title: Sexual transmission of HIV according to viral load and antiretroviral therapy: systematic review and meta-analysis.
abstract: OBJECTIVE
  To synthesize the evidence on the risk of HIV transmission through unprotected sexual intercourse according to viral load and treatment with combination antiretroviral therapy (ART).
  
  
  METHODS
  Systematic review and meta-analysis.
  
  
  METHODS
  We searched Medline, Embase and conference abstracts from 1996-2009. We included longitudinal studies of serodiscordant couples reporting on HIV transmission according to plasma viral load or use of ART and used random-effects Poisson regression models to obtain summary transmission rates [with 95% confidence intervals, (CI)]. If there were no transmission events we estimated an upper 97.5% confidence limit.
  
  
  RESULTS
  We identified 11 cohorts reporting on 5021 heterosexual couples and 461 HIV-transmission events. The rate of transmission overall from ART-treated patients was 0.46 (95% CI 0.19-1.09) per 100 person-years, based on five events. The transmission rate from a seropositive partner with viral load below 400 copies/ml on ART, based on two studies, was zero with an upper 97.5% confidence limit of 1.27 per 100 person-years, and 0.16 (95% CI 0.02-1.13) per 100 person-years if not on ART, based on five studies and one event. There were insufficient data to calculate rates according to the presence or absence of sexually transmitted infections, condom use, or vaginal or anal intercourse.
  
  
  CONCLUSIONS
  Studies of heterosexual discordant couples observed no transmission in patients treated with ART and with viral load below 400 copies/ml, but data were compatible with one transmission per 79 person-years. Further studies are needed to better define the risk of HIV transmission from patients on ART.
authors.affiliation: Institute of Social and Preventive Medicine, University of Bern, Switzerland.
authors.forename: Suzanna
authors.initials: S
authors.lastname: Attia
authors.forename: Matthias
authors.initials: M
authors.lastname: Egger
authors.forename: Monika
authors.initials: M
authors.lastname: Müller
authors.forename: Marcel
authors.initials: M
authors.lastname: Zwahlen
authors.forename: Nicola
authors.initials: N
authors.lastname: Low
mesh_terms: D019380:Anti-HIV Agents / Q000008:administration & dosage*; D023241:Antiretroviral Therapy, Highly Active; D005260:Female; D015658:HIV Infections / Q000188:drug therapy / Q000635:transmission; D006801:Humans; D008297:Male; D012725:Sexual Behavior; D019562:Viral Load
chemical_list: D019380:Anti-HIV Agents