Phylogenetic relationships of representative H5N1 influenza virus strains and patient and animal cage isolates (indicated by asterisks) used in this study. A) Hemagglutinin gene (nt positions 29–1650). B) Neuramidase gene (nt positions 28–1323). Gs, goose; GD, Guangdong; Ck, chicken; CN, People's Republic of China; Dk, duck; HK, Hong Kong; HB, Hebei; FJ, Fujian; GZ, Guangzhou; ST, Shantou; HN, Hunan; WDK, wild duck; GX, Guangxi; AH, Anhui; Qa, quail; YN, Yunnan; BH Gs, brown-headed goose; QH, Qinghai; THA, Thailand, NP, Nakhon Pathom; Vnm, Vietnam; ZJ, Zhejiang; Sw, swine. Scale bars show percentage relatedness.