Key Points

• In 2024, 83 cases of Legionnaires' disease were reported in the Normandy region, representing a 19% increase compared to 2023;

• The notification rate was 2.4 cases per 100,000 inhabitants, lower than the national average but up from 2023, reaching its highest level since 2010;

• At the departmental level, the Eure department had the highest notification rate, consistent with trends observed in previous years;

• Case characteristics (predominantly male, median age of 64) were comparable to those of previous years;

• The case fatality rate was 12.5% (10 deaths), an increase compared to previous years and higher than the national average (case fatality rate of 8.9%);

• Diagnosis was based primarily on antigen detection, used in 89% of cases, and remained the most common diagnostic method;

• A Legionella strain was isolated in 29 cases (35%), allowing for a comparison between clinical and environmental strains in two cases, with no evidence of concordance;

• No clusters of cases were investigated;

• Risk exposure was reported in 30% of cases, primarily associated with travel;

• The study on sporadic Legionnaires’ disease cases and household exposure (LEGIODOM) began on October 1, 2024; it aims to estimate the proportion attributable to contamination of household water systems and will run for a period of 2 years.