The expected seasonal increase of locally acquired West Nile virus (WNV) infections in Europe was observed as of July this year, indicating that the transmission season is well under way.
In 2024 and as of 31 July 2024, eight countries in Europe reported 69 locally acquired human cases of WNV infection. Cases were reported by Greece (31), Italy (25), Spain (5), Austria (2), Hungary (2), Serbia (2), France (1) and Romania (1). Eight deaths were reported by Greece (5), Italy (2) and Spain (1).
At the European level, the total number of cases reported so far this year is within the expected range, even though the number of cases in Greece and Spain are higher than in previous years. Clinical and severity indicators are also similar to previous years. All regions affected this year were either previously affected or had neighbouring regions that have reported cases.
Given the favourable weather conditions for WNV transmission in Europe, additional human cases are expected in the coming weeks and months.
WNV is transmitted by mosquito bites. Transmission is most common among birds, but humans and mammals can also become infected. About 80% of human infections have no symptoms. Most cases in humans occur between July and September, when mosquitoes are active.
WNV has a wide geographical circulation in Europe due to an abundance of the Culex pipiens mosquitoes that are responsible for the spread of WNV. This mosquito species is native to Europe and is present throughout Europe.
About 20% of WNV infections in humans may cause West Nile fever, characterised by symptoms such as headache, malaise, fever, vomiting and fatigue. Less than one per cent of infections may cause severe disease that affects the nervous system.
Personal protective measures to prevent WNV infection include the use of mosquito repellent, wearing clothing that covers most of the body, and sleeping in screened or air-conditioned rooms.
Risk for people
Risk factors include:
advanced age
tumours in the brain
high blood pressure
blood disorders
diabetes
kidney diseases
alcohol abuse
genetic factors
The mortality rate among people who develop WNND can be up to 17%.
How it spreads
WNV is usually spread to humans from infected mosquitoes. Mosquitoes get infected by infected birds. Mosquitoes spread the virus, and birds help the virus to grow in numbers. The virus can also spread between humans through blood transfusion and organ transplant. Other ways in which the virus can spread are from mother to child during pregnancy and breast-feeding and through laboratory exposure.
Vaccination and treatment
There is no specific treatment for the virus, only supportive care.
