Temporal trends in reported vector-borne diseases in China before and after the onset of COVID-19 from 2004 to 2023

Background Vector-borne diseases (VBDs) continue to pose a public health burden in China. However, changes in the reported incidence and mortality of VBDs during the COVID-19 period remain insufficiently characterized. Methods We analyzed five major VBDs—typhus, dengue, leishmaniasis, malaria, and epidemic encephalitis B (EEB)—in China from 2004 to 2023. Province- and age-specific surveillance data for 2004–2020 were obtained from the Chinese Center for Disease Control and Prevention, whereas national aggregate data for 2021–2023 were obtained from the National Health Commission. Accordingly, spatial and age-specific analyses were restricted to 2004–2020, while national trend analyses were extended through 2023. Annual trends were evaluated using Joinpoint regression, monthly seasonal patterns were assessed using STL decomposition, monthly changes after January 2020 were evaluated using interrupted time-series analysis, and expected monthly trajectories for 2020–2023 were estimated using SARIMA models trained on pre-COVID data. Results From 2004 to 2020, incidence and mortality of VBDs declined significantly, especially for malaria, dengue, and EEB, and spatial hotspots were concentrated mainly in southern provinces. Compared with 2013–2019, overall incidence and mortality during 2020–2023 were 59.86% lower (95% CI: –60.36 to –59.36; P < 0.001) and 83.72% lower (95% CI: –87.86 to –78.18; P < 0.001), respectively. Malaria and EEB showed the largest reductions, whereas typhus and leishmaniasis changed less markedly. However, these declines should be interpreted cautiously because they may reflect a combination of COVID-19-era public health measures, pre-existing long-term trends, disease-specific control programs, and possible surveillance disruption. Conclusions During the COVID-19 period in China, reported VBD incidence and mortality decreased substantially. However, it would be overly simplistic to attribute these changes entirely to COVID-19-related interventions, as other factors were also likely involved. These findings highlight the need for reliable surveillance and reporting during public health emergencies, together with forecasting tools that can be adapted to changing conditions, to support future vector-borne disease control.