During the late summer and early fall of 1964 an epidemic of St. Louis encephalitis occurred in Houston. In the three-month period from July to October 1964, 50 patients were admitted to the pediatric service of Ben Taub General Hospital with a preliminary diagnosis of viral meningoencephalitis. Early in the period of study there was nothing to suggest that the viruses causing the central-nervous-system disease were other than the usual endemic enteroviruses which are prevalent in Houston in midsummer.1 However, an unusual incidence of severe meningoencephalitis among adults, with a number of fatalities,2 suggested that a new viral agent had entered the community.
Brain tissue was obtained at postmortem examination from several adults with meningoencephalitis. Microscopic examination of the tissue revealed pathological findings consistent with a diagnosis of St. Louis encephalitis. Preliminary blood samples obtained from adult as well as pediatric patients demonstrated serologic evidence of St. Louis