Incidence of leptospirosis in the French armed forces from 2004 to 2018: Retrospective analysis.

Background: The French military personnel may be exposed to leptospirosis during their training or on duty on the field in continental France, and most of all, in intertropical areas in the French departments and in Africa. The aim of this study was to assess the incidence of leptospirosis from epidemiological surveillance and cases data from 2004 to 2018, and to propose tools to assess leptospirosis risk prior to any mission or leisure activity.

Method: A retrospective epidemiological study on leptospirosis cases among French Armed Forces was conducted. More data were collected for 2 clusters in Martinique, as most of leptospirosis cases among French military personnel were identified in Martinique.

Results: Eighty-eight cases of leptospirosis were reported, 15 cases in continental France and 73 cases in overseas (including 42 cases in the French West Indies). The global leptospirosis incidence rate in continental France was 0.3/100,000 person-years and in overseas 24/100,000 person-years with the higher incidence rate in Martinique (99/100,000 person-years) and in Mayotte (36.9/100,000 person-years). For the clusters in Martinique, between January and June 2009, 7 cases were declared; between 2016 and 2018, 16 cases were reported, high proportions of severe cardiac, renal and neurological forms (6/16) and hospitalizations (9/16).

Conclusion: The occupational risk is real in French Armed Forces, particularly in malaria-free intertropical areas where chemoprophylaxis by doxycycline is not applied. Prevention can be optimized by the use of practical tools such as tables and cartographies, leading to a better leptospirosis risk assessment and application of preventive recommendations.