VIRUS: West Nile virus is a single-stranded RNA virus of the family Flaviviridae, genus Flavivirus.
Epidemiology: West Nile virus is maintained in the cycle involving culicine mosquitoes and birds. Humans typically acquire West Nile infection through a bite from infected adult mosquito. Person to person transmission can occur through organ transplantation, blood and blood product transfusions, transplacentally and via breast milk. Human cases of West Nile infections were recorded in Africa, Israel, Russia, India, Pakistan. In Romania in 1996 West Nile fever occurred with hundreds of neurologic cases and 17 fatalities. First human cases in the United States were in New York City where 59 persons were infected and had fever, meningitis, encephalitis and flaccid paralysis. CLINICAL MANIFESTATION: Most human cases are asymptomatic. The majority of symptomatic patients have a self limited febrile illness. Fatigue, nausea, vomiting, eye pain, headache, myalgias, artralgias, lymphadenopathy and rash are common complaints. Less than 1% of all infected persons develop more severe neurologic illness including meningitis, encefalitis and flaccid paralysis.
Laboratory diagnosis: Diagnosis of West Nile virus infection is based on serologic testing, isolation of virus from patient samples and detection of viral antigen or viral genom. ELISA test and indirect immunofluorescence assay are used for detecting IgM and IgG antibodies in serum and cerebrospinal fluid.
Treatment: In vitro studies have suggested that ribavirin and interferon alfa-2b may be useful in the treatment of West Nile virus disease.
Prevention: The most important measures are mosquito control program and personal protective measures.