Phylogenetic analyses and genotypes of H7N9 highly pathogenic avian influenza viruses.
The phylogenetic trees of the HA (A) and NA (B) genes were rooted to A/chicken/Rostock/45/1934 (H7N1) and A/chicken/Italy/22A/1998 (H5N9), respectively. The viruses sequenced in this study are shown in red in the phylogenetic trees. (C) Genotypes of H7N9 and H7N2 viruses and the hosts in which these genotypes were detected. The genotypes of the viruses isolated between February 2017 and January 2018 were reported previously ; the viruses isolated between February 2018 and December 2019 were analyzed in this study. The numbers of strains of each genotype are provided in parentheses.