Acute exacerbations of chronic hepatitis B are rarely associated with superinfection of hepatitis B virus

There are 7 genotypes of hepatitis B virus (HBV). Whether superinfection of HBV carriers with different HBV genotypes occurs remains unknown. We there fore determined the HBV genotype and association between superinfection and acute exacerbation of disease in a cohort of 244 patients with chronic HBV infection who had elevated serum aminotransferase levels for at least 1 ye ar. Within this group, 103 patients experienced acute exacerbation with an annual incidence of 13%, and 20 of the 103 patients had IgM antibody to hep atitis B core antigen (IgM anti-HBc). These 20 patients had a higher preval ence of genotype C infection (65%) than the remaining 83 anti-core IgM-nega tive patients (40%) who also had acute exacerbations (P < .05). Detailed an alysis of HBV genotypes and sequences of the variable pre-S gene were deter mined in serial samples from 20 patients with IgM anti-HBc-positive acute e xacerbations (group A), 20 patients with IgM anti-HBc-negative acute exacer bations (group B), and 20 patients without exacerbations (group C). Two (10 %) of the group A patients had virologic evidence of HBV superinfection dur ing acute exacerbation, one superinfected with heterotypic virus and the ot her with homotypic virus. The newly introduced virus disappeared after the exacerbation and the original virus resumed thereafter. The calculated prev alence of HBV superinfection in the hepatitis B carriers and those with acu te exacerbations was 0.8% (2 of 244) and 1.9% (2 of 103), respectively. In conclusion, superinfection of HBV on hepatitis B carriers indeed occurs and may cause acute exacerbations, albeit at a low frequency even in hyperende mic areas of HBV infection.