Seroprevalence of SARS-CoV-2 and assessment of epidemiologic determinants in Portuguese municipal workers

ObjectivesTo assess the seroprevalence of SARS-CoV-2 antibodies in municipal employees of Northern Portugal during the first pandemic wave (May–June 2020) and its association with potentially related risk factors for infection.Material and MethodsThe authors assessed municipal employees of 2 cities in Northern Portugal, in whom serological tests to SARS-CoV-2 and an epidemiological survey were applied. The authors assessed the proportion of individuals presenting IgM and/or IgG antibodies to SARS-CoV-2, and evaluated the association between having positive serological test results, epidemiologic variables and clinical presentations. Reported symptoms were evaluated on their sensitivity, specificity, and predictive values.ResultsThe authors assessed 1696 employees, of whom 22.0% were firefighters, 10.4% were police officers, 10.3% were maintenance workers, and 8.1% were administrative assistants. The seroprevalence of SARS-CoV-2 infection was 2.9% (95% CI: 2.1–3.7%). Administrative assistants comprised the professional group with highest seroprevalence of SARS-CoV-2 (OR = 1.9 in the comparison with other occupational groups, 95% CI: 0.8–4.3, p = 0.126). The seroprevalence of SARS-CoV-2 infection among those who were in direct contact with COVID-19 patients in their professional activity was 3.9%, compared to 2.7% among those who were not in direct contact with such patients (OR = 1.5, 95% CI: 0.8–2.8, p = 0.222). The highest risk of infection was associated with the presence of a confirmed SARS-CoV-2 infection in the household (OR = 17.4, 95% CI: 8.3–36.8, p < 0.001). Living with a healthcare professional was not associated with a higher risk of infection (OR = 1.0, 95% CI: 0.4–2.5, p = 0.934). Anosmia/dysgeusia was the symptom with the highest positive predictive value (52.2%, 95% CI: 31.8–72.6, p < 0.001) and specificity (99.3%, 95% CI: 98.9–99.7, p < 0.001), while cough was the most prevalent symptom among SARS-CoV-2 seropositive participants (36%).ConclusionsThe authors observed a SARS-CoV-2 seroprevalence of 2.9% among assessed municipal employees. Anosmia/dysgeusia was the COVID-19 symptom which displayed the highest positive predictive value and specificity