Investigation of a COVID-19 outbreak on the Charles de Gaulle aircraft carrier, March to April 2020: a retrospective cohort study.

BackgroundSARS-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.AimTo understand how the virus was introduced, circulated then stopped circulation, risk factors for infection and severity, and effectiveness of preventive measures.MethodsWe 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.ResultsThe 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).ConclusionNon-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.

Impact of Tobacco Smoking on the Risk of COVID-19: A Large Scale Retrospective Cohort Study.

INTRODUCTION: Preliminary reports indicated that smokers could be less susceptible to coronavirus SARS-CoV-2, which causes Covid-19. However, once infected an increased risk of severe disease is reported. We investigated the association between smoking and COVID-19 during an outbreak of the disease on a naval vessel. METHODS: We conducted a cross-sectional, observational study on the 1769 sailors of the same navy aircraft carrier at sea exposed at the same time to SARS-CoV2 to investigate the link between tobacco consumption and Covid-19. RESULTS: Among the 1688 crewmembers (87% men; median age = 28 [interquartile range 23-35]) included, 1279 (76%) developed Covid-19 (1038 [62%] reverse-transcriptase- polymerase chain reaction testing-positive and 241 [14%] with only clinical signs). One hundred and seven patients were hospitalized. The univariable analysis odds ratio (OR) for Covid-19 infection was 0.59 (95% confidence interval [CI], 0.45-0.78; p < .001) for current smokers versus former and nonsmokers; sex, body mass index or blood group had no significant impact. Crewmembers >50 years old had an increased risk of contracting Covid-19 (OR, 2.84 [95% CI, 1.30-7.5]; p = .01). Multivariable analysis retained the lower risk of current smokers becoming infected (OR, 0.64 [0.49-0.84]; p < .001) and age >50 years was significatively associated with Covid-19 (OR, 2.6 [1.17-6.9]; p = .03). CONCLUSIONS: Current smoking status was associated with a lower risk of developing Covid-19 but cannot be considered as efficient protection against infection. The mechanism of the lower susceptibility of smokers to SARS-CoV-2 requires further research. TRIAL REGISTRATION: IRB no.: 0011873-2020-09. IMPLICATIONS: (1) Recent epidemiologic data suggest a paradoxical link between smoking and COVID-19. (2) Among the 1688 crewmembers (with an attack rate of 76% and exposed at the same time in the same place to SARS-CoV2), we found a significantly lower risk for developing COVID-19 in current smokers (71%) versus former and nonsmokers (80%). This finding strongly supports the need for further research on nicotine physiological pathway and its impact on COVID-19 infection whilst emphasizing that tobacco smoking should not be considered as efficient protection against COVID-19.