| [ Summary ] |
Ten genotypes of the hepatitis B virus (HBV) have been detected with sequence divergence > 8 % in the entire HBV genome and have been designated by the letters A to J. These genotypes have distinct geographical distribution and influence the severity of liver disease and the response to antiviral therapies. Although HBV genotype A (HBV/A) is predominant in Northwestern Europe, the United States, Central Africa, and India, many lines of evidence have revealed an increase in acute infection with HBV/A following sexual transmission in Japan. Acute infection with HBV/A may be associated with an increased risk of progression to persistent infection compared with acute infection with HBV/B or HBV/C. Furthermore, more than 30 subgenotypes have been reported. For instance, genotype C, which was the most common genotype in Japan, has been divided into C1,5 (prevalent in Southeast Asia), C2 (prevalent in East Asia), C3 (prevalent in Polynesia), and C4 (prevalent in Oceania). HBV/B has been classified into 6 subgenotypes ; HBV/B2‒5 (prevalent in Asia except for in Japan) have undergone recombination with HBV/C in the core promoter/pre‒core/core genomic region, while HBV/B1 (prevalent in Japan) was associated with good prognosis. Herein, we summarize clinical characteristics of HBV genotypes and subgenotypes. |