An SIR model is an epidemiological model that computes the theoretical number of people infected with a contagious illness in a closed population over time. The name
of this class of models derives from the fact that they involve coupled equations
relating the number of susceptible people 
, number of people infected 
, and number of people who have recovered 
. One of the simplest SIR models is the Kermack-McKendrick
model.
The Season 1 episode "Vector" (2005) of the television crime drama NUMB3RS features SIR models.
