Hepatitis B Virus Genotype and Mutations Related to Clinical Outcome

Hepatitis B virus (HBV) infection is a high risk factor on severe liver diseases. HBV is currently divided into ten genotypes based on the genetic sequence of HBV, which has regional characteristics on clinical outcomes. Recently, cross-border incursion of HBV genotypes occurs worldwide. The nationwide epidemiological study in Japan showed that the number of acute hepatitis B patients was about 8000–8400 people per year. Interestingly, the European–US genotype HBV/A2 has made up an increasing proportion of acute HB cases over 50% in Japan. And 29% of acute HB patients infected with HBV/A became negative for HBsAg within 6–12 months, which were considered “prolonged,” rather than chronic hepatitis B. The acute infection of HBV/A2 is more likely to become chronic compared to HBV/B or C in Japanese population. The invasion of HBV genotypes into other region or country could provide new insights on clinical outcomes of HBV genotypes. The observation of long-term prognosis is needed to collect the clinical evidences on the infection of new genotype into a population.