Outbreaks of mosquito-borne diseases surge in France this summer

More than 300 native cases of tropical mosquito-borne diseases were recorded in France this summer, the highest level to date.

Between May 1 and September 2, 44 episodes of either chikungunya or dengue fever were registered in mainland France, states health authority Santé Publique in its latest report.

Each episode corresponded to an outbreak of the diseases and can relate to one or multiple cases – for example, one chikungunya episode in Fréjus (Var) led to 47 cases. 

Overall, 301 native cases of chikungunya were identified, alongside 19 native cases of dengue fever during the summer period. 

This is far higher than the levels seen in 2024, when 127 native cases were recorded.

These ‘native’ cases are recorded when an individual contracts a disease despite not leaving France for at least 15 days prior. This means they were infected by a mosquito in mainland France. 

Alongside these native cases, between May 1, 2025 and September 2, 2025 there were close to 2,000 imported cases, where someone contracted the disease outside of mainland France and then brought it back:

• 957 imported cases of chikungunya

• 862 imported cases of dengue

• 7 imported cases of Zika virus 

Taken with reports from the beginning of the year, it means several thousand cases of the diseases, both imported and native, have been recorded in 2025 in mainland France. 

These tropical diseases are spread by tiger mosquitoes, insects which are now present across all regions of France. 

In addition, 20 native cases of West Nile virus – spread by the Culex mosquito indigenous to France – were recorded over the same time period. 

This included cases in Paris, the first time the disease had been recorded in the capital.

Doctors in France are required to report any suspected cases of the disease to health authorities.

Symptoms can vary – our previous articles on chikungunya and dengue fever outline the most common – however attempting to reduce the threat of tiger mosquito bites is paramount. 

This can be done by destroying breeding grounds in stagnant water, using mosquito traps, and wearing long, loose-fitting clothing.

Further tips offered by Connexion readers can be found here. 

Cases across several regions

Outbreaks were located in southern regions of Provence-Alpes-Côte-d’Azur, Corsica, Occitanie, and the Auvergne-Rhône-Alpes, where they have also been recorded in previous years. 

However, for the first time this year native cases were recorded in Nouvelle-Aquitaine, Grand-Est, and Bourgogne-Franche Comté. 

The high number of imported cases of chikungunya from the French overseas department of Réunion is in part responsible for the high number of native cases this year. 

People infected with the disease when abroad can return to France and be bitten by a tiger mosquito, which itself becomes a vector to spread the disease.

“With the persistence of active clusters, particularly in tourist areas in the south of France, and the return from summer holidays, the risk of secondary clusters in other regions of France is increased,” said the health authorities. 

This means further cases are possible.

A map showing the location of all clusters recorded this year is available on the Santé Publique website, by downloading the PDF containing the official data.

Outside of France, Italy and Portugal are the only other European countries to record native cases of either dengue fever or chikungunya, according to the European Centre for Disease Prevention and Control.