b epidemics resulted in increased hospitalizations but not increased mortality [40] . as a result, our findings might be less precise for mild influenza seasons and may not reflect the general influenza experience in hong kong. this is a common limitation in studies that employed mortality surveillance. in addition to death data, influenza-like illness (ili) surveillance has been commonly adopted as a proxy for influenza activity. nevertheless, the definition of ili failed to document significant influenza-associated morbidity and mortality [5] . as such, ili is a poor indicator of influenza activity when adopted in areas with a less defined pattern of seasonality [41] . laboratory surveillance data would be a better indicator for influenza activity but large efforts would be required to gather and collate such data. the data used in this study was only applied the retrospective fitting. further studies would have to be conducted to validate these results. for example, more data is required to extend the model application to projecting the sir curve for model validations [8] . plausible causality and potential interactions should also be justified, such as direct and indirect effects of air temperatures [22] . nevertheless, our study represents an initial step towards identifying potential meteorological determinants for driving the seasonal variations of influenza in a subtropical region. this study identified the potential meteorological drivers for the seasonal variations of influenza in a subtropical city, hong kong. results show that the cold air temperature was a significant driver for increasing the transmission intensity of seasonal influenza from 2002 to 2009. rainfall was also found to be a significant driver for some seasons, although this result was less robust. an accurate would enable officials to take appropriate control measures for influenza epidemics, such as maintaining sufficient indoor temperature and enhancing vaccination activities prior to the cold seasons. further laboratory and epidemiological studies are required to validate and justify the associations proposed here. seasonal influenza activity in hong kong and its association with meteorological variations influenza in tropical regions influenza seasonality: lifting the fog fact sheet influenza-associated mortality in hong kong influenza-associated hospitalization in a subtropical city dynamical resonance can account for seasonality of influenza epidemics absolute humidity and the seasonal onset of influenza in the continental united states shortcomings of vitamin d-based model simulations of seasonal influenza driving factors of influenza transmission in the netherlands the government of the hong kong special administrative region: table 2: population figures from mid-2002 to mid-2013. mid-year population for the computation of equivalent potential temperature. mon. weather rev über einige meteorologische begriffe comparison of algorithms for the computation of the thermodynamic properties of moist air the reproduction number of seasonal influenza epidemics in brazil centers for disease control and prevention. seasonal influenza: clinical signs and symptoms of influenza finding the real case-fatality rate of h5n1 avian influenza seasonal influenza in the united states, france, and australia: transmission and prospects for control model selection and multimodel inference: a practical information-theoretic approach modeling and predicting seasonal influenza transmission in warm regions using climatological parameters influenza virus transmission is dependent on relative humidity and temperature influenza seasonality: underlying causes and modeling theories hospital admissions as a function of temperature, other weather phenomena and pollution levels in an urban setting in china associations between mortality and meteorological and pollutant variables during the cool season in two asian cities with sub-tropical climates: hong kong and taipei absolute humidity modulates influenza survival, transmission, and seasonality high temperature (30 ºc) blocks aerosol but not contact transmission of influenza virus meteorological parameters as predictors for seasonal influenza the role of temperature and humidity on seasonal influenza in tropical areas the seasonality of pandemic and non-pandemic influenzas: the roles of solar radiation and vitamin d influenza, solar radiation and vitamin d. dermatoendocrinology randomized trial of vitamin d supplementation to prevent seasonal influenza a in schoolchildren a note on the inactivation of influenza a viruses by solar radiation, relative humidity and temperature modeling the impact of air, sea, and land travel restrictions supplemented by other interventions on the emergence of a new influenza pandemic virus assessing the impact of airline travel on the geographic spread of pandemic influenza school closure and mitigation of pandemic (h1n1) effects of school closures, 2008 winter influenza season methods for current statistical-analysis of excess pneumonia-influenza deaths the impact of influenza epidemics on mortality: introducing a severity index respiratory infections during sars outbreak the impact of influenza epidemics on hospitalizations clinical signs and symptoms predicting influenza infection this study was supported by the project (2012zx09303012-002) from the shenzhen research institute, the chinese university of hong kong, shenzhen, china. the authors thank the hong kong observatory, the hospital authority and the environmental protection department for providing the datasets for this study. the authors also thank external reviewers for their expertise advice on constructing the manuscript. william goggins and maggie haitian wang collected the data and conducted the data analysis. ka chun chong conducted the data analysis, summarized the results, and wrote the manuscript. benny chung ying zee initiated the research and revised the manuscript. all the authors read and approved the final version of the manuscript. the authors declare no conflict of interest. key: cord-021375-lca26xum authors: voelkner, nadine title: riding the shi: from infection barriers to the microbial city date: 2019-08-23 journal: nan doi: 10.1093/ips/olz016 sha: doc_id: 21375 cord_uid: lca26xum how can a microbial approach to global health security protect life? contemporary infection control mechanisms set the human and the pathogenic microbe against each other, as the victim versus the menace. this biomedical polarization persistently runs through the contemporary dominant mode of thinking about public health and infectious disease governance. taking its cue from the currently accepted germ theory of disease, such mechanisms render a global city like hong kong not only pervasively “on alert” and under threat of unpredictable and pathogenic viruses and other microbes, it also gives rise to a hygiene and antimicrobial politics that is never entirely able to control pathogenic circulation. the article draws on recent advances in medical microbiology, which depart from germ theory, to invoke an ecological understanding of the human-microbe relation. here, while a small number of viruses are pathogenic, the majority are benign; some are even essential to human life. disease is not just the outcome of a pathogenic microbe infecting a human host but emerges from socioeconomic relations, which exacerbate human-animal-microbial interactions. in a final step, the article draws on daoist thought to reflect on the ways that such a microbial understanding translates into life and city dwelling. any visitor to hong kong will realize that disinfection is an urgent and pervasive imperative in contemporary everyday life in this global city. in late 2016, hong kong was on the way to fashioning itself an antimicrobial global city. public signs on multiple surfaces including elevator buttons, escalator handrails, and floor mats duly inform the passer-by of hourly or daily sanitation. at various busy urban spaces, including mtr (metro) stations, walkways, libraries, and office and housing complex receptions, free hand sanitizer dispensers compel the passer-by to engage regularly in the act of public cleansing of the body. similarly, handbag-sized instant hand sanitizer bottles, readily available at every corner store or supermarket, with promises of killing "99.99 percent of germs"; notices of hand-washing rituals; and the donning of masks by individual city dwellers, remind residents of the private acts of virus and bacteria control. all these practices of cleansing nourish an insidious sanitizing imperative in the defense against epidemic infections deeply enmeshed with the pulsating energies of an ambitious global city. it is the experience and fear of infection and death that accompanied the recent experience of the sars (severe acute respiratory syndrome) outbreak in 2003, which precipitated this aggressive stance to potential contagions emerging in hong kong. 1 li (2014) , a scholar of asian architecture, suggests that infection control in the form of public hygiene in contemporary postcolonial hong kong manifests itself in what he has termed "infection barriers." these antimicrobial-like-that is, antibiotic-and antiviral-like-physical and mental barriers aim to prevent the virus and other microbes from settling in the city. basing his interpretation on the traditional conception of the chinese city, "infection barriers" help him to analyze the historico-aesthetics of the city's contemporary urban defense against infectious diseases. li succinctly demonstrates how public hygiene is not only governed through overt public health programs but is affectively knit into both the fabric of the urban architecture and the tissue of the city population. infection barriers take the form of structures and widespread cleansing practices, which in li's eyes render hong kong a hospital disguised as a city. like other modern infection control mechanisms, the story of infection barriers in hong kong is one of setting the human and the virus against each other, as the victim versus the menace. this biomedical polarization, in which an external pathogen threatens the healthy human body, persistently runs through the contemporary dominant mode of thinking about public health and infectious disease governance (macphail 2002 (macphail , 2014 fishel 2015; white 2015; du plessis 2017) , which is rooted in the currently accepted germ theory of disease. it renders a city like hong kong pervasively "on alert"-albeit with chinese characteristics, as will be shown below. indeed, the polarization between the human body and the virus in global health constitutes "a world on alert" (weir and mykhalovskiy 2010; lee and mcinnes 2012) . "global public health vigilance," bolstered by an extensive transnational surveillance apparatus led by the world health organization (who), caters to a world under threat of unpredictable and pathogenic microorganisms and diseases. over the past two decades, a range of global health issues have reached the highest levels of political concern, prompting states and international organizations to respond to such threats in the language, and with the arsenal, of security (rushton and youde 2015) . worryingly, it has been suggested that these security practices render citizens as patients and states as megahospitals (elbe 2010) , as is also the argument in li's description of hong kong. in her excellent "pathography" of global public health's experience with the 2009 h1n1 pandemic, macphail (2014) examines our collective fear of viruses by tracing the h1n1 influenza virus through history and sites of public health activity, particularly in hong kong. the picture she paints is also of anxiety fueling an influenza pandemic narrative in which not only is the virus misunderstood but archaic truths of influenza research dominate (cf. webster 1993) and infection control stifles the development of necessary, novel ideas of infection control (schiffman 2014; lee 2015) . the fallacy of the influenza pandemic narrative lies in it largely misunderstanding the virus and bacteria and their relation to the human. recent advances in medical microbiology have found that the human-virus relationship is not one of opposition per se but of profound entanglement. one cannot be thought without the other, leading some to theorize the figure of homo microbis (helmreich 2014) . in this understanding, few microbes are pathogenic; most are benign, some even essential to human life. indeed, viruses have been and are a vital source of new genetic information, horizontal gene transfer, and genetic diversity in the evolution of life. zoonotic viruses' ability to continuously mutate as they go about infecting hosts and exchanging genetic information renders global health strategies largely obsolete. moreover, there is an increasing realization that antimicrobial interventions such as antivirals and antibiotics are accelerating antimicrobial resistance, making infection control strategies not just obsolete but also counterproductive. thus, a rethinking of the human-virus relationship in (urban) politics and security in hong kong and global health more generally is timely. the article begins by tracing the way the global city of hong kong has been constituted as an antimicrobial city since the sars outbreak in 2003. the antimicrobial stance takes its cue from the scientifically accepted germ theory of disease. in a second step, the article explores the recent claims of medical microbiology, which profoundly depart from the germ theory to invoke an ecological or configurational understanding of the human-microbe relation. here, disease is not just the outcome of a pathogenic microbe infecting a human host but emerges from socioeconomic relations, which intensify human-animal-microbial interactions, thereby leading to pathogenesis-that is, the diseased state (lorimer 2017) . in a final step, the article draws on daoist thought and traditional chinese medicine to reflect on the ways that such an ecological understanding translates into life and city dwelling. sporadic outbreaks of h5n1 in the live bird markets; the spectre of sars whenever someone with an acute, unexplained upper respiratory tract infection is hospitalized; the occasional case of japanese encephalitis; thick, humid air that feels pregnant with microbes; the soundless, nearly invisible mosquitos ubiquitous in the lush, dense patches of forest that cover the territory. contagions seem to originate both from within and from without. (macphail 2014, 79) in early 2003, after having treated patients with atypical pneumonia in a guangzhou hospital, a medical professor arrived in hong kong from guangzhou carrying sars coronaviruses. the arrival of the coronaviruses led to the volatile outbreak of sars in hong kong. hitching a ride on the chinese professor, the pathogenic microbe family began infecting and reproducing among the large pool of hosts-that is, the hospital staff and medical students whom the chinese professor was visiting. during the professor's short stay at the metropole hotel in kowloon, before he himself fatally succumbed to sars, the viruses continued infecting seven other hotel guests, who traveled elsewhere in hong kong, singapore, vietnam, and canada. the viruses moved into the prince of wales hospital while journeying on a local hotel guest who was admitted in early march. there, they moved through the hospital, infecting over one hundred medical and nursing personnel. by early april, coronaviruses entered the housing estate "amoy gardens," where they infected and reproduced among the large pool of hosts living in and beyond this estate (lee 2003) . only a month later, coronavirus activities finally began to slow down and decrease-however, not before having also spread to a number of global cities including beijing, guangzhou, singapore, and hanoi in east asia as well as toronto. as hardy has aptly noted, "the history of the infectious diseases in modern times remains inextricably intertwined with the history of the cities that spawned them" (hardy 1993, 293; see also mcneill 1976) . this can be said too of hong kong. with the social and environmental conditions of a global city, the densely populated city is argued to have provided the necessary breeding and circulation ground for a fast-emerging disease such as sars to spread rapidly in the network of connecting global cities. 2 cities afford microbes a large pool of closely connected human hosts by which a "sustainable chain of transmission" is ensured (harris ali and keil 2008, 4) . "the city is a playground for parasites," notes guardian writer kira cochrane and adds, quoting historian of science barnett (cochrane 2014 ), there are a lot more exciting human beings they can jump on to, . . . lots more opportunities for vectoring and transmission. it's all about movement. parasites love movement. so in that sense the city is an absolutely fantastic place for them. indeed, in hong kong, according to li shiqao, the sars outbreak brought into painful realization the problem with the city's characteristically chinese urban architecture of abundance or "maximum quantities," expressed through the functional building of ever-higher skyscrapers to house more and more people within ever smaller spaces (li 2014, 28-30; also roloff 2007) . this specific urbanity of hong kong emerged with the unique political and economic circumstances that came with the arrival of large waves of mainland chinese refugees after the creation of the people's republic of china in 1949. until the 1960s, an estimated one million people were homeless in hong kong. before they were resettled in tiny spaces in public housing estates by the colonial authority, mainland chinese refugees lived in squalid squatter-settlements, which gave rise to the circulation of diseases and criminality (roloff 2007, 112) . throughout history, cities have responded in different ways to infectious diseases-from the traditional quarantine, to the development of urban hygiene infrastructure through sanitation and waste management systems (loos 1987, 45-49; melosi 1999) , to the more recent establishment of public health systems. "the whole history of urban life," argues medical historian richard barnett, "is of living with parasites and trying to get rid of them" (as quoted in cochrane 2014) . indeed, in the modernization of cities in the late nineteenth century, gandy emphasized the way technopolitical discourses became entangled with advances in the medical sciences such as disease epidemiology to influence developments in civil engineering and planning, as well as public health (gandy 2006, 15) . 3 writing about the inclusion of public hygiene in urban design and architecture, li shiqiao has spoken of "an architecture of bacteria and virus control" emerging in europe during this time (li 2014, 117-18) . this found its expression especially in urban architectural designs of whiteness (which expresses the visual act of bleaching and antisepsis) and homogenous surfaces (which express the medical practice of disinfection) (li 2014, 117-18) . 4 thus, the concern for public hygiene and microbial control has shaped (particularly western) urban architecture since the turn of the twentieth century. chinese cities, on the other hand, first encountered the late nineteenth century european discourse of urban hygiene 5 through "treaty-port cities" such as hong kong, shanghai, and tianjin, which were established to ensure the trading interests of western powers in china (rogaski 2004, 141) . 6 cities like hong kong were to participate in late nineteenth century global trade, at a time when a bubonic plague was also spreading globally. hong kong's crowded architecture rendered it a 3 gandy (2006) referred to this as the emergence of the "bacteriological city," to highlight the complex interactions between disease, water, and urban infrastructure. similar to concepts such as the "sanitary city" and the "hydraulic city" in analyzing the relationship between water and cities in the modernization of cities in late nineteenth century europe, gandy's "bacteriological city" nevertheless goes further in emphasizing the role of scientific advances such as disease epidemiology. 4 according to li (2014, 188) , whiteness symbolizes "the visual act of bleaching, the physical and metaphorical removal of dirt as an antiseptic practice." it is reflective of ventilation and light in hospital design. "shine" is produced of homogenous surfaces that find their cue from the medical practice of disinfection. 5 health strategies in china have traditionally focused on preserving the body. urban hygiene as a rationale was officially incorporated into the qing imperial administration in the early twentieth century and subsequently adopted by the communist government in 1949. urban hygiene was linked to the nationalist project of the mao regime and launched in mass campaigns to eliminate disease and pest (li 2014, 119) . 6 hong kong was created in the mid-nineteenth century as a result of the opium war between the british empire and the qing empire in china. having lost the war, the chinese emperor ceded hong kong in perpetuity to britain in 1842. under british rule, the city was a free trade center with low taxation, a character it still holds today. its british heritage is an intensely neoliberal mentality reflected in a minimum government, few controls on imports and exports, and the lack of a military arm, which laid the ground for its eventual integration into the global economy and evolution into a global city. hygienically challenged city that was particularly vulnerable to infectious diseases, leading to urban hygiene becoming a fundamental feature in governing the colonial, and eventually postcolonial, city (li 2014, 118-19) . historically, hong kong is considered a "naturally diseased space," where new influenzas emerge. with its "year-round humidity and swampy, tropical marshland," from the early times of british colonization hong kong was "seen as a reservoir-pit-of disease" (macphail 2014, 80) . a series of deadly outbreaks in the newly acquired colony led the british to set up hospitals and bring in western medical authorities to ensure there was little disruption to economic flow. the port of hong kong had become indispensable to the british economy and thus necessitated a strategic eye to controlling disease circulation (macphail 2014, 82) . in 1894, hong kong experienced a plague outbreak which led to the establishment in 1906 of what would eventually become the bacteriological institute, its first modern microbiological research center (macphail 2014, 83) . while until the 1890s hong kong's medical officials followed the widely accepted miasma theory in explaining infectious disease circulation, by the early nineteenth century, and with the establishment of the institute, the shift to germ theory in european medical circles had resolutely arrived in hong kong. using the new technology of the microscope, germ theory established that infectious diseases were not caused by atmosphericmiasma or "bad air" but by pathogenic microorganisms such as bacteria, protozoa, fungi, and viruses in the body. microbiologists proved that specific microbes, which spread from person to person, caused infectious diseases. germ theory radically changed the practice of medicine. it influenced how hospital space in hong kong and elsewhere had to be rethought toward including microbiological laboratories and isolation wards (sihn 2017). more importantly, as the accepted scientific theory of disease, which still underlies contemporary biomedicine, germ theory to this day influences and dominates modern sanitary practices and public health. the battle against sars, occurring only five years after hong kong's handover to china in 1997, revealed considerable problems both with the sino-british political arrangement of "one country, two systems" and with the city's public health governance system. sars "can be understood epidemiologically as a virus that tested hong kong's healthcare system and governance to the maximum" (baehr 2008, 147) . while a number of stringent but important measures to control the spread of infections-including isolation and home confinement, regular health checks at the border, and public information sharing-were introduced during the outbreak, the hong kong government's response was widely considered to have been severely delayed and inadequate (ng 2008, 71-73) . 7 in fact, the change in political rule and the insufficient governmental response provoked a distinct cultural reaction to sars by the hong kong people who mistrusted mainland chinese and associated hong kong officials. culturally, baehr found the "mask culture," which arose during this time, a sign of an emerging social solidarity among hong kong people in which they paid tribute to a common good by meeting one's duty not to endanger the wider hong kong community. the plague, or any other pandemic in chinese culture, is traditionally seen as a sign of evil: it "summons up the possibility of a collective death: the extirpation of the social itself" (baehr 2008, 147) . mask-wearing thus "became the quickly improvised, if obligatory, social ritual: failing to don one was met with righteous indignation, a clear sign of ritual violation" (baehr 2008, 150) . in the immediate sars aftermath, partly to be seen to regain control of the battle against infectious diseases and partly to defend its beleaguered image as "asia's world city," the hong kong government aggressively promoted a new culture of urban hygiene (roloff 2007, 74) . building on the "positive hygiene spirit" and mask-culture during the sars outbreak, the city government began working to normalize a mentality of urban hygiene in the hong kong community. shortly after the sars outbreak, it established the governmental organization team clean. its role was to regain hong kong's status as a world-class city by instituting high hygiene standards throughout the city. former chief secretary for administration, donald tsang, declared on may 28, 2003: there are problems emanating from personal hygienic habits, household hygiene unsatisfactory conditions and some environmental unhygienic problems relating to building maintenance and so on. . . . it is a monumental task but it is an important step that hong kong must go through if we aspire to be a city of the first rank and not only as a very successful international financial centre, but in fact a "clean room" in asia. (tsang 2003) the work of team clean began by identifying, defining, and clearing "hygiene blackspots" in nearly one hundred public housing estates. but the city's hygiene efforts extended not only to cleaning up buildings and surrounding infrastructure, it crucially involved changing the behavior of the people of hong kong: we believe that all efforts must begin with the self, extend to the family and the immediate neighbourhood, and then radiate throughout the entire community of hong kong before we can claim a place as a world-class city. (team clean report as quoated in roloff 2007, 97) by orchestrating mass campaigns of hygiene habits through posters, audio announcements, television broadcasts on public transportation, and the display of disinfection stations, public notices of disinfection routines, etc. and by incorporating regular and mandatory hand washing in schools, hong kong actively worked to induce an antimicrobial (sanitizing) imperative in the hong kong people. its stringent urban hygiene regime is creating hygienic world-class citizens who are to carry hong kong back into the top ranks of global cities (roloff 2007, 91) . in li's reading of the post-sars climate in hong kong, an architecture of bacteria and virus control was manifesting in distinctly chinese-style "infection barriers" in the city. historically, the chinese city is "conceived as a set of concentric corporeal defenses of the body, the family, the village, the work unit, and the state family" (li 2014, 133) . the preferred method of defense in traditional cities in china was walls. infection barriers in chinese cities like hong kong, li claims, take on some of the characteristics of the traditional walls in their concentric forms. unlike city walls or gated communities, however, infection barriers manifest according to the principles of antimicrobials. as such, in reproducing the chinese imperative of prudence in preserving the body, they defend the body by "fighting bacteria and viruses from within the tissues of architecture" (li 2014, 130) . in this way, the "monumental task" of transforming hong kong into an antimicrobial global city was underway. li concludes, "in hong kong, the hospital is poised to take over the entire city, spreading its standard practices of hand-washing, maskwearing, and temperature-taking" (li 2014, 130-31) . building on germ theorywhich posits that pathogenic microorganisms such as bacteria, protozoa, fungi, and viruses residing in human bodies spread from person to person to cause infectious diseases-an extreme urban hygiene culture emerged in this global city to prevent germs from spreading. this is not only fueling and normalizing anxieties of infection and disease as i experienced when visiting hong kong in late 2016, it may also not be achieving what it set out to do, namely, securing human life. considering recent advances in gene sequencing in microbiology, through which a "vast diversity of microbial life in, on and around the human body" (lorimer 2017, 544) has been identified as residing in complex relationality with one another, how befitting is it to fight infectious diseases by indiscriminately eliminating microbes through the use of antimicrobials and practicing urban hygiene as in the case of hong kong? what happens when the enemy is not the virus or other microbes but us (methot and alizon 2014, 778) ? like many others caught up in the emerging-disease narrative, which is based on the tenets of germ theory, the story of infection barriers is one of setting the human and the nonhuman virus against each other, as the victim versus the menace. viruses are commonly understood to be "'bad matter' to be prepared for, brought under control, and ultimately eradicated or rendered impotent" (white 2015, 145-46) . unlike the germ theory of disease, which makes a specific microbe responsible for a specific disease (e.g., the coronavirus is responsible for sars), an ecological perspective holds that microbes are not essentially pathogenic (methot and alizon 2014) . rather, as hinchliffe et al. (2016) have argued, disease emerges from the complex entanglement between the immune system of a host and the microbial milieu in and outside of the host. various scholars have noted how, much like hong kong in the face of sars, global public health programs adopt an antimicrobial stance to the control and/or elimination of infectious diseases, however, which might prove to be counterproductive in securing human life (macphail 2014; methot and alizon 2014; fishel 2015 fishel , 2017 white 2015; hinchliffe et al. 2016; du plessis 2017; lorimer 2017, 545) . at the microbial level, ecological microbiologists understand most viruses and bacteria are not pathological; they are benign and even indispensable to human life. scientists are understanding better the causes of infectious diseases, but they also "increasingly hear about beneficial microbes and the consequences of their decline or absence" (lorimer 2017, 544) . 8 causal links remain unclear and contested, however; as lorimer finds, there is "a widespread reappraisal underway in modern medicine of the salutary potential of the microbiome and the therapeutic use of microbes" (lorimer 2017, 544) . humans and microbes seem deeply and irrevocably entangled. this has led anthropologist stefan helmreich to consider the figure of homo microbis, made up of bacteria, viruses, fungi, and protozoa (helmreich 2014 (helmreich , 2015 . what are the implications of this understanding of the human body as mostly microbial to the way we fight infectious diseases in global cities and elsewhere? microbes are everywhere. apart from the ocean floors (helmreich 2009 ), soil, and deep forests, they inhabit nearly all of living matter, including mammals. humans are colonized by many viruses. this collection of viruses found in or on humans is known as the human virome, which is the viral component of the human microbiome-the assemblage of microorganisms including bacteria, fungi, protists, archaea, and viruses residing in/on the human body. only a minority of viruses infect human cells and can cause "acute, persistent, or latent infection"; some viruses are even "integrated into the human genome such as endogenous retroviruses" (wylie, weinstock, and storch 2012) , which are essential to human reproduction. 9 8 "missing microbes" have arguably been linked to several metabolic, immunological, and mental health conditions, such as allergies, obesity, inflammatory bowel disease, and depression. see velasquez-manoff 2012; blaser 2014; and lorimer 2017. 9 endogenous retroviruses are fossil viruses which "began to be integrated into the human genome some 30-40 million years ago and now make up 8% of the genome" (tugnet et al. 2013) . they may be associated with autoimmune diseases such as rheumatoid arthritis, though evidence is still limited. yet, while many mammalian viruses, such as the endogenous retrovirus, picked up mammalian genes during their evolution by subverting these "to provide a selective advantage to the virus," an opposite story can be told too. an endogenous defective retrovirus "has been sequestered to serve an important function in the physiology of a mammalian host" by encoding a protein call syncytin. syncytin has been found to be vital in placenta production, a necessary prerequisite to human reproduction (mi et al. 2000; zimmer 2012 ). there is no scientific consensus on whether viruses are living matter. 10 this is because viruses cannot live without a host cell: "they must invade and 'hijack' a cell's mechanism" so that they can produce the proteins needed for their own reproduction (macphail 2014, 8) . it is in this sense that van regenmortel and mahy (2008) have noted, viruses lead "a kind of borrowed life." their capacity to produce an effect-that is, their efficacy-, like other nonhuman matter, is "not only to impede or block the will and designs of humans but also to act as quasi agents or forces with trajectories, propensities, or tendencies of their own" (bennett 2010, viii) . by not taking seriously their efficacy to alter the course of events, however, their animating role in evolution has until very recently been overlooked. viruses have been and are a vital source of new genetic information, horizontal gene transfer, and genetic diversity in the evolution of life, including increasing and decreasing immunity to certain viruses or bacteria. 11 they have effected change on the direction of human evolution and were involved in the making of human history, most visibly in the form of plagues and diseases (mcneill 1976) . they are essential to sustaining the environment, including sea and freshwater regulation, as well as human reproduction; humans are deeply involved with viruses, in the positive and negative sense (fishel 2015, 158) . the vital role of viruses in human evolution necessitates an epistemological rethinking of evolution, as melissa a. white has noted, "from darwinian models of the 'survival of the fittest' to the phenomenon of emergent life" (white 2015, 146-47) . viruses are able to evolve very quickly, reinventing themselves by mutation and adaptation, thereby "evading immune systems and other means of eradicating them" and "surviving under conditions that would cripple or kill other organisms" (macphail 2014, 9) . essentially, viruses are "packets of pure information" in that they are protein encasements of genetic material in the form of either dna or rna. rna viruses such as influenza a (responsible, for example, for avian flu in 2003, the 1918 flu, and swine flu in 2010) evolve by engaging in "antigenetic drift" when mutating while replicating. zoonotic viruses that are able to jump species also evolve by engaging in "antigenetic shift" during which they exchange "entire genetic segments with other viruses inside a host" (macphail 2014, 9) . it is in this capacity that viruses ought to be recognized as "bioinformatic transport machines." indeed, white argues, "they ought to be considered active participants in creating the potentiality of new conditions of life through their capacity to assemble novel coalitions of genes" (white 2015, 147) . antigenetic shifts can change the surface proteins of the virus (the antigens), which are then no longer recognizable by the host's immune system, thus provoking a slower or no response to fend off the virus. virologists studying influenza a tend to focus on any incremental changes or dramatic shifts in genetic makeup to the viral antigens hemagglutinin (ha) and neuraminidase (na). it is after these specific antigens that influenza a viruses are named by their h and n numbers 10 generally, scientists apply a list of a priori criteria to decide on life. following this, according to virologists van regenmortel and mahy (2008) , viruses today are considered somewhere in-between living and nonliving. similarly, theresa macphail (2104) argues, while viruses ought to be considered to have a "certain type of nontrivial agency," they are usually seen as "liminal objects" "with some of the properties of life, yet they cannot be considered fully 'alive' while outside of a permissive host." they are "organisms at the edge of life" (rybicki 1990) . 11 in fact, historical viral traces in human dna were, until recently, controversially referred to as "junk dna." this noncoding dna makes up a greater portion of the human genome than "segments of dna that actively code for genes" (macphail 2014) . the human genome effectively consists of only two to three percent of coding dna, while the remaining ninety seven to ninety eight percent was thought to be just a "sea of genetic gibberish" with no biological function, hence "junk dna" (hall 2012) . this idea was debunked in 2012 by the encode group, which revealed that "junk dna" was in fact brimming with important genetic information. the encode group produced "a stunning inventory of previously hidden switches, signals and sign posts embedded like runes throughout the entire length of human dna." this essential noncoding dna, as macphail (2014) has noted, is evidence of past infections or "of a long-standing symbiotic partnership" with viruses. viral "junk" may even be responsible for creating new genes and for enabling the immune system to adapt to emerging infections (macphail 2002). (macphail 2014, 10). the pathogenicity of influenza a viruses is established both by their molecular makeup and their ability to cause serious illness in their host species, birds or other. a highly pathogenic virus causes severe or lethal illness in bird or other species populations. it is possible for a virus to "jump" from its host species into a human host, resulting in an usually severe and lethal infection. yet, viruses do not have "motives, or thoughts, or diabolical plans to wreak havoc to our cities"; "their function and purpose (if we can even say that they have one) is to replicate, to evolve, to survive" (macphail 2014, 11) . 12 most viruses, however, infect microorganisms including bacteria in the human microbiome (edwards and rohwer 2005) . these prokaryotic viruses "affect human health by impacting bacterial community structure and function" (relman 2015; also wylie et al. 2012) . because viruses evolve very quickly, the human virome (and thus also the microbiome) is changing all the time. each human virome is different and unique as it evolves and is formed both by preexisting immunity and viral and human genetics as well as by human lifestyle, age, geographic location, and susceptibility to disease, all of which affect individual exposure to viruses (delwart 2013) . from this perspective, diseases are not the outcome of a virus or other microbe infecting a human, as germ theory holds, but emerge from the unique constellation of political and ecological relations that affect the biological interactions of the human, the animal, and the microbe and lead to the potential development of a diseased state-that is, pathogenesis. hinchliffe et al. usefully speak of disease as "multispecies conditions configured by specific socio-ecological 'situations'" (hinchliffe et al. 2016; lorimer 2017, 545) . some scientists already seek a shift toward this ecological or configurational thinking. the emerging diseases and global health security narrative runs on the notion that the bacteria or virus is the enemy against which the global surveillance / health security apparatus must operate (weir and mykhalovskiy 2010) . this narrative rests on the germ theory of disease currently dominating microbiology/bacteriology. in her pathography of the h1n1 influenza pandemic in hong kong in 2009, macphail finds that a few "heretic" microbiologists are challenging the dominant emerging infectious diseases narrative, calling for a new epistemology in which microbes are understood not as enemies but as coinhabitants of the world (macphail 2014, 17) . hong kong biologist frederick c. leung suggests that the problem with the alarmist influenza pandemic discourse lies partly in the way viral genetic data revealed through "signature sequences" has been interpreted by leading influenza scientists such as the virologist robert webster (webster 1993) . speaking against the central focus on the h and n proteins as the key to what makes an influenza virus deadly or not in the dominant influenza surveillance and research discourse, leung and others believe that "the public health orthodoxy has become too ready to see what it has already been prepared to look for and to fear" (macphail 2014, 190) . evolutionary biologist paul w. ewald suggests that although the h and n proteins are most visible to our immune system, it is not certain that they are the reason for a strain's pathogenicity or severity (macphail 2014, 190) . ewald believes that scientists tend to confuse "sources of variation-the mutation and recombination of genes-with the process of evolution by natural selection" (ewald 2000, 22-23) . 12 hong kong biologist frederick c. leung suggests that the problem with the alarmist influenza pandemic discourse lies partly in the way viral genetic data, revealed through "signature sequences," has been interpreted by leading influenza scientists such as the virologist robert webster (1993) . speaking against the central focus on the h and n proteins as the key to what makes an influenza virus deadly or not in the dominant influenza surveillance and research discourse, leung and others believe that "the public health orthodoxy has become too ready to see what it has already been prepared to look for and to fear" (macphail 2014) . evolutionary biologist paul w. ewald (2000) suggests that although the h and n proteins are most visible to our immune system, it is not certain that they are the reason for a strain's pathogenicity or severity. ewald believes that scientists tend to confuse "sources of variation-the mutation and recombination of genes-with the process of evolution by natural selection." to date, our understanding of the human virome, benign viruses, and the virushuman relation remains limited. yet, viruses may not simply be bits of "bad matter" that slow down, disassemble, and debilitate complex systems. rather, viruses might well be approached from another vantage point altogether, as vitalizing forces in complex ecological systems in which humans are not the center. (white 2015, 149) the relation between the human and microbial communities is not antagonistic but symbiotic. while the rapid emergence of infectious diseases is creating a "world on alert," as weir and mykhalovskiy (2010) have observed, it demonstrates the frail character of the ecological balance of this vital symbiosis between humanity and their vital environment (methot and alizon 2014, 782) . the study of the biology and ecology of viruses forces us to appreciate our mostly symbiotic relationship with viruses and other microbes. it compels us to rethink how (human) life has come to be. it is not the darwinian paradigm of "the survival of the fittest" but rather an emerging paradigm revolving around a microbiological understanding of "emergent life" that explains our evolution. it also necessitates that we understand and respond to disease not as the invasion of enemy microbes but as the pathogenesis, that biological mechanism, of a unique constellation of politico-ecological relations and human-animal-microbial interactions, which gives rise to a malady. how can this emerging ontological and epistemological understanding of human life inform the governance of disease? the best defence we have against microbes is our brains, which can surely work out how to live in harmony with the microbes we know, and find non-disruptive ways of combating those that emerge in the future. (crawford 2007, 213) how do we live in harmony with the microbial world but still prevent infectious diseases from developing? how do we move from a potentially destructive antimicrobial perspective such as is embodied in hong kong to a microbial perspective in which we take responsibility for our vital relation with the microbial world? new materialist thinking (cf. hinchliffe 2007; coole and frost 2010; dolphijn and tuin 2012), which takes seriously the efficacy and ecology of human bodies and nonhuman bodies such as the virus and other microbes, invites us to examine how the human-microbe relationship can be rethought in politics. while a number of theorists have begun to conceptualize a new materialist politics and ethics within modern political theory (bennett 2010; connolly 2013; mitchell 2014) , others have looked to indigenous cosmologies, which take into account the world we share with other kinds of beings, to formulate a postanthropocentric politics (kohn 2013; tsing 2015; du plessis 2017) . the daoist cosmology underlying chinese medicine and chinese strategic thought and practices provides a first step to think in distinctly chinese ethical terms about how public health strategies in hong kong and beyond can begin to direct a human-microbial ecology to the advantage of protecting all life. daoist thought takes reality as dynamic, and the regulation of this changing reality is immanent to the interaction of the heterogeneous factors involved, thus emerging spontaneously (jullien 2004 ). sunzi's philosophy strategizes how best to direct a heterogeneous ensemble of human and nonhuman (virus, bacteria, and other nonhuman) bodies, by shifting the inherent potential, the shi, of this ecology to our advantage. in the art of war (515-512 bce), success in war was achieved not through the courage, activity, and talent of any individual fighter but through careful planning instead of actual combat. in fact, combat in chinese thought is not violence; violence is to be avoided. in medicine too, defending the body from danger demanded care for the body manifested in preservation regimes instead of reactive "western drug-and surgery-based medical practice" (li 2014, 83) . chinese medicine is about preserving rather than curing. this can be seen in its guise as a conception of food: it demands specific diet regimes developed from "observations of the characteristics of the vegetation and animals in the season." over time, it came to incorporate a puzzling spectrum of diet-based caring regimes that are still widely practiced today (li 2014, 83) . reflecting on this, medical anthropologist judith farquhar has noted of chinese medicine that it "heals in a world of unceasing transformation." this a priori dynamism in chinese medicine contrasts sharply with the modern western "world of discrete entities characterized by fixed essences, which seem to be exhaustively describable in structural terms." since motion and change are a given, they rarely require explanation with reference to their causes. according to farquhar, "one consequence of this dynamic bias in chinese medicine is that the body and its organs (i.e., anatomical structure) appear as merely contingent effects or by-products of physiological processes" (farquhar 1994 as quoted in needham 2000) . in a comparable vein, methot and alizon (2014) and others (hinchliffe and bingham 2008; lorimer 2017) have argued that pathogenesis results not from any single pathogenic microbe but from the configuration of socio-ecological relations and human-animal-microbe interactions. chinese thought, francois jullien explains, takes reality as an immanently "regulated and continuous process that stems purely from the interaction of the factors in play (which are at once opposed and complementary: the yin and yang)" (jullien 2004, 15) . reality is dynamic, and the regulation of this transformative reality-that is, the order of reality-emerges spontaneously. it is not achieved through external intervention but is "entirely contained within the course of reality, which it directs in an (inherent) fashion, ensuring its viability" (jullien 2004, 15) . two notions are central to this ancient chinese strategy: (a) the notion of a situation or configuration (xing)-that is, as a relation of forces such as are immanent to an ecology-and (b) the notion of the potential (shi) of a situation/configuration. this is commonly illustrated by "a mountain stream that, as it rushes along, is strong enough to carry boulders with it" (jullien 2004, 17) . the configuration (xing) of the mountain consists of a downward-sloping course and narrow channel, while this configuration itself gives rise to the potential (shi) for the rushing stream to carry boulders with it. thus, it is not "what we ourselves personally invest in the situation" that counts so much but rather "the objective conditioning that results from the situation" (jullien 2004, 17) . 13 jullien has argued that shi helps to "illuminate something that is usually difficult to capture in discourse: namely, the kind of potential that originates not in human initiative but instead results from the very disposition of things" (jullien 1995, 13) . bennett (2005, 461) usefully elaborates on this by explaining that "shi is the style, energy, propensity, trajectory, or élan inherent to a specific arrangement of things." for bennett, "shi names the dynamic force emanating from a spatiotemporal configuration rather than from any particular element within it." as "both the membership (of a configuration or assemblage) changes over time and the members themselves undergo internal alteration," as bennett points out, the shi or mood of a configuration also changes (bennett 2005, 461) . in margaret archer's words, everyone in the configuration "possesses autonomous emergent properties which are thus capable of independent variation and therefore of being out of phase with one another in time" (archer 1995, 66) . it is possible that an individual element such 13 biophilosophers deleuze and guattari (2004) describe something comparable when they discuss the milieu as a force field composed of nonhuman and human things (xing). not only do these heterogeneous elements constituting a milieu each entail some form of efficacy, but the milieu as a whole gives rise to a potential to effect (shi). jane bennett (2005) likewise argues that there is an agency that attaches to assemblages of human and nonhuman entities. she contends that this agency of an assemblage is comparable to the chinese strategic notion, shi. as a virus, in an antigenic shift, "becomes out of sync with its (previous) self" and forms new relations within an assemblage, "leaning towards a different set of allies" (bennett 2005, 462) . as such, the members of an assemblage "maintain an energy potentially at odds with the shi" (bennett 2005, 462) . it is for this vibrancy, according to bennett, that the agency of assemblages cannot be understood in terms of passive social structures. crucially, in chinese strategic thought, it is the shi that "can be made to play in one's favour" (jullien 2004, 17) . it is because of their variability that circumstances or ecologies can little by little be turned advantageously by the propensity or efficacy immanent to a situation. a chinese sage, according to jullien, "is inclined to concentrate his attention on the course of things in which he finds himself involved in order to deter their coherence and profit from the way that they evolve" (jullien 2004, 16) . a good general, in turn, "must be able to read and then ride the shi of a configuration of moods, winds, historical trends, and armaments" (bennett 2005, 461) . this "logic of regulated evolution" allows the potential of a situation "to develop of its own accord and to 'carry' us with it" (jullien 2004, 17) . jullien illustrates this by drawing on an old chinese proverb that captures the core idea of this thinking (mencius as quoted in jullien 2004, 16) : "even with a mattock and a hoe to hand, it is better to wait for the moment of ripening." unlike the western tradition of establishing a model that is projected onto a variable reality, according to jullien, chinese thought will concentrate on understanding how things unfold so as to discover their configuration (relationality) in order to come up with alternative ways to effect a more advantageous outcome. thus, instead of constructing an ideal form that we then project on to things, we could try to detect the factors whose configuration is favourable to the task at hand; instead of setting up a goal, we could allow ourselves to be carried by the propensity of things. (jullien 2004, 16) to ride the shi-in other words, to live harmoniously alongside and with the microbial word-we need to identity those factors whose configuration is favorable to human life. daoist ethics and chinese strategic thought lead us to embed homo microbis in an environment that is favorable to all life. as hong kong biologist frederik leung points out, the problem not only lies in the prevailing dominance of germ theory in science, it also lies in the way we relate to the animal and nonhuman world at large with which humans are so deeply entangled. he speaks against the culling of birds and animals as a response to an emerging influenza pandemic (macphail 2014, 192) . in fact, the flu is argued to be unpredictable only because influenza experts "don't understand the basic science" (leung, as quoted in macphail 2014, 193) . viruses naturally undergo constant mutation. in the case of cross-species transmission, such as the sars coronavirus which crossed over from civet cats to humans in 2003, it became clear that "highly pathogenic influenza viruses naturally burn themselves out, . . . they pose no greater risk to humanity than 'normal' influenza viruses" (macphail 2014, 193) . in fact, "the more virulent the virus, the faster the virus dies out. by evolutionary principle" (leung, as quoted in macphail 2014, 194) . leung laments the current focus on the development of influenza vaccines, since intervention through the vaccine encourages further mutation, whereas allowing the virus to take its natural course leads to its natural burn out (macphail 2014, 194) . leung's call for rethinking how we relate to the animal world echoes the recent effort to do just that in the one world one health initiative of scientists, physicians, and veterinarians worldwide to collaborate across disciplines in addressing emerging diseases. in part, this effort came about due to concerns for shared risks across human, animal, and environmental health. the focus, however, has tended to lie on the contamination and transmission of pathogens rather than on the socioeconomic relations underlying disease and health. it has been criticized for reducing diversity and for underappreciating the local, contingent, and practical engagements that first make health possible (hinchliffe 2015) . yet, it is not just how we relate to the animal world that matters. it is also about how we think about life in cities, especially as sars in hong kong in 2003 revealed, a set of absent actors-animals, microbes, airplanes, sewage systems, respiratorsthat had been banished to the margins of our conceptions of urban life, even as they actively contributed to how urban lives were composed and lived. (braun 2008, 251) the sars encounter and the post-sars politics force us to think about the microbes, animals, and many other organisms living amongst us and influencing the "social" collectives of humans. that social collective, the city, needs to be rethought on microbial terms. at the turn of the twentieth century, cities thrived on "bacteriological" (gandy 2006) and "epidemiological" conceptions of urban spaces in europe and north america. they aimed to transform urban spaces and the behavior of city people accordingly (braun 2008, 3) . in his exploration of the chinese city, li shiqiao highlights the key imperative of prudence, understood in terms of "the principle of endurance and an unknown future reward," which firmly runs through chinese conceptual thought (li 2014, 81) . he interpreted this in the post-sars situation of hong kong to be the donning of masks and ultimately striving to become hygienic subjects. yet, it seems prudent to build a microbial instead of an antimicrobial city, to rethink space and the behavior of the city people in hong kong and other (global) cities in ecological and sustainable terms, and to take into account the social-economic relations that intensify human-animal-microbial interactions. this article set out to show how a better understanding of the microbe and its deeply entangled existence with humans is crucial to conceptualizing a better approach to health and life. specifically, it argued for an inclusive approach to the virus and other microbes with which we share the world we live in over an exclusively oppositional approach to eradicating pathogenic circulation, which also eliminates or mutates benign viruses essential to human life. the article began by looking at the antimicrobial politics in chinese postcolonial hong kong since the turn of the century. it particularly focused on the notion of "infection barriers" advanced by li (2014) . li bases his analysis on the traditional conception of the chinese city and the practice of defense in walling the city off against danger. by arguing that, in the struggle against infectious diseases, contemporary practices of urban defense have taken on another guise, namely infection barriers, li is able to demonstrate how the politics of public hygiene operates not only through overt public programs but through infection barriers that are affectively knit into the fabric of the urban architecture and tissue of city dwellers. although his lens on chinese urban defenses takes seriously ancient chinese thought in the making of urban spaces, nonetheless, the politics of infectious disease remains caught up in the prevalent and dominant oppositional narrative of the human against the microbe. infection barriers set up the human and the nonhuman virus against each other, as the victim versus the menace. like antivirals and antibiotics, urban hygiene practices are never entirely able to control pathogenic circulation. this is because urban hygiene proceeds on the basis of a very narrow conception of disease, namely the widely accepted germ theory of disease. by studying the biology of microbes, it becomes possible to grasp more what the virus and other microbes are and do but particularly how they relate to the human. first, the activities of the virus escape the political designs, regimes, and practices because the virus and other microbes are forever in transformation. how then can human efforts be conceived to control pathogenic, while fostering benign, viral circulation? second, viruses play a large and essential part in making up the human. while a small number of viruses are pathogenic, the majority are benign, and some are even essential to human life. strategies to eliminate them may kill pathogenic viruses but essential viruses might also be killed off in the process. as the human cannot be thought without the virus, and attempts to alter or eliminate it (in)directly also affect the human, how might we think differently about urban spaces and public health if we consider the human and the virus not as opposed but as fundamentally interrelated? finally, the article considered daoist thought, to begin to reflect on the governance of microbes, which takes seriously their efficacy, dynamism, and deeply historical relationality with humans. from the biological vantage point of ecologies in which the virus, the human, and many other organisms are fundamentally interconnected forms that vitally depend on, but can also harm, each other, all interventions to control viruses will affect all involved, including the virus as well as the human. thus, it is in the interest of human beings to proceed with interventions to control viruses that cause the least direct or indirect harm to humans. daoist thought offers some ideas for how to strategize public health schemes, which take due consideration of this deep involvement of viruses and humans. public health schemes that develop defenses against pathogenic viral circulations, especially in a densely populated global city such as hong kong, remain important. however, there is also a need to consider and adapt the human practices that both create(d) the easy passages for viral circulation as well as forced viral mutations through the overuse of antiviral (and antibiotic) agents or vaccine development which is thought to have led to antiviral resistance. most of all, rather than fostering an oppositional relation between the human and the virus, there is a need for an appreciation of the vital role of the virus in human lives as well as of how deeply we are entangled with the virus. instead of only arming against pathogenic viral circulation by sanitizing both the urban environment and the minds of city dwellers, as in the case of hong kong, such circulation might be more usefully countered by championing an approach that proceeds on the understanding that the human irrevocably inhabits an ecosystem in which the multiplicity of life forms are deeply interrelated and dependent on each other. much like the chinese general evaluating the course of things immanent to a situation, since humans thrive on a range of other beings doing well, "an interest in human security becomes an interest in biodiversity: thriving is not a zero-sum game between different species, in fact, quite the opposite" (du plessis 2017, 18). global health projects ignore this and are struggling to deliver what they aim to do. modernity at large: cultural dimensions in globalization. public worlds realist social theory: the morphogenetic approach city under siege: authoritarian toleration, mask culture, and the sars crisis in hong kong the agency of assemblage and the north american blackout vibrant matter: a political ecology of things missing microbes: how killing bacteria creates modern plagues thinking the city through sars: bodies, topologies, politics the rise of the network society sick cities: why urban life is breeding new illness fears the fragility of things: self-organizing processes, neoliberal fantasies, and democratic activism new materialisms: ontology, agency, and politics deadly companions: how microbes shaped our history a thousand plateaus: capitalism and schizophrenia a roadmap to the human virome new materialisms: interviews and cartographies when pathogens determine the territory: toward a concept of non-human borders viral metagenomics security and global health: towards the medicalization of security plague time: how stealth infections cause cancers, heart disease, and other deadly ailments microbes the bacteriological city and its discontents journey to the genetic interior the epidemic streets: infectious diseases and the rise of preventive medicine 1865-1900 networked disease: emerging infections in the global city homo microbis: the human microbiome, figural, literal, political more than one world, more than one health: re-configuring interspecies health mapping the multiplicities of biosecurity pathological lives: disease, space and biopolitics the propensity of things: towards a history of efficacy in china how forests think: toward an anthropology beyond the human revealing power in truth global health and international relations. cambridge: polity. lee, shi hung understanding the chinese city. theory, culture and society. london: sage. loos, adolf. 1987. 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der global city routledge handbook of global health security the classification of organisms at the edge of life, or problems with virus systematics the global city reorganizing hospital space: the 1894 plague epidemic in hong kong and the germ theory transcript of the press conference with the chief secretary for administration in the conference hall of the central government offices new annexe on may the mushroom at the end of the world: on the possibility of life in capitalist ruins human endogenous retroviruses (hervs) and autoimmune rheumatic disease: is there a link? an epidemic of absence: a new way of understanding allergies and autoimmune diseases influenza global public health vigilance: creating a world on alert. routledge studies in science virus emerging view of the human virome mammals made by viruses i thank the anonymous reviewers and the editors of ips for their generous comments. i am also grateful for insightful comments on earlier versions of the article presented at the eisa convention 2017, ewis 2018, and before the irss research group, university of groningen. i am especially thankful to gitte du plessis, luis lobo-guerrero, and christopher long for thought-provoking nudges. this paper was produced under the aegis of the groningen centre for health and humanities and the aletta jacobs school of public health, university of groningen. key: cord-003171-z22ekgtv authors: babu, tara m; perera, ranawaka a p m; wu, joseph t; fitzgerald, theresa; nolan, carolyn; cowling, benjamin j; krauss, scott; treanor, john j; peiris, malik title: population serologic immunity to human and avian h2n2 viruses in the united states and hong kong for pandemic risk assessment date: 2018-10-01 journal: j infect dis doi: 10.1093/infdis/jiy291 sha: doc_id: 3171 cord_uid: z22ekgtv background: influenza a pandemics cause significant mortality and morbidity. h2n2 viruses have caused a prior pandemic, and are circulating in avian reservoirs. the age-related frequency of current population immunity to h2 viruses was evaluated. methods: hemagglutinin inhibition (hai) assays against historical human and recent avian influenza a(h2n2) viruses were performed across age groups in rochester, new york, and hong kong, china. the impact of existing cross-reactive hai immunity on the effective reproduction number was modeled. results: one hundred fifty individual sera from rochester and 295 from hong kong were included. eighty-five percent of patients born in rochester and hong kong before 1968 had hai titers ≥1:40 against a/singapore/1/57, and >50% had titers ≥1:40 against a/berkeley/1/68. the frequency of titers ≥1:40 to avian h2n2 a/mallard/england/727/06 and a/mallard/netherlands/14/07 in subjects born before 1957 was 62% and 24%, respectively. there were no h2 hai titers >1:40 in individuals born after 1968. these levels of seroprevalence reduce the initial reproduction number of a/singapore/1/1957 or a/berkeley/1/68 by 15%–20%. a basic reproduction number (r(0)) of the emerging transmissible virus <1.2 predicts a preventable pandemic. conclusions: population immunity to h2 viruses is insufficient to block epidemic spread of h2 virus. an h2n2 pandemic would have lower impact in those born before 1968. influenza pandemics may occur when influenza a viruses of animal origin with a novel hemagglutinin (ha, or h) with or without neuraminidase (na, or n) subtypes to which the human population has little or no immunity infect humans and transmit efficiently from person to person. there were 3 influenza pandemics in the 20th century. in 1918, an influenza a virus of the h1n1 subtype emerged and caused widespread disease; subsequently, h1n1 viruses caused seasonal epidemics until 1957. in 1957 a new influenza a virus of the h2n2 subtype, sometimes referred to as the "asian" influenza, emerged to cause a second pandemic, and subsequently h2n2 viruses replaced h1n1 viruses as the cause of seasonal influenza from 1957 to 1968. in 1968 a third pandemic was caused by an h3n2 virus, which replaced h2n2 viruses and continues to circulate in humans to the present day. influenza a pandemics are associated with significant mortality, morbidity, and financial burden. for example, the pandemic of 1918-1919 resulted in at least 50 million influenza-related deaths [1] , while the pandemics of 1957 (h2n2) and 1968 (h3n2) combined had estimated economic losses around us $32 billion (estimated in 1995 dollars) [2] . although not designated a pandemic, the reemergence of h1n1 in 1977 also shared some characteristics with the other 3 pandemics. the 2009 h1n1 pandemic was caused by a virus subtype that was then circulating in humans and was unexpected because it was generally assumed that that population immunity would prevent emergence of a pandemic virus of a subtype currently endemic in humans. there continues to be concern regarding the potential for new influenza a viruses to be transmitted to humans, with documented severe zoonotic disease caused by influenza a h5 and h7 infections. however, because h2n2 virus has already caused a pandemic, and h2 subtype viruses are currently circulating in wild and domestic birds [3] , reemergence of an h2n2 virus is one of the most likely scenarios for a new pandemic. anti-ha antibody, anti-na antibody, and cell-mediated immunity have all been correlated with protective immunity in both experimental animals and in humans [4] [5] [6] [7] . anti-ha antibody in peripheral blood sera, as assessed by the hemagglutination inhibition (hai) assay, has a strong correlation with protection against influenza infection and disease. although complicated by significant interlaboratory variation, an hai titer of 1:40 is generally accepted as a marker of reduced susceptibility [4] . therefore, analysis of the population level of hai antibody can be used to estimate the population susceptibility to infection [8] . for example, the seroprevalence of hai antibody to ph1n1 in individuals older than 65 years correlated with a significantly decreased influenza-associated mortality for these individuals during 2009 [9] . it has been suggested that exposure to antigenically related h1n1 influenza virus 50-60 years earlier provided older adults with some degree of immunity against the h1n1pdm09 virus [10] . similarly, individuals who were exposed to h2n2 viruses during the period from 1957 to 1968 may have persistent antibody to these viruses and be relatively protected from an emerging h2n2 virus. however, more than two-thirds of the world population in 2016 was born after 1968 [11] , suggesting that there may be substantial susceptibility to these viruses. because pandemics spread across the world within weeks after emergence [12] , much faster than the process of developing and rolling out a vaccine to the newly emerged pandemic virus, which takes >6 months [12] , attention has recently focused on developing systematic risk assessment algorithms for animal viruses of possible pandemic threat so that preemptive preparations including the development of vaccine seed strains can be initiated in advance. examples of these include the influenza risk assessment tool and the tool for influenza pandemic risk assessment [13] . an integral aspect of this risk assessment process is assessment of population immunity to the relevant virus. in this study, we evaluated population immunity using hai assays against human and avian h2n2 influenza strains in different age groups in the united states and hong kong. we then estimated the impact of existing cross-reactive hai immunity on reducing the effective reproduction number (r) of a potentially pandemic h2 subtype virus and characterized the minimum basic reproduction number (r 0 ) that such a virus must possess to cause a pandemic. samples in rochester were collected between 18 january 2010 and 14 march 2014 from nonimmunosuppressed individuals who were healthy or had stable medical conditions and were from 6 months to 80 years of age. in the united states, influenza activity typically peaks in january or february. according to the centers for disease control and prevention, in 2010-2011 influenza activity peaked in early february and in 2011-2012 it remained low through february and did not peak until mid-march. in 2012-2013, 2013-2014, and 2014-2015, influenza activity peaked in late december with some variability [14] . sera from children and adults in hong kong were collected as part of a previous serological study between 24 august 24 and 19 december 2011, prior to the winter influenza season, which typically commences around february-march in hong kong [15] . the preceding influenza season peaked in february-march 2011 and the dominant virus subtype was pandemic h1n1. two hundred ninety-five serum samples from this study were selected for testing in age strata. selection of viruses for hai testing was based on 3 phylogenetic lineages of the h2 influenza virus subtypes: human and avian eurasian lineages. viruses were selected from each lineage to represent temporal and geographic diversity. a/singapore/1/57(h2n2) and a/berkeley/1/68(h2n2) represented the human lineage, whereas a/mallard/ england/727/06(h2n2) and recent h2n2 virus isolate a/ mallard/netherland/14/07(h2n2) were of the eurasian avian lineage [16] . the a/mallard/england/727/06 virus was generated by plasmid-based reverse genetics with ha and na of a/ mallard/england/727/06 and other internal virus genes of a/ puerto rico/8/34 origin. antigenic relatedness of the selected test viruses was determined by reciprocal hai assays shown in supplementary table 1 . viruses with pandemic potential were handled in a us department of agriculture-approved animal biosafety level 3 (absl3)-enhanced facility. β-propiolactone (bpl)-inactivated virus using standard procedures for use as antigen in the hai test was prepared. the bpl-treated virus preparation was inoculated into 10-day-old hen's eggs following standard virus culture procedures to confirm complete inactivation of the virus. the antigen was then removed from the absl3-enhanced laboratory for hai analysis. in rochester and hong kong, hai studies were performed in biosafety level 2 conditions. serology hai tests were performed using turkey red blood cells in rochester, and chicken red blood cells in hong kong, otherwise the 2 laboratories used the same procedure for the test. sera were pretreated with receptor-destroying enzyme (denka seiken co ltd) and tested at a starting dilution of 1:10. hai was performed using "v" bottom microtiter plates as previously described [17] . the positive control sera used were ferret hyperimmune sera against a/kruitt/63, a/mallard/netherlands/31/2006, a/swine/ missouri/2124514/2006, a/mallard/netherlands/14/2007, and a/bakker/68 viruses, and goat hyperimmune sera against a/ japan/305/57 and a/singapore/1/57. negative controls consisted of antigen alone wells and the reagent control contained phosphate-buffered saline with red blood cells. statistical significance was analyzed using graphpad prism software (graphpad, san diego, california) using 1-way analysis of variance, followed by bonferroni post hoc analysis. p values <.05 were considered statistically significant. the reproduction number of each virus in each population was calculated as follows. we partitioned the population into n = 8 age groups (0-10, 11-20, 21-30, 31-40, 41-50, 51-60, 61-70, ≥71) and m = 4 hai titer levels (<1:20, 1:20, 1:40, ≥1:80). let p i be the proportion of population in age group and s ij be the proportion of age group i with the jth hai titer. the age distribution p i was based on the most recent census data from the united states (2012) and hong kong (2011). to estimate s s for each age group, we used bayesian inference with dirichlet y i was the number of individuals in age group i in our serologic study and x ij was the number of subjects in age group i with the jth hai titer level [18] . we assumed noninformative priors, that is, all priors were dirichlet distributions with parameters a j = 1 for j m = ¼ 1, , , and hence the joint posterior distributions of s s we assumed that an hai titer of <1:20, 1:20, 1:40, and ≥1:80 reduced susceptibility by 0%, 25%, 50%, and 75%. as such, the proportion of the population that were immune was ij j , where z j was the reduction in susceptibility conferred by the jth hai titer level (ie, , and z 4 0 75 = . ). the basic reproduction number r 0 was the largest eigenvalue of the matrix q ij { } , where q ij was the average number of secondary cases in age group i generated by an infector in age group j when everyone in the population was susceptible [19] . we constructed the matrix q ij { } using the united kingdom social contact matrix [20] because analogous data are not available from the united states and hong kong. because the immune proportion of age group i was table 1 . the demographics of the study population matched the demographics of the source population (data not shown). the results of hai testing of the sera from rochester and hong kong gave very similar results, despite the 2 populations and 2 different laboratories. the geometric mean titers (gmts) of antibody in the 2 populations against the test viruses by decade of birth are shown in table 2 . as expected, there were substantial levels of anti h2 hai antibody in the sera of persons old enough to have been infected with h2n2 viruses between 1957 and 1968, and essentially no detectable antibody in persons born after 1968. among persons born before 1957, the gmt of antibody against the early human a/singapore/18/57 was significantly higher compared with titers against the later human a/berkeley/1/68 virus, whereas in persons born from 1961 to 1970 there was a trend toward relatively higher titers against the a/berkeley/1/68 virus. titers against the avian h2n2 viruses were lower. there were no significant differences in the gmt against a/singapore/1/57, a/berkeley/1/68, or a/ mallard/england/727/2006 in sera tested in hong kong and rochester, but sera tested in rochester had significantly higher titers against a/mallard/netherlands/14/07 than the sera tested in hong kong. the prevalence of titers ≥1:40 against the test viruses is shown for sera from rochester and hong kong in persons born before the 1957 h2n2 pandemic, during the years that h2n2 circulated (1957-1968), or after 1968 is shown in figure 1 . ninetyeight percent of individuals from rochester and hong kong born before 1957 had titers ≥1:40 against the a/singapore/1/57 virus, whereas >63% of subjects born between 1957 and 1968 had titers ≥1:40. in contrast, none of those born after 1968 had titers >1:40 to a/singapore/1/1957. generally, persons born prior to 1957 had a lower prevalence of titers ≥1:40 to a/ berkley/1/1968, while the prevalence of titers ≥40 in persons born during circulation of these viruses was similar against a/ (7) 38 (13) 1951-1960 20 (13) 39 (13) 1961-1970 18 (12) 37 (13) 1971-1980 11 (7) 38 (13) 1981-1990 32 (21) 40 (14) 1991-2000 29 (19) 40 (14) 2001 or later 23 (15) 39 (13) data are presented as no. (%). singapore/57 and a/berkley/68. the prevalence of titers ≥1:40 against the 2 avian h2n2 viruses tested were significantly lower in these groups. no person born after 1968 had titer >1:40 against any of the h2 viruses. after combining the results from both populations, the cumulative distribution of antibody titers against the 4 test viruses in these 3 age groups is shown in figure 2 . eightyfive percent of individuals born in both the united states and hong kong before 1968 had hai titers ≥1:40 against a/ singapore/1/57 ( figure 2 ). more than 50% of subjects had hai titers ≥1:40 to a/berkeley/1/68 if born before 1968. the frequency of titers to avian h2n2 viruses was 62%, and 24% of subjects born before 1957 had titers of ≥1:40 to a/mallard/ england/727/06 and a/mallard/netherlands/14/07, respectively, with such titers seen in 21% and 8% of individuals born from 1957 to 1968. successful pandemic emergence and spread of a virus depends on the proportion of the population that is immune and the initial r of the potentially pandemic strain. the median r for the 1957 a/h2n2 pandemic was 1.65 (interquartile range [iqr], 1.53-1.70) [21] . to assess the impact of these age-dependent population immunity profiles on the pandemic potential of each of these viruses if they were to emerge in the human population, we computed the impact of population immunity in reducing r (figure 3 ). the current population immunity in the united states and hong kong would reduce the initial r of a/singapore/1/1957 by around 15% (12%-18%) and that of a/ berkeley/1/1968 by around 12% (10%-17%). as such, a pandemic of a/singapore/1/1957 and a/berkeley/1/1968 would be prevented if initial r of the emerging virus was below 1.18 (1.14-1.22) and 1.14 (1.11-1.20), respectively. the threshold r below which a pandemic with the avian subtype h2 viruses a/mallard/england/727/2006 and a/mallard/netherlands/14/2007 would be prevented was slightly lower. the comparability of data from 2 geographically separated areas of the world, rochester and hong kong, argues for the representativeness and generalizability of such studies that aim to assess population immunity to viruses of pandemic concern. our study suggests that those individuals born prior to or during the period of h2n2 virus circulation were more likely to have higher hai titers against the human h2n2 viruses than those born after 1968 when h2 infection in humans had been displaced by the h3n2 virus. in our study, we also confirmed evidence of cross-reactive hai antibodies to unrelated avian h2 viruses, albeit at lower prevalence and titer. the prevalence of such cross-reactive antibodies was higher in those born prior 1957 and the gmt of these cross-reactive antibodies was higher in those born prior to 1960 than in the birth cohort of 1961-1970. this is possibly because those who were infected in the early pandemic waves of the h2n2 virus in 1957-1958 were reinfected some years later by antigenically drifted h2n2 viruses, possibly broadening cross-reactive immunity. as reported by others, we also observed low hai titers <1:40 spanning across the age groups and this could be due to nonspecific data are presented as geometric mean titer (95% confidence interval). a samples in hong kong and rochester were tested at a starting dilution of <1:10 and negative tests are given an imputed value of 5. inhibition by the sera. however, we checked the sera for nonspecific agglutinins where about 7% of the samples contained nonspecific inhibitors. since the assays were run on sera which were confirmed not to contain nonspecific inhibitors, these low titers may be due to a certain type of antigen exposure that needs further investigation. sera from those born after 1963 had higher hai titers to a/berkeley/1/68 than to a/singapore/1/57 whereas the converse was true in those born before 1963. the older group of individuals who were first infected by a/singapore/1/1957like viruses likely had a boost of these titers when they were subsequently infected by later drift variants (ie, a/ berkley/1/1968-like viruses), the phenomenon known as "original antigenic sin" [22] . the broader cross-reactivity may also occur due to targeting different antigenic sites, as a recent study points out that antibody response against h2 is mainly to the receptor binding domain resulting in a greater degree of cross-reactivity whereas for h1 or h3 viruses it is the hypervariable regions of ha resulting in a lesser cross-reactivity [23] . soon after the h2n2 pandemic of 1957, studies done on sera collected prior to this pandemic were carried out and it was reported that people born prior to 1887 had detectable hai antibody to h2 viruses. it was therefore suggested that the historical pandemic that was believed to have occurred in 1889-1890 was likely caused by an h2 subtype virus [24] . this prior exposure has also shown to elicit cross-reactive antibody for h2 strains that are currently circulating in animals, potential candidate pandemic stains [25] . sera tested in rochester yielded higher titers against a/mallard/ netherlands/14/07 than the sera tested in hong kong. the differences between laboratories are not unexpected given the known laboratory-to-laboratory variation in the hai test, and what remains remarkable is the closeness of results. one technical difference between the 2 laboratories was the source of erythrocytes for the hai test; rochester used turkey erythrocytes whereas hong kong used chicken erythrocytes. it is not known if this may contribute to this difference in hai test results. an alternative reason for the discrepancy in titers between countries may be attributed to variation in vaccination rates. vaccine uptake in hong kong is lower than in the united states. potentially, repeated vaccination may increase cross-reactive antibody to this avian h2 strain. assuming that the h2 seroprevalence in rochester and hong kong reflects global population seroprevalence, we modeled the impact of such immunity on possible emergence of an h2n2 pandemic. this model was based on the candidate pandemic h2 strain originating from escape of the human adapted h2n2 virus or from the avian gene pool that acquires transmissibility in humans. we estimate that the current levels of population immunity would reduce r of a/singapore /1/1957a recent risk assessment for viruses currently known to be circulating in wild birds has been carried out and the risk of these viruses acquiring transmissibility in humans was assessed to be low; most isolates replicated in human bronchial epithelial cells and ferrets. several did transmit between ferrets by direct contact, but all has retained a preference for avian-like α2,3-linked sialic acid receptors [26] . these viruses still remain primarily in wild birds and have not been established in mammalian species including swine. our study provides the systematic assessment of the impact of human population immunity that goes toward such an overall assessment of pandemic risk. a limitation of the study is that other potential contributors to population immunity, such as cross-reactive na-inhibiting antibody, stalk-specific antibody, cell-mediated immunity, and heterosubtype reactive hai or neutralizing antibody [4] [5] [6] [7] 27] , were not assessed. furthermore, in many parts of the world (especially in developing countries), the proportion of individuals born in 1968 or later might be larger than that in rochester and hong kong. the level of immunity against a(h2n2) in these populations would be lower than that estimated here and the pandemic potential of a(h2n2) in these populations would thus be higher than estimated here. in summary, we find that levels of population immunity to h2 subtype viruses are not substantial enough to block epidemic spread of an h2 virus that had acquired efficient transmissibility between humans. furthermore, the existing levels of population immunity to h2 viruses will continue to decline with new birth cohorts being added to the human population. given that human-adapted h2n2 viruses that arose subsequent to the 1957 pandemic are present in many laboratories worldwide, these findings support the need to have preparedness for h2 viruses as a credible pandemic threat. the approach used in the case study of h2 viruses is more broadly applicable in defining the impact of population immunity to viruses to which there is some level of cross-reactive hai antibodiesfor example, swine h1 and h3 viruses and avian h9n2 viruses [27] . reliable methods for assessing population immunity are a key to reliable risk assessment of viruses for pandemic threat. it was the lack of such risk assessment of population immunity to the h1n2 triple reassortant swine viruses that led to these viruses not being recognized as potentially pandemic viruses prior to 2009; indeed, it was the triple reassortment swine ha that was the key protective antigen for the 2009 h1n1 pandemic virus. supplementary materials are available at the journal of infectious diseases online. consisting of data provided by the authors to benefit the reader, the posted materials are not copyedited and are the sole responsibility of the authors, so questions or comments should be addressed to the corresponding author. figure 3 . estimations of overall population-level immunity against h2 viruses and the potential impact of population immunity on reproduction number, using 3 potential titer cutoffs for 100% immunity. bars updating the accounts: global mortality of the 1918-1920 "spanish" influenza pandemic origin of the pandemic 1957 h2 influenza a virus and the persistence of its possible progenitors in the avian reservoir correlates of protection to influenza virus: where do we go from here? antibody to influenza virus neuraminidase: an independent correlate of protection preexisting influenza-specific cd4+ t cells correlate with disease protection against influenza challenge in humans cellular immune correlates of protection against symptomatic pandemic influenza seroprevalence to influenza a(h1n1) 2009 virus-where are we? complex patterns of human antisera reactivity to novel 2009 h1n1 and historical h1n1 influenza strains cross-reactive antibody responses to the 2009 pandemic h1n1 influenza virus vaccinate for the next h2n2 pandemic now the infection attack rate and severity of 2009 pandemic h1n1 influenza in hong kong pandemic preparedness and the influenza risk assessment tool (irat) relative incidence and individual-level severity of seasonal influenza a h3n2 compared with 2009 pandemic h1n1 adaptation of pandemic h2n2 influenza a viruses in humans world health organization. manual for the laboratory diagnosis and virological surveillance of influenza the bugs book: a practical introduction to bayesian analysis inferring influenza infection attack rate from seroprevalence data social contacts and mixing patterns relevant to the spread of infectious diseases estimates of the reproduction number for seasonal, pandemic, and zoonotic influenza: a systematic review of the literature original antigenic sin responses to influenza viruses host versus flu: antibodies win a round? pre-epidemic antibody against 1957, strain of asiatic influenza in serum of older people living in the netherlands studies on the content of antibodies for equine influenza viruses in human sera risk assessment of h2n2 influenza viruses from the avian reservoir safety and antigenicity of whole virus and subunit influenza a/hong kong/1073/99 (h9n2) vaccine in healthy adults: phase i randomised trial key: cord-275708-17cz3agx authors: babyn, paul s.; chu, winnie c. w.; tsou, ian y. y.; wansaicheong, gervais k. l.; allen, upton; bitnun, ari; chee, thomas s. g.; cheng, frankie w. t.; chiu, man-chun; fok, tai-fai; hon, ellis k. l.; gahunia, harpal k.; kaw, gregory j. l.; khong, pek l.; leung, chi-wai; li, albert m.; manson, david; metreweli, constantine; ng, pak-cheung; read, stanley; stringer, david a. title: severe acute respiratory syndrome (sars): chest radiographic features in children date: 2003-11-18 journal: pediatr radiol doi: 10.1007/s00247-003-1081-8 sha: doc_id: 275708 cord_uid: 17cz3agx background: severe acute respiratory syndrome (sars) is a recently recognized condition of viral origin associated with substantial morbidity and mortality rates in adults. little information is available on its radiologic manifestations in children. objective: the goal of this study was to characterize the radiographic presentation of children with sars. materials and methods: we abstracted data (n=62) on the radiologic appearance and course of sars in pediatric patients with suspect (n=25) or probable (n=37) sars, diagnosed in five hospital sites located in three cities: toronto, singapore, and hong kong. available chest radiographs and thoracic cts were reviewed for the presence of the following radiographic findings: airspace disease, air bronchograms, airways inflammation and peribronchial thickening, interstitial disease, pleural effusion, and hilar adenopathy. results: a total of 62 patients (suspect=25, probable=37) were evaluated for sars. patient ages ranged from 5.5 months to 17 years and 11.5 months (average, 6 years and 10 months) with a female-to-male ratio of 32:30. forty-one patients (66.1%) were in close contact with other probable, suspect, or quarantined cases; 10 patients (16.1%) had recently traveled to who-designated affected areas within 10 days; and 7 patients (11.2%) were transferred from other hospitals that had sars patients. three patients, who did not have close/hospital contact or travel history to affected areas, were classified as sars cases based on their clinical signs and symptoms and on the fact that they were living in an endemic area. the most prominent clinical presentations were fever, with a temperature over 38 °c (100%), cough (62.9%), rhinorrhea (22.6%), myalgia (17.7%), chills (14.5%), and headache (11.3%). other findings included sore throat (9.7%), gastrointestinal symptoms (9.7%), rigor (8.1%), and lethargy (6.5%). in general, fever and cough were the most common clinical presentations amongst younger pediatric sars cases (age<10 years), whereas, in addition to these symptoms, headache, myalgia, sore throat, chills, and/or rigor were common in older patients (age≥10 years). the chest radiographs of 35.5% of patients were normal. the most prominent radiological findings that were observed in the remaining patients were areas of consolidation (45.2%), often peripheral with multifocal lesions in 22.6%. peribronchial thickening was noted on chest radiographs of 14.5% of patients. pleural effusion was observed only in one patient (age 17 years and 11.5 months), whereas interstitial disease was not observed in any patient. conclusion: in pediatric cases, sars manifests with nonspecific radiographic features making radiological differentiation difficult, especially from other commonly encountered childhood respiratory viral illnesses causing airspace disease. the radiographic presentation of suspected sars cases ranged from normal to mild perihilar peribronchial thickening. the radiographic presentations, as expected, were relatively more pronounced in the sars probable cases. abstract background: severe acute respiratory syndrome (sars) is a recently recognized condition of viral origin associated with substantial morbidity and mortality rates in adults. little information is available on its radiologic manifestations in children. objective: the goal of this study was to characterize the radiographic presentation of children with sars. materials and methods: we abstracted data (n=62) on the radiologic appearance and course of sars in pediat-ric patients with suspect (n=25) or probable (n=37) sars, diagnosed in five hospital sites located in three cities: toronto, singapore, and hong kong. available chest radiographs and thoracic cts were reviewed for the presence of the following radiographic findings: airspace disease, air bronchograms, airways inflammation and peribronchial thickening, interstitial disease, pleural effusion, and hilar adenopathy. results: a total of 62 patients (suspect=25, probable=37) were evaluated for sars. patient ages ranged from 5.5 months to 17 years and 11.5 months (average, 6 years and 10 months) with a female-tomale ratio of 32:30. forty-one patients (66.1%) were in close contact with other probable, suspect, or quarantined cases; 10 patients (16.1%) had recently traveled to who-designated affected areas within 10 days; and 7 patients (11.2%) were transferred from other hospitals that had sars patients. three patients, who did not have close/hospital contact or travel history to affected areas, were classified severe acute respiratory syndrome (sars) was first identified in guangdong province in southern china in november 2002 [1, 2] . sars is a severe atypical pneumonia associated with substantial morbidity and mortality rates in adults, now believed to be caused by a novel coronavirus [3, 4, 5, 6, 7, 8] . outbreaks have been reported in asia, europe, north america, and australia [9] . as of 26 september 2003, a cumulative total of 8,098 probable cases and 774 deaths have been reported from 29 countries [10] . to date, the outbreak of sars in canada has resulted in 251 probable cases and 43 deaths; singapore had 238 probable cases and 33 deaths; hong kong had 1,755 probable cases and 299 deaths [10, 11] . the diagnosis of sars currently rests upon clinical and epidemiological criteria as defined by the world health organization (who), since definitive tests for sars have not yet been developed and validated [12] . a suspect case is disease in a person with documented fever (temperature >38°c), one or more respiratory tract symptoms (including cough, shortness of breath, difficulty breathing), and close contact with a person believed to have had sars (living with, caring for, or having had direct contact within 10 days of onset of symptoms, exposure to respiratory secretions and/or body fluids of a person with sars) and/or a history of travel (within 10 days of onset of sars symptoms) to an endemic geographic area with documented foci of illness transmission. a probable case is defined as a suspect case with chest radiographic findings of pneumonia, acute severe respiratory distress, or an unexplained respiratory illness resulting in death with autopsy results demonstrating the pathology of acute respiratory distress syndrome without an identifiable cause. probable cases of sars are similar to suspect cases, but often have a more severe illness, with progressive shortness of breath and difficulty breathing, as well as radiographic signs of atypical pneumonia [13, 14, 15] . descriptions of the sars outbreaks in adult patients from toronto [7, 16, 17, 18] , singapore [19, 20] , and hong kong [21, 22, 23, 24, 25] have recently been reported. to date, the clinical and radiographic findings in children suspected of having sars have been limited or combined with adult data [26, 33] . this article presents the initial chest radiographic findings collated from 62 children diagnosed as probable or suspect sars cases during the recent sars outbreak in toronto, singapore, and hong kong. the limited previously published material is included to provide as complete a pediatric series as possible. a total of 62 pediatric patients, fitting the who case definition [1] or a modification of this definition [33] for suspect or probable sars, admitted to hospital from late february 2003 to mid-may 2003, were included in this report. patients in this report were admitted to one of the following five hospitals: (a) the hospital for sick children (hsc) in toronto; (b) tan tock seng hospital (ttsh) in singapore; (c) prince of wales hospital (pwh), (d) princess margaret hospital (pmh), or (e) queen mary hospital (qmh) in hong kong. we abstracted data retrospectively from review of patientsõ medical records for patient demographics, exposure category, clinical presentations, and radiological findings. the hospitalization period (length of stay in the hospital) for these patients varied from 2 days to 1 month after the onset of symptoms. the exposure category included the possible mode of transmission through close contact, health-care setting, and/or travel to, or living in, endemic areas. clinical presentations were reviewed for as sars cases based on their clinical signs and symptoms and on the fact that they were living in an endemic area. the most prominent clinical presentations were fever, with a temperature over 38°c (100%), cough (62.9%), rhinorrhea (22.6%), myalgia (17.7%), chills (14.5%), and headache (11.3%). other findings included sore throat (9.7%), gastrointestinal symptoms (9.7%), rigor (8.1%), and lethargy (6.5%). in general, fever and cough were the most common clinical presentations amongst younger pediatric sars cases (age<10 years), whereas, in addition to these symptoms, headache, myalgia, sore throat, chills, and/or rigor were common in older patients (age ‡10 years). the chest radiographs of 35.5% of patients were normal. the most prominent radiological findings that were observed in the remaining patients were areas of consolidation (45.2%), often peripheral with multifocal lesions in 22.6%. peribronchial thickening was noted on chest radiographs of 14.5% of patients. pleural effusion was observed only in one patient (age 17 years and 11.5 months), whereas interstitial disease was not observed in any patient. conclusion: in pediatric cases, sars manifests with nonspecific radiographic features making radio-logical differentiation difficult, especially from other commonly encountered childhood respiratory viral illnesses causing airspace disease. the radiographic presentation of suspected sars cases ranged from normal to mild perihilar peribronchial thickening. the radiographic presentations, as expected, were relatively more pronounced in the sars probable cases. keywords chest ae severe acute respiratory syndrome (sars) ae radiography ae ct ae children the following signs and symptoms: fever, chills, body ache, cough, sore throat, rhinorrhea, dyspnea, tachypnea, crackles, headache, dizziness, hypoxemia, malaise, myalgia, rigor, lethargy, and gastrointestinal symptoms including vomiting and diarrhea. microbiological investigations from the toronto site (hsc, n=15) included nasopharyngeal swabs for direct antigen detection, and culture of respiratory viruses including respiratory syncytial virus, influenza a and b, parainfluenza 1, 2 and 3, and adenovirus. we also included the following investigations: a nasopharyngeal swab for sars-associated coronavirus reverse-transcriptase polymerase chain reaction (rt-pcr), a throat swab for bacterial culture and mycoplasma pneumoniae pcr, a stool sample for electron microscopy, and two blood cultures. the rt-pcr test used to detect the sars-associated coronavirus in toronto was developed in-house. from the hong kong sites (pwh and pmh, n=16), paired acute and convalescent sera/feces samples were collected from some patients. the microbiological investigations included viral culture, stool and throat gargle rt-pcr, bacterial culture of blood and sputum, serology, and nasopharyngeal aspirates (npa) for virology. the npa was assessed by rapid immunofluorescent antigen detection for influenza a and b, parainfluenza types 1, 2 and 3, respiratory syncytial virus, and adenovirus. the rt-pcr test used to detect the sars-associated coronavirus in hong kong was developed in-house. at the time of this study, patients from singapore were managed on the basis of clinical, epidemiological, and radiographic evidence. microbiological tests were not routinely performed on any patient. all available initial and follow-up chest radiographs obtained in these patients were interpreted by experienced pediatric or general radiologists. these radiographs were not reviewed at a central site, instead the films were read at each participating center independently. the chest radiographs were reviewed for the presence of standard radiographic findings of pulmonary infection in children. specific evaluation criteria included: the presence or absence of pulmonary overinflation, bronchial wall thickening, interstitial disease, atelectasis, airspace disease (ground-glass opacification, patchy, focal or lobar consolidation), nodules, pleural effusion, air bronchogram, hilar adenopathy, and extrapulmonary air. other radiological features, if present, were also noted. a combination of posteroanterior, lateral, and portable anteroposterior views was available. a standard radiographic technique was utilized, with most patients having portable examinations with anteroposterior views only. if a thoracic ct was obtained, the ct findings were also reviewed. a standard ct or thin-section ct technique was utilized as described elsewhere [27] . from a total of 101 cases, 39 patients (from all the study sites) initially under suspicion of having sars were excluded from the study, as another etiology (other pneumonias or other underlying disease) was determined. patients were excluded from this study if they had another known disease potentially affecting the chest radiographic appearance. institutional review board approval was obtained from two sites, toronto and hong kong, and was waived for singapore. a total of 62 pediatric patients were diagnosed with sars (suspect=25; probable=37) in toronto, singapore, and hong kong. demographic data, exposure category, clinical presentation, and radiographic findings of these cases from the various sites are shown in tables 1, 2, 3 and 4 with an overall summary shown in table 5 . patient ages ranged from 5.5 months to 17 years and 11.5 months (average, 6 years and 10 months) with a female-to-male ratio of 32:30. forty-one patients (66.1%) were in close contact with other probable, suspect, or quarantined cases; 10 patients (16.1%) had recently traveled to the affected areas; 7 patients (11.2%) were transferred from other hospitals with admitted sars patients. three patients from the hong kong patient cohort did not have close contact, hospital contact, or travel history to affected areas, but were included in the study on the basis of their clinical signs and symptoms and because they were living in an endemic region. these patients were classified as probable sars cases, which was possibly community acquired. in toronto, the patient population (n=15) average age was 6 years with a female:male ratio of 3:2. amongst these patients, close contact (60%) with sars probable, suspect, or quarantined family members was the most common mode of possible sars exposure. potential sars exposure through hospital contact or travel to who-defined affected areas within 10 days prior to onset of symptoms was observed in 26.7% and 13.3% of patients, respectively. from the various hospital sites in singapore, the patient population (n=30) average age was 4 years and 11 months with a femaleto-male ratio of 7:8. the mode of possible sars exposure through close contact (73.3%) was greater than exposure due to travel (26.7%). in hong kong, the patient population (n=17) average age was 9 years and 6 months with a female-to-male ratio of 9:8. the mode of possible sars exposure through close contact (58.8%) was also high amongst these patients, whereas three patients (17.6%) did not have a history of contact or travel exposure but were living in an endemic region. overall, close contact with a known sars case (family member) was the most common mode of possible sars exposure accounting for 40 cases (66.1%). health-care settings accounted for seven cases (11.2%) including transfer from other hospitals and, in one of these cases, a visit to a family physician. travel to an endemic region was seen in ten cases (16.1%), whereas no known mode of sars exposure was identified in three cases. the most common clinical manifestations noted from toronto patients were fever (100%), cough (53.3%), rhinorrhea (33.3%), and diarrhea (26.6%). from the singapore patient cohort, fever (100%) and cough (66.7%) were the most common clinical features. from the hong kong patient cohort, in addition to fever (100%) and cough (64.7%), myalgia (47.1%), chills (41.2%), rhinorrhea (29.4%), and rigor (29.4%) were also commonly reported. overall, the most common clinical presentation was fever with a temperature over 38°c (100%), cough (62.9%), rhinorrhea (22.6%), myalgia (17.7%), chills (14.5%), and headache (11.3%). other reported findings included sore throat (9.7%), diarrhea (9.7%), rigor (8.1%), and lethargy (6.5%). in general, fever and cough were the most common clinical presentation amongst younger pediatric sars cases (age<10 years), whereas, in addition to these symptoms, headache, myalgia, sore throat, chills, and/or rigor were reported in older patients (age ‡10 years). only one teenager with probable sars (toronto, age 17 years and 11.5 months) developed respiratory distress and required oxygen. from the toronto patient cohort (n=15), the nasopharyngeal swab specimens were negative for the sars-associated coronavirus (toronto rt-pcr test). however, most of the patients who had clinically defined sars and were tested for microbiological agents (n=10) in hong kong had either serological or rt-pcr evidence of infection for the sars-associated coronavirus (hong kong rt-pcr test). four patients were rt-pcr positive on npa; two patients were serology positive; stool rt-pcr and throat gargle rt-pcr were positive for three patients; and stool rt-pcr was positive in one patient. all three sars cases with no history of contact in hong kong were found to have positive paired acute and convalescent serum test results. the sars-associated coronavirus was isolated from npa in two patients and only one patient out of the ten included for microbiological testing was negative for rt-pcr. the chest radiographs of 35.5% of patients were normal. the most prominent radiological findings in the remaining patients were patchy infiltrates, opacities, and/ or areas of consolidation (45.2%) with multifocal lesions observed in 22.6%. the location of consolidation was predominantly within the lower lobes. perihilar peribronchial thickening was noted in 14.5% of cases. figures 1, 2, 3, 4 and 6 show the various common radiographic findings. pleural effusion was observed only in one patient, whereas interstitial disease was not observed in any patient. hilar adenopathy, extensive pleural effusions, lung abscess, pneumatocele, or pneumothorax were not seen. these radiographic findings resolved in the majority of cases within a 1-week interval. ct scans for some patients were obtained only in hong kong (table 4) . ct scans showed unifocal or multifocal, central and/or peripheral regions of consolidation and/or ground-glass opacities. figures 5 and 6b show ct scans obtained from two patients. in general, ct showed more extensive airspace consolidation and ground-glass attenuation than chest radiographs, but no evidence of hilar adenopathy, pneumothorax, or pneumomediastinum was noted in our patient population. as far as we know, to date no pediatric deaths have been reported amongst toronto, hong kong, or singapore patient cases that were included in this study. pneumonia is one of the most common serious infections of childhood with significant morbidity and mortality rates worldwide. in the united states, the reported mortality rate due to pneumonia and influenza for [28] . based on prospective data collected from pediatric studies of community-acquired lower respiratory tract infections, viral respiratory tract pathogens are responsible for the majority of diagnosed infections in the developed world, particularly in the younger age group [29, 30, 31, 32] . sars is a new viral disease that must now be considered when faced with a child with fever and respiratory symptoms. highly contagious, sars was first identified in guangdong province in southern china late last year. as in other epidemics of the past, trade and travel have sped up sars transmission between disparate populations. the impact upon affected regions has been significant, both medically and economically. since sars was first identified, a total of 368 casualties and 2,212 probable sars cases have been reported from canada, singapore, and hong kong with additional thousands quarantined. to date there have been limited reports in children [26, 33] . the great majority of sars victims have been adults [7, 16, 17, 18, 21, 23, 27, 34, 35, 36, 37] with a fatality rate of 9.6% based on who surveillance data [10] . over the past few months remarkable progress has been made in defining the clinical features and etiology of sars. microbiologic evaluation has now revealed a fig. 1 a 34 -month-old boy with probable sars from household contact. clinical presentation included fever (41°c), cough and rhinorrhea. initial chest radiograph revealed mild perihilar peribronchial thickening and patchy, multifocal infiltrates at the left lung base fig. 2 a 29-month-old boy with probable sars from household contact presented with fever (38.2°c) and cough. initial chest radiograph showed a focal area of airspace opacification in the right lower lobe fig. 3 a 16 -month-old girl with probable sars with recent travel history to guangdong province, south china, presented with fever and cough. initial chest radiograph revealed a patchy opacity in right upper lobe and a mild peribronchial thickening extending into the lower lobes. subsequent radiographs showed decreased opacity within the right upper lobe and an increased density within the right infrahilar region fig. 4 a 17 -year-old girl with probable sars exposed through household contact. signs and symptoms of the patient at admission included fever (40.1°c), cough, dyspnea, hypoxemia, and bilateral crackles. the initial radiograph revealed dense airspace disease involving the right middle lobe and posterior left lower lobe novel coronavirus as the etiologic agent of sars [3, 5, 8, 38, 39] . clinically, children show similar symptoms to those already reported in adults including fever, cough, headache, and myalgia. however, dyspnea, malaise, and hypoxemia are less commonly encountered in childhood. the typical pediatric presentation is rapid onset of high fever with cough. compared with adults, children with sars seem to have a milder clinical course, especially for those under the age of 10 years [26, 33] . currently, the who case definitions for suspect or probable sars rely upon patient contact, travel history to endemic areas within 10 days, and commonly encountered clinical and radiographic criteria. many children that were initially suspected of having sars were eventually excluded upon availability of the results of standard microbiologic investigations. for example, at one institution (toronto) we had ten children present with clinical and epidemiological criteria consistent with a diagnosis of suspect or probable sars, but who were later shown to have other infections. these other infections included viral respiratory tract infections such as adenovirus, influenza (a and b) , parainfluenza, and respiratory syncytial virus and bacterial infections, such as streptococcus pneumoniae bacteremia. further, using the current criteria, there are likely to be false-negative cases as well. some children may be inappropriately thought not to have sars due to our incomplete knowledge of the full extent of sars clinical presentations, especially at the early or mild stage of the disease. a few adult close contacts have reported a mild, febrile illness without definite respiratory signs or symptoms suggesting that the illness might not always primarily involve the respiratory tract. this appears to be true in children as well, with some in our study having minimal or no clear respiratory symptoms and a nonspecific febrile illness despite extensive contact history [33] . although gastrointestinal symptoms are usually absent, some children reported vomiting and/or diarrhea [22, 26, 33] , while several adults have presented solely with severe abdominal pain. the relative infectivity of these patients remains unclear and until more is learned, caution and full infection control procedures are recommended. significant effort still lies ahead to fully characterize the signs and symptoms of sars across all ages and especially to develop reliable means of differentiating it from other lower respiratory tract infections. accurate identification of the causative agent in these situations should hopefully lead to more specific and sensitive diagnostic tests to simplify sars diagnosis. preliminary work with rt-pcr tests for sars is promising; however, it is not yet clear how accurate these tests are, particularly for commonly used nasopharyngeal samples as shown in this study and by peiris et al. [37] . radiographic findings in children may be normal or may demonstrate airspace disease, which may present as ground-glass opacities or focal, lobar, or multifocal consolidation. other radiographic findings included perihilar peribronchial thickening and linear atelectasis. we did not consider mild peribronchial thickening as pneumonia and these children were classified as suspect sars. as in adults, regions of airspace disease predominated in the lower lobes, especially peripherally, but were also seen elsewhere. distinguishing between atelectasis and consolidation can be difficult fig. 5 high-resolution ct of a 13-year-old girl who presented with persistent fever for 1 week with chills, rigors, rhinorrhea, and myalgia. there is mixed airspace consolidation and ground-glass opacity in the left lower lobe fig. 6a , b a 16-year-old girl, who presented with fever, chills, rigors, myalgia, and headache for 2 days. she had a history of hospital contact with probable sars patients. a chest radiograph on admission is unremarkable with no definite consolidative change. b high-resolution ct on the same day shows a focal consolidation at the right lung base in daily practice. areas of segmental atelectasis are common in viral disease and may often be multiple and fleeting. adenopathy, infrequently encountered with viral diseases [40] , was not seen in our patients. with clinical recovery, complete clearing of chest radiographs were noted in our patients similar to other reports [35, 36] . it is still unclear what the long-term sequelae of sars infection will be on subsequent lung development. in adults, radiographic findings may be more extensive, and also include unilateral or multifocal and bilateral patchy or confluent areas of airspace consolidation or ground-glass opacities [22, 35, 36, 41] . chest radiographs may be normal during the early febrile prodrome or with mild disease and may progress later on. opacities are most often peripheral or mixed central and peripheral [22, 41] . in the more advanced stage of the disease, a widespread ground-glass opacification (likely representing progression to ards) and diffuse patchy or lobar consolidation have also been reported [35, 36] . interstitial disease is rare and pleural effusion is uncommon. resolution may occur early on. diffuse miliary disease has been reported in one patient [21] . ct findings in adults with probable sars have shown predominantly subpleural focal consolidation or ground-glass opacities [21, 27, 36, 37] . these findings occur predominantly in the lower lobes and may be unifocal or multifocal. less common findings include thickening of interlobular septa and intralobular interstitium, the crazy paving pattern, and spontaneous pneumomediastinum. air bronchograms may be seen. mediastinal nodes, effusions, or central pulmonary emboli have not been observed. chest ct has been helpful in differentiating suspect from probable cases by demonstrating lung findings 1-2 days before they become radiographically apparent [27] . our study showed similar ct features to those previously described with unifocal and multifocal consolidation and ground-glass opacities. we did not observe any of the less common features such as the crazy paving pattern or septal thickening. ct scans were obtained at one site only and were generally used to document early lung findings when the initial chest radiograph was normal or equivocal and suspicion for sars was high. ct scans of the pediatric chest are not routinely needed in evaluation of lower respiratory tract infection, but are generally reserved for investigation of suspected complications including pulmonary abscess, empyema, pulmonary necrosis, recurrent infection, or in immunocompromised individuals [42] . since the clinical presentation in most of our pediatric cases was mild, ct was not considered necessary in two sites (toronto and singapore). for the hong kong patients (pwh and pmh patient cohort), chest ct was used for patients with suspected sars but with normal chest radiographs, patients with a moderate to severe clinical course of the disease, and patients without contact history. use of ct may be justified if management depends upon positive lung findings; however, suspect sars patients were also admitted and managed in a similar fashion to those with positive chest radiograph findings. it is still unclear whether the infectivity of suspect sars patients is similar to or decreased relative to those with positive radiographic findings. radiography has two major roles in sars. the first role is to recognize pulmonary disease in a patient with clinical symptoms of sars and contact history but who may not have cough. the second role is to recognize radiographic changes that are more characteristic of other diseases including bacterial or granulomatous infections. it is important to differentiate sars from other respiratory infection(s) commonly encountered in children. although, many children with viral lower respiratory infection present clinically with bronchiolitis, it is often impossible to distinguish clinically and/or radiologically between viral and bacterial infections [43] . while its radiologic manifestations are nonspecific, sars appears similar to other viral infections encountered in children. certain radiographic findings are uncommon in sars, including extensive pleural effusions, pneumothorax, pneumatocele, and lung abscess. these findings were not encountered in our patient population, with exception of one patient with a small pleural effusion (table 1 , probable case no. 10). many patients were initially clinically thought to have tuberculosis or other infections, but the lack of radiographic findings such as adenopathy, cavitation, or pleural effusion may aid in suggesting sars or assist in excluding other disorders. recognition of the presence of radiographic changes which are atypical for sars, such as adenopathy and significant pleural effusion, may help to guide therapy as well as show the need for isolation. once the association with travel or case contact is lost in a community, clinical and radiographic recognition of the disease will become increasingly important especially if rapid diagnostic tests remain unavailable. our experience and that of others suggests little risk of transmission from child to adult; however, this remains to be substantiated. although the mechanisms of sars transmission remain to be fully elucidated, the most likely route of transmission is by large droplet and contact [22, 44] . data from hong kong have shown the potential of sars-associated coronavirus to persist in stool or urine of sars patients and maintain its viability on various contact surfaces for extended periods [45] . health-care workers are particularly at high risk, and there is potential for infection in the radiology department. we recommend extreme vigilance in application of infection control practices. further, the use of portable techniques in the ward, where a child can be maintained in proper isolation, helps to minimize the risk of sars virus transmission to staff and other patients. clinicians and radiology technologists need to use appropriate precautions during patient contact including hand hygiene, airborne measures (n-95 masks, capable of filtering out at least 95% of particles of a particular diameter), and contact precautions (e.g., caps, gowns, and gloves). goggles or visors are also recommended during direct patient contact, especially for aerosol-generating procedures such as suction or intubation [46] . cleansing of all radiographic equipment and rooms is important and consideration must be given to ensuring safe patient flow [41] . training and audit of inappropriate use of infection control measures have been documented as significant factors leading to health-care worker transmission. other factors include failure to apply appropriate isolation precautions to known sars cases or cases which have not yet been identified as sars and, finally, infected workers continuing to work despite infection. it is possible that all respiratory infections at initial presentation will need to be regarded as potential sars cases until proven otherwise. the retrospective nature of our study and the fact that we gathered data from multiple institutions are limiting factors. it is likely that the application of the case definitions was variable to some degree across the different communities and we lack knowledge as to whether the virus remains the same across these three distinct clusters. at this point we cannot be sure that all cases were indeed sars, and potentially other etiologies may have been included. limiting diagnosis to contact with a known case, although a valuable criterion, can lead to false-positive and false-negative cases especially as the disease spreads into the broader community [26] . community spread has not been identified in toronto and singapore; however, hong kong has encountered this problem at pwh and pmh where three rt-pcr confirmed sars cases were reported without definite contact history. although standard nomenclature was used, other potential limitations of sars diagnosis included the fact that we relied upon local interpretation of radiographs and review of radiology reports, which may be subject to some variation in interpretation of images. in conclusion, sars in children manifests with nonspecific radiographic features making radiological differentiation difficult, especially from other commonly encountered childhood respiratory viral illnesses causing airspace disease. the radiographic presentation of suspect sars cases ranged from normal or mild perihilar peribronchial thickening; however, the radiographic presentation, as expected, was relatively more pronounced in the probable sars cases with airspace disease including ground-glass opacification and consolidation. severe acute respiratory syndrome (sars) outbreak of severe acute 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prescribing for community acquired pneumonia: a closed loop audit severe acute respiratory syndrome (sars): information for clinicians sars can live on common surface severe acute respiratory syndrome (sars): infection control key: cord-260503-yq4dtf8n authors: samaranayake, lakshman p.; peiris, malik title: severe acute respiratory syndrome and dentistry a retrospective view date: 2004-09-30 journal: the journal of the american dental association doi: 10.14219/jada.archive.2004.0405 sha: doc_id: 260503 cord_uid: yq4dtf8n abstract background severe acute respiratory syndrome, or sars, which has created panic in asia and in some parts of north america, is the first epidemic of the new century. although it has been well-contained, sporadic cases continue to emerge. objectives the authors trace the emergence of the sars outbreak from southern china and its spread worldwide, discuss the viral etiology of the infection and its clinical features, and review the infection control guidelines issued during the outbreak by the health authorities in hong kong, the centers for disease control and prevention, the world health organization and the american dental association. they also review the prospects for a new outbreak and preventive measures. overview the disease, which is caused by a novel coronavirus termed the “sars coronavirus,” or sars-cov, essentially spreads through droplet infection and affects people of any age. it has a mortality rate ranging from 10 to 15 percent. a major hallmark of this disease has been the rate at which it has affected health care workers through nosocomial transmission; in some countries, up to one-fourth to one-third of those infected were in this category. however, no dental health care worker has been affected by sars in a nosocomial or dental setting. conclusions and clinical implications researchers believe that a combination of factors, including the universal infection control measures that the dental community has implemented and/or the low degree of viral shedding in the prodromal phase of sars, may have obviated the spread of the disease in dental settings. the dental community should reflect on this outbreak to reinforce the currently applied infection control measures. m icrobial threats continue to emerge, reemerge and persist. some organisms are newly recognized pathogens that have existed for centuries (for example, helicobacter pylori, which causes gastric ulcers). others are old organisms that have learned new tricks (for example, multidrug-resistant tubercle bacilli). a third category consists of totally new organisms. 1 this last group of alarming new infectious agents that are virulent and deadly have emerged in rapid succession during the last few years. some of these, such as the ebola virus infection, 2 are still smoldering in some remote corners of the world, 3 while others, such as the h5n1 (and h7n7) influenza a bird flu virus and the west nile virus infections, are emerging in different parts of the world. 4 severe acute respiratory syndrome, or sars, is the latest addition to this deadly assortment of new diseases. in the face of these infectious threats, in particular the pandemic of hiv infection, the dental community has reacted swiftly by adopting standard precautions. dentists follow a uniform infection control protocol to treat all patients, irrespective of their medical histories. 5 however, in the face of a new infection that is considered highly contagious, it is prudent to review infection control procedures. the objective of this article, therefore, is to describe the epidemiology, clinical features, etiology and prevention of sars, as well as to evaluate the current infection control protocols used in dentistry in view of the facts related to the spread of this infection. 6 we also explore the prospects for recrudescence of the disease, its treatment modalities and the promise of a sars vaccine. we do not know with certainty how, where and when the disease now known as sars manifested in humans, although theories abound. in february 2003, the world health organization, or who, coined the term "severe acute respiratory syndrome" for the flulike condition that developed into pneumonia. 7 nonetheless, researchers and clinicians generally believe that the first few cases may have originated in china. these sporadic cases were described sometime in the fall of 2002 in the guangdong province in southern china. for decades, the guangdong province had a large concentration of people, pigs and fowl living in close proximity because of mixed farming traditions that date back for centuries. 1 this region also has the dubious distinction of being the deadly source of the asian flu, caused by the h2n2 virus, which killed about 1 million people worldwide in 1957 and 1958. 8 in 1997, the avian flu (caused by the h5n1 virus), which killed six people, also originated in the guangdong province. 9 the recent outbreak. the sars outbreak has been identified in more than 30 countries in five continents, affecting more than 8,000 people, predominantly in asia (especially china), with mini-outbreaks in north america and a few cases in europe. the disease has led to more than 700 deaths worldwide. clusters of cases are particularly common among close associates of patients and the health care workers who treated them and their household contacts. because of the alarming global spread of the disease, who issued a global alert in march 2003 and instituted worldwide surveillance. 6 patient characteristics. most patients identified up to now were previously healthy adults aged 25 through 70 years. 10 a few cases of sars have been reported among children (≤ 15 years of age), in whom the clinical course now is thought to be less aggressive. 11 we provide a summary of the major clinical characteristics of patients with sars, although the information should be considered preliminary because of the broad and nonspecific case definition. clinical features. the incubation period for sars is widely considered to be two to seven days, but occasionally may last up to 10 days. symptomatically, the illness appears to have two phases: an early, prodromal febrile phase and a secondary lower-respiratory phase. in pathological terms, however, it is a triphasic disease with a primary viral replicative phase, a secondary immune hyperactive phase and a pulmonary destructive phase. 12 the disease generally begins with a prodrome of typically high fever (> 38 c) that may be accompanied by chills and rigors. headache, malaise and myalgia also are common. at the onset of the illness, some patients have mild respiratory symptoms. in a few cases, the febrile prodrome may be accompanied by diarrhea, although rash and neurologic or gastrointestinal findings are absent. after three to seven days, the secondary lower-respiratory phase begins with a dry, nonproductive cough or dyspnea that may be accompanied by, or progress to, hypoxemia. in up to one-fifth of the cases, the respiratory illness is severe enough to require intubation and mechanical ventilation. the fatality rate among patients with illness that meets the current who definition for probable and suspected cases of sars ranges from 3 to 10 percent, depending on the age group and possibly other, yet unconfirmed, factors. 10 furthermore, the mortality rate is higher among those with underlying illnesses and among the very elderly. typically, chest radiographs appear normal during the febrile prodrome and, in some patients, throughout the course of the illness. however, in the majority of patients, the respiratory phase is characterized by early focal infiltrates that progress to more generalized, patchy, interstitial infiltrates, sometimes leading to consolidation in the very late stages. 13 in general, in the early phase of the disease, patients may have either a normal or decreased white blood cell count, with a reduction in the absolute lymphocyte count. at the peak of the jada, vol. 135, september 2004 1293 c l i n i c a l p r a c t i c e symptomatically, the illness appears to have two phases: an early, prodromal febrile phase and a secondary lowerrespiratory phase. c l i n i c a l p r a c t i c e nomenon not common among other human coronaviruses. 16 medical workers in hong kong, toronto and germany noted this effect when they inoculated lung tissue of patients into cultured monkey kidney cells. [16] [17] [18] this phenomenon leads to a classic cytopathic effect in which the confluent cell layers in laboratory cell cultures are broken down, causing patchy denudation and detachment of cells. [16] [17] [18] immunofluorescence testing of the infected cells indicated that they were indeed infected with a new form of the coronavirus, which has been termed "sars coronavirus," or sars-cov. furthermore, antibodies to the sars-cov were found almost exclusively in patients with sars during their convalescence, but not in human serum samples from healthy patients or in samples banked before the outbreak, 16 suggesting that the infection is new to humans. until now, human coronaviruses have caused the relatively innocuous common cold. 20 however, coronaviruses that infect other mammals and birds are more virulent. these include avian infectious bronchitis (a major problem in the poultry industry), transmissible gastroenteritis of pigs and feline infectious peritonitis. 21 although there was initial speculation that close contact between poultry and humans in the chinese province of guangdong (where sars is thought to have originated) may have resulted in the virus' crossing the species barrier from poultry to humans, evidence now indicates that the himalayan palm civet cats that are consumed as a delicacy and sold widely in animal markets in china are the source of the infection. 22 however, the sars-cov is not a recombinant of known coronaviruses. analyses of the genetic signatures of the viral strains from different geographic regions indicate that immunological pressure might modulate the evolution of the virus in human population cohorts. 23, 24 other candidate organisms such as paramyxovirus and chlamydia have been implicated in the disease process, but the consensus is that they play a very small role, if any, in the pathogenesis of sars. 23 general properties of coronaviridae. coronaviridae are a family of rna viruses that have been associated etiologically with respiratory ill-lower respiratory phase, up to one-half of patients exhibit leukopenia and thrombocytopenia or platelet counts at the low end of the normal range (50,000 to 150,000 per microliter). renal function appears to remain normal in the vast majority of patients. the box shows the second interim case definition for sars, provided by the centers for disease control and prevention, or cdc. 14 it is based on clinical, epidemiologic and laboratory criteria. 14 however, in areas such as hong kong, where there has been significant disease activity, the cdc criteria have been amended to include patients who do not respond to appropriate antibiotic therapy for atypical pneumonia caused by conventional agents (such as mycoplasma pneumoniae and chlamydia pneumoniae) and/or are in direct contact with another patient with sars. treatment and prevention. a number of treatment regimens have been explored for sars. these include a variety of antibiotics to presumptively treat known bacterial agents of atypical pneumonia, as well as antiviral agents such as oseltamivir and ribavirin. steroids also have been administered in combination with these antimicrobial agents. however, the most beneficial regimen remains to be determined. 15 until reliable diagnostic tests, an effective vaccine and antiviral drugs are available, control of the epidemic depends on early identification of suspected and probable cases, quarantine of patients (and their close contacts) and effective infection control measures, particularly after patients are admitted to a health care facility. etiology. researchers have confirmed that a new strain of virus belonging to the family coronaviridae is the prime agent of this disease. [16] [17] [18] [19] although other viruses belonging to paramyxoviruses such as metapneumovirus have been implicated, these appear to play only a secondary role, if any, in the disease process. the coronaviruses-so named for the crown of spikes they carry on their surface 20 -attracted the interest of researchers when they noted that the virus rapidly infected cells in culture, a pheis the prime agent of severe acute respiratory syndrome. copyright ©2004 american dental association. all rights reserved. one or more of the following exposures in the 10 days before the onset of symptoms: dtravel to a foreign or domestic location with documented or suspected recent transmission of sars-cov; dclose contact † with a person with mild-to-moderate or severe respiratory illness and history of travel in the 10 days before onset of symptoms to a foreign or domestic location with documented or suspected recent transmission of sars-cov likely exposure to sars-cov one or more of the following exposures in the 10 days before onset of symptoms: dclose contact with a person with confirmed sars-cov disease; dclose contact with a person with mild-to-moderate or severe respiratory illness for whom a chain of transmission can be linked to a confirmed case of sars-cov disease in the 10 days before onset of symptoms laboratory criteria tests to detect sars-cov are being refined and their performance characteristics assessed; therefore, criteria for laboratory diagnosis of sars-cov are changing. the following are general criteria for laboratory confirmation of sars-cov: ddetection of serum antibody to sars-cov by a test validated by the centers for disease control and prevention, or cdc (for example, enzyme immunoassay); or disolation in cell culture of sars-cov from a clinical specimen; or ddetection of sars-cov rna by a reverse transcriptase polymerase chain reaction test validated by cdc and with subsequent confirmation in a reference laboratory (for example, cdc) dprobable case: meets the clinical criteria for severe respiratory illness of unknown etiology and epidemiologic criteria for exposure; laboratory criteria confirmed or undetermined dsuspect case: meets the clinical criteria for moderate respiratory illness of unknown etiology and epidemiologic criteria for exposure; laboratory criteria confirmed or undetermined a case may be excluded as a suspect or probable sars case if: dan alternative diagnosis can fully explain the illness; dthe case has a convalescent-phase serum sample (that is, obtained > 28 days after symptom onset), which is negative for antibodies to sars-cov; dthe case was reported on the basis of contact with an index case that was subsequently excluded as a case of sars, provided other possible epidemiologic exposure criteria are not present * adapted from the centers for disease control and prevention. 14 † close contact is defined as having cared for or lived with a person who has sars, or having a high likelihood of being in direct contact with respiratory secretions and/or body fluids of a person with sars (during encounters with the patient or through contact with materials contaminated by the patient), either during the period in which the individual was clinically ill or within 10 days of resolution of symptoms. examples of close contact include kissing or embracing, sharing eating or drinking utensils, close conversation (less than 3 feet apart), physical examination, and any other direct physical contact between people. close contact does not include activities such as walking by an individual or sitting across a waiting room or office for a brief time. ness in humans and with other diseases in domestic animals. interestingly, they also are associated to some extent with human diarrheal diseases. 21 structurally, they are 80 to 160 nanometers in diameter, positive-stranded and about 30 kilobases in length. 21 their genome is the largest of all rna viruses, and highfrequency recombination between related coronaviruses leads to the generation of much genetic diversity. the virus has three major proteins. the nucleocapsid protein is enclosed within the viral envelope with the rna in a helical nucleocapsid. the other two proteins are the membrane glycoproteins and the spike glycoprotein. 21 the spike glycoprotein is responsible for the characteristic fringe of crownlike projections. antibodies that elicit spike glycoprotein are thought to confer protection against infection. because the human strains are relatively difficult to culture compared with animal strains, the extent of strain variation in human coronaviruses is unclear. 25 there are three serologically and genetically distinct groups of coronaviruses associated with animal and human disease. in general, they are species-specific, although there are a number of examples of viruses crossing species barriers and establishing themselves in new hosts. 21, 25 once the host is infected, the virus may produce localized disease that often is restricted to the respiratory epithelium or the gastrointestinal tract, or they may produce disseminated infection causing systemic disease. 21 coronavirus was confirmed as the etiologic agent in sars via serologic techniques demonstrating a rise in antibody titer, its growth in tissue culture, a determination of reverse transcriptase-polymerase chain reaction, or rt-pcr, specific for this virus using molecular genetic techniques, and animal studies. 23 animal studies have helped to satisfy koch's postulates, which are necessary to prove disease causation. 19 these postulates stipulate that to be the causal agent, a pathogen must meet four conditions: it must be found in all cases of the disease, it must be isolated from the host and grown in pure culture, it must reproduce the original disease when introduced into a susceptible host, and it must be found in the experimental host so infected. however, further studies that include control groups are required to determine the role of other agents, if any, in causality or as cofactors for severe disease. virus infectivity and survival. the rapid spread of sars worldwide within a few months points to the contagious nature of the disease. the infectivity during the incubation period is still unclear, and it appears that the risk of transmission during the prodrome is low. in contrast, in coronaviruses that cause the common cold, the viral shedding period usually precedes the onset of clinical symptoms by one to two days, although the peak viral excretion occurs during the symptomatic phase. 21, 23, 26 the infectivity of sars during convalescence appears to be low and remains to be determined. some data on the survival and infectivity of the sars coronavirus 27 indicate that, unlike other coronaviruses, it is a rather robust organism that is stable in feces (and urine) at room temperature for at least one to two days. it is more stable (up to four days) in stool from patients with diarrhea (which has a higher ph than does normal stool). however, the virus loses infectivity five minutes after being exposed to commonly used disinfectants and fixatives, including 10 percent formaldehyde, 10 percent hypochlorite, 75 percent ethanol and 2 percent phenol. heat at 56 c kills the sars coronavirus at around 10,000 units per 15 minutes (considered to be a quick reduction). 27 spread of the disease. the available epidemiologic data suggest strongly that the main routes of virus spread are droplets, direct contact and fomite (indirect contact) transmission, although airborne transmission has not been ruled out completely. 28 researchers believe that the cause of the large outbreaks among health care workers was the transmission of droplets through aerosol-generating medical procedures, such as the use of nebulizers. 28, 29 no firm data exist regarding the infectivity of contaminated saliva (as opposed to sputum from the respiratory tract) through the droplet route. in some patients, the infection manifests itself as a mild form of diarrhea, and coronavirus particles have been recovered from fecal matter. hence, it is possible that fecal contamination could lead to the spread of the disease, although more data are needed to confirm this route of transmission. it is interesting that some animal coronaviruses are spread through the fecal-oral route. 21 laboratory diagnosis. the mainstay of the sars diagnosis is its characteristic clinical features mentioned above. however, a number of laboratory tests-including serologic tests, cell culture and molecular diagnostics-can be used to confirm the clinically suspicious or probable cases. 16, 23 these tests include the following. enzyme-linked immunosorbent assay, or elisa, test. from about 20 days after the onset of clinical signs, elisa tests can be used to detect immunoglobulin, or ig, m and iga antibodies in the serum samples of patients with sars. early antibodies are detected in some patients within two weeks. immunofluorescence assay. sars virusinfected vero cells can be used to detect igm antibodies in serum samples of patients after about day 10 of the onset of the disease. this test is reliable, yet demanding, because the live virus must be grown in cell culture; in addition, subsequent immunofluorescence needs to be demonstrated. cell culture. laboratory workers can detect virus in specimens (for example, respiratory secretions, blood) from patients with sars by infecting cultured vero-e6 or fetal rhesus kidney 4, or frhk-4, cells. molecular tests. laboratory workers can use pcr assays that detect genetic material of coronavirus in patient specimens (such as respiratory secretions, blood or stool samples). primers that are required for this test now are available widely through various web sites (for example, the cdc, the university of hong kong and the governmental viral unit of hong kong). interpretation of test results. clinicians must exercise caution when interpreting laboratory test results, because the key to diagnosis is clinical evaluation and possible exposure to an infected person. a positive laboratory test result indicates that the patient is, or has been, infected with the sars-cov, while a negative test result does not necessarily rule out sars. 16, 23 seroconversion of paired serum samples with convalescent serum samples obtained more than 21 days after onset of symptoms is a reliable, sensitive and specific diagnostic method. however, the current diagnostic option of choice for early and rapid diagnosis is rt-pcr detection of virus in respiratory or fecal specimens. this test has low sensitivity, and a negative test result does not exclude the diagnosis. many laboratories are addressing the problem of sensitivity and specificity of the sars diagnostic tests, and it will take some time before a highly sensitive, specific, quick and simple diag-nostic test is available. it is possible that, as is the case with hiv infection, saliva could be used as a diagnostic fluid in this context. many people have been alarmed by the spread of sars in clinical facilities, where a disproportionately large number of health care workers (sometimes up to one-third) have been infected. however, it is reassuring that, to date, there have been no documented cases of sars transmitted in a dental setting. this may be the result of a combination of factors. first, transmission has not been documented during the incubation period before the appearance of febrile symptoms. it is unlikely that patients with sars would visit a dentist for elective treatment while they are in the acute phase of the disease, because of the high fever and other, rather debilitating, attendant symptoms. seto and colleagues 29 conducted a case-control study in which they showed that proper use of standard precautions is adequate to prevent the nosocomial spread of sars in the absence of aerosol-producing procedures. however, as health care providers, dental personnel should be wary of the disease and should know how it is spread, how to identify patients with sars and what modifications need to be made to the practice to prevent transmission of the disease. although sars is well-controlled now, it may emerge insidiously, as has been the case with many other coronavirus infections. we review below the infection control measures that dentists and dental staff members now follow, in light of new epidemiologic data about sars, particularly its spread through aerosols and droplets. our recommendations are based on the recent ada guidelines, 30 the cdc's recent report of recommended infection control practices for dentistry 31 and our own experience in hong kong related to the last outbreak. identification of patients with sars. as health care providers, dentists should be able to identify a suspected case of sars. the cdc's current interim diagnostic criteria for sars are shown in the box. 14 they are subject to change as more is learned about the disease, and should be reviewed periodically by visiting the ada or cdc web sites. to date, there have been no documented cases of severe respiratory syndrome transmitted in a dental setting. as stated above, we doubt that patients with sars who are in the acute febrile phase of the disease will visit a dentist. in the unlikely event that this does occur, the dentist should not treat the patient in the dental office, but should refer him or her to a health care facility as soon as possible for diagnosis and care. dentists also have a duty to report the case to state or local health departments. 32 patient evaluation. as always, dentists should take a thorough medical history from each patient and update it at each recall appointment. 5 the questionnaire used for this purpose may have to be modified to incorporate targeted screening questions regarding sars. although these questions may appear superfluous during the current abeyance of the outbreak, they are important as a guide if there is another outbreak of sars or an outbreak of a similar new disease. these questions may include the following: ddo you have fever? dhave you experienced a recent onset of a respiratory problem, such as a cough or difficulty breathing? dhave you, within the last 10 days (that is, the incubation period for sars), traveled internationally or visited an area where documented or suspected community transmission of sars is occurring? dhave you come into contact with a patient with sars in the past 10 days? in the event that the patient recently has returned from a geographic region with documented or suspected community transmission of sars, the clinician can defer elective treatment until the incubation period is over. dentists can provide emergency treatment, provided they use routine barrier precautions and avoid spatter or aerosol-generating procedures. this emergency treatment should be limited to the control of pain and infection. dentists should not treat patients in the dental office who are suspected of having sars. if a patient replies "yes" to the first two screening questions, the dentist should wear a surgical mask, discuss his or her potential concerns with the patient, call an area medical facility (such as a hospital) and inform the staff that he or she is referring a patient suspected of having sars so that arrangements can be made for transportation and care of the patient. patients with sars need ground emergency medical services. 32 these screening questions should be asked routinely of all patients, because questioning only a select group of patients, for whatever reason, may undermine the early detection of infection and might be construed as a discriminatory practice. clinicians should delay treating convalescing patients for at least one month after they are released from the hospital. convalescing patients are instructed to remain at home for seven days after discharge from the hospital, and during this period they are requested to stay indoors and keep contact with others to a minimum. 33 preprocedural rinsing. a preprocedural antimicrobial mouthrinse (with 0.12 to 0.2 percent chlorhexidine gluconate) is believed to reduce the number of microbes that are released into the operatory environment. this has been shown in a number of studies in which a longlasting mouthrinse (for example, chlorhexidine gluconate with povidone iodine and essential oils) has reduced the disseminated microbial load during procedures such as ultrasonic scaling. 34, 35 however, no concrete data show that a preprocedural mouthrinse reduces infection among dental health care workers or patients. a preprocedural rinse would be most useful in situations in which a rubber dam cannot be used, such as when a prophylaxis cup or an ultrasonic scaler is used, and in the absence of assisted, high-volume suction. hand hygiene. microflora on the skin can be divided into two categories: the transient flora colonizing the superficial layers of the skin and mainly acquired through environmental routes, and the residential flora thriving on the deeper layers of the skin and hair follicles. 36 the exogenous, superficial flora are harmful and pathogenic, but are removed easily with clinical hand-washing procedures. by contrast, the endogenous residential flora are almost impossible to remove completely, but are less likely to be associated with infections. 36 the single most important method of preventing transmission of any infectious agent, including the sars coronavirus, is hand washing and appropriate hand care. studies have found that even in critical care units, hand-washing compliance is relatively low, sometimes approaching 40 percent. 37 by contrast, a dramatic reduction in the prevalence of health careassociated infections has been shown when regimented hand hygiene measures were introduced. 38 thus, appropriate hand hygiene is the mainstay of a good dental infection control program. furthermore, recent data indicate that the sars virus, compared with other coronaviruses, is a relatively robust organism and may survive on nonporous surfaces for up to 48 hours. 39 this reinforces the need for good hand hygiene, as well as the importance of thorough surface disinfection. hand hygiene for routine dentistry. for routine dentistry, which entails examinations and nonsurgical procedures, plain soap and water are adequate. recently, the cdc recommended that if the health care worker's hands are not visibly soiled, an alcohol-based hand rub could be used for routine decontamination, because this is as effective as hand washing and also saves time. 40 also, clinicians should decontaminate their hands both before and after removing gloves, because humidity and moisture cause bacteria to multiply rapidly under the glove surface. hand rubs that are based on alcohol alone should not be used owing to their rapid evaporation and lack of residual effect. consequently, hand rubs must be laced with agents such as chlorhexidine, octenidine or triclosan to achieve the needed effect. 41 after using an alcohol-based hand rub, the clinician must dry his or her hands thoroughly before putting on gloves, because any residual alcohol may increase the risk of glove perforation. 42 personal protective equipment. personal protective equipment, or ppe, is designed to protect the skin and mucous membranes of the eyes, nose and mouth from exposure to potentially infectious material. recent experience with the sars coronavirus has shown that vast numbers of health care workers acquired the infection in hospital settings, either as a result of inadequate barrier protection methods or the improper use of these methods. 29 this barrier protection equipment consists of protective eyewear, masks, gloves, face shields and protective overwear. we should note that general work clothes such as uniforms do not protect against a hazard and should not be considered ppe. we describe below the relevant aspects of ppe that pertain to protection against airborne hazards. masks. face masks were first worn by surgeons to minimize postsurgical infection in patients due to microbes that were exhaled or shed by the surgical team. 43 however, the realization that face masks protect the health care worker as well as the patient has led to the routine use of this protective measure in many clinical settings including dentistry. transmission of airborne infection depends on factors such as the virulence of the organism, as well as the number of organisms, transmitted. 44 in the case of coronavirus-induced pneumonia leading to sars, airborne droplet transmission of infection is considered to be the main route of spread. 45 various types of masks and face shields are available. surgical masks usually provide adequate protection in dental care settings, where highly transmissible infectious diseases are not typically encountered. particulate respirators. however, surgical masks are not designed to provide adequate protection against exposure to airborne infectious agents such as tubercle bacilli or droplet nuclei smaller than 5 micrometers. for such purposes, particulate respirators (for example, n-95 masks) must be used. during the sars outbreak in hong kong, the vast majority of dental practitioners in that country used n95 masks for routine dentistry. however, these masks are uncomfortable to wear for extended periods because of the difficulty in breathing through a thick impervious fabric, and are not recommended for routine dental office settings. rubber dam isolation. rubber dams help minimize the production of saliva-and bloodcontaminated aerosol or spatter. samaranayake and colleagues 46 reported an up-to-70-percent reduction in airborne particles around a 3-foot diameter of the operational field when a rubber dam was used. a split-dam technique may be used in situations in which gingival areas are involved, such as class v restorations and crownand-bridge preparations. aerosol-generating procedures should be avoided as much as possible if rubber dam isolation is not feasible. some of these procedures include ultrasonic scaling, root-surface débridement, and high-or low-speed drilling with water spray. there is no doubt that coronavirus research has gained an unprecedented and urgent momentum owing to the lethality of sars and its nearly worldwide spread within a few months. consequently, laboratories throughout the world are working in unison to provide answers to many unresolved questions, as well as to develop a new preventive vaccine. in dentistry, in particular, a number of questions remain to be resolved, including the following: although the global threat of sars has peaked for the most part, it is helpful to review the response of the community to this novel disease. it is fortunate that sars was not sufficiently infective to cause a repeat of the 1918 influenza pandemic that killed millions. even so, we might be able to attribute the relatively low death rate in large part to the worldwide surveillance networks and patient isolation efforts that were introduced rapidly in most countries. in retrospect, an overreaction seems to have been a better option than allowing the disease to run out of control, as was the case with the aids pandemic. culmination of the outbreak. the who lifted all its travel advisories 47 as of june 15, 2003 , and since then, only three new cases of sars have been reported. two of these-one in singapore and the other in taiwan-were acci-dental, laboratory-acquired infections in research technicians working with the organism, while the third patient-from guangdong province in southern china-is thought to have acquired the infection through contact with contaminated rodents. because the initial symptoms of sars mimic those of many variants of atypical pneumonia, a high degree of suspicion by the medical establishment, intense surveillance and immediate quarantine of all close contacts of patients should ward off another, large-scale winter outbreak. if sars does return, its epidemiology may be different from that of the current strain. for instance, the genome of the new sars-cov may differ, and the virus may be more or less infective than the original strain that emerged in 2003. furthermore, we do not know how long the acquired immunity to sars persists. also, will those exposed to the virus be carriers of the disease in the face of a new infection? how many will be silent healthy carriers of the virus? will an emergent strain or strains behave similarly to the older counterpart? we do not have the answers to these questions. mutation of the sars-cov. the reason for the pandemic spread of hiv is its ability to mutate rapidly from one generation to another so it can escape the immune surveillance mechanisms of the host, as well as the prescribed antiviral medications. the sars virus, on the other hand, seems to be remarkably invariant; the genome sequence of isolates from patients in singapore, toronto, china and hong kong has not revealed any changes of major consequence. 23 this does not mean that the sars virus is incapable of mutation; rather, because the virus has encountered little resistance from new human hosts, there is less selective pressure for new mutants to emerge and persist. drugs and vaccines for sars. many researchers are working on potential drugs and vaccines to treat patients with sars. however, their approach has been scattered for the most part, as they screen the multitude of available drugs and compounds for their ability to destroy the sars-cov. thus far, a few have had success. one group reported that the compound glycrrhizin, which is derived from licorice roots, can rid cultured monkey kidney cells of the sars virus. 48 other researchers, using in silico research, have proposed that the newly described proteinase of the sars virus (which converts viral proteins into the active form required for viral replication) 49 could be inhibited by drugs. animal models are essential for experimentation and drug discovery; thus far, the only validated model has been cynomolgus macaque (macaca fascicularis). 20 a smaller and less expensive animal model for sars research has yet to be defined. although vaccines exist for animal coronavirus infections, it may take a few years before a vaccine for sars is developed. it is comforting to note that the existing technology and know-how for animal coronavirus vaccines could be translated directly toward the manufacture of a sars vaccine. furthermore, implicit evidence shows that the vaccine approach to preventing sars is feasible, because patients' conditions appear to improve when they are given hyperimmune serum from recovered patients with sars. sars vaccines could be based on a killed sars virus or on an attenuated virus that is sufficiently potent to replicate itself in humans and initiate a successful antibody response, but not potent enough to cause disease. another option would be to re-engineer a harmless candidate virus to contain genetic sequences of the sars virus. this approach has been used to produce a prototypic vaccine against a coronavirus that causes bronchitis in chickens. 50 should there be a renewed threat of sars, a vaccine would be a mostwelcomed weapon by health care workers. sars is the first readily transmissible infectious disease that the global community has confronted in the new millennium. this, surely, will not be the last contagion that we will encounter. the fact that no dental health care worker or dental patient has thus far contracted sars in a dental setting is a testament to good infection control measures that have been implemented in the vast majority of dental offices. however, the dental community cannot let down its guard, and must be constantly aware of impending infectious threats in various guises, as well as recrudescence of disease, that may challenge the current infection control regimen. i institute of medicine; 2003. 2. samaranayake lp, peiris js, scully c. ebola virus infection: an overview the ebola virus and the challenges to health research in africa west nile virus: statistics, surveillance, and control. available at infection control for the dental team cumulative number of reported probable1 cases of severe acute respiratory syndrome (sars) there is nothing permanent except change: the emergence of new virus diseases centers for disease control and prevention. isolation of avian influenza a (h5n1) viruses from humans: hong kong epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in hong kong clinical presentations and outcome of severe acute respiratory syndrome in children sars: what do we know about the disease updated interim u.s. case definition for severe acute respiratory syndrome (sars) (appendix b1) sars bulletin from hong kong coronavirus as a possible cause of severe acute respiratory syndrome identification of a novel coronavirus in patients with severe acute respiratory syndrome sars-associated coronavirus koch's postulates fulfilled for sars virus coronaviruses of man isolation and characterization of viruses related to the sars coronavirus from animals in southern china identification of severe acute respiratory syndrome in canada comparative full length sequence analysis of 14 sars coronavirus isolates and common mutations associated with putative origins of infection centers for disease control and prevention. interim domestic infection control precautions for aerosol-generating procedures on c l i n i c a l p r a c t i c e patients with severe acute respiratory syndrome (sars) effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (sars) world health organization. who hospital discharge and followup policy for patients who have been diagnosed with severe acute respiratory syndrome (sars) reduction of viable bacteria in dental aerosols by preprocedural rinsing with an antiseptic mouthrinse reduction of bacteria-containing spray produced during ultrasonic scaling essential microbiology for dentistry how good are hand-washing practices? world health organization. summary on major findings in relation to coronavirus by members of the who multicenter collaborative network on sars aetiology and diagnosis. available at healthcare infection control practices advisory committee, hicpac/shea/apic/idsa hand hygiene task force. guideline for hand hygiene in health-care settings: recommendations of the healthcare infection control practices advisory committee and the hicpac/shea/apic/idsa hand hygiene task force: society for healthcare epidemiology of america/association for professionals in infection control/infectious diseases society of america hospital epidemiology and infection control the integrity of latex gloves in clinical practice the surgical mask unmasked: a review medical progress: how contagious are common respiratory tract infections? evidence of airborne transmission of the severe acute respiratory syndrome virus the efficacy of rubber dam isolation in reducing atmospheric bacterial contamination sars: breaking the chains of transmission chemical modification of glycyrrhzic acid as a route to new bioactive compounds for medicine coronavirus main proteinase (3clpro) structure: basis for design of anti-sars drugs a recombinant fowl adenovirus expressing the s1 gene of infectious bronchitis virus protects against challenge with infectious bronchitis virus dr. peiris is a professor of virology, faculty of medicine, the university of hong kong, hong kong, and the chief clinical virologist, queen mary hospital, hong kong. key: cord-262545-bs8p50ig authors: luk, andrea o. y.; ke, calvin; lau, eric s. h.; wu, hongjiang; goggins, william; ma, ronald c. w.; chow, elaine; kong, alice p. s.; so, wing-yee; chan, juliana c. n. title: secular trends in incidence of type 1 and type 2 diabetes in hong kong: a retrospective cohort study date: 2020-02-20 journal: plos med doi: 10.1371/journal.pmed.1003052 sha: doc_id: 262545 cord_uid: bs8p50ig background: there is very limited data on the time trend of diabetes incidence in asia. using population-level data, we report the secular trend of the incidence of type 1 and type 2 diabetes in hong kong between 2002 and 2015. methods and findings: the hong kong diabetes surveillance database hosts clinical information on people with diabetes receiving care under the hong kong hospital authority, a statutory body that governs all public hospitals and clinics. sex-specific incidence rates were standardised to the age structure of the world health organization population. joinpoint regression analysis was used to describe incidence trends. a total of 562,022 cases of incident diabetes (type 1 diabetes [n = 2,426]: mean age at diagnosis is 32.5 years, 48.4% men; type 2 diabetes [n = 559,596]: mean age at diagnosis is 61.8 years, 51.9% men) were included. among people aged <20 years, incidence of both type 1 and type 2 diabetes increased. for type 1 diabetes, the incidence increased from 3.5 (95% ci 2.2–4.9) to 5.3 (95% ci 3.4–7.1) per 100,000 person-years (average annual percentage change [aapc] 3.6% [95% ci 0.2–7.1], p < 0.05) in boys and from 4.3 (95% ci 2.7–5.8) to 6.4 (95% ci 4.3–8.4) per 100,000 person-years (aapc 4.7% [95% ci 1.7–7.7], p < 0.05] in girls; for type 2 diabetes, the incidence increased from 4.6 (95% ci 3.2–6.0) to 7.5 (95% ci 5.5–9.6) per 100,000 person-years (aapc 5.9% [95% ci 3.4–8.5], p < 0.05) in boys and from 5.9 (95% ci 4.3–7.6) to 8.5 (95% ci 6.2–10.8) per 100,000 person-years (aapc 4.8% [95% ci 2.7–7.0], p < 0.05) in girls. in people aged 20 to <40 years, incidence of type 1 diabetes remained stable, but incidence of type 2 diabetes increased over time from 75.4 (95% ci 70.1–80.7) to 110.8 (95% ci 104.1–117.5) per 100,000 person-years (aapc 4.2% [95% ci 3.1–5.3], p < 0.05) in men and from 45.0 (95% ci 41.4–48.6) to 62.1 (95% ci 57.8–66.3) per 100,000 person-years (aapc 3.3% [95% ci 2.3–4.2], p < 0.05) in women. in people aged 40 to <60 years, incidence of type 2 diabetes increased until 2011/2012 and then flattened. in people aged ≥60 years, incidence was stable in men and declined in women after 2011. no trend was identified in the incidence of type 1 diabetes in people aged ≥20 years. the present study is limited by its reliance on electronic medical records for identification of people with diabetes, which may result in incomplete capture of diabetes cases. the differentiation of type 1 and type 2 diabetes was based on an algorithm subject to potential misclassification. conclusions: there was an increase in incidence of type 2 diabetes in people aged <40 years and stabilisation in people aged ≥40 years. incidence of type 1 diabetes continued to climb in people aged <20 years but remained constant in other age groups. the hong kong diabetes surveillance database hosts clinical information on people with diabetes receiving care under the hong kong hospital authority, a statutory body that governs all public hospitals and clinics. sex-specific incidence rates were standardised to the age structure of the world health organization population. joinpoint regression analysis was used to describe incidence trends. a total of 562,022 cases of incident diabetes (type 1 diabetes [n = 2,426]: mean age at diagnosis is 32.5 years, 48.4% men; type 2 diabetes [n = 559,596]: mean age at diagnosis is 61.8 years, 51.9% men) were included. among people aged <20 years, incidence of both type 1 and type 2 diabetes increased. for type 1 diabetes, the incidence increased from 3.5 (95% ci 2.2-4.9) to 5.3 (95% ci 3.4-7.1) per 100,000 person-years (average annual percentage change [aapc] 3.6% [95% ci 0.2-7.1], p < 0.05) in boys and from 4.3 (95% ci 2.7-5.8) to 6.4 (95% ci 4.3-8.4) per 100,000 person-years (aapc 4.7% [95% ci 1.7-7.7], p < 0.05] in girls; for type 2 diabetes, the incidence increased from 4.6 (95% ci 3.2-6.0) to 7.5 (95% ci 5.5-9.6) per 100,000 person-years (aapc 5.9% [95% ci 3.4-8.5], p < 0.05) in boys and from 5.9 (95% ci 4.3-7.6) to 8 , p < 0.05) in women. in people aged 40 to <60 years, incidence of type 2 diabetes increased until 2011/2012 and then flattened. in people aged �60 years, incidence was stable in men and declined in women after 2011. no trend was identified in the incidence of type 1 diabetes in people aged �20 years. the present study is limited by its reliance on electronic medical records for identification of people with diabetes, which may result in incomplete capture of diabetes cases. the differentiation of type 1 and type 2 diabetes was based on an algorithm subject to potential misclassification. there was an increase in incidence of type 2 diabetes in people aged <40 years and stabilisation in people aged �40 years. incidence of type 1 diabetes continued to climb in people aged <20 years but remained constant in other age groups. why was this study done? • diabetes affects over 400 million people worldwide, and over half of the diabetes population comes from asian countries. • most studies on the burden of diabetes in asia reported the diabetes prevalence, i.e., the proportion of the population with disease, but few have considered diabetes incidence, i.e., the rate at which new cases have developed in the population. • knowledge of disease incidence informs how population exposure to risk factors has changed over time and is useful for projection of future prevalence. what did the researchers do and find? • we identified 562,022 people with new-onset type 1 or type 2 diabetes occurring between 2002 and 2015 in the electronic medical record system of the hong kong hospital authority. • we calculated the incidence rates of diabetes according to age categories and gender and analysed incidence trends over time. • we found that the incidence of both type 1 and type 2 diabetes increased in children and adolescents (aged <20 years). • incidence of type 2 diabetes also increased in people aged 20 to <40 years but was stable in people aged �40 years. type 2 diabetes mellitus is a complex progressive disease of rapidly growing prevalence. the global prevalence of type 2 diabetes is currently estimated at 415 million and is projected to escalate to 642 million over the next 25 years [1] . more than half of the world's population of those with type 2 diabetes comes from asia, where rapid industrialisation and urbanisation have contributed to an obesogenic living environment and increasing rates of overweight and obesity [1] . the majority of published population-based studies on the epidemiology of type 1 and type 2 diabetes in asia, including china, reported prevalence data, but few examined the incidence of diabetes [2, 3] . although the prevalence informs the disease burden, the incidence reflects how population exposure to risk factors has changed over time, and these estimates are necessary for the accurate projection of future prevalence. importantly, disease incidence communicates to the health policy makers whether strategies to prevent diabetes have been effective. recently, quan and colleagues reported the incidence and prevalence of diabetes in hong kong and detected a decline in the incidence of diabetes over a 9-year period between 2006 and 2014 [4] . however, diabetes types were not differentiated, and trends among the paediatric population were not explored. we accessed the territory-wide database hosted by the hong kong hospital authority (ha) and described the secular trends in incidence of type 1 and type 2 diabetes from 2002 to 2015. hong kong is a special administrative region of people's republic of china and has a population of 7.44 million. the hong kong ha is a statutory body formed in 1996 that governs all 47 public hospitals and 73 government outpatient clinics in hong kong. because of the wide cost differential between public and private healthcare sectors, around 89% of the local residents receive care for chronic illnesses in the ha [5] . a territory-wide electronic medical record system, adopted in 2000, captures demographic information, diagnostic and procedure codes, laboratory results, and drug prescriptions of people attending public hospitals and clinics. the hong kong diabetes surveillance database (hkdsd) is a population-based cohort of people with diabetes in hong kong identified from the ha electronic medical record system between 1 january 2000 and 31 december 2016. the analysis was not prespecified and was planned after obtaining and reviewing the content of the database. diabetes was ascertained based on one or more of the following qualifying criteria: (1) glycated haemoglobin (hba1c) � 6.5% (48 mmol/mol) in any one available hba1c measurement [6] ; (2) fasting plasma glucose (fpg) � 7.0 mmol/l in any one available fpg measurement [7] ; (3) prescription of noninsulin antihyperglycaemic drugs and/or (4) prescription of insulin for at least 28 days continuously, with or without (5) recording of the diagnostic code of diabetes based on the international classification of diseases, ninth revision (icd-9) code 250; and/or (6) recording of the diagnostic code of diabetes according to the revised edition of the international classification of primary care, world organization of national colleges, academics, and academic associations of general practitioners/family physicians code t89 or code t90. to minimise misclassification of normal individuals as having diabetes, people who received diagnostic coding of diabetes but did not fulfil any of the laboratory or drug criteria throughout the observation are not considered. to avoid inclusion of women with gestational diabetes, we removed episodes occurring within 9 months prior to or 6 months after delivery (icd-9 codes 72-75) or occurring within 9 months before or after any pregnancy-related encounter (icd-9 codes 630-676). however, women with subsequent episodes that met the criteria for diabetes occurring outside the context of any obstetric events would be included. the separation of diabetes types is not reliable based on coding alone in administrative databases. in the hkdsd, a small subset of people received icd-9 coding for both type 1 and type 2 diabetes. for the purpose of this analysis, we developed and validated an algorithm to delineate type 1 from type 2 diabetes using another database, the hong kong diabetes register (hkdr). in brief, the hkdr contains clinical information on people with physician-diagnosed diabetes who were referred to two public hospitals (prince of wales hospital and alice ho miu ling nethersole hospital) for assessment of diabetes complications. in the hkdr, diabetes subtype was determined by the referring physician and was independently confirmed with chart review by one of the investigators (ck) of the present study. type 1 diabetes was defined as clinical presentation with diabetic ketoacidosis and/or continuous requirement of insulin within 1 year of diagnosis. positivity for islet autoantibodies was not used to define autoimmune diabetes because antibodies were not routinely measured. of 24,060 patients in the hkdr, we excluded people with onset dates outside of 1 january 2002 to 31 december 2015 (n = 8,403) and those with missing data on diabetes subtype (n = 357). of the remaining 15,297 people with newly diagnosed diabetes, type 1 diabetes was confirmed in 103 patients. the cohort was separated in a 2:1 ratio for derivation and validation of the algorithm, respectively. we considered icd-9 codes (type 1 diabetes: icd-9 250.x1 or 250.x3, type 2 diabetes: icd-9 250.x0 or 250.x2) and types of insulin treatment in the algorithms, and we tested 12 combinations for sensitivity, specificity, positive predictive value (ppv) and negative predictive value (npv) for identifying type 1 diabetes. of these combinations, ratios of type 1 to type 2 diabetes codes �4 or prescription of a combination of short-and long-acting insulin and no noninsulin antihyperglycaemic treatment within the first year of diagnosis yielded the optimal sensitivity of 100.0% (95% ci 76.8-100.0), specificity of 100.0% (95% ci 87.2-100.0), ppv of 100.0% (95% ci 76.8-100.0), and npv of 100.0% (95% ci 87.2-100.0) in the hkdr for people aged <20 years in the validation cohort. the sensitivity and ppv of this algorithm for identifying type 1 diabetes decreased to 50.0%-71.4% and 28.6%-62.5%, respectively, in people aged �20 years, which is expected because of the rarity of type 1 diabetes at older ages. an incident case of diabetes was identified by the first occurrence of any episode fulfilling the definition of diabetes and at least 2 years of diabetes-free observation prior. at least 1 year of surveillance from the date of diagnosis was required to enable discrimination of type 1 and type 2 diabetes. thus, although the database includes cases of diabetes from 1 january 2000 to 31 december 2016, incidence of diabetes was described from 1 january 2002 to 31 december 2015. the date of diagnosis was the date to first fulfil the qualifying event. we estimated sexspecific annual incidence rates of type 1 and type 2 diabetes. the numerator was the number of incident cases of diabetes in the hkdsd in each calendar year, and the denominator was the estimated hong kong population of the previous year at midyear as reported by the local census and statistics department. calculated rates were expressed per 100,000 person-years. we reported age-standardised rates (using the age structure of the world health organization standard population) for the entire population and for subgroups by sex and age categories (<20 years, 20 to <40 years, 40 to <60 years, �60 years). we calculated the annual percentage change (apc) and the average apc (aapc) in incidence rates with 95% ci by sex and by age bands. joinpoint regression analysis was used to describe incidence trends over time. the optimal number of line segments that best fit the pattern was identified, and apcs were computed for the slope before and after each joinpoint using regression analysis. because of an observed irregularity in the number of new cases of type 2 diabetes in 2004, trend analysis including reporting of apc and aapc for both type 2 and type 1 diabetes (for consistency) was restricted to the period between 1 january 2005 and 31 december 2015. in a sensitivity analysis, we conducted trend analysis for type 2 diabetes using restricted cubic spline, which allowed for a more flexible fitting of the change in incidence rates, and results are presented in the supporting information. statistical significance was set at p-value of <0.05. analysis was performed using sas version 9.4 (cary, nc) and joinpoint regression program version 4.6.0.0 (national cancer institute, bethesda, md). of 778,051 people captured in the hkdsd, we excluded 33,916 people who had diabetes codes but did not fulfil other criteria of diabetes. we further excluded 137,569 cases of prevalent diabetes (episodes fulfilling diabetes between 1 january 2000 and 31 december 2001) and 44,544 cases of diabetes that occurred between 1 january 2016 and 31 december 2016. the remaining 562,022 people with incident type 1 or type 2 diabetes occurring between 2002 and 2015 were included in the analysis (s1 fig, s1 table) . demographic and clinical characteristics of the cohort at diagnosis are detailed in s2 table. trends in incidence of type 1 diabetes using the derived algorithm, 2,426 people with newly diagnosed diabetes were classified as having type 1 diabetes, among whom 774 (31.9%) were aged <20 years and 845 (34.8%) and 807 (33.3%) were aged 20 to <40 years and �40 years, respectively (s1 table) . age-standardised incidence of type 1 diabetes increased from 2005 to 2015 in people aged <20 years in both sexes, from 3.5 (95% ci 2.2-4.9) to 5.3 (95% ci 3.4-7.1) per 100,000 person-years (aapc 3.6% [95% ci 0.2-7.1], p < 0.05) in boys and from 4.3 (95% ci 2.7-5.8) to 6.4 (95% ci 4.3-8.4) per 100,000 person-years (aapc 4.7% [95% ci 1.7-7.7], p < 0.05) in girls (table 1) . broken down into narrower age bands, the incidence of type 1 diabetes peaked in the age groups of 5-9 years in the female sex and 10-14 years in the male sex and declined with increasing age. among those aged 20 to <40 years and �40 years, incidence of type 1 diabetes remained stable over time (table 1 ). sex differences in the risk of type 1 diabetes were detected in the people aged <20 years but not in people aged �20 years. the rate ratio for type 1 diabetes was 1.38 (95% ci 1.10-1.37, p < 0.05) in girls compared with boys. among 559,596 incident cases of type 2 diabetes, 1,182 (0.2%) presented below 20 years of age, 22,924 (4.1%) presented in people aged 20 to <40 years, and 535,490 presented (95.7%) in people aged �40 years (s1 table) . the incidence rose with age and peaked in the age groups of 65-75 years in both men and women (fig 1) . table, the majority (76.2%) of the new episodes of type 2 diabetes in 2004 was identified by first-time use of noninsulin antihyperglycaemic drugs alone, suggesting that these occurrences could be prevalent cases initially diagnosed and followed outside of ha and later presenting to ha for continuation of existing treatment. incident cases captured in 2004 or before were excluded from subsequent trend analysis. an increase in the incidence of type 2 diabetes was observed in the <20 years and 20 to <40 years age groups (table 1 , fig 2a and 2b) . for people <20 years old, the age-standardised incidence of type 2 diabetes increased from 4.6 (95% ci 3.2-6.0) to 7.5 (95% ci 5.5-9.6) per 100,000 person-years ( 2) in men and women, respectively, for the entire period (p < 0.05). the sex disparity in incidence of type 2 diabetes varied by age. for people <20 years old, the incidence was disproportionately higher in girls than in boys, with an overall rate ratio of 1.22 (95% ci 1.10-1.37, p < 0.05). upon reaching young adulthood, the risk reversed, and men had higher incidence rates than women. in people aged 40 to <60 years, we detected an initial increase in incidence followed by stabilisation in both sexes (table 1, fig 2c) . in men, the incidence of type 2 diabetes increased from 697.0 (95% ci 681. using the territory-wide hkdsd, we conducted time trend analyses on the incidence of type 1 and type 2 diabetes in people in hong kong. between 2005 and 2015, the incidence of type 2 diabetes increased in people aged <20 years and 20 to <40 years, increased and then stabilised in people aged 40 to <60 years, and was unchanged in those aged �60 years. incidence of type 1 diabetes continued to climb in people aged <20 years but remained constant in other age groups. although the incidence of type 1 diabetes was the highest in those <20 years old, adult-onset type 1 diabetes accounted for over two-thirds of newly diagnosed cases during the surveillance period. among those <20 years old, type 2 diabetes contributed to more than half of the newly presented cases. the key strengths of this study were the use of population-level data through access to the electronic medical record system of the hong kong ha and its low susceptibility to selection bias. given the scarcity of population-level data on secular changes in diabetes incidence in asia, our results are timely in providing insights into the contemporary diabetes epidemic in this region. importantly, this study highlights the emerging problem of young-onset diabetes and calls for effective strategies to reduce modifiable risk factors for diabetes in this group. the multinational european diabetes (eurodiab) register, which included 29,311 incident cases of type 1 diabetes in youth aged <15 years recorded between 1989 and 2003, revealed regional differences in the trend of diabetes incidence [8] . in areas with a high burden of type 1 diabetes, such as the nordic countries, the united states, and australia, the incidence appeared to have stabilised over the past decade [9, 10, 11] . conversely, the incidence of type 1 diabetes has continued to rise in places of low disease prevalence, including east asia [12, 13] . based on a registry of 622 newly diagnosed cases of type 1 diabetes in children aged <15 years in shanghai, zhao and colleagues observed an increase in incidence from 1.5 per 100,000 person-years in 1997-2001 to 5.5 per 100,000 person-years in 2007-2011 [12] . from the 2012-2014 national health insurance service database containing 706 physician-reported cases of type 1 diabetes in children aged <15 years in south korea, kim and colleagues reported an incidence of 3.2 per 100,000 person-years, which was 2.3-fold higher compared with the rate recorded in the earlier period of 1995-2000 [13] . in the present study, we also detected an increase in the incidence of type 1 diabetes in children and adolescents, and the increase occurred in both sexes. in hong kong, the incidence of type 1 diabetes has not been determined since the last report 2 decades ago. based on retrospective retrieval of 255 paediatric cases of newly diagnosed diabetes between 1984 and 1996, huen and colleagues recorded an incidence of 1.4 per 100,000 person-years for type 1 diabetes in children aged <15 years in hong kong, which was considerably lower than our updated estimates of 5.3-6.4 per 100,000 person-years in a comparable age group [14] . our observations, together with others' observations showing a similar rise in incidence, remain unexplained, although environmental factors, including obesity, nutrition, climate, and infection, have been implicated in the induction and acceleration of beta cell destruction [15] . from surveys of hong kong school children, the prevalence of overweight or obesity rose from 11.6% in the mid-1990s to 16.7% in 2005 [16] , and the prevalence was 17.6% in primary school students and 19.9% in secondary school students in the last estimation in 2018 [17] . it is noteworthy that although the incidence was the highest in the paediatric population, adults aged >20 years accounted for two-thirds of the newly diagnosed cases in our database. in contrast to the rising trend of childhood-onset type 1 diabetes, the incidence of adult-onset type 1 diabetes has not increased. the growing number of young people acquiring type 2 diabetes is a major health concern that is now seen globally. in the present study, 60% of incident cases of diabetes in people aged <20 years were type 2 diabetes. the search for diabetes in youth registry, which systematically identified and followed youth with diabetes in the us, reported an annual increase of 4.8% in the incidence of type 2 diabetes in people aged <20 years between 2002 and 2012, from 7.0 to 9.0 per 100,000 person-years in boys and from 11.1 to 16.2 per 100,000 person-years in girls [18] . furthermore, the increase was larger in asians and pacific islanders (annual increase 16.0%) than europeans (annual increase 3.3%). similarly, wu and colleagues reported an increase in incidence from 0.7 to 3.6 per 100,000 person-years using a registry of 392 newly diagnosed cases of young-onset diabetes presented between 2007 and 2013 in zhejiang, china [19] . among those aged <20 years in hong kong, the average annual increase in incidence was 4.8%-5.9%, and the last recorded crude incidence rates in 2015 were 8.3 and 9.2 per 100,000 person-years in boys and girl, respectively, which were lower than the us figures but higher than rates in china. similarly, we detected an increase in incidence of type 2 diabetes in people aged 20 to <40 years in both sexes. besides exposure to an increasingly obesogenic environment, intrauterine effects from gestational diabetes and/or maternal obesity and exposure to present-day endocrine disruptors may be responsible [20] [21] [22] . it is also possible that the observed incidence trend of young-onset type 2 diabetes was the result of people seeking medical attention earlier in their disease trajectory rather than an actual fall in the age of diabetes development. in this regard, people who would develop diabetes were diagnosed progressively earlier, thus removing people from the undiagnosed pool who would have otherwise presented at an older age. in people aged 40 to <60 years, the incidence of type 2 diabetes in both sexes initially increased and then flattened from 2011/2012 onward. in women aged �60 years, the incidence was stable until 2011 and declined thereafter, whereas in men aged �60 years, the incidence remained constant. the absence of a rise might reflect levelling off in exposure to risk factors. in hong kong, the prevalence of obesity has been stable in men and has declined in women since the mid-1990s [23, 24] , which is attributable to a series of government-led health promotion initiatives targeting healthier lifestyles, such as the eatsmart programme and mandatory nutrition labelling during this period [25] . women are generally more receptive to health information and ready to adopt a healthy lifestyle compared with men, which might in part account for the sex difference in trends of obesity and type 2 diabetes [26] . cigarette smoking is linked to the development of type 2 diabetes [27] . antismoking advertising campaigns and government policy to ban smoking in many public areas have resulted in a reduction in smoking rates over the past 35 years, from 23.3% in 1982 to 10.0% in 2017 in hong kong [28] . lastly, saturation effect could be an explanatory factor, wherein increased health awareness and improved screening efforts during earlier periods have captured most of the high-risk individuals, thus depleting the pool of undiagnosed type 2 diabetes over time. in support of this, we observed a significant decline in hba1c values at diagnosis of type 2 diabetes from 2002 to 2011, possibly reflecting proactive case finding and earlier detection. although screening programmes for diabetes have not been formally introduced in hong kong, governmental policies to enhance primary care, including the dissemination of a reference framework for diabetes care, could have an effect toward improving diabetes detection [29, 30] . the increasing number of outpatient and inpatient attendances to public healthcare facilities over time also supports an increasing opportunity for diagnosing diabetes [31] . limited studies indicated interethnic variation in the risks for type 2 diabetes. alangh and colleagues reported 10-year secular trends in diabetes incidence in ontario, canada, and found that incidence increased moderately by 24% in the european population as compared with a 15-fold increase in the chinese population, in which the absolute incidence rate was twice that of europeans (19.6 versus 10.0 per 1,000 person-years) by 2005 [32] . from contemporary studies, the ageand sex-adjusted diabetes incidence rates among adults were 370 per 100,000 person-years in the united kingdom [33] , 398 per 100,000 person-years in sweden [34] , and 710 per 100,000 person-years in the us during the 2012-2014 period [35] . over a comparable reporting period, the rates were 1,099 and 949 per 100,000 person-years in men and women in our study, 830 per 100,000 person-years in korea [36] , and 800 per 100,000 person-years in taiwan [37] . differences in methods used to capture incident cases and diagnostic intensities would have influenced the estimates. allowing for these factors, available data, including those from the present study, suggest that the incidence of type 2 diabetes may be higher in east asians than europeans. although chinese people are leaner than europeans, for the same bmi, the former have more visceral fat, greater insulin resistance, and more metabolic complications [38] . moreover, low body weight is linked to poorer pancreatic beta cell reserve, and chinese people are more vulnerable to external factors, such as glucolipotoxicity, that trigger progressive decline in beta cell function [39] . a sharp peak in the incidence of type 2 diabetes was recorded in 2004, and this could be connected to the severe acute respiratory syndrome epidemic in 2003 in hong kong [40] . the excess of 21,000 new cases of type 2 diabetes in 2004 compared with 2003 might be due to heightened health vigilance at the aftermath of the epidemic, which prompted increased doctor visits. the modest dip in the number of new cases in the ensuing 3 years (from 2005 to 2007) compared with numbers between 2002 and 2003 could support earlier identification of cases during the transitory period, leaving fewer cases to be detected in subsequent years. the excess might also represent an injection of prevalent cases from the private sector to the public system in response to economic adversity. we acknowledge the following limitations in the study. an electronic medical record database was used to identify patients with diabetes, and we cannot exclude the possibility of incomplete capture. the data source included patients who attended only public healthcare facilities, and those receiving care in the private sector-who represent about 10% of the entire disease population-were not included. as such, the incidence rates as reported were likely underestimations of the actual figure by up to 10%. however, except for 2004, there was no evidence that the ratio of medical care in private sector versus public sector has changed over time, and therefore, this is unlikely to affect assessment of incidence trends. two-hour plasma glucose by an oral glucose tolerance test (ogtt) was not included as one of the qualifying criteria for diabetes, which could also underestimate incidence rates, especially in the paediatric population in whom hba1c alone has low sensitivity of diagnosing type 2 diabetes [41] . the categorisation of type 1 and type 2 diabetes was based on an algorithm rather than direct inspection of the clinical notes. although the algorithm was developed in an independent data set in which the diagnosis of type 1 diabetes was verified by reviewing medical records, the absence of confirmatory tests such as anti-islet cell antibodies or c-peptide levels could lead to incorrect differentiation of type 1 and type 2 diabetes, affecting the accuracy of the algorithm. misclassifying type 2 as type 1 diabetes would significantly inflate the incidence of type 1 diabetes, whereas the impact on incidence of type 2 diabetes was probably minimal. the probability of incorrect grouping would be greater in older patients in whom the algorithm performed less well, and estimates of incidence of type 1 diabetes in adults will require confirmation in other cohorts. because of limitations in details of the extracted information, we could not discern patients with other aetiologies of diabetes, such as maturity-onset diabetes of the young and secondary diabetes. owing to the asymptomatic nature of diabetes, diagnosis is often delayed. despite the good quality of the surveillance database, undiagnosed cases could not be captured, leading to underreporting of case burden. the recorded incidence rates were also sensitive to secular changes in people's health-seeking behaviour, screening practice, and prescription behaviour. in this report on the secular trend of the incidence of diabetes in hong kong, we revealed that the incidence of type 1 diabetes increased in people aged <20 years and was stable in other age groups. the incidence of type 2 diabetes also increased in people aged <40 years and accounted for over half of new cases of diabetes among people aged <20 years. in people aged �40 years, the incidence of type 2 diabetes remained constant. these observations provide an impetus for scaling up measures to prevent development of diabetes in people at risk. (a) incidence trends of type 2 diabetes in boys aged <20 years using restricted cubic spline. (b) incidence trends of type 2 diabetes in men aged 20 to <40 years using restricted cubic spline. (c) incidence trends of type 2 diabetes in men aged 40 to <60 years using restricted cubic spline. (d) incidence trends of type 2 diabetes in men aged �20 years using restricted cubic spline. (e) incidence trends of type 2 diabetes in girls aged <20 years using restricted cubic spline. (f) incidence trends of type 2 diabetes in women aged 20 to <40 years using restricted cubic spline. (g) incidence trends of type 2 diabetes in women aged 40 to <60 years using restricted cubic spline. 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region the government of the hong kong special administrative region. our partner for better health the government of the hong kong special administrative region. hong kong reference framework for diabetes care for adults in primary care settings. food and health bureau the government of the hong kong special administrative region rapid increase in diabetes incidence among chinese canadians between examining trends in type 2 diabetes incidence, prevalence and mortality in the uk between incidence, prevalence and mortality of type 2 diabetes requiring glucose-lowering treatment, and associated risks of cardiovascular complications: a nationwide study in sweden prevalence and incidence trends for diagnosed diabetes among adults aged 20 to 79 years trends in diabetes incidence in the last decade based on korean national health insurance claims data time trend analysis of the prevalence and incidence of diagnosed type 2 diabetes among adults in taiwan from 2000 to 2007: a populationbased study asians have lower body mass index but higher percent body fat than do whites: comparisons of anthropometric measurements diabetes in asia: epidemiology, risk factors, and pathophysiology a major outbreak of severe acute respiratory syndrome in hong kong utility of hemoglobin a(1c) for diagnosing prediabetes and diabetes in obese children and adolescents we acknowledge the hong kong hospital authority for providing the data for research. key: cord-000280-zyaj90nh authors: wong, samuel ys; wong, eliza ly; chor, josette; kung, kenny; chan, paul ks; wong, carmen; griffiths, sian m title: willingness to accept h1n1 pandemic influenza vaccine: a cross-sectional study of hong kong community nurses date: 2010-10-29 journal: bmc infect dis doi: 10.1186/1471-2334-10-316 sha: doc_id: 280 cord_uid: zyaj90nh background: the 2009 pandemic of influenza a (h1n1) infection has alerted many governments to make preparedness plan to control the spread of influenza a (h1n1) infection. vaccination for influenza is one of the most important primary preventative measures to reduce the disease burden. our study aims to assess the willingness of nurses who work for the community nursing service (cns) in hong kong on their acceptance of influenza a (h1n1) influenza vaccination. methods: 401 questionnaires were posted from june 24, 2009 to june 30, 2009 to community nurses with 67% response rate. results of the 267 respondents on their willingness to accept influenza a (h1n1) vaccine were analyzed. results: twenty-seven percent of respondents were willing to accept influenza vaccination if vaccines were available. having been vaccinated for seasonable influenza in the previous 12 months were significantly independently associated with their willingness to accept influenza a (h1n1) vaccination (or = 4.03; 95% ci: 2.03-7.98). conclusions: similar to previous findings conducted in hospital healthcare workers and nurses, we confirmed that the willingness of community nurses to accept influenza a (h1n1) vaccination is low. future studies that evaluate interventions to address nurses' specific concerns or interventions that aim to raise the awareness among nurses on the importance of influenza a (h1n1) vaccination to protect vulnerable patient populations is needed. the 2009 pandemic of influenza a (h1n1) infection has alerted many governments to make preparedness plan to control the spread of influenza a (h1n1) infection. with evidence on the effectiveness of vaccination in the control and prevention of seasonal influenza [1, 2] , vaccination for pandemic influenza is one of the most important primary preventative measures to reduce the disease burden associated with influenza a (h1n1) infection [3] . several high risk groups have been identified as "the priority group" to receive the influenza a (h1n1) vaccination and among these, healthcare workers have been identified "as a first priority" to be vaccinated against influenza a (h1n1) by the world health organization [4, 5] . although it is considered essential for all healthcare workers to be immunized against influenza a (h1n1) to prevent the spread of influenza a (h1n1) to patients as the pandemic evolves, previous studies that have examined the acceptability of seasonal influenza vaccination among healthcare workers have generally demonstrated a low acceptance rate of vaccination in this group [6, 7] . among all healthcare workers, nurses constitute the largest group with the highest frequency of contacts with patients and staff [8] . previous findings of the acceptability of seasonal influenza vaccination in nurses showed that their acceptance of vaccination was lowest among all healthcare workers [6, 7, 9, 10] . acceptability of influenza a (h1n1) vaccination in healthcare workers has been shown to be low [11] [12] [13] . a survey conducted in greece found that only 17% of hospital healthcare were willing to receive influenza a (h1n1) vaccination [11] . of all healthcare workers, nurses were found to have the lowest rate of acceptability of influenza a (h1n1) vaccination [12, 13] . a study of italian healthcare workers showed 31% of nurses willing to accept vaccination compared to 67% of physicians [12] . in a study conducted of hong kong healthcare workers in hospitals, it was found that only 25% of nurses were willing to accept influenza a (h1n1) vaccination, compared with 47% of doctors and 29% of allied professionals [13] . general practitioners working in the community in france also report a high rate of acceptability of influenza a (h1n1) vaccination at 62% [14] . it is therefore not surprising that a recent online poll conducted in the uk suggested that nurses may be unwilling to receive pandemic influenza vaccination [15] . in a cross-sectional survey that was conducted on experienced nurses who were members of the nursing professional organizations in hong kong, the vaccination rate for seasonal influenza vaccination was about 50% [16] . in a more recent survey that explored influenza a (h1n1) acceptance rate in the same group of nurses [17] , it was found that only 13% were willing to accept vaccination for influenza a (h1n1) compared to 38% who plan to receive the seasonal influenza vaccination. however, in the study, there was a low response rate of 28% of nurses with different clinical settings. there is a lack of studies in hong kong looking at influenza a (h1n1) vaccination acceptability particularly in the community setting. nurses who work in the community may be the first group to be in contact with patients who are affected with the influenza a(h1n1) infection. a recent study [18] showed differences in the concerns in using new vaccines during a pandemic than using established vaccine in a non-crisis situation. therefore, we undertook the current study to examine the willingness of frontline registered nurses who work in the community in hong kong to receive vaccination against influenza a (h1n1) at the time of a pandemic. all participants in this study were specially trained nurses, who provided nursing care and treatment for patients in their own homes (also known as community nursing service) in hong kong. the responsibility of these community nurses is to provide nursing care and health education to patients through home visits. cns nurses are employed by hospital authority in hong kong and provide continuity of care for patients who have been discharged from hospitals such that patients can recover in their own homes. community nurses were chosen because of their frequent contacts with patients in their homes which is likely to increase their risk for exposure to influenza. we have only included cns nurses who provide medical services in the study. the rest of the cns nurses (around 100 nurses) provide psychiatric services in the community. currently, there are a total of 401 nurses who provide medical related services for the community nursing service (cns) centres that are distributed among the 7 geographical clusters in hong kong (in hong kong, public hospital and primary care services are organized in 7 clusters that covers all of hong kong). in this study, twelve major cns centres were contacted first and all cns nurses were invited to participate in the current study through these 12 major centres. all 12 centres responded to this study and 270 questionnaires were returned with 267 completed questionnaires [19] . the response rate for this study was 67% and all questionnaires were received within a 2week period at a time when there was widespread h1n1 in the community. the survey was sent out from june 24 th to june 30 th , 2009 when the who influenza pandemic alert level assigned to h1n1 was phase 6. phase 6 signifies a widespread human infection, indicating that the virus has caused sustained community level outbreaks in at least one other country in another who region (who pandemic phase description). the pandemic in hong kong started on 1 st may, when a mexican traveller was confirmed with influenza a (h1n1). till the end of our data collection, there were 1389 confirmed cases and no death were reported. all general managers of the involved community nursing centres were contacted through telephone to obtain approval to send questionnaires to their nursing staff. in total, 401 self administered, anonymous questionnaires were posted to general managers of centres who then passed these questionnaires to the community nurses in their centres. the general managers of centres were then reminded via telephone during the period from 2 nd july and 8 th july one week after the questionnaires were sent out and advised to return the completed questionnaires within the week. once completed, questionnaires were collected and returned by their supervisors, except for one of the (sau mau ping) sub-offices, where nurses mailed back their questionnaires individually. all centres sent their questionnaires back after one telephone reminder. the last pile of completed questionnaires was received on 14 th july, 2009. the questionnaire consisted of six parts with 44 questions and the full questionnaire can be accessed by contacting the authors. the first four parts were based on a conceptual framework developed by patel et al [20] to guide systematic planning for community primary care service response to pandemic influenza with modifications to make it more relevant for nurses. we added a fifth part on psychological responses to pandemic influenza and a sixth part on demographics of respondents which were based on two studies previously published (one on general practitioners' response to sars and one on general public response to swine flu) [21, 22] . in summary, these sections were 1) clinical services change as a response to pandemic influenza; 2) internal environment changes as a response to pandemic influenza e.g. wearing of mask; 3) macro-environmental changes as a response to pandemic influenza e.g. use of guideline etc; 4) professional and public health responsibilities with respect to pandemic influenza; 5) attitude and psychological responses to pandemic influenza; and 6) demographics and year of education of respondents. the willingness to accept influenza a(h1n1) vaccination was asked in the professional and public health responsibility sections and the question "will you receive the new influenza a (h1n1) vaccine when it is available" was asked with a dichotomous "yes" or "no" response. for those who answered no, they were further asked to give their reasons for refusing to receive the vaccine. only results on willingness of accept influenza a (h1n1) vaccination and information related to the analysis on willingness to accept vaccine are reported in this paper. other results from this survey will be presented in a separate report. descriptive results were cross-tabulated. χ 2 test was used to examine characteristics between nurses who were willing to accept influenza a (h1n1) vaccination against those who were not willing to accept vaccine. univariate analysis was performed with demographic information (age, post year education and working district), personal protective behaviour (hand washing practice), experience of taking care of sars patients, and influenza vaccination in the previous 12 months as independent variables. dependent variables were the willingness to receive pandemic influenza vaccination. multiple logistic regression analysis was conducted to examine the relationship between pre-defined factors that we think might be associated with the acceptance of the influenza a (h1n1) vaccine when constructing the questionnaire and the dependent variable. the level of statistical significance was set at a p-value of ≤ 0.05. among the respondents ( table 1) , most of them were females who had worked an average of 8.8 years as a community nurse (ranging from 2 months to 32 years) and having been a registered nurse for 16.5 years (ranging from 1 year to 36 years). the mean age of respondents was 39.1 years and about a third (30%) had had the experience of dealing with sars. one third of them had received vaccination for seasonal influenza in the past 12 months. nurses from each geographical cluster in hong kong participated, with 11% of respondents working in hong kong island, 47% working in kowloon and 42% working in the new territories (hong kong is geographically divided into hong kong island, kowloon peninsula and the new territories). overall, 194 (73%) participants do not want to receive new influenza a (h1n1) vaccine when it is available. the reasons for their not intending to receive vaccination when it is available are summarised in table 2 . the characteristics of respondents who were willing to accept influenza a (h1n1) vaccination and with those who were not willing to accept influenza a (h1n1) influenza vaccination were compared by χ2 test and were presented table 1 . nurses who were willing to receive influenza a (h1n1) vaccine were different from nurses who were not willing to receive influenza a (h1n1) vaccine with respect to "being vaccinated against seasonal influenza vaccination in the previous 12 months". there were no statistical significant differences in other characteristics as analyzed by chi-square test. the relationship between demographic and other characteristics of the nursing respondents and their willingness to accept vaccination were analyzed further using forced entry logistic regressions (table 3) . having seasonal vaccination in the past 12 months was significantly independently associated with the willingness to accept influenza a (h1n1) vaccination (or = 4.03; 95% ic: 2.03-7.98). washing hands before and between patient contact, however, was negatively independently associated with willingness to accept influenza a (h1n1) vaccination (or = 0.49; 95% ic: 0.23-1.06). to confirm the results, we have also conducted backward logistic regression and the results also indicated that having seasonal vaccination in the past 12 months was significantly associated with the willingness to accept influenza a (h1n1) vaccination (or = 3.56, 95% ci: 1.87-6.80, p < 0.001). consistent with findings from previous surveys conducted in hospital healthcare workers and nurses [13, 17] , we have shown that the majority of nurses from community nursing services in hong kong were not willing to be vaccinated against h1n1 influenza when the vaccine becomes available. similar to findings from previous studies in healthcare workers [13, 17, 23, 24] , we showed that the major concerns for vaccination against pandemic influenza was fear of side effects and concern of efficacy of the new vaccine (table 2) . moreover, influenza vaccination in the previous 12 months was significantly associated with their willingness to accept the pandemic influenza vaccination. we also showed that in addition to previous vaccination with seasonal influenza, preventive behaviours such as frequent hand washing practice were independently associated with nurses' willingness to accept influenza a (h1n1) vaccination. we showed that "have been washing hands between and before patient contact" was negatively associated with willingness to accept vaccination independently although the reason for this is unclear and be a result of our relatively small sample. we can only postulate that the barrier to pandemic influenza vaccination is probably not related to the willingness of nurses to protect themselves against infections or their personal hygiene in general. researchers [17] have suggested one of the barriers to pandemic influenza vaccination in nurses was misconceptions about the purpose of vaccinations in which nurse might think that the aim of vaccination was for self protection rather than to protect at risk populations in contact with them [17, 23, 25] . specific vaccination policy for health care workers may improve vaccination in this group as nurses have different concerns and priorities when compared to the general public's concerns [17, 25] . although some may suggest that more educational programs for healthcare workers may be a solution to the low vaccination uptake [13] , studies have reported low influenza vaccination rates among healthcare workers even when educational programs were implemented [10] . other studies including randomized controlled trials also failed to show that better knowledge or educational programmes (27) other concerns (i.e. pregnancy, poor health status, and the severity of the epidemic of h1n1) 10 (<0.1) note: the total percentage exceeds 100% because multiple responses were allowed. were effective in increasing acceptability of vaccination in healthcare workers [26] . indeed, some suggested that educational campaigns based on the health belief model were unlikely to be enough to change healthcare workers' acceptability of vaccination as evidence showed that perceived seriousness of infection, acknowledgement of increased risk of infection and knowledge of vaccine being safe were unrelated to vaccine uptake in healthcare workers [26] . others suggested that educational programmes may be counter-productive as many of these healthcare workers do not perceive themselves to be at risk for contracting the infection. recently, ofstead et al [25] suggested that an ecological model, which included engaging organizations, communities and policy makers to create environments that were more conducive to risk reduction, might be more effective in increasing vaccination rates in healthcare workers. to our knowledge, this is the first study to explore the willingness of nurses who work in the community to be vaccinated for pandemic influenza and our results confirmed that their acceptability of influenza a (h1n1) vaccination is low. a strength of our study is our response rate of 67% which is higher than similar report conducted in hong kong with a response rate of 28% [18] . a limitation of our study is that we have only documented nurses' intentions of when a vaccine is available and not the actual uptake of vaccination. furthermore, all data from this study were from self-reports and recall bias, such recalling influenza vaccination in the previous year, might have occurred. a possible contributory factor e.g. recent episode of influenza-like illness which may influence the willingness of vaccination was not enquired. our analysis of results was limited by the relatively small sample size in nurses who are part of the community nursing service in hong kong with no information available on non respondents. however, our results are similar to recent studies conducted in hospital healthcare workers [13] and members of professional nursing organizations [17] in hong kong. consistent with previous findings which were conducted in healthcare workers and nurses [13, 17] , we confirm that the acceptance rate of pandemic influenza vaccination is low amongst community nurses. since community nurses are at high risk of contracting influenza infection, and play a significant role in caring for community cases, special attention should be paid to this group as successful vaccination strategy has been shown to be beneficial in disease transmission [27] . future work, including interventional studies evaluating potential interventions based on the ecological model or interventions that aim to increase awareness among nurses on the importance of vaccination in healthcare workers to protect vulnerable populations [16] is needed. the need to address low influenza vaccination rates in this high-risk group is urgent in the context of pandemic response. vaccines for seasonal and pandemic influenza efficacy and effectiveness of influenza vaccination stockpiling prepandemic influenza vaccines: a new cornerstone of pandemic preparedness plans healthcare workers should get top priority for vaccination against a/h1n1 flu, who says who global influenza preparedness plan: pandemic influenza preparedness and response: a who guidance document. world health organization correlation between healthcare workers' knowledge of influenza vaccine and vaccine receipt factors influencing update of influenza vaccination among hospital-based healthcare workers nurses' contacts and potential for infectious disease transmission influenza immunization: improving compliance of healthcare workers uptake of influenza vaccine by healthcare workers in an acute hospital in ireland low acceptance of vaccination against the 2009 pandemic influenza a(h1n1) among healthcare workers in greece behviours regarding preventive measures against pandemic h1n1 influenza among italian healthcare workers willingness of hong kong healthcare workers to accept pre-pandemic influenza vaccination at different who alert levels: two questionnaire surveys positive attitudes of french general practitioners towards a/ h1n1 influenza-pandemic vaccination: a missed opportunity to increase vaccination uptake in the general public? vaccine siva n: incidence of swine flu in england continues to fall, but winter surge is predicted impact of severe acute respiratory sundrome and the perceived avian influenza epidemic on the increased rate of influenza vaccination among nurses in hong kong exploring determinants of acceptance of the pandemic influenza a (h1n1) 2009 vaccination in nurse the public's acceptance of novel vaccines during a pandemic: a focus group study and its application to influence h1n1. emerg health threats j will the community nurse continue to function during h1n1 influenza pandemic: a cross-sectional study of hong kong community nurses? general practice and pandemic influenza: a framework for planning and comparison of plans in five countries primary care physicians in hong kong and canada-how did their practices differ during the sars epidemic? widespread public misconception in the early phase of the h1n1 influenza epidemic influenza vaccination among primary healthcare workers which determinants should be targeted to increase influenza vaccination uptake among healthcare workers in nursing homes? vaccine influenza vaccination among registered nurses: information receipt, knowledge, and decision-making at an institution with a multifaceted educational program promoting uptake of influenza vaccination among health care workers: a randomized controlled trial health care worker, vaccinate thyself: toward better compliance with influenza vaccination this study was supported by the research fund for the control of infectious diseases (rfcid), food and health bureau, hong kong sar government. we thank ting gao in data entry and her assistance in analysis of data. we also thank louisa lau for coordination with centres* of the community nursing service. we especially thank all nurses and nursing managers of the community nursing service of the hospital authority who participated in this study. all authors were involved in the design of the project. the survey tool was designed by sysw and elyw. the data collection, analysis and the results interpretation were carried by sysw and elyw in consultation with the team. the first draft of this article was composed by sysw and was revised critically by all authors. all authors have approved the final version of the manuscript. the authors declare that they have no competing interests. key: cord-263941-afxh7rks authors: yip, paul; chan, milton; so, b. k.; wat, k. p.; lam, kwok fai title: a decomposition analysis to examine the change in the number of recipients in the comprehensive social security assistance (cssa) system date: 2020-10-27 journal: china popul dev stud doi: 10.1007/s42379-020-00069-z sha: doc_id: 263941 cord_uid: afxh7rks social security is an important social and public policy measure to help address poverty in any contemporary society. the comprehensive social security assistance (cssa) system in hong kong provides a safety net for those aged children and adults below 65 years old who cannot support themselves financially. it is designed to bring their income up to a prescribed level to meet their basic needs. the rapid increase in social welfare expenditure in the last decade has become a concern to the hong kong sar government. the overall social welfare expenditure has accounted for nearly 15.6% of government expenditure in 2018, with the total amount increasing from $58 billion to $90 billion (an increase of 72.4%) for the period 2014-2018. however, the amount spent on cssa only increased from $20.7 billion to $22.3 billion with an increase of 7.7% only for the same period. the much slower magnitude of increase is related to the reduction in the number of cssa recipients, which decreased from 237,501 to 185,528 over the period. a decomposition method was used to assess the changes in the number of people in the cssa system. it showed that the rate of arriving into the system has been decreasing due to a robust economy with a very low unemployment rate; whereas moving out of the system has also been decreasing in the past 5 years. this phenomenon can be partly attributed to the widening of the income gap in the community in the period. despite the increase in population size, as long as employment conditions remain strong and the momentum of leaving the system can be maintained, the number of cssa recipients will continue to decrease. however, the results also suggested that a certain proportion of cssa recipients will not be able to move out of the system and have been trapped. some innovative methods to help them out of cssa are discussed. in view of the poor economic outlook arising from the covid-19 pandemic, it is important for the government to have effective measures to keep people in their jobs. if the unemployment rate will does not substantially increase and then increase of in cssa recipients can be contained. social security is an important social and public policy measure in any contemporary society. it is designed to bring low-income groups up to a prescribed level to meet their basic needs such that affected individuals and households can have some relief and reposition themselves for the next stages of life. it is particularly relevant to the key global concern of helping those who are unable to support themselves. "leave no one behind" is the slogan adopted by the united nations' 2030 sustainable development goals (united nations 2016), and ending poverty, everywhere, in all its forms, is the first of the sustainable development goals (sdg). there were 1.4 million people living below the poverty line in hong kong in 2018, accounting for 20.1% of the total population of 7.0 million, (poverty report 2018) . researchers have argued that poverty can be alleviated by social security through redistributing resources towards the poor (jones 1981; midgley 1984) , and local statistics prove that social security can make a significant difference to hong kong's poverty situation (poverty report 2018). for hong kong, after accounting for government recurrent cash benefits (including various kinds of social security schemes including cssa), the size of the poor population was reduced from 1.4 million to just over 1 million (14.7% of the population)-a 28% reduction in the size of the poverty population. hong kong's social service expenditure accounted for more than 15.6% of hong kong government expenditure, equal to about $90 billion, and it increased by 72.4% for the period 2014-2018 whereas the expenditure on cssa only increased by 7.7% from $20.7 billion to $22.3 billion for the same period. on the other hand, the non-means tested social security allowance (ssa) scheme for older adults aged 65 or over increased by 111.3% from $18.6 billion to $39.3 billion, which is a worrying economic sign for a rapidly ageing society. reducing the number of dependents in the social security system and maintaining a dynamic and vibrant economically active population is a high priority concern for policy makers of any government. a good understanding of the movement in and out of the social security system will be helpful in formulating effective interventions to reduce the number of social security recipients and to ensure financial sustainability of the system. yip et al. (2020) proposed a stochastic model to examine the in-and out-movement in the cssa scheme and identified that the group aged 30-49 with children had the largest impact on the number in the system. the results suggested that preventing this group from entering the cssa system would be more effective in reducing the number of cssa recipients than policies that aim to help them exit. it is a good illustration of the rose theorem, which asserts that the impact of "reducing a small risk in a large population" is more effective than "reducing a high risk in a small population" (rose 1992; yip et al. 2014 ). on the other hand, intergenerational poverty is of particular concern to policy makers (peng et al. 2019) . it is of great concern for helping those people who are trapped in poverty. upward mobility seems to be stagnant and poverty has become a structural problem in the community, especially among ethnic minorities (poverty report 2018). in this study, we adopt a decomposition analysis to assess the impact of population growth and age structure on the numbers of people moving in and out of the cssa scheme for the period 2014-2018. it is an improvement on earlier work that did not take into account the moving in and out mechanisms (yip et al. 2016) . here, the proposed method disentangles the overall effect of the changes in number of people in the cssa scheme at two different time points from the effect of demographic transition size and age structure. hong kong has a minimalist social welfare support system as compared to other western countries. the government promotes self-reliance, and the hong kong people are also not used to relying on handouts by the government. the amount of assistance under the cssa scheme is determined by the monthly income and recognised needs of a household. the difference between the total assessable monthly income of a household and its total monthly needs as recognised under the cssa scheme in terms of various types of payment will be the amount of assistance payable. when assessing a household's monthly income, earnings from employment and training/retraining allowance can be disregarded up to a prescribed level so as to provide an incentive to work and to recognise the additional expenditure incurred in attending training/retraining courses. the applicant must fulfil the residence requirement and pass both the income and asset tests. persons aged 15-59 in normal health should actively seek full-time jobs and participate in the support for selfreliance scheme (sfs) of the social welfare department (swd) if they are unemployed or working part-time or earning less than a reasonable wage as defined by swd. the cssa payments can be broadly classified into three types, namely, (a) standard rates; (b) supplements; and (c) special grants. under the cssa scheme, different standard rates are applicable to different categories of recipients. in addition, the cssa scheme provides various supplements to specified recipients, such as elderly persons, persons with disabilities or in ill-health, single parents and ablebodied adult recipients aged 60 to 64. a wide range of non-standard payments in the form of special grants are also payable to meet expenses such as rent, school fees and other educational expenses, and medically recommended diets/rehabilitation/ hygienic items. details can be seen at https ://www.swd.gov.hk/en/index /site_pubsv c/page_socse cu/sub_compr ehens /. the social welfare department has provided the number of cssa recipients by age group as of the end of 2014 and 2018, and the number of cssa recipients with duration on cssa of less than 1 year by age group. these allow us to estimate the number of arrivals to and removals from the cssa system (see table 1 ). the data excluded the 400,000 foreign domestic helpers who are not entitled to receive cssa. the dataset was categorized into cssa-arrival and cssa-removal, and by age group. in this study, we used 13 age group categories (0-4, 5-9, 10-14, 15-19, 20-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59, 60-64) . for those who aged over 65, a different scheme named social security allowance (ssa) is available. the objective of the ssa scheme is to provide a monthly allowance to hong kong residents who are severely disabled or who are 65 years old or above to meet special needs arising from disability or old age. the ssa scheme participants are not required to go through a means test. hence, the mobility out of the ssa scheme is non-existent as it is really a welfare payment for older adults depending on their needs and it is also non-contributory. hence, in this paper we only examine the movement of the cssa recipients of the group of aged 0-64 only. stratified data for the two time points 2014 and 2018 were then used to conduct the decomposition analysis. the cssa scheme in hong kong provides a safety net for those who cannot support themselves financially. it is designed to bring their income up to a prescribed level to meet their basic needs. the applicant must pass both the income and asset tests. the cssa cases of young people aged 18 or below is usually based on their parents/guardians. not all household members are eligible as each member needs to satisfy the criteria on income level and residence right. k age group; t year: equals 1 for 2014 and 2 for 2018; � p kt arrival rate of non-cssa population within group k in year t q kt removal rate of cssa population within group k in year t n kt net change in number of cssa population within group k in year t a kt − r kt the number of new arrivals and removals in year t can be expressed as the product of three components summing across age-size groups as in (2) and (4) respectively: (1) in eq. (2), the first component ( p kt ) refers to the age-specific arrival rate effect ( r1 ), which measures the arrival rate within age group k . the overall arrival rate is the sum of the specific arrival rates in the year. the second component ( x kt x .t ) refers to the agespecific effect ( q1 ), which measures the ratio of the kth age group with respect to the non-cssa population size. the third component ( x .t ) refers to the non-cssa population size effect ( p1). similarly, eq. (4) specifies the age-specific removal rate ( q kt ) effect ( r2 ), age-specific ( equations (2) and (4) are the product of the three components. the kitagawa's decomposition (kitagawa 1955 ) was used to differentiate the relative contributions of r1 and q1 and p1 , r2 and q2 and p2 effects from the change in overall newly arrival and removal population for the two time periods, respectively. with reference to eqs. (1) and (3), they are the product of two components. the decomposition can be simplified as below: the r , q and p effects sum up to give the change in the arrival number and removal number, thus giving the rate of change of cssa population size. the age composition effect non -cssa: the age composition effect cssa: the non -cssa population size effect ∶ p1 effect = ∑ k p k2 + p k1 2 the cssa population size effect: the arrival rate to cssa effect: the removal rate from cssa effect: we take the arrival size as the sign of the net change, i.e. net arrival. as removal size effect contributes a negative impact on arrival size effect, we can calculate the net change (arrival) size at time t from we can further calculate the difference between two different time points, i.e. change of net arrival size, from table 1 gives the changes in arrival and removal sizes, total cssa and non-cssa sizes, arrival and removal rates, and the decomposition of the changes (2018 minus 2014) into age ( q1 , q2 ), size ( p1 , p2 ) and rate ( r1 , r2 ) effects over the period 2014-2018 by 5-year age group. it showed a healthy sign that the number of people remaining in cssa has been continuously decreasing monotonically from 231,501 in 2014 to 185,528 in 2018, with 45,973 having left the cssa scheme for the whole period. the changes in the number of arrivals and removals in 2014-2018 were 3884 and 8480, respectively. both the arrival and removal rates have been decreasing, with the arrival rate reducing from 0.37 to 0.30%, and the rate of leaving reducing from 15.05 to 14.21%. thus, while fewer are entering the cssa system, there has also been a reduction.in the number of removals from cssa. table 1 suggests that increases in the population size for the period 2014-2018 resulted in an increase of 245 people into the cssa scheme. while the age effect also contributed 533 people to cssa as older people had a higher rate in joining the scheme. on the other hand, the improvement in the arrival rate contributed to a reduction of the number of cssa recipients (− 4662). the positive effect in containing the growth in cssa recipients is offset by the increase from the population growth (+ 245) and ageing of the non-cssa population (+533), with a net reduction − 3884 for the period 2014-2018. for the removal, decreases in the size of the cssa population accounted for the majority of the reduction of the number of removals, with a difference of − 6716 between 2014 and 2018, and the effect of ageing also slowing down the number of removals by − 140. more importantly, the reduction of removal rate between 2014 and 2018 contributed negatively to the number of removals (− 1624). the age group of 15-19 had the highest reduction of removal from the cssa, which might relate to the recent increase in youth unemployment (especially those who are not in school and unskilled) in hong kong. the negative sign suggest a stagnation of the cssa recipients in the system. however, there was a notable positive contribution made by improvements in employment among older adults aged 60-64 leaving the cssa system (+ 600). figure 1 depicts the size of age specific movement of cssa recipients in and out of the system for the period 2014-2018, with the size determined by the rate and associated population size. for the arrivals, there has been a consistent improvement in the reduction of cssa recipients for all age groups except for a slight increase among older adults (+ 119). however, as the ageing effect has become more significant than before, the size of the arrival for the age group 60-64 is still positive compared to 2014, as the improvement in its rate has completely been offset by the ageing effect despite improvements in preventing older adults from entering into the cssa system. for the removal, all of the age groups have experienced a reduction of removal rate of leaving the cssa system except for the age group 60-64. the reduction of the removal rate is worrying, as it indicates that nearly all of the cssa population found it harder to remove themselves from being a cssa recipient in 2018 compared to 2014. the increase in the number of removals in the 60-64 age group is noteworthy. this can be attributed to significant improvements in rehiring older adults into the workforce. the working participating rate among older adults in the period has improved due to incentivization and increases in job opportunities for the older population (table 2 ). the decomposition analysis allows us to examine the impact on the number of cssa recipients of changes in arrival and removal, population size and age distribution. it showed that the number of hong kong's cssa recipients has been decreasing for the period 2014-2018, mainly due to changes in the number of removals (277%) and arrivals (− 177%). the robust economy with a very low unemployment rate (3.0%) in hong kong helped to reduce the chance of becoming a cssa recipient from 0.37 to 0.30% during 2014-2018. on the other hand, the rate of removals decreased from 15.0 to 14.2%, indicating that it is more difficult than before to leave the cssa system. it has been shown that having a job is the most effective way to stay out of the cssa system (poverty report 2018). the government has tried to improve the incentive for low-skilled workers to join the work force by introducing the transport subsidy scheme in 2017, covering 25% of fares beyond hk$400 per month. with a threshold of hk$6500 income per month, within which applicants must fall, the scheme has excluded a large percentage of low-income workers with earnings just above the threshold that are struggling to have a reasonable quality of life. (sha et al. improving employment opportunities for older adults (aged 60-64) is important in keeping them out of cssa, therefore it is encouraging to see (as shown in table 1 ) that more people in this age group are keeping their work and/or getting a job such that they do not have to rely on the cssa system. some members wish to work and have the ability to work beyond their retirement age. the usual retirement fig. 1 changes in the number of arrivals and removals between 2014 and 2018 by five-year age group age in hong kong workforce is 60 years whereas the hong kong life expectancy has increased to 84 years old (c&sd 2020). removing barriers to working at older age would be a win-win scenario, especially in view of the shortage of workers due to hong kong's ageing society. some of the major barriers to retaining older adults in the workforce are the complicated procedures and expensive medical insurance, which is a major concern of many companies employing older adults (encouraging young-olds employment 2018). some infrastructure support and more flexible arrangements in the working environment would be conducive to increasing the working participation rate among older adults. for the removal rate, the propensity of leaving continues to decrease, reducing the number of removals and the number of cssa recipients remains high. apparently, inertia has been building in our system such that some people cannot move out from cssa. they are trapped in the system, or they have become the structural poor. for example, in view of the rising divorce rate in hong kong, single parents with young children that are lacking support from their families are particularly affected. without sufficient childcare service, the women would have more difficulty to participate in the workforce. furthermore, children from cssa families have been shown to have lower self-esteem (yip 2020) . to avoid issues of structural and stubborn poverty, we need to provide training and retraining programs for those who still have the ability to re-join the workforce. more family friendly working environments would be helpful to increase female labour participation to break down intergenerational poverty. another vulnerable group, the 150 migrants daily from mainland china might have an impact on the increase in the number of cssa recipients. however, in reality most of them do not resort to seeking support from the cssa (lee and chou 2018) . nevertheless, more effort should be made to engage mainland migrants successfully to remove barriers to their workforce participation. also, these migrants are mainly the spouses and children of hong kong residents, with socioeconomic profiles generally inferior to local residents. they often experience problems in finding jobs due to lack of skills, qualifications and the language barrier (government of hong kong special administrative region 2013). the new female migrants also have to look after young children. the insufficient child care support has made it difficult for the female migrants to participate in the work force which can create sort of structural financial dependence (yip 2020) . some poverty among new migrants also relates to the lack of recognition in hong kong of qualifications earned in mainland china, and this may constitute a waste of human capital (chou et al. 2014 ). the specific poverty rates in the groups of old age and large households are higher than the population average (lee and chou 2016) . also, it is a good time to re-examine the wage especially for the low skilled workers and outsourcing arrangement of the government services. sometimes, the working wage is so low that it discourages people looking for work. the low wage is indeed a complicated issue which depends on the supply and demand of the workforce. nevertheless, coupled with low wages, unfair treatment by some employers, limited amount of protection of the labour law, and extreme profit-seeking behaviour by outsourcing companies, these workers can find themselves unable to improve their quality of living through regular employment, and have to work overtime in order to satisfy their basic needs, at the expense of their own and family well-being and society's welfare. sometimes, they don't have a choice but by becoming a cssa recipient. the paper has examined the impact of the demographic transition on the number of cssa recipients. indeed, the cssa recipients also depends on the household structure and changes for the period 2014-2018. unfortunately, the cssa household data is not available for analysis. nevertheless, individuals under 18 would not be eligible to apply for cssa. hence, all the cssa recipients under 18 years old should be dependent of the adults recipients. changes in the age group 30-45 would be closely related to the number of recipients of aged 0-4. access to social security is a lifeline for the vulnerable groups in the community, and forms the major expenditure component of social welfare spending in hong kong. being employed is the most effective way to stay out of the cssa (poverty report 2018). the economy has been strong despite the relatively low working wage. the majority of recipients would not apply for the cssa if there is other alternatives. nevertheless, our economy remains outward-oriented and more than 87% (poverty report 2018) of our workforce (3.4 million out of 3.9 million) is employed in service industries. with the covid-19 pandemic and the drastic reduction of international and mainland tourism, the impact on the economy is yet to be fully revealed. due to the poor global economic outlook, unemployment is going to be increasing at an alarming rate, which will certainly have a negative impact on the number of cssa recipients. unfortunately, in the last few years the propensity to leave cssa is decreasing, creating an increased proportion of individuals being kept in cssa. hence, cssa has become somewhat of an ineffective crutch for these individuals, and the reliance on aid that is only intended to be transitional continues to leave a large proportion of beneficiaries feeling defeated and morally degraded . it is crucial to help those who are working to stay in work, otherwise even a small percentage change to the large overall working population will have a substantial impact on the number of cssa recipients. at the same time, by providing a reasonable wage it will also be able to retain/attract more people to joining the work force. trends in child poverty in hong kong immigrant families the hong kong federation of young groups. encouraging young-olds employment. government of hong kong special administrative region the common welfare: hong kong's social services components of a difference between two rates trends in elderly poverty in hong kong: a decomposition analysis explaining attitudes toward immigrants from mainland china in hong kong social security inequality and the third world determinants of poverty and their variation across the poverty spectrum: evidence from hong kong, a high-income society with a high poverty level government of hong kong special administrative region. hong kong poverty situation government of hong kong special administrative region. hong kong poverty situation the strategy of preventive medicine a review of the child care support for hong kong. social welfare department of the hong kong sar government optimal strategies for reducing number of people in the social security system a markov chain model for studying suicide dynamics: an illustration of the rose theorem assessing the impact of population dynamics on poverty measures: a decomposition analysis acknowledgements the authors are grateful to many useful comments from the two reviewers and the data made available by mr andrew kwan of the census and statistics department of the hong kong sar government. paul yip is a chair professor (population health) of the department of social work and social administration, the associate dean (research) of the faculty of social science, the founding director of the centre of suicide research and prevention at the university of hong kong. he served as the chairman of the committee of preventing students' suicide in hong kong and a member of the steering committee on population policy and an associate member of the central policy unit of the hong kong sar government. he is a recipient of a medal of honor (mh) of the hong kong sar government, the stengel research award, outstanding supervisor and researcher, knowledge exchange award of the university of hong kong; a distinguished alumnus of la trobe university, australia. he has published more than 500 research papers relating to population health and suicide prevention. mr. so's research is devoted to studying the analysis of singular partial differential equations, treating the lie groupoid defining them as the fundamental object. this novel viewpoint brings many open questions, some of them are currently under intense investigation. he also has interests in applying mathematical tools in solving real life problems. phd in actuarial science from the university of hong kong. he is a fellow of the society of actuaries, a fellow of the actuarial society of hong kong, a chartered enterprise risk analyst and a certified financial risk manager. he is currently a lecturer at the university of hong kong. he teaches courses mainly targeting risk management and statistics students in the department of statistics and actuarial science, aspiring to demonstrate to students the rigor and usefulness of quantitative analysis from theory to practice. key: cord-272759-dqkjofw2 authors: small, michael; tse, c.k.; walker, david m. title: super-spreaders and the rate of transmission of the sars virus date: 2006-03-15 journal: physica d doi: 10.1016/j.physd.2006.01.021 sha: doc_id: 272759 cord_uid: dqkjofw2 we describe a stochastic small-world network model of transmission of the sars virus. unlike the standard susceptible-infected-removed models of disease transmission, our model exhibits both geographically localised outbreaks and “super-spreaders”. moreover, the combination of localised and long range links allows for more accurate modelling of partial isolation and various public health policies. from this model, we derive an expression for the probability of a widespread outbreak and a condition to ensure that the epidemic is controlled. moreover, multiple simulations are used to make predictions of the likelihood of various eventual scenarios for fixed initial conditions. the main conclusions of this study are: (i) “super-spreaders” may occur even if the infectiousness of all infected individuals is constant; (ii) consistent with previous reports, extended exposure time beyond 3–5 days (i.e. significant nosocomial transmission) was the key factor in the severity of the sars outbreak in hong kong; and, (iii) the spread of sars can be effectively controlled by either limiting long range links (imposing a partial quarantine) or enforcing rapid hospitalisation and isolation of symptomatic individuals. the sars virus first appeared during october 2002 in the guangdong province of southern china. it then passed over the border to hong kong and from there spread to europe, africa, asia, australia and the americas [1] . the outbreak in 2003 infected 8422, killing 916 [2] . in this paper we focus on modelling the transmission of sars within hong kong. beside mainland china, hong kong suffered the greatest casualties [2] . in addition, the epidemiological data currently available for hong kong is far superior to that of the chinese mainland. 1 two characteristic features were observed during the sars outbreak in hong kong in 2003 (see fig. 1 ) [3, 4] : so-called super-spread events (sse), in which a single individual initiates a large number of cases; and persistent transmission within the community. two widely cited sses were observed early in the epidemic and have been the subject of much attention: at the amoy gardens housing estate and at the prince of wales hospital. epidemiological studies [5, 1] have found that in hong kong: • the fatality rate was approximately 17% (compared to 11% globally); • the mean incubation period was 6.4 days (range 2-10 days) [6] ; • the duration between onset of symptoms and hospitalisation was 3-5 days; and, • the mean number of individuals infected by each case during the initial phase of the epidemic (excluding sses) was 2.7 [4] . standard deterministic sir (susceptible-infected-removed) models of the spread of infectious diseases [7] make several important assumptions. an alternative approach [8] , particularly popular for the study of sexually transmitted diseases [9] [10] [11] , is to build an explicit network and model disease transmission along the links. under certain network structures, it is then possible to obtain a closed form study of the underlying transmission pattern [10, 12] . in particular, [12] studied the transmission of an epidemic among a population whose individuals are connected both locally and globally. from this, they were able to obtain an approximately poisson distribution for the contact distribution. in [13] , hufnagel and co-workers also studied the local and non-local transmission of epidemics. the main features modelled by [13] are local sir infection (with the usual stochastic differential equations) and long distance complex network links to model global aviation routes. they show that transmission dynamics with similar geographical dispersion to the 2003 sars outbreak can develop in the model. in contrast to [13] , we focus on abstract network models within a particular community. a similar global model of sars transmission could be achieved by introducing an aviation network model on top of the models presented in this paper. recently, both small-world (sw) and scale-free (sf) networks have been observed in many areas of natural and physical science, including social relationships [14, 15] . the important feature of both sw and sf networks is that they are highly connected: the average path length between random individuals is relatively short. moreover, for sf networks, the node degree distribution follows a scale-free distribution. hence, in many areas of natural and physical science, this new model structure has unveiled a rich range of behaviours. in this paper, we apply these methods to the modelling of the spread of sars in hong kong; transmission is only allowed to occur along a limited number of direct links between individuals. by doing this, we will avoid making one of the assumptions underlying standard susceptible-infected-removed (sir) models: a homogeneous fully connected population. the sir model assumes that all individuals are susceptible to the disease and all suffer an equal, small, positive probability of contracting the virus. this homogeneous model leads to a continuous and smooth inter-day distribution of infections. irregularities in this are usually attributed to random variation and non-stationarity in the model parameters. in proposing an alternative to the standard sir model, we do not claim that the sir model has failed. certainly, the power of any model lies in its simplicity, and its ability to capture the important features of a system. hence, like the sir model, the complex network model that we describe here is very simple and is described by a very small number of parameters. analysis of the spread of sars with sir models shows good correlation between decreasing infection rate r and the introduction of various governmental control measures: quarantine and public awareness campaigns [16] . however, these results are based on a very simplistic model, and localised outbreaks (such as the incident at amoy gardens) are not modelled very well. while it is impossible to predict the occurrence of such outbreaks, sw-sf models provide a more realistic physical model of the relationships between individuals in a community and will therefore provide a better picture of the true disease dynamics. note that, since one cannot actually predict when a particular sse will occur, one cannot accurately model the timing of the peak in the time series of fig. 1 . moreover, it is not possible to accurately model the initial sse at the prince of wales hospital, which "kick started" the sars outbreak in hong kong. to include the same initial spread of sars in hong kong, via a rather singular sse, that sse must be included explicitly in the model. in other areas where sw-sf models have been applied, a rich range of behaviours has been observed. unlike standard differential equation based models, sw and/or sf structures model the underlying network of connections between individuals directly. our model is designed to capture explicitly the small-world features of social interaction. our model is not scale-free. to generate a scale-free model for disease epidemics, one needs a power-law distribution of infection links; we consider the theoretical implementation of such a model in a separate paper [16] . finally, we will also provide one possible answer to the question posed by galvani and may [17] : "were sars superspreaders anomalies, or are super-spreaders characteristic of most infectious diseases?" [17] . we show that, even with uniform rates of infection, super-spreaders will occur, to varying degrees, in a small-world or scale-free [16] network. the implication is that super-spreaders are not (necessarily) a result of variable rate of infection. nonetheless, we argue that the sars outbreak in hong kong was initiated by a single, rather unfortunate, super-spreader event. in the next section, we describe our model and study its behaviour analytically. subsequent sections present some numerical simulations and a summary of our results. in the following subsections, we define our model structure (section 2.1) and derive some analytical results concerning the likelihood of a widespread outbreak (section 2.2). our aim is to capture accurately the qualitative features of the sars epidemic with the simplest model (the fewest parameters). we propose four distinct states. individuals can be susceptible (s), prone (p), infected (i), or removed (r). the transmission path is depicted in fig. 2 . infected individuals can cause susceptible individuals, to whom they are linked, to become prone with some probability ( p 1 or p 2 ). by infection we mean the transition from the susceptible state to the prone state. infected individuals can cause their immediate neighbours to become infected with probability p 1 ; long range links cause infection with probability p 2 . prone individuals become infected with probability r 0 and, finally, infected individuals become removed with probability r 1 . just as in the sir model, we do not distinguish fatalities from recoveries: in either case, the individuals are assumed to have acquired immunity. the model states that we describe here bear a close correspondence to the four states of the seir model. the prone state is analogous to the exposed (e) state in the seir model. we choose to use the new term p because the epidemiological state is slightly different. by prone we mean both the infected but not infectious (incubation) period and the pre-symptomatic period. for sars, all infections in hong kong could be traced to contact with a symptomatic individual. 2 hence, for the purposes of modelling transmission, we assume that, during the pre-symptomatic period, there is no chance of transmission. moreover, to calibrate our model with the observed data (which, by definition, are hospital admissions), we further prescribe that the time between the onset of symptoms and hospitalisation is constant (or, equivalently, follows a stationary unimodal distribution). in our model we explicitly model the geographical structure of the population. we include both "local" and "non-local" links. because of common transmission of sars within specific housing estates and districts in hong kong, and the (both real and perceived) risk of transmission in workplaces (primarily hospitals and schools) or other public areas, we model these two types of transmission separately. the geographical arrangement of nodes represents the residence of each individual. so, by "local" transmission, we mean only transmission within a family unit (i.e. residents of a single flat), or between adjacent flats. 3 hence, "non-local" transmission the top panel depicts the transmission state diagram: s to p based on the sw structure and the infection probabilities p 1,2 ; p to i with probability r 0 ; and i to r with probability r 1 . the lower panel depicts the distinction between "local" (i.e. short range) and "non-local" (long range) network links. the lower panel shows the arrangement of nodes in a small-world network. the black (infected) node may infect its four immediate neighbours with probability p 1 and three other nodes (hashed) with probability p 2 . refers to transmission between non-family members due to the mixing of individuals in public spaces. in the context of the sars outbreak in hong kong, this would include transmission within hospitals, schools and public spaces. in our model, we expect sse to be represented through a single node with a large number of non-local connections. 4 we fix the population n and assume that there are no other additions to, or deletions from, the population from any other cause for the duration of each simulation. the population of n nodes is arranged in a regular grid, of side length l (l 2 = n ), and each node is connected directly to n 1 immediate neighbours. 5 an infected individual will infect each of its n 1 neighbours (provided that they are still susceptible) with probability p 1 . furthermore, each node has n 2 non-local (i.e. long distance) links (see fig. 2 ). these are links to nodes that are geographically remote from one another; infection occurs along these pathways with probability p 2 . for each node i, the number n (i) 2 is fixed, and so are the links to its n (i) 2 remote neighbours once they are established. the number n (i) 2 is chosen to be proportional to a decaying exponential f x (x) ∝ e − x µ with parameter µ proportional to the expected (average) number of 4 as we will see in what follows, the number of local connections is constant for all nodes. 5 the grid is assumed to be topologically equivalent to the surface of an annulus in three dimensions, that is, nodes (1, 1) and (l , l) are neighbours. links to remote nodes, where n (i) it is the inclusion of non-local links with a random number of links that can give rise to the network's sw (and, in other cases not considered here, sf) structure. in this paper, we assign an exponentially decaying probability distribution to any number of links, and (for uni-directional links) this is sufficient to generate the necessary sw properties. an sf network requires a power-law distribution of the number of links (which can consequently lead to more nodes with many more links) and we do not examine that case here. the sf distribution of the induced network of actual infections has been considered elsewhere [16] . it is worth considering that, for the model that we present here, the links between nodes are uni-directional. that is, infection only spreads in one direction. clearly, the true network of social interaction consists of bi-directional links. but, for the purposes of simulating disease transmission, unidirectional links appear to be a sufficient approximation. the consequence of this is that it becomes easier to generate the small-world (and elsewhere the scale-free) network. finally, for each simulation we seed the model with one randomly chosen initial infection. we expect that computational simulations of this network will show that infection spreads locally, just as sars spread within particular geographical regions of hong kong. moreover, the system can also exhibit non-local infection, as a single individual may infect individuals in distant communities. occasionally, individuals will infect a large number of others, exactly as was observed at the start of the sars epidemic in hong kong (an sse). however, unlike the start of the sars epidemic in hong kong, because we seed our population with a single infectious individual, we do not expect to see the initial sse triggered by that individual (except by chance). therefore, the initial growth of transmission in our model is exponential rather than an sse. the only way to overcome this is to include explicitly the "seed" sse in the model, regardless of network topology. the epidemic will eventually be contained if the rate of infection is lower than the rate of removal. intuitively, provided that (n 1 p 1 + µp 2 ) r 1 , one would expect the disease to become endemic; conversely, if (n 1 p 1 +µp 2 ) r 1 , the disease will be contained. in what follows, we study this condition more precisely. moreover, with this model we can analytically compute the probability of an outbreak being self-terminating. for a single infectious node, the probability of no further infections on a given day is given by hence the probability of no further infections from this node can be closely approximated by the infinite geometric series using the average p no1 computed in eq. (2): provided that |p no1 (1 − r 1 )| < 1. upon substitution of eq. (2) into (3), we find that eq. (4) is the probability of no infections from a given individual, and is therefore a weak lower bound on the probability of no general outbreak. now, let us denote the probability of no further infections occurring, given that there are k infectious nodes by = p (k) none = prob(no further infection | k infectious nodes) where, for notational convenience, we will drop the subscript on p none . treating infections as discrete events (i.e. they occur one at a time), we have that (1− p k ) is the probability of at least one further infection from k infectious nodes. the probability that the epidemic will terminate is given by where p = p none is given by eq. (4). by expanding eq. (5) and comparing to the pentagonal number theorem, 6 we find that eq. (5) can be rewritten as an infinite sum (1 − p n ) = p + p 2 − p 5 − p 7 6 this result was originally proved by euler in 1775. where the sequence of indices 0, 1, 2, 5, 7, 12, 15, 22, 26, 35 . . . is the generalised pentagonal numbers (described as sequence a001318 in [18] ). eq. (6) may also be re-written in terms of the dedekind eta function, but for the purposes of this discussion it is unnecessary to do so. nonetheless, for 0 ≤ p < 1 this sequence converges fairly rapidly as the order of the exponent increases. the exact 7 probability of a general outbreak can alternatively be obtained by using a branching process method. following [19] , we define the probability generating function for the number of secondary cases produced by a single infectious case in a day. then the probability generating function for the overall number of secondary infections from a single primary case is one can then obtain the probability of no general outbreak (i.e. the probability of the disease not becoming endemic) as the smallest solution x ∈ [0, 1] of g(x) = x. unfortunately, eq. (8) cannot be readily used for further analysis. similarly, although eq. (5) can be computed easily, it is not in a form that is immediately amenable for further analysis. however, since p safe ≥ p none , it is clear that 1 will make p safe ≈ 0. hence, either µ 1 or p 2 ≈ 1 will lead to widespread infection (as expected). differentiating (5) with respect to (1 − p 1 ) n 1 , we can easily verify that p safe is a monotonic function of both p 1 and n 1 . one can therefore observe that p safe ≈ 0 if p 1 ≈ 1 or n 1 1. the most severe limitation on eq. (5), and also eqs. (7) and (8) , is that we assume that no infected nodes have common neighbours, and that all of the neighbours are susceptible. in reality, the number of potential infections is limited by the fact that some of the potential neighbours are already infected. it is therefore important to estimate the number of neighbours of an infected node that have not been infected. this is equivalent to estimating the ratio of local and non-local infections in an epidemic. 8 one can consider the network of infected individuals as consisting of a number of "clumps": one clump 7 because of the assumption that infections occur individually and sequentially, the branching process in eq. (5) is only an approximation to the solution of eq. (8). 8 we can achieve this as follows. suppose that there are no non-local infections (i.e. p 2 = 0) and that infections grow in a single (roughly spherical) "clump". then, if the clump consists of i (t) individuals, then the radius of this for each non-local infection (i.e. each clump is seeded by a nonlocal transmission; all other transmissions within that clump are local). provided p 2 > 0, this implies that, as the clump gets bigger, the probability of any given infection being a long range infection will increase. conversely, as the number of clumps increases, the probability of local infection (relative to nonlocal infection) will increase. 9 let us now estimate the expected number of connections from an infected node. let n s denote the expected number of susceptible nodes linked to a random node. if this node is the result of a non-local infection, then we suppose that n s = n 1 + µ; however, if this is the result of a short range infection, then this number should be lower (certainly no more than µ + n 1 − 1). now, where k is the proportion of local links that support possible infection and 0 < k ≤ n 1 −1 n 1 . hence, from the preceding geometric argument, if infection grows in a single clump, then k ≈ 1 2 . moreover, k < 1 2 only if nodes remain infected when they are on the interior of such "clump" (i.e. when r 1 is very low). we would therefore expect that 1 2 ≤ k ≤ n 1 −1 n 1 . note that k is not a model parameter, but rather it is a term in the model that will both depend on the various model parameters and vary with time. finally, we now consider the rate of transmission. let p(t), i (t) and r(t) be the number of prone, infected and removed individuals at time t (in days). the probabilities r 0 and r 1 can therefore be considered as the rates at which prone nodes become infectious and infectious nodes become removed (respectively). similarly, (n 1 p 1 k+µp 2 )s(t)i (t) is the expected number of new infections. suppose that s(t) r(t) + i (t) + clump will be i (t) π and the number of susceptible individuals is 2 √ i (t)π . now, further suppose that all nodes in the clump are infectious (i.e. r 1 = 0), then the mean number of links per infected individual is 2 π i (t) . even with r 1 > 0, as the clump grows, there are, on average, fewer potential infection paths. 9 moreover, one can estimate the number of clumps k . observe that k ≈ µp 2 n 1 p 1 +µp 2 × (number of infections). more precisely, n 1 p 2 (n 1 k 2 p 1 + µp 2 ) + µp 2 (n 1 kp 1 + µp 2 ) × i where i is the total number of infections. where n k = (n 1 p 1 k + µp 2 ) is the expected number of links for each infectious node. we are now modelling the inter-day process assuming discrete day-to-day dynamics. the reason for this approximation is that the available time series data (which will be the basis of our comparison) is similarly course-grained. assuming that the population is seeded with a single infectious individual, the solution of eq. (11) is given by where is the matrix of eigenvectors and is formed from the corresponding eigenvalues, given by it then follows that the system has a marginally stable focus (i.e. the epidemic will terminate) if |λ 2,3 | < 1, i.e. n k < r 1 (13) n k r 0 < (2 − r 0 )(2 − r 1 ). the second condition (14) is only violated if n k > 1, which would also violate condition (13) . therefore, the epidemic is controllable provided that n k = n 1 p 1 k + µp 2 < r 1 . the right hand side of this inequality is the rate of infection and the left hand side is the rate of removal, as expected. in fact, this result is exactly analogous to the equivalent result for the continuous sir model [7] . moreover, computationally, we can see that, as r 0 or n k increases, then the rate of growth of the epidemic also increases. conversely, as r 1 increases, the rate of growth decreases. this is as one would expect, as increasing r 1 will decrease the number of infectious individuals while increasing either r 0 or n k increases this quantity. in the following subsections, we confirm the preceding relationships and numerically explore the behaviour of our models under a variety of conditions. as stated, our model has seven explicit parameters: l, n 1 , µ, p 1 , p 2 , r 1 , and r 2 . for the population of hong kong, we set l = 2700 (n = l 2 = 7,290,000). we arbitrarily choose n 1 = 4 and set e(n 2 ) = µ = 7 [16] . one further parameter is the time interval between successive steps in the discrete time simulations from our model. we choose the natural scale of one day. however, it is not obvious that this is the best choice. given that the data is discretised to this interval, it is perhaps the best choice in this situation. nonetheless, to confirm that this choice is appropriate, we have repeated our analysis with both longer and shorter time steps. the results are equivalent. the average incubation period between infection and an individual becoming symptomatic is 6.4 days [6] . the number of days in the prone state can therefore be modelled as the result of a series of independent bernoulli trials with a mean 1 r 0 and so it follows a geometric distribution f x (x) = (1 − p) x−1 p. 10 for a general disease model, it would possibly be more appropriate to have a separate state for the pre-symptomatic but infectious period. although contact tracing of all sars patients in hong kong has demonstrated that this is not a significant period for sars, we have repeated the simulations with this state. if the hiatus in this state is relatively short, the results are not altered significantly. in a similar spirit, the time before hospitalisation is 3-5 days, and we model this as a series of independent bernoulli trials. in an effort to establish the degree to which hospital transmission in our model matches what was observed, we first assume that hospitalisation is equivalent to isolation of infectious individuals. that is, we suppose that infectious individuals are only infectious for 3-5 days. the current weight of evidence suggests that hospital transmission was a crucial factor for the sars outbreak in hong kong during 2003. we will show that this is also the case for our model. hence, we suppose for now that the average amount of time prior to isolation is 4 days (we will consider larger values later). in our model, the number of days prior to hospitalisation is also made to follow a geometric distribution with mean 1 r 1 . hence, the only free parameters are µ, p 1 and p 2 . without active control, we also know that the average number of new infections per case (excluding sses) is 2.7 [4] . in this state, each infectious individual will infect, on average, n 1 p 1 + e(n 2 ) = µ and we suppose that the time before hospitalisation is d days, we have we set d = 4 and therefore p 1 ≈ 1 n 1 (0.675 − µp 2 ) = 0.135 − µ n 1 p 2 . in subsequent simulations, we also consider d = 3, 4, 6 and also a larger number of new infections than 2.7. 10 we do it this way simply because it is convenient to do so. for simulation purposes, this sequence of bernoulli trials is both easy to implement and (more importantly) requires very modest computational storage resources. in each case, the results are equivalent to those presented here. however, we maintain the values described above in the following discussion. any deviation of results between these and other values will be highlighted in the text. our initial model parameters are therefore [16] : note that, because we have the possibility of p to i transition after zero days, r 0 = 1 7.4 rather than 1 6.4 . this does not have a significant effect on our results; it is merely a computational convenience. now, from eq. (15) we can deduce that the rate of growth of infection is approximately which, for r 1 = 0.25, yields either a growth rate significantly less than exhibited in the data or rates of infection significantly greater. even for reasonable variation of d and the average number of secondary infections, we obtain similar results. hence, we conclude that the assumption of no nosocomial transmission is inconsistent with the observed data. increasing the average infectious time to 6 days gives a substantially higher rate of infection: consistent with the observed data. subject to eq. (5), we explore which parameter values give a significant probability of the epidemic becoming endemic. from eq. (13), we have that p safe = 1 if n k < r 1 . consistent with the discussion of the preceding section, we start with the assumption that k = n 1 −1 n 1 and set n 1 = 4 and µ = 7. fig. 3 is a plot of the probability of complete infection for various parameter values estimated from the data and eq. (5). we see that there is close agreement between the theoretical and experimental results. moreover, we note that a smaller value of k is appropriate for scenarios with a relatively high proportion of local spreading (i.e. p 1 larger and p 2 ≈ 0). this is consistent with the case of spreading within a single clump, and we approach the situation of k = 1 2 . however, in these simulations the best choice is k > 1 2 in all cases. only for extremely small values of r 1 and p 2 would we expect smaller values of k. typically, k = n 1 −1 n 1 = 3 4 seems to be a good choice. furthermore, in fig. 3 it is evident that the greatest probability of an epidemic becoming endemic is when there is both local and non-local infection. in the model that we have constructed here, local infection spreads approximately geometrically, 11 while non-local infection spreads exponentially. yet, it is some combination of both that provided the greatest possibility of an outbreak spreading without control. clearly, exponential growth will lead (all else being equal) to more rapid growth of an epidemic than geometric growth. but, by combining some geometric growth, the epidemic becomes even more dangerous. it seems that the additional local transmissions allow each nonlocal transmission the possibility of seeding a new infection cluster (rather than just a single point), and each new cluster is more difficult to eradicate than a single point infection. fig. 4 depicts level curves for the probability of fixed levels of infection. that is, we compute the parameter values p 1,2 ∈ [0, 1] and r 1 ∈ [0.1, 0.5] required to achieve specific values of p safe . we see that only for p 1,2 0.2 is the outbreak likely to be controlled. moreover, the variation with r 1 is not critical i.e. the range of behaviour for specific p 1,2 is not great. finally, in fig. 5 we plot the probability of the epidemic being controlled for various values of µ with p 1,2 ∈ [0, 1], r 0 = 0.1 and r 1 = 0.25. consistent with fig. 4 , results for different values of r 0,1 did not change significantly. moreover, from fig. 5 we see that only for µ > 2 does the infection probability p 2 have a significant effect. that is, to limit long range infection, one should aim to reduce the average number of long range links below 2. we find that, for all values of p 1,2 and µ > 2, there was remarkably little variation in the value of p safe . however, the rate of infection (eq. (15)) did change significantly. subject to the choice of parameters in the previous sections, we now simulate the expected dynamics and compare this to the theoretical bounds of section 2.2. according to theory, restricting the infectious period to five or fewer days does not yield a growth rate large enough to be consistent with the observed data. we test that assertion numerically and find that the observed data (over 1000 individuals infected after 50 days) is inconsistent with the simulation for r 1 = 0.25. however, by lowering r 1 to 0.165 (and therefore increasing the mean infectious period to six days, we achieve results more consistent with the observed data. we see that only with r 1 ≥ 0.165 do we obtain results for which the true data is not statistically atypical. moreover, this result is robust to moderate changes of the other relevant parameters, as illustrated in fig. 6 . we conclude that the obtained results for which the true data is not atypical; we require r 1 ≥ 0.165 (i.e. a mean exposure time of six or more days). moreover, we see from fig. 6 that widespread infection is associated with a large number of clusters. the results of the next section corroborate this. to examine the role of clustering more closely, fig. 7 is a snapshot of a single simulation for parameter values r 1 = 0.25 and p 2 = 0.006. this simulation shows sse resulting from clustering and highly connected nodes. moreover, the gradual spread of the disease within a single cluster is evident; one can see that the number of clusters is far less than the number of infections. time series of the infection total appear qualitatively similar to the hong kong sars data. specifically, burstiness typical of sses is evident. however, the quantitative behaviour of this model is remarkably different to the dynamics observed in the sars outbreak. the daily number of reported infections in fig. 1 far exceeds the total number of active infected and prone individuals in fig. 7 . finally, we provide simulations of the hong kong epidemic and from multiple simulations estimate the likelihood of various outcomes based on the model. we initiate the model with a single infected individual and a relatively low removal rate r 1 . fig. 8 depicts our results. we can see from fig. 8 that many of the features of the true data are reproduced well in the simulations. however, two important aspects of the simulations are not sufficiently similar to the data. firstly, the initial spreading of the disease is exponential, rather than the single sse observed in the real data. secondly, the magnitude of the sses in the simulations is somewhat smaller than the largest sses in the data. this second aspect can be overcome by simply altering the distribution of non-local links. in [16] we describe how a power-law distribution of links can lead to many more extreme events. conversely, the initial sse in the data cannot be modelled well by our simulations, except by chance. therefore, to achieve similar initial events, we would expect that we would have to execute many simulations (and choose only those that suit our purpose), or simply build the sse into the model. neither of these approaches are desirable. we prefer to focus on the possibility of sses occurring randomly, without explicitly adding them in the model. hence, we do see sses, but not necessarily immediately after the start of the simulation (as we suppose occurred in the true data). we now wish to demonstrated how the sw model described here improves on stochastic sir-type models [7] . one very simple way to achieve this is to compare the distribution of statistic values measured from simulations of either type of model to the true data. in fig. 9 we do this, and we find that the small-world model exhibits statistical properties much closer to the observed data. in fig. 9 we compare the results for the sirtype model (with stochastic inputs) to the sw model described in this paper. by generating multiple simulations of both models and estimating simple statistical measures from both sets of simulations, we see that the model dynamics of the sw model are much closer to the true data. assuming that this model and parameters are accurate, or at least appropriate, we compute the likely behaviour for various epidemics. we generated 1000 realisations of the model depicted in fig. 8 and computed the total number of casualties. fig. 10 is a plot of the probability distribution of the number of fatalities for these simulations, and fig. 11 is the probability distribution for the daily number of infections. we found that the probability of infecting fewer than 20 people was approximately 0.18, while the probability of infecting more than 1000 was 0.27. one can see that, with respect to these gross statistics, the true situation for hong kong (1755 casualties) is quite typical. 12 it is interesting to note, however, that there is a large variation in the number of casualties. in all cases, the parameter values of fig. 8 provided effective control of sars transmission after approximately 150 days. from these simulations, we therefore conclude that, with effective control measures in place, the likelihood of a significant outbreak is low. 12 from 1000 simulations, 106 exhibited a larger number of casualties. we summarise the main results of the preceding sections as follows. • the probability of the disease spread being controlled, p safe , is approximately • the epidemic is under control if n k = n 1 kp 1 + µp 2 < r 1 (section 2.2). • for the endemic case, the rate of growth of infection is • this model exhibits behaviour consistent with both sses and persistent localised transmission (section 3.4). more extreme sses can be observed simply by fattening the tail of the distribution of links. by assigning a power-law distribution to the number of nonlocal links that a node has, one can readily obtain sse involving many hundreds of secondary infections from a single source. • an sse does not imply highly infectious individuals, only highly connected ones (section 3.4). • theoretical results and model simulations are unlike the true data, unless exposure time is significantly greater than an average of three days (sections 2.2 and 3.3). if the exposure time is three days or less, the rate of growth of the epidemic is significantly lower than that observed in the true data. • nosocomial transmission was therefore a key factor in the acuteness of the sars epidemic in hong kong in 2003. effective control of hospital transmissions would have prevented a serious outbreak (section 3.3). with respect to nosocomial transmission, our model therefore confirms what has been observed independently, and suggested by many authors. • simulations of our model, with minimal parameter variation, produced dynamics indistinguishable from the true data. these same parameter values exhibit a wide variety of behaviours (section 3.5). hence, any effort to actually obtain maximum likelihood parameter estimates from the observed data is futile. despite this, our calculations show that the true data is certainly typical of our models. moreover, our models exhibit a marked long-tailedness both in infection times and epidemic lifetimes. • the likelihood of infecting fewer than 20 people was approximately 0.18, and the likelihood of infecting more than 1000 was 0.27 (section 3.5). apart from deriving analytic expression for the spreading and control of an epidemic, the main results of this study, when applied to the sars epidemic in hong kong in 2003, is that our data is consistent with the observation that the epidemic that occurred was largely preventable. the primary factor for the severity of the outbreak was poor infection control in the hospital setting and the delayed introduction of quarantine and community isolation practices. this is consistent with various discussions presented elsewhere. however, we note that nosocomial transmission was considered only by supposing (admittedly erroneously) that the time between becoming symptomatic (and infectious) and hospitalisation is constant. nosocomial transmission is simulated by changing the expected duration between becoming symptomatic (i) and becoming removed (r). although this is perhaps unconventional from an epidemiological viewpoint, it is probably the best that we can do, as the only data that we have to work from is the date of hospital admission. this conclusion is in contrast with work done by pastor-satorras and colleagues [20, 21] with scale-free sis type [7] disease models. in that case, they found that the disease would almost always persist and that random immunisation was ineffective [21] . the model presented here emphasised the small-world transmission dynamics created by providing a small number of highly connected nodes. we model the inter-connection between nodes with one-directional links (rather than the bi-directional links we would expect for social contacts) because this makes the network much easier to construct, without sacrificing any realism. this model could easily be extended to exhibit scale-free characteristics, by simply altering the distribution of non-local links (to follow a power-law distribution). doing so would produce simulations with a larger number of highly connected individuals, and therefore we could simulate the largest sses in the data. the results presented in this paper show small (less than 100 individuals) sses; extension to the power-law distribution would provide sses with a larger number of secondary infections. we should note that it is very difficult to reliably and accurately fit even a moderate number of parameters to a stochastic model from such limited data. especially when the model, for the same parameter values, can exhibit a wide variety of behaviour. to overcome this, we (a) make our model so simple that the number of parameters is very few (certainly comparable in number to ordinary sir), and (b) only "fit" the model with typical parameter values and test that, for these parameter values, the observed data is typical. certainly, we cannot exclude the (quite likely) probability that other parameter values also produce behaviour of which the observed data is typical. therefore, in this paper we only draw conclusions based on our observations of parameters that produce behaviours that are either typical or (more importantly) atypical of the observed data. although we have observed that our model exhibits more realistic dynamics than sir models, it is only a model. and, like the sir model, our model is a compromise between complexity and realism. we intend to address this problem in the future by applying monte carlo markov chain models [22] to this sparse data [23] . even our choice of a discrete time model is open to debate. the choice, with a time interval chosen as one day, was motivated by the data and what was more intuitive to us. we have conducted calculations with both longer and shorter interinterval time scales and find that the results are invariant under a suitable change in time scale (i.e. we get equivalent results by using a shorter time step). moreover, recent epidemiological case studies have found that, overall, in hong kong 8% of individuals sharing a flat with a sars patient contracted sars [24] . given an average infectious period of four days (prior to hospitalisation), this implies that the daily probability of transmission is 0.02. this is approximately consistent with the values of p 1 used in this study, and therefore provides further support of our results. conversely, analysis of the sse at the prince of wales hospital found that, for a group of medical students, the probability of direct contact with the index patient leading to sars infection was 10 27 [5] . as this study dealt with a single meeting, this implies a daily infection probability of approximately 0.371: significantly higher than p 2 in our simulations. hence, although we have concluded that sses may occur without individuals necessarily being highly infectious, epidemiological evidence suggests that, in some cases, this may still be the case. finally, we note that, although the methods presented here are applied only to the sars outbreak in hong kong in 2003, these methods are not limited to this situation. apart from repeating, or modifying, this analysis for different infectious diseases (such as hiv aids), we imagine that these techniques could be useful in the theoretical study of quarantine and isolation practices, as well as disease transmission among isolated communities. quarantine can be effectively modelled as a limitation of long range transmission. one can easily model change in quarantine by varying the parameter µ (or alternatively, but not equivalently, p 2 ). this should provide a new, simpler approach to the study of quarantine to supplement compartmental models such as those described in [25] . world health organisation, consensus document on the epidemiology of sars report of the severe acute respiratory syndrome expert committee transmission dynamics of the etiological agent of sars in hong kong: impact of public health interventions cluster of sars among medical students exposed to single patient epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in hong kong mathematical biology modeling infection transmission more realistic models of sexually transmitted disease transmission dynamics: sexual partnership networks, pair models and moment closure a versatile ode approximation to a network model for the spread of sexually transmitted diseases likelihood-based inference for stochastic models of sexual network formation, theor poisson approximation for epidemics with two levels of mixing forecast and control of epidemics in a globalized world six degrees: the science of a connected age collective dynamics of 'small-world' networks small world and scale free model for transmission of sars dimensions of superspreading on-line encyclopedia of integer sequences, online mathematical epidemiology of infectious diseases epidemic spreading in scale-free networks epidemic dynamics and endemic states in complex networks bayesian inference for partially observed stochastic epidemics stochastic modelling of ecological processes using hybrid gibbs samplers probable secondary infections in households of sars patients in hong kong simulating the effect of quarantine on the spread of the 1918-19 flu in central canada this work is supported by funding from the health, welfare and food bureau of the government of the hong kong special administrative region under the research fund for control of infectious diseases (rfcid). dw thanks the scottish executive environment and rural affairs department (seerad) for support. key: cord-034317-bhzctz87 authors: ngan, olivia miu yung; sim, joong hiong title: evolution of bioethics education in the medical programme: a tale of two medical schools date: 2020-10-27 journal: international journal of ethics education doi: 10.1007/s40889-020-00112-0 sha: doc_id: 34317 cord_uid: bhzctz87 bioethics education in the anglo-european context developed since 1970 and was incorporated into the undergraduate and postgraduate education, residency training, and continuous education. in the asia-pacific region, bioethics education is less structured and often dependent on contextual constraints. this paper provides a cross-sectional analysis, describing institutional experiences in developing bioethics curriculum at two medical schools in malaysia and hong kong. the medical programmes of the two institutions are distinctive in terms curriculum framework, teaching approach, and topic selection, and common challenges include implementation of bioethics courses, students’ resistance to bioethics, and limited teaching capacity, emerged as they evolve. the reported experiences revealed that there is room for improvement regarding how medical schools integrate bioethics education in regions where curriculum development remains at an early stage. at least, a bioethics education requires both top-down support from the faculty to improve teaching and educational quality, as well as from the bottom-up approach to empower students to raise awareness and concerns toward bioethics, and helps students developing reasoning through challenging issues. moral conduct in the clinical practice demonstrated through attitudes and behaviours is a transcendental element in medical education. entering medical school as students and later becoming clinicians involves a transformative process emphasising knowledge competencies, codes of practice compliance, and moral development (holden et al. 2015) . clinical knowledge acquisition has been the core in the medical education and establishment of virtues values through bioethics training have been underexplored in medical education. bioethics in the anglo-european context has developed since 1970 and has been incorporated into the undergraduate and postgraduate medical curriculum, residency training, and continuous professional education. in the asia-pacific region, bioethics education did not gain attention until the 1990s, and teaching deliveries remained inconsistent and less structured depending on contextual factors (miyasaka et al. 1999 ). one of the common barriers in the implementation of a curriculum in a resource-constrained context is a lack of teaching capacity (ten have 2014) . teaching bioethics requires expertise both in ethics and medicine. nonetheless, many teachers who are involved in bioethics curriculum in medical programmes were either philosophers, ethicists, or scientists with limited experience in medicine, or clinicians with inadequate formal training in ethics (ekmekci 2016; sim et al. 2019) . universities have a limited capacity to provide professional training of ethics and moral philosophy to sustain teaching quality. another common challenge is limited curriculum time to include ethics in the packed medical teaching timetable (ravindran 2008) . successful curriculum development implementation requires continuous and multifaceted consideration. there is a four-stage framework describing the action plan for progressive changes in the curriculum development, specific to bioethics curriculum in medical education over time, in terms of the implementation, content, teaching capacity, and instruction method (sherer et al. 2017) . in stage 1, there is no bioethics course in the institution. in stage 2, bioethics is taught from a philosophy course with a limited clinical perspective, emphasising on theories and knowledge acquisition. the capacity in supporting teaching is little and didactic lecture is the primary teaching delivery. in stage 3, bioethics is taught as an independent course, covering ethical issues arise from clinical practice, communication skills, and empathy. in addition to didactic teaching, other teaching methods, including small-group discussion and research project, are adopted to encourage intellectual exchange. in stage 4, the bioethics curriculum is taught by a multidisciplinary faculty team, including physicians, philosophers, and attorneys. the framework is a good indicator, particularly for developing countries, in determining the current status of bioethics education at medical schools. bioethics is taught in almost all medical schools in malaysia (sim et al. 2019 ) and hong kong (becker 2005) , and the teaching framework and deliveries vary to a great extent depending on the contextual factors. this paper provides a narration describing institutional experiences in developing bioethics curriculum at two medical schools the university of malaya and the chinese university of hong kong. malaya gained independence from british colonial rule in 1957. in 1963, malaysia, comprising the peninsula (west) and sabah and sarawak (east) was formed. the country is run based on parliamentary democracy. the legal system incorporates civil law, derived from british elements, and aspects of syariah laws for muslims. malaysia, with a population of 32.7 million, is a prime example of a plural society. the largest ethnic groups in malaysia are the malays (62%), chinese (21%), indians (6%), and others (1%) (department of information 2016). in sabah and sarawak, there is a myriad of indigenous ethnic groups with their own unique culture and heritage. due to the multi-racial characteristic of the population, it also has varieties of culture, religion, social norms and values. all these cultures have influenced each other, creating a genuinely diversified malaysian culture. the malaysian medical council (mmc) operates under the medical act of 1971 and regulates the registration and practice of medical practitioners (malaysian medical council 2020). over the years the mmc has undertaken the role of granting recognition to other medical schools in the country and overseas and added the name of these schools to the existing register of recognised medical degrees in the second schedule of the act. it is recommended that the mmc establishes an active functional 'education committee' and that the role of mmc in medical education should be clearly and explicitly stated in the act. currently, there are 32 malaysian medical schools, including 11 public and 21 private institutions (wong & kadir 2017) . the university of malaya (um) is the oldest public tertiary institution in malaysia, providing a five-year undergraduate medical programme -bachelor of medicine and bachelor of surgery (mbbs). at present, um adopts a system-based and problembased approach that integrates the teaching around the major body system, covering both basic scientific foundations and clinical reasoning skills development. before the medical curriculum reform took place in 2013, the teaching and assessment focused on the acquisition of medical knowledge and clinical skills, and the humane aspect of medicine was largely neglected. the course content is divided into three main components that run vertically through the course, namely: (i) the scientific basis of medicine, (ii) the doctor, patient, health and society, and (iii) personal and professional development. the scientific basis of medicine component includes the study of the normal human body and its function (anatomy, biochemistry, physiology); the body's reaction to injury (medical microbiology, pathology, parasitology pharmacology) and practice-based clinical medicine (anaesthesiology, biomedical imaging, emergency medicine, internal medicine, obstetrics and gynaecology, orthopaedic surgery, opthalmology, otorhinolaryngology, paediatrics, primary care medicine, psychological medicine, social and preventive medicine surgery). the doctor, patient, health and society (dphss) module includes the study of preventive, promotive, environmental and occupational health in the community; medical statistics, epidemiology, two field projects (community residency program, crp; organisation and management of health services, omhs); community family case studies, cfcs and family health. the personal and professional development (ppd) module includes improvement of learning, analytical, critical thinking and communication skills, nursing skills, medical ethics, research methodology and exposure to optional fields of interest via elective programs. under the past curriculum, bioethics was appended under personal, and professional development theme and lecture was the primary mode of delivery. there was no formal assessment on the subject. bioethics was not a popular subject among medical students. this was reflected by poor attendance, in particular, among pre-clinical students. some faculty members also do not consider bioethics a 'real' topic to be taught. at that time, the development of bioethics education was slow and insignificant. starting from 2013, the medical education and research development unit (merdu) has been actively involved in the curriculum reform and is now responsible for overseeing the bioethics curriculum. the current medical programme comprises of four themes, namely basic and clinical sciences, patient and doctor, population medicine, and personal and professional development. compared with the past curriculum, the most significant change in the revised curriculum is that personal and personal development module has been upgraded to a theme. while only ethics and professionalism were emphasised previously, bioethics, professionalism, humanities, and health law are given emphasis in the revised curriculum. this is to ensure that students not only grow professionally into good doctors but also receive a holistic experience in humanities other than science teaching in the medical curriculum. a unique feature is the 'language in medicine' component, which provides an early introduction to the humanities in medicine (sim et al. 2017) . students learn about icons in medicine, historical events in medicine, death and dying, end-oflife issues, and organ transplantation. (figure 1 ). today, bioethics is not taught as an independent course or a stand-alone course but as part of an integrated curriculum. moral theories and related application are oriented vertically and horizontally along with relevant clinical topics. for example, core topics such as informed consent and confidentiality are introduced in year 1 and revisited throughout the programme (vertical integration). other contentspecific topics such as ethical issues in human fertility are embedded into relevant learning block such as endocrine and reproductive health block in year 2 (horizontal integration) and revisit in later years during clinical postings such as obstetrics and gynaecology (vertical integration). in terms of content, a wide range of topics is being covered. topics more commonly taught in pre-clinical years include principles of bioethics, history of medicine, origins and philosophy in ethics, and medical humanities. it is believed that these topics need an early introduction to help lay the foundation for bioethics education. some cases, such as the refusal of treatment, reproductive issues, paediatrics and neonatal issues, are very clinical and could be addressed at a later stage, e.g. during clinical postings. however, certain topics need to be emphasised throughout the medical programme. some examples are informed consent, patient-doctor relationship, privacy and confidentiality, health law, truth-telling, cultural issues and diversity awareness, religious and spiritual issues, conflicts of interest. these topics aim to prepare medical students for work readiness in the healthcare setting of a plural society like malaysia. bioethics was not a popular subject among medical students, in particular, among pre-clinical students. some faculty members also do not consider bioethics a 'real' topic to be taught. before the medical curriculum reform, the development of bioethics education was slow and insignificant. nonetheless, since embarking on the change via curriculum transformation in our undergraduate medical programme at the beginning of 2013, our medical school has taken a giant step forward. murals related to bioethics on the walls of faculty buildings (figure 2) , initiated by faculty members and completed by medical students, is testimony there is increased awareness and acceptance of the importance of bioethics education among faculty members and students. local setting hong kong, now a territory of china, was a former british colony from 1841 to 1997 and the british common law system continued after 1997. british influence on the local medical practice and law also endures after the sovereignty handover to china. the current population of hong kong is about 7.5 million composed of chinese (92%). among the non-chinese ethnic groups, the majority are filipino (4%), followed by indonesia (2%), caucasian (1%), and others (3%) (the census and statistics department, 2017). compared with malaysia, hong kong is mostly a homogenous society. the medical council of hong kong is established under the medical registration ordinance handling the registration, professional conduct and discipline of medical practitioners in hong kong. the council also review the standard and structure of undergraduate medical education and training in the accreditation processes. in 2017, the council updated the document "hong kong doctors", listing a set of essential attributes and skills in addressing the medical dilemmas and moral difficulties among local medical practitioners (the medical council of hong kong 2017). the chinese university of hong kong (cuhk) is one of the two local universities, providing a six-year undergraduate medical degree programme -bachelor of medicine and bachelor of surgery (mbchb). it offers comprehensive longitudinal doctoring curriculum to train physicians. at present, cuhk adopts conventional, studentcentred and subject-based curricula offered by the preclinical-clinical division. overview of the current medical curriculum the first three years of the mbchb curriculum encourage breadth and depth learning, offering pre-clinical studies focusing on interdisciplinary education in the field of humanities, social science, natural science. in addition to courses teaching fundamental biomedical courses relevant to medicine (e.g. public health, anatomy, physiology), students are required to courses humanities and language. before transiting to the clinical year, a six-week bridging course is in place to equip student pathology and clinical anatomy and clinical communications skills. the latter three years of studies focus on learning advanced biology and clinical medicine subjects, such as anatomical and chemical pathology, anaesthesia and intensive care, diagnostic imaging, clinical microbiology, medicine and surgery. students receive clinical exposure through a rich mixture of bedside teaching, simulation training, and community or laboratory research opportunities. courses for communication skills and professionalism are introduced throughout the entire six-year programme. the overarching objective of the medical curriculum is to provide an allrounded training of science and humanities (figure 3 ). before the structured bioethics teaching rolled out, ethics was not yet implemented vertically and horizontally that sporadic ethics-related teaching took place on an ad hoc basis in the clinical years only. in 2011, a workshop "integrated professionalism teaching session" was introduced for final year medical students as part of the induction towards independent clinical practice (joynt et al. 2018 ). it is a 5-h session comprises of lectures, small group discussions, and group presentations. the teaching topics broadly include the principles guiding professionalism, medical regulations and government ordinances. starting from 2013, the quarterly clinical ethics grand round was also introduced in parallel in discussions about professional misbehaviours or ethical dilemmas in fig. 3 coursework during the six-year mbchb curriculum at the chinese university of hong kong healthcare and life science. during the symposium, students and staff members are required to vote using a green-red card that encourages active and interactive participation. in this 2-h event, students identify key ethical issues that arise in the context of the case, discuss possible conflicting principles, and provide reasonable resolutions based on the four principles approach that underpins much of our teaching of ethics. with this framework, the teaching of bioethics in the medical schools was the focus in the clinical years only. the acquaintance of ethics knowledge in the pre-clinical year were less emphasised. starting from the mid-2015, the new bioethics curriculum is integrated into the curriculum, covering a wide range of ethical issues in biomedical sciences, clinical practice, public health, law, and policy. the teaching goal of bioethics education along three dimensions encompasses acquiring cognitive knowledge and behavioural skills and encouraging positive character development. besides, teaching modules are designed to raise ethical sensitivity and develop critical thinking skills while encouraging robust communication and interpersonal skills. in the clinical years, students can then link the ethical theory, knowledge, and examples taught in the preceding years for an application to the clinical context. table 1 summarises the major themes of the curriculum. the topic-oriented approach in the pre-clinical year entails a teaching goal to (1) observe inter-dependence between medicines and ethics, (2) acquire bioethics knowledge and language, (3) recognise vital ethical issues in medical practice, and (4) apply reasoning skills when present in a dilemma. in the clinical years, students can then link the ethical theory, knowledge, and examples taught in the preceding years for an application to the clinical context. the section discusses barriers in the implementation of bioethics teaching from our experience, corroborating with literature. students' resistance to bioethics learning is a source of challenge. students, in general, believed that ethics is a 'soft' or 'fluffy' subject that lacks scientific rigour that could be reasoned based on common sensesocial and cultural normsthat does not require formal training (leo & eagen 2008) . malaysian and hong kong medical students, similarly, also regarded learning of ethics and medical humanities are of lower priority and prefer to spend more time learning clinical knowledge. ethics in medical education is sometimes regarded as a diversion from the core study of medical knowledge. at worst, ethics may be viewed as a tedious repetition of the obvious with an emphasis on procedural requirements for informed consent, protection of patient confidentiality, etc. less acknowledged is the unique role of bioethics in the development of core clinical skills such as critical reasoning, familial conflict management, navigation of discourse among professional peers, and understanding healthcare policy. the contemporary bioethics stems moral philosophy applied in research and healthcare contexts and the field has grown ever-present in medical curricula around the globe in an effort to produce doctors capable of navigating complex patient circumstances. however, given that most medical students gravitate towards hard science with its clear and testable answers, the theoretical-and humanities-based roots of bioethics reduce its importance in the eyes of pupils. another speculative reason is that students were uncertain about the need for bioethics in pre-clinical years, although they observe the vital role of bioethics for developing the professional identity. young medical students often neglected the importance of developing moral awareness for a future career during the time of learning 'skills' in early university years. interestingly, practising physicians observed the importance of bioethics when recognising their identity as primary caregivers as opposed to students (chan et al. 2011) . as young medical student progress to advanced years, they became interested in learning topics related to contemporary ethical issues and moral dilemmas that physicians faced in daily practice (aldughaither et al. 2012 ). the discrepant perceived view of bioethics education between young medical students and experienced practising doctors point out the need of a formal orientation about the instrumentality of bioethics training in early medical education years among students whose curricula in high school were predominately focused on mathematics, engineering and natural sciences. in other words, the influence of bioethics on professional identity construction has been largely ignored in reality. it is imperative to connect students with bioethics teaching such that relevance to the future career as a doctor is obvious rather than dismissed. there are studies in the united states, netherland, indonesia, or nigeria, reported that medical students witnessed unethical decision, unprofessional behaviour, inappropriate conduct by superiors or co-workers in early clerkship (muhaimin et al. 2019; okoye & nwachukwu 2017; seiden et al. 2006; yamey & roach 2001) . they, however, were uncertain about the resolution in preventing ethical lapses. importantly, implementing ethics training in the clinical years may be late, since students learn by being told what to do by senior doctors with limited opportunity to think and reflect critically (hren et al. 2011 ). bioethics training is not a one-time, but a longitudinal and reflective learning process in the career trajectory shaping a professional identity and cultivate a culture of humanism (fernandes 2011) . it needs to be implemented throughout medical practice years to help reconstruct correct values in medicine in the shifting role from 'layman or students' to 'physician' identity. when combined with traditional scientific learning, bioethics forms a critical component of comprehensive medical education, which has developed as the new international standard. to achieve parity with global education norms, bioethics teaching must adapt both to evolving learning styles and geographic realities. in the asia-pacific context, the euro-american dominance of teaching materials causes students to dismiss bioethics curricula as impractical. a lack of local contexts in the curriculum affects the long-term effect of learning. the framework should consider the deliberation of not only locally specific systems and events but also cultural belief systems and philosophical foundation of the society. modern bioethics which is developed in western philosophies might not adequately provide tools to address ethical complexity in clinical practices of ethical and religious diversity (chattopadhyay et al. 2013; fuscaldo et al. 2010) . the contested notion of cultural relativism in pluralistic societies as a response to the conventional belief of universality of morals needs to be discussed in bioethics education (sokol 2016) . the topic of public health is a great example illustrating the need to respect cultural difference from our experience. for instance, in the us context, the use of restrictive measures (i.e. quarantine) in response to infectious disease epidemics was disputable, as it is perceived to violate individual freedom for population good. this contrasts with hong kong, where citizens experienced the sars epidemic in 2003, and using quarantine to monitor individuals for the 'greater good' was found reasonable from the local perspective (blendon et al. 2006) . in malaysia, the recent examples of covid-19 challenge the right in a religious gathering while implementing individual movement's restriction (yezli & khan 2020) . our recent transcultural experience introducing local topics cases has resulted in more lively discussions, with students more willing to express their observations and opinions on topics of bioethical relevance. for example, the discussion of imposing a mandatory influenza vaccination program for healthcare workers is somewhat less challenged in the us (babcock et al. 2010) . still, it remains unsettled in malaysia and hong kong, which results in a lively debate in the class (hudu et al. 2016; so et al. 2016) . these examples demonstrated that there is no unified approach to ethical problems, and responses are the result of a complex mix of moral and value-related issues turner 2005) . a study also discussed that incorporating cases that are relevant to the local medical systems helps cultivate bioethical responsiveness among the students . our learning experience is that placing local contexts as equally as western bioethics enhance the quality of a participatory bioethics teaching in our institutions and it should be done clearly at the design phase of the curriculum. one of the common challenges in the implementation of a bioethics curriculum in a resource-constrained context is a lack of teaching capacity (sim et al. 2019; ten have 2014) . teaching bioethics requires expertise both in ethics and medicine, and universities, nonetheless, have a limited ability to provide professional training of ethics and moral philosophy to sustain teaching quality. in the university of malaya, there is only a retired o&g specialist with a law degree, who is well-qualified to teach bioethics. other faculty members involved in bioethics teaching are mainly clinicians with some exposure to ethical issues in clinical practice but not trained specially in bioethics. in other malaysian medical schools, bioethics teaching is majorly lead by healthcare professionals or a multidisciplinary team of scientists, lawyers, and ethicists (sim et al. 2019 , bilgin et al. 2018 . in hong kong, many teachers who are involved in bioethics curriculum in medical programmes were either philosophers, ethicists, or scientists with limited experience in medicine, or clinicians with some training in bioethics (rothchild & holmquist 2019) . to address limited teaching capacity limitation, the faculty development team shall progressively organise workshops to provide training to faulty with little ethics background on areas such as how to integrate bioethics teaching into clinical postings. placing local contexts as equally as western bioethics will enhance the quality of a participatory bioethics teaching in asia, and it should be done clearly at the design phase of the curriculum. to overcome limited teaching resources, the success of the collaborative learning activities depended upon the training of local faculty who were responsible for leading the teaching. indeed, the concept of "training of trainers (tot)" has been widely implemented globally in the fields of health education by international institutions (e.g., un agencies) and major universities in developed countries in resource-limited settings, mostly developing countries (ewert et al. 2011; world health organisation, 2006) . unesco offers "ethics teachers' training courses (ettc)" in developing countries as part of its bioethics professional capacity building programme (ten have 2019; langlois 2014) . while tot can be effective to introduce the change in the place of intervention by teaching individuals, providing basic resources and implementing an initiative programme, another level of local resources is necessary to achieve sustainability (mormina & pinder 2018) . thus, the long-term effect of the bioethics curriculum requires the local commitment and leadership as resource-limited academic settings need more collaborative, participatory learning through interaction with teachers and peers in class (avci 2017 ). this paper described two evolving experiences in implementing bioethics teaching within existing institutional capacity. both medical schools are unique and very different in terms of the curriculum, and common challenges include curriculum design, students' resistance to bioethics teaching, and limited teaching capacity, were observed as the curriculum evolve. the reported experiences revealed that there is room for improvement regarding how medical schools integrate bioethics education. from a top-down approach, the faculty shall proactively improve teaching and educational quality by hosting continuous education sessions. from a bottom-up approach, it is equally crucially to empower students to raise awareness and concerns toward bioethics and helps students developing reasoning through challenging issues. student perspectives on a course on medical ethics in saudi arabia learning from experiences to determine quality in ethics education mandatory influenza vaccination of health care workers: translating policy to practice bioethics with chinese characteristics: the development of bioethics in hong kong what does it mean for a case to be "local"? the importance of local relevance 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centres and primary health centre medical education in malaysia: quality versus quantity witnessing unethical conduct: the effects covid-19 social distancing in the kingdom of saudi arabia: bold measures in the face of political, economic, social and religious challenges publisher's note springer nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations authors' contributions jhs conceived the study. omyn and jhs drafted the manuscript. omyn made substantial edits on the writing. omyn and jhs approved the final manuscript.data availability not applicable. competing interests all authors declare no conflict of interests.code availability not applicable. key: cord-274306-cxvnv8dy authors: chastel, c. title: émergence de virus nouveaux en asie : les changements climatiques sont-ils en cause ? date: 2004-11-30 journal: médecine et maladies infectieuses doi: 10.1016/j.medmal.2004.07.027 sha: doc_id: 274306 cord_uid: cxvnv8dy résumé l’afrique tropicale n’est pas la seule région du monde où des virus dangereux pour l’homme aient récemment émergé. l’asie, en particulier la chine et le sud-est asiatique, a également connu l’émergence de viroses humaines graves, telles que la dengue hémorragique (les philippines, 1954) ou plusieurs pandémies grippales, la grippe asiatique (n2h2) en 1957, la grippe de hong-kong (h3n2) en 1968, et la grippe russe (h1n1) en 1977. mais, c’est surtout au cours des dix dernières années que les émergences virales s’y sont multipliées avec l’apparition de la fièvre hémorragique à virus alkhurma en arabie saoudite (1995), de la grippe aviaire h5n1 à hong-kong, en 1997, de l’encéphalite à virus nipah en malaisie, en 1998, et surtout du sras, en chine du sud en 2002. les facteurs climatiques n’ont probablement joué qu’un rôle réduit dans le succès émergentiel de ces viroses, favorisé plutôt par des facteurs humains : le développement d’élevages industriels d’animaux de basse cour augmentant les risques d’épizooties, les habitudes alimentaires, les pressions économiques et démographiques, les négligences dans la surveillance épidémiologique et la déclaration des premiers cas. abstract tropical africa is not the only area where deadly viruses have recently emerged. in south-east asia severe epidemics of dengue hemorrhagic fever started in 1954 and flu pandemics have originated from china such as the asian flu (h2n2) in 1957, the hong-kong flu (h3n2) in 1968, and the russian flu (h1n1) in 1977. however, it is especially during the last ten years that very dangerous viruses for mankind have repeatedly developed in asia, with the occurrence of alkhurma hemorrhagic fever in saudi arabia (1995), avian flu (h5n1) in hong-kong (1997), nipah virus encephalitis in malaysia (1998,) and, above all, the sars pandemic fever from southern china (2002). the evolution of these viral diseases was probably not directly affected by climate change. in fact, their emergential success may be better explained by the development of large industry poultry flocks increasing the risks of epizootics, dietary habits, economic and demographic constraints, and negligence in the surveillance and reporting of the first cases. au cours des cinquante dernières années, la plupart des virus « nouveaux » qui ont émergé provenaient d'afrique subsaharienne : fièvres hémorragiques africaines (marburg, lassa, ebola), sida, monkeypox, donnant l'impression que le continent africain était le réservoir de virus essentiel de la planète. mais d'autres virus nouveaux ont également émergé en asie, dont ceux de plusieurs pandémies grippales, de la dengue hémorragique et, plus récemment, le virus h5n1 de la grippe aviaire, le virus nipah et le coronavirus du sras. quant aux virus du sida, ils continuent de progresser chaque jour en asie, notamment dans les pays les plus peuplés, l'inde, la chine et l'indonésie. le but de cette revue est non seulement de dresser le bilan des dernières émergences virales sur ce continent, mais aussi d'apprécier la part relative des facteurs humains et des facteurs environnementaux dans l'émergence et la réussite émergentielle [1] de ces virus. pendant cette période, les techniques virologiques étaient encore sommaires. elles ont cependant permis l'isolement de certains des tous premiers virus reconnus pathogènes chez l'homme. ils sont répertoriés dans le tableau 1. ce sont tous des agents de zoonoses rurales entraînant chez l'homme une pathologie sévère et une mortalité pouvant dépasser le tiers des malades. parmi les survivants des encéphalites, les séquelles neurologiques sont fréquentes et graves. si leur nature virale a été assez rapidement prouvée pour l'encéphalite japonaise (1934) , pour l'encéphalite vernoestivale russe (1937) et pour la fièvre hémorragique de crimée (1945) , il a fallu attendre la fin des années 1970 pour que le virus de la fièvre hémorragique de corée mandchourie, maladie connue depuis les années 1930 sur les deux rives du fleuve amour, soit enfin isolé et caractérisé [2] . il existe un bon vaccin contre l'encéphalite japonaise, le vaccin biken inactivé, produit sous licence par pasteur-mérieux. il convient pour la protection des personnes vivant ou se déplaçant en zone d'endémie (cf. géographie, tableau 1), pour leur travail ou leurs loisirs. pour se protéger éventuellement de l'encéphalite vernoestivale russe, on dispose du vaccin inactivé fsme -immuno ® inject. il a été mis au point en autriche contre le virus de l'encéphalite européenne à tiques. cette dernière virose est transmise par la tique ixodes ricinus et son agent est un variant ouesteuropéen du virus russe. en france, ces vaccins sont accessibles dans les centres de vaccination contre la fièvre jaune. les progrès de la virologie ont permis de beaucoup améliorer nos connaissances sur les virus asiatiques. ainsi, la dengue hémorragique est apparue en 1954 aux philippines et elle a envahit ensuite tout le sud-est asiatique [3] . plus qu'une émergence virale, c'était celle d'une nouvelle forme clinique, plus grave, parfois mortelle, de la « dengue classique » habituellement bénigne [4] . contrairement aux fièvres hémorragiques précédemment décrites en asie (cf. 2.1), il s'agissait d'une maladie urbaine, frappant surtout de jeunes enfants autochtones et les vecteurs n'étaient pas des tiques mais des moustiques, aedes aegypti et aedes albopictus [4] . plus tard, de jeunes adultes furent également atteints. pour expliquer son apparition, on a invoqué des facteurs essentiellement anthropiques. le développement monstrueux des grandes métropoles asiatiques, au cours des années 1950-1960, a provoqué la prolifération des vecteurs, surtout d'a. aegypti, en même temps qu'une démographie galopante assurait un volant constamment renouvelé de jeunes enfants réceptifs. la circulation accélérée des quatre types sérologiques du virus de la dengue a provoqué une sensibilisation immunologique séquentielle de ces enfants, par ces flavivirus [5] . il en est résulté une cascade d'événements immunopathologiques conduisant à la fragilité capillaire, aux hémorragies et au choc hypovolémique, mortel dans 10 à 50 % des cas. on ne dispose toujours d'aucun vaccin efficace contre la dengue qui est devenue, chez l'enfant, l'un des principaux problèmes de santé publique, en asie du sud-est. par ailleurs, deux autres fièvres hémorragiques virales, de distribution géographique plus restreinte et de moindre importance en santé publique ont été décrites. en 1957, la fièvre de la forêt de kyasanur a été identifiée en inde, dans l'état de karnātaka, et la fièvre hémorragique d'omsk l'a été en 1959, en sibérie occidentale. toutes deux sont transmises par des tiques et leurs agents étiologiques sont des flavivirus [6] . le tableau clinique, fait d'hémorragies et de troubles neurologiques, est voisin dans les deux maladies et la mortalité ne dépasse pas 5 %. mais le principal événement virologique fut l'apparition de pandémies grippales a : en 1957, la « grippe asiatique » (h2n2) et en 1968, la « grippe de hong-kong » (h3n2). elles ont permis de dégager une doctrine permettant d'expliquer l'apparition en chine du sud de virus grippaux entièrement nouveaux, par réassortiment génétique [7] . l'existence dans de nombreuses régions rurales de ce pays, d'élevages de canards et de porcs, en étroite promiscuité avec la population, favorise le phénomène. le réservoir principal des virus grip l'asie a subi, alors, comme le reste du monde, l'impact de plusieurs pandémies virales. ainsi, des enterovirus nouveaux ont, en 1969-1973, envahi la planète, provoquant une pathologie jusque là inconnue : la conjonctivite hémorragique épidémique. cette virose oculaire extrêmement contagieuse provoque du larmoiement, des douleurs oculaires violentes, des hémorragies sous-conjonctivales et, éventuellement, une kératite. apparue en afrique occidentale (1969), elle a ensuite gagné rapidement le reste de l'afrique, l'europe et l'ensemble de l'asie, tout particulièrement l'inde, le japon et singapour (1971) . deux virus différents en étaient responsables : un variant du coxsackievirus a24 et l'enterovirus 70 [8] . l'inde fut à nouveau touché en 1975. il n'existe ni traitement spécifique, ni vaccin. mais la pandémie la plus grave est, sans conteste, celle du sida, reconnu à partir de 1981. les virus responsables ont été rapidement isolés et caractérisés, le vih 1 en 1981 et le vih 2 en 1985. depuis, la maladie ne cesse de s'étendre dans le monde, l'asie constituant le deuxième foyer mondial, après celui de l'afrique subsaharienne. les pays les plus peuplés de la terre, l'inde (~4 millions de personnes infectées) et la chine (~840 000 infections) sont gravement atteints ainsi que tout le sud-est asiatique. fin 2003, la région asie-pacifique comptait 7,4 millions de sujets infectés [9] . l'asie est aussi une terre d'élection des hépatites virales. les virus a et b y sont largement répandus et c'est à taiwan que fut confirmé, de façon indiscutable, le lien existant entre l'hépatite b et le cancer primitif du foie [10] . à la fin des années 1980, les progrès de la virologie moléculaire ont montré que les virus c et e étaient également très présents en asie [11, 12] . de plus, c'est en inde que la notion d'extrême gravité de l'hépatite e chez la femme enceinte (mortalité 20 %) a été établie [13] . enfin, en 1977, on a observé la réémergence du virus grippal a (h1n1), responsable de la « grippe russe ». le virus est apparu pratiquement simultanément en chine et en sibérie [14] . ces émergences se sont produites à un rythme accéléré et certaines ont été particulièrement spectaculaires. elle est provoquée par un flavivirus nouveau qui a émergé en 1995 chez des bouchers d'abattoir, à djedda, en arabie saoudite. proche du virus de la forêt de kyasanur (kfd), alk provoque comme ce dernier une fièvre hémorragique sévère ou, plus rarement, une encéphalite [15] . la source de la contamination est constituée par des moutons. actuellement, 24 cas ont été identifiés à djedda et à la mecque, avec une mortalité de 25 % [16] . le génome du virus a été entièrement séquencé confirmant ses parentés génétiques avec le virus kfd [16] . mais les virus kfd et alk occupent des niches écologiques totalement distinctes : une forêt humide dans le nord de l'inde, peuplée de singes et infestée de tiques pour kfd ; un environnement semi-désertique pour alk. outre le contact avec le sang de moutons infectés, la maladie pourrait être transmise par des tiques ou, encore, par la consommation de lait cru de chamelle. elle sévit en deux pics annuels : mai-juin et septembre-octobre [16] . aucun vaccin n'est disponible actuellement. lorsqu'en 1997, l'épidémie de grippe a (h5n1), d'origine aviaire, éclata à hong-kong, elle eut immédiatement un fort retentissement médiatique. ce pouvait être le début, tant redouté, d'une nouvelle pandémie grippale qui, telle celle de 1918-1919, pouvait faire des millions de morts [17, 18] . les choses avaient débuté à bas bruit. en mai 1997, un garçon de trois ans était mort d'une pneumonie grippale compliquée d'un syndrome de reye. la souche virale isolée à cette occasion était un virus grippal a non caractérisable par les méthodes courantes. c'était en réalité un virus grippal aviaire, de formule antigénique h5n1, jamais rencontré chez l'homme [19, 20] . fin 1997, 17 nouveaux cas survinrent à hong-kong entraînant cinq autres décès, ce qui portait la mortalité totale à 33 %, chiffre jamais atteint dans la grippe humaine. la plupart des malades avaient moins de 15 ans, mais il y avait d'autres sujets nettement plus âgés. depuis le printemps 1997, il y avait eu trois épizooties dans des élevages de poulets à hong-kong. elles étaient également dues au virus h5n1 [21] et les souches isolées de la volaille étaient identiques génétiquement à celles des cas humains. toutes les souches, humaines et animales, étaient d'un type purement aviaire. stupéfaction ! un virus grippal a aviaire avait franchi directement la « barrière d'espèce » humaine, sans réassortiment génétique préalable chez le porc. on extermina un million et demi de poulets fin 1997 et l'épidémie s'arrêta. il fut démontré que la transmission inter-humaine n'avait joué aucun rôle dans la propagation de l'épidémie, les malades s'étant tous probablement contaminés auprès de poulets infectés. le virus n'avait pas diffusé plus avant dans la population de hong-kong, justement du fait qu'il n'y avait pas eu de réassortiment avec les souches humaines. mais pourquoi le virus h5n1 de hong-kong avait-il entraîné des infections d'une telle gravité chez l'homme ? l'autopsie de deux patients décédés a montré des altérations diffuses, un syndrome hémophagocytaire, de la nécrose des hépatocytes et des tubules rénaux, avec une forte déplétion lymphocytaire. pendant la maladie, il y avait eu une hyperproduction des cytokines inf-c et il-6, et du récepteur soluble de il-2 [22] . quant aux souches virales elles-mêmes, elles présentaient un site polybasique de clivage de l'hémagglutinine, caractéristique des souches aviaires très virulentes [21] . [25] . ils avaient voyagé dans la province de fujian, dans le sud-est de la chine, les souches virales isolées de ces derniers malades étaient de type aviaire, mais différaient génétiquement de celles isolées en 1997 [25] . enfin en janvier 2004, h5n1 a réémergé chez l'homme au vietnam, au cambodge, au laos et en thaïlande, tandis que des élevages de poulets et de canards étaient infectés dans ces mêmes pays et en corée du sud, en chine, au pakistan et au japon. et le massacre de la volaille a repris de plus belle... un faucon pèlerin (falco peregrinus) a même été trouvé mort à hong-kong, infecté par h5n1. on redoute toujours, à l'occasion de ces réémergences multiples, un réassortiment génétique désastreux pour notre espèce. d'autant plus que la diversité génétique des souches de h5n1 circulant dans la région semble avoir beaucoup augmenté depuis 2001. c'est peut-être la conséquence des vaccinations réalisées dans les élevages de poulets, en chine, avec un vaccin insuffisamment immunogène. il aurait pu masquer la symptomatologie chez les poulets infectés, sans empêcher que ceux-ci diffusent l'infection autour d'eux (newscientist, 11 février 2004). pour le moment, il n'existe aucun vaccin à usage humain contre h5n1. ce virus a émergé brusquement en malaisie, en 1998, provoquant une grave épidémie d'encéphalite chez des éleveurs de porcs [26] . les états de negri sembilan, pérak et sélangor ont été les plus touchés : 245 cas humains ont été enregistrés entre septembre 1998 et avril 1999, entraînant la mort de 104 malades, soit 39,2 % [27] . c'était le prolongement humain d'une épizootie porcine qui avait tué 5 % des porcs atteints. on crut d'abord avoir affaire à une poussée d'encéphalite japonaise, mais les données épidémiologiques n'étaient pas en faveur d'une telle hypothèse, même s'il y eut probablement des infections mixtes. en fait, les malades étaient des hommes adultes, souvent vaccinés contre l'encéphalite japonaise et ayant eu des contacts professionnels avec des porcs malades [27, 28] . en mars 1999, un autre foyer épidémique apparut à singapour, touchant 11 travailleurs des abattoirs, infectés par des porcs importés de malaisie ; il n'y eut heureusement qu'un seul décès [27, 29] . l'étude anatomopathologique de 32 cas humains a révélé des lésions diffuses de capillarite nécrosante, notamment au niveau de l'encéphale [27, 28, 30] . le virus nipah, grâce à sa protéine v, peut inhiber l'action antivirale des inf-a et c, in vitro [31] . pour la seule fédération de malaisie, plus d'un million de porcs furent euthanasiés [28] , ce qui a représenté de lourdes pertes économiques pour ce pays, fort exportateur. deux militaires sur les 1638 engagés dans ce programme contractèrent une encéphalite tandis que six autres étaient infectés de façon inapparente, malgré le port de masques, de gants, de lunettes et de bottes [32] . le virus nipah est apparenté au virus hendra isolé précédemment en australie où il a tué des chevaux et des personnes en contact directe avec ces derniers [33] . ces virus appartiennent à un genre nouveau, henipavirus, de la sousfamille des paramyxovirinae. comme le virus hendra est associé à des chauves-souris on a, naturellement, recherché des traces d'activité du virus nipah chez les chiroptères du sud-est asiatique. effectivement, des anticorps neutralisant ce virus ont été décelés chez cinq espèces de chauves-souris de malaisie, tant frugivores (surtout des roussettes) qu'insectivores [34] , et chez des roussettes (pteropus lylei) proposées à la consommation dans des restaurants, au cambodge [35] . finalement, le virus nipah a été isolé des urines de la roussette pteropus hypomelanus, en malaisie [36] . ces chiroptères sont donc, très vraisemblablement les réservoirs du virus nipah dans la nature. depuis l'extermination des porcs infectés, on a plus signalé de cas d'encéphalite à virus nipah, mais il convient de rester vigilant car les roussettes et les porcs sont très nombreux dans tout le sud-est asiatique. heureusement, la ribavirine semble pouvoir réduire la mortalité chez l'homme [37] et un vaccin recombinant pasteur-mérieux est à l'étude [38] . c'est la première pandémie du xxi e siècle, apparue en chine méridionale, à la fin de 2002. elle a démontré à la fois la fragilité de nos systèmes de santé et l'intérêt évident d'une coopération scientifique internationale. le 15 mars 2003, l'oms a lancé une alerte mondiale concernant l'apparition à hong-kong, d'une épidémie inquiétante de « pneumonie atypique transmissible », baptisée sras peu après. cette maladie atteignait plus volontiers le personnel des services d'urgence et des sujets relativement âgés, mais pas exclusivement. l'évolution clinique était progressive et la mortalité se situait entre 3 et 10 %. ce n'était pas non plus de la grippe. l'épidémie a ensuite gagné hanoi, singapour, beijing, bangkok, toronto et vancouver, se manifestant dans une trentaine de pays. quelques cas furent rapportés en europe, dont sept en france, heureusement non mortels. le personnel des soins intensifs et les proches parents, ceux qui étaient en contact très étroit avec des malades, étaient les plus atteints. l'incubation durait de 48 heures à sept jours. en fait, dès la mi-novembre 2002, cette épidémie s'était manifestée en chine du sud, dans la province de guangdong, où elle avait tué plus de 300 personnes, sans que les autorités chinoises informent la communauté internationale. bien plus, elles retardèrent l'accès de la région aux experts de l'oms. le virus responsable fut rapidement isolé et caractérisé au point de vue biologique et génétique [39] . c'était un coronavirus entièrement nouveau, le sars-cov dédié au docteur carlo urbani, le représentant de l'oms à hanoï, mort dans les premiers du fait de son dévouement. ce virus différait complètement des coronavirus que l'on connaissait déjà chez l'homme et les animaux domestiques ou de compagnie [40] . la coopération de 11 laboratoires nationaux de virologie, coordonnés par l'o.m.s., a permis ce résultat spectaculaire qui aurait pu être encore plus rapide si les autorités politiques et sanitaires chinoises avaient preuve d'un peu plus de responsabilité [41] . ce succès ouvrait la voie à la mise au point de tests diagnostiques fiables, de vaccins, d'antiviraux et à la compréhension de la pathogénie du sras. contrairement à ce qui a pu être dit, les coronavirus ont une certaine résistance dans le milieu extérieur, en particuliers ceux qui infectent les porcs [42] . cela pourrait expliquer la facilité avec laquelle le sras a diffusé, à partir d'un seul cas-index, dans le « amoy gardens apartment block » de hong-kong, infectant 311 résidents. chez les malades (comme chez les animaux), le virus est présent non seulement dans les sécrétions nasales et pharyngées, mais également dans les selles (97 % par rt-pcr), et 73 % des patients sont diarrhéiques [43] . d'ailleurs, comment expliquer autrement que par une certaine résistance des virus, les infections de laboratoire rapportées fin 2003 à singapour et à taiwan. on a aussi suspecté les rats domestiques d'avoir propagé le sras dans le « amoy gardens » [44] . reste l'épineuse, mais essentielle question de l'origine du virus. l'hypothèse la plus vraisemblable est celle d'un réservoir de virus animal. l'attention des virologistes de hong-kong s'est rapidement portée sur la faune sauvage ou semisauvage, proposée à la vente sur les marchés du sud de la chine, afin de satisfaire les goûts culinaires des gastronomes locaux. on y trouve des pangolins, civettes, blaireaux, chauves-souris, singes, serpents, etc., dans une extraordinaire promiscuité avec l'homme. sur le marché de shenzhen, dans la province de guangdong qui fut l'épicentre de l'épidémie de 2002, ils ont isolé [45] un coronavirus très proche de celui du sras chez plusieurs civettes de l'himalaya (paguna larvata) et chez un chien viverrin (nyctereutes trocyonoides). au même endroit, un blaireau chinois (melogale moschata) fut trouvé porteur d'anticorps spécifiques. les souches virales isolées de ces animaux diffèrent de celles de l'homme atteint de sras par la présence, dans leur génome, de 29 nucléotides supplémentaires [45] . ce n'est probablement pas la consommation de leur viande qui assure la contamination humaine, car ces virus ne résistent pas à la cuisson. ce serait plutôt le stockage en cage, la vente, le dépeçage et la préparation en cuisine qui permettrait au virus de franchir la « barrière » de notre espèce. alors que de nouveaux cas de sras sont apparus en chine, début 2004, de plus en plus d'arguments virologiques et épidémiologiques désignent la civette de l'himalaya, sinon comme le réservoir primaire du virus, du moins comme le vecteur de l'infection, avec peut-être également les rats [46] et les chats domestiques, ces derniers ayant été trouvés infectés dans le « amoy gardens ». ces conclusions récentes ont valu à plus de 10 000 civettes d'élevage un pogrome très médiatisé. le sras n'a certainement pas fini de faire parler de lui. des vaccins sont à l'étude. la ribavirine semble avoir une certaine activité sur le virus. . face à l'émergence de nouvelles zoonoses virales, la notion de « barrière d'espèce » peut même s'avérer dangereuse, en conduisant les autorités sanitaires à sous-estimer les risques pour l'homme d'une maladie animale quelle qu'en soit la nature. on a encore en tête, l'émergence chez l'homme, en 1996, du nouveau variant de la maladie de creutzfelt-jakob, dont une soit disant barrière devait nous protéger. ensuite, il est de plus en plus évident que la chine et le sud-est asiatique représentent une formidable machine à faire émerger des virus dangereux pour notre espèce. par ailleurs, si l'on cherche à comprendre pourquoi les émergences virales récentes en asie ont eu des succès émer-gentiels variables, il faut faire appel à la biologie moléculaire des virus à arn. en 1997, à hong-kong, l'épidémie de grippe h5n1 s'est arrêtée après que les poulets responsables aient été tous exterminés. il n'y a pas eu d'extension interhumaine de la maladie car h5n1 n'a pas eu le temps ou l'opportunité, de se réassortir avec des souches du virus grippal a humaines. toutefois, il faut rester vigilant. les réémergences récentes de h5n1 au vietnam, en corée du sud, au cambodge, en chine, au japon et en indonésie risquent d'apporter à ce virus de nouvelles occasions de réassortiment génétique, d'où l'inquiétude justifiée de l'oms. le coronavirus du sras apparaît, à priori, le plus dangereux. il a bien réussi sa première émergence [40] , infectant plus de 8000 personnes, dans une trentaine de pays différents. il se transmet très bien d'un malade à son entourage immédiat, médical ou familial. si on applique au sras le concept du ro (« basis reproductive number »), c'est à dire la capacité moyenne à se transmettre, d'un individu infecté à un ou plusieurs sujets réceptifs d'une population non immune [47, 48] , le sras bénéficie d'un ro nettement supérieur à un, du moins au cours de certaines étapes de sa propagation planétaire. par comparaison, les infections à h5n1 ou nipah sont caractérisés par un ro voisin de zéro. enfin, si l'on cherche à estimer le poids des facteurs humains et des facteurs environnementaux tels que le réchauffement planétaire, dans le succès émergentiel de ces virus, il est clair que le principal responsable est l'homme lui-même. c'est lui qui a installé des élevages industriels, parfois monstrueux, de volailles (chine : 1,3 milliard de poulets pour la seule province de guangdong), de porcs (malaisie) ou de civettes (chine du sud), constituant autant de milieux artificiels favorables à l'éclosion d'épizooties. la mauvaise foi des autorités chinoises face aux problèmes du sras ou de h5n1, relève de la nature humaine. en revanche, les changements climatiques, le phénomène el niño [49] , dont la réalité ne peut être niée, représentent pour les virus examinés ici, peu de chose face aux comportements humains et aux habitudes culturelles, notamment alimentaires. les maladies virales, susceptibles d'être influencées par le réchauffement planétaire sont des infections à transmission vectorielle, faisant intervenir des tiques, des moustiques ou des rongeurs [50] . ce n'est le cas ni pour la grippe aviaire h5n1, ni pour l'encéphalite à virus nipah, ni pour le sras. les infections virales dont l'épidémiologie pourrait être modifiée par des changements climatiques, dans le sudest asiatique, sont plutôt l'encéphalite japonaise et la dengue, mais pour le moment rien n'a été publié dans ce sens. émergences virales chez l'homme et réussite émergentielle isolation of the etiologic agent of korean hemorrhagic fever mosquito-borne hemorrhagic fevers of south and south-east asia réflexions sur deux viroses d'actualité: la fièvre jaune et la dengue pathogenesis of dengue : challenges to molecular biology arbovirus transmis par des tiques et pathogènes pour l'homme ou pour les animaux 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of encephalitis in malaysia a morbillivirus that caused fatal disease in horses and humans nipah virus infection in bats (order chiroptera) in peninsular malaysia antibodies to nipah-like virus in bats isolation of nipah virus from malaysian island flying foxes treatment of acute nipah encephalitis with ribavirin nipah virus: vaccination and passive protection studies in a hamster model characterization of a novel coronavirus associated vith severe acute respiratory syndrome coronavirus : une émergence réussie china's missed chance enzymatic and acidic sensivity profiles of selected virulent and attenuated transmissible gastroenteritis viruses of swine clinical progression and viral load in a community outbreak of coronavirusassociated sars pneumonia: a prospective study possible role of an animal vector in the sars outbreak at amoy gardens isolation and characterization of viruses related to the coronavirus from animals in southern china sars virus infection of cats and ferrets epidemics-in-waiting the role of evolution in the emergence of infections diseases el niño and health incidence des changements climatiques planétaires sur les arboviroses transmises à l'homme par des moustiques et des tiques key: cord-273638-mmlwh87u authors: tso, ivy f.; park, sohee title: alarming levels of psychiatric symptoms and the role of loneliness during the covid-19 epidemic: a case study of hong kong date: 2020-08-23 journal: psychiatry res doi: 10.1016/j.psychres.2020.113423 sha: doc_id: 273638 cord_uid: mmlwh87u public health strategies to curb the spread of the coronavirus involve sheltering at home and social distancing are effective in reducing the transmission rate, but the unintended consequences of prolonged social isolation on mental health have not been investigated. we focused on hong kong for its very rapid and comprehensive response to the pandemic and strictly enacted social distancing protocols. thus, hong kong is a model case for the population-wide practice of effective social distancing and provides an opportunity to examine the impact of loneliness on mental health during the covid-19. we conducted an anonymous online survey of 432 residents in hong kong to examine psychological distress in the community. the results indicate a dire situation with respect to mental health. an astonishing 65.6% (95% c.i. = [60.6%, 70.4%]) of the respondents reported clinical levels of depression, anxiety, and/or stress. moreover, 22.5% (95% c.i. = [18.2%, 27.2%]) of the respondents were showing signs of psychosis risk. subjective feelings of loneliness, but not social network size, were associated with increased psychiatric symptoms. to mitigate the potential epidemic of mental illness in the near future, there is an urgent need to prepare clinicians, caregivers and stakeholders to focus on loneliness.  strict social distancing, implemented widely to curb the spread of covid-19, has the unintended consequences of prolonged social isolation and adverse impact on mental health.  we conducted an online survey to examine the impact of loneliness on mental health during covid-19 in hong kong, a model case for the population-wide practice of effective social distancing.  an astonishing 65.6% of the respondents reported clinical levels of depression, anxiety, and/or stress, and 22.5% were showing signs of psychosis risk.  loneliness, but not social network size, explained 12.0% to 29.2% of variance in these psychiatric symptoms.  to mitigate the potential epidemic of mental illness in the near future, there is an urgent need to prepare clinicians, caregivers and stakeholders to focus on loneliness. the corona virus disease 2019 , first started in china in december 2019, has spread across the globe within a few months and was declared a pandemic on march 11 th , 2020. many mental health professionals and scholars predict that the pandemic will have profound and long-lasting impact on mental health worldwide (holmes et al., 2020) . even prior to the current pandemic, mental illness was a global public health issue. according to the 2013 global burden of diseases study, psychological disorders were the fifth leading cause of disability worldwide . anxiety disorders and major depressive disorder each affected over 250 million people, and acute schizophrenia carried the highest disability weight of all diseases vos et al., 2015) . based on past observations of surges of psychiatric disorders and deaths by suicide following large-scale, life-threatening epidemics-for example, sars in 2003 (cheung et al., 2008 mak et al., 2009) , the 2014-2016 ebola epidemic (jalloh et al., 2018) , and the 1918-19 influenza pandemic (mamelund, 2010; wasserman, 1992) -and the unprecedented scale of the covid-19 pandemic, the extraordinary societal burden of mental illness is likely to grow further and rapidly in the near future. many expect a significant increase in the incidence of posttraumatic stress disorder (ptsd), depression, anxiety, substance use, suicide and other mental disorders, post-covid among the survivors, their caregivers, and healthcare workers (holmes et al., 2020) . indeed, preliminary results from china and italy confirm the high prevalence of ptsd, anxiety, depression, and perceived stress among the survivors of covid-19, and healthcare workers (bo et al., 2020; rossi et al., 2020) . the mental health impact of covid-19 will not be limited to those who are directly confronting (or have confronted) the disease. to contain the spread of the virus, nearly every country has implemented unprecedented levels and scales of quarantine, physical distancing, and even community lockdown. although effective in flattening the epidemic curve (matrajt and leung, 2020) , these public health strategies severely disrupt daily social life and limit interpersonal interactions with adverse consequences of social disconnection and loneliness, which play a central role in poor physical and mental health outcomes (cacioppo et al., 2015) , loneliness has been linked to premature death from stroke and cardiovascular diseases (valtorta et al., 2016) , altered expression of genes involved in inflammation and antiviral response (cole et al., 2015) , as well as increased depression, generalized anxiety disorder, panic disorder, suicide risk and psychosis (badcock et al., 2020; beutel et al., 2017) . with the prolonged social distancing related to covid-19, the general public will soon experience a surge in physical and mental illness. indeed, emerging data from china suggest increased incidence of mental illness among the general population following the covid-19 epidemic (gao et al., 2020; wang et al., 2020) . preliminary data also support the association between increased loneliness and greater depression (killgore et al., 2020) , although this relationship may be moderated by other psychological factors (shrira et al., 2020) . further studies are needed to confirm the role of loneliness in mental health during covid-19 with important factors likely impacting wellbeing controlled, and extend the investigation from depression and anxiety to other mental health concerns such as substance use and symptoms indicative of more severe disorders (e.g., psychosis). the present study examined wellbeing of the general public following prolonged social distancing during the covid-19 pandemic, and the role of loneliness and social network. we selected one of the first regions affected by covid-19 with strictly enforced quarantine and social distancing protocols since late january 2020-hong kong. hong kong is a special , 2020) . however, this early rapid response also means that the community has been living in prolonged social isolation since january 2020. we conducted an online survey of hong kong residents between march 31 st and may 30 th , 2020 to assess the physical and mental wellbeing after the city had implemented widespread social distancing for two months. we expected to observe high rates of common psychiatric symptoms (depression, anxiety, stress) as well as symptoms indicating emergence of severe mental illnesses (psychosis risk). furthermore, we expected that high levels of loneliness would be observed and would significantly explain health and mental health status, even after controlling for other key factors likely impacting wellbeing. respondents of this online survey were adults (age 18 or above), regardless of ethnic backgrounds and nationalities, currently residing in hong kong. a total of 555 unique visitors viewed the survey overview page in the period from march 31 st , 2020 to may 30th, 2020, out of which 461 were eligible for the survey by answering 18 or above for age and selecting "yes" or "part of the time" for the question of hong kong residence. of the eligible participants, 432 (93.7%) completed at least the demographics section and 347 (75.3%) completed the entire survey. only respondents completed at least the demographics section (n = 432) were included in the analyses below. these respondents on average completed 87.6% (median = 100%; sd = 27.5%) of the survey. the survey was available in two languages (traditional chinese and english) and was run on the qualtrics online platform (provo, ut). links to the survey were circulated on social media, local online forums or websites, and via words of mouth to reach the target population of hong kong residents. the survey was anonymous as no identifying information (e.g., name, date of birth, contact information, ip address) was asked or recorded. the median time respondents spent on the survey was 10 min 33s. this study received exempt determination from the university of michigan institutional review board (irb# hum00179454). the survey consisted of 145 questions assessing participants' demographics, general health, mental health, loneliness, and social network. the demographics and general health questions used in this survey (english version) can be found in supplementary information 1. items related to mental health, loneliness, and social network can be found in prior publications (detailed below). for mental health, the 21-item version of the depression anxiety stress scales (dass-21) (p. f. taouk moussa et al., 2001 ) was used to assess depression, anxiety, and stress levels. scores for depression, anxiety, and stress were calculated for each individual and classified into severity levels (normal, mild, moderate, severe, or extremely severe) according to the published norms (s. h. . the 16-item version of the prodromal questionnaire (pq-16) (ising et al., 2012 ) was used to screen for psychosis risk symptoms. for each individual, total score (i.e., number of items endorsed) and distress score (sum of distress related to endorsed items) were computed. a total score of 6 or higher was considered screened positive for psychosis risk syndrome (ising et al., 2012) . the ucla loneliness scale (russell, 1996) was used to assess the respondent's perceived loneliness. the social network index (sni) (cohen, 1997) was used to measure diversity (i.e., number of social roles) and size (number of people with whom the respondent has regular contact) of social network. respondents' demographics, general health, and mental health (dass-21 and pq-16 scores), loneliness (ucla total score), and social network (sni diversity and size scores) were examined with descriptive statistics. to understand the relationship of loneliness and social network to health and mental health, hierarchical regression analyses were conducted. this model comparison approach allows us to examine whether loneliness and/or social network can explain health and mental health above and beyond other demographic, psychological, and socio-political factors that likely have influence one's wellbeing. these include age, sex, exposure to domestic abuse, and worries about covid-19. given the current political context of hong kong where the residents had already been exposed to prolonged societal unrest and distress, we also considered the level of participation in the protest as a potentially influential factor. therefore, in step 1 of the hierarchical regression analyses, age, sex (two dummy coded variables: female, and no response to question of sex), frequency of domestic violence/abuse, level of concern about covid-19, and level of participation in the protests were entered as predictors into the reduced model. in step 2, stepwise method was used to add loneliness (ucla total score) and social network (sni diversity and size) measures as predictors into the full model. the dependent variables included: 1) self-report overall health; 2) numbers of days (over the past 30 days) in which physical health was not good; 3) numbers of days in which mental health was not good; 4) number of days in which poor physical or mental health affected usual activities; 5) number of days in which pain affected usual activities; 6) number of days in which the respondent felt worried, anxious, or tense; 7) dass-21 depression; 8) dass-21 anxiety; 9) dass-21 stress; 10) pq-16 total score; and 11) pq-16 distress score. since level of participation in the hong kong protests was not a significant predictor when included in any of the reduced or full models, and that nearly 20% of the respondents had a missing value on the item of (they chose not to answer the question), we removed this variable from the regression analyses to increase the sample size. the results of the regression analyses with or without this variable were virtually identical. we only report the results without this predictor variable below. because some respondents did not complete all the questions, the percentages reported below were calculated using the number of respondents completed the corresponding section as the denominator. summary of the 432 respondents who completed the demographics section is presented in comparatively, concern about the current covid-19 epidemic was much higher, with 360 (83.3%) of the 432 respondents expressing moderate or extreme concern (figure 1). 392 respondents completed the general health section. for self-perceived overall health, rated on a 1-5 scale (representing "excellent," "very good," "good," "fair," and "poor"), most respondents (71.4%) reported "good" or better (median = 3.0, mean = 2.9, sd = 0.97). about a third (34.9%) endorsed one or more of the following types of illnesses in the past 30 days: head cold or chest cold (14.0%); gastrointestinal illness with vomiting or diarrhea (16.3%); flu, pneumonia, or ear infections (9.7%); an ongoing or chronic medical condition (6.9%). only 3.8% were in mandatory or self-quarantine related to covid-19 (median duration = 14 days). none were in inpatient hospital care. few (9.9%) of the 389 respondents were cigarette smokers (mean = 0.68 packs/day, sd = 0.36) or alcohol drinkers (19.1%; mean = 3.6 drinks/week, sd = 4.2). however, among those who smoke or drink, many endorsed having been smoking (41.0%) or drinking (28.0%) more than usual in the past 30 days. the number of days in which various health-related problems occurred over the past 30 days are summarized in figure 2 . overall, the respondents reported more days affected by mental health issues than by physical health issues. 367 respondents completed the ucla loneliness scale. the mean score was 49.7 (median = 50.0; sd = 10.5), more than one standard deviation above the published norms obtained from samples of college students and nurses in north america (russell, 1996) . 356 respondents completed the social network index, reporting a mean number of social roles of 4.9 (median = 5.0, sd = 1.8, range = 1 -11). the mean number of people with whom the respondents have regular contact (i.e., at least once every 2 weeks) was 14.3 (median = 10.0, sd = 15.6, range = 0 -118). the model statistics of the hierarchical regression analyses are summarized in table 2; coefficients statistics are presented in supplementary information 2 (table s1 ). briefly, even after controlling for the effects of key variables that could impact health and mental health (age, sex, domestic violence exposure, and level of concern about covid-19), loneliness significantly explained variance (r 2 -change ranging from 1.3% to 29.2%) in all of the health and mental health measures (except the number of days in which usual activities were affected by pain). this amount was even higher for models using scores of validated scales of psychiatric symptoms (i.e., dass and pq16) as the dependent variable, with r 2 -change ranging from 12.3% to 29.2%. social network diversity and size did not significantly explain any of the health and mental health measures. the findings of this survey paint a very disconcerting picture of the mental health status among people in hong kong during the covid-19 pandemic. although many respondents reported overall good physical health and few days in the past month in which they were affected by physical health or pain issues, they suffered mental health issues frequently in that they experienced poor mental health or feeling worried, anxious or tense, on average, in more than one-third of the time over the past month. their responses to validated scales of psychiatric symptoms suggest that almost two-thirds (65.6%) reported clinical levels of depression, anxiety, and/or stress. population-wide incidence and prevalence of psychiatric disorders prior to covid-19 have been tracked by the large community-based studies of mental health lee et al., 2011) ; weighted prevalence was estimated at 13.3 % for any past-week for any psychiatric condition, with mixed anxiety and depressive disorder being the most frequent diagnoses. therefore, our results from the current survey indicate a significant increase in the risk for mental illness in the general population. yet more concerning is the high rate (22.5%) of elevated risk for a psychotic disorder observed in this study. previous studies using the same measure found only 4.0% of help-seeking young people in north america screened positive for psychosis-risk (ising et al., 2012) . a prior population-based household survey for mental disorders estimated a lifetime prevalence of all psychotic disorders to be approximately 2.5% among the chinese adult population in hong kong (chang et al., 2017) ; this estimate is similar to the prevalence reported globally, suggesting that the elevated psychosis risk found in this study was not due to a higher "baseline" psychosis risk among hong kong people. this is a population with low rates of smoking (9.9%) or drinking alcohol on a regularly basis (19.1%). while the smoking rate in this sample was similar to that reported in the 2015 census (10.5%) (census and statistics department, 2018), the drinking rate was much higher than the 11.1% reported in the population health survey 2014/15 (centre for health protection, 2017). among those who smoke or drink alcohol regularly, many reported having been smoking (41%) or drinking (28%) more heavily in the past month. taken together, these findings indicate that the societal impact of the covid-19 in hong kong extends beyond the illness itself and well into the future, with sharp increases in the risk for depression, anxiety, stress, psychosis, and substance use. in addition to psychiatric symptoms, level of loneliness was very high in this hong kong sample: it was one standard deviation elevated compared with samples of similar education attainment (college students and nurses) in north america (russell, 1996) . furthermore, loneliness significantly explained physical and mental health across measures, even after accounting for the effects of other important variables (age, sex, domestic abuse/violence frequency, and level of concern for covid-19). the only health measure not significantly explained by loneliness was the number of days affected by pain, likely due to the very low frequency of pain in this sample. whilst the prevalence of psychological distress found in this sample during the pandemic is daunting, our finding that loneliness is playing a central role may give us a handle to address this public health emergency at a societal level. to mitigate the potential epidemic of mental illness in the near future, there is an urgent need to prepare clinicians, caregivers and stakeholders to focus on loneliness. reducing loneliness could result in reduction of mental illness across all diagnostic categories. our finding that social network size (number of social roles, and number of people in the social network) failed to explain any of the health and mental health measures suggests that it is the quality rather than quantity of interpersonal relationships that matters. therefore, interventions that can strengthen social connectedness (e.g., training in communication and social skills, consistent group activities) may exert larger impact than focusing only on increasing the amount of social encounters. furthermore, interventions need to be implemented at a broad societal level rather than for a small fraction of the population. creative solutions, including those leveraging technology, are likely needed to help achieve this goal. it is important to remember that individuals with preexisting psychiatric conditions or those who were already marginalized in society are likely to be impacted even more by the social distancing protocols introduced to reduce the transmission rate of the virus and economic aftermath of the pandemic (tsai and wilson, 2020; yao et al., 2020) , and we must deploy more resources and social capital to address the mental health needs of people disproportionately affected by the pandemic. ongoing pro-democracy movement (reuters, 2020) , which has been assailed by an unprecedented level of violent crackdown (amnesty international, 2019; time, 2019) and persecution by the authorities (pang, 2020) . this sociopolitical context must be considered when interpreting the findings of this study. the city was already embattled with a mental health crisis before the pandemic. a study conducted in late 2019, just before the covid-19 epidemic in hong kong, showed high rates of probable posttraumatic stress (12.8%) and depression (11.2%) among the residents, especially the younger (age 18-35) cohort who show higher level of support for the protests (ni et al., 2020) . the pandemic further deteriorated people's mental health, not only through prolonged social distancing, but also economic decline (lam, 2020a) , surge of unemployment rate (lam, 2020b) , and public mistrust of the government (marlow and hong, 2020; radio television hong kong, 2020) . therefore, the alarming covid-19 related mental health status found in this study was likely amplified by ongoing societal problems, some of which are in common with other countries and some are unique to hong kong. this study has several limitations. the sample was relatively young and highly educated, unlikely to be fully representative of the hong kong population. this was a cross-sectional study and lacked longitudinal data to track changes in mental health over time during the pandemic. however, the rates of psychiatric symptoms founded in this study were higher than the estimates reported in a study of a representative sample conducted in december 2019 (ni et al., 2020) , just before the first confirmed case of covid-19 was reported. this provides some preliminary evidence for the adverse consequences of covid-19 on mental health across broad domains including psychosis. additionally, although level of participation in the hong kong protests was not a significant predictor of mental health status in the regression analyses, it should be noted that a non-trivial proportion of the respondents (~20%) chose not to answer this question. it is possible that respondents who participated frequently in the protests were more likely to skip this question because they were worried about political or legal repercussions. however, it is also possible that those who never or rarely participated in the protests tended to skip this question because of social desirability (the protests are widely supported by people in hong kong). it is unclear whether the data of this question were missing at random or not. in so far as we could test from the available data, we could only conclude that level of participation in the hong kong protests did not predict health/mental health status. this may be because the political crisis and social unrest affected everyone negatively regardless of one's political orientation. obviously, this result applies only to this sample at this given point in time. the political situation has significantly worsened since our survey, so it is possible that the impact of participation in political protests has changed as well. finally, the survey data were collected mostly in april 2020; it is unknown how mental health outcome would be impacted by the lifting of social distancing protocols worldwide, potentially followed by a second-or even third-wave of the pandemic. close monitoring of the mental health impact of this pandemic is warranted. to conclude, this study investigated the mental health status of ordinary citizens and the impact of loneliness in a city that was one of the first regions that practiced population-wide social distancing during the covid-19 pandemic. the results indicate a dire situation with respect to mental health, with highly elevated rates of significant psychiatric symptoms including depression, anxiety, stress, and signs of psychosis risk. subjective feelings of loneliness, but not social network size, significantly explained these increased psychiatric symptoms above and beyond other demographic factors. these findings together suggest that there will likely be an epidemic of mental illness in the near future, and preparing clinicians, caregivers and stakeholders to focus on alleviating loneliness would be one effective way to mitigate this impending public health crisis. the authors thank the respondents for donating their valuable time to complete this survey. this research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. note. all predictive models included 6 predictive variables: age, sex (two dummy coded variables: female, and no response to the question of sex), frequency of domestic abuse/violence, level of concern about covid-19, and ucla loneliness score. change statistics were relative to the reduced model, which contained only 5 predictive variables (i.e., all variables except ucla loneliness score). physical health was not good: mean = 4.8 days (sd = 6.9). b) mental health was not good: mean = 11.6 days (sd = 10.0); c) usual activities were affected due to health problems: mean = 3.9 days (sd = 7.2); d) usual activities were affected due to pain: mean = 1.9 (sd = 4.5); and e) feeling worried, anxious, or tense: mean = 14.1 days (sd = 10.8). coronavirus disease (covid-19) in hk [www document multidisciplinary research priorities for the covid-19 pandemic: a call for action for mental health science. the lancet psychiatry the validity of the 16-item version of the prodromal questionnaire (pq-16) to screen for ultra high risk of developing psychosis in the general help-seeking population impact of ebola experiences and risk perceptions on mental health in sierra leone letter to the editor. loneliness : a signature mental health concern in the era of covid-19 pandemic and politics push hong kong's economy into record slump hong kong's unemployment rate rises to highest since prevalence, psychosocial correlates and service utilization of depressive and anxiety disorders in hong kong: the hong kong mental morbidity survey (hkmms) a community study of generalized anxiety disorder with vs. without health anxiety in hong kong the structure of negative emotional states: comparison of the depression anxiety stress scales (dass) with the beck depression and anxiety inventories manual for the depression anxiety & stress scales long-term psychiatric morbidities among sars survivors the impact of influenza on mental health in norway hong kong police arrest protesters for violating social distancing guidelines evaluating the effectiveness of social distancing interventions to delay or flatten the epidemic curve of coronavirus disease depression and post-traumatic stress during major social unrest in hong kong: a 10-year prospective cohort study hong kong police detain veteran democracy activists in raids hundreds of medical workers walk off in protest timeline: key dates in hong kong's anti-government protests [www document mental health outcomes among frontline and second-line health care workers during the coronavirus disease 2019 (covid-19) pandemic in italy ucla loneliness scale (version 3): reliability,validity, and factor structure disability weights for the global burden of disease 2013 study covid-19 related loneliness and psychiatric symptoms among older adults: the buffering role of subjective age psychometric properties of a chinese version of the 21-item depression anxiety stress scales (dass21) covid-19: a potential public health problem for homeless populations loneliness and social isolation as risk factors for coronary heart disease and stroke: systematic review and metaanalysis of longitudinal observational studies immediate psychological responses and associated factors during the initial stage of the 2019 coronavirus disease (covid-19) epidemic among the general population in china the impact of epidemic, war, prohibition and media on suicide: united states, 1910-1920 patients with mental health disorders in the covid-19 epidemic key: cord-272207-jtvf257r authors: liao, qiuyan; cowling, benjamin j; lam, wendy wt; ng, diane mw; fielding, richard title: anxiety, worry and cognitive risk estimate in relation to protective behaviors during the 2009 influenza a/h1n1 pandemic in hong kong: ten cross-sectional surveys date: 2014-03-27 journal: bmc infect dis doi: 10.1186/1471-2334-14-169 sha: doc_id: 272207 cord_uid: jtvf257r background: few studies have investigated associations between psychological and behavioral indices throughout a major epidemic. this study was aimed to compare the strength of associations between different cognitive and affective measures of risk and self-reported protective behaviors in a series of ten cross-sectional surveys conducted throughout the first wave of influenza a/h1n1 pandemic. methods: all surveys were conducted using questionnaire-based telephone interviews, with random digit dialing to recruit adults from the general population. measures of anxiety and worry (affective) and perceived risk (cognitive) regarding a/h1n1 were made in 10 serial surveys. multivariate logistic regression models were used to estimate the cognitive/affective-behavioral associations in each survey while multilevel logistic models were conducted to estimate the average effects of each cognitive/affective measure on adoption of protective behaviors throughout the ten surveys. results: excepting state anxiety, other affective measures including “anticipated worry”, “experienced worry” and “current worry” specific to a/h1n1 risk were consistently and strongly associated with adoption of protective behaviors across different survey periods. however, the cognitive-behavioral associations were weaker and inconsistent across the ten surveys. perceived a/h1n1 severity relative to sars had stronger associations with adoption of protective behaviors in the late epidemic periods than in the early epidemic periods. conclusion: risk-specific worries appear to be significantly associated with the adoption of protective behaviors at different epidemic stages, whereas cognitive measures may become more important in understanding people’s behavioral responses later in epidemics. future epidemic-related psycho-behavioral research should include more affective-loaded measures of risk. understanding relationships between psychological state and protective behaviors during respiratory infectious disease epidemics (rides) can inform risk communication and interventions addressing behavior change [1, 2] . studies of behavioral change during rides usually assess risk perception as an affect-neutral cognitive ("cognitive") process, commonly using measures such as perceived personal probability of infection or perceived severity of the illness [3] [4] [5] , or as a more affect-active process, by assessing worry and anxiety [6] [7] [8] [9] [10] . the latter are frequently referred to as "affective" dimensions of risk, though worry is often considered a cognitive dimension of anxiety [11] . the dual-process theory proposes that responses to external stimuli involve two different processing systems, one being deliberate, slow and rule-based, the other being experiential, quick and intuitive [12] . these two systems may reflect distinct response pathways to risk: risk-asanalysis (cognitive estimates) and risk-as-feeling (affective estimates) [13] . the affect heuristics and risk-as-feeling hypotheses imply that affect quickly and more efficiently guides cognitive risk analysis and behavior [13] [14] [15] . previous studies found that in the ride situation when personal threat is highly uncertain, affective measures of risk more powerfully predict protective behavior uptake than do cognitive measures [6, 10] . therefore, both cognitive and affective components of risk appear to be relevant to understanding rides-related population behavior [1] . in the early epidemic stage when uncertainty about the epidemic characteristics, treatment and prevention is higher, affective responses may be optimal for guiding behavioral change [6, 9, 10] but cognitive risk responses should increasingly drive behavior as the epidemic evolves. we term these "psycho-behavioural" associations. given this, the question arises: should studies or assessments done early in the epidemic emphasize affect-based assessments of risk, whereas those performed later in the epidemic emphasize cognitive-based measures, in order to optimally predict behaviors? otherwise, it is possible that research conducted in different stages of an epidemic may observe different strengths for the same psycho-behavioral association and misattribute these. observed variation in the strength of specific psycho-behavioral associations across an epidemic introduces avoidable measurement error in the target cognitive/affective measure which will subsequently influence its association with behavioral change, reducing the apparent reliability of risk assessments as predictors of behavior change during rides. this raises questions about whether the same or similar associations would be repeatedly identified in surveys conducted in different epidemic periods within the same population. however, very few studies appear to have examined the consistency of these psycho-behavioral associations across different ride stages [6] . we therefore performed secondary data analyses for data collected in a series of ten consecutive cross-sectional surveys spanning the epidemic wave of 2009 pandemic influenza a/h1n1 in hong kong [16] . the objectives of this study were to compare the strength and stability of associations between affective and cognitive measures of risk and the adoption of ride-related health protective behaviors. this was assessed by comparing the associations between health protective behaviors against a/h1n1 and different cognitive/affective measures of risk used for each of the ten cross-sectional surveys. most psycho-behavioral studies of new communicable respiratory disease outbreaks were rapidly implemented [2] . consequently, many used unrefined questionnaires, with several suffering from minimal theoretical support for the inclusion of specific psychological variables, items of limited utility in understanding behavioral change or items that may have posed task difficulty for respondents [1, 2] , and multiple items, which increase interview load, thereby reducing interview efficiency and the accuracy of results. to inform future item selection, we therefore also sought to assess the difficulty respondents faced in answering different question measures of risk perception. this was done by examining proportions of missing data for different psychological measures as an indirect reflection of task difficulty. our null hypotheses were: 1. cognitive and affective measures of risk will not differ in terms of stability of association with adoption of protective behaviors across the ten cross-sectional surveys; 2. for the same associations measured at different epidemic periods, strength of associations between affective/cognitive measures and adoption of health protective behaviors will not decline/increase across epidemic stage; 3. there will be no difference in proportions of missing data for cognitive estimation items such as estimates of the likelihood of contracting influenza infection than other risk assessment formats reflecting no differences in the difficulties posed to respondents by such items [17, 18] . between april and november 2009, we monitored population psycho-behavioural responses to the 2009 influenza a/h1n1 pandemic using 13 cross-sectional surveys (s1-s13) covering the entire first wave of the a/h1n1 pandemic in hong kong [16] . during the survey period, approximately 15% of the hong kong population were infected with this new virus [19] . here we report data from 10 of these (s3-s5 and s7-s13). the first two surveys (s1 and s2) conducted between april and may were excluded from this study because of incompatibility with later surveys and because the local a/h1n1 epidemic did not start until s3 was conducted. survey s6 was excluded because of sample insufficiency. all surveys utilized identical methods involving random household telephone interviews based on randomly computergenerated landline telephone numbers of all hong kong households. one adult aged 18 or above within each household was randomly selected based on a kish grid and invited for the telephone interview. sampling details have been published elsewhere [16] . the study received ethical approval from the institutional review board (irb) of the university of hong kong. the irb waived written informed consent in lieu of verbal consent given the format of these ten telephone surveys. all participating respondents gave verbal consent for telephone interviews. the sample sizes for each of the ten surveys (s3-s5, s7-s13) ranged between 1,000-1,404, with response rates of 65.6%-72.7% [16] . surveys were conducted every two weeks with data collection completed within 3-5 days for each survey. the ten surveys covered different a/h1n1 epidemic stages in hong kong. specifically, s3 (jun 9-12, 2009) was conducted when local a/h1n1 human cases were first identified in hong kong; s10 (sep [8] [9] [10] [11] 2009 ) was conducted when the local epidemic reached peak activity and s13 (nov 9-13, 2009) when epidemic activity had declined substantially (additional file 1: figure s1 ). core items for the questionnaires used in the ten surveys were retained throughout. minor changes were made on one measure of risk perception (the comparator "perceived relativesusceptibility relative to others" was made more precise by specifying age and gender at s11) and two new items (current worry and infectivity relative to seasonal flu) were added in later surveys to refine measurement and during the surveys. table 1 details psychological measures associated with risk covered by different survey periods. four measures (state anxiety, anticipated worry, experienced worry and current worry about a/h1n1 infection) were classified as affective measures. four other measures (perceived absolute susceptibility and perceived relative susceptibility to a/h1n1 infection, perceived a/ h1n1 severity relative to sars and perceived a/h1n1 infectivity relative to seasonal influenza) were classified as cognitive estimates of risk. the definitions, questions and response scales for these measures are detailed below and in the additional file 2: table s1. respondents' anxiety level was assessed with a previously validated state-anxiety scale of the state-trait anxiety inventory (stai) wherein respondents' rate their feelings in response to ten general statements [6, 20] . positive feeling statements were reversely coded and then the mean scores of the ten items (possible range 1 -4) were calculated for subsequent analyses to overcome the problems of randomly missing items. (additional file 2: table s1 ). respondents were asked to rate their worry about possibly developing a/h1n1 symptoms within the next 24 hours (additional file 2: table s1 ). hence this measure was prospective. respondents were asked to recall whether they had experienced any worry over the past week about contracting a/h1n1 (additional file 2: table s1 ). this measure was retrospective. starting from survey 9 ( table 1) respondents were asked about their current level of worry related to a/h1n1 (additional file 2: table s1 ). this measure was current. respondents estimated their personal likelihood of contracting a/h1n1 in the coming months throughout the ten surveys (additional file 2: table s1 ). this measure was prospective. in the earlier surveys, respondents estimated their personal likelihood of contracting a/h1n1 relative to another table 1 psychological measures and their proportions of missing data throughout the 10 surveys s3 s4 s5 s7 s8 s9 s10 s11 s12 s13 missing rang% c totally missing% note "√" indicates that the measure was covered in the survey. a the measure of anxiety state included ten items asking about ten general feeling statements and thereby the proportions of missing data for anxiety in the table were the highest proportion of missing data of the item among the ten statement items. b these two items were combined as "perceived relative susceptibility" in the analysis. c the range of missing proportions across the covered surveys. (unspecified) person in the general population. in later surveys (s11-s13), this item was slightly changed to personal likelihood of contracting a/h1n1 relative to another person of similar age and sex in the general population (additional file 2: table s1 ). perceived a/h1n1 severity relative to sars throughout the 10 selected surveys, respondents estimated the perceived severity of a/h1n1 infection relative to sars (additional file 2: table s1 ). starting from survey 9 (table 1) , this item was added in the surveys to assess the infectivity rate of a/h1n1 relative to seasonal influenza, serving as an additional measure to assess the perceived severity of a/h1n1. the frequencies of three protective behaviors against a/h1n1 were polled throughout the ten surveys. these were avoiding crowded places, maintaining good indoor ventilation and disinfecting the household frequently. all three protective measures were recommended by the hong kong government to minimize the transmission of influenza during the epidemic [21] . respondents were asked whether they had adopted any of these three protective behaviors over the past seven days, and if so, whether the behaviors were adopted for a/h1n1 prevention. these behavioral outcomes were dichotomized as "1" (adopted for preventing a/h1n1) and "0" (not adopted or adopted for reasons other than preventing a/h1n1) for subsequent analyses. previous analyses showed trends for psycho-behavioral associations were similar across the responses range on all the above risk measures [16] . therefore, these responses were dichotomized as either above or below a threshold for subsequent analyses in order to facilitate comparison, and the process detailed in the additional file 2: table s1 . first, the proportions of missing data for all psychological measures associated with risk were calculated. then, multiple imputation was used to generate ten values for each missing value, the mean of which was substituted for the missing value. for each survey, one multiple logistic regression model calculated the associations between each of three protective behaviors (avoiding crowded places, maintaining good indoor ventilation and disinfecting household frequently) and each psychological variable (psycho-behavioral association) plus the corresponding 95% confidence interval. the psychobehavioral association was adjusted for respondents' age, gender, education, marital status and birth place in each logistic regression model because all these demographics are potential confounders of these psycho-behavioral associations [2] . i 2 (an index of variability) based on q-statistic was calculated to quantify heterogeneity of these psycho-behavioral associations across the ten surveys and to determine the appropriateness of combining the data from ten surveys to calculate averaged effects. i 2 produces values ranging between 0 and 100%, indicating the percentage of the total variation across surveys due to heterogeneity rather than chance [22] . values of 25%, 50% and 75% arbitrarily indicate low, medium and high heterogeneity, respectively [22] . all studied psycho-behavioral associations had either low or low-medium heterogeneity except that the associations between experienced worry and disinfecting the household frequently and between perceived severity relative to sars and disinfecting the household frequently had medium-tohigh heterogeneity across the ten surveys. therefore, random-effect multilevel logistic regression models were used to estimate the pooled effect of each psychobehavioral association across the ten surveys. for these multilevel models, individual responses were specified as the first level while survey periods were specified as the second level. all multilevel logistic regression models were adjusted for age, gender, education, marital status and place of birth. to minimize potential interactions (moderation or mediation) between different psychological measures [10, 23] , only one psycho-behavioral association was assessed in each model. all analyses were conducted based on data excluding the small proportions (0.2%-1.5%) of subjects who reported having had influenza-like illness (ili: fever plus cough or sore throat) within the two weeks prior to each survey. p-values <0.05 were considered to be statistically significant. all analyses were conducted using stata software (version 10.1; stata corp., college station, tx). the ten surveys included a total of 10,345 subjects after excluding 92 (0.9%) subjects with ili. the effect sizes for differences between the sample characteristics (age, gender, education and place of birth) of each survey and the hong kong population were small, indicating good sample representativeness [16] . missing data for the risk-related psychological measures table 1 reports the proportions of missing data for each psychological measure and survey. among all the measures, perceived absolute susceptibility and perceived relative susceptibility to a/h1n1 infection had the highest proportions (totally missing 5.63% and 5.82%, respectively) of missing data throughout the surveys, followed by perceived a/h1n1 infectivity relative to seasonal influenza (3.04%) and perceived a/h1n1 severity relative to sars (1.50%). affective measures generally had few missing data (below 1%, table 1 ). figures 1, 2 and 3 show forest plots describing the associations of different risk-related psychological measures with avoiding crowded places (figure 1) , maintaining good indoor ventilation ( figure 2 ) and household disinfection (figure 3) , respectively, throughout the ten surveys. the patterns of psycho-behavior associations were similar for the three types of health protective behaviors. for each of the three figures, the upper four forest plots illustrate the associations between affective measures and adoption of protective behaviors while the lower four illustrate the associations between cognitive measures and adoption of protective behaviors. averaged effects of different perceptions on adoption of each of the three protective behaviors are indicated by the lower diamond of each forest plot and in table 2 . overall, all risk-related psychological variables were positively and significantly associated with all three heath protective behaviors except for the association between perceived absolute susceptibility and household disinfection ( table 2) . figures 1, 2 and 3 suggest that all affective measures excepting state anxiety are more strongly associated with adoption of protective behaviors than are cognitive measures, these associations being consistently positive and statistically significant across the ten surveys. in particular, current worry and experienced worry had the strongest associations with adoption of protective behaviors among the eight risk-related psychological measures. state anxiety was only significantly associated with avoiding crowds in s4 and s10 (figure 1) , with maintaining good indoor ventilation in s4 (figure 2) , and with household disinfection in s7, s8, s10 and s13 (figure 3 ). perceived absolute susceptibility was only weakly and significantly associated with avoiding crowds in s7 and s11 ( figure 1 ) and maintaining good indoor ventilation in s7, s11 and s13 (figure 2 ) but not with household disinfection across the ten surveys ( figure 3 ). perceived relative susceptibility seemed to have stronger associations with avoiding crowds and household disinfection than did perceived absolute susceptibility (figures 1 and 2) . no change was seen in associations between perceived relative susceptibility compared to another person, and adoption of protective behaviors in s10-s13 when the refined measure of perceived relative susceptibility specified "a general person of similar age and gender". perceived higher a/h1n1 severity relative to sars was more likely to be significantly associated with adoption of protective behaviors in later (s10-s13) than earlier surveys, a pattern not found for other cognitive measures (figures 1, 2 and 3) . perceived a/h1n1 infectivity relative to seasonal influenza was generally significantly associated with adoption of health protective behaviors but the associations were relative weaker than the associations between perceived a/h1n1 severity relative to sars and adoption of health protective behaviors (figures 1, 2 and 3 ). our findings were mostly consistent with those hypothesized and the null hypotheses were largely rejected. the main finding is that affective measures of risk perception generally had stronger associations with reported adoption of health protective behaviors during the a/h1n1 pandemic than did cognitive measures. this finding is consistent with those from other studies conducted during both sars [6] and pandemic a/h1n1 [10, 24] , suggesting that affective components contribute significantly to adoption of protective behaviors in response to the threat during epidemics over and above simpler cognitive risk estimates. while previous studies were mainly conducted in early epidemic periods [10, 24] , this study examined affectivebehavioral associations across the entire epidemic wave of a/h1n1 in hong kong and found that the association between affect-loaded risk measures and adoption of protective behaviors were consistently strong and positive across different epidemic periods. studies of the anxiety-behavior association throughout the sars epidemic found consistently significant and positive associations during the early epidemic phase surveys but mostly non-significant associations in late epidemic phase surveys [6] . the present study did not duplicate this pattern for any of the four affective measures. reported anxiety level was inconsistently associated with adoption of health protective behaviors in these 10 surveys. one possible reason could be that the measure we used assessed general anxiety only rather than anxiety specific for a/h1n1. furthermore, overall reported state anxiety levels remained quite stable and consistently low throughout the a/h1n1 epidemic [16] , indicating a floor effect, suggesting that a low level of anxiety has little effect on these behaviors. other affective measures including anticipated worry, experienced worry and current worry generally involve less intense affective components compared with anxiety and thereby are more likely to covary with behavioral change. in particular, our study found that experienced worry and current worry seemed to have stronger associations with adoption of protective behaviors than did anticipated worry. one possible reason could be that the actual affective experience or associated processing may be more strongly associated with behavioral change than its anticipation, which may be subject to forecasting errors [23] . cognitive risk assessments, in particular perceived susceptibility to a/h1n1 (either absolute or relative susceptibility) had weak associations with adoption of protective behaviors. this suggests that cognitive-behavioral models such as the health belief model [25, 26] that rely primarily on purely cognitive estimates of risk to predict behavioral change should perform relatively more poorly at predicting the adoption of protective behaviors during rides. cognitive-behavioral models generally assume rational processing of external information to inform action. however, during rides particularly in the early stages, uncertainty is usually widespread and poses high [9] or ambiguous personal threat. consequently, people may face difficulties when attempting to quantify the probabilities of their risk of acquiring the infection and the severity of associated disease. whether it is threat ambiguity, task difficulty in determining risk magnitude or a primary affective response that modifies cognition, that leads to affect-related measures dominating remains unclear. this study found that the proportions of missing data for purer cognitive risk perception measures, particularly perceived absolute/relative susceptibility to a/h1n1 were greater than for affect-loaded measures, suggesting that respondents may face greater figure 3 associations between psychological responses and disinfecting household frequently during a/h1n1 pandemic. task difficulties in comprehension and/or responses to such questions under epidemic circumstances. further study is needed to confirm the extent of this effect. perceived relative susceptibility seemed to have stronger associations with adoption of protective behaviors than perceived absolute susceptibility. perceived susceptibility measured in this relative way involves social comparison and accommodates the influences of optimistic bias [27] and therefore probably involves more cognitive processing. more cognitive processing is associated with greater risk estimates and psychological distress [28] . this might account for the more substantial associations with behavioral change than seen for simple personal risk estimates. associations between cognitive risk perception measures and protective action were quite inconsistent across the ten selected surveys in this study. previous reviews concluded associations between cognitive risk perception and adoption of protective behaviors during rides were inconsistent [29] . our evidence suggests a major reason for this inconsistency lies in these studies being conducted in different epidemic stages [6, 30, 31] . our hypothesis was that cognitive factors were more important in changing human behaviors in the later epidemic stage when people had more knowledge and less uncertainty about the threat. this study found that the associations between perceived a/h1n1 severity relative to sars and adoption of each of the three protective behaviors became significantly and consistently positive starting from survey 10 after the a/h1n1 case confirmations had peaked, consistent with our hypothesis. however, this pattern of associations was not found for perceived susceptibility. perceived a/h1n1 infectivity relative to seasonal flu, though not measured before survey s9 had weaker associations with adoption of health protective behaviors, than did perceived a/h1n1 severity relative to sars in each survey and overall. however, these two measures assessed different aspects of a/h1n1 severity with the former focused on the infectivity rate of a/ h1n1 while the latter may primarily focus on the fatality rate of a/h1n1. further study is needed to confirm which aspects of disease severity could be more important in motivating behavior change. study limitations include the serial cross-sectional design and thereby reverse-causality remains a possible explanation. nonetheless, it is difficult to think of plausible mechanisms whereby, for example, disinfecting one's home will lead to greater worry regarding infection. alternatively, the associations could be spurious but this is unlikely given the consistent pattern of the associations in 10 separate samples. it therefore seems most likely that the protective behaviors are consequential on the risk perceptions, and not vice versa. examining psychobehavioral associations using longitudinal data during rides is difficult due to their often-rapid evolution and the short lead-time compared to the need to obtain and retain large cohorts for follow-up surveys. conducting a series of consecutive cross-sectional surveys to investigate the psycho-behavioral associations is a better option than using a single cross-sectional survey. there may be concerns about the generalizability of our findings to more severe rides. for example, during the initial phase of the sars epidemic, population state anxiety regarding the epidemic was much higher and thereby had strong association with protective behavioral change [6] . however, sars was the first of the new wave of rides, and a degree of risk fatigue may have subsequently set in. considering the common situation during rides, we believe that most of the findings in this study could be all data represent odds ratios and their corresponding 95% confidence intervals (in parentheses). all odds ratios were adjusted by age, gender, education, marital status and birth place. **p<0.01; *** p < 0.001. applicable in other rides. finally, because all data were self-reported the results may reflect social desirability bias. this study raises important implications for future respiratory communicable disease-related psycho-behavioral research and public health interventions. first, affective responses improve understanding of behavioral responses throughout different ride periods and must form part of measures in relevant studies. however, intense but nonspecific affect such as generalized state anxiety is probably less useful for understanding public behavioral responses during most epidemics where perceived milder threat fails to arouse such affect. less intense, specific affective responses to a identifiable, if uncertain threat that currently activates or has in the past activated worry may be more likely to show strong and consistent effects on behavioral change across different epidemic periods. second, cognitive risk estimates during the early epidemic stage may be poor at predicting human behavioral change and present task difficulties to respondents. however, cognitive risk estimates may inform individual behavioral change later in the ride epidemic trajectory and should be included in studies conducted during these phases. relative measures of perceived susceptibility appear superior to perceived absolute susceptibility in predicting behavioral change and thereby are preferable where questionnaire brevity is an issue. from a public health perspective, recognizing that the public may not show expected "rational" behaviors during rides is important. therefore, risk probabilities alone are unlikely to be sufficient to motivate protective behaviors. what affective strategies to use to best motivate behavioral change awaits clarification. risk perceptions related to sars and avian influenza: theoretical foundations of current empirical research demographic and attitudinal determinants of protective behaviours during a pandemic: a review an outbreak of the severe acute respiratory syndrome: predictors of health behaviors and effect of community prevention measures in hong kong, china factors influencing the wearing of facemasks to prevent the severe acute respiratory syndrome among adult chinese in hong kong pandemic influenza in australia: using telephone surveys to measure perceptions of threat and willingness to comply longitudinal assessment of community psychobehavioral responses during and after the 2003 outbreak of severe acute respiratory syndrome in hong kong initial psychological responses to swine flu public perceptions, anxiety, and behaviour change in relation to the swine flu outbreak: cross sectional telephone survey situational awareness and health protective responses to pandemic influenza a (h1n1) in hong kong: a cross-sectional study the association between pandemic influenza a (h1n1) public perceptions and reactions: a prospective study worry: a cognitive phenomenon intimately linked to affective, physiological, and interpersonal behavioural processes the self-regulation of health and illness behaviour risk as analysis and risk as feelings: some thoughts about affect, reason, risk, and rationality the affect heuristic risk as feelings community psychological and behavioral responses through the first wave of the 2009 influenza a(h1n1) pandemic in hong kong risk perceptions: assessment and relationship to influenza vaccination risk perception measures' associations with behavior intentions, affect, and cognition following colon cancer screening messages epidemiological characteristics of 2009 (h1n1) pandemic influenza based on paired sera from a longitudinal community cohort study state trait anxiety inventory: a test manual/test form center for health protection hong kong government: general guideline: a guide to personal, home and environmental hygiene: keep clean be healthy measuring inconsistency in meta-analyses emotions and preventive health behavior: worry, regret, and influenza vaccination avoidance behaviors and negative psychological responses in the general population in the initial stage of the h1n1 pandemic in hong kong the health belief model and personal health behaviour the health belief model in the prediction of dietary compliance: a field experiment do moderators of the optimistic bias affect personal or target risk estimates? a review of the literature the function of credibility in information processing for risk perception factors associated with uptake of vaccination against pandemic influenza: a systematic review a tale of two cities: community psychobehavioral surveillance and related impact on outbreak control in hong kong and singapore during the severe acute respiratory syndrome epidemic the impact of community psychological responses on outbreak control for severe acute respiratory syndrome in hong kong anxiety, worry and cognitive risk estimate in relation to protective behaviors during the 2009 influenza a/h1n1 pandemic in hong kong: ten cross-sectional surveys additional file 1: figure s1 . the a/h1n1 pandemic curve in hong kong and timeline of the surveys.additional file 2: table s1 . questions for measuring anxiety, worry and risk perception in the study and their associated response scales. the authors declare that they have no competing interests.authors' contributions ql participated in the study design, analyzed the data, interpreted the data and drafted the manuscript. bjc supervised the research, contributed to study design, data interpretation and amended the manuscript. wwtl contributed to study design, data interpretation and amended the manuscript. dwmn contributed to questionnaire design, coordinated data collection and amended the manuscript. rf conceived of the study, designed the questionnaire, interpreted data and amended the manuscript. all authors read and approved the final manuscript. key: cord-293403-o1i999hy authors: holliday, ian; tam, wai-keung title: e-health in the east asian tigers date: 2004-09-11 journal: int j med inform doi: 10.1016/j.ijmedinf.2004.08.001 sha: doc_id: 293403 cord_uid: o1i999hy objective: the article analyzes e-health progress in east asia's leading tiger economies: japan, hong kong, singapore, south korea and taiwan. it describes five main dimensions of e-health provision in the tigers: policymaking, regulation, provision, funding and physician-patient relations. methods: we conducted a series of fieldwork interviews and analyzed key healthcare websites. results and conclusion: our main finding is that the development of e-health in the region is less advanced than might be expected. our explanation focuses on institutional, cultural and financial factors. the application of information technology (it) to public sector operations sometimes captured in the notion of e-government is starting to have an impact on developed healthcare systems the world over. as time goes by, that impact is expected to become even more pronounced. ''the consensus seems to be that new information technologies will significantly affect almost every aspect of health care,'' wrote blumenthal [1] . in this article, we examine the progress of e-health in the five leading economies of east asia: japan, hong kong, singapore, south korea and taiwan. each seeks to place itself at the forefront of the information revolution and has high levels of internet access and usage. each also has a sophisticated healthcare system dedicated to securing maximum healthcare benefit at minimal cost. by standard outcome indicators, these systems all have very good records. the tigers, therefore, form a cluster in which e-health might be expected to be notably advanced. however, our finding is that although some progress is being made, it remains limited. it is also variable across the five societies. the article begins by reviewing some of the literature on e-health taking from it a series of critical dimensions and issues. it then briefly analyzes the two relevant contextual aspects of the east asian tigers: their participation in the information age and the nature of their healthcare systems. on these bases, it examines their e-health progress, focusing on the major themes unearthed in the contemporary literature. finding limitations and variations, it concludes by thinking through possible explanatory factors, focusing on institutional, cultural and financial issues. much of the existing e-health literature has been developed in the context of the united states, reflecting both us leadership in the information age and the continuing search for solutions to us healthcare problems. five main themes are prominent. four of the five address distinct dimensions of the broad policy and management framework for healthcare, examining internet impacts on policymaking, regulation, provision and funding. the fifth theme looks inside the healthcare sector and inside the surgery, at the implications of the internet for physician-patient relations. eventually, this may have policy significance, but for now, it is best treated separately. the major argument made about healthcare policymaking is that the us government has been slow to engage with the numerous issues generated by the it revolution [2] . the core features of that revolution, notably enhanced information flows, increased networking possibilities and novel commercial opportunities, are now well documented [3] . however, it is said that in us healthcare, most policy actors in both congress and the executive branch continue to focus on pre-information age agendas. although, the bush administration has started to address these concerns, the result remains something of a lack of internet-related policy activity and only a limited number of perspectives on the internet's potential to transform the us healthcare system. clearly structural features of the us system, including fragmentation both of government and of the healthcare sector, play key roles. looking at the narrower sphere of regulation, concerns are expressed about the failure of regulatory agencies to keep pace with internet-related developments. goldsmith notes that the internet generates many potential regulatory problems, ranging from licensing e-health practitioners to monitoring information quality in a virtual world with no boundaries [4] . fried et al. detail some of the obstacles placed in the way of e-health by existing regulations, holding that individuals and organizations must navigate a maze of rules and codes, old and new, if they wish to implement fresh ideas and approaches [5] . kassirer's prediction is that the courts will play a role when substandard medical advice provided through web sites or e-mail yields poor medical outcomes. he believes that courts will be especially important when professional advice is given without a direct patient encounter, or when state lines are crossed [6] . some regulatory issues are us-specific, but many have much wider relevance. partly building on the regulatory theme, analysts have also debated the limitations currently imposed on healthcare provision through the internet. kleinke argues that the internet will not contribute to a solution to the administrative redundancies, economic inefficiencies, and quality problems that have long plagued the us healthcare system. instead, it will exacerbate the cost and utilization problems of a system in which patients demand more, physicians are legally and economically motivated to supply more, and public and private purchasers are expected to pay the bills [7] . goldsmith holds that the challenges of standardizing coding and formats for clinical information, and protecting patient privacy, will hinder the realization of network computing potentials in healthcare [4] . the problems to which these and other authors point are structural. economic, organizational, legal, regulatory, and cultural conflicts rooted in the us healthcare system are all barriers to e-healthcare provision. further problems are found in the sphere of healthcare funding. shortliffe criticizes congress for focusing on short-term benefits, arguing that research investment for e-health must be balanced between basic and applied analyses [8] . robinson examines the effect of distinct forms of capital on the development of the healthcare internet. in the late 1990s, venture capital flooded into the ehealth sector, rising dramatically from us$3 million in early 1998 to us$335 million in late 2000. in the same period, 26 e-health firms went public, raising us$1.35 billion at their initial public offerings. however, the technology-sector crash in late 2000 hit the e-health sector especially hard, prompting an extended period of consolidation between e-health and more conventional firms [9] . us funding problems thus relate to both the public and the private sectors. finally, analysts have looked inside the surgery at physician-patient relations. existing survey data show that citizens make considerable use of the internet for healthcare information and services, mostly of a generic kind [10] . indeed, anderson reports that in 2002, 80% of us adults with internet access did so [11] . as more patients go online, increasing numbers will turn up in surgeries with internet-fueled questions and concerns. meeting the growing expectations of these individuals will be a significant challenge for physicians [12] . assessing the likely impact, kassirer argues that the internet will change the physician-patient relationship in unpredictable ways, with some aspects of electronic communication strengthening the bond, and others undermining it [6] . goldsmith believes patients have most to gain from the emergence of the internet, arguing that it will rebalance the steeply asymmetrical medical knowledge held by patients and physicians [4] . using information gained through internet searches, patients can now open their dialogues with physicians at a much higher level than before, and thereby gain leverage in the care process. ball and lillis also discuss the potential challenges the internet presents to physicians. as internet searches often generate as many questions as answers, physicians are likely to find themselves under increased workload pressures [13] . the variable quality of healthcare information accessed through online searches [14] , a matter that is being actively addressed by bodies such as the health on the net foundation (www.hon.ch) and the internet healthcare coalition [15] , can only reinforce those pressures. zupko and toth hold that physicians sometimes encounter a form of cultural shock when confronted by well-informed patients [16] . it is therefore perhaps not surprising that an april 2002 survey found that physicians are much more reluctant than patients to use the internet for healthcare interactions. while 90% of patients wanted to exchange e-mail with their doctors, only about 15% of doctors actually did so. physician-patient confidentiality, time concerns and increased exposure to malpractice liability were cited as primary reasons for doctors' wariness [17] . in the face of this mounting speculation and evidence, lumpkin is sanguine, however, contending that the physician-patient encounter is little changed, despite widespread internet usage in healthcare [18] . though focused on the us, the existing e-health literature generates key themes for an analysis of progress in other parts of the world, including the east asian tigers. however, before exploring those themes, we first present some basic contextual information about our five societies. two features of the east asian tigers are particularly relevant to this analysis: their participation in the information age and the nature of the healthcare systems in which their application of it needs to be assessed. in this section, we examine both features. looking at broad social participation, it was exploited more rapidly in the five east asian tigers than in any other global cluster. for many years, the nielsen//netratings global internet index has ranked all five societies in the top 10 worldwide for personal computer (pc) connections and internet access and usage. the four smaller societies, hong kong, singapore, south korea and taiwan, are particularly advanced. furthermore, the severe acute respiratory syndrome (sars) crisis that hit the region in spring 2003 gave a major boost both to internet usage in general, and to e-health in particular [19] . in hong kong, for instance, the number of active internet users increased by 13% from february to april 2003, before falling back by 3% from april to june 2003. the overall increase was 10%. also at the start of 2003, the time spent online by hong kong people first increased by 49% and then fell back by 18%, registering an overall increase of 22% [20] . consistent with the image of economic and social dynamism, they have projected for many years now, the east asian tigers are among the most advanced it societies on earth. to some extent, this strong it orientation is the product of developmental state strategies. with the partial exception of hong kong, the east asian tigers have long placed considerable faith in stateled growth strategies. furthermore, for many years they have frequently focused those strategies on it and it-related sectors. in japan, in the 1980s, the fabled ministry of international trade and industry targeted supercomputers and the fifth generation as a major development project [21] . despite a long period of economic stagnation in the 1990s, the japanese it industry remains a significant global force. in singapore in the 1980s, the state took the lead in nurturing wafer fabrication, the most sophisticated ''front end'' of the semiconductor industry. chartered semiconductor manufacturing, established by the government in 1988, is now the third largest silicon foundry in the world. in south korea, in the early 1980s, the state reorganized the public-sector telecommunications system by closing inefficient firms and allocating profitable segments to major chaebol like samsung and goldstar, enabling them to establish specialized chip businesses. by the early 1990s, samsung had become the world's number one producer of dynamic random access memories for pcs and workstations. in taiwan since the 1970s, the ministry of economic affairs and the state-controlled electronics research service organization have played crucial roles in developing the semiconductor industry. today, it is the fourth largest in the world, and firms within it have entered into strategic alliances with leading industry players in the west [22] . even in hong kong, where a developmental state took longer to emerge, the government is currently overseeing the construction of a flagship cyberport, intended to host a strategic cluster of companies and professional talents, specializing in it applications, information services and multimedia content creation, and designed to project a hi-tech international digital city image. the east asian tigers are also leading players in the development of e-government. the 2001 un/aspa benchmarking survey of all 190 un member states placed singapore at number 4 (a long way behind the us, but only fractionally behind australia and new zealand), south korea at number 15 and japan at number 26. all three states featured in the top category of high e-government capacity. the survey did not assess hong kong and taiwan, neither of which is a un member state. the report noted that singapore ''demonstrated a balanced and citizen-centric e-government program, while possessing the benefits of a high technological infrastructure and human capital measures''. it held that south korea ''made perhaps the most dramatic advances in its e-government program by successfully implementing several new online transaction features''. it was more critical of japan, arguing that it had ''yet to live up to its rather significant potential''. ''japan's e-government program has not yet reached a comparable level of sophistication as that of the regional leaders due primarily to achieving only a limited interactive presence among national government websites'' [23] . a january 2002 analysis of e-government in east and southeast asia reached similar conclusions, identifying the five tigers as regional leaders [24] . accenture's 2004 survey looked at only two of the five east asian jurisdictions analyzed here. it ranked singapore number 2 in the world after canada, and japan number 13 [25] . looked at from many different perspectives, then, the east asian tigers are leading participants in the emergent information age. healthcare systems in the tigers share a basic orientation, but are otherwise quite varied. the orientation is best termed productivist, in that in each society social policy has usually been subordinate to economic objectives. while the governments of all five tigers certainly get involved in social policy, they usually do so either for economic reasons or after they have made provision for their various economic goals. the main stimuli to this strong focus on economic development were, in all cases, the devastation brought by the second world war, and the uncertainties of the international order constructed thereafter [26] . this shared orientation has fed into healthcare policy in three main ways [27] . in japan and its two former colonies, south korea and taiwan, healthcare was initially left chiefly to the market. only once economic policy was on track and a measure of growth had already been attained, did these societies turn their attention to planning their healthcare systems. in doing so, they concerned themselves chiefly with healthcare finance, creating social insurance systems by gradualist means. now, in all of these societies, the health insurance scheme is universal in aspiration and near universal in fact. across all three societies, healthcare provision remains privatesector-driven, with the state performing a chiefly regulatory role. traditional medicines are significant in all three societies and covered by national health insurance schemes [28] . however, they are not consistently brought within the planning frame. in hong kong, until the early 1990s, the colonial government took a strictly reactive and incremental approach to healthcare. its major interventions focused on subventing charitable organizations in the healthcare business, though in time, it also built hospitals and delivered care directly through them. throughout, government activity was funded out of general government revenue. the major and to date, only step change came in 1991, with the formation of the hong kong hospital authority (hkha). this imposed state control and state funding on the secondary sector and gave hong kong a miniature version of the british national health service. however, there has never been any attempt to bring primary care within the planned healthcare system. only in 1999, was traditional chinese medicine subjected to anything more than minimal government regulation [29] . in singapore, the early post-war experience was similar to that of hong kong. here, however, separate initiatives were taken in the spheres of provision and funding. in 1985, much provision was integrated at the secondary care level through creation of the state-run hospital corporation of singapore. this body subsequently sought to drive private-sector disciplines into state provision through ''corporatization''. in 2000, in an attempt to generate integrated pathways of care, it was broken into two territorial clusters focused on the secondary sector but also having primary and tertiary elements. however, as most of the primary sector remained outside the state sector, the extent of integration was limited; in singapore, the state provides 80% of secondary care but only 20% of primary care. on the funding side, singapore in 1984 created a compulsory savings system, medisave, within the wider central provident fund scheme. it added the insurance schemes medishield and medishield plus in 1990 and 1994 and created a basic social safety net, medifund, in 1993. these various schemes partially fund secondary care provision. there is also some direct state subsidy. funding of primary care takes place mainly through out-of-pocket expenses. the traditional sector stands outside all state planning and, as in hong kong, has only recently been brought within the regulatory framework. these healthcare systems have enviable records. not only did they make a rapid post-war transition from the contagious disease characteristic of thirdworld countries to the chronic disease characteristic of first-world societies, but also they register very favorable health outcomes as measured by standard input and outcome indicators (table 1) . healthcare systems in the east asian tigers thus share a productivist orientation and strong performance. they exhibit varied state roles, with much healthcare activity lying outside the public sector and some of it falling beyond the planning horizon. in japan, south korea and taiwan, state involvement is extensive in finance but limited in provision. in hong kong, the government both funds and directly provides care in the secondary sector, but not elsewhere. in singapore, the state provides a large amount of secondary and some primary care. the funding regime is complex, comprising direct state subsidy, forced individual saving, state-run and private-sector insurance, and out-of-pocket expense. in all five tigers, both the public and private sectors play important roles and face clear incentives to take an interest in harnessing the internet for healthcare gain. note: taiwan data are from 1999. sources: [34] . against the dual backdrop of sophisticated it societies that make extensive use of the internet and cost-effective healthcare systems driven in variable ways by actors from the public and private sectors, we now turn to a survey of e-health in the east asian tigers. to frame the survey, we begin by providing a brief descriptive overview of the major state-run healthcare websites in the region. we then structure our analysis using the five main analytical spheres that dominate the existing e-health literature: policymaking, regulation, provision, funding and physician-patient relations. all ministries or departments of health in the east asian tigers have their own website. throughout the region, the major quasi-autonomous state agencies, such as the national health insurance agencies in japan, south korea and taiwan, the hkha in hong kong and the two big healthcare clusters in singapore, also have sites. here, we look only at the main government healthcare sites ( table 2) . the overall quality is high. all have clickable links to organizational objectives and tasks. most also offer detailed information about subsidiary divisions. all contain links to the government homepage and related healthcare sites so that visitors can conduct further searches and collect additional information. all provide feedback channels. in singapore, the ministry of health (moh) offers online feedback opportunities. in taiwan, citizens can make online appointments with the director of the department of health (doh). in japan, the ministry of health, labour and welfare (mhlw) uses e-mail to solicit however, within this generally strong showing, there are also significant differences, with japan's mhlw and to a lesser extent, hong kong's hwfb lagging behind their regional counterparts in key respects. firstly, the mhlw fails to provide contact details for named officials on its website. this is standard practice in the other four tigers. singapore's moh, for example, gives address, telephone number and e-mail details for key officials. secondly, while healthcare professionals and officials in singapore, south korea and taiwan can communicate with each other through the internet, their counterparts in japan and hong kong cannot. thirdly, the range of options available to users is more restricted in japan and hong kong than in the other three tigers. in south korea, for instance, it has played a role in the surveillance system for communicable disease since 1999. through electronic data interchange and regional database management systems, notifying and reporting systems have been computerized, and an electronic record of all notified and reported cases is kept. using the super-highway communication network, physicians and public health centers can access the notifying and reporting system, disweb, anywhere and anytime through the internet (http://dis.mohw.go.kr). in singapore, the moh site within the government's ecitizen portal enables healthcare professionals to download application forms for license renewal, approval to perform a pregnancy termination, and so on. the policymaking strand of the e-health literature castigates us policymakers for being slow to grasp the potential of the internet. such a charge is less easy to sustain in the east asian tigers, though again experience is variable. singapore and taiwan are the regional leaders. singapore's ecitizen portal addresses many aspects of citizen interaction with government, with healthcare being a prominent theme. the internet is used to reinforce the public health messages that have been disseminated by the singaporean government through other media for many years. behind the scenes, e-mail links pervade the healthcare system and enhance the cohesiveness of policy networks. in a controlled city state, those networks are in any case very tight. in taiwan, the doh in 2002 launched an ambitious e-health project, with a timeline stretching to 2006. the health information network that is central to this initiative has a backbone funded by central government and permits local users in both the public and private sectors to participate on a self-paying basis. drawing on us experience, it seeks to promote electronic medical records, based on a smart card system, so that information can flow to all parts of the healthcare sector. a healthcare certification authority, created in 2002, oversees promotion of this initiative. in the other three tigers, progress is less impressive. japan launched an e-japan strategy in january 2001, designed to make it ''the world's most advanced it nation within 5 years'' [30] . the strategy had an explicit e-government strand. in september 2001, the mhlw followed up by issuing a ''grand design'' for promotion of it in the healthcare sector. the aim was to computerize the entire sector by 2004 and to introduce an electronic medical record system covering 60% of clinics and 60% of hospitals with 400plus beds by 2006. progress towards targets appears to be on track. however, japanese performance in the e-health domain is poor by regional standards. hong kong is also quite slow to place healthcare online. the hwfb site contains standard bureaucratic information, such as current policy initiatives and recent speeches, plus public health information that has been developed particularly since the 2003 sars crisis. here, the major networking initiative is being taken by the dominant public-sector delivery agency, the hkha. while its primary focus is provision, the networking links being created among hospitals are likely to have policy consequences. as in singapore, e-mail links also bolster ties within policy networks that are already quite cohesive. south korea is making an aggressive attempt to exploit the internet across all areas of government, but in the healthcare sphere, currently remains an average performer. turning to regulation, three main issues are raised in the literature. the first is that e-health generates a number of regulatory problems. the second is that excessive regulation may impede e-health progress. the third is that the courts are likely to have to step in when administrative regulation fails. in the east asian tigers, regulation is clearly a major concern and an evident constraint on ehealth development, often for good reason. one instance is limitations placed on consultations, which in all five tigers quite properly mandate face-toface physician-patient contact before any specific healthcare information or advice can be given. for the foreseeable future, online consultation, though technically feasible, is likely to be restricted by professional concerns. another instance is limitations placed on information sharing and exchange, which in all the tigers are again very properly restricted by privacy considerations. however, there is some variation in regional regulatory practice. in singapore, patients requiring repeat prescriptions can place an order online and have the medications delivered to their homes. only after 6 months, do they have to return to the healthcare system to consult a physician. elsewhere, this practice is illegal. in japan, physicians are prohibited from answering specific questions about healthcare or disease by e-mail or telephone. regarding provision, assessments in the us literature are mainly negative. on the one hand, the argument is made that it cannot be expected to solve structural problems in healthcare systems. on the other, barriers even to less ambitious networking initiatives are held to be substantial. these are fair points, but they should not be allowed to obscure the real progress being made by healthcare systems around the world, and in our case in east asia. among the five tigers, taiwan's healthcare websites, both public and private, provide the most comprehensive services to patients. singapore ranks second, and hong kong third. japan and south korea are somewhat behind the regional pace. an overview is given in table 3 . in taiwan, the doh operates a taiwan e-hospital site to provide free online medical advice to patients (http://taiwanedoctor.doh.gov.tw/). currently, 237 medical practitioners and 11 nutritionists from 31 public hospitals form a consulting team to answer questions about 29 specialties. patients seeking general medical advice can send questions to a particular practitioner and receive feedback online or by e-mail. in the private sector, a number of hospitals, such as the chang gung memorial hospital, have online question-and-answer services for patients. the kingnet second opinion webhospital (www.webhospital.org.tw) and the taiwan physician's net (www.doctor.com.tw) are two prominent sites providing free online medical advice to patients. established by kingnet entertainment (www.kingnet.com.tw) in 1998, the webhospital has some 200 voluntary physicians answering questions from the public. the taiwan physician's net brings together about 1500 physicians, whose information and advice are posted on the web. apart from getting online medical advice, patients can search for a particular physician and visit his or her office for treatment. in taiwan, patients can also make medical appointments online with many public and private hospitals. looking to the future, the doh is planning to develop a medical information exchange center to promote information sharing and enhance treatment quality. in singapore, health is one of a number of cluster points within the ecitizen site. to date, the internet is mainly used to provide general healthcare information, with the healthcare portal containing comprehensive information about healthcare providers, the healthcare establishment, healthy lifestyles and public health issues such as sars. many searches are possible. the site also allows individuals to submit complaints and feedback. only a few transactions can be undertaken online. as in taiwan, appointments can be made and altered online. through singapore's e-pharmacy services, recurrent prescription items can be ordered online and delivered throughout the island. in one of its two main healthcare clusters, patients can register online and access summary medical records. inside the healthcare system, information flows are starting to change as polyclinics and gps gain access to hospital records online. the likelihood is that enhanced integration of the public and private sectors will result. in hong kong, the hkha, which oversees almost the entire secondary sector, is currently introducing online networking in hospitals. its clinical management system is an integrated clinical workstation giving clinicians access to departmental information and patient records. it will soon develop into a longitudinal electronic patient record within the public hospital system, enabling records to be accessed by many parties simultaneously anywhere, anytime. the system will also actively support clinical decisions by offering alerts, reminders, links to medical knowledge and other aids. it is expected to play an important role in reducing medical errors and improving the quality of patient care. over the next 5 years, the hkha is planning to create a hong kong health information infrastructure, with the aim of networking all healthcare providers in the public, private and social welfare sectors. it also intends to build an electronic medical record for every hong kong resident and provide citizens with an electronic gateway to healthcare information and evidence-based medicine [31] . these initia-tives are likely to enhance information flows within the public healthcare system. compared with taiwan and singapore, however, hong kong lags behind in developing internet services for patients. individuals cannot register and access summary medical records online. lacking an e-pharmacy service, the hong kong system does not allow recurrent prescription items to be ordered online. japan and south korea are falling behind their regional counterparts in providing online health services to patients. their official health websites do not deliver any electronic service to individual patients. with the exception of initiatives taken by a small number of private hospitals in south korea, like the yonsei eye and ent hospital, neither public nor private hospitals in these two tigers allow patients to register online. however, in 2001, japan's mhlw established telemedicine networks to provide specialized care to people in remote areas. the government will provide us$4 million a year to form networks consisting of one large hospital and three clinics working together to supervise patients. each patient will be equipped at home with a computer that can monitor heart rate, blood pressure and other indicators, as well as a phone capable of transmitting video. they will be linked to physicians through an isdn digital phone connection, thus enabling physicians to diagnose illness by electronically transmitted data. from june 2001, the mhlw started to establish 10 such networks a year, so that all 47 districts will have at least one by 2006 [32] . in 2000, south korea's semipublic seoul national university hospital founded ezhospital, which is business-oriented instead of patient-oriented. with three main business elements, education (content services), e-trading and system integration, ezhospital is starting to alter purchasing arrangements for both medical and non-medical supplies. as the south korean system is highly fragmented, the purchasing consortia that can be built through the internet could one day become significant. at present, however, e-purchasing is at an early stage of development. analyses of e-health funding focus on one main issue, the short-termism of us initiatives. in this domain, it is difficult to reach an overall assessment of the tigers' performance. on the one hand, their developmental state orientations make the general climate for it industrial emergence very different from the climate found in the us. in this regard, the tigers look to the long term in a systematic fashion that has no us equivalent. on the other hand, it is hard to find evidence that the tigers are investing heavily in e-health applications. moreover, because the private sector plays such a large regional role in healthcare, as it does in the us, many of the relevant initiatives fall outside the state sector and are hard to capture. there are undoubtedly many small commercial initiatives in east asia as, again, there are in the us. furthermore, like other commercial websites, private healthcare sites throughout the region rely heavily on advertising and sale of products for income. to take just two taiwanese instances, the kingnet webhospital and the taiwan physician's net offer online sales not only of healthrelated products, but also of cinema tickets. the very fragmented nature of private-sector healthcare operations throughout the tigers means that few summary assessments can be made. looking finally at physician-patient relations, the existing literature contains variable forecasts of unpredictable change, little change, and so on. however, there is a clear belief that patients have most to gain from e-health and physicians correspondingly have most to lose. in general, physicians in the tigers have tended to be wary of exploiting the internet for patient interactions. this partly reflects the tight regulatory climate in which many find themselves, with many modes of physician-patient contact outlawed. it may also reflect a certain reluctance on the part of both physicians and patients to engage in the informalities of online contact. until recently, then, the emergence of virtual physician-patient relations was highly limited. since the spring 2003 sars crisis, however, the pattern may have started to change. although it is too early to register the longterm impact of the crisis, it is clear that during the sars outbreak, many individuals sought to shift to online interactions with healthcare professionals. the fear of visiting surgeries and, in particular, hospitals that gripped the region in 2003 has certainly not disappeared and seems likely to provide a lasting stimulus to virtual delivery of healthcare. furthermore, the generic healthcare information found in great abundance on english-language websites is paralleled on regional websites operating in chinese, japanese and korean. there is also some official encouragement for patients to migrate to e-health. in may 2004, hong-jen chang, ceo and president of taiwan's bureau of national health insurance, argued at an oecd forum that e-health could make a major contribution in informing patients. as evidence, he cited taiwanese experience in confronting hiv/aids and the role of the internet in educating patients about the disease. in the long run, he contended, patients equipped with information gained from online searches ''will translate into quality improvement and efficiency gains for the system'' [33] . overall, east asian societies retain many traditional features, which generate some resistance to change in established modes of physician-patient contact. nevertheless, there are also factors operating in the opposite direction. one long-term impact of the sars crisis seems likely to be heightened caution about visiting healthcare facilities, for fear of contracting infectious disease, and a consequent boost for e-health. the east asian tigers form the most wired cluster of societies found anywhere in the world. moreover, they have long had a developmentalist orientation that has seen their states become involved in many aspects of economic and social development. in the sphere of e-health, however, their performance is strong at the level of basic web provision, but otherwise not particularly advanced. on the whole, their health ministries or departments have good sites covering all the fundamentals of online provision. outside central government agencies, they often have a wealth of additional sites in the public and private sectors. beyond that, they do not make pioneering use of the internet in healthcare. there are many possible reasons for this slightly disappointing performance, some of which apply to all of the tigers and others which are specific to a particular society. in japan, the structural problems that mired the economy in stagnation for more than a decade from the early 1990s also form part of the explanation for its sluggish e-health performance. a notable feature of the japanese healthcare system is the considerable power of the japan medical association and its extensive links to the liberal democratic party that has governed the country for almost all of the post-war period. in hong kong, the 1997 sovereignty transfer was quite disruptive, and only several years on is the political system taking a settled shape on the developmental state model. looking beyond the specific circumstances of individual tigers, however, the major explanatory factors appear to be institutional, cultural and financial. institutionally, east asian healthcare systems tend to be highly fragmented, notably in japan, south korea and taiwan. in consequence, policymakers in healthcare ministries and departments have rather few levers that they can use to direct change. in the e-health sphere, they can quite easily construct official government websites, but generating reform in the wider healthcare system is more difficult and depends on their success in building consortia of interest among many private-sector actors. in part, they seek to do this by offering ring-fenced seed money for specified development projects. in part, they resort to exhortation, calling on all members of society to engage in the project of securing and maintaining regional and/or global leadership in the information age. in these many respects, the east asian tigers have a great deal in common with the us. in the additional domain of culture, they differ from the us. while capitalism is certainly a dynamic force in east asia as in north america, it also co-exists with still vibrant cultural underpinnings. the confucian heritage that characterizes all five east asian tigers has many complex strands. among them is considerable respect for authority, hierarchy, status and so on. in the medical sphere, one consequence is that doctors tend still to be accorded considerable professional status. this may make it difficult for full commercialization to take place and for the market drive that characterizes ehealth in the us to work its way through the system. finally, the financial dimensions of healthcare in the east asian tigers should not be overlooked. these are healthcare systems that deliver the excellent outcomes already mentioned at a fraction of the cost registered in the us and, indeed, in most developed societies. as a proportion of gdp, east asian tigers spend between 3 and 7% on healthcare, with most coming in at around 5%. this is far below the us figure of 13-14%, and also below the highincome country standard of almost 10%. one result of the tigers' success in holding down healthcare costs is that the incentive to experiment with new initiatives is reduced. clearly, there still are some incentives, but they are not as strong as in the us. e-health in the east asian tigers remains at an early stage of development. all have attained a good basic standard, but few are engaged in pathbreaking initiatives. alongside institutional factors that are similar to those found in the us, cultural and financial factors help to explain this rather unsatisfactory level of performance. doctors in a wired world: can professionalism survive connectivity? milbank q the internet promise, the policy reality the information age: economy, society and culture. vol. ii. the power of identity the information age: economy, society and culture. vol. i. the rise of the network society the information age: economy, society and culture. vol. iii. end of millennium how will the internet change our health system? ehealth: technologic revolution meets regulatory constraint patients, physicians and the internet com: the failed promise of the healthcare internet networking health: learning from others, taking the lead financing the healthcare internet rethinking communication in the e-health era consumers of e-health: patterns of use and barriers the impact of cyberhealthcare on the physician-patient relationship e-health: transforming the physician/patient relationship health care web sites: are they reliable? internet healthcare coalition, e-health quality partners named exclusive education and outreach affiliate of the internet healthcare coalition physicians get on line, aspen publishers doctor-patient e-mail slow to develop, international herald tribune nielsen//netratings, internet provided vital information and alternative access to shopping, banking and education for people in hong kong as sars took hold online shopping and banking sites soared in popularity as people in hong kong shunned the crowds sars stimulates ongoing growth in internet usage in hong kong divided sun: miti and the breakdown of japanese high-tech industrial policy tiger technology: the creation of a semiconductor industry in east asia united nations/american society for public administration building e-government in east and southeast asia: regional rhetoric and national inaction high performance, maximum value productivist welfare capitalism: social policy in east asia welfare capitalism in east asia: social policy in the tiger economies traditional medicines in modern societies: an exploration of integrationist options through east asian experience agenda-setting for the regulation of traditional chinese medicine in hong kong networking health: dawning of the e-health era. paper presented to apami-mic conference 2000 at the hong kong convention and exhibition centre e-health and the informed patient, paper presented to oecd forum taiwan council of economic planning and development, taiwan statistical data book world development indicators the work described in this article was substantially supported by a grant from the research grants council of the hong kong special administrative region, china [project no. cityu 1199/03h]. initial seed funding was provided by the governance in asia research centre, city university of hong kong.we are grateful for the research support we received. we thank academics, officials and practitioners in east asia for talking to us about e-health. the usual disclaimer applies. key: cord-000266-xwfptmmv authors: liao, qiuyan; cowling, benjamin; lam, wing tak; ng, man wai; fielding, richard title: situational awareness and health protective responses to pandemic influenza a (h1n1) in hong kong: a cross-sectional study date: 2010-10-12 journal: plos one doi: 10.1371/journal.pone.0013350 sha: doc_id: 266 cord_uid: xwfptmmv background: whether information sources influence health protective behaviours during influenza pandemics or other emerging infectious disease epidemics is uncertain. methodology: data from cross-sectional telephone interviews of 1,001 hong kong adults in june, 2009 were tested against theory and data-derived hypothesized associations between trust in (formal/informal) information, understanding, self-efficacy, perceived susceptibility and worry, and hand hygiene and social distancing using structural equation modelling with multigroup comparisons. principal findings: trust in formal (government/media) information about influenza was associated with greater reported understanding of a/h1n1 cause (β = 0.36) and a/h1n1 prevention self-efficacy (β = 0.25), which in turn were associated with more hand hygiene (β = 0.19 and β = 0.23, respectively). trust in informal (interpersonal) information was negatively associated with perceived personal a/h1n1 susceptibility (β = −0.21), which was negatively associated with perceived self-efficacy (β = −0.42) but positively associated with influenza worry (β = 0.44). trust in informal information was positively associated with influenza worry (β = 0.16) which was in turn associated with greater social distancing (β = 0.36). multigroup comparisons showed gender differences regarding paths from trust in formal information to understanding of a/h1n1 cause, trust in informal information to understanding of a/h1n1 cause, and understanding of a/h1n1 cause to perceived self-efficacy. conclusions/significance: trust in government/media information was more strongly associated with greater self-efficacy and handwashing, whereas trust in informal information was strongly associated with perceived health threat and avoidance behaviour. risk communication should consider the effect of gender differences. pandemic influenza a/h1n1 has a clinical profile similar to seasonal influenza, despite initially appearing more severe [1] . respiratory infectious diseases (rids) such as influenza are a major public health issue best dealt with by prevention, ideally vaccination. however, in the first six-months or so of a newlyemergent rid epidemic/pandemic vaccines are generally unavailable and non-pharmacological interventions can play a major role in minimizing rid spread [2] [3] [4] . government health education messages are a major source of information for promoting self-protective practices against rids. these preventive messages generally emphasize improved hygiene, face-mask use by infected persons, and social distancing measures, including avoiding crowds during epidemics [5] [6] [7] . predictors of population uptake of health protective behaviours in rid epidemics have begun to be studied [8] [9] [10] [11] [12] [13] , yet related theory remains nascent and this is problematic: to effectively predict behaviour during future epidemics robust theory is critical. effective models that enable comprehensive prediction of health protective behaviours remain limited mainly to two overlapping theoretical paradigms: the theories of reasoned action/planned behaviour (tpb) [14] [15] [16] and bandura's concept of self-efficacy [17] [18] [19] (the belief that one can successfully execute some behaviour), particularly regarding the core tpb concept of perceived behavioural control, which controversially is claimed by some to be largely synonymous with self-efficacy [19] [20] [21] and by others to be indistinguishable from intent [22] (the intention to execute a particular behaviour), the key predictive element of tpb [16] . when used to account for health-related behaviours tpbbased models typically account for ,35% of variance in outcomes [16] , while self-efficacy accounts for ,25% of variance in outcomes [23, 24] . however, neither tpb nor self-efficacy allow for the social and affective influences that might be expected logically to be important in rid [25, 26] . we report on a theoretical model that incorporated elements of influenza causal knowledge, perceived self-efficacy and also social and affective influences ( figure 1 ) because these latter variables have been less frequently studied in combination, but have theoretical and logical support for their potential importance in the context of rids. we tested this model against data collected in the early phase of the influenza a/h1n1 pandemic (table s1 ) to examine how levels of trust in formal and informal sources of risk/prevention information associated with hand washing and social distancing. ethics approval was obtained from the institutional review board of the university of hong kong/hospital authority hong kong west cluster. for this telephone interview, written informed consent was waived by the irb but verbal consent was required from all the respondents and agreement to participate in the interview was taken as further consent. before the interview began, a brief introduction about the study aims and interview contents was given and then respondents were asked whether the interview could start. if approval was received this was recorded and the interview performed. if not, respondents were thanked and the call was terminated. more than 98% of hong kong households have landline telephones and all local calls are free. random-digit dialled telephone numbers and within-household random-sampling grids (kish grids) are a cost-effective way to survey highly representative random population samples. kish grids are matrices containing random numbers for different sized households that facilitate random selection of individuals within households and help minimize sampling bias. the number of eligible household residents, ''n'', is determined by asking the person of first contact in the household. the kish grid provides a randomly generated number ''k'' between 1 and ''n'' which is used by the interviewer. ordering by age and starting from the oldest eligible member in the household, the k'th member is then invited to participate in the survey. different grid values are used for each household. as part of a series of surveys to monitor a/h1n1 epidemic activity, a commercial polling organization administered the questionnaire using this telephone-survey methodology, targeting 1,000-1,500 participants on each occasion, a sample size calculated to give an estimate of a/h1n1 health protective behaviours with a precision of 63%. the survey with the largest sample was selected for this analysis. sampling was performed during the evening to minimize exclusion of young working adults. data on attitudes, knowledge, situational awareness, risk perception and preventive behaviours (table s1) were collected by household telephone interviews, based on random digit dialling. one cantonese-speaking adult (age$18) who lives .4 nights per week in each household was selected using a kish grid. all interviews were conducted between 8:30pm-10:45pm from 23 rd -25 th june, 2009, two weeks after the first community transmission had been identified in hong kong. existing theoretical frameworks of behaviour change have been adapted to predict health-related behaviour-change for chronic, non-communicable diseases [15, 16] , but we lack a comprehensive evidence-based model of protective behaviour against rid threat [11] . a recent review of 26 papers on rid prevention behaviours concluded that 23 lacked a theoretical basis [13] . existing applications of health behaviour change models in communicable disease are almost exclusively limited to hiv/aids research [24, 27] and to a lesser extent hepatitis b and c, which share the same transmission pathways as hiv. there are good reasons why sexually-transmitted diseases embody a different set of influences than do rids. for example people are highly motivated to seek sexual contact (or injection drug use) and have a high degree of potential control (e.g. condom use) over the nature of these encounters, even though they may be situationally constrained from executing that control, and are infected only by direct exchange of bodily fluids. in contrast, one can acquire an rid transmitted by air droplets, hand contact or fomites for up to 72 hours after the person who is the source departs [28] , or immediately by being sneezed on. infection is much more casual. clearly, the controllability of rids requires different behavioural imperatives to those in stds and hence different psychological influences should be considered. attempts by the tpb to accommodate social influences had relied on incorporating social norms [14] , the behavioural expectations within a group. however, norms, and hence theoretical models reliant on norms to account for social processes, cannot accommodate the fact that communicable respiratory diseases make other humans ambiguous sources of threat: one can usually control sexual encounters but not who shares public transport. in this respect social factors in communicable respiratory disease differ significantly from those in non-communicable diseases and warrant greater consideration than existing hbc models allow. outbreaks of new infectious diseases constitute situations that are uncertain, dynamic, and embody highly personal threat, requiring rapid decisions on appropriate action [29] . under such circumstances timely and relevant information on the best preventive actions become critical to such decision-making. hence, health protective behaviour during the early stages of a novel epidemic would be more likely to resemble situational reactions using established or known default actions such as avoiding crowds (social distancing), rather than intention-based planning before any behavioural change, such as deciding to consult a doctor to administer a vaccination. later in the epidemic as threat familiarity increases, different factors such as planned behaviour may become important. reporting delays, uncertainty and other biases affect publicly available information on the characteristics of newly-emergent communicable diseases, such as a/h1n1 lay knowledge of infection-related risks can be limited. the resulting uncertainty about disease severity and transmissibility at the epidemic onset extends to the utility and timing of adopting preventive measures. information cues to individuals about initiating protective action must therefore be synthesized from various sources. perceived information reliability or trustworthiness influences decisions to utilize any given information source [30] to inform awareness of the situation. more trustworthy sources are therefore likely to be more influential. epidemic situational awareness is likely derived from formally-announced public information like news items, government press releases and health education messages, and also from informal, social sources [25, 29] ; observation of other peoples' behaviour and communications from family, peers and neighbours. noting how others behave informs action decisions in the observer [19] . if those around you are wearing masks, this indicates others might have knowledge you do not possess, and that the threat level might be locally high and imminent, suggesting prudent precautionary or rid preventive behaviour. observers are also subject to social conformity influences that can help adoption of group patterns of behaviour. maintaining situational awareness, involving elements of perception, comprehension and prediction [31] , during epidemics probably relies on these two types of information. however, when uncertainty is high and widespread, or when there is low confidence in social and other information sources then individuals' hpbs might be expected to be more independent of formal and informal information sources. perceived risk is influenced by several stimulus characteristics, including unfamiliarity, invisibility, dreadfulness and inequity [32] , and by recipient characteristics, including demographics and trust in information source and content [33] . perceived risk is an important determinant of protective behavioural responses [12, 34, 35, 36] , but is subject to optimistic bias, where for example people distort their risk of contracting influenza downwards relative to others [35, 37] . nonetheless, susceptibility to risk remains an important measure in understanding variation in behavioural responses to threat and reflects the key element of perceived risk in an epidemic/pandemic situation. worry is a cognitive process linked to anxiety [26, 38] and reflects negative affectivity, interacting with perception of susceptibility to risk [26, 39] and may also influence rid protective responses such as social distancing [13] . because data were collected using telephone interviews we had to adapt measures to suit a brief format in order to avoid people hanging up mid-way or providing invalid answers to hurry the interview, a problem encountered with this data collection method. we therefore used parsimonious measure to minimize assessment fatigue and low response rates which threaten representativeness. trust in government/media (formal) information: we asked about respondents' agreement with three statements (table s1 ). responses were made on categorical five-point scales ranging from ''strongly disagree'' to ''strongly agree''. scalability of these three items was assessed using cronbach's alpha, which at 0.61 indicated that the internal consistency between items was low, but acceptable. however, to minimize potential measurement error arising from the low internal consistency, this construct was treated as a latent variable in the subsequent analysis [40] . a latent variable is a concept opposed to an observed variable. a latent variable can not be measured directly but is inferred from one or more variables that are directly measured (observed variable) while an observed variable can be directly measured with a specific question or item or observed by the researchers. for example, an ''attitude'' is a concept that is difficult to measure directly with single items but can be inferred from various questions asking about different aspects of that attitude. then within the analysis ''attitude'' is treated as the latent variable while the questions used to infer it are the observed variables. trust in interpersonal (informal) information: respondents' agreement with two statements (table s1 ). responses were made on categorical five-point scales ranging from ''strongly disagree'' to ''strongly agree''. scalability of these two items was assessed using cronbach's alpha, which at 0.50 indicated that scalabilty was unsuitably low for two items. this suggests that these two items measure different aspects of social information. again to minimize potential measurement error this construct was treated as a latent variable in the subsequent analysis. understanding cause of a/h1n1 (''i understand how swine flu is caused'') and self-efficacy (confidence in one's ability to act in a way that achieves desired future outcomes) for a/h1n1 prevention (''i am confident that i can protect myself against swine flu''): each was assessed using responses on 5-point scales of agreement with these two single item statements (table s1) . perceived personal susceptibility: two items, one assessing absolute susceptibility (perceived absolute probability of developing a/h1n1) and another assessing relative susceptibility (perceived probability of developing a/h1n1 relative to peers) formed a latent variable for perceived personal susceptibility (table s1 ). the cronbach alpha of these two items was 0.66. worry about contracting h1n1. respondents were asked to indicate their level of worry over the past one week about contracting influenza a/h1n1. responses were 5-point scales of worry ranged from ''never thought about it'' to ''extremely worried'' (table s1 ). hand hygiene. respondents were asked to indicate frequencies of use of four hand hygiene practices over the three days prior to interview: hand washing after sneezing, coughing and touching nose; hand washing after returning home, use of liquid soap for hand washing, and hand washing after touching common objects. responses were on a 4-point scale of frequency: 1 ''never'', 2 ''sometimes'', 3 ''usually'' and 4 ''always''. cronbach's a was 0.62 (table s1 ). social distancing behaviours: a. social avoidance. respondents were asked to indicate if they had adopted any of four avoidance behaviours due to influenza a/h1n1 in the past 7 days: avoiding eating out, avoiding using public transport, avoiding going to crowded places, and rescheduling travel plans responses were coded as 1 ''yes'' and 0 ''no''. cronbach's a was 0.61 (table s1 ). we first compared the demographic structure of the sample against that of the general population derived from the hong kong government general household survey to identify any sample differences. our model proposes that trust in formal (government and media sources) and informal (from other people) information affects rid epidemic health protective behaviours, the former by informing about generic risk and response characteristics for dealing with a potential threat (causes and protective responses), the latter about threat imminence, severity and response effectiveness (seeing how others behave). we refer to the product of these combined processes as situational awareness, and propose that rather than driving behaviour directly information acts through altering the cognitive/affective domain of situational awareness. thus the model is predicated on several premises: that understanding of the disease and perceived personal susceptibility influence self-efficacy [17, 18, 31] ; that the effect of perceived susceptibility to influenza on hpbs acts through increasing worry about the disease [26, 33, 38, 41, 42] ; and that more worry from perceived susceptibility prompts hpbs [39, 41, 42] . these cognitive/affective processes are represented in the hypothesized model ( figure 1 ). structural equation modeling (sem) is a method for simulating and testing multiple and interrelated causal relationships simultaneously in statistical data, making it suitable for theory development and testing [40] . sem was applied to test the hypothesized model. sem is usually performed when a model contains latent variables assessed with specified measurement models. despite including estimations of a series of multiple regression equations, sem differs from regression analysis in several ways, which make it advantageous for this kind of analysis. first, sem is usually theoretically based because it is performed after researchers specify the hypothesized model. second, it can be used to refine the hypothesized model by estimating the measurement model and structural model simultaneously. finally sem analysis can accommodate measurement errors of the constructs in the model [40] . in our hypothesized model, trust in formal information, trust in informal information, perceived personal susceptibility, hand washing and social distancing behaviours were entered as latent (inferred) variables while other constructs were entered as observable (directly measured) variables because they were assessed with only one item. two different health protective behaviors, hand washing and social distancing, were entered as the hpb outcomes because we hypothesized that different influences may act on each of these. we assumed that the ''disturbances'' of the two health behavior outcomes were correlated. disturbance represents the unexplained variances of the latent variables predicted by the specified independent variables [40] . in making this assumption, we assumed that unexplained variance in the outcome variables could be correlated and the variables in question jointly influenced by other unknown factors, and so allowed for such constraints within the model by using more conservative criteria. previous studies have shown that hand hygiene and social distancing behaviours during a pandemic could be influenced by some common causes which were not fully explored in our study such as current health, past experience of disease and cues to action [14] . in particular, in our study, the two kinds of health protective behaviours occurred in the same situation of the 2009 influenza pandemic, and so it is sensible and reasonable to assume that they could be influenced by some common causes which were not fully explored in our studies. adequacy of the measurement models was tested before testing the full structural model. to test the full structural model, all constructs ( figure 1) were entered into the model and all factor loading, specified paths, covariance, measurement errors and disturbances were estimated simultaneously. since the model contained categorical variables, weighted least square with mean-and variance-adjusted estimation (wlsmv) was used to estimate the standardized parameter (b) for each path [43] . with this kind of estimation, chi-square difference testing is inappropriate. we therefore used the comparative fit index (cfi), tucker-lewis index (tli) and root mean squared error of association (rmsea) to evaluate the model fit to the data. a cfi.0.95, tli.0.95 and rmsea,0.05 indicate a good fit of data to the model [43] . the analysis was conducted in mplus 6.0 for windows [43] . the proportion of missing values ranged from 0.1% for ''in the past one week, have you ever worried about catching influenza a/h1n1'' to 10.1% ''did you wash hands after sneezing, coughing or touching nose in the past 3 days''. missing data were handled with multiple imputation to generate 10 datasets which were summarized into one for subsequent analysis. multiple imputation was performed in ameliaview [44] . responses are likely to differ by sociodemographic factors [13] . we therefore stratified the sample by gender and by age (,45 years old vs. .45 years old). education is also likely to have a significant effect but there are difficulties in education stratification in hong kong. the age cut-off of 45 years was adopted to account for the introduction in hong kong of 6-year compulsory education in 1971 and 9-year compulsory education in 1978 [45] . this means that people aged 45 or above are much less likely to have a tertiary (college/university) level education and less secondary (high school) education than people aged ,45 years old [45] . moreover, in traditional families in china, a son (who lived with his parents after marriage) was usually more educationally-favoured over daughters (who moved to their in-laws' home on marriage) to ensure support for the parents in their old age, so males usually obtained more education than females [45] . these distinctions were somewhat evidenced by our data which showed that 98% of the respondents aged ,45 compared to 71% of the respondents aged 45 or above (x 2 = 147.69, p,0.001), and 89% of male compared to 80% of female respondents, obtained at least secondary education (x 2 = 17.05, p,0.001). since the numbers of tertiary educated respondents and primary (elementary) educated respondents were too small to produce stable models, we limited stratification to gender and age only and acknowledge that this also incorporates indefinable education and income effects. consequently, we used a multi-group sem to assess the invariance of the model (figure 1 ) across gender and age group (respondents aged 18-44 and aged 45 or above). we tried to test the model by stratifying the sample into four subgroups (female aged 18-44, female aged 45 or above, male aged 18-44 and male aged 45 or above). however, the sample size for males aged 18-44 was relative small (table s2) . moreover, all the model variables were treated as categorical variables and we used the wlsmv method to estimate the model. this method requires that each subsample covers all the categories of each variable. in the case of one category, younger males, not all variable values were present. to meet the assumptions for analysis we would need to recode all variables, intrinsically altering the model. in order to avoid this, we relinquished a combined four-group comparison and instead compared the model across gender and the two age groups separately. to perform multigroup comparison we first ran a model with all parameters unconstrained. we then identified factor loadings that were not significantly different (p$0.05) and set these as equal, while loadings that were significantly different were allowed to vary, and finally paths that did not differ significantly were constrained to be equal while those that differed significantly were allowed to vary and estimated separately by groups. the ''difftest'' option in mplus 6.0 was used to obtain a correct chi-square difference test for the wlsmv estimators and was used to estimate the differences between the least constrained model (with all the paths freely estimated) and the most constrained model (with all the paths constrained to be equal) as well as the partially constrained model (with some of the paths freely estimated and others constrained to be equal) [43] . a p-value.0.05 for the ''difftest'' indicate a nonsignificant difference between the models. finally, to help interpret these multigroup sem comparisons, we performed a post-hoc examination of the model variable means for different gender and age groups and tested differences using the mann-whitney test, which tests differences between two groups on ordinal scales of measurements. a total of 1,001/1,449 (69.1% response rate) hong kong adults successfully completed the interview. the characteristics of the sample were compared against the hong kong 2006 by-census population data [46] , showing respondents to be better educated and more likely to have been born in hong kong compared to the general population (table 1 ) but otherwise representative. both formal and informal information trust were correlated with all situational awareness variables except worry about contracting a/h1n1 (''worry''), while formal information trust was also independent of perceived personal susceptibility (''susceptibility''). in turn, understanding of h1n1 cause (''understanding'') and perceived self-efficacy (''self-efficacy'') were significantly associated with hand washing while worry and susceptibility were significantly associated with social distancing (table s3 ). the sem model fitted well to the data with cfi = 0.977, tli = 0.969 and rmsea = 0.026. standardized coefficients indicated two primary features in the model; the first one linking formal information and hand hygiene and a second linking informal information and social distancing ( figure 2 ). paths were seen via formal information trust and self-efficacy (b = 0.25) and self-efficacy and hand hygiene (b = 0.23), and via formal information trust and understanding (b = 0.36), and understanding and hand hygiene (b = 0.19) while understanding and selfefficacy were independent. these associations formed the first feature. marginal associations between worry and hand hygiene and between self-efficacy and social distancing were seen, but the small standardized coefficients of b = 0.13 suggest that these paths are minor. susceptibility and worry were associated, but otherwise were functionally independent, both upstream from formal information trust, and downstream from hand hygiene. the second feature of the model is reflected in a different set of paths associating informal information trust with social distancing. trust in informal information sources was inversely associated with susceptibility (b = 20.21), which was associated positively with worry (b = 0.44), and inversely with self-efficacy (b = 20.42). however, more confidence in informal information sources was associated with more worry (b = 0.16) and finally, only worry was associated with social distancing (b = 0.36). trust in informal information was independent of understanding and self-efficacy. the only remaining notable feature of the model was a strong inverse association (b = 20.42) between susceptibility and selfefficacy. this suggests some interaction between these two variables that could strongly influence both sets of paths mentioned so far. overall, the model explained 11.3% of the variance in hand hygiene and 16.1% of the variance in social distancing behaviors. across gender, both the least constrained model and the most constrained models fit the data well with cfi.0.970, tli$0.970, rmsea = 0.025. the most constrained model did not differ significantly from the least constrained model (x 2 for ''difft-est'' = 29.30, d f = 19, p = 0.061). however, three sets of associations differed significantly between females and males: those between formal information trust and understanding, from informal information trust to understanding, and from understanding to self-efficacy. these paths were set free and estimated separately in female and male. the model with these paths freely estimated fit well to the data with cfi = 0.978, tli = 0.976 and rmsea = 0.023, and did not differ significantly from the least constrained model (x 2 for ''difftest'' = 15.07, d f = 16, p = 0.519). figure 3 presents the results of multigroup comparison of the model applied to males and females with the three path parameters unconstrained. for a given path, if the path coefficients did not differ significantly between males and females, only the path coefficient for males is presented; if the path coefficients differed significantly between males and females, the path coefficients for both genders are presented with the coefficients for males presented on the left of the slashes and for females presented on the right of the slashes. by comparison, the model shows that for both genders while the association between formal information trust and understanding was positive this association was stronger amongst females (b = 0.50) than males (b = 0.25); the association between informal information trust and understanding was weakly positive in males (b = 0.12) but weakly negative in females (b = 20.14), and; the association between understanding and self-efficacy was positive (b = 0.12) in males but non-significant in females (b = 20.01). across the two age groups, both the least constrained model and the most constrained model fit well to the data with cfi.0.960, tli$0.950, rmsea#0.030. the most constrained model did not differ significantly from the least constrained model (x 2 for ''difftest'' = 15.85, d f = 19, p = 0.667). no path was found to be significantly different between the two age groups. means and standard deviations for all model variables by gender and age group showed differences (table s4 ). all the constructs did not differ by gender except for hand hygiene and social distancing with female being more likely to wash their hands and adopt social distancing behaviours. trust in formal and informal information sources, self-efficacy, and hand hygiene significantly differed by age groups, with respondents of older age group being more likely to trust the information from both sources, perceive higher self-efficacy and wash their hands. we tested a hypothesized model of associations between trust in (formal/informal) information, situational awareness variables (causal understanding, self-efficacy, susceptibility and worry) and different types of health protective behaviours (hand hygiene and social distancing) for influenza protection. the model suggested that two different sets of influences relate trust in information to hand hygiene, and to social distancing respectively. the strongest associations observed were between susceptibility and self-efficacy neither age nor gender contributed significant variation to the association between trust in formal information and self-efficacy, and self-efficacy and hand hygiene. these findings are consistent with other studies showing self-efficacy is enhanced by procedural information [18, 19, 47, 48] and that attitudinally and actionoriented interventions are more successful in changing behaviour for communicable disease protection, such as in the case of hiv [24] . similarly, exposure to relevant media stories during the 2009 a/h1n1influenza pandemic was associated with higher efficacy beliefs regarding hygiene, which in turn was associated with greater frequency of reported tissue access and sanitising gel purchase among british people [49] . however, there is evidence that coping style interacts with the ability of procedural information to enhance self-efficacy and under circumstances of high threat, such as during sars-type epidemics where mortality is high, procedural information might be counter productive for some segments of the community who use an information avoidance (''blunting'') coping style [50] . self-efficacy was only weakly associated with social distancing. people are limited in their ability to avoid crowds in hong kong, one of the most densely populated cities on earth, despite the hong kong government recommending this in order to limit the pandemic [51] . however, the relatively mild impact of a/h1n1 meant that people saw no reason to jeopardize their economic well-being and curtail other social activities, given such a low perceived threat [49, 52] . hand washing was probably seen as sufficient protection. the association between trust in formal information and understanding of influenza cause differed by gender but not age, with females showing a stronger association. men tend to have poorer health knowledge than women [53] . we found that females were more likely to wash their hands than were males. older respondents reported significantly greater trust in formal information, marginally-significantly better understanding of influenza cause and were more likely to wash their hands. this is consistent with other studies reflecting that preventive practice is enabled by knowledge of causes [49, 54] . however, increasing knowledge is not itself sufficient to always ensure preventive behaviour [55] . in this context, understanding has an independent contribution to hand washing practice only. trust in informal information seems to be associated with less perceived susceptibility to health threat. this may reflect rational processes or cognitive bias. trusting social cues involves comparison and conformity influences, and can enhance optimistic bias (the tendency to view oneself less likely to experience negative events but more likely to experience positive events) in personal risk estimates [56] , thereby reducing perceived susceptibility. conversely, others' behavioural cues about health threat proximity can arouse motivating worry and anxiety producing protective action [17, 29] . we found trust in informal information was independent of both understanding of influenza cause and self-efficacy. however, when stratified by gender, the trust in informal information-understanding association was positive among males but negative among females. education is probably an important influence in understanding and may have a bearing on these patterns which await clarification. susceptibility was strongly associated with both self-efficacy (negatively) and worry (positively). neither worry nor susceptibility varied significantly by gender or age group. this is plausible and theoretically consistent [26, 34, 35, 39] . worry was strongly associated with social distancing, again consistent with british data [49] . although worry was also significantly associated with hand hygiene, the association was weak. elsewhere, using a generic measure of personal hygiene practices we have found a stronger association between disease worry and hygiene, suggesting a moderate effect of level of disease worry [57] . the model tested explained only a modest proportion of the variance in adoption of hbps, suggesting that there are significant theoretical gaps that remain to be filled. these await further research. social distancing is unassociated with formal hpb messages, suggesting potential susceptibility to a ''herd-like'' response in this chinese community, particularly if confidence in formal (government or doctors) information is low. voerten and colleagues describe such a pattern of response in the early stages of sars [25] . these models support the hypothesis that social distancing is more likely to occur when perceived health threat is high [25] . logically, when others seem to be behaving in a way that is informed and probably consistent then their actions provide clear information. if mixed social messages occur signalling uncertainty then the utility of social information will fall. this is likely to be associated with increase perceived susceptibility, and possibly greater worry and distancing behaviour. this pattern of responses would be most likely early in a novel rid epidemic where disease characteristics and behaviour are often uncertain. high threat uncertainty then drives social avoidance of potentially high-risk others. high levels of worry are associated with greater social distancing. around 50% of 997/14,297 (response rate 7%) british respondents agreed that social avoidance would minimize risk of a/h1n1 infection, and respondents reporting more anxiety were more likely to engage in preventive actions; severity and likelihood of infection were the most important determinants of preventive action [12] . further research on social influences on hpb during epidemic and pandemic rids is warranted. providing more knowledge about disease causes can improve hand hygiene but is unlikely to influence social avoidance, which appears less amenable to formal health messages. however, as formal messages achieve acceptance across the population, and uptake of hpbs increases, then under circumstances where a critical mass of the population are practicing precautions trust in informal information should increase, reducing susceptibility and worry and leading to declines in social avoidance. because others are likely adopting hpbs this makes them less of a contagion risk. conversely maintaining a high level of hand washing practices may require sustained public education activities. finally, different segments of the population probably communicate different types of information with their peers. self-efficacy in preventing a/h1n1 influences hand hygiene but has little influence on social distancing. formal health education messages that focus on enhancing the public's sense of their ability to protect themselves by adopting hygiene practices would seem to be the most effective to improve hand hygiene, but where the practice is already established, high levels of trust in these messages are not likely to significantly increase hand hygiene. this study is limited in being cross-sectional and relying on hypothesized modeling to infer causality. this is potentially errorprone and can only be confirmed by specific longitudinal tests of the hypotheses proposed above. there are potential limitations related to measurement imposed by the need to be parsimonious in questioning due to use of telephone interviews. where this is not done refusal rates would have been unacceptably high [12] raising serious questions about representativeness. as a consequence, construct validity for some latent variables was weaker than expected, for example, only two items were scaled to measured trust in informal information giving a low internal consistency. we re-ran the sem treating the two trust items as separate which gave almost identical associations with different situation awareness variables, so we entered their combined score as a latent variable in the final model. only one item measured self-efficacy. this is generally not considered adequate but does have precedent indicating it is valid for predicting behavioral change [9] . finally, this random sample, closely representative of the population of hong kong and collected early in the epidemic phase, nonetheless was slightly older and less-well educated than the general population. this was likely due to unavoidable sampling bias from surveying in the early evening to 10pm. many young adults do not return home from work until after this time and were thereby not sampled. the results may in part reflect this bias. otherwise the response rate was high at 69% and excellent compared to similar studies [12] . some of these above limitations may also have contributed to the low explained variance of the model. many factors influence rid protective behaviour. this study has examined a very limited number of these. confidence in formal information such as health education messages is associated with greater compliance to recommended preventive measures for influenza a/h1n1 [12] . however, the mechanisms for this were unclear. we have shown that this probably involves different mechanisms for hand washing and social distancing, and suggest how these might function. formal messages may not reduce social distancing behaviours until such time that preventive behaviours are widely adopted in the community. social distancing seems more likely to occur when there is high influenza-related worry and uncertainty, such as in the initial stages when epidemic circumstances are unknown, or if an epidemic is severe and appears poorly controlled, as during early sars. this would seem to be largely worry/affect-driven. if so, then social distancing is likely to occur irrespective of government messages as population anxiety about an epidemic increases. susceptibility may also increase and this may inhibit self-efficacy regarding hand washing. finally, high levels of community uncertainty or rumour are likely to increase distancing by exacerbating perceived susceptibility and worry. a simple version of our findings can be found it the supporting file (text s1). table s1 found at: doi:10.1371/journal.pone.0013350.s001 (0.05 mb doc) text s1 this is a simple version of our study findings for nonspecialists. found at: doi:10.1371/journal.pone.0013350.s005 (0.03 mb doc) pneumonia and respiratory failure from swineorigin influenza a (h1n1) in mexico efficacy 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