Hepatitis B in seven hospitals for the mentally handicapped.

Patients in seven hospitals for the mentally handicapped were screened for markers of hepatitis B infection. Of 2239 patients, 123 (5.5 per cent) were carriers of hepatitis B surface antigen (HBsAg) and a third of these were 'infectious' (negative for antibody to hepatitis B e antigen). Patients with Down's syndrome (DS) were 18 times more likely to be 'infectious' carriers than those without, and male patients were six times more likely to be 'infectious' carriers than female patients. There was a wide difference in carrier rate among the various hospitals. In the hospital with the highest carrier rate (12.5 per cent), 60 per cent of male patients with DS were carriers of HBsAg and of these two-thirds were 'infectious'. The carrier rate decreased with age, but the proportion of carriers who were hepatitis B e antigen positive was unaffected by age.