Humidex-related risk of other infectious diarrhea in Anhui, China: a multi-city study on spatial heterogeneity and socioeconomic modifiers

Abstract

Climate change may influence the transmission dynamics of enteric pathogens through changes in temperature, humidity, precipitation, and environmental exposure. Humid heat poses a significant threat, yet its synergistic impact on Other Infectious Diarrhea (OID) remains under-characterized. This study quantifies humid-heat-related OID risks and investigates the socioeconomic determinants driving spatial vulnerability in Anhui, China. Daily data on OID cases ( n  = 822,220) and meteorological variables were collected from 16 cities in Anhui Province (2015–2023). We employed a two-stage strategy: city-specific distributed lag non-linear models (DLNM) to estimate exposure-response associations, followed by multivariate meta-regression to evaluate geographical and socioeconomic effect modifiers. Spatial clustering was quantified using Global Moran’s I statistics. The association between Humidex and OID was non-linear, with significant spatial clustering that intensified over time (Moran’s I : 0.36–0.47, P  < 0.001). Substantial heterogeneity was observed ( I ² = 70.03%), masking marked disparities: less-developed northern cities faced significantly higher risks (e.g., Bengbu, RR = 2.08) and larger disease burdens (e.g., Suzhou, AN = 7,671) than southern counterparts. Multivariate meta-regression identified urbanization rate, GDP per capita, and latitude as the primary drivers of this regional heterogeneity. Humid-heat-related OID risk is structurally modulated by socioeconomic development. Urbanization and economic capacity act as critical buffers, highlighting an “adaptation deficit” in less-developed regions. Public health interventions should prioritize high-risk northern hotspots to mitigate climate-driven health inequities.