WESTERN VARIETY OF EQUINE ENCEPHALITIS IN MAN

Abstract

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