Changes

====Epidemiology====

====Epidemiology====

=====(1) Distribution=====

=====(1) Distribution=====

Togaviral encephalitis in equids is largely confined to the Western Hemisphere.  Venezuelan EEV can cause large outbreaks of disease over extensive geographical areas in both humans and horses.  Spread of this virus into Central America has had disasterous consequences with epidemics as far north as Texas. Climatic conditions and interventions that support vector populations, such as irrigation, greatly influence the geographical spread of the disease.  EEE has been recorded across the United States, but mostly in the Southeastern States. As its names suggests, WEE has a predilection for the Western states which have been subject to significant outbreaks in the past.  A regional alteration in virulence has been proposed for the steep decline in clinical case numbers observed in this area.  A lag phase of 2-5weeks is commonly observed between horse and human cases of WEE in a given locus.  Both are dead-end hosts for the virus.    A subtype of Western EEV, Highlands J virus, was isolated from the brain of a horse with encephalitis in Florida (Karabatsos ''et al''., 1988).

Togaviral encephalitis in equids is largely confined to the Western Hemisphere.  Venezuelan EEV can cause large outbreaks of disease over extensive geographical areas in both humans and horses.  Spread of this virus into Central America has had disasterous consequences with epidemics as far north as Texas. Climatic conditions and interventions that support vector populations, such as irrigation, greatly influence the geographical spread of the disease.  EEE has been recorded across the United States, but mostly in the Southeastern States. As its names suggests, WEE has a predilection for the Western states which have been subject to significant outbreaks in the past.  A regional alteration in virulence has been proposed for the steep decline in clinical case numbers observed in this area.  A lag phase of 2-5weeks is commonly observed between horse and human cases of WEE in a given locus.  Both are dead-end hosts for the virus.    A subtype of Western EEV, [[Equine Viral Encephalitis|Highlands J virus]], was isolated from the brain of a horse with encephalitis in Florida (Karabatsos ''et al''., 1988).

=====(2) Transmission=====

=====(2) Transmission=====