title: HIV transmission by stage of infection and pattern of sexual partnerships.
abstract: BACKGROUND
  Most model analyses examining the role of primary HIV infection in the HIV epidemic ignore the fact that HIV is often transmitted through long-term, concurrent sexual partnerships. We sought to understand how duration and concurrency of sexual partnerships affect the role of transmissions during primary HIV infection.
  
  
  METHODS
  We constructed a stochastic individual-based model of HIV transmission in a homogeneous population where partnerships form and dissolve. Using observed contagiousness by stage of HIV infection, the fraction of transmissions during primary HIV infection at equilibrium was examined across varying partnership durations and concurrencies.
  
  
  RESULTS
  The fraction of transmissions during primary HIV infection has a U-shaped relationship with partnership duration. The fraction drops with increasing partnership duration for partnerships with shorter average duration but rises for partnerships with longer average duration. Partnership concurrency modifies this relationship. The fraction of transmissions during primary HIV infection increases with increasing partnership concurrency for partnerships with shorter average duration, but decreases for partnerships with longer average duration.
  
  
  CONCLUSIONS
  Partnership patterns strongly influence the transmission of HIV and do so differentially by stage of infection. Dynamic partnerships need to be taken into account to make a robust inference on the role of different stages of HIV infection.
authors.affiliation: Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI, USA. kimfinale@gmail.com
authors.forename: Jong-Hoon
authors.initials: JH
authors.lastname: Kim
authors.forename: Rick L
authors.initials: RL
authors.lastname: Riolo
authors.forename: James S
authors.initials: JS
authors.lastname: Koopman
mesh_terms: D018450:Disease Progression; D015658:HIV Infections / Q000453:epidemiology / Q000635:transmission*; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D015233:Models, Statistical; D012307:Risk Factors; D012725:Sexual Behavior; D012747:Sexual Partners; D013997:Time Factors