We consider a standard Susceptible-Infected-Removed (SIR) model [10, 12] with no loss of immunity but with mortality. In this model, the dynamic variables at time t are the number of susceptible individuals, S(t); the number of infected individuals, I(t); the number of recovered individuals, R(t); and the number of removed/dead individuals, D(t). We assume that the population is closed to immigration such that S(t)+I(t)+R(t)+D(t) = N is constant, and any three of the dynamic variables define the fourth.