Molecular Analysis of the Avian H7 Influenza Viruses Circulating in South Korea during 2018–2019: Evolutionary Significance and Associated Zoonotic Threats

Abstract

Avian influenza virus (AIV) subtypes H5 and H7, possessing the ability to mutate spontaneously from low pathogenic (LP) to highly pathogenic (HP) variants, are major concerns for enormous socio-economic losses in the poultry industry, as well as for fatal human infections. Through antigenic drift and shift, genetic reassortments of the genotypes pose serious threats of increased virulence and pathogenicity leading to potential pandemics. In this study, we isolated the H7-subtype AIVs circulating in the Republic of Korea during 2018–2019, and perform detailed molecular analysis to study their circulation, evolution, and possible emergence as a zoonotic threat. Phylogenetic and nucleotide sequence analyses of these isolates revealed their distribution into two distinct clusters, with the HA gene sharing the highest nucleotide identity with either the A/common teal/Shanghai/CM1216/2017, isolated from wild birds in Shanghai, China, or the A/duck/Shimane/2014, isolated from Japan. Mutations were found in HA (S138A (H3 numbering)), M1 (N30D and T215A), NS1 (P42S), PB2 (L89V), and PA (H266R and F277S) proteins—the mutations had previously been reported to be related to mammalian adaptation and changes in the virulence of AIVs. Taken together, the results firmly put forth the demand for routine surveillance of AIVs in wild birds to prevent possible pandemics arising from reassortant AIVs.

Identification of specific neutralizing antibodies for highly pathogenic avian influenza H5 2.3.4.4b clades to facilitate vaccine design and therapeutics

“…The spread of AIVs among wild birds has potential consequences for human health and the global poultry industry [ 26–30 ]. HPAIV H5 2.3.4.4 and 2.3.2.1c subclade infections in animals have jumped the species barrier and spread to humans [ 31–33 ].…”

Emergence of Eurasian Avian-Like Swine Influenza A (H1N1) virus in a child in Shandong Province, China

“…The PB2-Q591R, E627K and D701N mutant have been demonstrated to be critical for increasing polymerase activity, and enhancing viral replication and transmissibility in mammalian models [23][24][25][26]. In addition, related studies revealed that the PB2-L89V, R251K and T271K mutation could increase virulence and virus adaptability in mammalian [20][21][22]. Although the A/Shandong-binzhou/01/2021 (H1N1) virus PB2 gene possesses amino acid mutations 89V, 251K, 271K and 591R, the virus strain lacks characteristic human/mammalian amino acid mutations to enhance transmissibility in mammalian, such as E627K and D701N.…”

Surveillance of avian influenza viruses from 2014 to 2018 in South Korea

“…One limitation of our study is that, at the time of writing, the sequences we report are already at least five years old. Several studies have already reported more recent data (2019 to 2022) on circulating avian influenza viruses among wildfowl that visit South Korea, although most have focused on H5-, H7-, and H9-subtype influenza viruses 19 , 31 – 33 . Given the continued threat of AIVs to both animal and human health, large amounts of genetic data are important to allow us to track the movement of avian influenza virus gene pools across time and geographic locations.…”