A new group of hepadnaviruses naturally infecting orangutans (Pongo pygmaeus)

A high prevalence (42.6%) of hepatitis B virus (HBV) infection was suspecte d in 195 formerly captive orangutans due to a large number of serum samples which cross-reacted with human HBV antigens,It was assumed that such viral infections were contracted from humans during captivity. However, two wild orangutans were identified which were HBV surface antigen positive, indica ting that HBV or related viruses may be occurring naturally in the oranguta n populations. Sequence analyses of seven isolates revealed that orangutans were infected with hepadnaviruses but that these mere clearly divergent fr om the six known human HBV genotypes and those of other nonhuman hepadnavir uses reported. Phylogenetic analyses revealed geographic clustering with So utheast Asian genotype C viruses and gibbon ape HBV. This implies a common origin of infection within this geographic region, with cross-species trans mission of hepadnaviruses among hominoids.