On the 21st of February 2020, a resident of the municipality of Vo’, a small town near Padua, died of pneumonia due to SARS-CoV-2 infection. This was the first COVID-19 death detected in Italy since the emergence of SARS-CoV-2 in the Chinese city of Wuhan, Hubei province. In response, an extensive swab testing campaign was implemented together with a 2-weeks lockdown, which were then followed by another swab testing survey. As part of the surveys, we collected information on the demography, clinical presentation, hospitalization, contact network and presence of SARS-CoV-2 infection. We found a prevalence of infection of 2.6% (95% confidence interval (CI) 2.1-3.3%) at the first survey, which declined to 1.2% (95% CI 0.8-1.8%) at the second survey. Notably, 42.5% (95% CI 31.5-54.6%) of the SARS-CoV-2 infections detected across the two surveys were asymptomatic (i.e., did not have symptoms at the time of swab testing and did not develop symptoms afterwards) and we found no statistically significant difference in the viral load of symptomatic versus asymptomatic infections.
In this talk, I will present these and other results obtained from the analysis of the data collected in Vo, which have been published in Nature last year (Lavezzo et al, Suppression of a SARS-CoV-2 outbreak in the Italian municipality of Vo, available at https://www.nature.com/articles/s41586-020-2488-1). I will also present preliminary results of two recent serological surveys conducted in the same population to assess the magnitude and duration of the antibody response, together with the results of an analysis of within-household SARS-CoV-2 transmission and an assessment of the impact of contact tracing on the epidemic dynamics and final size (the proportion of population infected).