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=====Seasonal Incidence=====
 
=====Seasonal Incidence=====
 
The diseases occur largely during the height of the vector season.  In temperate climates, case numbers peak in June to November.  In warm climates, where the vector season is longer, the disease period is prolonged.  Global warming may promote more cold climate outbreaks.
 
The diseases occur largely during the height of the vector season.  In temperate climates, case numbers peak in June to November.  In warm climates, where the vector season is longer, the disease period is prolonged.  Global warming may promote more cold climate outbreaks.
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=====Epidemics=====
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Prerequisites for epidemics to occur include adequate and adjacent numbers of reservoir animals, sufficient quantities of virulent virus, infected intermediate hosts, insect vectors and susceptiple horse and human populations.  Outbeak prediction has been inaccurate, implyingf that other, unidentified factors may be important.
    
====Pathogenesis====
 
====Pathogenesis====
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