To establish the epidemic thresholds and intensity classification criteria for varicella in Sichuan Province by applying the Moving Epidemic Method (MEM), so as to provide a scientific basis for precision prevention and control.

Based on the weekly incidence data of varicella in Sichuan Province from 2014 to 2024, obtained from the China Information System for Disease Control and Prevention, the MEM model was constructed separately for each epidemic season, accounting for its characteristic bimodal peaks (the spring-summer peak from week 8 to week 34 and the autumn-winter peak from week 35 to week 7 of the following year). The optimal parameter (δ) was determined through cross-validation. Model performance was evaluated using sensitivity, specificity, and the Youden index.

In the autumn-winter model, after excluding data from weeks 35 to 7 of the 2014-2015 season, the model was built based on nine years of historical data (δ=2.9), yielding a sensitivity of 0.837, a specificity of 0.933, and a Youden index of 0.770. In the spring-summer model, after excluding data from weeks 8 to 34 of 2020, the model was constructed using nine years of historical data (δ=2.6), which resulted in a sensitivity of 0.902, a specificity of 0.943, and a Youden index of 0.845.

The seasonal stratification approach combined with the MEM epidemic intensity assessment model enables accurate identification of varicella epidemic periods in Sichuan Province, thereby providing a scientific basis for implementing differentiated prevention and control measures based on epidemic intensity levels.