Screening around a COVID-19 cluster: Exploring its impact on a local virus outbreak

•A screening of all high-risk contacts in this cluster, as well as different individuals living in their household, led to identification of 11% of new cases among screened individuals.•This large-scale screening, which included not only the contacts of COVID-19 cases, but also the members of their households, broke chains of transmission.•Large-scale screening led to the identification of persons; some of them asymptomatic, who were not initially considered as being or having been in direct contact with index cases.•Early and large-scale screening around this cluster, conducted a few days before the national lockdown, probably helped to limit the propagation of SARS-CoV-2 in the local population. In March 2020, we implemented screening of the contacts of a COVID-19 cluster having occurred in the Lot-et-Garonne department, the first department of the Nouvelle-Aquitaine region to be affected by the active circulation of SARS-CoV-2. We aimed to describe the impact of this screening on the local SARS-CoV-2 outbreak. All high-risk contacts, as well as the individuals living in their households, were screened. We detailed the evolution of the number of confirmed COVID-19 cases in the Lot-et-Garonne department and the rest of the Nouvelle-Aquitaine region. Among the 89 screened individuals, 10 new cases were confirmed, including 4 asymptomatic persons. In Lot-et-Garonne, the number of confirmed COVID-19 cases immediately decreased after this screening and no epidemic peak occurred, contrary to what was observed in the rest of the region. The early screening of high-risk contacts of COVID-19 cases and members of their household implemented a few days before the first lockdown probably helped to prevent the spread of the virus in the department.