Figure 11.

Diagram displaying the disease-free state by fixing the parameter values Ye SPF wt/A0 from Table 3 in Model (14). As long as ${\alpha }^{\left(B\right)}$ is large enough, the disease-free state persists. However, by reducing ${\alpha }^{\left(B\right)}$, the basic reproduction number ${\mathcal{R}}_0^{wt}$ reaches its threshold value (${\mathcal{R}}_0^{wt}=1$). This causes changes in the dynamic behavior of the model (14), as shown in Figure 4.