Western equine encephalitis virus

The Western equine encephalitis virus is the causative agent of relatively uncommon viral disease Western equine encephalitis (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. 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 sequellae 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.