Distribution of serotypes of hepatitis B surface antigen in an institution for the mentally retarded

The serotypes of hepatitis B surface antigen present in patients at the Lynchburg Training School and Hospital were determined by counterelectrophoresis. Hepatitis B surface antigen was detected by counterelectrophoresis in 72 of 82 samples that were positive by complement fixation or passive hemagglutination techniques. Of the isolates that were serotyped, 51 (71 percent) were ad, and 21 (29 percent) were ay; thus the ad:ay ratio was about 2.4:1. The incidence of the ay serotype was significantly higher in females and in patients with Down's syndrome. The ay serotype was not randomly distributed in the institution but was clustered in two of seven female wards and four of 11 male wards, all of which contained younger patients who had been institutionalized at an early age.