As of October 6, 2025, 87 outbreaks of indigenous vector-borne transmission of chikungunya and dengue fever and a total of 737 cases have been identified in mainland France:

• 695 cases of chikungunya spread across 75 outbreaks (1 to 128 cases per outbreak; 26 of these outbreaks are closed).

• 28 cases of dengue fever spread across 12 outbreaks (1 to 8 cases per outbreak; 9 of these outbreaks are closed).

• 13 isolated cases of chikungunya and 1 isolated case of dengue fever for which the precise location of contamination could not be identified.

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

The increase in outbreaks and the existence of secondary outbreaks are linked to the successful adaptation of the viral strain to the Aedes albopictus mosquito vector and to environmental conditions favorable to mosquito reproduction.

With the persistence of active outbreaks (particularly in tourist areas in southern France), the risk of secondary outbreaks in other regions of France remains high.

Diagnosis should be considered in the event of a fever upon returning from areas of chikungunya and dengue virus transmission, abroad, overseas, and also in mainland France.

Public Health France reiterates the importance of reporting cases, which allows for rapid intervention to limit transmission. Public Health France also reiterates the importance of protective measures against mosquito bites and the control of breeding sites.

Concerning imported arbovirus cases, since May 1st, the start of enhanced surveillance, and continuing through October 6, 2025, the following have been identified:

• 1,007 imported cases of chikungunya

• 974 imported cases of dengue fever

• 11 imported cases of Zika virus

As of October 6, 2025, 44 human cases of vector-borne West Nile virus infection have been identified in 14 departments of mainland France. The affected regions are Provence-Alpes-Côte d’Azur, Occitanie, Nouvelle-Aquitaine, and, for the first time, Île-de-France and Auvergne-Rhône-Alpes.

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