Indigenous cases of chikungunya continued to rise in mainland France in early October, but the rate of increase appears to be stabilizing, with 2025 already an unprecedented year in this regard, the public health agency summarized on Wednesday.
As of September 29, 708 cases of chikungunya, spread across 75 outbreaks, have resulted from contamination in mainland France since the beginning of May, compared to 642 the previous week, Public Health France indicates in its weekly report.
The summer of 2025 proved unprecedented in terms of the spread of chikungunya, a disease transmitted by the tiger mosquito and with symptoms similar to those of the flu, in mainland France. Until then, there had never been more than a few dozen cases recorded per year.
This year, a major epidemic in Réunion and the Indian Ocean region contributed to the arrival of imported cases, which then fueled contamination in mainland France. But, more generally, global warming is facilitating the establishment of the tiger mosquito in regions where it was absent several decades ago.
The rate of increase in cases now appears to be stabilizing, with each of the last few weeks seeing the recording of around sixty new cases.
Another disease transmitted by this mosquito, dengue fever, continues to cause a few indigenous cases, but the scale is much lower (28 cases) and does not reach the record of 2024 (66 cases), according to the latest report.
For these two diseases, "the indigenous cases are located in the Auvergne-Rhône-Alpes, Corsica, Île de France, Occitanie, Provence-Alpes-Côte d'Azur regions, already affected in previous years, and for the first time this year in Bourgogne-Franche Comté, Centre-Val de Loire, Grand Est and Nouvelle-Aquitaine," recalls Public Health France, with no new regions being reported compared to previous weeks.
Also under increased surveillance: West Nile fever, transmitted by the Culex mosquito via an infected bird, has a growing number of indigenous cases in France, with 44 identified at the end of September.
Only one case, a man over 80 years old with comorbidities, died, a situation already known the previous week.
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