West Nile Fever is a disease caused by a virus (West Nile Virus - WNV) of the Flaviviridae family, first isolated in 1937 in the West Nile district of Uganda. This virus is commonly found in Africa, West Asia, Europe, Australia and the Americas.
Wild birds and mosquitoes (especially of the Culex genus) are the natural reservoirs of the virus, and mosquito bites are the main route of transmission to humans. Other routes have been documented, although much less frequent, such as organ transplant, blood transfusions and mother-to-child transmission during pregnancy. There is no evidence of human-to-human transmission of WNV through contact with an infected person. The virus is known to infect other mammals, especially equines, but also dogs, cats, rabbits and other species.