Changes

===Seasonal Incidence===

===Seasonal Incidence===

The disease is not directly contagious between horses and humans but occurs sporadically in both species from mid-summer to late autumn - during the height of the vector season.  Case numbers peak in June to November in temperate climates.  The vector season is longer in warmer climates, where the disease period is prolonged.  Global warming may promote more outbreaks in historically colder climates.

The disease is not directly contagious between horses and humans but occurs sporadically in both species from mid-summer to late autumn - during the height of the vector season.  Case numbers peak in June to November in temperate climates.<ref name="multiple">Bertone, J.J (2010) Viral Encephalitis in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12</ref> The vector season is longer in warmer climates, where the disease period is prolonged.  Global warming may promote more outbreaks in historically colder climates.<ref name="multiple">Bertone, J.J (2010) Viral Encephalitis in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12</ref>

===Epidemics===

===Epidemics===

Outbeak prediction to date has been inaccurate, implying that other, unidentified factors may be in operation.  However, some epidemic requirements are beyond question.  Adequate amounts of infective virus, sufficent vectors, infected sylvatic hosts and susceptible terminal hosts, and finally, appropriate reservoirs, are all crucial.

Outbeak prediction to date has been inaccurate, implying that other, unidentified factors may be in operation.<ref name="multiple">Bertone, J.J (2010) Viral Encephalitis in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12</ref> However, some epidemic requirements are beyond question.  Adequate amounts of infective virus, sufficent vectors, infected sylvatic hosts and susceptible terminal hosts, and finally, appropriate reservoirs, are all crucial.<ref>Sellers, R.F (1980) Weather, host and vector: their interplay in the spread of insect-borne animal virus diseases, ''J Hyg (Lond)'', 85:65-102.  In: Bertone, J.J (2010) Viral Encephalitis in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12</ref>

==Pathogenesis==

==Pathogenesis==