Climatic drivers of vector-borne diseases: A nationwide causal inference study in China.

OBJECTIVES

Vector-borne diseases (VBDs) impose a significant burden in China, with complex spatiotemporal patterns driven by heterogeneous and nonlinear climatic influences, complicating the identification of causal drivers.

METHODS

To fill this gap, we conducted a nationwide study across 365 city-level regions in mainland China, covering nearly 0.8 million cases of eight types of VBDs, with a time span of 18 years. An empirical dynamic modeling framework was applied to reconstruct system dynamics directly from time-series data, and identify causal climatic drivers for eight VBDs via convergent cross-mapping. Their nonlinear effects and interactions were quantified via scenario exploration across diverse climate zones.

RESULTS

Our results reveal distinct, disease-specific climatic drivers: dengue, Japanese encephalitis, hemorrhagic fever with renal syndrome (HFRS), and leptospirosis are primarily influenced by relative humidity and sunshine-hour; scrub typhus is sensitive to temperature, humidity, and sunshine; severe fever with thrombocytopenia syndrome (SFTS) and tick-borne encephalitis are mainly driven by sunshine-hour. Forecast improvement confirms marked north-south heterogeneity - sunshine alone improves dengue forecasts nationally, but both humidity and sunshine contribute in northern cities, whereas marginal effects diminish in persistently humid southern regions. Scenario exploration further uncovers nonlinear interactions and threshold effects: the positive effect of relative humidity on scrub typhus weakens above 25°C, and sunshine-hour shift from promoting to suppressing SFTS incidence across gradients.

CONCLUSIONS

The climatic driving mechanisms of multiple VBDs in China were disease-specific, regionally heterogeneous, and state-dependent. The forecast-improvement effects of the identified climatic drivers differed between northern and southern regions, and their impacts changed nonlinearly across background climatic states.