Identification of Asymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infections Among Healthcare Workers at Sultan Qaboos University Hospital, Oman

Abstract

Objectives

This study aimed to describe the incidence and features of asymptomatic COVID-19 infections among healthcare workers (HCWs) at a tertiary hospital in Oman.

Methods

This cross-sectional study was conducted between August 2020 and February 2021 among HCWs with no history of COVID-19 infection. An online questionnaire collected sociodemographic and clinical data. COVID-19 infection was diagnosed using nasopharyngeal/throat swabs, which were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Analyses were performed using the Chi-squared test, Fisher’s exact test or univariate ordinary least squares regression, as appropriate.

Results

A total of 583 HCWs participated in the study, most of whom were female (56.6%), and the mean age was 35 ± 8 years. Only 9.6% (95% confidence interval [CI]: 7.3–12.3%) of the HCWs were at high exposure risk as they were directly involved in the care of COVID-19-infected patients. Overall, 4.1% (95% CI: 2.7–6.1%) of the HCWs screened positive for SARS-CoV-2, of which 20.8% developed symptoms within two weeks. The frequency of SARS-CoV-2 positivity among HCWs working in high-, intermediate-, low- and miscellaneous-risk areas was 1.8% (95% CI: <0.1–9.6%), 2.6% (95% CI: <0.1–6.5%), 5.3% (95% CI: 0.3–9.3%) and 4.8% (95% CI: <0.1–69.3%), respectively. Working in high-risk areas was associated with increased compliance with various infection control strategies (P <0.001).

Conclusion

There was a greater frequency of SARS-CoV-2 positivity among HCWs working in low-risk areas, whereas HCWs who worked in high-risk areas were significantly more likely to report increased compliance with infection control strategies.

Advances in Knowledge

• - This study found that the prevalence of asymptomatic coronavirus disease 2019 (COVID-19) infections among healthcare workers (HCWs) working at a tertiary hospital in Muscat, Oman was 4.1% (95% confidence interval [CI]: 2.7–6.1%), including 1.8% (95% CI: <0.1–9.6%), 2.6% (95% CI: <0.1–6.5%), 5.3% (95% CI: 0.3–9.3%) and 4.8% (95% CI: <0.1–69.3%) of HCWs working in high-, intermediate-, low- and miscellaneous-risk areas, respectively.

• - Overall, HCWs in high-risk areas were significantly more likely to adhere to COVID-19 infection control practices, including hand hygiene and wearing appropriate personal protective equipment during interactions with infected patients.

• - To the best of the authors’ knowledge, the incidence of asymptomatic COVID-19 infections among HCWs in Oman has not previously been reported.

Application to Patient Care

• - The findings of this study indicate that asymptomatic COVID-19-infected HCWs may constitute a significant transmission risk in hospital settings.

• - Hospital authorities should consider implementing routine interval screening to detect asymptomatic infections among HCWs. In addition, there is a need to increase adherence to infection prevention and control strategies among asymptomatic HCWs in lower-risk areas to reduce the possibility of unknowingly transmitting the disease to others.

Coronavirus disease 2019 (covid-19) is a respiratory illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Clinical manifestations of COVID-19 infection range from a mild cough and sore throat to fulminant pneumonia and multi-organ failure. However, a notable proportion of infected patients may be asymptomatic, especially in the early stages of infection.1–3 In the absence of symptoms, COVID-19 infections can be identified using a positive SARS-CoV-2 RNA test or based on chest X-ray or computed tomography findings.2 Since the initial outbreak of the disease in December 2019, COVID-19 has proven to be highly transmissible, with more than 5.9 million confirmed cases worldwide as of August 2022.4

According to back casting statistical estimates, the rate of COVID-19 infection in the general population is 6.08% (95% confidence interval [CI]: 4.24–10.68%).5 However, people who reside or work in densely populated or confined environments such as cruise ships, homeless shelters and prisons can be exposed to even higher rates of infection.6–8 In addition, healthcare workers (HCWs) are at a generally increased risk of COVID-19 infection due to their exposure to and role in the care and management of infected patients. In Hubei, China, the epicentre of the COVID-19 outbreak, the number of infected HCWs increased from 1,502 to 3,062 in a span of 13 days.9 In the UK, a recent study reported that up to 24.4% of asymptomatic HCWs may demonstrate SARS-CoV-2 seropositivity.10

Asymptomatic COVID-19 infections are confirmed by the evidence of SARS-CoV-2 positivity in the absence of self-reported or clinically discernible symptoms.3 The identification of asymptomatic cases is an important factor in better understanding the epidemiology of infectious diseases and may help inform appropriate measures to prevent transmission. Researchers have warned of the dangers posed by ‘invisible epidemics’ or ‘silent spread’ because asymptomatic carriers are unlikely to seek timely treatment. This is concerning as the absence of symptoms does not mean a lack of subclinical damage to the lungs or other organs. Additionally, asymptomatic individuals can unknowingly transmit the infection to others.11,12 A recent systematic review and meta-analysis by Ma et al. found the pooled percentage of asymptomatic SARS-CoV-2 infections to be 0.25% (95% CI: 0.23–0.27%) among 29,776,306 individuals reported in 95 studies. This represented 40.5% of all infections detected in the tested population.13 Similarly, a narrative review by Oran et al. indicated that up to 40–45% of reported SARS-CoV-2 infections are asymptomatic in nature.12

In the Gulf Cooperation Council region, few studies have sought to assess the frequency of asymptomatic infections among HCWs. In the United Arab Emirates, researchers reported that up to 43% of identified COVID-19 cases were asymptomatic. However, only 3% of the COVID-19-infected patients being studied (i.e. both symptomatic and asymptomatic cases) were employed in occupations with high exposure risk, including HCWs.14 Al-Hakami et al. identified the prevalence of asymptomatic infections to be 18.3% among 186 HCWs working in tertiary care centres in southwestern Saudi Arabia.15 Another study found that the seroprevalence of SARS-CoV-2 was 3.2% among asymptomatic HCWs in a larger tertiary hospital in Riyadh, Saudi Arabia.16 However, to the best of the authors’ knowledge, the incidence of asymptomatic COVID-19-infected HCWs in Oman has not previously been reported. Furthermore, it is unclear whether specific clinical or sociodemographic factors influence the risk of asymptomatic infection in this population. As such, this study aimed to identify the prevalence of and sociodemographic and clinical characteristics associated with COVID-19 infections among asymptomatic HCWs working at a tertiary university hospital in Muscat, Oman.

Methods

This cross-sectional study was conducted between August 2020 and February 2021 at the Sultan Qaboos University Hospital (SQUH), a large tertiary university hospital in Muscat, Oman. The target population included all asymptomatic HCWs from different SQUH departments and of all job titles and responsibilities including physicians, nurses, medical orderlies and administrative and security personnel. Only HCWs without a previous diagnosis of COVID-19 disease were eligible for inclusion in the study. As such, the inclusion criteria comprised hospital staff working in all clinical or administrative areas of the hospital. The exclusion criteria consisted of staff who were symptomatic on the day of recruitment or those who reported a history of positive SARS-CoV-2 swab results at any point beforehand. However, staff who reported symptoms within seven days of swab collection were included in the study so long as they were asymptomatic on the day of recruitment/data collection.

An invitation to participate in the study was published on the hospital’s home page to recruit participants. Respondents were initially screened for inclusion in the study to identify those who were asymptomatic and had no history of COVID-19 infection. Based on the initial sample size calculation, a total of 992 subjects were needed (496 in each arm) to ensure 90% power to detect a statistical difference of 10% (i.e. 30% versus 40% when detecting COVID-19 in high-risk versus low-risk areas) at the 5% alpha level. However, only 583 HCWs were recruited and included in the final sample. The participants were subsequently categorised into four groups based on their level of risk of exposure to COVID-19-infected patients, including: (1) high-risk (i.e. HCWs working in COVID-19 wards or the COVID intensive care unit [ICU]); (2) intermediate-risk (i.e. HCWs working in emergency medicine or family medicine, public health departments and laboratories); (3) low-risk (i.e. HCWs working in all other wards, non-COVID-19 ICU, paediatric ICU and ambulatory clinics); and (4) miscellaneous risk (i.e. all remaining HCWs).

An online questionnaire was used to collect sociodemographic data from the participants, including their gender, age, working area, place of residence, occupation and education level. In addition, clinical information was elicited, including self-assessed symptomatology, history of contact with COVID-19-infected persons, personal protective equipment (PPE) use, training and other relevant epidemiological risk factors, including a recent history of inter-city travel or attendance at large social gatherings. The questionnaire was adapted from the World Health Organization’s data template; however, modifications were made to include additional information, such as epidemiological risk factors. It is important to note that the modified version of the questionnaire was not validated.17 Subsequently, combined nasopharyngeal/throat swabs were collected from all the participants by trained research assistants. The participants’ RNA was extracted from the samples using fully automated nucleic acid extraction systems, including either the MagNA Pure LC 2.0 Total Nucleic Acid Isolation Kit (Roche Diagnostics GmbH, Mannheim, Germany) or Liferiver EX3600 Automated Nucleic Acid Extraction System (Shanghai Bio-Tech Co. Ltd., Shanghai, China).

The extracted RNA was tested for SARS-CoV-2 using a real-time polymerase chain reaction performed using either the LightMix^® Modular SARS-CoV-2 Assay (Roche Diagnostics GmbH), Liferiver Novel Coronavirus Real Time Multiplex RT-PCR (Shanghai Bio-Tech Co. Ltd.) or TaqPath^™ RT-PCR COVID-19 Kit (Thermo Fisher Scientific Inc., Waltham, Massachusetts, USA). Samples were considered positive when at least two targeted genes were detected, negative when all targeted genes were negative and inconclusive when only one gene was detected. For all inconclusive cases, repeat sampling and testing were performed. Participants with positive COVID-19 results were informed of their diagnosis within 24–48 hours and quarantined according to local guidelines. In addition, they were assessed for symptomatology for up to two weeks after testing positive.

Statistical analyses were conducted using the STATA Statistical Software Package, Version 16.1 (STATA Corp., College Station, Texas, USA). Descriptive results were presented as frequencies and percentages (categorical variables) or means and standard deviations (continuous variables), as appropriate. Differences between the exposure risk groups (i.e. HCWs working in high-, intermediate-, low- and miscellaneous-risk areas) were analysed using either Pearson’s Chi-squared test or Fisher’s exact test (for cell frequencies of <5). Differences between continuous variables were assessed using univariate ordinary least squares regression. The a priori two-tailed level of significance was set at 0.05.

Ethical approval for this study was obtained from the Medical Research and Ethics Committee of Sultan Qaboos University, Muscat, Oman (SQU-EC/085/2020 MREC #2137). All HCWs provided written informed consent prior to participating in the study. All study procedures were performed in accordance with local and international ethical standards. Data confidentiality was ensured at all times to ensure privacy.

Results

Of the 583 HCWs who participated in the study, over half were female (n = 330, 56.6%), and approximately one-third (n = 212, 36.4%) were of Omani nationality. The mean age was 35 ± 8 years (range: 22–59 years). Overall, 24 HCWs (4.1%; 95% CI: 2.7–6.1%) tested positive for SARS-CoV-2 based on the RNA test. Among them, five (20.8%; 95% CI: 7.1–42.2%) developed COVID-19 symptoms within two weeks of swab collection, including cough, fever, sore throat, body aches and pain. In addition, some participants reported a history of symptoms in the week prior to swab collection, although they were asymptomatic upon enrolment in the study. The three most common pre-swab symptoms were sore throat (n = 48, 8.2%), muscle aches (n = 47, 8.1%) and fatigue (n = 42, 7.2%).

The distribution of SARS-CoV-2 positivity among asymptomatic HCWs working in high-, intermediate-, low- and miscellaneous-risk areas was 1.8% (95% CI: <0.1–9.6%), 2.6% (95% CI: <0.1–6.5%), 5.3% (95% CI: 0.3–9.3%) and 4.8% (95% CI: <0.1–69.3%), respectively [Table 1]. High-risk areas had a higher proportion of female staff compared to intermediate-, low- or miscellaneous-risk areas (71.4% versus 64.3%, 65.2% and 33.7%, respectively; P <0.001). Furthermore, participants who reported having a sore throat in the week prior to swab collection were less likely to work in high-risk areas compared to intermediate-, low- or miscellaneous-risk areas (1.8% versus 10.4%, 11.1% and 4.8%, respectively; P = 0.026). No significant differences in age or other symptomatology were observed across different risk areas, including fever, fatigue, cough, sore throat, loss of taste or smell, shortness of breath, chest pains, muscle aches and nausea/vomiting/diarrhea.

Table 1.

Distribution of positive coronavirus disease 2019 cases among asymptomatic healthcare workers at Sultan Qaboos University Hospital, Muscat, Oman, according to in-hospital exposure risk status (N = 583)

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 the level of risk of exposure to COVID-19-infected patients as either high-risk (those working in COVID-19 wards or the COVID intensive care unit [ICU]), intermediate-risk (those working in the emergency medicine or family medicine and public health departments and laboratories), low-risk (those working in all other wards, the non-COVID-19 ICU, paediatric ICU and ambulatory clinics) or miscellaneous risk (those working in all other hospital areas).

^†Positivity was based on real-time polymerase chain reaction of RNA extracted from combined nasopharyngeal/throat swab samples.

The participants working in high-risk areas were significantly more likely to adhere to COVID-19 protective measures compared to those working in intermediate-, low- or miscellaneous-risk areas. Specifically, they were significantly more likely than the other participants to wear PPE as recommended during interactions with COVID-19-infected patients (94.6% versus 86.4%, 57.5% and 54.8%, respectively; P <0.001) and perform hand hygiene before and after interactions with COVID-19-infected patients (94.6% versus 89.6%, 66.2% and 63.3%, respectively; P <0.001). In addition, when performing aerosol-generating procedures on COVID-19-infected patients, HCWs working in high-risk areas were significantly more likely to wear gloves (92.9% versus 85.7%, 61.8% and 56.6%, respectively; P <0.001), wear fit-tested N95 or equivalent respirators (69.6% versus 46.1%, 39.6% and 44%, respectively; P = 0.001), wear face shields (92.9% versus 81.8%, 53.1% and 47.6%, respectively; P <0.001) and remove and replace their PPE according to hospital policy (92.9% versus 85.7%, 69.9% and 53%, respectively; P <0.001) compared to those working in intermediate-, low- or miscellaneous-risk areas. No significant differences were observed in terms of recent epidemiological risk factors (e.g. recent history of travel, attendance at social gatherings or contact with an infected person) according to differences in exposure risk [Table 2].

Table 2.

Epidemiological history and adherence to anti-coronavirus disease 2019 protective measures among asymptomatic healthcare workers at Sultan Qaboos University Hospital, Muscat, Oman, stratified by in-hospital exposure risk (N = 583)

Item	Risk status*, n (%)				P value
	High (n = 56)	Intermediate (n = 154)	Low (n = 207)	Miscellaneous (n = 166)
Epidemiological history
Have you recently travelled 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 away 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
Compliance with infection control measures
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 COVID-19 patients?	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 according to the level of risk of exposure to COVID-19-infected patients as either high-risk (those working in COVID-19 wards or the COVID intensive care unit [ICU]), intermediate-risk (those working in the emergency medicine or family medicine and public health departments and laboratories), low-risk (those working in all other wards, the non-COVID-19 ICU, paediatric ICU and ambulatory clinics) or miscellaneous risk (those working in all other hospital areas).

Discussion

In the current study, the overall prevalence of asymptomatic COVID-19 infections among HCWs working at a large tertiary hospital in Muscat was 4.1%, of which 20.8% developed mild symptoms within two weeks of swab collection. Previous studies have shown comparable prevalence rates of positive SARS-CoV-2 findings among asymptomatic HCWs elsewhere around the world (3.4–7.1%).18–20 Overall, 9.6% of the asymptomatic HCWs enrolled in the present study were directly involved in the care of COVID-19-infected patients and therefore faced a high-risk of exposure to infection, while 64% had either a low or miscellaneous/unknown risk of exposure to COVID-19-infected patients.

In the current study, adherence to various COVID-19 infection control and protective measures was significantly higher among HCWs working in high-risk areas than among those working in lower-risk areas. This could be attributed to the high-risk area HCWs’ increased awareness of patient COVID-19 status and clinical conditions. Nevertheless, it is important to acknowledge that pre-admission PCR testing for COVID-19 was not mandatory for asymptomatic patients. As a result, HCWs working in low-risk areas may have been more frequently exposed to undiagnosed patients without being aware of it. On the other hand, no significant differences were noted with regard to the frequency of various epidemiological risk factors regardless of risk exposure level, including recent inter-city travel, attendance of social gatherings and visiting relatives. However, due to the self-reported nature of these findings, the role of community transmission cannot be dismissed entirely.

There is evidence indicating that viral shedding and disease transmission can occur in the absence of symptoms (asymptomatic cases) as well as before symptom onset (presymptomatic cases).21–23 He et al. estimated that viral shedding in patients with laboratory-confirmed COVID-19 infections peaked at or before symptom onset, thus posing a substantial risk of transmission before symptoms in the index case are clinically discernible.21 Moreover, according to an analysis of seven epidemiological clusters, Wei et al. found that presymptomatic transmission of COVID-19 occurred on an average of 1–3 days before symptom onset.22 Zou et al. reported that viral loads detected in asymptomatic patients were similar to those found in symptomatic patients. In addition, the researchers confirmed that the median duration of viral shedding among asymptomatic individuals was 16.4 days (interquartile range: 7–28 days), comparable to symptomatic patients with mild-to-moderate disease severity.23 Such findings highlight the importance of preventing the spread of infections by asymptomatic individuals.

Chow et al. assessed the spectrum of initial symptoms among HCWs working in a long-term care facility in the USA and found that the median interval between disease onset and the appearance of established COVID-19 screening symptoms was two days (range: 1–7 days).24 Treibel et al. also noted that 27% of HCWs working in a UK-based hospital who tested positive for SARS-CoV-2 reported no symptoms in the week before or after testing positive.18 More inclusive contact tracing criteria are therefore needed to capture potential transmission events before symptom onset.21,22 Thus, a universal testing strategy, rather than a symptom-triggered approach, is recommended to identify and mitigate the spread of COVID-19 by asymptomatic individuals.24 Moreover, the use of combined nasopharyngeal/throat swabs is recommended due to conflicting findings on the differences in viral loads detected in swab samples obtained separately from the nose and throat.22,23 Chow et al. also noted that the inclusion of additional symptoms during COVID-19 screening, such as myalgias and chills, increased case detection by 6.3%.24

The findings of this study underscore the need for additional measures to prevent the spread of asymptomatic infections by HCWs. It is recommended that all HCWs routinely wear face masks and other appropriate PPE and adhere to institutional hand hygiene and infection control measures to prevent presymptomatic or asymptomatic transmission. These measures are particularly crucial for HCWs working in critical, chronic or long-term patient care and areas with a high frequency of community transmission.24 Other researchers have also recommended the implementation of a traffic control bundling approach to protect HCWs and mitigate the spread of infection during epidemics. This approach involves triaging patients before they enter the hospital and ensuring clear segregation of different risk zones, with strict disinfection protocol stations set up at inter-zone boundaries.25,26

Nevertheless, it is important to note that such recommendations may not help prevent the spread of COVID-19 infections via community transmission. The difference between nosocomial and community infections is contingent upon the setting. Nosocomial infections originate in hospital settings, provided that the infection was not present or incubating upon admission, while community infections develop elsewhere.27 Developing effective infection prevention and control measures requires an understanding of the differences between specific transmission settings and how they contribute to the spread of a particular disease.28 However, differentiating between nosocomial and community infections is often challenging due to uncertainty about the time of infection onset (i.e. prior to or within 48 hours of hospital admission). Moreover, in the context of the present study, this determination would be even more difficult in the absence of clinically discernible symptomatology. Therefore, stringent surveillance measures for all patients upon admission and routine screening of HCWs are recommended to determine whether COVID-19 infections can be classified as nosocomial or community infections.

This study has several limitations, including its observational design, small sample size and the absence of mandatory COVID-19 screening for HCWs. The present study was also limited by the smaller sample size (N = 583) compared to the original requirements based on sample size calculations with 90% power (N = 992). Therefore, further studies are warranted to corroborate the findings. The voluntary nature of enrolment introduces a high possibility of selection bias in the sample. Additionally, as a single-centre study covering a known geographical area, the findings may not reflect the true incidence of asymptomatic HCWs in other institutions in Muscat or elsewhere in Oman. Moreover, the study period did not cover the peak of the pandemic, which may have resulted in a lower prevalence. It is important to note that the analysis did not differentiate between asymptomatic and presymptomatic infections and did not consider vaccination status, as the vaccine roll-out in Oman began after the recruitment and data collection process had already commenced.

In addition, the current study did not assess individual levels of occupational risk exposure other than by designating risk levels to specific working areas. Thus, future research should be conducted to determine individual levels of occupational risk exposure, using, for example, the WHO risk assessment tool for HCWs.29 In addition, other variables that could influence the risk of infection, such as demographic characteristics and ethnicity, were not considered in the analysis. These factors should be considered in future studies. Finally, the information regarding participants’ recent epidemiological history was self-reported, which introduces the possibility of recall and social desirability biases. Consequently, the role of community transmission in the spread of COVID-19 among HCWs may have been underestimated.

Conclusion

Asymptomatic COVID-19-infected HCWs pose a significant transmission risk in hospital settings. Moreover, there was a higher frequency of SARS-CoV-2 positivity among HCWs working in lower-risk areas, whereas HCWs who worked in high-risk areas were significantly more likely to report increased compliance with infection control strategies. Hospital authorities should therefore implement interval screening for the detection of asymptomatic infections among HCWs in addition to enforcing adherence to infection control strategies.