The influence of age on the prevalence of hepatitis C virus subtypes 1a and 1b.

The distribution of hepatitis C virus (HCV) genotypes was determined in isolates of 447 chronically HCV-infected German patients by nucleotide sequencing. Of these, 206 (46.1%) were infected with the subtype 1a, 215 (48.1%) with subtype 1b, 2 (0.4%) with subtype 1c, 9 (2.0%) with subtype 3a, and 15 (3.4%) with subtype 4a. Subtype 1a was predominant in those < 40 years old (62.6%) and was associated with the risk factor of intravenous drug addiction and with shorter duration of disease. Conversely, subtype 1b was more frequent in patients > 50 years old (84.7%; P < .001) and was associated with the risk factor of blood transfusions and with longer duration of disease. These data suggest that a shift from subtype 1b to subtype 1a occurred in the population studied. An increase in HCV infection with subtype 1a and a diminution of subtype 1b in the future can be expected.