Key Points

In 2024, 202 cases of Legionnaires' disease were reported in the Grand Est region.

• The notification rate was 3.6 cases per 100,000 inhabitants, making it the third region with the highest notification rate. It has decreased compared to 2023 but remains higher than in 2022.

• Significant disparities exist between departments, with cases primarily concentrated in Bas-Rhin, Haut-Rhin, and Moselle; however, the departments of Meuse and Ardennes have the highest notification rates (number of cases relative to the resident population in the departments).

• The characteristics of the cases (mostly men, median age of 70) are comparable to previous years, and the majority of cases are hospitalized.

• The case fatality rate is 8% (16 deaths), comparable to previous years.

• In 91% of cases, the diagnosis was made by urine antigen testing, which remained the most common diagnostic method.

• A Legionella strain was isolated in 42 cases (21%), leading to a comparison of clinical and environmental strains in 9 cases, 6 of which were found to be identical, allowing the source of contamination to be identified.

• One cluster of cases was investigated.

• No risk exposure was reported through mandatory reporting for 66% of cases.

• The study on sporadic cases of Legionnaires’ disease and exposure in the home (LEGIODOM), led by the National Legionella Reference Center in collaboration with Santé publique France, began on October 1, 2024; its objective is to document the proportion attributable to contamination of domestic water systems. It will last two years.