West Nile Virus Infection

Abstract

Although long recognized as a human pathogen, West Nile virus (WN virus) emerged as a significant public health problem following its introduction and spread across North America. Subsequent years have seen a greater understanding of all aspects of the viral infection. The North American epidemic witnessed a further understanding of the virology, pathogenesis, clinical features, and epidemiology of WN virus infection. Approximately 80 % of human WN virus infections are asymptomatic. Most symptomatic persons experience an acute systemic febrile illness; less than 1 % of infected persons develop neuroinvasive disease, which typically manifests as meningitis, encephalitis, or anterior myelitis resulting in acute flaccid paralysis. Older age is associated with more severe illness and higher mortality; other risk factors for poor outcome have been challenging to identify. In addition to natural infection through mosquito bites, transfusion- and organ transplant-associated infections have occurred. Since there is no definitive treatment for WN virus infection, protection from mosquito bites and other preventative measures are critical. WN virus has reached an endemic pattern in North America, but the future epidemiologic pattern is uncertain.