Figure 2

Numerical simulation of the solution of system ( 1.2 ) and its corresponding deterministic system ( 1.1 ) with initial value \(\pmb{S(0)=30}\) , \(\pmb{I(0)=10}\) , \(\pmb{P(0)=15}\) : (a) is with \(\pmb{\alpha=0.004}\) , \(\pmb{\lambda=0.015}\) ; (b) with \(\pmb{\alpha =0.004}\) , \(\pmb{\lambda=0.015}\) , \(\pmb{\sigma=0.002}\) ; (c) with \(\pmb{\alpha=0.004}\) , \(\pmb{\lambda =0.015}\) , \(\pmb{\sigma=0.004}\) ; (d) with \(\pmb{\alpha=0.004}\) , \(\pmb{\lambda=0.015}\) , \(\pmb{\sigma=0.006}\) .