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Investigation of a COVID-19 outbreak on the Charles de Gaulle aircraft carrier, March to April 2020: a retrospective cohort study
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PA-CDG COVID-19 investigation group: Marion Fossier, Christelle Tong, Liliane Pellegrin, Sandrine Duron, Marie Dubois, Lénaïck Ollivier, Catherine Désideri Vaillant, Brice Schneider, Olivier Ferraris, Fabrice Biot, Noémie Verguet, Frédéric Iseni, Gaëlle Frenois-Veyrat, Marine Ridet, Marc Grandadam, Laurent Martinez, Jean-François Louis, Fabienne Lafrogne, Eric Reverbel, Jean-Marie Loreau, Yann Morin, Albane de Bonet d’Oléon, Lise Holterbach, Audrey Merens, Vincent Foissaud, Léopoldine Peron, Sophie Murris, Nastasia Menoud, Anne-Claire Garcia, Typhaine RessortView Citation Hide Citation
Citation style for this article: . Investigation of a COVID-19 outbreak on the Charles de Gaulle aircraft carrier, March to April 2020: a retrospective cohort study. Euro Surveill. 2022;27(21):pii=2100612. https://doi.org/10.2807/1560-7917.ES.2022.27.21.2100612 Received: 08 Jun 2021; Accepted: 16 Dec 2021
Abstract
SARS-CoV-2 emergence was a threat for armed forces. A COVID-19 outbreak occurred on the French aircraft carrier Charles de Gaulle from mid-March to mid-April 2020.
To understand how the virus was introduced, circulated then stopped circulation, risk factors for infection and severity, and effectiveness of preventive measures.
We considered the entire crew as a cohort and collected personal, clinical, biological, and epidemiological data. We performed viral genome sequencing and searched for SARS-CoV-2 in the environment.
The attack rate was 65% (1,148/1,767); 1,568 (89%) were included. The male:female ratio was 6.9, and median age was 29 years (IQR: 24–36). We examined four clinical profiles: asymptomatic (13.0%), non-specific symptomatic (8.1%), specific symptomatic (76.3%), and severe (i.e. requiring oxygen therapy, 2.6%). Active smoking was not associated with severe COVID-19; age and obesity were risk factors. The instantaneous reproduction rate (Rt) and viral sequencing suggested several introductions of the virus with 4 of 5 introduced strains from within France, with an acceleration of Rt when lifting preventive measures. Physical distancing prevented infection (adjusted OR: 0.55; 95% CI: 0.40–0.76). Transmission may have stopped when the proportion of infected personnel was large enough to prevent circulation (65%; 95% CI: 62–68).
Non-specific clinical pictures of COVID-19 delayed detection of the outbreak. The lack of an isolation ward made it difficult to manage transmission; the outbreak spread until a protective threshold was reached. Physical distancing was effective when applied. Early surveillance with adapted prevention measures should prevent such an outbreak.
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