Cholera is an acute intestinal illness caused by infection with the bacterium Vibrio cholerae. The dynamics of the disease transmission are governed by human-human, environment-human, and within-human sub-dynamics. A multi-scale model is presented to incorporate all three of these dynamical components. The model is divided into three subsystems where the dynamics are analyzed according to their respective time scales. For each subsystem, we conduct a careful equilibrium analysis, with a focus on the disease threshold characterized by the basic reproduction number. Finally, the three subsystems are combined to discuss the dynamical properties of the full system.