West Nile virus

West Nile virus was first isolated from a febrile adult woman in the West Nile District of Uganda in 1937. 

The virus is a member of the Japanese encephalitis antigenic complex in the family Flaviviridae, genus Flavivirus. The Flavivirus are a genus of arboviruses that included viruses that cause yellow fever, St. Louis encephalitis and dengue fever.

The West Nile virus is a mosquito-borne disease that can cause inflammation of the brain in humans. In 1999, the virus appeared in North America for the first time, and the following year the virus was reported in 12 states along the East coast. The outbreak in New York was the first sign of these infection in the Western world.

Prior to its appearance in North America, West Nile virus occurred in parts of Africa, Asia, and Europe and a number of different mosquito species were identified as its vectors in natural cycles involving birds as amplifying hosts.

Illness from this virus is essentially a disease of the elderly. Although it may occur in people of all ages from five to 90. Being over 50 years old is the major risk factor for development of encephalitis. Persons 50-60 years old are 10 times more likely to experience central nervous system disease than younger person.

The illness presents as fever with hot flashes, night sweats, weakness, nausea, eye pain, upper respiratory symptoms and vomiting. Lynphadenopathy and a diffuse macular papular, or morbiliform rash may occur.
West Nile virus