Locally transmitted West Nile virus case confirmed in south of France
Disease recorded in the Var. It is the first such case in France in 2025
The West Nile virus is transmitted by culex mosquitoes which bite in the night
Babul Hosen/Shutterstock
The first indigenous case of the West Nile Virus in France in 2025 has been confirmed by regional health authorities in the south of France.
The disease, spread by common Culex mosquitoes found across France, was reported in Hyères (Var) on July 30 by the Santé publique France. The case was recorded on July 15.
It follows several indigenous cases of dengue fever and chikungunya, spread by tiger mosquitoes that are now rampant in France.
Last year, 34 indigenous cases of the West Nile virus were reported in France, all in Provence-Alpes-Côte-d’Azur and Nouvelle-Aquitaine in the south and south-west.
An ‘indigenous’ or native case is one where a person has not travelled in the last 14 days, and thus has picked up the disease from a mosquito within France.
Health authorities report that so far in 2025 there have been 14 native episodes of chikungunya in mainland France (each comprising one to 13 cases) and five native episodes of dengue fever (each comprising one to two cases).
West Nile virus is spread by common mosquitos and can be fatal
The West Nile virus is different to other tropical diseases such as Dengue and Zika in that it is spread by common mosquitoes found all over France and not by more recent arrivals tiger mosquitoes.
Unlike tiger mosquitoes, Culex variants of the insect tend to feed at night meaning bites can often go unnoticed.
In around 80% of cases, the West Nile virus is asymptomatic, making an outbreak hard to spot.
In remaining cases, West Nile fever patients show symptoms such as fever, headache, vomiting, and rashes.
In roughly 1% of cases, brain swelling or meningitis occurs, alongside neck stiffness, confusion, and seizures.
In this final group, the mortality rate from the virus is around 10%.
Mosquitoes can only become ‘infected’ with West Nile by drawing blood from a bird infected with the virus before passing it on.
In addition, humans and horses are ‘accidental hosts’ of the virus, and cannot transmit it themselves.
Both of these factors help limit the spread of the virus.
Unlike with episodes of other tropical diseases, a mosquito elimination squad is not being deployed in the area where the disease was recorded.
