West Nile virus cases in France approach 180 amid wider regional spread

16:47

By: Azzat Manal

West Nile virus cases in France approach 180 amid wider regional spread

France has recorded 178 locally acquired cases of West Nile virus this year, nearly three times the total reported in 2025, according to figures cited by French media. The increase has raised concerns among health authorities, particularly after infections were identified in Auvergne-Rhône-Alpes, a region that had not previously reported locally acquired cases during the current season.

A regional health bulletin published in early October identified five infections in the area, with patients developing symptoms in August or early September. The cases were reported in four departments: two in Drôme and one each in Rhône, Ain and Isère. According to Santé publique France, three of the five patients developed neuro-invasive forms of the disease, which can affect the brain and nervous system.

Although most West Nile virus infections do not cause noticeable illness, severe cases can lead to serious neurological complications. Health authorities estimate that around 80% of infected people remain asymptomatic, while approximately one in five develops symptoms resembling the flu, including fever, headache and muscle pain. Neurological disease occurs in fewer than 1% of infections but may result in lasting disability or death.

The virus's growing presence represents a marked increase compared with the previous year. France recorded 62 locally acquired infections between early May and late November 2025, alongside five reported deaths. With 178 cases identified so far this year, the current season has been described by the French Agency for Food, Environmental and Occupational Health and Safety as one of particularly intense circulation.

Several areas have reported infections, including Bouches-du-Rhône, Vaucluse, Var, Haute-Garonne and the Paris region. Cases have also been detected in horses across multiple departments, including Drôme, highlighting the circulation of the virus among animals as well as humans. Veterinary infections can provide additional information for monitoring the spread of the disease.

West Nile virus is transmitted primarily through the bites of infected mosquitoes. Birds serve as the main reservoir of the virus, while mosquitoes can carry it to humans and other animals after feeding on infected birds. Humans are generally considered incidental hosts and do not usually contribute significantly to the virus's transmission cycle.

There is no routine person-to-person transmission. However, infection can occur in exceptional circumstances, including through blood transfusions or organ transplants, which is why screening and surveillance measures are important. The virus is not transmitted from one person to another through a mosquito that has bitten an infected human.

The rise in cases and the appearance of infections in new areas have reinforced the importance of epidemiological monitoring, mosquito control and public awareness. Health authorities are particularly attentive to neurological symptoms, which require prompt medical assessment. While severe disease remains uncommon, the expansion of West Nile virus activity makes continued surveillance essential throughout the transmission season.