Epidemiological characteristics of scarlet fever in Liaoning Province, China: a pre- and postpandemic comparison, 2005-2024.

ObjectivesThis study aimed to investigate scarlet fever epidemiology in Liaoning Province, China (2005-2024), and assess COVID-19 pandemic impacts.MethodsIndividual-level data on scarlet fever cases from the National Notifiable Infectious Disease Reporting System (NNIDRS) were analyzed for temporal, demographic and spatiotemporal features across pre-, peri‑ and postpandemic stages.ResultsA total of 73,102 scarlet fever cases were reported. Incidence remained stable during the prepandemic period, from 2005 (8.9 per 100,000 population per year) to 2019 (10.8), sharply declined during the pandemic period (2020-2022; range: 1.4-0.6), and rebounded markedly postpandemic (2023: 1.9; 2024: 7.7). Most cases (79.4%) occurred in children under 15 years of age from urban areas. During 2005-2019, incidence significantly increased among children aged 3-6 years (AAPC: 7.4%; 95% CI: 3.0-11.9%) and in rural populations (AAPC: 4.3%; 95% CI: 1.1-7.6%). Compared with the prepandemic period (2005-2019), the proportion of cases among children aged 7-14 years significantly increased during the postpandemic period (2023-2024) (31.4% vs 54.1%, P < 0.01).ConclusionScarlet fever incidence in Liaoning Province showed a resurgence after the pandemic, with an age distribution shifting toward older children. These evolving epidemiological patterns highlight the need for enhanced, age-targeted surveillance and adaptive prevention strategies.