Epidemiological Characteristics of Hepatitis E in Eastern China, 2015–2024: A Spatiotemporal Multicomponent Modeling Analysis

Background: In recent years, the incidence of enteric infectious diseases in China has declined significantly. However, hepatitis E incidence remains relatively high in eastern coastal provinces. This study aimed to characterize the epidemiological features of hepatitis E in Zhejiang Province; to decompose county-level incidence into endemic, autoregressive, and spatiotemporal components; and to assess the heterogeneity across counties. Methods: Hepatitis E case data, population data, socioeconomic data, and meteorological data were obtained. Seasonality was described using the seasonal index, the concentration method and a harmonic Poisson regression. A spatiotemporal multicomponent model was fitted to monthly county-level case counts to decompose incidence into endemic, autoregressive and spatiotemporal components. Results: Over the study period, hepatitis E incidence in Zhejiang Province showed an upward trend. Seasonality was weak (concentration index M = 0.10; sin term: p < 0.001; amplitude A = 0.21, 95% CI: 0.16–0.27), with a minor peak in early-to-mid April. Incidence was relatively higher in the northwestern region. The estimated parameters for the autoregressive, spatiotemporal, and endemic components were 0.366, 0.037, and 45.325, respectively, with substantial heterogeneity across counties. The endemic component accounted for the largest mean county-specific proportion. The autoregressive component accounted for the largest proportion in high-incidence areas, whereas the endemic component dominated in low-incidence areas. The relative risk for per capita Gross Domestic Product and daily total precipitation was 1.018 (95% CI: 1.010–1.025) and 0.976 (95% CI: 0.960–0.992), respectively. Conclusions: The components accounting for the largest proportion of hepatitis E incidence in Zhejiang Province differed between high- and low-incidence areas, underscoring the need for tailored prevention strategies based on local epidemiological patterns.