On the role of variable incubation periods in simple epidemic models

The paper formulates a simple stochastic model which can be used to describe the early spread of an epidemic in a large population. Comparison of the behaviour of the epidemic under different assumptions for the distribution of the incubation period are made using the concept of partial ordering between random variables. It is shown that the process describing the infectious contacts between individuals has a major effect on the comparison of the different models. These results have important implications for modelling the AIDS epidemic.