Figure 3

The mean of the (stochastic) I-paths over 8000 runs, compared with the deterministic I-path [\(\sigma =0.0002\), \(\zeta =0.05\)]. The graph illustrates the stability theorem, Theorem 4.3: Although \(R_{0}= 1.0202 > 1\) means that the deterministic model yields the instability of the disease-free equilibrium and stochastic perturbations cause the convergence (almost surely) to disease-free equilibrium