Key Points

Chikungunya, Dengue, and Zika

Indigenous Cases

As of August 24, 2026, 11 outbreaks (+5 compared to the previous week) of locally transmitted vector-borne disease have been identified in mainland France:

• 7 outbreaks (+4) of chikungunya totaling 33 cases (1 to 19 cases per outbreak) in the Tarn, the Lot (Occitanie), the Gironde (Nouvelle-Aquitaine), and the Val-de-Marne (Île-de-France);
• 4 outbreaks (+1) of dengue, totaling 5 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 these various
outbreaks.

Imported cases

From May 1, when enhanced surveillance began, through August 23, 2026, the following were identified:

• 117 imported cases of chikungunya
• 328 imported cases of dengue
• 11 imported cases of Zika

West Nile virus infections

Locally acquired cases

As of August 24, 2026, 30 locally acquired cases (+12 compared to the previous week) of West Nile virus infection had been identified in mainland France. These cases are located in the Provence-Alpes-Côte d'Azur (3 departments), Occitanie (4 departments), Île-de-France (5 departments), and Auvergne-Rhône-Alpes (Drôme department) regions.

This is the first time that human cases of West Nile virus infection have been detected in the departments of Aude (Occitanie), Seine-et-Marne (Île-de-France), and Drôme (Auvergne-Rhône-Alpes).