West Nile virus: five people infected in Auvergne-Rhône-Alpes, including three with severe forms

Until now spared, the Auvergne-Rhône-Alpes region is experiencing its first human Nile virus infections, several of which have led to serious complications. Five indigenous cases have been identified, indicates the Regional Health Agency (ARS) in its bulletin at the beginning of October. The patients showed the first signs of infection during the month of August or at the beginning of September. Two cases were reported in Drôme, one in Rhône, one in Ain and one in Isère.

Three of them “presented neuro-invasive forms”, specifies Public Health France. If the infection is asymptomatic in 80% of cases, it manifests as a flu-like syndrome in one in five cases, with neurological manifestations in less than 1% of cases. “These neuro-invasive forms can progress to after-effects, or even death in 7 to 9% of cases,” indicate the authorities.

Five fatal cases in France last year

In 2025, the West Nile virus caused five deaths in France, out of the 62 cases of infection reported from the beginning of May to the end of November. It is circulating in a “particularly intense” manner this year, according to ANSES. A total of 178 indigenous cases have been recorded to date, almost three times more than last year. Bouches-du-Rhône, Vaucluse, Var, Haute-Garonne and the Paris region concentrate the most cases. Equine cases are also reported in several departments, including Drôme.

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The West Nile virus or WNV according to the English acronym is transmitted “accidentally” to humans via common mosquitoes, specifies Public Health France. “The main reservoir of infection is birds,” add the health authorities. There is no human-to-human transmission (apart from transfusions or transplants), nor human-to-human transmission of the virus via mosquitoes.