Evolution and Spread of Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus in Wild Birds, South Korea, 2022–2023

• Published in: Emerging Infectious Diseases
• Main Authors: Ye-Ram Seo, Andrew Y. Cho, Young-Jae Si, Song-I Lee, Dong-Ju Kim, Hyesung Jeong, Jung-Hoon Kwon, Chang-Seon Song, Dong-Hun Lee
• Format: Article in Journal/Newspaper
• Language: English
• Published: Centers for Disease Control and Prevention 2024
• Subjects: influenza; highly pathogenic avian influenza virus; H5N1; clade 2.3.4.4b; wild bird; South Korea; Medicine; R; Infectious and parasitic diseases; RC109-216; Cygnus cygnus
• Online Access: https://doi.org/10.3201/eid3002.231274; https://doaj.org/article/0aa51e0ca305439bb5de1dc529f0008a

During October 2022–March 2023, highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b virus caused outbreaks in South Korea, including 174 cases in wild birds. To understand the origin and role of wild birds in the evolution and spread of HPAI viruses, we sequenced 113 HPAI isolates from wild birds and performed phylogenetic analysis. We identified 16 different genotypes, indicating extensive genetic reassortment with viruses in wild birds. Phylodynamic analysis showed that the viruses were most likely introduced to the southern Gyeonggi-do/northern Chungcheongnam-do area through whooper swans (Cygnus cygnus) and spread southward. Cross-species transmission occurred between various wild bird species, including waterfowl and raptors, resulting in the persistence of HPAI in wild bird populations and further geographic spread as these birds migrated throughout South Korea. Enhanced genomic surveillance was an integral part of the HPAI outbreak response, aiding in timely understanding of the origin, evolution, and spread of the virus.