Evidence from the New York experience as well as from outbreaks in Africa, Europe and Asia, point to Culex, and the one that seems most likely involved in the New York region is Culex pipiens. Unlike the relatively rural mosquitoes suspected of transmitting the Eastern Equine encephalitis virus, Culex pipiens is well-adapted to conditions found in more urban areas, which makes control of West Nile encephalitis potentially very troublesome. You will find this mosquito virtually anyplace, except perhaps Antarctica. West Nile encephalitis can cause the brain to swell. People with severe reactions may suffer convulsions, fever, and paralysis, but infection rarely leads to death.
Many people carry the virus with mild, if any, symptoms.
Scientists first isolated the virus in Uganda in 1937. It was later found in Africa, the Middle East, and Europe. In 1996, the virus infected thousands in Romania and was later detected in the Czech Republic and Italy. Then, in August 1999, birds began dying in New York City. Tests identified West Nile encephalitis virus as the culprit, fixing the virus on North American shores for the first time in history.