What is West Nile encephalitis?

Updated: Aug 07, 2018
  • Author: David S Howes, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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In 1999, a late summer outbreak of West Nile encephalitis (WNE), an arbovirus not previously found in the United States, was implicated in several deaths in New York. By late summer 2002, West Nile virus had been identified throughout the eastern and southeastern United States. Following bird migration, the virus began to extend westward, and by April 2003, virus activity had been detected in 46 states and the District of Columbia.

An updated Centers for Disease Control and Prevention (CDC) report for 2007 (West Nile Virus Update) included information regarding viremic blood donors. Throughout the world, outbreaks of WNE have been associated with severe neurologic disease, though, in general, only 1 in 150 affected patients develop symptomatic WNE. By 2008, the number of cases reported to the CDC had dropped dramatically throughout the United States, owing to the decimation of the US crow bird population, a common host of the WNV, which is lethal to the American crow. [2]

For more information, see the CDC fact sheet on West Nile virus, links to state and local government web sites on West Nile virus, and the Environmental Protection Agency (EPA)/CDC article on mosquito control.

For clinical information on the Internet, see West Nile Virus: A Primer for the Clinician, from the August 6, 2002, issue of Annals of Internal Medicine. The Canadian equivalent, West Nile Virus: Primer for Family Physicians, was published on June 10, 2005, in Canadian Family Physician. [3]

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