Genetic relatedness of H6 subtype avian influenza viruses isolated from wild birds and domestic ducks in Korea and their pathogenicity in animals

We report the genetic characterization of H6 avian influenza (AI) viruses isolated from domestic ducks and wild birds in Korea between April 2008 and April 2009. A phylogenetic analysis showed that the H6N1 viruses of wild birds and domestic ducks were of the same genotype (K-1) and were similar to the H6N1 virus isolated from a live poultry market in 2003, as six of the eight gene segments of those viruses had a common source. However, the H6N2 viruses of domestic poultry were separated into four genotypes (K-2a, K-2b, K-2c and K-2d) by at least a triple reassortment between influenza viruses of low pathogenicity from Korean poultry (H9N2 and H3N2) and viruses from aquatic birds. In an experimental infection of animals, certain H6 AI viruses replicated well in chickens and mice without pre-adaptation, indicating that H6 virus pathogenicity has the potential to be altered due to multiple reassortments, and that these reassortments could result in interspecies transmission to mammals.