Objective To analyze the epidemiological characteristics of influenza-like illness (ILI) cases and the distribution patterns of influenza virus types in Xiaogan City from 2020 to 2024, and to provide a scientific basis for local influenza prevention and control.

Methods Data on ILI surveillance reported by two national sentinel hospitals in Xiaogan City and influenza virus detection data reported by the network laboratory of Xiaogan Center for Disease Control and Prevention during 2020‒2024 were collected. All data were stratified and statistically analyzed by time, age and gender. Inter-group differences were compared using the chi-square (χ²) test, and statistical analyses were performed with SPSS 27.0 software.

Results A total of 781 528 outpatient and emergency cases were reported by two sentinel hospitals in Xiaogan City from 2020 to 2024, among which 34 078 were ILI cases, with an ILI proportion (ILI%) of 4.36%. The highest proportion of ILI cases was observed in the 0‒<5 years age group, accounting for 28.62% (9 754/34 078). A total of 11 000 surveillance samples were tested, and 1 515 were positive for influenza virus, with an overall positive rate of 13.77%. Among the positive samples, 724 (47.79%) were influenza A (H3N2) subtype, 232 (15.31%) were influenza A (H1N1) subtype, 554 (36.57%) were influenza B (Victoria lineage), and 5 (0.33%) were mixed infections. A statistically significant difference was found in the seasonal distribution of influenza virus positivity rate (χ²=9 120.63, P<0.001). Epidemic peaks mainly occurred in winter and spring, with positivity rates ranging from 42.22% to 76.62%, while summer epidemic peaks were observed only in 2021 and 2022 (positivity rate was 21.48% and 43.03%, respectively). A statistically significant difference was also observed in influenza virus positivity rate among different age groups (χ²=846.61, P<0.001), with the highest influenza positive rate in the 5‒<15 years age group. No statistically significant difference was found in gender distribution (χ²=2.43, P=0.650).

Conclusion The influenza epidemic season in Xiaogan City is mainly in winter and spring, with occasional summer peaks. Prevention and control efforts should focus on children and adolescents aged 5 to <15 years, and targeted measures should be adopted in key settings such as schools. It is necessary to continuously strengthen influenza surveillance to provide a scientific basis for formulating prevention and control strategies.