Figure 1
Phylogenetic tree of the HA gene of H7N9 influenza A viruses and their origins. (A) Viruses isolated from different Chinese provinces are distinguished by colors. The first column represents the five waves of H7N9 marked with different colors, while the second and last columns denote those viruses collected from humans and specifically from Hubei province. Those H7N9 viruses in Hubei (excluding strain A/Hubei/34007/2015 which was isolated in 2015) province are shown in detail in the dotted boxes and were colored in red. Box 1, the majority of isolates in Hubei province; box 2, the imported strain A/Hubei/1/2016 (highlighted) and its closely related environmental strain (A/Environment/Hubei/12167/2017) from 2017. The tree was rooted with virus A/Shanghai/1/2013. (B) A partial map indicating the routes of viral movement leading to the outbreak in Hubei province. Abbreviations are: HB, Hubei province; AH, Anhui province; JS, Jiangsu province; and ZJ, Zhejiang province. Blue arrow, Hubei strains mainly derived from Zhejiang, Jiangsu and Anhui provinces sampled in wave 5.
