Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2000
Publication Date: 7/1/2000
Interpretive Summary: Influenza virus infects many species of animals including both mammals (i.e., humans and pigs) and birds. Influenza that infects birds usually does not infect or cause disease in humans. However, in Hong Kong in 1997, bird influenza infected humans and caused serious disease and death. The source of the bird influenza was the live bird markets of Hong Kong; thus, all poultry in Hong Kong was slaughtered to prevent further spread of the bird influenza to humans. The live bird markets have since been re-established with new poultry and imported birds are tested for influenza. In 1999 bird influenza was detected in geese imported for the live bird markets of Hong Kong. This bird influenza was characterized to determine how similar it was to the 1997 bird influenza that infected humans. Influenza has ten genes, and we found that only one of these genes, hemagglutinin protein, was the same as the 1997 bird influenza. The e1999 bird influenza was very deadly to chickens like the 1997 bird influenza, but caused no disease in mice. These findings suggest that the hemagglutinin gene of both the 1997 and 1999 bird influenza is important in causing disease in chickens but not in mammals, such as humans and mice.
Technical Abstract: Since the outbreak of an avian H5N1 influenza virus in Hong Kong in 1997, poultry entering the Hong Kong live bird markets have been monitored for influenza infection. In 1999, H5N1 avian influenza isolates were obtained through this system and are known as A/Environment/Hong Kong/437/99 (A/Env/HK/437/99).These viruses were characterized and compared to the 1997 7H5N1 Hong Kong isolates. Phylogenetic analysis of all eight gene segments was conducted, and all segments of the A/Env/HK/437/99 isolates were nearly identical and closely related to those of A/Goose/Guangdong/1/96. Only the H5 HA gene of A/Env/HK/437/99 viruses was in the same lineage as the 1997 H5N1 Hong Kong viruses. The pathogenicity of the A/Env/HK/437/99 viruses was evaluated in both chickens and mice, and findings were compared to that of A/Hong Kong/156/97. The A/Env/HK/437/99 viruses were highly pathogenic in chickens, but did not cause clinical disease in mice. Histopathology and dimmunohistochemistry showed distinct differences between the groups of viruses. Mice infected with A/Env/HK/437/99 viruses showed elevated serum levels of activated transforming growth factor-beta.