Submitted to: Proceedings of the 45th Western Poultry Disease Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/1/1996
Publication Date: N/A
Interpretive Summary: No Interpretive Summary is required. This paper will be for proceedings only.
Technical Abstract: A systematic evaluation was made of the molecular structure of the hemagglutinin (HA) protein of numerous H5N2 avian influenza isolates arising from central Mexico. No two isolates exhibited the same nucleotide sequence for the HA gene and the variation in sequences was not confined to a single region of the protein. Phylogenetic comparisons with h all other known H5 sequences suggests that these strains, as well as recent H5N2 US strains had progenitors in the stable circulating H5 strains of migratory waterfowl. The variation associated with emergence of the highly pathogenic phenotype, namely a single base transition and the insertion/duplication of 6 bases near the proteolytic cleavage site, suggested a mechanism by which virulence might emerge following introduction of avian influenza viruses from migratory waterfowl. Other outbreaks of AI, including those of the H7 subtype, may have involved a similar molecular mechanism. A general model is proposed by which virulence-generating insertions in the HA gene may occur.