Susceptibility to Eastern Equine Encepkalomyelitis

In the summer of 1938 an outbreak of encephalomyelitis in man in the vicinity of Massachusetts was proved to be due to the virus of equine encephalomyetitis, Eastern strain (1). An epidemic of encephalomyelitis in horses had appeared a month before and continued during the human outbreak (2). I t was thought, although not proved, that the virus was transmitted by mosquito vectors (3). The age distribution indicated that the highest incidence was among the youngest children. Thus, more than a third of the thirty-eight recognized cases were in children under 2 years of age, half under 5 years, and more thnn two-thirds under 10 years of age (2). This age distribution is of special interest in connection with previous reports of an increasing resistance with age of animals to peripheral injection of equine encephalomyelitis virus as weU as of certain other neurotropic viruses. In each case cerebral suceptibility was found not to be influenced by age.