ABSTRACT
Consider a large community that is currently free from a certain infectious disease, for which the effective reproduction number R is greater than 1. Figure 2.6 illustrates that importation of the infection has two distinct types of outcome when R > 1. Either a minor outbreak occurs or an epidemic. Which of these outcomes occurs is subject to chance. Specifically, it depends on whether the number of infectives builds up adequately during the early stage of the outbreak for transmission “to take off.”
