Key Points

In 2024, 304 cases of Legionnaires' disease were reported in the Auvergne-Rhône-Alpes region.

• The notification rate was 3.7 cases per 100,000 inhabitants, making it the region with the second-highest notification rate. It has been declining over the past three years.

• Significant disparities exist between departments, with higher reporting rates in the eastern departments of the region.

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

• The case fatality rate was 8% (23 deaths), comparable to previous years.

• The diagnosis was made in 89% of cases by urine antigen testing, which remained the most common diagnostic method.

• A Legionella strain was isolated in 78 cases (26%), leading to a comparison of clinical and environmental strains in 19 cases, 17 of which were found to be identical, allowing the source of contamination to be identified.

• No high-risk exposure sites were reported through mandatory reporting for 60% of cases.

• The study on sporadic cases of Legionnaires’ disease and exposure in the home (LEGIODOM) began on October 1, 2024; its objective is to document the proportion attributable to contamination of household water systems, and it will last for two years.