Avian influenza viruses in Korean live poultry markets and their pathogenic potential.

We surveyed live-poultry markets in Korea in 2003 and isolated 9 H9N2, 6 H3N2, and 1 H6N1 influenza viruses. Antigenic and phylogenetic analyses showed that all 9 H9N2 isolates were of A/Chicken/Korea/25232-96006/96-like lineage (which caused disease in chickens in Korea in 1996) but were different from H9N2 viruses of southeastern China. They had at least 4 genotypes and replicated in chickens but not in mice. The H3N2 and H6N1 viruses were new to Korea and were probably reassortants of avian influenza viruses from southeastern China and recent Korean H9N2 viruses. All 8 segments of the H3N2 viruses formed a single phylogenetic cluster with 99.1 to 100% homology. The H3N2 viruses replicated in chickens and mice without preadaptation, but the H6N1 virus did not. Our results show an increasingly diverse pool of avian influenza viruses in Korea that are potential pandemic influenza agents.