Environmental Persistence and Threshold Dynamics in a Multi-Region Cholera Model

Cholera remains a major global health concern, particularly in regions with limited sanitation and high population mobility. Motivated by the 2010 Haiti earthquake and subsequent outbreak, this study examines the roles of environmental reservoirs, and spatial coupling in cholera transmission, using a coupled SEIR-B and hydrodynamic modeling framework. Human disease dynamics are integrated with environmental bacterial transport via advection and diffusion, together with cross-regional coupling mechanisms. Analysis of the basic reproduction number R0, stability properties, and numerical simulations identifies thresholds separating bacterial elimination from persistence and demonstrates how hydrological transport, exogenous contamination, and upstream sources shape downstream risk. Numerical results further show even localized external contamination can sustain downstream bacterial persistence despite local control of human infections. These results underscore the need for coordinated sanitation and water-management interventions in hydrologically connected regions. They also highlight the importance of region-level coordination when designing effective cholera control strategies.