Prevalence of chronic hepatitis B virus infection in pregnant black women living in Soweto.

Urban black children have an appreciably lower hepatitis B virus (HBV) carrier rate than rural Black children. The purpose of this study was to determine the carrier rate in the preceding generation of urban-born Blacks, in order to establish how rapidly the reduction in carrier rate following urbanization has occurred. HBV markers were measured by radioimmunoassay in the serum of 616 urban-born and 618 rural-born pregnant Black women living in Soweto. HBV carriage was significantly less frequent in the urban-born (1.3%) than in the rural-born women (4.0%; P less than 0.05). Total HBV exposure was also less common in the urban-born women (35.2% compared with 44.7%; P less than 0.001). HBV carrier rates were the same in women whose mothers were urban-born (1.31%) and those with rural-born mothers (1.68%). Only three rural-born and no urban-born women had replicative HBV infection. These findings suggest that the decrease in the HBV carrier rate with urbanization is abrupt, occurring in the first generation born in the urban environment.