Human immunodeficiency virus (HIV) is a lenti-virus (a member of the retrovirus family) that causes acquired immunodeficiency syndrome (AIDS), a critical condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections. Over the past few years HIV has been spreading rapidly in the population. Almost, everyday there are thousands of new human cases of HIV infection being recorded in the world and these occur in almost every country of the world. However, the spread of HIV is relatively faster in the developing countries as compared to developed countries because developing countries have limited resources. Worldwide, 70% of HIV infections in the adults have been transmitted through heterosexual contact and vertical transmission accounts for more than 90% of global infection in infants and children. In this paper, we propose a nonlinear mathematical model to study the spread of HIV by considering transmission of disease by heterosexual contact and vertical transmission. A stage structured model is proposed and analyzed by considering the total population variable and dividing the whole population under consideration into three stages: children, adults and old. Also, in this paper it is assumed that the rates of recruitment are different in different groups of population. Equilibria of the model and their stability are also discussed. Using the stability theory of differential equations and computer simulation, it is shown that due to the increase in the awareness of the disease in the adult class the total infective population decreases in the region under consideration.