Figure 1.

The relationship between the population attributable fraction (PAF) calculated by simulating epidemics and the basic reproduction number. A risk factor that affects a proportion $p=0.1$ of the population with relative risk of susceptibility of $r=10$ has a traditional PAF estimate of $PA{F}_{trad}=0.47$. Methods for estimating PAF by simulating cumulative incidence with and without a risk factor (PAF${}_c$) result in estimates ranging from $PA{F}_{trad}\le PA{F}_c\le 1$, depending on the basic reproduction number in the general population (the non-risk group). The thick lines illustrate $PA{F}_c$ values when $PA{F}_{trad}=0.47$ for sample reproduction numbers. The thin lines are the asymptotes, given by PAF${}_i$.