Protecting healthcare workers (HCWs) is essential to safely maintaining healthcare systems during the coronavirus (COVID-19) pandemic [1]. A Dutch study of various hospitals during the early outbreak, found a 0–10% attack rate for reverse transcription-polymerase chain reaction (RT-PCR) diagnosed COVID-19 among HCWs with mild viral symptoms [2]. In several Asian countries, HCWs constituted >20% of presumptive occupational COVID-19 cases during the early outbreak [3]. At the Cambridge Health Alliance (CHA), the cumulative attack rate for RT-PCR-confirmed COVID-19 in the workforce is consistent with the Dutch report (>2.5%), with rates increasing from the early phase to the ‘surge’ phase (operation at high capacity with predominantly SARS-CoV-2-positive patients). A consistent picture of clinical COVID-19 among HCWs is emerging. The three most common symptoms are cough, fever and myalgia [4–6]. However, cough is non-specific, whereas systemic symptoms/signs (fever, body temperature ≥ 37.5°C, myalgia and headache) and anosmia/ageusia are much more frequent in HCWs with RT-PCR-confirmed COVID-19 compared to those testing negatively [6]. On the other hand, HCWs at both CHA and Pamplona with no symptoms or isolated sore throat/nasal congestion symptoms typically have negative SARS-CoV-2 RT-PCRs. During a pandemic, HCWs can be infected through travel, at home, in their communities or at work due to unprotected exposure to contagious patients, from infected co-workers and contaminated clinical environments. However, there are reassuring signs that personal protective equipment (PPE) (masks/respirators, gloves, eye protection and gowns), hand hygiene and distancing are effective measures in preventing COVID-19 among HCWs. In Pamplona, preliminary serology results for SARS-CoV-2 antibodies among HCWs on the ‘frontline’ (emergency room, inpatient and ICU wards) demonstrated similar seroprevalence results as compared to non-frontline personnel from the rest of the healthcare system. Further evidence of PPE effectiveness against SARS-CoV-2 comes from swab sampling from HCW PPE after caring for COVID-19 patients. No evidence of SARS-CoV-2 contamination was found on the surface of these gowns, face visor masks, N95 masks or goggles [7,8]. However, at CHA and Pamplona, occupational transmission has been documented in two situations: from infected HCWs to other HCWs; or to HCWs from patients admitted for non-COVID-19 indications, where precautions were not taken, and COVID-19 symptoms manifested later. There is also evidence of community-driven infection with multiple positives seen in HCWs residing in towns with high SARS-CoV-2 attack rates. These persons are more likely to be diagnosed at work because of testing priorities (as of 15 April 2020, CHA HCWs were 6.7 times more likely to be receive an RT-PCR than an average Massachusetts resident). Regardless of workplace infection control strategies, a critical challenge has been the ideal return to work strategy for HCWs who have contracted COVID-19. Strategies based on RT-PCR are safe, but often delay return to work, because positive assays may persist for weeks due to their high sensitivity. Research on viral shedding suggests that quantitative RT-PCR SARS-CoV-2 testing using a viral culture viability threshold may be useful [9,10], as can convalescent antibody testing, but all strategies remain empirical at this point [11].
