Genetic characteristics analysis of influenza A(H1N1) virus in Jiaxing, China, in the postepidemic era
Abstract Background Following the lifting of COVID-19 pandemic control measures, a progressive increase in influenza A virus activity, particularly the H1N1 subtype, has been observed in Jiaxing. This study systematically characterized the genomic evolution of influenza A(H1N1) viruses circulating i...
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2025-07-01
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| Online Access: | https://doi.org/10.1186/s12879-025-11257-y |
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| author | Yin Song Xue Zhang Jimei Ji Lina Li Yamei Zhou Ganglin Ren Shencong Lv Xiaofei Zhang Yong Yan Guoying Zhu |
| author_facet | Yin Song Xue Zhang Jimei Ji Lina Li Yamei Zhou Ganglin Ren Shencong Lv Xiaofei Zhang Yong Yan Guoying Zhu |
| author_sort | Yin Song |
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| description | Abstract Background Following the lifting of COVID-19 pandemic control measures, a progressive increase in influenza A virus activity, particularly the H1N1 subtype, has been observed in Jiaxing. This study systematically characterized the genomic evolution of influenza A(H1N1) viruses circulating in Jiaxing, China during the 2023–2024 epidemic seasons through whole-genome sequencing and phylogenetic analysis. Methods Viral RNA was detected by quantitative real-time PCR (qPCR) and 83 influenza A(H1N1) isolates (48 from 2023 and 35 from 2024 surveillance) were selected for whole-genome sequencing. Launch RDP4, MEGA11 and iTOL were used to analyze the homology, molecular evolutionary clusters and resistance sites of influenza A(H1N1) virus. Results The positivity rates of influenza A(H1N1) virus in Jiaxing were 10.66% in 2023 and 5.09% in 2024, respectively. Compared with vaccine strain A/Wisconsin/67/2022, the influenza A(H1N1) virus in 2023 and 2024 showed high homology, with the nucleotide homology of hemagglutinin gene ranging from 97.9% to 99.2% and that of neuraminidase gene ranging from 98.3% to 99.1%. Among 83 Jiaxing strains, 80 were classified as clade 6B.1A.5a.2a and 3 were assigned to clade 6B.1A.15a.2a.1. These strains were further categorized into subclades C.1 (45), C.1.9(17), C.1.9.3 (18), and D (3). Additionally, an HA/NA reassortant strain (A/ZJNH/SWL1331/2023) was identified in 2023, followed by an oseltamivir-resistant strain (A/ZJPH/SWL1544/2024) carrying the H275Y substitution in 2024. A total of 31 amino acid substitutions were identified in the HA1 segment of Jiaxing influenza A(H1N1) strains, affecting three antigenic sites: Ca (S137P, A139D, A141T/V, R142K, D222G), Cb (L70F, S71F), and Sb (I185S, D187N, S190G), plus an additional Ca1 substitution (K169Q). Conclusions During 2023–2024, multiple genomic sites of influenza A(H1N1) viruses in Jiaxing have acquired mutations, underscoring the need for enhanced continuous surveillance and prevention of H1N1 influenza. |
| format | Article |
| id | doaj-art-c893fdd2aaaa405f89c99a3f7705dfef |
| institution | Kabale University |
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| language | English |
| publishDate | 2025-07-01 |
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| spelling | doaj-art-c893fdd2aaaa405f89c99a3f7705dfef2025-08-20T03:42:30ZengBMCBMC Infectious Diseases1471-23342025-07-0125111110.1186/s12879-025-11257-yGenetic characteristics analysis of influenza A(H1N1) virus in Jiaxing, China, in the postepidemic eraYin Song0Xue Zhang1Jimei Ji2Lina Li3Yamei Zhou4Ganglin Ren5Shencong Lv6Xiaofei Zhang7Yong Yan8Guoying Zhu9Jiaxing Key Laboratory of Pathogenic Microbiology, Jiaxing Center for Disease Control and PreventionTongxiang Center for Disease Control and PreventionJiaxing Key Laboratory of Pathogenic Microbiology, Jiaxing Center for Disease Control and PreventionJiaxing Key Laboratory of Pathogenic Microbiology, Jiaxing Center for Disease Control and PreventionJiaxing Key Laboratory of Pathogenic Microbiology, Jiaxing Center for Disease Control and PreventionJiaxing Key Laboratory of Pathogenic Microbiology, Jiaxing Center for Disease Control and PreventionJiaxing Key Laboratory of Pathogenic Microbiology, Jiaxing Center for Disease Control and PreventionJiaxing Key Laboratory of Pathogenic Microbiology, Jiaxing Center for Disease Control and PreventionJiaxing Key Laboratory of Pathogenic Microbiology, Jiaxing Center for Disease Control and PreventionJiaxing Key Laboratory of Pathogenic Microbiology, Jiaxing Center for Disease Control and PreventionAbstract Background Following the lifting of COVID-19 pandemic control measures, a progressive increase in influenza A virus activity, particularly the H1N1 subtype, has been observed in Jiaxing. This study systematically characterized the genomic evolution of influenza A(H1N1) viruses circulating in Jiaxing, China during the 2023–2024 epidemic seasons through whole-genome sequencing and phylogenetic analysis. Methods Viral RNA was detected by quantitative real-time PCR (qPCR) and 83 influenza A(H1N1) isolates (48 from 2023 and 35 from 2024 surveillance) were selected for whole-genome sequencing. Launch RDP4, MEGA11 and iTOL were used to analyze the homology, molecular evolutionary clusters and resistance sites of influenza A(H1N1) virus. Results The positivity rates of influenza A(H1N1) virus in Jiaxing were 10.66% in 2023 and 5.09% in 2024, respectively. Compared with vaccine strain A/Wisconsin/67/2022, the influenza A(H1N1) virus in 2023 and 2024 showed high homology, with the nucleotide homology of hemagglutinin gene ranging from 97.9% to 99.2% and that of neuraminidase gene ranging from 98.3% to 99.1%. Among 83 Jiaxing strains, 80 were classified as clade 6B.1A.5a.2a and 3 were assigned to clade 6B.1A.15a.2a.1. These strains were further categorized into subclades C.1 (45), C.1.9(17), C.1.9.3 (18), and D (3). Additionally, an HA/NA reassortant strain (A/ZJNH/SWL1331/2023) was identified in 2023, followed by an oseltamivir-resistant strain (A/ZJPH/SWL1544/2024) carrying the H275Y substitution in 2024. A total of 31 amino acid substitutions were identified in the HA1 segment of Jiaxing influenza A(H1N1) strains, affecting three antigenic sites: Ca (S137P, A139D, A141T/V, R142K, D222G), Cb (L70F, S71F), and Sb (I185S, D187N, S190G), plus an additional Ca1 substitution (K169Q). Conclusions During 2023–2024, multiple genomic sites of influenza A(H1N1) viruses in Jiaxing have acquired mutations, underscoring the need for enhanced continuous surveillance and prevention of H1N1 influenza.https://doi.org/10.1186/s12879-025-11257-yInfluenza A(H1N1) virusWhole genome sequencingHemagglutininNeuraminidasePhylogenetic analysis |
| spellingShingle | Yin Song Xue Zhang Jimei Ji Lina Li Yamei Zhou Ganglin Ren Shencong Lv Xiaofei Zhang Yong Yan Guoying Zhu Genetic characteristics analysis of influenza A(H1N1) virus in Jiaxing, China, in the postepidemic era BMC Infectious Diseases Influenza A(H1N1) virus Whole genome sequencing Hemagglutinin Neuraminidase Phylogenetic analysis |
| title | Genetic characteristics analysis of influenza A(H1N1) virus in Jiaxing, China, in the postepidemic era |
| title_full | Genetic characteristics analysis of influenza A(H1N1) virus in Jiaxing, China, in the postepidemic era |
| title_fullStr | Genetic characteristics analysis of influenza A(H1N1) virus in Jiaxing, China, in the postepidemic era |
| title_full_unstemmed | Genetic characteristics analysis of influenza A(H1N1) virus in Jiaxing, China, in the postepidemic era |
| title_short | Genetic characteristics analysis of influenza A(H1N1) virus in Jiaxing, China, in the postepidemic era |
| title_sort | genetic characteristics analysis of influenza a h1n1 virus in jiaxing china in the postepidemic era |
| topic | Influenza A(H1N1) virus Whole genome sequencing Hemagglutinin Neuraminidase Phylogenetic analysis |
| url | https://doi.org/10.1186/s12879-025-11257-y |
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