Our results, showing a high prevalence of SARS-CoV-2 infection among HCWs, are in line with previous data that demonstrated that HCWs have higher susceptibility to respiratory infections. These findings were also observed in other zoonotic coronavirus outbreaks (SARS and MERS), when a substantial proportion of the infected population were HCWs [3,9]. They are repeatedly exposed to COVID-19 patients, particularly those working on frontline, where certain procedures ( intubation, contact with secretions, aerosol-generating procedures) increase the risk of infection, highlighting the importance of using the recommended personal protective equipment (PPE) measures .
In our hospital, universal use of masks by all HCWs was implemented as a standard practice in the hospital only in the first week of May. According to the standard infection prevention protocol in place at that time, PPE was recommended only when caring for suspected or confirmed COVID-19 patients. It is important to emphasize that during the whole study period, availability and access to PPE, as well as training and supervision from the infection prevention and control committee members, were fully provided to HCWs, with adequate adherence to the protocols. Hospitalized patients were in transmission-based isolation precautions only when presenting symptoms compatible with COVID-19 or with history of known exposure to a COVID-19 patient in the previous 14 days. Although HCWs are at higher risk of SARS-CoV-2 infection at work, while caring for suspected or confirmed COVID-19 patients, household and community transmission are also relevant, particularly during the period of the study, when an intense activity of community transmission was occurring in São Paulo (In May more than 200 new COVID-19 cases per 100,000 persons within 14 days was reported) .
The rates of hospitalization among HCWs with COVID-19 (7.2%), as well as case fatality rates (1.6%) found in our study are similar to those reported in US among HCWs patients with data available on age and health outcomes (respectively 8% and 0.6%) . Interestingly, these rates are lower than those found in non-HCWs population with COVID-19 in Brazil , probably reflecting the younger median age of the HCWs of our hospital. Furthermore, it is likely that among HCWs the level of suspicion to the disease symptoms is higher, enabling them to an earlier diagnosis and treatment, which may improve COVID-19 outcomes, and identifying a higher proportion of mild cases. Similar to earlier findings , our data also showed that male sex was associated with a higher risk of severe outcomes (78% of the HCWs that were hospitalized and both that died were men).
There are conflicting results in the literature to identify the job category with the highest risk of COVID-19 among HCWs [6, 7, 11]. In our study, physicians represented the majority of the cases, even though nurses form the largest subset of employees in the hospital. Compared to other HCWs, physicians seem to have greater awareness of disease symptoms, facilitating their access to testing and medical care.
In the city of São Paulo, the epicenter of the pandemic in Latin America, on June 14th, during the study period, there were 98,000 confirmed cases of COVID-19, of which, 1,902 (1.94%) were HCWs, with 26 confirmed deaths (CFR of 1.3%), similar to the CFR found in our study . Data from China showed that a total of 3,387 of 77,262 patients with COVID-19 (4.4%) were HCWs, with 23 deaths (CFR of 0.67%) .
The sustained high weekly prevalence rates of SARS-CoV-2 infection among symptomatic HCWs observed in our study (from 22.3% to 55.9%), when compared to similar studies from Asia, Europe and US [11-14, 20-22] is concerning (figure1). The majority of our cohort had a mild illness, which could potentially represent a risk of continued routine of working throughout the illness, facilitating the transmission of the virus into the hospital to patients and other HCWs. It is also concerning the long median time between symptom onset and RT-PCR testing among HCWs found in our study (6.3 days), despite the presence of recommendations to self-isolation when symptomatic. This finding may represent a significant risk of increasing transmission. Similar studies in Europe demonstrated that a high proportion of HCWs maintained their work routine in the hospital even presenting mild symptoms [11-13]. These findings highlight the importance of having not only well-stablished guidance for all HCWs on the use of PPE, but also clear recommendations on sick leave policies for all HCWs with suspected COVID-19.
Limitations of this study include the single-hospital design and testing only symptomatic HCWs. Furthermore, the study was not designed to identify the source of infection among symptomatic HCWs. This approach limited the possibility of a better understanding on the transmission dynamics as well as the true prevalence of SARS-Co-V-2 infection among HCWs. However, to our knowledge this is the first report describing prevalence, clinical characteristics, and outcomes of SARS-CoV-2 infection among HCWs in Latin America.
One of the great challenges we faced in Brazil, and probably one of the reasons that contributed to the high burden of COVID-19 in the country, was the limited availability of virologic testing. Only suspected cases that were hospitalized could be tested for SARS-CoV-2 in the public health system. During the initial phase of the pandemic, even symptomatic HCWs were not able to be tested for the virus in our hospital as well as several others in the country. These limited testing clearly compromises the strategies to contain nosocomial transmission of the virus to inpatients and to other HCWs . Expanding capacity of testing among HCWs, including not only symptomatic, but also asymptomatic (facilitating detection of those that are in the presymptomatic phase, when transmission is already occurring) is the logical strategy in places where budget-resource constraints are not present, particularly among groups like HCWs, susceptible to high exposure to infected patients. Recent data from a large UK teaching hospital demonstrated the value of a comprehensive screening, including asymptomatic and oligosymptomatic HCWs, emphasizing the importance of this expanded strategy for protecting patients and hospital staff .
COVID-19 has a wide spectrum of clinical manifestations ranging from asymptomatic illness to severe cases with multi-organ failure and death. Our study provides valuable information on symptoms in the early phase of COVID-19 among HCWs. Anosmia and ocular pain were symptoms independently associated with SARS-CoV-2 test positivity. In low and middle-income countries, where limited availability of tests is frequent, these findings may contribute to optimize a targeted symptom-oriented screening strategy.