More than 300 cases of chikungunya in mainland France since this summer, an unprecedented level

Public Health France (SPF) reported an unprecedented summer season for mosquito-borne diseases on Wednesday, September 3. According to the latest data published by the health agency, more than 300 cases of chikungunya have been recorded in France this summer.

As of September 2, "34 episodes of chikungunya totaling 301 cases" have been identified, it is specified in the weekly report of SPF, thus highlighting four new episodes of transmission of this viral disease.

While several episodes are now over, the summer of 2025 is of unprecedented magnitude in mainland France for indigenous cases of chikungunya, the virus of which is transmitted from one human to another by tiger mosquito bites.

The large number of chikungunya outbreaks and their early onset are partly linked to the large-scale epidemic that hit Réunion and the Indian Ocean region and encouraged the arrival of imported cases, which then led to contamination on the European continent.

The spread of chikungunya is also taking place in a context where the tiger mosquito, which was absent from France a few decades ago, is now established almost everywhere, against a backdrop of global warming. Another disease transmitted by the tiger mosquito and on the rise, dengue fever, has so far caused ten summer outbreaks in mainland France, for a total of 19 cases, without reaching the record of 2024 (66 cases).

The cases of chikungunya and dengue fever identified this summer are located in the Provence-Alpes-Côte d'Azur (PACA), Corsica, Occitanie, Auvergne-Rhône-Alpes regions, already affected in previous years, and, for the first time this year, in the Grand Est, Nouvelle-Aquitaine and Bourgogne-Franche-Comté.

"With the persistence of active outbreaks, particularly in tourist areas in the south of France, and the return of summer holidays, the risk of secondary outbreaks in other regions of France is increased," notes Public Health France.

Another disease under increased surveillance: West Nile fever, which is not transmitted by the tiger mosquito but by the Culex variety, more common in mainland France.

With 20 indigenous cases identified, no record has been broken so far this summer in mainland France, but their location confirms growing transmission outside the historical Mediterranean arc. In addition to those in PACA and Occitanie, several cases have been identified in Île-de-France and Auvergne-Rhône-Alpes for the first time.