West Nile virus infection

West Nile virus was discovered in 1937 in the West Nile region of Uganda. The virus was found only in the Eastern Hemisphere until 1999. In 1999, West Nile virus was first identified in the Western Hemisphere in New York City. Since 1999, viremic birds have continued to spread the disease across the United States. West Nile virus is an arbovirus and is transmitted as part of a bird-mosquito-bird cycle. During 2002, newly recognized mechanisms of West Nile virus transmission were described. Epidemiologists have documented transmission of the West Nile virus to recipients of transplanted organs and blood transfusions, to laboratory workers, to fetuses, and to breast-fed infants. Approximately 20% of infected individuals will develop a mild febrile illness with symptoms lasting from 3–6 days. Roughly 1 in 150 infected persons will develop severe neurological disease. Recent outbreaks have been associated with meningoencephalitis and case fatality rates of 4–13%. Also, West Nile virus infection has been linked with acute flaccid paralysis. Acute flaccid paralysis is a polio-like syndrome with involvement of the anterior horn cells of the spinal cord and motor axons. The most efficient way to diagnose West Nile virus is to detect IgM antibody in serum or cerebral spinal fluid within 8 days of onset of illness using IgM MAC-ELISA. Treatment of severe neurological disease requires hospitalization and intense supportive care. Effective prevention of West Nile virus infections is dependent on integrated arboviral surveillance and vector mosquito control programs, as well as public education.