Figure 3: Probability of extinction given an introduction of single child or adult index case. The probabilities of extinction are calculated, assuming that a single child or adult index case is introduced into a fully susceptible large population. The probability approximately accounts for heterogeneous transmission among and between child and adult populations. The estimates of the next-generation matrices are extracted from A. Fraser et al. [6] based on an analysis in Mexico and B. Nishiura et al. [2] in Japan. The basic reproduction numbers in the original studies in Mexico and Japan are estimated at and 1.22, respectively, and both panels rescales the next-generation matrix by multiplying each entry with where measures the horizontal axis.