A MAJOR EPIDEMIC OF INFECTIOUS HEPATITIS IN AN INSTITUTION FOR THE MENTALLY RETARDED

From April-September 1970, 375 clinically apparent cases of infectious hepatitis occurred among 3600 patients in an institution for the mentally retarded. Only one employee had clinically apparent hepatitis during the epidemic. The clinical to subclinical ratio of infection was approximately 2:1. The incubation period was short, averaging 29 days. Transmission was believed to be from person to person by the fecal-oral route through direct contact or through fomites. Attack rates were high, averaging 57% in a study group of 473 severely retarded patients. The attack rates were low among wards of patients who were less retarded and thus capable of maintaining better personal hygiene. Two deaths attributed to hepatitis occurred during the epidemic. Patients over 40 years old or any patient who had been institutionalized at Lynchburg for more than 18 years had very low attack rates. The epidemic hepatitis was not related to the hepatitis B antigen (Australia antigen). Immune serum globulin administration initially failed to control the epidemic. Attack rates during a period in which no ISG was given were similar. A controlled study late in the epidemic demonstrated the effectiveness of ISG and the reasons for its apparent initial failure. No index cases were identified early in the epidemic. ISG was given on the day the first secondary case was recognized and only prevented clinical disease which would have developed after 21 days. Administration of ISG prior to this proportionally reduced the time period over which secondary cases were recognized.