Fig. 1: Evolutionary history of HACS of the influenza A(H9N2) viruses.

a Maximum likelihood (ML) phylogeny of the H9N2 influenza virus HA gene. The HA gene sequences from all available H9N2 viruses were downloaded from GISAID’s EpiFlu Database for phylogenetic analysis. The ML tree was inferred with the RAxML software under the GTRGAMMA model with 1,000 bootstraps. References H9N2 viruses from each HACS motif are denoted by different colors. The distribution of different HACS motif of influenza A (H9N2) viruses from GISAID’s EpiFlu and GenBank Database. The branch length is scaled according to the numbers of substitutions per site (subs/site). b represents the distribution of the amino acids of HACS except for China, and c represents the amino acids of HACS in China. Different colored bars represent multiple HACS motifs of influenza A(H9N2) viruses. Amino acids frequency of all available HACS of influenza A(H9N2) viruses. Frequencies of each position, from P6 to P4’ of the HACS are illustrated using WebLogo 3.4 (http://weblogo.threeplusone.com/). d represents China, and e represents all countries except for China.