The prevalence and transmission of hepatitis B virus infection in urban, rural and institutionalized black children of Natal/KwaZulu, South Africa.

The sera of statistically selected urban (805), rural (238) and institutionalized (127) black children were tested for markers of hepatitis B virus (HBV) infection. The age-standardized (6-14 years) prevalence rates of HBs antigenaemia for comparison between urban, rural and institutionalized children were 10%, 18.5% and 25.1% and the HBV exposure rates were 31.4%, 62.1% and 72.0% respectively. In the newborn to six years age group the prevalence rates of HBsAg and HBV exposure were 2.5% and 7.1% for urban children and 53.1% and 70.3% for institutionalized children. Peak prevalences of HBsAg occurred in the 6-8 year age group and were 14.4% and 22.6% in urban and rural children respectively. Hepatitis Be Antigen (HBeAg) was detected in 46.5% and antibodies to hepatitis Be antigen (HBeAb) in 10.0% of all HBsAg positive children. Multiple mechanisms involving horizontal rather than vertical transmission appeared to be important in urban children, with HBV exposure in females being significantly associated with ear-piercing (p less than 0.001) and scarification (p less than 0.05). In addition, HBsAg was detected in 25 of 29 pools of bloodfed mosquitoes caught at the children's institution and was negative in all four pools of unfed mosquitoes, suggesting that these arthropods may also be one factor in the horizontal spread of HBV infection. Familial clustering of HBV infection was suggested by a significantly higher (p less than 0.01) prevalence of HBsAg amongst family contacts of HBsAg positive urban children (17.7%) than in the control groups of family contacts of HBsAb positive children (8%) and children who were negative for all HBV markers (2.4%). The significance and implications of these findings are discussed.