Objective To analyze the epidemiological characteristics of varicella in Liangjiang new district, Chongqing municipality.

Methods The incidence data of varicella reported in Liangjiang new district from 2015 to 2024 were collected from China Disease Prevention and Control Information System. Joinpoint regression analysis was applied to evaluate the temporal trend of the incidence of varicella, while seasonal index analysis was used to characterize its seasonal distribution of the disease. Spatial autocorrelation analysis and spatiotemporal scan statistics were conducted to detect the spatiotemporal clustering patterns of the reported varicella cases.

Results From 2015 to 2024, a total of 25 936 varicella cases were reported in Liangjiang new district, with the average annual reported incidence rate of 139.74/100 000. The reported incidence showed an increasing trend from 2015 to 2018, with an annual percent change (APC) of 31.99% 95% confidence interval (CI): −23.29%−127.10%, then a decreasing trend from 2018 to 2024, with an APC of −17.54% (95% CI: −28.54%−−4.38%). The overall average annual percent change (AAPC) was −3.54% (95% CI: −17.57% −12.87%). The annual incidence exhibited obvious seasonality with two incidence peaks, one was during May - June and another one was during October - December. The highest incidence rate was reported in age group 10～<15 years during 2023-2024 instead of age group 5−<10 years during 2015—2022. Global spatial autocorrelation analysis indicated a positive global spatial correlation in incidence from 2016 to 2022 and in 2024. Local spatial correlation analysis revealed the presence of local spatial clusters in the reported incidence for each year. High-high clustering areas were mainly distributed in urban areas and showed a shifting trend from southwestern area to northeastern area. Spatiotemporal scan analysis identified five clustering areas (one class I clustering area and four class II clustering area). The class I clustering area was distributed in Huixing community and 9 surrounding communities from January 2018 to December 2020.

Conclusion From 2015 to 2024, the average annual reported incidence rate of varicella was 139.74/100,000 in Liangjiang new dsitrict, showing an increase trend first then a decrease trend and two annual incidence peaks. The age group at high risk shifted from 5～<10 years to 10～<15 years. Significant spatiotemporal clustering was observed, with high-high clustering areas in urban areas and shifting from the southwest to the northeast.