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Lee SH, Kwon JH, Youk S, Lee SW, Lee DH, Song CS. Epidemiology and pathobiology of H5Nx highly pathogenic avian influenza in South Korea (2003-2024): a comprehensive review. Vet Q 2025; 45:23-38. [PMID: 40332021 PMCID: PMC12064103 DOI: 10.1080/01652176.2025.2498918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2025] [Revised: 03/31/2025] [Accepted: 04/23/2025] [Indexed: 05/08/2025] Open
Abstract
Since their emergence in Guangdong, China, in 1996, Gs/GD H5 highly pathogenic avian influenza viruses (HPAIVs) have diversified into multiple clades, spreading globally through wild bird migrations and causing substantial losses in poultry and wildlife. In South Korea, HPAIVs, including H5N1, H5N8, and H5N6 subtypes, have been repeatedly introduced since 2003. This review examines the epidemiology, genetic characteristics, and pathobiological features of these viruses in South Korea. Outbreaks typically occur between October and December, aligning with the arrival of wintering migratory birds. While outbreaks in poultry farms dominated before 2018, wild bird cases became more prevalent in subsequent years. Seasonal outbreaks in poultry have declined, but large-scale mortality events in wild birds emerged biennially from 2020. Genotypic diversity has increased since 2014 due to reassortment with low pathogenic viruses, with novel genomic traits detected in recent seasons. Infection studies show consistently fatal outcomes in chickens, while high mortality in domestic ducks was observed only with two of the studied strains, despite efficient transmission. Wild bird studies reveal species-specific roles in viral shedding and transmission. This review underscores the dynamic nature of HPAI outbreaks, highlighting the importance of surveillance, biosecurity, and genetic and pathogenicity analyses to mitigate future risks.
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Affiliation(s)
- Sun-Hak Lee
- Avian Disease Laboratory, College of Veterinary Medicine, Konkuk University, Seoul, Republic of Korea
- Wildlife Health Laboratory, College of Veterinary Medicine, Konkuk University, Seoul, Republic of Korea
| | - Jung-Hoon Kwon
- Laboratory of Veterinary Microbiology, College of Veterinary Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Sungsu Youk
- Department of Microbiology, College of Medicine, Chungbuk National University, Cheongju-si, Republic of Korea
| | - Sang-Won Lee
- College of Veterinary Medicine, Konkuk University, Seoul, Republic of Korea
| | - Dong-Hun Lee
- Wildlife Health Laboratory, College of Veterinary Medicine, Konkuk University, Seoul, Republic of Korea
| | - Chang-Seon Song
- Avian Disease Laboratory, College of Veterinary Medicine, Konkuk University, Seoul, Republic of Korea
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Cha RM, Park MJ, Baek YG, Lee YN, Jang Y, Kang YM, Heo GB, An SH, Lee KN, Kim JK, Kim HR, Lee YJ, Lee EK. Genetic characteristics and pathogenesis of clade 2.3.4.4b H5N1 high pathogenicity avian influenza virus isolated from poultry in South Korea, 2022-2023. Virus Res 2025; 353:199541. [PMID: 39894372 PMCID: PMC11850744 DOI: 10.1016/j.virusres.2025.199541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2024] [Revised: 01/31/2025] [Accepted: 01/31/2025] [Indexed: 02/04/2025]
Abstract
During the 2022-2023 winter season in South Korea, a novel clade 2.3.4.4b H5N1 HPAIV was first detected in wild birds, which then subsequently caused multiple outbreaks in poultry farms and wild birds. This study aimed to investigate the genetic characteristics of H5N1 HPAIVs isolated during the 2022-2023, along with their pathogenicity and transmissibility in chickens and ducks. The clade 2.3.4.4b H5N1 HPAIV viruses caused outbreaks in 75 poultry farms and detected in 174 wild bird cases. Phylogenetic analysis of hemagglutinin genes revealed that the South Korean H5N1 HPAIV isolates were closely related to Eurasian and American HPAIVs isolated between 2022 and 2023. In total, 21 diverse genotypes (22G0-22G20) were identified in virus isolates from poultry and wild birds, among which 22G7 was the dominant genotype. The 22G1 genotype (A/duck/Korea/H493/2022(H5N1)) caused high virulence and pathogenicity, with a 100 % mortality rate in specific-pathogen-free chickens. Ducks inoculated with genotypes 22G1 or 22G7 (A/duck/Korea/H537/2022(H5N1)) showed neurological signs, with 60 %-80 % mortality rate. In the contact groups of ducks, 100 % of transmissibility was observed. Notably, in the 22G7-inoculated group, viral shedding via the cloacal route was longer, and viral replication in the cecal tonsil was higher than that in the 22G1-inoculated group, which may have contributed to the dominancy of the 22G7 genotype. Therefore, better understanding of the genetic and pathogenic features of HPAI viruses is important for effective virus control in the field.
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Affiliation(s)
- Ra Mi Cha
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Min-Ji Park
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Yoon-Gi Baek
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Yu-Na Lee
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Yunyueng Jang
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Yong-Myung Kang
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Gyeong-Beom Heo
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Se-Hee An
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Kwang-Nyeong Lee
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Jae-Kyeom Kim
- Avian Disease Research Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Hye-Ryoung Kim
- Avian Disease Research Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Youn-Jeong Lee
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea
| | - Eun-Kyoung Lee
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, South Korea.
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Seo YR, Cho AY, Si YJ, Lee SI, Kim DJ, Jeong H, Kwon JH, Song CS, Lee DH. Evolution and Spread of Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus in Wild Birds, South Korea, 2022-2023. Emerg Infect Dis 2024; 30:299-309. [PMID: 38215495 PMCID: PMC10826760 DOI: 10.3201/eid3002.231274] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2024] Open
Abstract
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.
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Cha RM, Lee YN, Park MJ, Baek YG, Shin JI, Jung CH, Sagong M, Heo GB, Kang YM, Lee KN, Lee YJ, Lee EK. Genetic Characterization and Pathogenesis of H5N1 High Pathogenicity Avian Influenza Virus Isolated in South Korea during 2021-2022. Viruses 2023; 15:1403. [PMID: 37376703 PMCID: PMC10304347 DOI: 10.3390/v15061403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 06/16/2023] [Accepted: 06/16/2023] [Indexed: 06/29/2023] Open
Abstract
High pathogenicity avian influenza (HPAI) viruses of clade 2.3.4.4 H5Nx have been circulating in poultry and wild birds worldwide since 2014. In South Korea, after the first clade 2.3.4.4b H5N1 HPAI viruses were isolated from wild birds in October 2021, additional HPAIV outbreaks occurred in poultry farms until April 2022. In this study, we genetically characterized clade 2.3.4.4b H5N1 HPAIV isolates in 2021-2022 and examined the pathogenicity and transmissibility of A/mandarin duck/Korea/WA585/2021 (H5N1) (WA585/21) in chickens and ducks. Clade 2.3.4.4b H5N1 HPAI viruses caused 47 outbreaks in poultry farms and were also detected in multiple wild birds. Phylogenetic analysis of HA and NA genes indicated that Korean H5N1 HPAI isolates were closely related to Eurasian viruses isolated in 2021-2022. Four distinct genotypes of H5N1 HPAI viruses were identified in poultry, and the majority were also found in wild birds. WA585/21 inoculated chickens showed virulent pathogenicity with high mortality and transmission. Meanwhile, ducks infected with the virus showed no mortality but exhibited high rates of transmission and longer viral shedding than chickens, suggesting that they may play an important role as silent carriers. In conclusion, consideration of both genetic and pathogenic traits of H5N1 HPAI viruses is required for effective viral control.
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Affiliation(s)
- Ra Mi Cha
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Yu-Na Lee
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Min-Ji Park
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Yoon-Gi Baek
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Jae-In Shin
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Chang Hwa Jung
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Mingeun Sagong
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Gyeong-Beom Heo
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Yong-Myung Kang
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Kwang-Nyeong Lee
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Youn-Jeong Lee
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
| | - Eun-Kyoung Lee
- Avian Influenza Research & Diagnostic Division, Animal and Plant Quarantine Agency, 177 Hyeoksin 8-ro, Gyeongsangbuk-do, Gimcheon-si 39660, Republic of Korea
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