Fig. 3.

The figure shows the basic reproduction number ${\mathcal{R}}_0$ when $\left(i\right)$$\eta$ and $\rho$ varies, $\left(\mathit{ii}\right)$$\eta$ and $\mu$ varies, $\left(\mathit{iii}\right)$$\mu$ and $\rho$ varies. Contour plots of basic reproduction number ${\mathcal{R}}_0$ with respect to $\left(\mathit{iv}\right)$$\eta$ and $\rho$, ($v)$$\eta$ and $\mu$, $\left(\mathit{vi}\right)$$\mu$ and $\rho$.