Case of West Nile virus recorded near Paris for first time
Rare mosquito-borne disease is usually only seen in the south
The mosquitoes feed at night making the virus hard to detect
Babul Hosen/Shutterstock
Two indigenous cases of West Nile virus in the 脦le-de-France region have been recorded, health authorities have reported. It brings the total number of native cases this year to seven, following the first recorded case in the Var department last month.
It is the first time cases have been recorded near the capital.
The recent cases in northern France were recorded in the Seine-Saint-Denis department that borders the capital, with one recorded in mid-July and another in the first week of August.
The victims had both been in France for at least two weeks before falling sick, meaning they were infected by mosquitoes in the country.
One person had travelled to the Jura department at this time so could have picked up the virus from there but the other had not left the greater Paris area.
Recorded cases of the virus so far this year are significantly lower than in 2024, when 34 native cases were reported.
However, these were all reported in the south of the country, meaning the cases in Paris show a northwards movement in areas where mosquitoes can transmit the illness.
Virus is often asymptomatic
West Nile virus is transmitted by common Culex mosquitoes found across France.
Unlike the tiger mosquitoes responsible for the spread of tropical illnesses such as dengue fever, Zika, and chikungunya, Culex mosquitoes are native to Europe.
They tend to feed at night, meaning their bites can often go unnoticed from victims.
West Nile virus is particularly hard to track as around 80% of cases are asymptomatic, meaning a mosquito can infect several people but the illness goes unnoticed.
In the remaining 20% of cases, symptoms include fever, headache, vomiting, and rashes.
In roughly 1% of cases, brain swelling or meningitis occurs, with stiffness of neck, confusion, and seizures.
Mortality rates are high in the group suffering these enhanced symptoms.
Humans (as well as horses) are 鈥榓ccidental hosts鈥� of the virus, and cannot transmit it between themselves.
Only a mosquito that has drawn blood from an infected bird (from where the virus originates) can pass on the disease, and the period where the disease is active usually only runs from May to November, both of which limit the threat of a wider outbreak.
However, authorities believe there is potential for a West Nile epidemic in France, and since 2021 it has been mandatory for health professionals to report any cases of the disease.
Its arrival in Paris means authorities around the capital are stepping up a program to tackle the spread of the virus, and place birds and horses in the area under greater scrutiny.
Health facilities will be informed of signs of the disease to help identify any further cases.
The public are being asked to help limit the opportunities for Culex mosquitoes to infect people.
This includes using mosquito traps and wearing long-sleeved and loose clothing to reduce the risk of being bitten, and immediately consulting a doctor if you record any of the above symptoms following a bite.
