“…In [16], the authors proposed a more general incidence rate which has a combination of monotonicity, nonmonotonicity and saturation properties as follows: Usually, there are two types of epidemic models: continuous-time models and discrete-time models. The continuous-time epidemic models described by differential equations have been widely investigated in many articles (for example, [10,11,21,25,30,31] and the references therein). In recent years, there has been an increasing interest in the study of discrete-time models (see [6,8,9,23,24,26,32] and the references therein).…”