[Change of the prevalent subtype of hepatitis B antigen in acute hepatitis B infections (author's transl)].

Subtyping of hepatitis B antigen (HBs Ag) in patients with acute hepatitis B revealed subtype ay in 75 percent while subtype ad was much more common in chronic hepatitis B infections: 81 percent of HBs Ag positive blood donors and 76 percent of patients with HBs Ag positive chronic aggressive hepatitis revealed subtype ad. In contrast to blood donors and chronic hepatitis patients, a change of the prevalent subtype was noted in acute hepatitis patients between 1970 and 1974. Before May 1972, subtype ad was found in 67 percent of patients, whereas later subtype ay dominated in 93 percent. An unequal distribution of subtypes between acute and chronic forms of hepatitis B infections has been explained by differences in the virulence of virus strains. Our results suggest that the higher prevalence of subtype ad in longterm carriers may be due to infection during an earlier time when subtype ad was also common in acute infections. The change of the prevalent subtype in acute infections may be attributed to differences in contagiosity rather than differences in virulence of virus strains.