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The precore mutation G¹⁸⁹⁶→A occurs frequently in anti-HBe-positive carriers of HBsAg with T¹⁸⁵⁸ in the stem of the encapsidation signal. Hepatitis B virus (HBV) genotype F, considered an Amerindian genotype, subdivides into two clades and the precore mutation occurs in Central American F strains. To investigate the relationship between substitutions at position 1858 and these clades, the precore and small S genes of 48 strains of HBV genotype F were subjected to phylogenetic analyses. Isolates of one clade, formed mainly of Central American strains, all had T¹⁸⁵⁸ and Thr⁴⁵ in the S gene, whereas in the other clade, formed mainly of South American strains and one strain from Polynesia, all had C¹⁸⁵⁸ and Leu⁴⁵. The latter strain was related to strains from Venezuela and Colombia, supporting an Amerindian contribution to the Polynesian population. The position of the Polynesian strain in the …