Hemagglutinin mutation D222N of the 2009 pandemic H1N1 influenza virus alters receptor specificity without affecting virulence in mice.

•The D222N hemagglutinin mutation within the receptor-binding site was detected with higher frequencies in severe cases of 2009 pandemic H1N1 infections.•The D222N alters receptor specificity and does not change the virulence.•The results implied that the receptor specificity may not linked to pathogenicity.