Objective  To analyze the long-term trend and spatial clustering of scarlet fever in Changsha, Hunan, 2010－2024, identify key characteristics and priority areas, and provide references for subsequent scientific prevention and control.

Methods  The data of scarlet fever case reports in Changsha from 2010 to 2024 were collected from the Chinese Disease Control and Prevention Information System, and the incidence rate trend of scarlet fever was analyzed by Joinpoint regression, and the incidence rate of towns/streets was scanned by FlexScan spatial clustering to detect the areas with high incidence in each year.

Results  A total of 9 798 cases of scarlet fever were reported in Changsha from 2010 to 2024, with an average annual incidence rate of 7.99/100000. The age range is 3 months to 61 years old, with a median age of onset of 5 years old and the male to female ratio is 1.60∶1. Preschool children account for 49.79%, followed by students at 34.60%. The incidence rate reported from 2010 to 2019 showed an upward trend, with the annual percent change (APC) of 17.92% 95% credibility interval (CI): 8.94%-309.10%. From 2019 to 2024, no significant upward or downward trend was observed, with the APC of −11.71% (95%CI: −49.79%-3.81%). Two annual epidemic peaks were observed, from April to June and from November to January. From 2010 to 2024, the incidence rate of scarlet fever in Changsha county (16.95/100000) ranked first in Changsha. The incidence rate of scarlet fever in Wangcheng district, Liuyang city and Yuelu district showed an overall upward trend, with the average annual percent change of 28.44%, 24.53% and 22.50%, respectively. The spatial scanning analysis shows that the primary gathering areas are mainly concentrated in Xingsha, Quantang, and Xianglong streets in Changsha county (restricted likelihood ratio was 407.94-1359.58, P<0.001). By 2023−2024, they will form the core hotspot area together with Moon Island Street in Wangcheng District and six streets/towns in Liuyang city (Huaichuan, Jili, Hehua, Guankou, Dayao, and Jingang).

Conclusion  The incidence of scarlet fever in Changsha presents a bimodal seasonal pattern of sustained prevalence, with preschool children and students being the high-risk population, and the spatial hotspot area has undergone an evolution from Changsha county to the surrounding areas and formed a stable core area. It is recommended to strengthen surveillance and implement precise interventions for childcare institutions and primary schools in core hotspots during the peak season of the epidemic.