Model with a single group (left) and q = 1.7 corresponding to a basic reproduction ratio of 1.37, and two groups (right) with q₁ = 2.35, q₂ = 0.117, and p = 0.02 as in Figure 3, with same basic reproduction ratio. Note that the figure on the left is the same as in Figure 1 (right), on a different scale. The straight dotted line is the level p. In the case with two groups, note that almost all individuals of the second group get infected during the propagation of the disease.