OBJECTIVES: The management of healthcare workers (HCWs) exposed to confirmed cases of COVID-19 is still a matter of debate. We aimed to assess in this group the attack rate of asymptomatic carriers and the symptoms most frequently associated with the infection. METHODS: Occupational and clinical characteristics of HCWs who performed a nasopharyngeal swab for the detection of SARS-CoV-2 in a University Hospital from February 24, to March 31, 2020, were collected. For those who tested positive and for the asymptomatic positives we checked laboratory and clinical data as of May 22 to calculate the time necessary to become test-negative and to verify whether symptoms developed thereafter. Frequencies of positive tests were compared according to selected variables using multivariable logistic regression models. RESULTS: Positive tests were 139 among 1,573 HCWs (8.8%, 95% confidence interval [CI]: 7.5-10.3), with a marked difference between symptomatic (122/503, 24.2%) and asymptomatic (17/1,070, 1.6%) workers (p<0.001). Physicians were the group with the highest frequency of positive tests (61/582, 10.5%), whereas clerical workers and technicians displayed the lowest frequency (5/137, 3.6%). The likelihood of being positive increased with the number of reported symptoms and the strongest predictors were taste and smell alterations (odds ratio [OR]= 76.9) and fever (OR = 9.12). The median time from first positive test to a negative test was 27 days (95% CI: 24-30). CONCLUSIONS: A relevant number of HCWs can be infected by SARS-CoV-2 without displaying any symptom. Among symptomatic workers, the key symptoms to guide diagnosis are taste and smell alterations and fever. In median, almost four weeks are necessary to achieve negativity of nasopharyngeal swab.
Characteristics of 1,573 healthcare workers who underwent nasopharyngeal swab for SARS-CoV-2 in Milano, Lombardy, Italy