Analysis of epidemiological characteristics and etiological surveillance results of influenza in Kunming City From 2005 to 2021
Objective To analyze the surveillance results and epidemiological characteristics of influenza in Kunming City from 2005 to 2021,and to provide scientific basis for the formulation and adjustment of influenza prevention and control strategy in Kunming City.Methods Epidemiological analysis of influenza incidence and influenza strain surveillance in Kunming City from 2005 to 2021 was carried out.The difference of strain composition in different populations was tested by Chi-square test,and P＜0.05 was considered as statistically significant.Results There was a fluctuating upward trend of the influenza morbidity in Kunming City from 2005 to 2019.The morbidity and the number of influenza patients reached to the top in 2019 and began to decline in 2020(x2 tren=20 132.699,P＜0.001).The male to female sex ratio was 1.1∶1.Meanwhile,the majority of the patients were children under 5 years old.From 2005 to 2021,a total of 1 520 positive influenza samples were detected in Kunming City,among which,H3(30.7％)and new H1N1(28.5％)accounted for a high proportion.The difference of strain composition between different genders showed no statistically significant(x2=8.363,P=0.079).However,the differences of strain composition among different age groups were statistically significant(x2=122.135,P＜0.001).The main strain of infection among 0-19 years old and over 60 years old age groups was seasonal H3,and the main strain among 20-59 years old age group was new HINI.There were statistical differencesin the composition of influenza strains in each year(x2=1 902.834,P＜0.001).The composition of seasonal H3 strain was higher in each year,and seasonal Hl strain was prevalent before 2009.The proportion of new H1N1 strain was high after 2011,and B type Victoria(BV)and B typeYamagata(BY)strains alternated every 3-4 years.Conclusions There were age differences in the incidence and distribution of influenza strains in Kunming City.We should take targeted prevention and control measures based on the characteristics of influenza in different age groups.
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