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West Nile virus spreading in Europe - 56 cases in France this year
In three French departments the virus has been detected for the first time
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France has recorded 56 cases of locally-acquired West Nile virus this year, with cases being detected in several regions.
The figures from Santé publique France (France’s national health agency) amount to cases reported up until September 6 and mark an increase of 17 from the previous week and are already nearing the 2025 figures, where 62 locally acquired cases were recorded.
West Nile virus is transmitted through bites of infected Culex mosquitoes, which are different from the tiger mosquitoes that spread diseases such as dengue and chikungunya.
France’s prolonged heatwaves and dry conditions may have temporarily reduced mosquito activity, as extreme heat can make mosquitoes less active.
However, as temperatures fall in September, conditions may become more favourable again, especially if rain creates new breeding sites.
In Europe, the European Centre for Disease Prevention and Control (ECDC) reported 1,086 locally acquired human cases by September 3, with Italy, Greece and Spain among the countries reporting the largest numbers.
Where are the French cases?
Provence-Alpes-Côte d’Azur is currently the most affected region in France, with 23 cases.
Bouches-du-Rhône has recorded 10 cases, followed by Vaucluse with eight and Var with five.
Occitanie has recorded 11 cases: four in Pyrénées-Orientales, three in Gard, three in Haute-Garonne and one in Aude.
Île-de-France has 12 cases. These include four in Essonne, three in Seine-Saint-Denis, two in Val-de-Marne, two in Seine-et-Marne and one in Val-d’Oise.
There are also three cases in Gironde and one in Drôme. Then, for the remaining six cases, health authorities have not been able to identify a precise place of infection.
The latest figures also show the virus moving into areas where human infections had not previously been recorded. The cases in Aude, Seine-et-Marne and Drôme are the first human West Nile infections reported in those departments.
What is the West Nile virus?
West Nile virus is a mosquito-borne virus which mainly circulates between mosquitoes and birds. People and horses can become infected when bitten by an infected mosquito, but they are considered accidental hosts and do not normally pass the virus on to other mosquitoes.
In France, the virus is mainly transmitted by Culex mosquitoes which are widespread in mainland France and are mainly active from the evening into the night.
Most infections cause no symptoms
West Nile infection often goes unnoticed. About 80% of people infected develop no symptoms.
However, around 20% develop West Nile fever, which can cause a sudden fever, headache, tiredness, muscle or body aches and sometimes a skin rash or swollen glands.
In about 1% of infections, the virus can cause neurological complications such as meningitis or encephalitis. Older people and people with weakened immune systems are at greater risk.
Anyone who develops a high fever, rash, severe headache or neck stiffness after being exposed to mosquitoes in an affected area should go see a doctor promptly.
There is currently no vaccine for humans and no specific antiviral treatment for West Nile virus. Treatment focuses on relieving symptoms.
How can people protect themselves?
The best protection starts by stopping mosquitoes from breeding around the home.
People should regularly empty or cover anything that can collect rainwater, including plant saucers, buckets, gutters and watering cans.
When mosquitoes are already around, a simple fan can also help. “If you have one or two reasonably-sized fans blowing air towards your legs or your body, the mosquito will have difficulty reaching you,” Grégory L’Ambert, head of the preventive tiger mosquito control and public health unit at EID Méditerranée previously told The Connexion.
For additional protection, Mr L’Ambert recommends repellents containing proven active ingredients such as DEET, IR3535 or icaridin.
Citronella candles, plants and essential oils should not be relied on as a barrier against bites. “They smell good, but mosquitoes don’t care,” he said.
People using mosquito traps should also avoid placing them next to a terrace or dining area, as they can attract mosquitoes towards the place where people are sitting.
