West Nile virus (WNV) is a neurotropic flavivirus that has emerged globally as a significant cause of viral encephalitis. Infection of humans is associated with a febrile illness that can progress to a lethal encephalitis with symptoms including cognitive dysfunction and flaccid paralysis. Seroprevalence studies suggest that while the majority of WNV infections are asymptomatic, approximately 20 to 30% of infected individuals develop flu-like clinical manifestations characterized as WNV fever.
West Nile virus is a progressively common and dangerous disease. Since 1999, hundreds of people have been infected or killed by it. According to the National Institute of Allergy and Infectious Diseases, scientists have identified at least 40 mosquito species that can transmit West Nile virus. In 1999, 61 cases of severe disease and 7 deaths occurred in the New York area.
The diagnosis of West Nile virus infection is confirmed with a blood or cerebrospinal fluid test. There is no specific treatment for West Nile virus infection. Intensive supportive therapy is directed toward the complications of brain infections. Anti-inflammatory medications, intravenous fluids, and intensive medical monitoring may be required in severe cases.
NIAID supports research on West Nile virus through its comprehensive emerging infectious disease program. This program supports research on bacterial, viral, and other types of disease-causing microbes.