There were 2,083 cases of autochthonous transmitted West Nile virus (WNV) reported in Europe (mainly the south and south east) in 2018. This compares to a total of 832 cases recorded across the previous seven years and was a 7.2-fold increase on 2017. There were 181 deaths due to WNV.27,28

Although around 80 per cent of WNV infections are asymptomatic, the remainder will develop West Nile fever, with one in 150 developing symptoms of severe disease. Symptoms are flu-like, with a rash and swollen lymph glands. Neurological aspects include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis.29

The main reservoir hosts for the virus are birds which can infect each other, but the virus is transmitted to humans and other mammals by mosquitoes of the Culex species. Outbreaks among animals normally precede human outbreaks. While a WNV vaccine is available for horses, a human vaccine is still in development.