West Nile Virus (WNV) is commonly found in Africa, the Middle East, North America and West Asia. Cases of WNV in humans, caused by the bite of an infected mosquito, have also been recorded in Europe since the 1950s. WNV is most frequently transmitted to mosquitoes by migratory birds and horses. Warm, wet weather is likely to increase breeding grounds for the mosquitoes that serve as the virus vector. In recent years, human cases and outbreaks of WNV have been reported by many countries in the WHO European Region, several of which are reporting cases for the first time.
In the Region, the majority of cases in humans occur between June and November, when mosquitoes are most active. While most people infected by WNV don’t experience any symptoms, 20% of infected people develop West Nile fever, and 1 in 150 people develop a more severe form of disease, neuroinvasive disease, which can be fatal. Serious illness can occur in people of any age, but older people and immunocompromized people – for example, transplant patients – have the highest risk of getting severely ill when infected with WNV.
“WHO is responding to the increase in West Nile fever by strengthening surveillance and reporting across the WHO European Region. WHO is also building laboratory capacity so that more laboratories have the ability to detect WNV, providing guidelines for treatment, and targeting health information and advice to help people protect themselves from mosquito bites,” said Nhu Nguyen Tran Minh, WHO/Europe Head of Infectious Hazard Management.