Key Points

• Increase in the number of reported cases of Legionnaires' disease among residents of Nouvelle-Aquitaine in 2023 (n=167) compared to 2022 (n=158), with a record number of cases recorded.

• The increase in the number of cases in 2023 was driven primarily by the Gironde department, where the number of cases tripled compared to 2022 (59 in 2023 vs. 19 in 2022).

• The Nouvelle-Aquitaine region, like other regions in mainland western France, remains less affected than regions in the east (west-east gradient). The standardized notification rate is 2.4 per 100,000 inhabitants, compared to 3.2 for mainland France.

• Characteristics of Legionnaires’ disease cases are comparable to those observed in France and in previous years: a higher number of reported cases among men (M/F sex ratio = 2.5) and an increase in incidence with age.

• A slight decrease in the proportion of strains isolated from lower respiratory tract samples, which allows for linking cases to one another and identifying the source(s) of contamination.