Fig. 7.

Plot of the total number of infectives $K\left(t\right)=I\left(t\right)+J\left(t\right)$ for parameters as in (27), (28) and with different choices of the modulation factors μ_i. The initial conditions are chosen according to (29). In the reference run (black curve, solid) all the μ_i are equal to 1; in the other runs the modified factors are as follows: Change of ξ (blue), $r_{\xi }=2.5$; change of β alone (green), $r_{\beta }=7/3$; change of η alone (yellow), $r_{\eta }=7/3$; change of both β and η (red), $r_{\beta }=r_{\eta }=7/3$; change of α (black, dashed), $r_{\alpha }=3/5$. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)