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West Nile Virus (cont.)

West Nile Virus and West Nile Encephalitis Causes

West Nile virus is transmitted to humans by the bite of an infected mosquito. Mosquitoes become infected by biting birds (or other animals like horses or dogs) that harbor the virus; thus, mosquitoes are the vectors of West Nile encephalitis (WNE). The virus is not spread from person to person nor is it spread from infected birds to humans without a mosquito bite. The virus has now been found in 111 bird species and about a dozen mammals.

  • How West Nile virus entered New York in 1999 is not entirely clear. The most likely explanation is that the virus was introduced by an imported infected bird or by an infected human returning from a country where West Nile virus is common. Before the 1999 New York outbreak, West Nile encephalitis had been identified previously only in Africa, Asia, the Middle East, and only rarely in Europe.
  • Most cases of West Nile occur during the warm weather months. Nonetheless, the mild climate in southern U.S. states is expected to sustain the mosquitoes beyond those months.
Medically Reviewed by a Doctor on 4/9/2015

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West Nile Encephalitis »

West Nile encephalitis (WNE) is distinguished from other arthropod-borne causes of viral encephalitis (eg, western equine encephalitis, eastern equine encephalitis [EEE], Japanese encephalitis, Venezuelan encephalitis) based on its geographic distribution, clinical features, and laboratory findings.

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