Key Points

In 2024, 223 cases of Legionnaires’ disease were reported in the Provence-Alpes-Côte d’Azur (PACA) region.

• The notification rate1 was 4 cases per 100,000 inhabitants, making it the region with the highest notification rate. It was lower than in 2023 and comparable to 2022.

• Significant disparities exist between departments. The highest notification rates were observed in the Alpes-Maritimes and Bouches-du-Rhône departments, at 5.6 and 4.1 per 100,000 inhabitants, respectively.

• The characteristics of the cases (mostly men, median age of 68) were comparable to previous years.

• The case fatality rate was 5.9% (13 deaths), lower than in previous years.

• The diagnosis was made in 95% of cases by urine antigen testing.

• A Legionella strain was isolated in 44 cases (20%).

• Risk exposure was reported in 37% of cases, mostly associated with travel.

• The study on sporadic cases of Legionnaires’ disease and household exposure (LegioDom) began on October 1, 2024; its objective is to document the proportion attributable to contamination of household water systems, and it will last two years. In the region, as of November 30, 2025, 74 cases had already been included in the study, and several matches between clinical and environmental strains were found.