Epidemic patterns of the different influenza virus types and subtypes/lineages for 10 years in Chongqing, China

Abstract

Abstract Objectives To optimize seasonal influenza control and prevention programs in regions with potentially complicated seasonal patterns. Methods Descriptive epidemiology was used to analyze the etiology of influenza, and chi-square tests were used to compare the epidemic patterns among different influenza virus types and subtypes/lineages. Result From January 2010 to December 2019, a total of 63,626 ILI cases were reported in Chongqing and 14,136 (22.22%) were laboratory-confirmed influenza cases. The positive rates of influenza A and influenza B, which were 13.32% and 8.86%, respectively. The positive rate of influenza A reached the highest in winter (23.33%), while the positive rate of influenza B reached the highest in spring (11.88%). Children aged 5-14 years old had the highest positive rates of influenza. The influenza virus types/subtypes positive was significantly different by seasons and age groups (p＜0.001), not by gender (p=0.436). The vaccine strains were matched to the circulating influenza virus strains in all other years except for 2018 (circulating strain was B/Yamagata). Conclusions The study showed significant variations in epidemic patterns, including seasonal epidemic period and age distributions, among different influenza types, subtypes/lineages in Chongqing. Influenza vaccines matched well to the circulating influenza virus strain. In order to prevent and mitigate the influenza outbreak in this area, high risk population, especially children aged 5-14 years, should be encouraged to get vaccinated against influenza before the epidemic season.