Continued Circulation in China of Highly Pathogenic Avian Influenza Viruses Encoding the Hemagglutinin Gene Associated with the 1997 H5N1 Outbreak in Poultry and Humans

Abstract

Since the outbreak in humans of an H5N1 avian influenza virus in Hong Kong in 1997, poultry entering the live-bird markets of Hong Kong have been closely monitored for infection with avian influenza. In March 1999, this monitoring system detected geese that were serologically positive for H5N1 avian influenza virus, but the birds were marketed before they could be sampled for virus. However, viral isolates were obtained by swabbing the cages that housed the geese.

Emergence of multiple genotypes of H5N1 avian influenza viruses in Hong Kong SAR

“…Since 1999, H5N1 viruses were intermittently isolated from geese (and since 2000, also from ducks) imported into the central slaughter house at the Western Wholesale Food Market (14)(15)(16). By contrast, between April 1999 and December 2000, no H5N1 virus was isolated from 8,626 routine surveillance swabs taken from terrestrial poultry in the retail, live poultry markets in Hong Kong.…”

“…In contrast, prospective virological surveillance and molecular epidemiology carried out on viruses isolated from terrestrial and aquatic poultry in Hong Kong between 1999 and 2001 now allows us to (i) document a series of virus reassortment events associated with a new interspecies transmission of H5N1 viruses from the aquatic avian influenza reservoir to terrestrial poultry, and (ii) gain insight into the genetic events that may have taken place in 1997. Until the year 2000, geese were the reservoir of H5N1 Gs͞Gd-like viruses (14,15). In 2000, these viruses also were isolated from ducks, and in December 2000, H5N1 Gs͞Gd-like viruses isolated from a goose and a duck were found to have acquired internal protein genes (NS, PA, M, and PB2) through reassortment with other aquatic avian virus͞es (16).…”

“…The neuraminidase (NA) of H5N1͞97 is similar to that found in W312-like H6N1 viruses. Although viruses with the gene constellation of H5N1͞97 have not been detected since the poultry slaughter in late 1997, its putative precursors continue to persist in the region-H5N1 Gs͞Gd-like viruses in geese (14)(15)(16) and the H9N2 (G1)-and H6N1 (W312)-like viruses in quail (17,18).…”

Immunogenicity of the inactivated oil emulsion influenza A (H5N1) vaccine in chickens

“…The latest monitoring data reveal circulation and existence of many influenza viruses with different combinations of HA and NA in the poultry population in China. Due to this fact use of subtype NA as a marker for differentiation of infected from vaccinated birds is impossible (Cauthen et al, 2000, He et al, 2003.…”

Protection of chickens against highly lethal H5N1 and H7N1 avian influenza viruses with a recombinant fowlpox virus co-expressing H5 haemagglutinin and N1 neuraminidase genes

“…Additional cases of H7 and H9 AI viruses have been identified in humans and other mammals thus demonstrating that an avian virus could directly cross the species barrier to replicate in mammals and cause severe disease. Currently, avian H5N1 viruses are still active in Hong Kong and other parts of the world, which make it necessary to develop an efficacious vaccine that would protect chickens from multiple subtypes of 1 E-mail: QCHL2001@yahoo.com.cn lethal viruses and prevent the spread of virus (Subbarao et al, 1998;Cauthen et al, 2000).…”