Phylogenetic tree of the 90 P2-B strains and 5 reference strains from GenBank, based on 81-nucleotide sequences from the RNA polymerase region. The distances were calculated by Kimura's two-parameter method with Clustal X. The tree was drawn by the neighbor-joining method with Clustal X. The asterisks indicate the 19 P2-B strains subjected to sequence analysis of the capsid region. The GenBank accession numbers for reference strains used in this analysis are as follows: Arg320, AF190817; Hawaii virus, U07611; LV, X86557; MxV, U22498; and Snow Mountain Agent, L23831.