Phylogenetic analysis of swine Hepadnavirus strains and Hepadnaviridae family. The Bayesian phylogenetic tree was constructed by using partial nucleotide sequence of open reading frame S (566 nt) of HBV and related viruses. For each sequence used, the GenBank accession number and country of isolation are shown. Multiple nucleotide sequence alignment was analyzed by using the Markov Chain Monte Carlo method implemented in the program MrBayes version 3.1.2 under GTR + G nucleotide substitution model, selected using the jModeltest program. The tree was rooted at midpoint. Posterior probabilities are shown at the branch label. Newly described swine hepadnavirus sequences are indicated. Scale bar indicates evolutionary distance.