We formulate and analyze an unconditionally stable nonstandard finite difference method for a mathematical model of HIV transmission dynamics. The dynamics of this model are studied using the qualitative theory of dynamical systems. These qualitative features of the continuous model are preserved by the numerical method that we propose in this paper. This method also preserves the positivity of the solution, which is one of the essential requirements when modeling epidemic diseases. Robust numerical results confirming theoretical investigations are provided. Comparisons are also made with the other conventional approaches that are routinely used for such problems.

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We develop and analyze a mathematical model for the transmission dynamics of HIV that accounts for behavioral change. The contact rate is modeled by a decreasing function (response function) of HIV prevalence to reflect a reduction in risky behavior that results from the awareness of individuals to a higher HIV prevalence. The model also includes a distributed delay representing the time needed for individuals to reduce their risky behavior. We study mathematically and numerically the impact of the response function and the distributed delay on the model's dynamics. Threshold values for the delay at which the system destabilizes and periodic solutions can arise through Hopf bifurcation are determined.

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