Cluster of Coronavirus Disease 2019 (COVID-19) in the French Alps, February 2020
Authors: Danis Kostas , Epaulard Olivier , Bénet Thomas , Gaymard Alexandre , Campoy Séphora , Botelho-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 ,   Investigation Team, Brottet Elise , Casamatta Delphine , Gallien Yves , George Scarlett , Viriot Delphine , Ait Belghiti Fatima , Bernard-Stoecklin Sibylle , Desenclos Jean-Claude , Giese Coralie , Ghislain Didier , Gounon Magali , Grangeret Nathalie , Marie Cécile , Morel Bruno , Deher Muriel , Ronnaux Baron Anne-Sophie , Courbis Geneviève , Ragozin Nathalie , Wolska Monika , Serange Eric , Mercatello Delphine , Aiouaz Soraya , Valette Martine , Frobert Emilie , Josset Laurence , Escuret Vanessa , Morfin Florence , Billaud Geneviève , Blanc Myriam , Arata-Bardet Julie , Froidure Marie , Le Maréchal Marion , Pavese Patricia , Pierre Isabelle , Becker Agathe , Chauvelot Pierre , Conrad Anne , Ferry Tristan , Miailhes Patrick , Perpoint Thomas , Pouderoux Cécile , Roux Sandrine , Valour Florent , Lutz Marie-France , Pouvaret Anne , Vitrat Virginie , Maillet Mylène , Janssen Cécile , Piet Emilie , Bosch Alexie , Destrem Anne-Laure , Isnard Margaux , Challan-Belval Thibault , Wackenheim Chloe , Couturier Alice , Gheno Gael , Roupioz Thierry , Lucet Nicolas , Ayouni Stéphane , Vincent Mireille , de Epidemiología Servicio , General de Salud Pública del Gover Balear Dirección , Masserey Spicher Virginie , Bourquin Catherine , Stoll Jeanine , Chaud Pascal , Mounayar Anne-Laure 
Published: April 2020

Background

On 7 February 2020, French Health authorities were informed of a confirmed case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 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 reverse-transcription polymerase chain reaction 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, 1 tertiary case was detected in a symptomatic patient with from the chalet a positive endotracheal aspirate; all previous and concurrent nasopharyngeal specimens were negative. Additionally, 172 contacts were monitored; all contacts tested for SARS-CoV-2 (N = 73) were negative.

Conclusions

The occurrence in this cluster of 1 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 suspected cases of coronavirus disease 2019.