FIG 3.

Schematic diagram of commonly divergent amino acids of the HA and PA genes between airborne-transmissible viruses and viruses that are not airborne transmissible. Differences in the amino acid residues in PA and HA between airborne-transmissible viruses and viruses that are not airborne transmissible are shown as single-letter amino acid codes with their positions at the top of the diagram. The white and black letters indicate the amino acid regions originating from transmissible viruses and nontransmissible viruses, respectively. The amino acid positions of HA are based on the numbering of mature H9 HA.