Characterization of influenza epidemic in Changzhou City， Jiangsu Province from 2019 to 2023

ObjectiveTo analyze the epidemic intensity and characteristics of influenza in Changzhou City， Jiangsu Province from 2019 to 2023， and to provide scientific evidence for the formulation of influenza prevention and control strategies.MethodsThe surveillance data of influenza surveillance sentinel hospitals in Changzhou City from April 2019 to March 2023 were collected through the China influenza surveillance information system. Influenza-like illness （ILI） cases before and after the pandemic of COVID-19 in Changzhou City were analyzed， and the differences among qualitative data were compared by using χ² test.ResultsFrom April 2019 to March 2023 the percentages of ILI cases’ medical visits in the four-influenza surveillance year were 2.57%， 1.84%， 5.38%， and 3.66%， respectively， and the positive detection rates of influenza virus were 25.71%， 0.44%， 22.78%， and 24.32%， respectively. The number of influenza outbreaks was 61， 1， 23， and 128， respectively. ILI cases were mainly among adolescent children aged 5‒14 years. The percentage of ILI cases in 2020‒2021 after the pandemic of COVID-19 was significantly lower than that in 2019‒2020 （χ2=737.342， P