Geographical distribution of the subtype of hepatitis B surface antigen in Chinese.

Using the much more sensitive hemagglutination inhibition assay for subtyping of hepatitis B surface antigen (HBsAg), we examined the determinants a, d, w and r in 192 from 228 HBsAg positive adults who had been found after screening with reversed passive hemagglutination method. Sixty-four subtypable cases were asymptomatic carriers and the remaining 128 were liver disease patients. Among them there was no significant difference of the subtypes, invariably with adw as the main subtype. Geographical difference was evident: adr was the main subtype (78 per cent) among the northern Chinese; while adw was dominant (76 per cent) among the southern Chinese with the Yangtze River as a boundary. Eight of the 18 adr-subtyped northern Chinese were born and live in Taiwan where 91 per cent of HBsAg positive Taiwanese were adw-subtyped. This was an indirect evidence that intra-familial spreading from parents played an important role in hepatitis B virus infection.