ABSTRACT
A basic issue in ecology is the relationship between extinction and population size. One of the clearest manifestations of a population threshold for extinction is the Critical Community Size (CCS) below which infections like measles do not persist in isolated populations. The current generation of stochastic models over-estimates the observed CCS for measles, generating much less persistence of infection than is observed. Including a more biologically realistic model for the duration of infection produced a much closer fit to the CCS and explains previously undescribed high frequency oscillations in measles incidence