Transmission of hepatitis B and hepatitis delta viruses in the households of chronic hepatitis B surface antigen carriers: a regression analysis of indicators of risk.

To evaluate whether clinical and laboratory features of a hepatitis B surface antigen (HBsAg) carrier can predict risks of infection, its chronicity, and the development of liver disease among close contacts, the authors studied a cohort of 994 first degree relatives or cohabitants (household contacts) of 226 non-drug-addicted chronic HBsAg carriers (index cases), of whom 77% had liver disease and 26% were superinfected by hepatitis D virus (HDV). A logistic form of regression analysis was used to assess the role of each feature in the index case as predictor of hepatitis B virus (HBV)- and HDV-related outcomes among household contacts. Six models of risk, expressed as odds ratios, were assessed by multivariate step-down analysis, with the following results. 1) Infection with HBV in the household contact was independently predicted by the index case being son, sibling, spouse, female, or HBV-DNA positive. 2) Chronic HBsAg carriage in the adult household contact was associated with female sex of the index case and with being a sibling; among young subjects, household contacts were more likely to be chronic HBsAg carriers when the index case was the mother, a sibling, or an HBV-DNA-positive subject. 3) HBV-DNA positivity in the young contact was more likely when the index case was HBV-DNA positive and when she was the mother. 4) HBV-DNA positivity in the absence of hepatitis B e antigen (HBeAg) in serum in the index case was not related to a similar pattern of infection in HBsAg-positive contacts. 5) Super-infection with HDV of an HBsAg-positive household contact was significantly predicted by female sex of the index case and by anti-HDV positivity. 6) Chronic liver disease in a contact was predicted only by HDV superinfection of the index case. We conclude that horizontal, nonparenteral transmission of HBV among siblings plays a major role in the household of HBsAg carriers from an intermediate endemicity area.