SARS-CoV-2 seroprevalence trends in healthy blood donors during the COVID-19 outbreak in Milan.
Luca Valenti, Annalisa Bergna, Serena Pelusi, Federica Facciotti, Alessia Lai, Maciej Tarkowski, Angela Lombardi, Alessandra Berzuini, Flavio Caprioli, Luigi Santoro, Guido Baselli, Carla Della Ventura, Elisa Erba, Silvano Bòsari, Massimo Galli, Gianguglielmo Zehender, Daniele Prati
Abstract
BACKGROUND: The Milan metropolitan area in Northern Italy was among the most severely hit by the SARS-CoV-2 outbreak. The aim of this study was to examine the seroprevalence trends of SARS-CoV-2 in healthy asymptomatic adults, and the risk factors and laboratory correlates of positive tests. MATERIALS AND METHODS: 2020; n=789). Presence of IgM/IgG antibodies against the SARS-CoV-2-Nucleocapsid protein was assessed by a lateral flow immunoassay. RESULTS: (p=not significant). At multivariate logistic regression analysis, IgG reactivity was more frequent in younger individuals (p=0.043), while IgM reactivity was more frequent in individuals aged >45 years (p=0.002). DISCUSSION: SARS-CoV-2 infection was already circulating in Milan at the start of the outbreak. The pattern of IgM/IgG reactivity was influenced by age: IgM was more frequently detected in participants aged >45 years. By the end of April, 2.4-9.0% of healthy adults had evidence of seroconversion.