Transmission of hepatitis B virus from adopted Asian children to their American families.

In 1985, 6,991 Asian children were adopted by Americans. To estimate the risk that such children may transmit hepatitis B virus to their adoptive families, we conducted a cumulative-incidence follow-up study in the State of Washington. We examined the association between having adopted a hepatitis B surface antigen (HBsAg)-seropositive Asian child and serologic evidence of past or present hepatitis B virus infection in adoptive family members. Seven (9 per cent) of 77 family members exposed to an HBsAg-seropositive child had evidence of past or present infection compared with four (2 per cent) of 232 nonexposed (relative risk = 5.3; 90% confidence limits [CL] = 2.0-13.9). The risk was higher for those with prolonged exposure and was entirely restricted to parents.