To analyze the epidemiological and etiological characteristics of influenza-like illness (ILI) in Jinhua City, Zhejiang Province, during the 2017—2024 surveillance years, and to provide a scientific basis for influenza prevention and control in the city.

ILI surveillance data from sentinel hospitals in Jinhua City during 2017—2024 surveillance years (from week 14 of the current year to week 13 of the following year) were collected through the Chinese Influenza Surveillance Information System and analyzed using descriptive epidemiological methods.

During the 2017—2024 surveillance years, a total of 7 748 309 outpatient and emergency visits were reported, including 426 013 ILI cases, with an overall ILI proportion (ILI%) of 5.50%. The highest ILI% was observed in the 2022 surveillance year (8.75%), while the lowest was recorded in the 2024 surveillance year (2.66%). Marked inter-annual fluctuations in ILI activity were noted: single winter peaks occurred in the 2017—2019 surveillance years. The 2021 surveillance year exhibited multiple cross-seasonal peaks. The 2022 surveillance year showed two peaks, one in summer and the other in late winter and early spring. A single winter peak reappeared in the 2023 surveillance year, and no significant epidemic peaks were detected in the 2020 or 2024 surveillance years. ILI cases were predominantly concentrated in the 0-4 years age group, accounting for 53.45% of all reported cases. A total of 18 911 ILI specimens were tested for influenza virus, of which 3 025 were positive, yielding an overall positive rate of 16.00%. Influenza A and B viruses accounted for 71.17% and 28.56% of positive detections, respectively. Among the identified subtypes and lineages, A (H3N2) accounted for 40.89%, followed by A (H1N1) pdm09 (30.28%), B/Victoria lineage (27.17%), and B/Yamagata lineage (1.39%). No B/Yamagata virus was detected after the 2020 surveillance year. Mixed infections accounted for 0.26%. The ILI% was significantly positively correlated with the influenza virus positivity rate in the 2017, 2018, 2019, 2022, and 2023 surveillance years (P<0.001).

Influenza activity in Jinhua City during the 2017—2024 surveillance years exhibited distinct seasonal fluctuations and pronounced inter-annual variability. Influenza activity was markedly suppressed during the implementation of non-pharmaceutical interventions (NPIs) against COVID-19 and rebounded following their relaxation. The predominant strains alternated across surveillance years, with A (H3N2) accounting for the highest proportion, while B/Yamagata lineage was no longer detected after 2020. Further optimization of the influenza sentinel surveillance system, including strengthening multi-pathogen co-surveillance and integrated data analysis, is needed to provide scientific evidence for precision influenza prevention and control.