Abstract for: HIV Transmissions by Stage under Dynamic Sexual Partnerships

Most models that assess the relative number of transmissions during different stages of human immunodeficiency virus (HIV) infection assume that the transmission occurs through instantaneous sexual contacts. In the real world, however, human sexual interactions occur in the context of a complex social system, and HIV is likely to transmit through repeated sexual acts during partnerships formed and broken over time that last for varying lengths of time. We sought to understand how dynamic sexual partnerships would influence transmission dynamics during different stages of HIV infection: primary HIV infection (PHI) and asymptomatic HIV infection (AHI). Using a pair approximation technique, we developed a dynamic model of HIV transmission in a homogeneous population that includes the formation and dissolution of sexual partnerships of varying duration. The fraction of transmissions during PHI is a U-shaped function of increasing partnership duration, such that the fraction decreases as partnership duration increases up to a few years, but rises again as partnerships are further lengthened. Our results show that the dynamics of sexual partnerships strongly influence HIV transmissions by stage and models that assume instantaneous contacts will likely overestimate transmissions during PHI for real, dynamic sexual partnerships with varying (non-zero) durations.