Key Points

Chikungunya, Dengue, and Zika

Indigenous cases

As of September 22, 2025, 76 outbreaks of locally transmitted chikungunya and dengue and a total of 603 cases have been identified in mainland France:

• 570 cases of chikungunya spread across 65 outbreaks (1 to 103 cases per outbreak; 21 of these outbreaks are closed)

• 24 cases of dengue fever spread across 11 outbreaks (1 to 5 cases per outbreak; 8 of these outbreaks have been resolved)

• 8 isolated cases of chikungunya and 1 isolated case of dengue for which the exact site of infection could not be identified

The locally acquired cases are located in the Auvergne-Rhône-Alpes, Corsica, Île-de-France, Occitanie, and Provence-Alpes-Côte d'Azur regions, which were already affected in previous years, and for the first time this year in Bourgogne-Franche-Comté, Centre-Val de Loire, Grand Est, and Nouvelle-Aquitaine.

Imported cases

• 993 imported cases of chikungunya

• 939 imported cases of dengue

• 10 imported cases of Zika

West Nile virus infections

Local cases

As of September 22, 2025, 36 human cases of vector-borne West Nile virus infection have been identified in 11 departments of mainland France. The affected regions are Provence-Alpes-Côte d'Azur, Occitanie, and, for the first time, Île-de-France and Auvergne-Rhône-Alpes.