Figure 1From: Identification of hemagglutinin structural domain and polymorphisms which may modulate swine H1N1 interactions with human receptorPhylogeny of HA gene sequences of H1N1 and H1N2 viruses infecting humans. Human cases of H1 swine that infected humans between 1976 and 2007 (black square); avian species (H1); seasonal human H1N1 influenza (black triangle), representative strains of Novel A/H1N1 influenza and H1N2 viruses (asterisk).Back to article page