{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T05:52:50Z","timestamp":1775713970371,"version":"3.50.1"},"reference-count":33,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T00:00:00Z","timestamp":1775692800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"State Key Laboratory of Veterinary Public Health and Safety","award":["2024SKLVPHS03"],"award-info":[{"award-number":["2024SKLVPHS03"]}]},{"DOI":"10.13039\/100014103","name":"Key Research and Development Program of Shandong Province","doi-asserted-by":"publisher","award":["2025CXPT153"],"award-info":[{"award-number":["2025CXPT153"]}],"id":[{"id":"10.13039\/100014103","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Microbiol."],"abstract":"<jats:p>Swine influenza virus (SIV) is a highly contagious respiratory pathogen in pigs, with bidirectional transmission posing a potential threat to human health. In this study, nasal swab samples were collected from pigs in Shandong Province, China, and yielded an H1N2 SIV strain, designated A\/swine\/Shandong\/QD726\/2021 (H1N2). Whole-genome sequencing was performed for Sw\/SD\/QD726\/2021, and phylogenetic analysis was conducted together with 156 Chinese H1N2 reference sequences obtained from the Global Initiative on Sharing All Influenza Data (GISAID) database and the National Center for Biotechnology Information (NCBI) Influenza Virus Resource database. The results indicated that Sw\/QD726\/2021 represents a novel reassortant genotype (G21), with the HA gene derived from Eurasian avian-like H1N1 (EA H1N1), the NA and NS genes from triple-reassortant H1N2 (TR H1N2), and the remaining internal genes (PB2, PB1, PA, NP, M) from the 2009 pandemic H1N1 (pdm\/09 H1N1). Key amino acid analysis revealed N31 in M2, responsible for adamantane resistance, and S42 in NS1, which influences viral virulence in mouse models. BALB\/c mouse experiments demonstrated efficient viral replication in the lungs and nasal turbinates, accompanied by moderate body weight loss and lung lesions, indicating only moderate pathogenicity. These findings underscore the ongoing evolution of H1N2 SIV in pigs and emphasize the importance of enhanced surveillance and preventive strategies to mitigate public health risks.<\/jats:p>","DOI":"10.3389\/fmicb.2026.1779293","type":"journal-article","created":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T05:20:42Z","timestamp":1775712042000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Genetic characterization of a novel triple-reassortant influenza A (H1N2) virus from pigs, China, 2021"],"prefix":"10.3389","volume":"17","author":[{"given":"Yuzhong","family":"Zhao","sequence":"first","affiliation":[{"name":"College of Veterinary Medicine, Shandong Agricultural University","place":["Tai\u2019an, Shandong, China"]},{"name":"Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control and Prevention, College of Veterinary Medicine, Shandong Agricultural University","place":["Tai\u2019an, Shandong, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Chang","family":"Liu","sequence":"additional","affiliation":[{"name":"College of Veterinary Medicine, Shandong Agricultural University","place":["Tai\u2019an, Shandong, China"]},{"name":"Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control and Prevention, College of Veterinary Medicine, Shandong Agricultural University","place":["Tai\u2019an, Shandong, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Chenlu","family":"Xia","sequence":"additional","affiliation":[{"name":"College of Veterinary Medicine, Shandong Agricultural University","place":["Tai\u2019an, Shandong, China"]},{"name":"Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control and Prevention, College of Veterinary Medicine, Shandong Agricultural University","place":["Tai\u2019an, Shandong, 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Microbiol."},{"key":"ref2","doi-asserted-by":"publisher","first-page":"vex007","DOI":"10.1093\/ve\/vex007","article-title":"Adaptation of avian influenza virus to a swine host","volume":"3","author":"Bourret","year":"2017","journal-title":"Virus Evol."},{"key":"ref3","doi-asserted-by":"publisher","first-page":"7020","DOI":"10.1128\/JVI.00522-11","article-title":"PA residues in the 2009 H1N1 pandemic influenza virus enhance avian influenza virus polymerase activity in mammalian cells","volume":"85","author":"Bussey","year":"2011","journal-title":"J. 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Virol."},{"key":"ref7","doi-asserted-by":"publisher","first-page":"2275","DOI":"10.1007\/s007050170002","article-title":"Universal primer set for the full-length amplification of all influenza A viruses","volume":"146","author":"Hoffmann","year":"2001","journal-title":"Arch. Virol."},{"key":"ref8","doi-asserted-by":"publisher","first-page":"e01716","DOI":"10.1128\/JVI.01716-16","article-title":"The microminipig as an animal model for influenza A virus infection","volume":"91","author":"Iwatsuki-Horimoto","year":"2017","journal-title":"J. Virol."},{"key":"ref9","doi-asserted-by":"publisher","first-page":"1146","DOI":"10.1128\/JVI.01698-07","article-title":"A single-amino-acid substitution in the NS1 protein changes the pathogenicity of H5N1 avian influenza viruses in mice","volume":"82","author":"Jiao","year":"2008","journal-title":"J. Virol."},{"key":"ref10","doi-asserted-by":"publisher","first-page":"747574","DOI":"10.3389\/fimmu.2021.747574","article-title":"Protective efficacy of an Orf virus-vector encoding the hemagglutinin and the nucleoprotein of influenza A virus in swine","volume":"12","author":"Joshi","year":"2021","journal-title":"Front. Immunol."},{"key":"ref11","doi-asserted-by":"publisher","first-page":"327","DOI":"10.1111\/1348-0421.12152","article-title":"Reassortant swine influenza viruses isolated in Japan contain genes from pandemic A(H1N1) 2009","volume":"58","author":"Kanehira","year":"2014","journal-title":"Microbiol. Immunol."},{"key":"ref12","doi-asserted-by":"publisher","first-page":"1123","DOI":"10.1128\/JCM.44.3.1123-1126.2006","article-title":"Identification of human H1N2 and human-swine reassortant H1N2 and H1N1 influenza A viruses among pigs in Ontario, Canada (2003 to 2005)","volume":"44","author":"Karasin","year":"2006","journal-title":"J. Clin. Microbiol."},{"key":"ref13","doi-asserted-by":"publisher","first-page":"345","DOI":"10.1016\/j.vetmic.2013.09.024","article-title":"Reassortants of the pandemic (H1N1) 2009 virus and establishment of a novel porcine H1N2 influenza virus, lineage in Germany","volume":"167","author":"Lange","year":"2013","journal-title":"Vet. Microbiol."},{"key":"ref14","doi-asserted-by":"publisher","first-page":"378","DOI":"10.1016\/j.meegid.2015.06.005","article-title":"Evaluation of the zoonotic potential of a novel reassortant H1N2 swine influenza virus with gene constellation derived from multiple viral sources","volume":"34","author":"Lee","year":"2015","journal-title":"Infect. Genet. Evol."},{"key":"ref15","doi-asserted-by":"publisher","first-page":"1237","DOI":"10.1007\/s00894-007-0245-0","article-title":"Homology modeling and examination of the effect of the D92E mutation on the H5N1 nonstructural protein NS1 effector domain","volume":"13","author":"Li","year":"2007","journal-title":"J. Mol. Model."},{"key":"ref16","doi-asserted-by":"publisher","first-page":"329","DOI":"10.1016\/j.cell.2014.02.040","article-title":"Identification, characterization, and natural selection of mutations driving airborne transmission of A\/H5N1 virus","volume":"157","author":"Linster","year":"2014","journal-title":"Cell"},{"key":"ref17","doi-asserted-by":"publisher","first-page":"8502","DOI":"10.1128\/jvi.74.18.8502-8512.2000","article-title":"Early alterations of the receptor-binding properties of H1, H2, and H3 avian influenza virus hemagglutinins after their introduction into mammals","volume":"74","author":"Matrosovich","year":"2000","journal-title":"J. Virol."},{"key":"ref18","doi-asserted-by":"publisher","first-page":"2511","DOI":"10.1099\/vir.0.000190","article-title":"Replication and transmission of mammalian-adapted H9 subtype influenza virus in pigs and quail","volume":"96","author":"Obadan","year":"2015","journal-title":"J. Gen. Virol."},{"key":"ref19","doi-asserted-by":"publisher","first-page":"152","DOI":"10.3201\/eid2301.161122","article-title":"Whole-genome characterization of a novel human influenza A(H1N2) virus variant, Brazil","volume":"23","author":"Resende","year":"2017","journal-title":"Emerg. Infect. Dis."},{"key":"ref20","doi-asserted-by":"publisher","first-page":"29","DOI":"10.1007\/s00705-014-2223-z","article-title":"A human-like H1N2 influenza virus detected during an outbreak of acute respiratory disease in swine in Brazil","volume":"160","author":"Schaefer","year":"2015","journal-title":"Arch. Virol."},{"key":"ref21","doi-asserted-by":"publisher","first-page":"1068","DOI":"10.3389\/fmicb.2016.01068","article-title":"A novel H1N2 influenza virus related to the classical and human influenza viruses from pigs in Southern China","volume":"7","author":"Song","year":"2016","journal-title":"Front. Microbiol."},{"key":"ref22","doi-asserted-by":"publisher","first-page":"1658","DOI":"10.1099\/vir.0.042648-0","article-title":"Reassortants of pandemic influenza A virus H1N1\/2009 and endemic porcine HxN2 viruses emerge in swine populations in Germany","volume":"93","author":"Starick","year":"2012","journal-title":"J. Gen. Virol."},{"key":"ref23","doi-asserted-by":"publisher","first-page":"1143","DOI":"10.1016\/j.jmb.2005.11.002","article-title":"Glycan microarray analysis of the hemagglutinins from modern and pandemic influenza viruses reveals different receptor specificities","volume":"355","author":"Stevens","year":"2006","journal-title":"J. Mol. Biol."},{"key":"ref24","doi-asserted-by":"publisher","first-page":"101020","DOI":"10.1016\/j.lanmic.2024.101020","article-title":"Genome-scale evolution and phylodynamics of swine influenza A viruses in China: a genomic epidemiology study","volume":"6","author":"Sun","year":"2025","journal-title":"Lancet Microbe"},{"key":"ref25","doi-asserted-by":"publisher","first-page":"17204","DOI":"10.1073\/pnas.1921186117","article-title":"Prevalent Eurasian avian-like H1N1 swine influenza virus with 2009 pandemic viral genes facilitating human infection","volume":"117","author":"Sun","year":"2020","journal-title":"Proc. Natl. Acad. Sci. U.S.A."},{"key":"ref26","doi-asserted-by":"publisher","first-page":"807458","DOI":"10.3389\/fmicb.2021.807458","article-title":"Swine influenza virus infection decreases the protective immune responses of subunit vaccine against porcine circovirus type 2","volume":"12","author":"Sun","year":"2021","journal-title":"Front. Microbiol."},{"key":"ref27","doi-asserted-by":"publisher","first-page":"290","DOI":"10.1186\/1743-422X-10-290","article-title":"Genetic and biological characterisation of an avian-like H1N2 swine influenza virus generated by reassortment of circulating avian-like H1N1 and H3N2 subtypes in Denmark","volume":"10","author":"Trebbien","year":"2013","journal-title":"Virol. J."},{"key":"ref28","doi-asserted-by":"publisher","first-page":"4117","DOI":"10.1128\/JVI.03532-14","article-title":"Mammalian adaptive mutations of the PA protein of highly pathogenic avian H5N1 influenza virus","volume":"89","author":"Yamaji","year":"2015","journal-title":"J. Virol."},{"key":"ref29","doi-asserted-by":"publisher","first-page":"224","DOI":"10.1016\/j.vetmic.2014.11.031","article-title":"Two different genotypes of H1N2 swine influenza virus isolated in northern China and their pathogenicity in animals","volume":"175","author":"Yang","year":"2015","journal-title":"Vet. Microbiol."},{"key":"ref30","doi-asserted-by":"publisher","first-page":"63","DOI":"10.1186\/s12985-022-01794-2","article-title":"Human infection with a reassortant swine-origin influenza A(H1N2)v virus in Taiwan, 2021","volume":"19","author":"Yang","year":"2022","journal-title":"Virol. J."},{"key":"ref31","doi-asserted-by":"publisher","first-page":"278","DOI":"10.1016\/j.bbrc.2009.05.056","article-title":"Isolation and genetic characterization of avian-like H1N1 and novel ressortant H1N2 influenza viruses from pigs in China","volume":"386","author":"Yu","year":"2009","journal-title":"Biochem. Biophys. Res. Commun."},{"key":"ref32","doi-asserted-by":"publisher","first-page":"1038","DOI":"10.1080\/22221751.2021.1912644","article-title":"PB1 S524G mutation of wild bird-origin H3N8 influenza A virus enhances virulence and fitness for transmission in mammals","volume":"10","author":"Zhang","year":"2021","journal-title":"Emerg. Microbes Infect."},{"key":"ref33","doi-asserted-by":"publisher","first-page":"1517023","DOI":"10.3389\/fcimb.2024.1517023","article-title":"Two genotypes of H3N2 swine influenza viruses identified in pigs from Shandong Province, China","volume":"14","author":"Zhao","year":"2024","journal-title":"Front. Cell. Infect. 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