title: The dual impact of antiretroviral therapy and sexual behaviour changes on HIV epidemiologic trends in Uganda: a modelling study.
abstract: OBJECTIVE
  Antiretroviral therapy (ART) availability in a population may influence risky sexual behaviour. We examine the potential impact of ART on the HIV epidemic, incorporating evidence for the impact that ART may have on risky sexual behaviour.
  
  
  METHODS
  A mathematical model, parameterised using site-specific data from Uganda and worldwide literature review, was used to examine the likely impact of ART on HIV epidemiologic trends. We varied assumptions about rates of initiating ART, and changes in sexual partner turnover rates.
  
  
  RESULTS
  Modelling suggests that ART will reduce HIV incidence over 20 years, and increase prevalence. Even in the optimistic scenario of ART enrollment beginning after just five months of infection (in HIV stage 2), prevalence is estimated to rise from a baseline of 10.5% and 8.3% among women and men, respectively, to at least 12.1% and 10.2%, respectively. It will rise further if sexual disinhibition occurs or infectiousness while on ART is slightly higher (2% female to male, rather than 0.5%). The conditions required for ART to reduce prevalence over this period are likely too extreme to be achievable. For example, if ART enrolment begins in HIV stage 1 (within the first 5 months of infection), and if risky sexual behaviour does not increase, then 3 of our 11 top fitting results estimate a potential drop in HIV prevalence by 2025. If sexual risk taking rises, it will have a large additional impact on expected HIV prevalence. Prevalence will rise despite incidence falling, because ART extends life expectancy.
  
  
  CONCLUSIONS
  HIV prevalence will rise. Even small increases in partner turnover rates will lead to an additional substantial increase in HIV prevalence. Policy makers are urged to continue HIV prevention activities, including promoting sex education, and to be prepared for a higher than previously suggested number of HIV infected people in need of treatment.
authors.affiliation: Department of Internal Medicine, University of Manitoba, Winnipeg, Manitoba, Canada Medical Research Council Unit on AIDS/Uganda Virus Research Institute, Entebbe, Uganda.
authors.forename: Leigh Anne
authors.initials: LA
authors.lastname: Shafer
authors.affiliation: Medical Research Council Unit on AIDS/Uganda Virus Research Institute, Entebbe, Uganda.
authors.forename: Rebecca N
authors.initials: RN
authors.lastname: Nsubuga
authors.affiliation: London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Ruth
authors.initials: R
authors.lastname: Chapman
authors.affiliation: London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Katie
authors.initials: K
authors.lastname: O'Brien
authors.affiliation: Medical Research Council Unit on AIDS/Uganda Virus Research Institute, Entebbe, Uganda.
authors.forename: Billy N
authors.initials: BN
authors.lastname: Mayanja
authors.affiliation: London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Richard G
authors.initials: RG
authors.lastname: White
mesh_terms: D000293:Adolescent; D000328:Adult; D023241:Antiretroviral Therapy, Highly Active; D017280:Condoms / Q000706:statistics & numerical data*; D005260:Female; D006679:HIV Seropositivity / Q000188:drug therapy* / Q000453:epidemiology* / Q000523:psychology; D006297:Health Services Accessibility; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D011050:Policy Making; D015995:Prevalence; D012309:Risk-Taking; D012736:Sex Education; D012725:Sexual Behavior / Q000523:psychology / Q000706:statistics & numerical data*; D012747:Sexual Partners / Q000523:psychology; D014454:Uganda / Q000453:epidemiology; D019562:Viral Load
keywords: Africa; Antiretroviral therapy; HIV/AIDS; Uganda; epidemiologic trends; mathematical modeling; sexual behavior