Abstract:

Objective To understand the epidemiological patterns and virological features of influenza in Fuxin City of Liaoning Province，provide scientific basis and theoretical support for future influenza epidemic prevention and control. Methods The epidemiological surveillance data on influenza-like illness（ILI） cases reported by sentinel hospitals in Fuxin City through the China Influenza Surveillance System between 2015 and 2025，along with testing results from influenza network laboratories were collected. The descriptive epidemiological methods and Joinpoint regression modeling were employed to analyze the epidemiological characteristics of ILI and trends in pathogen composition shifts. Results From 2015 to 2025，the proportion of ILI cases in outpatient visits（ILI%） in Fuxin City peaked in the winter to spring season with a single peak each year. The difference in popularity intensity of ILI% was statistically significant among different years（χ²=4 701.169，P<0.01）. The regression models indicated a stable overall trend across the decade. The distribution of ILI% varied by age group，with the majority of cases occurring in individuals aged<15 years old. A total of 793 influenza virus-positive samples were detected over the surveillance period，with influenza A accounting for the majority（66.63%）. The dominant subtypes varied by year，with frequent shifts in predominant strains. The influenza virus positivity was primarily concentrated between December and February of the following year. A positive correlation was observed between monthly ILI% and the influenza positivity rate（r=0.487，P<0.05）. The difference in positive rate of influenza nucleic acid was statistically significant among age groups（χ²=166.747，P<0.01），with the 5-<15 age group showing the highest positivity. Conclusions The influenza activity in Fuxin City demonstrated a consistent winter-spring peak，with children aged 5-<15 years old identified as the primary high-risk group. The alternation of dominant influenza subtypes occurs annually in 10 years. The ILI% peak is closely related to nucleic acid positivity rates，suggesting that timely sample collection during ILI peaks can improve detection rates. The abnormal ILI fluctuations may serve as an early warning indicator. Since 2020，no Yamagata lineage influenza B viruses have been detected，indicating that the trivalent influenza vaccine may offer optimal strain matching.

Key words: Influenza-like illness, Influenza, Influenza virus, Surveillance, Sentinel hospital, Analysis