Characteristics of 1,573 healthcare workers who underwent nasopharyngeal swab for SARS-CoV-2 in Milano, Lombardy, Italy
Authors: Lombardi Andrea , Consonni Dario , Carugno Michele , Bozzi Giorgio , Mangioni Davide , Muscatello Antonio , Castelli Valeria , Palomba Emanuele , Cantù Anna Paola , Ceriotti Ferruccio , Tiso Basilio , Pesatori Angela Cecilia , Riboldi Luciano , Bandera Alessandra , Gori Andrea 
Published: May 2020

Background

The management of healthcare workers (HCWs) exposed to confirmed cases of COVID-19 is still a matter of debate. It is unclear whether these subjects should be tested in the absence of symptoms and if those can guide diagnosis.

Methods

Occupational and clinical characteristics of all the consecutive HCWs who performed a nasopharyngeal swab for the detection of SARS-CoV-2 in a University Hospital from February 24, 2020, to March 31, 2020, were collected. Frequencies of positive tests were compared according to selected variables. Multivariable logistic regression analyses were then applied.

Findings

Positive tests were 138 among 1,573 HCWs (8.8%, 95% confidence interval [CI]: 7.4-10.3), with a marked difference between symptomatic (20.2%, 95% CI: 16.7-24.1) and asymptomatic (3.7%, 95% CI: 2.7-5.1) subjects (p<0.001). Physicians were the group with the highest frequency of positive tests (10.6%, 95% CI: 8.3-13.4) whereas clerical workers and technicians displayed the lowest frequency (2.9%, 95% CI: 0.8-7.3). The likelihood of being positive increased with the number of reported symptoms and the strongest predictors of a positive test were taste and smell alterations (odds ratio [OR] = 29.7) and fever (OR = 7.21). The median time from first positive test to a negative test was 23 days (95% CI: 19-24).

Interpretation

In this Italian group of HCWs exposed to confirmed cases of COVID-19 the presence of symptoms, especially taste and smell alterations and fever, was associated with SARS-CoV-2 infection. The median time to clear the virus from nasopharynx was 23 days.

Funding

none related to the content of this manuscript.

Research in context

Evidence before this study

We searched PubMed for articles published in English up to April 25, 2020, using the keywords “SARS-CoV-2”, “COVID-19”, “2019-nCoV”, AND “healthcare workers”,“HCW”, AND “testing”, “nasopharyngeal swab”. We found one article:Roll-out of SARS-CoV-2 testing for healthcare workers at a large NHS Foundation Trust in the United Kingdom, March 2020published inEuro Surveillance. Reviewing the pre-print website medRxiv with the same keywords we identified two additional studies:SARS-CoV-2 infection in Health Care Workers in a large public hospital in Madrid, Spain, during March 2020, andSARS-CoV-2 infection in 86 healthcare workers in two Dutch hospitals in March.

Added value of this study

We showed that, even if symptomatic healthcare workers had a much higher probability of positive test, almost one third of those infected were asymptomatic. Specific symptoms, namely taste and smell alterations and fever, were strongly associated with the infection. Finally, the median time to clear the virus from nasopharynx was 23 days.

Implications of all the available evidence

Screening strategies for healthcare workers exposed to COVID-19 patients should take in account the significant proportion of asymptomatic carriers and the predictive role of specific symptoms. Moreover, healthcare workers coming back to work after a positive test should be aware of the long-time of viral shedding from nasopharynx.