Fig. 3

Phylogenetic tree of HA1 sequences of A/H3N2 viruses. The tree was constructed using 1000 randomly selected sequences, which showed an apparent selecting preference on the evolutionary path of A/H3N2
Phylogenetic tree of HA1 sequences of A/H3N2 viruses. The tree was constructed using 1000 randomly selected sequences, which showed an apparent selecting preference on the evolutionary path of A/H3N2