On the extended simple stochastic epidemic model

Abstract

McNeil (1972) suggests a normal approximation to the distribution of the number of infectives in large populations for two distinct epidemic models. In this note, we extend the work of McNeil to the extended simple stochastic epidemic model proposed by Severo (1969). We also compare the resulting approximations to the mean and variance of the number of infectives with the corresponding exact results for populations of size 10.