Time series of a simulated epidemic in a population in which transmission between adults (black) and children (gray) is 1% of intra-group transmission (β_AC = 0.01 * β_AA; β_CA = 0.01 * β_CC; left), or 10% (β_AC = 0.1 * β_AA; β_CA = 0.1 * β_CC; middle), or 100% (β_AC = β_AA; β_CA = β_CC; right), in the absence of intervention.

<p>Broken line: susceptible; solid line: infected. In the right panel, the black and gray broken lines overlap each other exactly. R_0A = 1.25; R_0C = 2. 50% adults; 50% children. All other parameters and initial conditions are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036573#pone-0036573-t001" target="_blank">Tables 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036573#pone-0036573-t002" target="_blank">2</a>. The reason why in the right panel, the curves of susceptible adults and children overlapped, while the curves of infected adults and children did not, was that adults and children had different rates of recovery and therefore their average durations in the model compartment of the infected/infectious were different.