Figure 1.

The figure of infective sizes at equilibria versus R ₀ when β = 0.05, ε = 1.2, d = 0.2, μ = 0.2, υ = 0.4, r = 1.5, α = 0.1, and k = 2, where k is big enough to lead a backward bifurcation with two endemic equilibria when R ₀ ^c < R ₀ < 1.