Phylogenetic trees of virus genes isolated from tree sparrows in China. Trees were generated by using neighbor-joining analysis with the Tamura-Nei-gamma model in the MEGA program (version 2.0). Numbers below branches indicate bootstrap value percentages from 1,000 replicates. Analysis was based on nucleotides 1 to 1,012 (1,012 bp) of the HA gene, 1 to 1,055 (1,055 bp) of the NA gene, 1,058 to 2,227 (1,170 bp) of the PB2 gene, 23 to 1,316 (1,294 bp) of the PB1 gene, 1,450 to 2,148 (699 bp) of the PA gene, 22 to 976 (955 bp) of the NP gene, 25 to 759 (725 bp) of the M gene, and 46 to 685 (640 bp) of the NS gene. The scale bar represents the distance unit between sequence pairs. Th, Thailand; VN, Vietnam; In, Indonesia; HK, Hong Kong; Gd, Guangdong; YN, Yunnan; Sh, Shanghai; Sd, Shandong; ST, Shantou; Ck, chicken; Dk, duck; Qa, quail; Gs, Goose; SCk, silky chicken. The sequences are named in concordance with their GenBank nomenclature. The tree sparrow genes are indicated in red.

Possible derivation of the tree sparrow viruses and their relationship to other H5N1 genotypes. The eight gene segments in each schematic virus particle are (from top to bottom) the PB2, PB1, PA, HA, NP, NA, M, and NS genes. Genes of the same lineage are shown in the same color. The capital letters indicate the genotypes and Sparrow 1 to Sparrow 4 indicate the four sparrow isolates.