Sequence variation of HA gene of H5N1 influenza viruses at the indicated antigenic sites.

Notes: The amino acid positions are based on mature H5 sequences. Three live viral strains that are included in this study are in bold. Human isolates are in italic. The asterisk indicates a few WHO-recommended vaccine strains. Abbreviations: RBS, receptor binding site; Gly, glycosylation site; BHG, bar-headed goose; Jpn-WE, Japanese white-eye.