To construct an influenza composite index for Guizhou Province and predict the epidemic threshold and graded thresholds for influenza.

Winter-spring influenza surveillance data from the 2017/2018 to 2024/2025 influenza seasons in Guizhou Province were selected. The influenza composite index was constructed using three indicators: the influenza-like illness percentage, influenza nucleic acid positivity rate, and influenza-like illness outbreak count. The moving epidemic method (MEM) was applied to predict the epidemic threshold and graded thresholds for the 2025/2026 influenza season in Guizhou Province. The model performance was evaluated using sensitivity, specificity, and the Youden index.

A total of six influenza seasons (2017/2018, 2018/2019, 2019/2020, 2021/2022, 2023/2024, and 2024/2025) were finally included for constructing the MEM model and conducting early warning analysis. The sensitivity, specificity, and Youden index of the model were 0.90, 0.96, and 0.86, respectively. For the 2025/2026 influenza season, the pre-epidemic threshold was 0.73,the epidemic start week was week 45 of 2025, the end week was week 9 of 2026, and the estimated epidemic duration was 17 weeks.

The constructed influenza composite index demonstrates good performance in assessing influenza epidemic levels in Guizhou Province and can provide a scientific basis for influenza surveillance and early warning in the region.