Molecular analysis of the haemagglutinin gene of an avian H1N1 influenza virus

This study presents the first nucleotide sequence and deduced primary amino acid sequence of a subtype H1 haemagglutinin from the avian influenza virus A/duck/ Alberta/35/76 (H1N1). The molecule is structurally, antigenically and molecularly similar to H1 haemagg-lutinins of human viruses but sequence homology differences indicate that there has not been a recent transfer of haemagglutinin genetic information between them. The sudden appearance ofpandemic strains of influenza A viruses in the human population led to the develop-ment of the hypothesis that these 'new ' viruses may arise by genetic reassortment between human strains and influenza viruses from other mammals or birds (Laver & Webster, 1979). The close genetic and antigenic relation