Arthropod-Borne Encephalitis in 1956

Abstract

Increased incidence of the arthropod-borne encephalitis in the U. S. in 1956 was characterized by sporadic occurrence of Eastern equine encephalitis in horses throughout the Atlantic and Gulf states, and occurrence in man of 12 cases in southeastern Massachusetts, 1 in Delaware, and 2 in Maryland. Numerous virus isolations from horses, pheasants, mosquitoes and wild birds in North Atlantic coastal states were recorded. Western equine encephalitis occured diffusely in nature, although it failed to infect man and horses in epidemic fashion. It remains a severe disease threat in irrigated areas of the West. St. Louis encephalitis was the main contributor to the high incidence of reported acute infectious encephalitis, notably in a large rural epidemic in Texas and in three smaller foci in Kansas, Colorado and Indiana. This disease reappeared as an urban epidemic in Louisville, Ky., for the first time since 1937. The epidemiology and public health importance of this disease group, and the national surveillance program for their study are discussed.