Epidemiological characteristics and influencing factors of school influenza-like illness outbreaks in Chongqing from 2012 to 2022

Yang Shuang; Qi Li; Long Jiang; Xiong Yu; Yang Jule; Li Tingting; Fu Xiaoqing; Zhou Ailin; Zhao Yong

doi:10.11986/j.issn.1673-873X.2025.01.02

Abstract：Objective To analyze the epidemiological characteristics and influencing factors of school influenza-like illness(ILI)outbreak epidemics in Chongqing municipality during 2012-2022,and to provide evidence for the formulation of pre-vention and control measures.Methods Data were obtained from the China Influenza Surveillance Information System and the Public Health Emergency Reporting and Management Information System.Descriptive statistical methods were used to analyze the epidemiological characteristics of school ILI outbreak epidemics in Chongqing from 2012 to 2022.Results Dur-ing 2012-2022,a total of 246 school ILI outbreak epidemics were recorded in Chongqing,with 7,869 reported cases.The incidence rate ranged from 0.27%to 44.74%,showing an overall upward trend.A total of 3,902 respiratory samples were collected,with an overall positive detection rate of influenza virus nucleic acid of 76.01%.The epidemic peaks mainly oc-curred in the winter-spring season,with a duration of(17.71±11.06)days.Outbreaks were primarily distributed in the southeastern and northeastern regions of Chongqing,accounting for 65.44%of the total number of outbreaks.The primary sites of occurrence were concentrated in primary schools,with primary school outbreaks accounting for 63.82%overall.During 2012-2022,both type A and type B influenza viruses were detected,with two or more types of influenza viruses cir-culating each year.The dominant strains mainly showed a trend of alternation among type A H1 N1,type A H3 N2,and type B BV.Conclusion School ILI outbreak epidemics are relatively common in Chongqing,primarily among school-age children aged 6-17 years,with rural primary schools being the high-incidence sites.It is recommended that relevant depart-ments strengthen influenza surveillance,monitor real-time influenza dynamics,epidemic trends,and viral mutations,and raise the coverage of influenza vaccination among school-age children.