A longitudinal study of hepatitis infection in an institution for the mentally retarded

The natural history of hepatitis A and B infections in a large institution for the mentally retarded were studied over an eight year period. Serum samples were obtained from most subjects on three occasions and tested for anti-HAV, HBsAg, anti-HBs and occasionally anti-HBc, by solid-phase radioimmunoassay. Hepatitis A was found to have been a common infection was 74.8% of subjects having detectable levels of antibody. The virus does not appear to be endemic, as the prevalence of antibody in children admitted since the last outbreak was no higher than amongst non-institutionalised children. The infection rate amongst subjects with Down's syndrome (DS) was higher than amongst subjects with other forms of mental retardation (OMR), and more than 95% of infections in both groups were unrecognised. By contrast with hepatitis A, hepatitis B virus was endemic in the institution with 81.2% of residents showing serological evidence of current or past infection. Of these, 40.8% of subjects with DS and 9.2% of those with OMR were found to be chronic carriers. The carrier rate was higher in males than females and tended to be more prolonged in subjects with DS. During the study period, the predominant subtype of HBsAg detected in the institution changed from adw to ayw.