The Non-Linear Transmission Dynamics of HIV/AIDS

Abstract

How infectious a person is when infected with HIV depends upon what stage of the disease the person is in. We use three stages which we call primary, asymptomatic and symptomatic. It is important to have a systematic method for computing all three infectivities so that the measurements are comparable. Using robust modeling we provide high-resolution estimates of semen infectivity by HIV disease stage. We find that the infectivity of the symptomatic stage is far higher, hence more potent, than the values that prior studies have used when modeling HIV transmission dynamics. The stage infectivity rates for semen are 0.024, 0.002, 0.299 for primary, asymptomatic and symptomatic (late-stage) respectively. Implications of our infectivity estimates and modeling for understanding heterosexual epidemics such as the Sub-Saharan African one are explored.

Most models are compartment models that are based on the number of new infections per unit time. We create a new risk-based model that focuses on a susceptible person's risk of becoming infected if he has a single contact with an infected individual.