The epidemic models
When we want to describe how a pathogen or a disease is spread within a population, we need to create a model using mathematical, statistical, or computational tools. The most common model used in epidemiology is the SIR (Susceptible, Infected, and Recovered) model, which was formulated by McKendrick and Kermack in their paper A Contribution to the Mathematical Theory of Epidemics, published in 1927.
In the models presented in this chapter, we assume a closed population (without births or deaths) and that the demographics and socio-economic variables do not affect the spread of the disease.
The SIR model
The SIR epidemiological model describes the course of an infectious disease, as we can see in the following diagram. Starting with a susceptible population (S) that comes into contact with an infected population (I), the individual remains infected, and once the infection period has passed, the individual is then in the recovered state (R).
In this chapter, we will use...
