The traveller and West Nile virus

Infection with West Nile virus is a zoonosis which has emerged recently as a threat to public health and animal health in temperate regions in parts of Europe and more extensively in North America. Most infections are asymptomatic, 20% lead to a mild febrile illness and about 1% result in severe neurological disease, particularly in those over the age of 50 years. West Nile virus is transmitted by mosquitoes and the principal hosts are numerous species of wild birds. There is no specific treatment and a vaccine is not available. Prevention in areas where the virus is circulating is based on protection from mosquito bites and reduction and control of the number of mosquitoes in the environment. The risk to travellers is not known at present, but appears to be low in terms of symptomatic illness.