Cluster of coronavirus disease 2019 (Covid-19) in the French Alps, 2020

Danis, Kostas; Epaulard, Olivier; Bénet, Thomas; Gaymard, Alexandre; Campoy, Séphora; Bothelo-Nevers, Elisabeth; Bouscambert-Duchamp, Maude; Spaccaferri, Guillaume; Ader, Florence; Mailles, Alexandra; Boudalaa, Zoubida; Tolsma, Violaine; Berra, Julien; Vaux, Sophie; Forestier, Emmanuel; Landelle, Caroline; Fougere, Erica; Thabuis, Alexandra; Berthelot, Philippe; Veil, Raphael; Levy-Bruhl, Daniel; Chidiac, Christian; Lina, Bruno; Coignard, Bruno; Saura, Christine

BACKGROUND: On 07/02/2020, French Health authorities were informed of a confirmed case of SARS-CoV-2 coronavirus in an Englishman infected in Singapore who had recently stayed in a chalet in the French Alps. We conducted an investigation to identify secondary cases and interrupt transmission. METHODS: We defined as a confirmed case a person linked to the chalet with a positive RT-PCR sample for SARS-CoV-2. RESULTS: The index case stayed 4 days in the chalet with 10 English tourists and a family of 5 French residents; SARS-CoV-2 was detected in 5 individuals in France, 6 in England (including the index case), and 1 in Spain (overall attack rate in the chalet: 75%). One pediatric case, with picornavirus and influenza A coinfection, visited 3 different schools while symptomatic. One case was asymptomatic, with similar viral load as that of a symptomatic case. Seven days after the first cases were diagnosed, one tertiary case was detected in a symptomatic patient with a positive endotracheal aspirate; all previous and concurrent nasopharyngeal specimens were negative. Additionally, 172 contacts were monitored, including 73 tested negative for SARS-CoV-2. CONCLUSIONS: The occurrence in this cluster of one asymptomatic case with similar viral load as a symptomatic patient, suggests transmission potential of asymptomatic individuals. The fact that an infected child did not transmit the disease despite close interactions within schools suggests potential different transmission dynamics in children. Finally, the dissociation between upper and lower respiratory tract results underscores the need for close monitoring of the clinical evolution of suspect Covid-19 cases.