Key Points

In 2025, in France, 1,989 cases of Legionnaires' disease were reported to Santé publique France, with:

• an overall stable number of cases compared to 2024 (+50 cases, +2.6%),
• a reporting rate of 2.8 cases per 100,000 residents for cases residing in France, which remained generally stable compared to 2024,
• cases with characteristics comparable to those of previous years,
• regions with higher reporting rates: Auvergne-Rhône-Alpes (4.1 cases per 100,000 inhabitants) and Provence-Alpes-Côte d’Azur (4.0 cases per 100,000 inhabitants),
• 187 deaths (9.4% of cases died),
• 71% were men (sex ratio: 2.5),
• 90% of cases were initially diagnosed using a urinary antigen test,
• a positive PCR test on a respiratory specimen in 40% of cases,
• the source of infection identified in 61 cases through genomic matching of clinical and environmental strains,
• an outbreak of 7 cases in which a wastewater treatment plant (WWTP) was identified as the most likely source of infection,
• 57% of cases had no reported risk exposure according to mandatory reporting.

Continuation of the LEGIO-DOM exploratory study aimed at documenting the proportion of Legionnaires’ disease cases that may be linked to household contamination via water distribution systems, with the participation of regional health agencies (ARS) from all regions of mainland France except Occitanie.