Key Points

• In 2024, 189 cases of Legionnaires' disease were reported in the Occitanie region.

• The notification rate was 2.9 cases per 100,000 inhabitants, making it the 5th region with the highest notification rate. This is the highest Legionnaires’ disease notification rate in Occitanie over the past 15 years, and it has been steadily increasing since 2020.

• Significant disparities exist between departments, with standardized rates¹ ranging from 1.5 cases of Legionnaires' disease per 100,000 inhabitants in Lot to 4.2 cases in Hautes-Pyrénées. In 2024, Hérault was the department with the highest number of resident cases in Occitanie (45 cases), followed by Gard (35 cases) and Haute-Garonne (27 cases).

• The characteristics of the cases (mostly men, median age of 69 years) were comparable to previous years.

• The case fatality rate of 7% (10 deaths) was similar to that observed in previous years.

• The diagnosis was made in 86% of cases by urine antigen testing, the most common diagnostic method.

• A Legionella strain was isolated in 50 cases (27%), and a comparison of clinical and environmental strains was possible in only 3 cases, 2 of which were found to be identical, allowing the source of contamination to be identified.

• Two clusters of cases were investigated in the Occitanie region.

• Risk exposure was reported in 31% of cases, primarily associated with travel.

• A study of sporadic cases of legionellosis and their exposure at home (LEGIODOM) began on October 1, 2024. Its objective is to document the proportion of legionellosis cases attributable to contamination of household water systems, and it will last two years.