Supragenotypic groups of the hepatitis B virus genome.

Phylogenetic relationships among hepatitis B virus (HBV) genotypes were investigated using different regions across the genome. The phylogenetic analysis in conjunction with graphical examination of phylogenetic distance matrices and distance frequency distribution plotting suggest the clustering of HBV genotypes into three higher-order hierarchical groups: group I, comprising genotypes A-E and G; group II, comprising genotypes F and H; and a hypothetical group III. Present-day genotype G is postulated to be a recombinant with the non-polymerase region of group III virus and the polymerase gene of an ancestral virus belonging to group I.