West Nile virus

West Nile virus A febrile disease that is transmitted from birds to mosquitoes and then to people by mosquito bites. The virus is named after the area in which it was first found, in Uganda. West Nile virus occurs in parts of Africa and Asia and, infrequently, in Southern Europe, the Middle East, and the US. West Nile virus had never been seen in birds or people in the Western Hemisphere prior to an outbreak in summer 1999 in New York City. Since that time, it has spread across the US. Most affected people have no symptoms or minor symptoms, but a febrile illness may develop accompanied by drowsiness, headache and nausea due to encephalitis, pain in the abdomen, a rash, and swollen glands (lymphadenopathy). Fatal cases tend to involve infants and small children under age 5, the aged, and people with impaired immune systems. Prevention of mosquito bites can help prevent infection. Also known as West Nile encephalitis. See also encephalitis.