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Surveillance and Epidemiology of Leptospirosis in France

Leptospirosis is a zoonotic disease that is widespread worldwide. It remains largely underestimated due to the absence of specific symptoms. After an incubation period of about ten days, human leptospirosis presents with a highly variable clinical picture, ranging from the anicteric febrile form observed in the vast majority of cases to potentially fatal multi-organ failure, characterized by renal failure, visceral hemorrhage, and jaundice. Diagnosis is often delayed during the course of the infection. Leptospirosis is not a notifiable disease; national surveillance is passive and relies on the National Reference Center for Leptospira and its network of laboratories (Biomnis and Cerba laboratories, hospital laboratories).In 2014–2015, the number of cases doubled compared to previous years in metropolitan France, reaching a record incidence since 1920 (1 case per 100,000 inhabitants—Figure). The incidence in the French overseas departments (DOM), where leptospirosis is endemic, can be 50 times higher than in mainland France. For the 2011–2015 period, the Aquitaine, Franche-Comté, and Basse-Normandie regions were the most affected. The peak in cases usually occurs between August and September. More than 85% of documented cases had not traveled in the month prior to the onset of symptoms. The remaining cases reported travel to endemic regions (Southeast Asia, the Caribbean, or the Indian Ocean). Exposure and risk factors for cases considered autochthonous are primarily associated with spending time in rural environments and/or engaging in outdoor recreational activities, particularly water-based activities (swimming, kayaking, rafting, canyoning). Several cases of leptospirosis have been identified following exposure to pet rats. To date, the reasons for the emergence of the disease in mainland France, and in Europe as a whole, have not been clearly identified and are likely to be multifaceted (improved diagnostic testing, climate change, rodent overpopulation, increased recreational activity in natural areas).