Deterministic prediction of the parameter ranges where epidemic enhancement may be observed.

<p>The range of parameter values (grey) for a population size of <i>N</i> = 50,000 and the initial condition (<i>S₀,I₀</i>) = (<i>N−1, 1</i>) which demonstrate the behavior of an initial epidemic which dies out (there exists <i>t></i>0 such that <i>I_t<</i>1) followed by persistence upon reintroduction (<i>I*></i>1), depending on the level of population turnover between pathogen extinction and reintroduction. <i>R₀</i> is the basic reproductive number of the pathogen in a naïve host population; <i>ρ</i> is the duration of infectiousness relative to the average duration of immunity. Stars represent parameter values taken from the literature for a variety of common and emerging infectious diseases. Note that the x-axis is shown on a log scale. Parameter values used, estimated ranges of parameter values, and references are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000165#pone.0000165.s001" target="_blank">Table S1</a>.