Management of the COVID-19 epidemic in the carrier battle group (January-April 2020) by the Armed Forces Epidemiology and Public Health Center

Faced with the COVID-19 epidemic that occurred within the naval air group and the nuclear aircraft carrier Charles de Gaulle, the French Armed Forces Epidemiology and Public Health Center (CESPA) carried out an investigation (January - April 2020) whose objectives were: to identify the possible routes of introduction of the virus ; to describe the characteristics of the epidemic and to describe and model the dynamics of the epidemic's spread. A telephone survey was conducted. The biological diagnoses were transmitted by the medical antennas. A time/place/population analysis was carried out, as well as the description of the clinical pictures with their exposure factors. The instantaneous reproduction rate Rt of the epidemic was modeled. A spatial analysis of the epidemic on board was carried out. Forty-three viral genomes were sequenced and compared to the reference bases. 0f 1767 sailors, 1568 (89%) participated in the telephone survey and 1064 (67.9%) were confirmed cases. Four patient profiles have been described: asymptomatic (13.0%); non-specific symptomatic (8.1%); specific symptomatic (76.3%); severe cases (2.6%). In univariate and multivariate analysis, age, overweight and obesity were significantly associated with the risk of having a severe form. Smoking was a protective factor. The evolution kinetics of Rt was in favor of an introduction of the virus at the end of February with a reintroduction during the stopover in Brest. Analysis of viral genomes ruled out introduction and spread of a single strain. Despite the control measures taken, an epidemic occurred. The often pauci-symptomatic clinical pictures resulted in a delay in identification. CESPA was able to carry out this epidemiological investigation within a highly constrained timeframe, showing all the interest of its integrated public health model.