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West Nile Virus and West Nile Encephalitis (WNE)

West Nile Virus Overview

West Nile virus is a Flaviviridiae virus transmitted to humans by mosquito bites. Virus symptoms range from none to severe: encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord). The disease the virus causes is termed West Nile Encephalitis (WNE). WNE currently is endemic in Asia, Africa, Middle East and can be detected in many areas in the US (see map below).

West Nile virus was discovered in 1937 in the West Nile district of Uganda. West Nile emerged in the United States for the first time in the New York City area in August 1999. There were 62 confirmed human cases and 7 deaths during this outbreak, creating widespread concern.

  • Since the initial 1999 New York City outbreak, the cases of West Nile encephalitis have been relatively limited. In 2002, there were a total of 480 reported cases in humans and 24 deaths (as of August 28, 2002).
  • The distribution of the virus has spread across the United States, as determined from surveillance of infected birds by the Centers for Disease Control and Prevention. In a little more than a year, West Nile spread to 11 states along the East Coast. In 2002, the virus spread to Florida, Arkansas, Louisiana, and Texas. Cases are also being seen in the Dakotas, Colorado, Nebraska, and Wyoming.
  • Whether West Nile encephalitis will present a serious health risk to the United States in the future is unknown. Using precautions directed at limiting contact by mosquitoes is the best preventive measure at this time.

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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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