Epidemiological characteristics and spatiotemporal analysis of scarlet fever in Guangzhou, China: the surveillance of 20 years

BACKGROUND: This study investigated the epidemiological and spatiotemporal characteristics of scarlet fever in Guangzhou, China, and provided a scientific basis for the formulation and optimization of prevention and control strategies. METHODS: The epidemiological profile of scarlet fever was systematically reviewed using descriptive analysis. We used the Moran's I, local indicators of spatial association, and the retrospective spatiotemporal scanning statistical analysis to study the spatiotemporal aggregation phenomenon of scarlet fever in Guangzhou. RESULTS: From 2005 to 2024, 9,601 scarlet fever cases were reported within Guangzhou, with an annual average morbidity of 3.16 per 100,000. Joinpoint regression analysis indicated a statistically significant overall upward trend in scarlet fever incidence (AAPC = 17.26%, p < 0.001), characterized by four phases: low-incidence phase, upsurge phase, COVID-19-affected phase and post COVID-19 rebound phase. Seasonal distribution exhibited a dual-modal pattern, and the crest of transmission occurred from April to June and November to the following January. Demographically, cases mainly occurred among males and kindergarten children aged 3-6 years. Notably, during the post COVID-19 rebound phase, the proportion of cases among students, particularly those aged 7-10 years, increased substantially, becoming a major affected group nearly comparable to kindergarten children. Spatially, higher incidence was observed within central urban districts and expanding peri-urban growth centers. Spatiotemporal scanning identified ten statistically significant clusters, characterized by an expansion toward expanding peri-urban growth centers, such as Licheng in Zengcheng, alongside a resurgence in traditional central urban areas like Meihuacun in Yuexiu, Baihedong in Liwan and their surrounding regions. CONCLUSIONS: This study reveals a significant spatial-temporal clustering of scarlet fever in Guangzhou from 2005 to 2024, characterized by an overall upward trend and a notable recent resurgence. The high-risk regions were predominantly localized within the central urban regions and expanding peri-urban growth centers, such as Helong, Licheng, Meihuacun, and their surrounding regions. The outbreak mostly affects kindergarten children aged 3-6 years and students aged 7-10 years, with winter and spring as peaks. Control strategies should target high-risk seasons, populations and regions to reduce scarlet fever cases.