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Western Equine Encephalitis

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We would like to acknowledge and thank the Centers for Disease Control for allowing
the use of the following information and links concerning mosquito-borne illness.


  • No licensed vaccine for human use
  • No effective therapeutic drug
  • Unknown overwintering cycle
  • Control measures expensive
  • Limited financial support of surveillance and prevention


  • Epidemic disease that is difficult to predict
  • Risk exposure increases as population expands into endemic areas


  • National Notifiable Diseases Surveillance System

Risk Groups:

  • Residents of endemic areas and visitors
  • Persons with outdoor work and recreational activities


  • Mosquito Borne


  • Total case costs range from $21,000 for transiently infected individuals to $3 million for severely infected individuals
  • Insecticide applications can cost as much as $1.4 million depending on the size of area treated


  • Mild to severe neurologic deficits in survivors.


  • 639 confirmed cases in the U.S. since 1964.

Etiologic Agent:

  • Western equine encephalitis virus, member of the family Togaviridae, genus Alphavirus. Closely related to eastern and Venezuelan equine encephalitis viruses

Clinical Features:

  • Symptoms range from mild flu-like illness to frank encephalitis, coma and death.