title: Incidence of HIV infection in stable sexual partnerships: a retrospective cohort study of 1802 couples in Mwanza Region, Tanzania.
abstract: OBJECTIVE
  To describe the dynamics of HIV transmission in stable sexual partnerships in rural Tanzania.
  
  
  METHODS
  Retrospective cohort study nested within community-randomized trial to investigate the impact of a sexually transmitted disease treatment program.
  
  
  METHODS
  A cohort of 1802 couples was followed up for 2 years, with the HIV status of each couple assessed at baseline and follow-up.
  
  
  RESULTS
  At baseline, 96.7% of couples were concordant-negative, 0.9% were concordant-positive, 1.2% were discordant with the male partner being HIV-positive, and 1.2% were discordant with the female partner being HIV-positive. Individuals living with an HIV-positive partner were more likely to be HIV-positive at baseline (women: odds ratio [OR] = 75.7, 95% confidence interval [CI]: 33.4-172; men: OR = 62.4, CI: 28.5-137). Seroincidence rates in discordant couples were 10 per 100 person-years (py) and 5 per 100 py for women and men, respectively (rate ratio [RR] = 2.0, CI: 0.28-22.1). In concordant-negative couples, seroincidence rates were 0.17 per 100 py in women and 0.45 per 100 py in men (RR = 0.38, CI: 0.12-1.04). Individuals living in discordant couples were at a greatly increased risk of infection compared with individuals in concordant-negative couples (RR = 57.9, CI: 12.0-244 for women; RR = 11.0, CI: 1.2-47.5 for men).
  
  
  CONCLUSIONS
  Men were more likely than women to introduce HIV infection in concordant-negative partnerships. In discordant couples, incidence in HIV-negative women was twice as high as in men. HIV-negative individuals in discordant partnerships are at high risk of infection, and preventive interventions targeted at such individuals are urgently needed.
authors.affiliation: London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Hugonnet
authors.forename: Frank
authors.initials: F
authors.lastname: Mosha
authors.forename: James
authors.initials: J
authors.lastname: Todd
authors.forename: Kokugonza
authors.initials: K
authors.lastname: Mugeye
authors.forename: Arnoud
authors.initials: A
authors.lastname: Klokke
authors.forename: Leonard
authors.initials: L
authors.lastname: Ndeki
authors.forename: David
authors.initials: D
authors.lastname: Ross
authors.forename: Heiner
authors.initials: H
authors.lastname: Grosskurth
authors.forename: Richard
authors.initials: R
authors.lastname: Hayes
mesh_terms: D000328:Adult; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D015658:HIV Infections / Q000453:epidemiology*; D006679:HIV Seropositivity / Q000453:epidemiology; D006801:Humans; D008297:Male; D016017:Odds Ratio; D012189:Retrospective Studies; D012307:Risk Factors; D012747:Sexual Partners; D013636:Tanzania / Q000453:epidemiology