Characterization of H10 subtype avian influenza viruses isolated from wild birds in South Korea

A total of 13 avian influenza viruses of the H10 subtype were isolated from wild birds in South Korea over the winter season between July 2008 and July 2011. The HA cleavage site of most of the isolated viruses, PEIMQGR↓G was similar to that of H10 viruses (A/turkey/England/384/79 and A/mandarin duck/Singapore/805/93), which are well known to be highly pathogenic in chickens. The exception was the A/mallard/Korea/1242/10(H10N6) virus, which had a PEMMQGR motif. Phylogenetic analysis showed that eight genes of the isolated H10 viruses belonged to the Eurasian lineage, and that the Korean H10 viruses could be divided four genotypes (genotypes A, B, C and D). Chicken challenge studies revealed that most of the H10 viruses did not replicate well through the natural infection route, but a genotype D virus was re-isolated from the brain of a chicken inoculated by the intravenous route. Although H10 viruses have not been isolated from poultry in South Korea, our results emphasize the continuing need to monitor the evolutionary genetics of the influenza virus in wild birds.