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Western equine encephalitis virus


Western equine encephalitis virus

Western equine encephalitis virus
CryoEM model of western equine encephalitis virus, 12Å resolution. EMDB entry [1]
Virus classification
Group: Group IV ((+)ssRNA)
Family: Togaviridae
Genus: Alphavirus
Western equine encephalitis virus
Classification and external resources
ICD-10 A83.1
ICD-9-CM 062.1
MeSH D020241

The Western equine encephalomyelitis virus is the causative agent of relatively uncommon viral disease Western equine encephalomyelitis (WEE). An Alphavirus of the family Togaviridae, the WEE virus is an arbovirus (arthropod-borne virus) transmitted by mosquitoes of the genera Culex and Culiseta.[2] WEE is a recombinant virus between two other alphaviruses, an ancestral Sindbis virus-like virus, and an ancestral Eastern equine encephalitis virus-like virus. There have been under 700 confirmed cases in the U.S. since 1964.

In the U.S. WEE is seen primarily in states west of the Mississippi River. The disease is also seen in countries of South America. WEE is commonly a subclinical infection; symptomatic infections are uncommon. However, the disease can cause serious sequelae in infants and children. Unlike Eastern equine encephalitis, the overall mortality of WEE is low (approximately 4%) and is associated mostly with infection in the elderly. There is no vaccine for WEE and there are no licensed therapeutic drugs in the U.S. for this infection.


  • History 1
  • Use as a biological weapon 2
  • See also 3
  • References 4
  • External links 5


WEE was discovered in 1930 when a number of horses in the San Joaquin Valley of California, USA died of a mysterious encephalitis. Karl Friedrich Meyer investigated but was not able to isolate the pathogen from necropsies of horses that had been dead for some time and needed samples from an animal in the earlier stages of disease. When the team heard of a horse that appeared to have encephalitis, its owner threatened to shoot the scientists. However Meyer was able to convince the farmer's wife that the horse was dying anyway, and to secretly signal him when the farmer was asleep in exchange for $20 (as this was during the Great Depression, this was a substantial amount of money). Meyer and his colleagues hid in the bushes until the signal, euthanized the horse and stole its head. They successfully isolated WEEV from the brain tissue.[3]

Use as a biological weapon

Western equine encephalitis virus was one of more than a dozen agents that the United States researched as potential biological weapons before the nation suspended its biological weapons program.[4]

See also


  1. ^ Sherman, M. B.; Weaver, S. C. (2010). "Structure of the Recombinant Alphavirus Western Equine Encephalitis Virus Revealed by Cryoelectron Microscopy". Journal of Virology 84 (19): 9775–9782.  
  2. ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill.  
  3. ^ Sabin, Albert (1980). "Karl Friedrich Meyer: 1884–1974" (PDF). Biogr Mem Natl Acad Sci. (Washington, D.C.: National Academy of Sciences) 52: 269–332.  
  4. ^ "Chemical and Biological Weapons: Possession and Programs Past and Present", James Martin Center for Nonproliferation Studies, Middlebury College, April 9, 2002, accessed 31 March 2010.

External links

  • United States Centers for Disease Control and Prevention (CDC) Fact Sheet
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