“…Recently, nonlinear analysis has been widely applied in mathematical modelling in biology [2,3,5,13,21,22,31]. Inspired by previous work for stochastic dynamics in [9,10,12,14,16,19,23,24,[26][27][28]32], this paper discusses a nonlinear SIS epidemic model with stochastic perturbation, which is described by the following stochastic system dS(t) = Λ − µS(t) − βS(t)I(t) 1 + αI(t) + λI(t) dt − σS(t)I(t) 1 + αI(t) dB(t), dI(t) = βS(t)I(t) 1 + αI(t) − (µ + λ)I(t) dt + σS(t)I(t) 1 + αI(t) dB(t), (1.1) where S(t) and I(t), respectively, represent the number of susceptible and infectious individuals at time t, B(t)(B(0) = 0) is the standard Wiener process with intensity σ 2 > 0, Λ stands for the birth rate of susceptible individuals, µ denotes the natural mortality, λ is the recovery rate of disease.…”