First case of West Nile virus transmitted this year identified in southern France
The virus follows a different transmission cycle from dengue, chikungunya and Zika
Published
The first locally acquired case of West Nile virus has been confirmed in mainland France, with the infection identified in the Pyrénées-Orientales (Occitanie).
The case was announced by Santé publique France in its latest weekly arbovirus surveillance bulletin, and is the first evidence of human West Nile virus circulation in France during the 2026 mosquito season.
The patient developed symptoms on June 30 and is believed to have been infected locally, meaning they had not recently travelled to an area where the virus is circulating.
Unlike dengue, chikungunya and Zika, which are spread in mainland France by the invasive Asian tiger mosquito (Aedes albopictus), West Nile virus is transmitted by common mosquitoes of the Culex genus, which are found throughout France.
These mosquitoes are mainly active from dusk until dawn, while the tiger mosquito is active both in the morning and late afternoon.
Additionally, the disease follows a different cycle from those transmitted by tiger mosquitoes. The virus circulates between birds and Culex mosquitoes. Humans and horses can become infected after being bitten by an infected mosquito, but they do not carry enough of the virus to pass it on if bitten by other mosquitoes, so they do not contribute to further spread.
Earlier this year the Provence-Alpes-Côte d'Azur regional health agency (ARS Paca) confirmed that all six departments in the region are now colonised by tiger mosquitoes, although not every commune is affected.
No locally transmitted cases have been reported for dengue, chikungunya or Zika although imported infections continue to be detected.
Since May 1, 215 imported cases of dengue, 69 of chikungunya and nine of Zika have been identified.
What are the symptoms ?
Around 80% of people infected with West Nile virus have no symptoms. Then from those who do become ill, most develop a mild flu-like illness, which can also include fever, headache, muscle and joint pain, fatigue and a skin rash.
Only around 1% of infections develop into severe neurological disease such as meningitis or encephalitis. People with weaker immune systems as well as older people are usually more at risk.
How to reduce your risk of mosquito bites
Although West Nile virus is spread by common Culex mosquitoes rather than tiger mosquitoes, many of the same precautions apply:
Remove stagnant water from around homes and gardens, including plant pots, buckets, watering cans and blocked gutters, to reduce mosquito breeding sites.
Wear long, loose-fitting clothing, especially in the evening when Culex mosquitoes are most active.
Install mosquito screens or mosquito nets where possible.
Consult a doctor if you develop symptoms such as fever, headache, muscle or joint pain after mosquito bites, particularly if you have recently travelled abroad.
