Var. Chikungunya: a first indigenous case detected in metropolitan France

The first indigenous case of chikungunya in mainland France for 2025 was detected on Wednesday in the Var region, in the commune of La Crau, the Provence-Alpes-Côte d'Azur Regional Health Agency announced in a press release on Friday.

Only one indigenous case of this virus transmitted by the tiger mosquito had been detected in 2024 in mainland France, in Ile-de-France, and none in 2023. Since 2010, mainland France had experienced around thirty indigenous cases of this virus.

Until now, since the beginning of the year, all cases of chikungunya recorded in mainland France came from contamination outside the territory, mainly in Réunion, this French island in the Indian Ocean which has been hit for several months by an epidemic of this virus unprecedented in twenty years.

"Immediate measures are being implemented to limit any risk of spread," assured the ARS Paca, mentioning in particular mosquito control carried out in the commune, "on public roads and in private gardens located around the case," in order to eliminate larval breeding sites and adult mosquitoes as quickly as possible.

Similarly, a door-to-door survey will be conducted in homes in the affected neighborhood to identify people who may be exhibiting symptoms. A native case is defined as a person who contracted the disease on national territory and has not traveled to an infected area in the 15 days prior to the onset of symptoms.

This year, the chikungunya epidemic, a disease that causes fever and joint pain, has hit Reunion Island the hardest , with 23 deaths, although it is now continuing to decline. It is estimated that 200,000 people have been infected on the island since January.

While the epidemic is clearly declining in Réunion, it is still gaining momentum in Mayotte, also in the Indian Ocean, where it broke out later. According to the latest report, 746 cases have been reported since the beginning of the year, but this figure likely appears to be an underestimate.

The warmer temperatures currently affecting France are favoring the activity of tiger mosquitoes, vectors of this virus as well as those of dengue and Zika. In 2024, there were also 83 indigenous cases of dengue in mainland France, between the Provence-Alpes-Côte d'Azur, Occitanie, and Auvergne-Rhône-Alpes regions.

Having appeared in mainland France in 2004, the tiger mosquito is in any case continuing its rapid expansion across the country, particularly towards the north: at the start of 2025 it was present in 81 departments, or 84% of mainland departments, according to new data released in mid-May by Public Health France.

Dengue fever 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 the journal Lancet Planetary Health in mid-May.

Faced with this progression, and in an attempt to halt it, several thousand male tiger mosquitoes rendered sterile by X-rays were released in mid-May in Brive-la-Gaillarde (Corrèze), as part of an experiment of unprecedented scale in mainland France.

With this sterile insect technique (SIT), used for decades in the agricultural sector, the offspring of females, the only ones responsible for the bites, would gradually be neutralized and the populations should automatically decrease.