Multiple Reassortants of H5N8 Clade 2.3.4.4b Highly Pathogenic Avian Influenza Viruses Detected in South Korea during the Winter of 2020–2021

Abstract

During October 2020–January 2021, we isolated a total of 67 highly pathogenic avian influenza (HPAI) H5N8 viruses from wild birds and outbreaks in poultry in South Korea. We sequenced the isolates and performed phylogenetic analysis of complete genome sequences to determine the origin, evolution, and spread patterns of these viruses. Phylogenetic analysis of the hemagglutinin (HA) gene showed that all the isolates belong to H5 clade 2.3.4.4 subgroup B (2.3.4.4b) and form two distinct genetic clusters, G1 and G2. The cluster G1 was closely related to the 2.3.4.4b H5N8 HPAI viruses detected in Europe in early 2020, while the cluster G2 had a close genetic relationship with the 2.3.4.4b H5N8 viruses that circulated in Europe in late 2020. A total of seven distinct genotypes were identified, including five novel reassortants carrying internal genes of low pathogenic avian influenza viruses. Our Bayesian discrete trait phylodynamic analysis between host types suggests that the viruses initially disseminated from migratory waterfowl to domestic duck farms in South Korea. Subsequently, domestic duck farms most likely contributed to the transmission of HPAI viruses to chicken and minor poultry farms, highlighting the need for enhanced, high levels of biosecurity measures at domestic duck farms to effectively prevent the introduction and spread of HPAI.

Pathogenicity of H5N8 High Pathogenicity Avian Influenza Virus in Chickens and Ducks from South Korea in 2020–2021

“…From the winter of 2020–2021 until April 2021, 109 outbreaks in poultry and 234 cases in wild birds reported (based on data from Korean Animal Health Integrated System (KAHIS)). H5N8 HPAI viruses from the 2020–2021 outbreak revealed to have at least seven genotypes [ 15 ]. The H5N8 HPAI virus that first circulated during the 2020–2021 outbreak in Korea is genetically close to viruses reported in Europe during 2019–2020 [ 15 , 16 , 17 , 18 ].…”

“…H5N8 HPAI viruses from the 2020–2021 outbreak revealed to have at least seven genotypes [ 15 ]. The H5N8 HPAI virus that first circulated during the 2020–2021 outbreak in Korea is genetically close to viruses reported in Europe during 2019–2020 [ 15 , 16 , 17 , 18 ]. Major H5N8 viruses that circulated later during the 2020–2021 outbreak have a close genetic relationship with viruses detected in Europe in late 2020 [ 15 ].…”

Temporal Dynamics of Influenza A(H5N1) Subtype before and after the Emergence of H5N8

“…Different genotypes of this virus (carrying variable internal gene segments) were subsequently identified and disseminated via the migration of wild birds to many countries in Europe, Asia, and Africa within a few months, causing the most widespread epidemic by HPAI virus since the H5N1 epidemic in 2005 [ 23 , 24 ]. In 2020–2021, HPAI H5N8 viruses were again spreading rapidly, and were responsible for >1000 outbreaks in 25 countries, mainly in Europe [ 25 , 26 ]. The new HPAI H5N8 virus was reported to have genetic similarity and phylogenetic relatedness with H5N8 viruses currently circulating in Egypt [ 25 ].…”

Parallel Outbreaks of Deadly Pathogens (SARS-CoV-2, H5N8, EVD, Black fungi) around the World in 2021: Priorities for Achieving Control with Socio-Economic and Public Health Impact

“…Along with all possible attempt, the global initiative on sharing avian influenza data (GISAID) has set up the platform to gather and share all available sequence data for providing a better understanding of the epidemiology and evolution of the currently circulating viruses including the H5N8. Also, flu surveillance laboratories have been established in more than 50 countries worldwide [61].…”