Figure. Bootstrapped (1,000×) maximum likelihood phylogenetic tree of hemagglutinin genes of avian influenza viruses (H5N1), People’s Republic of China, 2009–2010. Viruses isolated from the plateau pika near Qinghai Lake are indicated by squares; viruses isolated from wild birds in Qinghai Lake Region during 2005–2007 are indicated by triangles; 2009 Qinghai virus submitted to GenBank by the National Avian Influenza Virus Reference Laboratory (Harbin, China) is indicated by the star and in boldface; and viruses isolated in 2009 and 2010 in the Qinghai Lake Region are indicated in boldface, Clade numbers are indicated on the right. NAMRU3, Naval Medical Research Unit 3; Ck, chicken; Dk, duck. Scale bar indicates nucleotide substitutions per site.