Pathogenic Analysis of Influenza Outbreaks in Jiaozuo City,Henan Province from 2018 to 2023

WANG Weihua; ZHANG Yunjie; GAO Yuan

doi:10.3969/j.issn.1004-437X.2025.11.007

Abstract：Objective To analyze the etiological surveillance results of an influenza outbreak in Jiaozuo City,Henan Province from 2018 to 2023,and further analyze the genetic characteristics and variation of influenza virus according to the etiological surveillance.Methods Descriptive analysis was conducted on influenza like cases and pathogen monitoring results in Jiaozuo City,Henan Province from January 2018 to March 2023,and nucleic acid testing and virus isolation were performed.Ten influenza A(H1N1)viruses were isolated and their genetic characteristics were further analyzed by nucleic acid extraction,amplification and sequencing of hemagglutinin(HA)gene.Results Jiaozuo city has tested a total of 277 influenza outbreak specimens from 2018 to 2023,of which 202 were positive,121 were positive for influenza A(59.90％),96 were positive for influenza A H1N1,and 25 were positive for subtype H3N2.B positive was detected in 81 cases(40.10％),Victoria positive in 42 cases,Yamagata positive in 39 cases.From December to May of the following year,influenza A virus dominated,with A(H1N1)as the dominant strain.The positive rate of different monitoring years was compared,the difference was statistically significant(P＜0.05).There was no significant difference in the positive rate of different stypes(P＞0.05).Compared with vaccine strains A/California/07/2009,the nucleotide homology and amino acid homology of HA gene of 10 isolates of influenza A H1N1 virus were 95.8％-97.5％and 92.7％-95.8％respectively.Gene evolution tree analysis showed that the amino acid sequences of the HA gene of the 10 isolates were changed,and the H1N1 influenza virus isolates from different monitoring years had high homology and were closest to the vaccine strain.Glycosylation site analysis showed that there were five glycosylation sites in the antigenic determinant cluster of the 10 isolates,and when compared with the vaccine strain A/California/07/2009,the glycosylation sites in 23NVTV,162NQS,1 in 11NSID,and 2 in 11NSID were missing due to mutations in the T278I site.Compared with the vaccine strain A/California/07/2009,two strains had glycosylation sites at 23NVTV and 162NQS,one strain had glycosylation site at 11NSID,and two strains had a deletion of 276 glycosylation sites due to a mutation at the T278I site.Conclusion The influenza viruses that occurred in Jiaozuo City from 2018 to 2023 mainly occurred from December to May of the following year,and the main strain was influenza A virus,with influenza A H1N1 as the dominant strain.Further analysis show that,compared with the vaccine strains,influenza A H1N1 virus has a high degree of homology,and the antigen determinant and glycosylation site of HA gene are changed to some extent.