Fig. 2.

Phylogenetic relationships of the polymerase genes PB2 (A) and PB1 (B) of representative influenza A viruses isolated in Eurasia. Analysis was based on nucleotides 1–2,277 of the PB2 gene and 1–2,271 of the PB1 gene. The PB2 and PB1 trees are rooted to equine/Prague/1/56 (H7N7), pintail duck/Alberta/628/79, respectively. The numbers above and below the branch nodes indicate Bayesian posterior probabilities of ≥95 and neighbor-joining bootstrap values of ≥50%, respectively. Red branches indicate H5N1 viruses with H5N1 prototype virus names in red. Virus genotypes are given in parenthesis following the virus names. Major genotypes are indicated with bold text. Lineage names are indicated in normal text: Aquatic, contemporary Eurasia aquatic virus; Ck/Bei, Ck/Beijing/1/94-like (H9N2) virus; Early, 1970s Eurasia aquatic virus; G1, Qa/HK/G1/97-like (H9N2) virus; H9N2, contemporary reassortant H9N2 virus. Scale bar, 0.01 substitutions per site. Abbreviation: AS, African starling; BHG, bar-headed goose; Ck, chicken; Dk, duck; Gf, Guinea fowl; Gs, goose; HK, Hong Kong; MDk, migratory duck; Pa, partridge; Ph, pheasant; Qa, Quail; SCk, silky chicken; ST, Shantou; TS, tree sparrow; Ty, Turkey; WDk, wild duck.