# Kermack-McKendrick SIR Model

Kermack-McKendrick SIR Model

The Kermack–McKendrick susceptible/infected/removed (SIR) model is one of the simplest possible descriptions of a viral outbreak [1]. After normalizing variables, it depends on only one shape parameter, which determines skew-asymmetry of the distribution of infected individuals across time. Any simpler logistic model of [2] cannot account for asymmetry, unless the differential equation is solved by an error-prone application of Euler's method [3]. This Demonstration shows that erroneous solution of the logistic equation produces a 99.9% accurate, discrete solution of the SIR differential equations over a limited range of the parameter space (see Details). These are called "logistic peaks".