Dysentery in Mainland China, 2004–2020: Spatiotemporal Dynamics and the impact of COVID-19 public health interventions

Background Dysentery remains a significant enteric disease globally, causing substantial morbidity and economic burden. Dysentery incidence in China has declined over the past two decades, but the seasonal pattern, spatial clustering, and interprovincial heterogeneity of this decline have not been fully characterised at the national level. The effect of COVID-19 NPIs on dysentery transmission in 2020 also remains unclear. Methods We analysed CISDCP surveillance data from January 2004 to December 2020 across 31 provinces. Joinpoint regression identified long-term trends; time-series decomposition quantified seasonal components; Global Moran's I and LISA assessed spatial autocorrelation and local clusters. Six forecasting models were evaluated per province using a composite standardised index (neural network, ETS, SARIMA, hybrid, BSTS, Prophet). Province-specific models trained on 2004–2019 data generated counterfactual incidence estimates for 2020, which were compared with observed values. Results A total of 3,971,083 cases and 661 deaths were reported. Incidence declined throughout, with an accelerated fall after 2017 (APC: −11.47% for 2004–2017; −18.85% for 2017–2020). Seasonal patterns were stable year to year, though peak amplitude decreased over time. Spatial clustering was significant during 2005–2018 (P < 0.01) but absent in 2020. Beijing and Tianjin had the highest bacillary dysentery incidence; southwest provinces showed a relatively higher amoebic dysentery burden. Infants aged 0–1 years had the largest case share. In 2020, observed national incidence was ~ 18.1% below counterfactual estimates, with wide provincial variation (Guangdong − 34.9%, Chongqing − 35.6%; Qinghai and Hainan showing smaller gaps). Conclusions Dysentery burden in mainland China fell steadily from 2004 to 2020, but seasonality, spatial clustering, and provincial disparities persisted. Infants remained the primary high-risk group. The 2020 decline exceeded pre-pandemic projections by ~ 18%, consistent with collateral benefits from COVID-19 NPIs, though changes in healthcare-seeking behaviour may also contribute. These findings support hotspot-targeted control, priority actions for infants and childcare settings, and province-level early warning.