No abstract

Surveillance of H9 avian influenza viruses in Korean live-poultry markets from September 2004 through October 2007 was carried out to investigate active reassortment between wild migratory birds and domestic poultry in Korea. Antigenic and phylogenetic analyses showed that most of the isolates belong to the previous Korean H9N2-like lineage and differ from the southeastern Chinese strains. Interestingly, the Ck/Korea/LPM77/06 group (genotype B) and Dk/Korea/LPM248/07 group (genotype C) showed unique properties distinct from those of other Korean H9N2 strains. Although the HA genes of these two groups belong to Korean H9N2-like lineage, the PA genes closely resemble those of the Chinese Y280-like lineage. In addition, the PB2 genes of the Dk/Korea/LPM248/07 group were closely related to those isolated from migratory birds. Several other isolates also clustered within the H9N2 B genotype, an indication that there are at least two predominant H9N2 influenza genotypes in Korea. Another isolate, Dk/Korea/LPM71/06, was identified as an H9N1 subtype, the first ever discovered in Korean live-poultry markets. These findings reveal that reassortment of Korean H9 influenza viruses has occurred frequently in live-poultry markets and may have been mediated by introduction of genetic material from viruses circulating among migratory wild birds to domestic birds. Consequently, the new dominant H9N2 genotypes have become established in Korean live-poultry markets through continued reassortment.

To determine the genetic origins of novel H3 avian influenza viruses of chickens and ducks in Korea, genetic characterization of H3 avian influenza viruses isolated from live poultry markets and migratory aquatic birds in South Korea during 2004–2006 was conducted. Phylogenetic analysis revealed that at least four novel genotypes of H3N2 and two genotypes of H3N6 avian influenza viruses were co-circulating in backyard poultry of Korea. The viruses were reassortants between H9N2 viruses of Korean chickens and unknown influenza viruses of migratory birds. Genetic comparison of H3 viruses from live bird markets with those from wild bird isolates revealed that certain gene segments of wild bird isolates are related closely to those of Korean group H9N2 viruses isolated from live poultry markets in 2003. Furthermore, animal-challenge studies demonstrated that the pathogenicity of certain avian H3 influenza viruses was altered due to reassortment, leading to H3 avian influenza viruses in Korea that can potentially expand their host range to include mammals. These studies emphasize the continuing need to monitor backyard poultry at live poultry markets to better understand interspecies transmission and the emergence of novel influenza viruses that have the potential to infect humans.