Figure 4
From: Spatial, temporal and genetic dynamics of highly pathogenic avian influenza A (H5N1) virus in China
Spatiotemporal distribution of different virus clades isolated from birds in China, 1996–2011. (a) Phylogenetic tree based on H5N1 HA gene sequences. (b) Distribution of H5N1 virus isolated from birds in China, 1996–2011. The definition criteria of clades were developed by the WHO/OIE/FAO H5N1 Evolution Working Group: sharing of a common (clade-defining) node in the phylogenetic tree; monophyletic grouping with a bootstrap value ≥60 at the clade-defining node; and average percentage pairwise nucleotide distances between and within clades of >1.5% and <1.5%, respectively.