Fig. 5.

Corresponding population intensities of individuals $S,V,$ and $I$ of system (1.3) with recruitment rate $\Lambda =0.7,0.8,0.9,$ and 1.0, respectively. Other given parameters: $(\beta ,\mu ,\alpha ,\delta ,\gamma ,\vartheta )=(0.4,3\times {10}^{-5},0.00457,0.128,0.2,0.4)$ and $({\sigma }_1,{\sigma }_2,{\sigma }_3)=(0.0008,0.0004,0.0008)$.