Key Points

Chikungunya, Dengue, and Zika

Indigenous Cases

As of September 21, 2026, 17 outbreaks (no new outbreaks compared to the previous week) of locally transmitted vector-borne disease were identified in mainland France:

• 13 chikungunya outbreaks (no new outbreaks compared to the previous week) totaling 90 cases (1 to 30 cases per outbreak) in the Tarn and the Lot (Occitanie), in Gironde, in the Landes (Nouvelle-Aquitaine), and in Val-de-Marne (Île-de-France);
• 4 dengue outbreaks (no new outbreaks compared to the previous week) totaling 6 cases (1 to 2 cases per outbreak) in the Tarn, the Hérault (Occitanie), the Dordogne (Nouvelle-Aquitaine), and the Bouches-du-Rhône (Provence-Alpes-Côte d'Azur).

Investigations and prevention and control measures are underway for the various outbreaks that are still active.

Imported Cases

From May 1, when enhanced surveillance began, through September 20, 2026, the following were identified:

• 150 imported cases of chikungunya
• 412 imported cases of dengue
• 15 imported cases of Zika

West Nile virus infections

Locally acquired cases

• As of September 21, 2026, 117 locally acquired cases of West Nile virus infection (+25 compared to the previous week) have been identified in mainland France. These cases are located in the Provence-Alpes-Côte d'Azur region (3 departments), Occitanie (5 departments), Île-de-France (6 departments), Auvergne-Rhône-Alpes (3 departments), Nouvelle-Aquitaine (Gironde department), Pays de la Loire (2 departments), and Centre-Val de Loire (Loiret department). For 11 cases, no specific site of infection could be identified.
• For the first time, human cases of West Nile virus infection have been detected in the departments of Aude (Occitanie), Seine-et-Marne (Île-de-France), Drôme, Rhône, and Isère (Auvergne-Rhône-Alpes), Loire-Atlantique, Maine-et-Loire (Pays de la Loire), and Loiret (Centre-Val de Loire).