Highly pathogenic avian influenza H5N6 and H5N1 viruses of clade 2.3.4.4b were simultaneously introduced into South Korea at the end of 2023. An outbreak at a broiler duck farm consisted of concurrent infection by both viruses. Sharing genetic information and international surveillance of such viruses in wild birds and poultry is critical.
Keywords: H5N1; H5N6; South Korea; clade; duck; highly pathogenic avian influenza virus; influenza; international dissemination; migratory wild birds; poultry; viruses.