Local: Kermack and McKendrick’s “Contributions to the Mathematical Theory of Epidemics"

This sequence of papers, published in the late 1920’s, are credited with introducing the dominant epidemic modelling paradigm, now known as “compartmental models”. These have been widely used by many groups to make predictions for the current pandemic. I will summarise the model that is introduced in this work, before focussing on the special case of the famous SIR (susceptible-infected-recovered) model. This model defies an exact solution, but it is possible to determine quantities like the outbreak size analytically, gain some understanding of the much-discussed R number, and also find the time-dependent solution in an approximation when the outbreak is small relative to the population size.