Objective To understand the epidemiological and etiological characteristics of influenza-like illness (ILI) in Taizhou, Zhejiang province, from 2023 to 2025, and provide scientific evidence for influenza prevention and control.

Methods The surveillance data and etiological testing results of ILI in Taizhou from 2023 to 2025 were collected. Descriptive analysis was conducted on the temporal and age distributions, as well as the etiological characteristics of ILI, χ² test was used to compare differences between groups, and Spearman rank correlation analysis between ILI% and influenza virus positive rate was conducted.

Results The ILI% was 5.77%, 5.05%, and 5.23%, respectively, in Taizhou from 2023 to 2025, the differences were significant (χ²=948.614, P<0.001). The incidence peak varied across different influenza seasons. In the 2022–2023 influenza season, the highest ILI% (21.96%) was observed mainly due to the spread of SARS-CoV-2 (responsible for for 82.82% of positive detections in peak week). In the 2023−2026 influenza seasons, the contribution of SARS-CoV-2 was limited, and the fluctuations in ILI% were mainly attributable to the annual alternation of predominant influenza virus subtypes. Each influenza season exhibited typical winter-spring epidemic characteristics, with the highest incidence being observed in the 2022−2023 influenza season. Age distribution analysis showed that the the highest number of ILI cases were reported in age group 5−14 years (83 058 cases, 31.46%), and the differences among age groups were significant (χ²=1607.512, P<0.001). Etiological surveillance revealed an overall positive rate of 37.65%. In the positive detections, influenza virus accounted for 27.48% and SARS-CoV-2 accounted for 10.17%. The ILI% and influenza virus positive rate showed consistent temporal trends, especially in high-incidence period or weeks (the 13^rd week in 2023, 2023−2024 influenza season and the 48^th-53^nd weeks in 2025), indicating that ILI% mainly reflects influenza activity. Significant positive correlations between ILI% and influenza virus detection were observed across 2023−2025 (r=0.67,0.47 and 0.42; all P < 0.05). However, the correlation between SARS-CoV-2 positive rate and ILI% varied by year.

Conclusions The ILI% fluctuated significantly in Taizhou from 2023 to 2025. Children aged 5−14 years are the key population in influenza prevention and control. The spread of influenza virus has significant impact on ILI%. Continuous strengthening of influenza surveillance and multi-pathogen detection is warranted.