The leptospirosis surveillance system led by Santé publique France and the National Reference Center for Leptospirosis (CNR, Institut Pasteur) enables the study of the epidemiological trends and characteristics of this disease. Until the end of 2023, this system relied on diagnostic data from the CNR and its network of laboratories. Since August 2023, leptospirosis has been included on the list of notifiable diseases, making it mandatory to report all diagnosed cases of leptospirosis throughout the country. Surveillance results now come from mandatory reporting data.

In 2024, 886 cases of leptospirosis were reported in France, including 441 in mainland France and Corsica, and 445 in the Overseas Departments and Regions (DROM). Among these cases, 74% required hospitalization, and 13 deaths were recorded, highlighting the potential severity of this zoonosis. The most commonly identified risk exposures were linked to gardening, farming, swimming in freshwater, and contact with animals. This highlights the importance of enhanced surveillance and greater awareness among people engaging in these high-risk activities.

Significant geographical disparities across regions in mainland France

Reporting rates were highest in the regions of Brittany (1.1 cases per 100,000 inhabitants), Burgundy-Franche-Comté (1.1), New Aquitaine (1.0), Pays de la Loire (1.0), and Auvergne-Rhône-Alpes (0.9).

However, the case notification rate was highest in the departments of Hautes-Pyrénées (3.4 per 100,000 inhabitants), Doubs (3.3), Savoie (2.7), Lozère (2.6), and Ariège (2.6).

These differences may be related to the ecosystem, climate, and diversity of potential reservoir species, as well as to the activities and lifestyles of the population. They may also be related to the level of awareness among healthcare professionals regarding the diagnosis and reporting of leptospirosis cases.

Higher incidence in the DROMs, but few cases reported through mandatory reporting

The French Overseas Departments and Regions (DROM) accounted for nearly half of the reported national cases, with 445 reports in 2024.

However, the number of reported leptospirosis cases likely underestimates the actual number of cases. Due to exceptional epidemiological situations that mobilized stakeholders (cholera outbreak in Mayotte, arbovirus outbreaks in the Antilles, etc.), the effective implementation of mandatory reporting was delayed. Regional bulletins, including additional data, are available:

• Leptospirosis in the Antilles. 2024 Report.

• Health surveillance in Réunion. Update as of July 4, 2024.

• Leptospirosis in Mayotte. Bulletin of November 28, 2024.

• Leptospirosis in French Guiana. 2024 Report.