TECHNICAL ARTICLE A simple model for estimating the prevalence of HIV-infected persons

It is not possible to ascertain directly the exact actual value of prevalence of HIV-infected persons without clinical symptoms of AIDS. Therefore a very simple simulation model was developed for the estimation of this value in the early stage of the epidemic. This model is based on the principles of the general method of multicompartmental models and its core is the so-called one-way transport segment which imitates very faithfully the supposed transition of HIV-infected persons through the stage from the transmission of infection to AIDS manifestation. The number of AIDS cases is represented in the model by a compartment. The essence of the estimation procedure is also very simple —it consists in the finding of such shape of the time-dependent parameter of exponential input function of the transport segment for which the course of the compartment measure values agree with the ascertained or prognosti-cated data about the numbers of AIDS cases. The dependence of the exponen-tial function parameter on the product of the average probability that the infection is transmitted from the infected to the receptive individual and of the average rate at which new sexual partners are required can be shown. Key words: HIV-infected persons, multicompartmental models, one-way transport segment, HIV-transmission