Epidemiological characteristics and incidence trend of influenza like illness in Hebei, 2010−2020

  Objective  To understand the epidemiological characteristics and incidence trend of influenza like illness (ILI) in Hebei province from 2010 to 2020 and provide evidence for the development of influenza prevention and control strategies.

  Methods  The 2010−2020 ILI surveillance data in Hebei were collected for a descriptive analysis. Software joinpoint was used to construct a piecewise point linear regression model with the surveillance year as the independent variable and the proportion of ILI cases as the dependent variable to explore the incidence trends of ILI in different age groups and areas.

  Results  The proportion of ILI cases in Hebei from 2010 to 2020 was 1.84%, and the incidence of ILI and the proportion of ILI cases mainly peaked during winter-spring; the cases in children under age of 15 years accounted for the highest proportion (about 67.3%); The incidences in Langfang, Baoding, Chengde, Shijiazhuang and Handan were high. The proportion of ILI cases in Hebei began to change during 2016−2017, showing a trend of “decrease-rapid increase” (APC=−3.34% and 18.62%); the proportion of ILI cases in 0-year-old group and the 5-year-old group showed a trend of “decrease-rapid increase”, the proportion of ILI cases in 25-year-old group and the 60-year-old group showed a slow increase trend (APC=0.03% and 0.01%). Except Handan, Chengde, and Shijiazhuang, the proportion of ILI cases other prefectures showed an overall increase, and the linear structure of regression varied.

  Conclusion  The incidence of ILI in Hebei showed a peak in winter and spring. The proportion of ILI cases in Hebei showed a “decline-rapid increase” during 2010 to 2020. The change trends of ILI case proportion in each age group under 15 years old were similar to the overall trend; except Baoding, Xingtai, Zhangjiakou, the trend of the proportions of ILI cases in other areas were partially or completely consistent with the overall trend. Joinpoint regression model can reveal the incidence trend of ILI in different populations, and provide a basis for better targeted influenza prevention and control of ILI.