A longitudinal study of healthcare workers' surveillance during the ongoing COVID-19 Epidemics in Italy: is SARS-CoV-2 still a threat for the Health-care System?

Barbaro, F.; Della Rocca, F.; Padoan, A.; Aita, A.; Vito, C.; Basso, D.; Cattelan, A.; Donato, D.; Plebani, M.; Dall'Olmo, L.

Objectives: In spring 2020, Northern Italy was the first area outside China to be involved in the SARS-CoV-2 pandemic. This observational study depicts SARS-CoV-2 prevalence and serological curves among first-line healthcare workers (HCWs) at Padua University Hospital (PdUH), North-East Italy. Method: 344 HCWs, working at the PdUH Emergency Department and Infectious Disease Unit, underwent a SARS-CoV-2 RNA nasopharyngeal swab with paired IgM and IgG antibody detection for 4 consecutive weeks. At every session, a questionnaire recorded symptoms, signs and recent contacts with SARS-CoV-2 patients. Positive cases were followed up for 5 months. Results: Twenty-seven HCWs (7.84%) had positive serology (Abs) with 12 positive swabs during the study period. Two additional HCWs were positive by swab but without Abs. Fourteen cases (4%) had SARS-CoV-2 infection before the beginning of the study. An HCW with autoimmune disease showed false Ab results. 46% of individuals with Abs reported no symptoms, in accordance with previous population studies. Fever, nasal congestion, diarrhoea and contacts with SARS-CoV-2 individuals correlated to SARS-CoV-2 infection. 96% of Abs+ cases showed persistent positive antibodies 5 months later and none was re-infected. Discussion: Correct use of PPEs and separate paths for positive/negative patients in the hospital can result in a low percentage of SARS-CoV-2 infections among HCWs, even in high risk settings. Frequent testing for SARS-CoV-2 with nasopharyngeal swabs is worthwhile, irrespective of HCWs' symptoms, due to the lack of specificity together with the high percentage of asymptomatic cases. Further studies are needed to elucidate the neutralizing effect of SARS-CoV-2 antibodies.