Key Points

In 2024, 56 cases of Legionnaires' disease were reported in the Pays de la Loire region:

• The regional notification rate¹ was 1.4 cases per 100,000 inhabitants, one of the lowest rates among French regions. It has decreased compared to 2023.

• Disparities exist between departments, with notification rates ranging from 1.1 cases of Legionnaires' disease per 100,000 inhabitants in Maine-et-Loire and Vendée to 2.7 cases in Sarthe. In 2024, Loire-Atlantique was the department with the highest number of cases residing in the Pays de la Loire region (17 cases), followed by Sarthe (16 cases).

• The characteristics of the cases (mostly men, median age of 72 years, presence of at least one risk factor) were comparable to previous years.

• The case fatality rate of 8% (4 deaths) was slightly lower than in previous years.

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

• A Legionella strain was isolated in 19 cases (34%), and a comparison of clinical and environmental strains was possible in 4 cases, 3 of which were found to be identical, allowing the source of contamination to be identified.

• A cluster of cases was identified and investigated in the Pays de la Loire region, but it was not possible to determine the source of contamination.

• Risk exposure was reported in 43% of cases, primarily 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 of Legionnaires’ disease cases attributable to contamination of household water systems, and it will last for 2 years.