Journal of Veterinary Diagnostic Investigation 23(3) 570 –575 © 2011 The Author(s) Reprints and permission:

Eastern equine encephalitis (EEE) is a zoonotic disease of the family Togaviridae, genus Alphavirus. Viruses of this genus are mainly associated with disease of the central ner vous system (CNS) of horses and human beings, both of which are the terminal hosts, while infected birds usually act as reservoirs and do not develop disease.8 However, domes tic and wild birds including pheasants, emus, and broilers have often been affected, and there are records of the disease in other species, including sheep,2 dogs,4 and deer.14 In South America, there have only been 2 cases of fatal EEE reported in human beings, 1 in Brazil and another in Trinidad, while in North America, over 100 fatal cases have been reported. This difference can be attributed to the dis tinct pathogenic characteristics of the agents and habits of the vectors involved. It is suggested that the U.S. variants ar