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As if chikungunya, dengue or zika – which can be caught with the tiger mosquito – were not enough, it is now necessary to be wary of another virus transmitted by the mosquito: the West Nile, or Western Nile virus. Usually located around the Mediterranean periphery, This virus has just been detected in Seine-Saint-Deniswhere two indigenous cases were identified by the health authorities, they announced this Wednesday, August 13, 2025.
“An unprecedented situation” in the region, reports our editorial staff Paris news. These are the “first identifications of local vector transmission of the virus in Île-de-France,” said Ars Île-de-France on Wednesday.
Several French departments affected
Last July, a first indigenous case of the Western Nile virus had been identified in France. Located in the Var, in Hyères, the individual had presented the first symptoms on July 15, according to the France Public Health Bulletin, detailed our editorial staff ACTU VAR. In 2024, three cases had already been spotted in this same department.
The West Nile or Western Nile virus was identified for the first time in 1937 in the West Nile district, Uganda. “It was historically Responsible for epidemics in Africain the Middle East, Western Asia and Europe. He appeared in North America for the first time in 1999 and he disseminated in a few years to the whole territory, ”explains Public Santé France. In France, he is regularly detected around the Mediterranean.
Present on several continents, the infection has known, since 2010, a extension progressive en Europeespecially in southern countries, with an increase in neuro-invasive forms.
How is the West Nile virus transmitted?
Birds are the first tank of the virus, but humans, horses and several other vertebrate species can also be contaminated.
Human transmission is carried out by the bite of a mosquitolike Culex, himself infected after having an infected bird.
“Man and the horse represent” epidemiological dead ends “for the West Nile virus, because the quantity of virus in the blood (viremic) is insufficient to infect the mosquito during a bite and thus allow the transmission of the disease,” continues the health agency.
What are the symptoms?
In almost 80 % of cases, The virus is asymptomatic. Symptomatic forms are characterized by:
- a brutal fever after 3 to 6 incubation;
- muscle pain;
- a cough;
- swelling of the neck nodes (lymphadenopathy);
- a rash;
- nausea;
- abdominal pain;
- diarrhea;
- respiratory symptoms.
Serious neurological complications
This arbovirus can be responsible, in less than 1 % of cases, for:
- Neurological complications
- meningitis
- encephalitis
- flange paralysis
- Guillain Barré syndrome
Other complications, even rarer, can occur:
- hepatitis
- pancreatitis
- myocarditis
“Generally, the patient recovers spontaneously, sometimes with sequelae. But viral infection can be deadly Mainly in senior adults, ”says the Pasteur Institute.
What treatment or vaccine?
It does not exist no treatment specific to the disease. Management is symptomatic.
The diagnosis can be confirmed by biological analyzes carried out in the blood and/or in the cerebro-spinal liquid (LCS), obtained by lumbar puncture.
No vaccine is available. The best way to protect yourself from the virus is the implementation of protective measures against mosquito bites: covering clothes, repellents, serpentine, electric diffusers, mosquito nets.
Collectively, it is necessary to fight against the larval lodges of mosquitoes.
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