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Reports of mosquito-borne diseases spreading in France are increasing this year, as a number of outbreaks impact the country. 

This includes native cases (people infected after not leaving mainland France in the previous 15 days) of dengue fever as well as chikungunya. 

There have also been over 3,000 imported cases of the two viruses recorded this year, where people have contracted the disease after travelling outside of mainland France.

These diseases, alongside zika, are spread by tiger mosquitoes, a relatively new insect in France now found across all mainland regions. 

Recently, a report of native West Nile virus was recorded near Paris, the most northerly destination in France where it has been found. It follows the report of a native case in the south of France earlier in the summer.

This disease is spread by the common Culex mosquito native to France, but is largely asymptomatic with humans being ‘accidental hosts’ so can be difficult to trace.

Cases of all of these diseases must be reported to national health authorities, who undertake schemes such as mosquito-destroying raids in an attempt to stop their spread.

Below, we review the figures of native and imported cases of chikungunya and dengue fever.

Imported Cases

These are cases where someone has picked up an illness after travelling outside of mainland France in the 15 days before falling sick.

An outbreak of chikungunya in the French overseas territory of Réunion has contributed to particularly high numbers this year.

The figures above equate to a total of 867 cases of chikungunya and 659 cases of dengue across France between May 1 and July 29, 2025.

The regions of Grand Est, Occitanie, and Provence-Alpes-Côte d'Azur also each recorded one case of Zika, meaning an overall total of three cases were recorded in France during the time period.

As a reminder, from January 1 to April 30, 2025, the following cases were identified through mandatory reporting: 

• 1,099 imported cases of dengue 

• 919 imported cases of chikungunya 

• 5 imported cases of zika

In 2024, 4,683 imported cases of dengue fever were recorded, as were 34 cases of chikungunya and eight cases of zika.

Native Cases

The number of native cases of chikungunya in the period of May - July 2025 reached 47. This is a major jump compared to 2024, which saw only one – the first – native case of chikungunya in mainland France.

Several ‘episodes’ of chikungunya (one or several cases clustered together in close proximity) have been tentatively linked to an imported form of the virus from Réunion then spread to tiger mosquito populations already present in France.

There were also three native cases of dengue fever in Provence Alpes-Côte d'Azur and another three cases in Auvergne Rhône-Alpes. 

This points to a total set to be considerably lower than in 2024, when over 80 native cases were recorded.