Suppression of COVID-19 outbreak in the municipality of Vo’, Italy

Abstract

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, the regional authorities imposed the lockdown of the whole municipality for 14 days. We collected information on the demography, clinical presentation, hospitalization, contact network and presence of SARS-CoV-2 infection in nasopharyngeal swabs for 85.9% and 71.5% of the population of Vo at two consecutive time points. On the first survey, which was conducted around the time the town lockdown started, we found a prevalence of infection of 2.6% (95% confidence interval (CI) 2.1-3.3%). On the second survey, which was conducted at the end of the lockdown, we found a prevalence of 1.2% (95% CI 0.8-1.8%). Notably, 43.2% (95% CI 32.2-54.7%) of the confirmed SARS-CoV-2 infections detected across the two surveys were asymptomatic. The mean serial interval was 6.9 days (95% CI 2.6-13.4). We found no statistically significant difference in the viral load (as measured by genome equivalents inferred from cycle threshold data) of symptomatic versus asymptomatic infections (p-values 0.6 and 0.2 for E and RdRp genes, respectively, Exact Wilcoxon-Mann-Whitney test). Contact tracing of the newly infected cases and transmission chain reconstruction revealed that most new infections in the second survey were infected in the community before the lockdown or from asymptomatic infections living in the same household. This study sheds new light on the frequency of asymptomatic SARS-CoV-2 infection and their infectivity (as measured by the viral load) and provides new insights into its transmission dynamics, the duration of viral load detectability and the efficacy of the implemented control measures.

Transmission dynamics of the COVID-19 epidemic in India and modelling optimal lockdown exit strategies

“…Estimates for asymptomatics range from 18% to 80% of total infections. 17,18,[32][33][34] With India and China reporting asymptomatics in the higher ranges, it may be possible that young and developing countries have a high proportion of asymptomatic carriers. These estimates are crosssectional, and thus do not differentiate asymptomatics from presymptomatics.…”

“…We set the probability of infected case being asymptomatic (p a ) to 0•2, 0•4, 0•6, 0•8, as reported estimates for the percent of infections that are asymptomatic range widely from 18% 80%. 17,18,[32][33][34] We consider that asymptomatic cases do not exhibit coughing, sneezing or sputum production and are thus expected to show lower infectivity than symptomatics. We conservatively assume an asymptomatic patient is 50% as infective as a symptomatic patient (a i =0•5).…”

“…16 It may be possible that COVID19 transmission is driven significantly by undetected asymptomatics while fatality is driven by severe cases a devastating combination. 17,18 Some have deemed asymptomatic transmission as the "Achilles' Heel" of the current control strategies against COVID19, 19 and it is important to consider the range of uncertainty regarding same when simulating COVID19 transmission.…”

Modelling safe protocols for reopening schools during the COVID-19 pandemic in France

“…Adolescents, however, may have a different role in driving the epidemic spread compared to younger children. Massive testing in Iceland and in the municipality of Vo', Italy, the initial epicenter of the Italian outbreak, showed that children under 10 years of age had a lower incidence of COVID-19 than adolescents and adults 19,20 .…”

Response to ‘Is there a future for hydroxychloroquine/chloroquine in prevention of SARS-CoV-2 infection (COVID-19)?’ by Moiseev et al

“…Perhaps, we should also consider that almost half of SARS-CoV-2-infected subjects are asymptomatic. 9 However, in such a global health emergency, with more than 2.600.000 people with confirmed infection and almost 185.000 deaths (as of 23 April 2020), we do not feel to give any judgement on the opportunity of planning studies on the prophylactic effect of HCQ in subjects at highest risk of infection.…”