Figure 3

Final size, extinction probability, and global invasion threshold vs. R ₀ . A-B: Final sizes and extinction probabilities per age class as functions of the reproductive number R ₀. The various curves for the eight European countries under study are shown by means of a shaded area, with the exception of Belgium, see below. The maximum value for the epidemic size in children (and minimum for the epidemic size in adults) is obtained for Italy; the opposite is obtained for Poland. The situation is reversed for the extinction probabilities – the maximum value for the extinction probability in children (and minimum for the extinction probability in adults) is obtained for Poland; the opposite is obtained for Italy. In both plots, Belgium is a standalone example, with z _c > z _a and π _c > π _a , differently from all other countries and due to the fact that it is the only population in the dataset to have η > 1, as discussed in the main text. The dashed line represents the case of homogeneous mixing when no partition of the population is considered (in panel B it corresponds to the function R ₀ ^{− 1}). C: Global invasion threshold R _* as a function of the reproductive number R ₀, for different values of the parameters describing the mobility process. Air mobility networks having degree distributions P(k) ∝ k ^{− γ} with γ = 2 and γ = 3 are shown to consider different levels of heterogeneity. The results obtained in the two cases are compared to the scenarios with homogeneous diffusion rates d _{kk '} = w ₀(kk ^')^θ obtained for θ = 0. All curves are obtained by setting the fraction of passengers in the children class equal to the observed data, i.e. r = 7%, and informing the model with the European average values for α, η, ε.