Background/aims: The world-wide distribution of hepatitis B virus (HBV) genotypes follows a geographic pattern under the influence of ethnic background.
Methods: Forty eight core genes from four pacific islands were compared with the following findings.
Results: First, island-specific variant substitutions were found for only two out of four islands. Second, 11 amino acid and 90 nucleotide changes specific for pacific genotypes C and D were defined. Third, the nucleotide diversity of genotype C (all but one were silent) was greater than that of genotype D.
Conclusions: These results suggest an early appearance of genotype C in the pacific with few subsequent amino acid changes because of shared immunological responses across the region followed by random silent changes, some of which reflect isolation of individual island populations. Genotype D appeared later.