Long-term co-circulation of multiple influenza A viruses in pigs, Guangxi, China

Influenza A viruses (IAVs) pose a persistent potential threat to human health because of the spillover from avian and swine infections. Extensive surveillance was performed in 12 cities of Guangxi, China, during 2018 and 2023. A total of 2540 samples (including 2353 nasal swabs and 187 lung tissues) were collected from 18 pig farms with outbreaks of respiratory disease. From these, 192 IAV-positive samples and 19 genomic sequences were obtained. We found that the H1 and H3 swine influenza A viruses (swIAVs) of multiple lineages and genotypes have continued to co-circulate during that time in this region. Genomic analysis revealed the Eurasian avian-like H1N1 swIAVs (G4) still remained predominant in pig populations. Strikingly, the novel multiple H3N2 genotypes were found to have been generated through the repeated introduction of the early H3N2 North American triple reassortant viruses (TR H3N2 lineage) that emerged in USA and Canada in 1998 and 2005, respectively. Notably, when the matrix gene segment derived from the H9N2 avian influenza virus was introduced into endemic swIAVs, this produced a novel quadruple reassortant H1N2 swIAV that could pose a potential risk for zoonotic infection.

甲型流感病毒（Influenza A viruses, IAVs）因可从禽类与猪群感染跨种传播，持续对人类健康构成潜在威胁。2018年至2023年间，研究团队在中国广西壮族自治区的12座城市开展了大规模监测工作。本研究从18个暴发呼吸道疾病的养猪场中共采集2540份样本，其中包括2353份鼻拭子与187份肺组织样本。经检测，从中获得192份甲型流感病毒阳性样本及19条基因组序列。研究发现，在此期间该区域内多谱系、多基因型的H1和H3亚型猪甲型流感病毒（swine influenza A viruses, swIAVs）仍持续共同流行。基因组分析结果显示，欧亚类禽源H1N1亚型猪甲型流感病毒（G4）仍在猪群中占据主导流行地位。值得注意的是，本研究发现新型多基因型H3N2亚型病毒系通过反复引入早期北美三重重配H3N2病毒（TR H3N2 lineage）演化而来，该类病毒分别于1998年和2005年在美国与加拿大出现。尤为关键的是，当源自H9N2亚型禽流感病毒的基质基因片段被引入地方性流行猪甲型流感病毒后，可产生新型四重重配H1N2亚型猪甲型流感病毒，该病毒具备引发人畜共患感染的潜在风险。