This is a model this can be used to predict or track the development of an epidemic. .
It can often be referred to as the SIR model. Susceptible, Infected, Recovery. .
A pop…ulation is susceptible to a disease, it can then become infected once it catches the disease and then recovers. It may be there is a positive feedback into the susceptible category if the recovered people cannot develop immunity. .
Various external factors control the risk of the susceptible populous e.g. exposure, health diet etc. The Infected rate depends upon exposure, type of disease, ease of infection etc. The recovery depends upon the disease. In the most extreme cases of death the populous for mathematical purposes is removed from the recovery category. .
If you know your population e.g a school. Then you can enter hypothetical illnesses such as mumps into the model to see how quickly the disease would spread in the school. This can allow you to develop strategies to reduce infection and promote recovery e.g. isolation or washing hands. ( Full Answer )