WESTERN EQUINE ENCEPHALOMYELITIS IN CHICAGO:  Report of a Patient Successfully Treated with Gamma Globulin

Shortly after the virus of Western equine encephalomyelitis was isolated from the central nervous system of affected horses in California by Meyer, Haring and Howitt,¹ infections were noted in persons who worked in close association with infected animals.² Howitt³ first recovered the virus from a human being in 1938. Since then outbreaks of the disease have occurred in several Western and Central states. The largest epidemic occurred in Manitoba, Minnesota and North Dakota in 1941⁴; over 3,000 cases were reported with a mortality rate of 8 to 15 per cent. At present an endemic focus of this disease is known to exist along the Pacific coast. Annual outbreaks occur in the Yakima valley (Washington)⁵ and in Kern and Fresno counties of California.⁶

Present epidemiologic and experimental evidence point to the spread of equine encephalomyelitis by an arthropod vector rather than by contact. Culex tarsalis