Figure 4

Impact of contacts ratio η.Global invasion threshold R _*  as a function of the contacts ratio η, for the case of a mobility air network structure having P(k) ∝ k ^{− γ} with γ = 2 (panel A) and γ = 3 (panel B). Each plot considers three values of the reproductive number – R ₀ = 1.05, 1.2, 1.4. The various curves for the eight European countries under study are shown by means of a shaded area, for the sake of visualization. The distribution of the population into the children class is set to the average European value for all countries, whereas the assortativity level is left country-specific. Maximum assortativity (and thus minimum ε) is reached for Italy, the opposite observed for Belgium. Here we assume that r = 0. The dashed line indicates the threshold condition R _* = 1.