Equine encephalitis is not a new disease; it has been observed in the United States for over ninety years. Its etiology was not definitely established until 1931, when Meyer and his co-workers1 first reported the discovery of a virus as the cause of encephalomyelitis among horses and mules in the San Joaquin Valley of California. A few years later TenBroeck and Merrill2 isolated a virus in an epizootic occurring in the eastern states. This virus proved to be immunologically distinct from the western strain isolated by Meyer. It produced a much more virulent infection, with a resultant mortality of almost 90 per cent (Feemster3).
Meyer4 in 1932 first suggested that human beings might become infected with the equine virus and reported 3 cases in which he suspected such an infection. Eklund and Blumstein5 presented the first proof that such a specific human infection might actually
BAKER AB, NORAN HH. WESTERN VARIETY OF EQUINE ENCEPHALITIS IN MANA CLINICOPATHOLOGIC STUDY. Arch NeurPsych. 1942;47(4):565–587. doi:10.1001/archneurpsyc.1942.02290040055003