Transmission of hepatitis B virus to classroom contacts of mentally retarded carriers.

The risk of the spread of hepatitis B virus infection from deinstitutionalized, mentally retarded carriers to pupil and staff school contacts in the New York City public school system was measured serologically in a three-phase study from 1978 to 1982. In the third phase, undertaken in 1982, blood samples were drawn and questionnaires were completed on students and staff tested in either of the first two phases and on comparison groups with intermediate and no known school exposure to deinstitutionalized carriers. Univariate and logistic regression analyses revealed that staff and pupils with a history of classroom exposure to a hepatitis B virus carrier had significantly increased prevalences of hepatitis B virus infection (13.4%, odds ratio = 1.9; 9.3%, odds ratio = 2.5, respectively). Similarly, yearly seroconversion rates of 1.3% and 0.67% indicate that staff and, to a lesser extent, pupils are at increased risk of infection.