Many infectious diseases that spread indirectly via reservoir remain endemic and epidemic in the world, causing thousands of deaths annually in locations that lack adequate sanitation and water infrastructures. However, their dynamics are still not fully understood. In this talk, I will present two models with the Minimum Infection Dose (MID) for an infectious disease: iSIR and iSIBP models. The iSIR model is composed of the bacterial population coupled with a human susceptible-infected-recovered system. On the other hand, the iSIBP model is composed of a bacteria-phage system coupled with a human susceptible-infected system. Global stability and sensitivity analyses of the iSIR model reveal that to control the period and the intensity of disease outbreaks, it is better to focus on the environmental factor (represented by the bacterial carrying capacity) rather than on the sanitation (represented by the shedding rate). Unfortunately, the latter is the current practice in most endemic regions. I will show, using the iSIBP model, that cyclic cholera outbreaks of infectious diseases are generated by the predator-prey cycle that exists between bacteriophage and bacteria in the reservoir. Lastly, I will present easily implementable algorithms that extract the time-dependent transmission rate from either prevalence or incidence data in existing open databases. Over the course of the talk, I will discuss the implications of my findings for current practices in disease prevention/health management bodies.