ABSTRACT
Human encephalitis in California generally was attributed to poliovirus infection and was diagnosed as polioencephalomyelitis. In 1951 western equine encephalomyelitis (WEE)-like virus was isolated from birds and mosquitoes collected in a Louisiana swamp. In Argentina, epizootics of equine encephalitis have recurred periodically since 1908, and in 1933 WEE virus was isolated by Rosenbusch. Although mechanization has reduced the economic impact of subsequent WEE epizootics in the United States, WEE remains an economically important agricultural disease in Argentina and Uruguay where equines are important draught animals and are raised for meat production. WEE virus is a member of the genus Alphavirus of the family Togaviridae. The spectrum of infection ranges from inapparent to full-blown encephalitis and encompasses mild forms of illness such as fever with headache and aseptic meningitis. WEE viral infection in horses and mules is similar to other equine encephalitides including eastern equine encephalitis and Venezuelan equine encephalitis.
