SUBMITTED 14 SEP 2022 1 REVISION REQ. 25 OCT 22; REVISION RECD. 23 NOV 22 2 ACCEPTED 8 DEC 22 3 ONLINE-FIRST: FEBRUARY 2023 4 DOI: https://doi.org/10.18295/squmj.1.2023.008 5 6 Identification of Asymptomatic Severe Acute Respiratory Syndrome 7 Coronavirus 2 Infections among Healthcare Workers at Sultan Qaboos 8 University Hospital, Oman 9 *Amal Al Shibli,1 Mahmood Al Jufaili,1 Awatif Al Alawi,1 Abdullah 10 Balkhair,2 Ibrahim Al Zakwani,3 Faisal Al Azri,4 Khuloud Al Maamari,5 11 Fatma Ba Alawi,5 Azza Al Qayoudhi,5 Hajar Al Ghafri5 12 Departments of 1Emergency Medicine, 2Internal Medicine, 4Radiology & Molecular Imaging 13 and 5Microbiology & Immunology, Sultan Qaboos University Hospital, Muscat, Oman; 14 3Department of Pharmacology & Clinical Pharmacy, College of Medicine and Health 15 Sciences, Sultan Qaboos University, Muscat, Oman. 16 *Corresponding Author’s e-mail: ashibli@squ.edu.om 17 18 Abstract 19 Objectives: This study aimed to describe the incidence and features of asymptomatic 20 COVID-19 infections among HCWs at a tertiary hospital in Oman. Methods: This cross-21 sectional study was conducted between August 2020 and February 2021 among HCWs with 22 no history of COVID-19 infection using an online questionnaire to collect sociodemographic 23 and clinical data. COVID-19 infection was diagnosed using nasopharyngeal/throat swabs, 24 which were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). 25 Analyses were performed using Chi-squared test, Fisher’s exact test, or univariate ordinary 26 least squares regression, as appropriate. Results: A total of 583 HCWs participated in the 27 study. Most were female (56.6%) and the mean age was 35  8 years . Only 9.6% (95% 28 confidence interval [CI]: 7.3–12.3%) of the HCWs were at high exposure risk as they were 29 directly involved in the care of COVID-19-infected patients. Overall, 4.1% (95% CI: 2.7–30 6.1%) of the HCWs screened positive for SARS-CoV-2; of these, five (20.8%) developed 31 symptoms within two weeks. The frequency of SARS-CoV-2 positivity among HCWs 32 mailto:ashibli@squ.edu.om working in high, intermediate, low, and miscellaneous risk areas was 1.8% (95% CI: <0.1–33 9.6%), 2.6% (95% CI: <0.1–6.5%), 5.3% (95% CI: 0.3–9.3%), and 4.8% (95% CI: <0.1–34 69.3%), respectively. Working in high-risk areas was associated with increased compliance 35 with various infection control strategies (P <0.001). Conclusion: There was a greater 36 frequency of SARS-CoV-2 positivity among HCWs working in lower-risk areas, whereas 37 HCWs who worked in high-risk areas were significantly more likely to report increased 38 compliance with infection control strategies. 39 Keywords: SARS-CoV-2; COVID-19 Nucleic Acid Testing; Asymptomatic Infections; 40 Health Personnel; Occupational Exposure; Infection Control; Real-Time Polymerase Chain 41 Reaction; Oman. 42 43 Advances in Knowledge 44 - To the best of the authors’ knowledge, the incidence of asymptomatic coronavirus 45 disease 2019 (COVID-19) infections among healthcare workers (HCWs) in Oman has 46 not previously been reported. 47 - This study found that the prevalence of asymptomatic COVID-19 infections among 48 HCWs working at a tertiary hospital in Muscat, Oman, was 4.1% (95% confidence 49 interval [CI]: 2.7–6.1%), including 1.8% (95% CI: <0.1–9.6%), 2.6% (95% CI: <0.1–50 6.5%), 5.3% (95% CI: 0.3–9.3%), and 4.8% (95% CI: <0.1–69.3%) of HCWs 51 working in high, intermediate, low, and miscellaneous risk areas, respectively. 52 - Overall, HCWs in high-risk areas were significantly more likely to adhere to COVID-53 19 infection control practices, including hand hygiene and wearing appropriate 54 personal protective equipment during interactions with infected patients. 55 56 Application to Patient Care 57 - The findings of this study indicate that asymptomatic COVID-19-infected HCWs may 58 constitute a significant transmission risk in hospital settings. 59 - Hospital authorities should consider implementing routine interval screening to detect 60 asymptomatic infections among HCWs. In addition, there is a need to increase 61 adherence to infection prevention and control strategies among asymptomatic HCWs 62 in lower-risk areas to reduce the possibility of unknowingly transmitting the disease to 63 others. 64 65 Introduction 66 Coronavirus disease 2019 (COVID-19) is a respiratory illness caused by severe acute 67 respiratory syndrome coronavirus 2 (SARS-CoV-2). Clinical manifestations of COVID-19 68 infection range from a mild cough and sore throat to fulminant pneumonia and multi-organ 69 failure; however, a notable proportion of infected patients may be asymptomatic, especially 70 in the early stages of infection.1–3 In the absence of symptoms, COVID-19 infections can be 71 identified using a positive SARS-CoV-2 RNA test or based on chest X-ray or computed 72 tomography findings.2 Since the initial outbreak of the disease in December 2019, COVID-19 73 has proven to be highly transmissible, with more than 5.9 million confirmed cases worldwide 74 as of August 2022.4 75 76 According to back casting statistical estimates, the rate of COVID-19 infection in the general 77 population is 6.08% (95% confidence interval [CI]: 4.24–10.68%).5 However, people who 78 reside or work in densely populated or confined environments such as cruise ships, homeless 79 shelters, and prisons can have even higher rates of infection.6–8 In addition, healthcare 80 workers (HCWs) are at a generally increased risk of COVID-19 infection due to their 81 exposure to, and their role in the care and management of, infected patients. In Hubei, 82 China—the epicentre of the COVID-19 outbreak—the number of infected HCWs increased 83 from 1,502 to 3,062 in the span of 13 days.9 In the UK, a recent study reported that up to 84 24.4% of asymptomatic HCWs may demonstrate SARS-CoV-2 seropositivity.10 85 86 Asymptomatic COVID-19 infections are defined by evidence of SARS-CoV-2 positivity in 87 the absence of self-reported or clinically discernible symptoms.3 The identification of 88 asymptomatic cases is an important factor in better understanding the epidemiology of 89 infectious diseases and may help inform appropriate measures to prevent transmission. 90 Researchers have warned of the dangers posed by “invisible epidemics” or “silent spread”, 91 both because asymptomatic carriers are unlikely to seek timely treatment—which is 92 concerning as the absence of symptoms does not mean a lack of subclinical damage to the 93 lungs or other organs—as well as because of the risk they pose in unknowingly transmitting 94 the infection to others.11,12 A recent systematic review and meta-analysis by Ma et al. found 95 the pooled percentage of asymptomatic SARS-CoV-2 infections to be 0.25% (95% CI: 0.23–96 0.27%) among 29,776,306 individuals reported in 95 studies, representing 40.5% of all 97 infections detected in the tested population.13 Similarly, a narrative review by Oran et al. 98 indicated that up to 40–45% of reported SARS-CoV-2 infections are asymptomatic in 99 nature.12 100 101 In the Gulf Cooperation Council region, few studies have sought to assess the frequency of 102 asymptomatic infections among HCWs. In the United Arab Emirates, researchers reported 103 that up to 43% of identified COVID-19 cases were asymptomatic; however, only 3% of the 104 COVID-19-infected patients being studied (i.e., both symptomatic and asymptomatic cases) 105 were employed in occupations with high exposure risk, including HCWs.14 Al-Hakami et al. 106 identified the prevalence of asymptomatic infections to be 18.3% among 186 HCWs working 107 in tertiary care centres in Southwestern Saudi Arabia.15 Another study found that the 108 seroprevalence of SARS-CoV-2 was 3.2% among asymptomatic HCWs in a larger tertiary 109 hospital in Riyadh, Saudi Arabia.16 However, to the best of the authors’ knowledge, the 110 incidence of asymptomatic COVID-19-infected HCWs in Oman has not previously been 111 reported. Furthermore, it is unclear whether specific clinical or sociodemographic factors 112 influence the risk of asymptomatic infection in this population. As such, this study aimed to 113 identify the prevalence of and sociodemographic and clinical characteristics associated with 114 COVID-19 infections among asymptomatic HCWs working at a tertiary university hospital in 115 Muscat, Oman. 116 117 Methods 118 This cross-sectional study was conducted between August 2020 and February 2021 at the 119 Sultan Qaboos University Hospital (SQUH), a large tertiary university hospital in Muscat, 120 Oman. The target population included all asymptomatic HCWs from different SQUH 121 departments and of all job titles and responsibilities, including physicians, nurses, medical 122 orderlies and administrative and security personnel. Only HCWs without a previous diagnosis 123 of COVID-19 disease were eligible for inclusion in the study. As such, the inclusion criteria 124 comprised hospital staff working in all clinical or administrative areas of the hospital. The 125 exclusion criteria consisted of staff who were symptomatic on the day of recruitment or those 126 who reported a history of positive SARS-CoV-2 swab results at any point beforehand. 127 However, staff who reported symptoms within 7 days of swab collection were included in the 128 study so long as they were asymptomatic upon the day of recruitment/collection. 129 130 An invitation to participate in the study was published on the hospital’s home page to recruit 131 participants. Respondents were initially screened for inclusion in the study to identify those 132 who were asymptomatic and had no history of COVID-19 infection. Based on the initial 133 sample size calculation, a total of 992 subjects were needed (496 in each arm) to ensure 90% 134 power to detect a statistical difference of 10% (i.e., 30% versus 40% when detecting COVID-135 19 in high-risk versus low-risk areas) at the 5% alpha level. However, only 583 HCWs were 136 recruited and included in the final sample. Participants were subsequently categorised into 137 four groups based on their level of risk of exposure to COVID-19 infected patients, 138 including: (1) high-risk (i.e., HCWs working in COVID-19 wards or the COVID intensive 139 care unit [ICU]); (2) intermediate-risk (i.e., HCWs working in the emergency medicine or 140 family medicine and public health departments and laboratories); (3) low-risk (i.e., HCWs 141 working in all other wards, non-COVID-19 ICU, paediatric ICU, and ambulatory clinics); 142 and (4) miscellaneous risk (i.e., all remaining HCWs). 143 144 An online questionnaire was used to collect sociodemographic data from the participants, 145 including their gender, age, working area, place of residence, occupation and education level. 146 In addition, clinical information was elicited, including self-assessed symptomatology, 147 history of contact with COVID-19-infected persons, personal protective equipment (PPE) use 148 and training, and other relevant epidemiological risk factors, including a recent history of 149 inter-city travel or attendance at large social gatherings. The questionnaire was adapted from 150 the World Health Organization’s data template; however, modifications were made to include 151 additional information, such as epidemiological risk factors, and the modified version of the 152 questionnaire was not validated.17 Subsequently, combined nasopharyngeal/throat swabs 153 were collected from all participants by trained research assistants. RNA was extracted from 154 the respiratory samples using fully automated nucleic acid extraction systems, including 155 either the MagNA Pure LC 2.0 Total Nucleic Acid Isolation Kit (Roche Diagnostics GmbH, 156 Mannheim, Germany) or Liferiver EX3600 Automated Nucleic Acid Extraction System 157 (Shanghai Bio-Tech Co. Ltd., Shanghai, China). 158 159 The extracted RNA was tested for SARS-CoV-2 using real-time polymerase chain reaction 160 (PCR) performed using either the LightMix® Modular SARS-CoV-2 Assay (Roche 161 Diagnostics GmbH), Liferiver Novel Coronavirus Real Time Multiplex RT-PCR (Shanghai 162 Bio-Tech Co. Ltd.), or TaqPath™ RT-PCR COVID-19 Kit (Thermo Fisher Scientific Inc., 163 Waltham, Massachusetts, USA). Samples were considered positive when at least two targeted 164 genes were detected, negative when all targeted genes were negative, and inconclusive when 165 only one gene was detected. Repeat sampling and testing was performed for all inconclusive 166 cases. Participants with positive COVID-19 results were informed of their diagnosis within 167 24–48 hours and quarantined as per local guidelines; in addition, they were assessed for 168 symptomatology for up to 2 weeks from the time of test positivity. 169 170 Statistical analyses were conducted using the STATA statistical software package, Version 171 16.1 (STATA Corp., College Station, Texas, USA). Descriptive results were presented as 172 frequencies and percentages (categorical variables) or means and standard deviations 173 (continuous variables), as appropriate. Differences between exposure risk groups (i.e., HCWs 174 working in high, intermediate, low, and miscellaneous risk areas) were analysed using either 175 Pearson’s Chi-squared test or Fisher’s exact test (for cell frequencies of <5). Differences 176 between continuous variables were assessed using univariate ordinary least squares 177 regression. The a priori two-tailed level of significance was set at the 0.05 level. 178 179 Ethical approval for this study was obtained from the Medical Research and Ethics 180 Committee of Sultan Qaboos University, Muscat, Oman. All HCWs provided written 181 informed consent prior to participation in the study. All study procedures were performed in 182 accordance with local and international ethical standards. Data confidentiality was ensured at 183 all times in order to ensure privacy. 184 185 Results 186 Of the 583 HCWs who participated in the study, over half were female (n = 330; 56.6%) and 187 approximately one-third (n = 212; 36.4%) were of Omani nationality. The mean age was 35  188 8 years (range: 22–59 years). Overall, 24 HCWs (4.1%; 95% CI: 2.7–6.1%) tested positive 189 for SARS-CoV-2 based on the RNA test; of these, five (20.8%; 95% CI: 7.1–42.2%) 190 developed COVID-19 symptoms within two weeks of swab collection, including cough, 191 fever, sore throat, body aches, and pain. In addition, some of the participants reported a 192 history of symptoms within the week prior to the swab collection, although they were 193 asymptomatic upon enrolment into the study. The three most common of the pre-swab 194 symptoms were sore throat (n = 48; 8.2%;), muscle aches (n = 47; 8.1%), and fatigue (n = 42; 195 7.2%). 196 197 The distribution of SARS-CoV-2 positivity among asymptomatic HCWs working in high, 198 intermediate, low, and miscellaneous risk areas was 1.8% (95% CI: <0.1–9.6%), 2.6% (95% 199 CI: <0.1–6.5%), 5.3% (95% CI: 0.3–9.3%), and 4.8% (95% CI: <0.1–69.3%), respectively 200 [Table 1]. High-risk areas were more likely to be staffed by women than men in comparison 201 to intermediate, low, or miscellaneous risk areas (71.4% versus 64.3%, 65.2%, and 33.7%, 202 respectively; P <0.001). In addition, participants who reported having a sore throat in the 203 week prior to swab collection were less likely to work in high-risk areas compared to 204 intermediate, low, or miscellaneous risk areas (1.8% versus 10.4%, 11.1%, and 4.8%, 205 respectively; P = 0.026). No significant differences in age or other symptomatology were 206 noted according to differences in risk areas, including fever, fatigue, cough, sore throat, loss 207 of taste or smell, shortness of breath, chest pains, muscle aches, and 208 nausea/vomiting/diarrhoea. 209 210 Participants working in high-risk areas were significantly more likely to adhere to anti-211 COVID-19 protective measures compared to HCWs working in intermediate, low, or 212 miscellaneous risk areas. Specifically, they were significantly more likely to wear PPE as 213 recommended during interactions with COVID-19-infected patients (94.6% versus 86.4%, 214 57.5%, and 54.8%, respectively; P <0.001) and perform hand hygiene before and after 215 interactions with COVID-19-infected patients (94.6% versus 89.6%, 66.2%, and 63.3%, 216 respectively; P <0.001). In addition, when performing aerosol-generating procedures on 217 COVID-19-infected patients, HCWs working in high-risk areas were significantly more 218 likely to wear gloves (92.9% versus 85.7%, 61.8%, and 56.6%, respectively; P <0.001), wear 219 fit-tested N95 or equivalent respirators (69.6% versus 46.1%, 39.6%, and 44%, respectively; 220 P <0.001), wear face shields (92.9% versus 81.8%, 53.1%, and 47.6%, respectively; P 221 <0.001), and remove and replace their PPE according to hospital policy (92.9% versus 222 85.7%, 69.9%, and 53%, respectively; P <0.001) compared to those working in intermediate, 223 low, or miscellaneous risk areas. No significant differences were observed in terms of recent 224 epidemiological risk factors (e.g., recent history of travel, attendance at social gatherings, or 225 contact with an infected person) according to differences in exposure risk [Table 2]. 226 227 Discussion 228 In the current study, the overall prevalence of asymptomatic COVID-19 infections among 229 HCWs working at a large tertiary hospital in Muscat was 4.1%; of these, 20.8% developed 230 mild symptoms within two weeks of swab collection. Previous studies have shown 231 comparable prevalence rates of positive SARS-CoV-2 findings among asymptomatic HCWs 232 elsewhere around the world (3.4–7.1%).18–20 Overall, 9.6% of the asymptomatic HCWs 233 enrolled in the present study were involved directly in the care of COVID-19-infected 234 patients and therefore faced a high risk of exposure to infection, while 64% had either a low 235 or miscellaneous/unknown risk of exposure to COVID-19-infected patients. 236 237 Interestingly, adherence to various COVID-19 infection control and protective measures was 238 significantly higher among HCWs working in high-risk areas in the current study compared 239 to those working in lower-risk areas. This could be attributed to an increased awareness of 240 patient COVID-19 status and clinical condition on the part of HCWs working in high-risk 241 areas. Nevertheless, it is important to acknowledge that pre-admission PCR testing for 242 COVID-19 was not mandatory for asymptomatic patients; as a result, HCWs working in low-243 risk areas may have been more frequently exposed to undiagnosed patients without being 244 aware. On the other hand, no significant differences were noted with regards to the frequency 245 of various epidemiological risk factors regardless of risk exposure level, including recent 246 inter-city travel, attendance at social gatherings, and visiting relatives. However, due to the 247 self-reported nature of these findings, the role of community transmission cannot be 248 dismissed entirely. 249 250 There is evidence to indicate that viral shedding and disease transmission can occur in the 251 absence of symptoms (asymptomatic cases), as well as before symptom onset 252 (presymptomatic cases).21–23 He et al. estimated that viral shedding in patients with 253 laboratory-confirmed COVID-19 infections peaked at or before symptom onset, thus posing a 254 substantial risk of transmission before symptoms in the index case are clinically discernible.21 255 Moreover, according to an analysis of seven epidemiological clusters, Wei et al. found that 256 presymptomatic transmission of COVID-19 occurred on an average of 1–3 days before 257 symptom onset.22 Zou et al. reported that viral loads detected in asymptomatic patients were 258 similar to those found in symptomatic patients; in addition, the researchers confirmed that the 259 median duration of viral shedding among asymptomatic individuals was 16.4 days 260 (interquartile range: 7–28 days), comparable to symptomatic patients with mild-to-moderate 261 disease severity.23 Such findings highlight the importance of preventing the spread of 262 infections by asymptomatic individuals. 263 264 Chow et al. assessed the spectrum of initial symptoms among HCWs working in a long-term 265 care facility in the USA; the researchers found that the median interval between disease onset 266 and the appearance of established COVID-19 screening symptoms was 2 days (range: 1–7 267 days).24 Treibel et al. also noted that 27% of HCWs working in a UK-based hospital who 268 tested positive for SARS-CoV-2 reported no symptoms in the week before or after testing 269 positive.18 More inclusive contact tracing criteria are therefore needed to capture potential 270 transmission events before symptom onset.21,22 Thus, a universal testing strategy, rather than 271 a symptom-triggered approach, is recommended to identify and mitigate the spread of 272 COVID-19 by asymptomatic individuals.24 Moreover, the use of combined nasal/throat swabs 273 is recommended due to conflicting findings as to differences in viral loads detected in swab 274 samples obtained from the nose compared to the throat.22,23 Chow et al. also noted that the 275 inclusion of additional symptoms during COVID-19 screening, such as myalgias and chills, 276 increased case detection by 6.3%.24 277 278 The findings of this study underscore the need for additional measures to prevent 279 asymptomatic infection spread by HCWs. It is recommended that all HCWs routinely wear 280 face masks and other appropriate PPE and conform to institutional hand hygiene and 281 infection control measures in order to prevent presymptomatic or asymptomatic transmission. 282 Such measures are particularly crucial for HCWs working in critical, chronic or long-term 283 patient care and in areas with a high frequency of community transmission.24 Other 284 researchers have also recommended the implementation of a traffic control bundling 285 approach to protect HCWs and to mitigate infection spread during epidemics in which 286 patients are triaged prior to entering the hospital and there is a clear segregation of different 287 risk zones, with strict disinfection protocol stations set up at inter-zone boundaries.25,26 288 289 Nevertheless, it is important to note that such recommendations may not be helpful to prevent 290 the spread of COVID-19 infections via community transmission. The difference between 291 nosocomial and community infections is contingent upon setting; nosocomial infections refer 292 to those that originate in hospital settings, so long as the infection was not present or 293 incubating upon admission, while community-acquired infections represent those which 294 develop elsewhere.27 Developing effective infection prevention and control measures is only 295 possible by understanding differences between specific transmission settings and how these 296 contribute to the spread of a specific disease.28 However, distinguishing between hospital-297 acquired and community infections is often challenging due to uncertainty as to the onset of 298 the infection (i.e., prior to or within 48 hours of admission to hospital). Moreover, in the 299 context of the present study, this determination would be made even more difficult in the 300 absence of clinically discernible symptomatology. As such, stringent surveillance measures 301 for all patients upon admission, and the routine screening of HCWs, are recommended to 302 determine whether COVID-19 infections can be classified as community or hospital-303 acquired. 304 305 This study was subject to several limitations, including the observational design, small 306 sample size, and absence of compulsory COVID-19 screening for HCWs. The present study 307 was also limited by the smaller sample size (N = 583) in relation to original requirements 308 based on sample size calculations with 90% power (N = 992). Further studies are therefore 309 warranted to corroborate the findings. Due to the voluntary nature of enrolment, there is a 310 high possibility of selection bias in the sample. Furthermore, as a single-centre study 311 covering a known geographical area, the findings may not reflect the true incidence of 312 asymptomatic HCWs in other institutions in Muscat or elsewhere in Oman. Moreover, the 313 study period did not include the peak of the pandemic which could have resulted in a lower 314 prevalence. It is also important to note that the analysis did not distinguish between 315 asymptomatic and presymptomatic infections and did not consider vaccination status as the 316 vaccine roll-out in Oman occurred after the recruitment and data collection process had 317 already begun. 318 319 In addition, the current study did not assess individual levels of occupational risk exposure 320 other than by designating risk levels to specific working areas. Thus, future research should 321 be conducted to determine individual levels of occupational risk exposure, for instance using 322 the WHO risk assessment tool for HCWs.29 In addition, other variables which could influence 323 risk of infection, such as demographic characteristics and ethnicity, were not considered in 324 the analysis. These factors should be considered in future studies. Finally, findings related to 325 the participants’ recent epidemiological history were self-reported in nature and may 326 therefore have been subject to recall and social desirability bias; as such, community 327 transmission might have played a more significant role in the transmission of COVID-19 328 among HCWs than indicated. 329 330 Conclusion 331 Asymptomatic COVID-19-infected HCWs constitute a significant transmission risk in 332 hospital settings. Overall, 4.1% of the studied asymptomatic HCWs screened were positive 333 for SARS-CoV-2. Moreover, there was greater frequency of SARS-CoV-2 positivity among 334 HCWs working in lower-risk areas, whereas HCWs who worked in high-risk areas were 335 significantly more likely to report increased compliance with infection control strategies. 336 Hospital authorities should therefore implement interval screening for the detection of 337 asymptomatic infections among HCWs, in addition to enforcing adherence to infection 338 control strategies. 339 340 Acknowledgement 341 We thank the Research Council, Oman for funding this project. We thank all colleagues from 342 Sultan Qaboos University Hospital who provided insight and expertise that greatly assisted 343 the research. We also thank SN. Karen Manlangit and SN. Amira Al Abri from emergency 344 medicine department for their help as research assistants. We thank all the participants who 345 helped in making this research successful. 346 347 Conflicts of Interest 348 The authors declare no conflict of interests. 349 350 Funding 351 Funding for this study was obtained from the Research Council, Oman 352 353 Authors’ Contribution 354 AAS, MAJ, AAA and AB conceptualized and designed the study. AAS, AAA and IAZ 355 drafted the proposal and MAJ revised it. AAS, MAJ, AAA and AB prepared the 356 questionnaire. AAS and AAA supervised the work and the data collection process. FAA 357 provided equipment needed for sample analysis. KAM, FBA, AAQ and HAG contributed to 358 the processing of laboratory samples. AAS and AAA analysed the data. IAZ provided 359 statistical advice on study design and conducted the statistical analysis of the data. AAS, 360 AAA, AB, IAZ and KAM contributed to drafting the manuscript. AAS, MAJ, AAA, AB, 361 IAZ and KAM revised the manuscript. 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From: 460 https://apps.who.int/iris/handle/10665/331496 Accessed: Nov 2022. 461 462 https://doi.org/10.1093/cid/ciu978 https://doi.org/10.4103/0300-1652.103543 https://apps.who.int/iris/handle/10665/331496 Table 1: Distribution of positive coronavirus disease 2019 cases among asymptomatic 463 healthcare workers at Sultan Qaboos University Hospital, Muscat, Oman, according to in-464 hospital exposure risk status (N = 583) 465 Risk* status n (%) Total Positive† COVID-19 cases High 56 (9.6) 1 (1.8) Intermediate 154 (26.4) 4 (2.6) Low 207 (35.5) 11 (5.3) Miscellaneous 166 (28.5) 8 (4.8) Total 583 (100) 24 (4.1) COVID-19 = coronavirus disease 2019. *Participants were stratified according to level of 466 risk of exposure to COVID-19 infected patients as either high-risk (those working in COVID-467 19 wards or the COVID intensive care unit [ICU]), intermediate-risk (those working in the 468 emergency medicine or family medicine and public health departments and laboratories), 469 low-risk (those working in all other wards, the non-COVID-19 ICU, paediatric ICU, and 470 ambulatory clinics), or miscellaneous risk (those working in all other hospital areas). 471 †Positivity was based on real-time polymerase chain reaction of RNA extracted from 472 combined nasopharyngeal/throat swab samples. 473 474 Table 2: Epidemiological history and adherence to anti-coronavirus disease 2019 protective measures among asymptomatic healthcare workers 475 at Sultan Qaboos University Hospital, Muscat, Oman, stratified by in-hospital exposure risk (N = 583) 476 Item Risk* status, n (%) P value High (n = 56) Intermediate (n = 154) Low (n = 207) Miscellaneous (n = 166) E p id e m io lo g ic a l h is to r y Have you recently traveled between cities? 7 (12.5) 23 (14.9) 32 (15.5) 22 (13.3) 0.904 Have you attended a gathering with a person who has had SARS-CoV-2 detected? 3 (5.4) 22 (14.3) 16 (7.7) 20 (12) 0.115 Have you visited relatives within the last 14 days? 7 (12.5) 29 (18.8) 39 (18.8) 38 (22.9) 0.397 Have many times have you gone shopping in the last 14 days? 0.437 1–2 44 (78.6) 111 (72.1) 157 (75.8) 134 (80.7) 3–5 10 (17.9) 35 (22.7) 44 (21.3) 24 (14.5) >5 2 (3.6) 8 (5.2) 6 (2.9) 8 (4.8) How often do you adhere to physical distancing requirements (i.e., keeping 1–2 m from others) during your daily activities? 0.448 Always 12 (21.4) 29 (18.8) 32 (15.5) 17 (10.2) Mostly 34 (60.7) 87 (56.5) 125 (60.4) 103 (62) Sometimes 10 (17.9) 37 (24) 49 (23.7) 46 (27.7) Never 0 (0) 1 (0.6) 1 (0.5) 0 (0) Have you provided direct care to a confirmed COVID-19 patient? 52 (92.9) 95 (61.7) 53 (25.6) 20 (12) <0.001 Have you had unprotected contact with a confirmed COVID-19 patient? 10 (17.9) 41 (26.6) 19 (9.2) 9 (5.4) <0.001 Were you present during any aerosol-generating procedure performed on a patient? 39 (69.6) 65 (42.2) 27 (13) 10 (6) <0.001 Were you recently in an environment in which a confirmed COVID-19 patient was present? 47 (83.9) 102 (66.2) 66 (31.9) 30 (18.1) <0.001 C o m p li a n c e w it h i n fe c ti o n c o n tr o l m e a su r e s Have you been wearing PPE as recommended during interactions with COVID-19-infected patients? 53 (94.6) 133 (86.4) 119 (57.5) 91 (54.8) <0.001 Do you remove PPE as recommended after interactions with COVID-19-infected patients? 53 (94.6) 132 (85.7) 118 (57) 93 (56) <0.001 Do you perform hand hygiene before and after interactions with COVID-19-infected patients? 53 (94.6) 138 (89.6) 137 (66.2) 105 (63.3) <0.001 Do you wear PPE during any aerosol-generating procedures performed on COVID-19-infected patients? 51 (91.1) 132 (85.7) 119 (57.5) 88 (53) <0.001 Do you wear gloves during aerosol-generating procedures performed on a COVID-19 patient? 52 (92.9) 132 (85.7) 128 (61.8) 94 (56.6) <0.001 Do you wear fit-tested N95 or equivalent respirators during aerosol-generating procedures performed on COVID-19- infected patients? 39 (69.6) 71 (46.1) 82 (39.6) 73 (44) 0.001 Do you wear face-shields during aerosol-generating procedures performed on COVID-19-infected patients? 52 (92.9) 126 (81.8) 110 (53.1) 79 (47.6) <0.001 Do you wear disposable gowns during aerosol-generating procedures performed on COVID-19-infected patients? 52 (92.9) 131 (85.1) 120 (58) 84 (50.6) <0.001 Do you remove and replace PPE according to hospital regulations during aerosol-generating procedures performed on COVID-19-infected patients? 52 (92.9) 132 (85.7) 124 (59.9) 88 (53) <0.001 SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; COVID-19 = coronavirus disease 2019. *Participants were stratified 477 according to level of risk of exposure to COVID-19 infected patients as either high-risk (those working in COVID-19 wards or the COVID 478 intensive care unit [ICU]), intermediate-risk (those working in the emergency medicine or family medicine and public health departments and 479 laboratories), low-risk (those working in all other wards, the non-COVID-19 ICU, paediatric ICU, and ambulatory clinics), or miscellaneous 480 risk (those working in all other hospital areas). 481