Comparison of different models in Figure 1A.

<p>(A) Model based on all contacts with relative susceptibility of over-18s, <i>α</i>, equal to one. (B) Model based on close contacts with <i>α</i> = 1. (C) Model based on all contacts with variable <i>α</i>. (D) Model based on close contacts with variable <i>α</i>. Colour shows model support under the Akaike Information Criterion (AIC). Note that models with numerous contact classes in B and D had some classes consisting solely of individuals – some of whom had been infected – that had no reported close contacts. The likelihood of such people seeing infection given the model assumptions was zero; the difference in AIC was therefore infinite.