Changes in Dengue Epidemiology in China Before, During, and After COVID‐19 2015–2024: A Retrospective National Surveillance and Spatiotemporal Study

BACKGROUND: Dengue remains a major mosquito-borne disease in China. The COVID-19 pandemic and associated non-pharmaceutical interventions (NPIs) profoundly altered human mobility and public health responses, potentially reshaping dengue transmission dynamics. However, comprehensive nationwide evidence on their long-term epidemiological impact is limited. OBJECTIVE: This study aimed to evaluate changes in dengue epidemiology in China before, during, and after the COVID-19 pandemic, with a focus on temporal periodicity, importation and indigenous transmission, counterfactual deviations from pre-pandemic trends, and spatial risk redistribution. METHODS: We conducted a nationwide retrospective spatiotemporal study using reported dengue cases in China from 2015 to 2024. Epidemiological characteristics were compared across pre-pandemic, pandemic, and post-pandemic phases. Morlet wavelet analysis was used to assess temporal periodicity. A SARIMA model fitted to pre-pandemic data generated counterfactual forecasts for 2020-2024. Spatial patterns were evaluated using provincial incidence mapping, Global Moran's I, and Local Indicators of Spatial Association. RESULTS: A total of 87 182 dengue cases were reported, with major peaks in 2019 and 2024. Imported cases declined sharply during 2020-2022 and rebounded after 2023, whereas indigenous transmission became increasingly dominant. Annual periodicity weakened during the pandemic but re-emerged after 2023. Observed incidence during 2020-2022 was frequently below counterfactual expectations, while substantial positive deviations appeared from mid-2023 and intensified in 2024. Post-pandemic dengue risk re-emerged in South and Southwest China and expanded inland, with weaker provincial clustering. CONCLUSIONS: COVID-19 and related NPIs substantially reshaped dengue epidemiology in China, suppressing transmission during 2020-2022 but followed by a marked post-pandemic resurgence, increasing indigenous transmission, disrupted but re-emerging seasonality, and broader inland spread.