Figure 3

Entropy plot of the protein consensus ClustalW alignment. Amino acid positions that do not exhibit any changes over the years have entropy of 0, whereas positions of high variability are represented by peak in the plot. Two hot spots of variability were observed and are clustered around amino acid position 140–190, and 200–240. The entropy analysis was performed for the entire hemagglutinin sequence (560 amino acids), but at amino acid position 340 (HA2) the analysis does not exhibit much entropy.