Late seroconversion to hepatitis B in a Somali village indicates the important role of venereal transmission.

Hepatitis B virus (HBV) markers were investigated in a cross-sectional study in 1985 on sera from 84% of the 648 inhabitants in a rural Somali village. The prevalence of HBV markers increased with age, from 9.7% in subjects less than 12 years old, to 38% in the age group 12-19 years, and to 68% in adults. HBV markers were more common in boys less than 12 years old, 13%, than in girls of the same age group, 5.8% (P less than 0.05). A rapid increase of HBV markers started at adolescence in both sexes. The female cohort showed their highest seroconversion rate during their second decade of life, while the male cohort seroconverted more rapidly in the third decade. Thus, an initially more rapid seroconversion among boys was reversed when the females reached reproductive age, and no sex difference in marker frequencies was observed in the age group 12-19 years. There was a steady increase of HBV markers during the reproductive years in both sexes. The frequencies of HBsAg, as well as total markers, were significantly higher in adult males than females, 14 vs 5.6%, and 77 vs 62%, respectively. HBV markers were more frequent in wives of HBV positive husbands than in those married to HBV negative husbands. No increased marker prevalence was observed among siblings of HBV positive children, nor among their mothers, which disproved the role of vertical and early horizontal transmission. In 1989 the four-year rate of seroconversion was investigated in villagers who were seronegative in 1985. On testing 158 sera from 319 individuals, the seroconversion rate was significantly lower among those younger than 12 years in 1985 compared to those in the older age group, 5 vs 17%.(ABSTRACT TRUNCATED AT 250 WORDS)