Epidemiological characteristics and etiological surveillance results of influenza in Nanning City from 2013 to 2022
Objective To analyze epidemiological characteristics of influenza in Nanning from 2013 to 2022,to provide a reference for the prevention and control of influenza.Methods The data of influenza incidence and etiology surveillance results of the influenza virus in Nanning from 2013 to 2022 were collected to build a database.Data statistical analysis was performed through SPSS 21.0 and Joinpoint software to explore the epidemic trend and epidemic characteristics of the influenza virus in Nanning,and the seasonal index method was used to analyze the epidemic seasons.Results The reported incidence of influenza in Nanning showed an overall upward trend from 2013 to 2022,with an annual percent change(APC)of 47.63%(P<0.05),and an average annual incidence rate of 84.47/105(ranging from 6.65/105 to 302.55/105).The peak months for influenza in Nanning were January,June,and December,with the seasonal indices of influenza all exceeding 100%,and the proportions of reported cases was 12.69%,29.41%,and 25.97%,respectively.Both male and female incidence rates showed an upward trend without significant difference(P=0.66).The male-to-female case ratio was 1.24∶1,with the highest case distribution in the 5-<10 years age group,accounting for 31.17%,mainly among students,scattered children,and preschoolers.Xixiangtang District reported the largest influenza cases(21.12%),and Xingning District had the highest annual incidence(214.72/105).Influenza outbreaks mainly occurred in schools and kindergartens,accounting for 97.84%;primary schools accounted for 63.07%of the total.From 2013 to 2022,the dominant strains of influenza viruses alternated in Nanning,with a higher proportion of influenza A(H1N1)and(H3N2)viruses from Jan.2013 to Mar.2019.The dominant strains from April 2019 to Dec.2022 were influenza A(H3N2)and B(Victoria)lineage.Conclusions The intensity of the influenza epidemic in Nanning City showed an increasing trend from 2013 to 2022,with obvious seasonality.The dominant subtypes of influenza viruses varied each year.The main affected groups were students and children,and the outbreaks mainly occurred in schools.Therefore,it is necessary to strengthen the prevention and control of influenza in schools,and the timely detection and handling of outbreaks.
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