Submitted to: Emerging Diseases Veterinary Medicine Agriculture Human Health Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 21, 1999
Publication Date: N/A
Technical Abstract: In 1997, an outbreak of highly pathogenic H5N1 avian influenza virus was detected in poultry in Hong Kong. Viruses from these outbreaks subsequently infected eighteen humans causing severe disease and death in six cases. To prevent a possible influenza pandemic, the chickens of Hong Kong were depopulated at the end of 1997. As part of an ongoing monitoring gprogram of poultry coming into Hong Kong, several H5N1 influenza viruses associated with geese were isolated in March of 1999. Sequence analysis of all eight segments of these H5N1 viruses has been undertaken to determine if these viruses are related to the H5N1 viruses isolated in 1997. The H5 gene of these viruses has high similarity to those of the 1997 outbreak; however, other genes appear to be of a different lineage. Standard pathotyping of these viruses in chickens showed that these viruses were highly pathogenic with a mean death time (MDT) ranging from 3.0 to 4.1 days. However, these viruses were not as deadly as the H5N1 viruses isolated in 1997, which killed chickens with a MDT of 1.0 to 1.5 days. Unlike the H5N1 viruses isolated in 1997, these viruses did not cause clinical signs of disease or death in BALB/c mice. This data suggests that while the hemagglutinin gene is an important determinant in the pathogenicity of avian influenza virus in chickens, other genes are also important for replication in both chickens and mammalian hosts.