A METHODOLOGICAL STUDY ON FITTING A NONLINEAR STOCHASTIC-MODEL OF THEAIDS EPIDEMIC IN PHILADELPHIA

A nonlinear stochastic model accommodating heterogeneous risk behavior and recruitment was fit to Philadelphia public health data adjusted f or delays in reporting. The methodological study that was performed re sulted in a finding of significant clinical importance. Namely, that t he variable time from infection with HIV to seroconversion may be long er than reported in the literature. The finding challenges our underst anding of the progression of HIV disease and has profound public healt h implications. Although the model and the software incorporated sever al risk categories, such as heterosexual males and females among other s, those examined in this paper are confined to white male homosexual/ bisexual intravenous drug users and white male homosexual/bisexual non intravenous drug users. The results of this paper demonstrate that it is possible to fit a rather complex stochastic model to public health data, using computer intensive methods, and thus, more completely refl ect the diversity of human behavior represented by the defined risk gr oups of the data.