Key Points

• In 2023, 74 cases of Legionnaires' disease were reported in the Centre-Val de Loire region, representing a notification rate of 2.7 per 100,000 inhabitants, compared to 3.2 per 100,000 inhabitants nationally.

• A 23% increase in the number of reported cases in 2023 compared to 2022.

• Higher notification rates in the departments of Loir-et-Cher and Loiret (5.2 per 100,000 inhabitants and 4.2 per 100,000 inhabitants, respectively).

• Higher reporting rates among men than among women (male-to-female ratio = 2.7) and increasing with age. Nevertheless, characteristics comparable to previous years and those observed in France.

• Case fatality rate of 9.5% in 2023, up from the previous year.

• An upward trend in PCR-based diagnoses in recent years, but a decline observed in 2023 with 12% of PCR tests positive.

• In 2023, for nearly 40% of cases, a risk exposure was reported, a proportion stable compared to previous years. The distribution of reported types of risk exposures was similar to previous years

• 16 cases with isolated strains, representing 22%, a rate lower than that reported nationally.

• Given the low number of isolated strains in the region, it is worth noting that the collection of respiratory specimens by clinicians is important in that it allows for the detection of species and serogroups other than Lp1 (not detected by urine tests), the identification of clustered cases, and the identification of the source of contamination (by comparing clinical and environmental strains).