Modeling the impact of WASH funding on cholera dynamics: an integrated modeling approach

Cholera remains a persistent public health challenge in many low- and middle-income countries, driven by inadequate access to safe water, sanitation, and hygiene (WASH), and further exacerbated by unstable financing of control programmes. While WASH interventions are widely recognized as essential for sustainable cholera prevention, their epidemiological impact depends critically on the timing, intensity, and continuity of funding. In this study, we develop and analyse a deterministic compartmental model that explicitly couples cholera transmission dynamics with WASH funding processes. The model accounts for both direct person-to-person transmission and indirect waterborne transmission via an environmental bacterial reservoir, while linking funding inflows to WASH effectiveness through a saturating scale-up function that captures diminishing returns and infrastructure decay. Funding is modeled as responsive to reported case burden, with attrition incorporated to reflect the gradual decline of financial support over time. Analytical results establish the well-posedness of the system, derive a closed-form cholera–WASH–funding reproduction number, and identify parameter regimes under which backward bifurcation may occur, indicating that reducing transmission intensity alone may be insufficient for elimination. Numerical simulations reveal a clear separation of control mechanisms across time scales: early outbreak dynamics are dominated by transmission intensity, particularly through environmental pathways, whereas long-term epidemic behavior is governed by sustained funding and the durability of WASH effectiveness. The model suggests that, under the structural assumptions of the framework, reactive short-term funding surges may be insufficient for durable control in the parameter regimes examined. In contrast, sustained investment that maintains baseline WASH capacity above a critical threshold can prevent recurrent outbreaks. Overall, this study highlights the importance of explicitly incorporating financial sustainability into cholera models and provides a flexible framework for assessing long-term WASH financing strategies in support of global cholera elimination efforts.