Epidemiological and genetic characteristics of school influenza outbreaks in Changzhou from 2021 to 2024
10.3760/cma.j.cn112866-20250725-00154
- VernacularTitle:2021—2024年常州市学校流感疫情病原学及基因特征分析
- Author:
Qiong LI
1
;
Jingyi JIANG
1
;
Li GONG
1
;
Jian XU
1
;
Xujian MAO
1
;
Fengming WANG
1
;
Ping YAO
1
Author Information
1. 常州市疾病预防控制中心病原生物检验科，常州 213022
- Publication Type:Journal Article
- Keywords:
Influenza;
Outbreak in clusters;
Epidemiology;
Genetic characteristics
- From:
Chinese Journal of Experimental and Clinical Virology
2025;39(5):617-622
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To characterize the etiological and genetic features of pediatric influenza outbreaks in Changzhou between 2021 and 2024，with the goal of informing evidence-based prevention strategies and guiding effective management of influenza outbreaks in school settings.Methods:During the period of 2021 to 2024，throat swabs of influenza-like cases from school outbreaks in Changzhou were collected. These samples underwent real-time reverse transcription-polymerase chain reaction（RT-PCR）testing and virus isolation. Epidemiological data were integrated to conduct pathogenetic analysis. The HA genes of isolated strains were amplified and sequenced to perform genetic characterization.Results:Between 2021 and 2024，a total of 256 influenza outbreaks were reported in schools in Changzhou. A total of 3 201 specimens were collected，of which 2 245 were tested positive for influenza viruses，resulting in a positivity rate of 70.13%. The outbreak season was primarily concentrated from December to February each year，with settings predominantly distributed in primary schools（accounting for 73.83%）. The predominant epidemic strains were influenza A viruses，including 118 outbreaks caused by H1N1 and 104 by H3N2. A total of 74 influenza virus strains were successfully isolated from positive specimens，and sequencing of the hemagglutinin（HA）gene was completed. Phylogenetic analysis revealed that certain B/Victoria lineage strains（e.g.，B/Changzhou/01/2021）clustered closely with the vaccine strain B/Austria/3594/17（bootstrap support：99%）. Among influenza H1N1 strains，multiple isolates from 2023—2024 clustered within the same major branch as A/Victoria/4897/2022（bootstrap support：100%）. In contrast，the H3N2 strains exhibited a complex evolutionary pattern，showing variable genetic distances to vaccine strains from different years（e.g.，A/Massachusetts/18/2022，A/Darwin/6/2021）；some isolates were closely related to vaccine strains，while others were more distantly related and scattered across the phylogenetic tree.Conclusions:The influenza outbreak situation in schools was severe and has significant public health implications. Continuous surveillance is essential，and preventive strategies should be promptly adjusted based on the epidemiological and genetic characteristics of circulating strains.
