The first mathematical epidemiological model was formulated in 1760 by Daniel
Bernoulli (Choisy, Guégan et al. 2006) with the aim of evaluating the impact of
variation of human life expectancy. In the early 1920s, Kermack and McKendrick
made crucial suggestions concerning a compartment model to study the spread of
infectious diseases. Their suggestions formed the foundations of mathematical
epidemic modelling. The epidemic of any population at any time consists of different
proportions (compartments) of susceptible, infective and recovered individuals
(Kermack and McKendrick 1927). This model is discussed in more detail in section