Health. Chikungunya: Nearly 400 indigenous cases in mainland France since May. What are the main outbreaks?

Unprecedented scale. Nearly 400 indigenous cases of chikungunya have been recorded in France since the beginning of May: the summer of 2025 is going from record to record for this disease transmitted by tiger mosquitoes, according to data published this Wednesday by Public Health France, which recorded 81 additional cases in one week.

As of September 8, "38 episodes of chikungunya totaling 382 cases " have been identified in metropolitan France, the health agency summarized in a weekly report. A first indigenous case was reported in Paris, and a mosquito control operation, led by the Regional Health Agency, is planned for the night of Wednesday to Thursday, according to the city hall of the 11th arrondissement of the capital. While several episodes are now over, the summer of 2025 is of unprecedented magnitude in metropolitan France for indigenous cases of chikungunya, whose virus is transmitted from one human to another via tiger mosquito bites and causes fever and joint pain.

The main outbreaks are located in Antibes in the Alpes-Maritimes with 71 cases, Bergerac in the Dordogne (54), Fréjus in the Var (51) and Vitrolles in the Bouches-du-Rhône (46). The large number of chikungunya outbreaks in mainland France and their early occurrence is partly linked to the major epidemic that raged in Réunion and the Indian Ocean region and encouraged the arrival of imported cases, which then favored contamination in mainland France.

The expansion of chikungunya also takes place in a context where the tiger mosquito, still absent from mainland France a few decades ago, is now established in 81 departments, against a backdrop of global warming. Also transmitted by the tiger mosquito and on the rise, dengue fever has so far been the center of eleven transmission hotspots in mainland France, for a total of 21 cases, without reaching the 2024 record (66 cases).

Another disease under increased surveillance: West Nile fever, transmitted by the Culex mosquito. With 23 indigenous cases now identified, there have been no records broken so far this summer, but their location confirms increasing transmission outside the historical Mediterranean arc. And, since the start of increased surveillance of mosquito-borne diseases in early May, there have been 966 imported cases of chikungunya, 894 of dengue fever, and seven of Zika.

Dengue and chikungunya could become endemic in Europe due to global warming, urbanization and travel, all factors that promote the spread of the tiger mosquito, according to a study published in mid-May in the Lancet Planetary Health .