Figure 1

All the parameters are listed in Table  1 except \(\pmb{\lambda_{i}=1}\), \(\pmb{i=1,2}\). Stability of equilibria of (1.3). The virus-free equilibrium is globally asymptotically stable when \(\mathcal{R}_{0} < 1\) and \(\mathcal{R}_{0}^{\mathrm{cc}}<1\). The graph trajectories of \(y_{j}(t,a)\), \(j=1,2\) versus time t and age a are illustrated in (a) and (b). The graph trajectories of \(Y_{j}(t)\), \(j=1,2\) versus time t are illustrated in (c) and (d).