[Genetic characterization of an avian influenza A (H5N1) virus isolated from a sick goose in China].

Genetic analysis of viral HA gene showed that there were 22 nucleotide differences in HA gene between goose and human H5N1 viruses. The sequence analysis of amino acid on viral protein molecules indicated that there were 7 and 9 position differences between goose and human, chicken H5N1 viruses, respectively. All the three viruses share multiple basic amino acids (R-E-R-R-R-K-K-R) at the cleavage site between HA1 and HA2 domain, that is associated with highly pathogenic H5 avian viruses. Except one more glycosylation site located at 156 position in the chicken strain, there were 7 glycosylation sites at same positions in three virus HA protein molecules. The analysis of NA protein molecule indicated that the stalk region which extends from the viral membrane up to amino acid 85, human and chicken viruses had a 19 amino-acid deletion as compared with that of goose virus, while the goose NA gene was closely related to A/Parrot/Ulster/73 (H7N1) virus. Therefore, goose H5N1 virus HA and NA genes were avian in origin and were different from those of human and chicken H5N1 viruses. In our knowledge, this is the first time that the avian H5N1 virus was found causing influenza outbreak in goose. Why was A/Goose/Guangdong/2/96(H5N1) virus virulent for geese? It might be related to the substitution of amino acid located at 138 position near by RBS on HA protein molecule and 19 amino acids insertion on NA protein molecule as compared with those of human and chicken H5N1 viruses.