Mathematical modeling is an important tools to analyze and control the spread of infection disease in a society. One of the fundamental questions of mathematical epidemiology is to find threshold conditions that determine whether an infectious disease will spread in a susceptible population when the disease is introduced into the population. The threshold conditions are characterized by the so-called reproductive number, the reproduction number, the reproductive ratio, basic reproductive value, basic reproductive rate, or contact number. This book present the deterministic and stochastic epidemic models for HIV and study of reproductive numbers. The homotopy perturbation method and homotopy analysis method which was used to solve the linear and nonlinear differential equations. Also, the generation of stochastic models in the epidemic disease has been studied.