“…Since epidemic models were first introduced by Kermack and McKendrick in [15,16], the study on mathematical models has been flourished. Much attention has been devoted to analyzing, predicting the spread, and designing controls of infectious diseases in host populations; see [1,2,4,6,8,18,19,15,16,26,27] and the references therein. One of classic epidemic models is the SIR (Susceptible-Infected-Removed) model that is suitable for modeling some diseases with permanent immunity such as rubella, whooping cough, measles, smallpox, etc.…”