Horizontal nonparenteral spread of hepatitis B among children.

Two families with an unusually high incidence of hepatitis B infection (15 of 21 persons) were investigated over an 18-month period. Serologic evidence of past or present infection--hepatitis B surface antigen (HBsAg), antibody to hepatitis B surface antigen (anti-HBs), or antibody to hepatitis B core antigen (anti-HBc)--was found in 11 of the 12 members of one family, four of whom were chronic HBsAg carriers, and in four of nine members of a contact family. Anti-HBc was the only serologic marker of infection in five persons. Histocompatibility leukocyte antigen (HLA) typing failed to show an association between carriage of HBsAg and specific HLA markers. Chewing gum was a potential vehicle as HBsAg was detected in gum samples from three of four children who were chronic HBsAg carriers. Horizontal, nonparenteral transmission of hepatitis B virus probably accounted for the clustering of infection in these families, especially via the exchange among children of objects contaminated with oral secretions.