title: Rates of HIV-1 transmission per coital act, by stage of HIV-1 infection, in Rakai, Uganda.
abstract: BACKGROUND
  We estimated rates of human immunodeficiency virus (HIV)-1 transmission per coital act in HIV-discordant couples by stage of infection in the index partner.
  
  
  METHODS
  We retrospectively identified 235 monogamous, HIV-discordant couples in a Ugandan population-based cohort. HIV transmission within pairs was confirmed by sequence analysis. Rates of transmission per coital act were estimated by the index partner's stage of infection (recent seroconversion or prevalent or late-stage infection). The adjusted rate ratio of transmission per coital act was estimated by multivariate Poisson regression.
  
  
  RESULTS
  The average rate of HIV transmission was 0.0082/coital act (95% confidence interval [CI], 0.0039-0.0150) within approximately 2.5 months after seroconversion of the index partner; 0.0015/coital act within 6-15 months after seroconversion of the index partner (95% CI, 0.0002-0.0055); 0.0007/coital act (95% CI, 0.0005-0.0010) among HIV-prevalent index partners; and 0.0028/coital act (95% CI, 0.0015-0.0041) 6-25 months before the death of the index partner. In adjusted models, early- and late-stage infection, higher HIV load, genital ulcer disease, and younger age of the index partner were significantly associated with higher rates of transmission.
  
  
  CONCLUSIONS
  The rate of HIV transmission per coital act was highest during early-stage infection. This has implications for HIV prevention and for projecting the effects of antiretroviral treatment on HIV transmission.
authors.affiliation: Heilbrun Department of Population and Family Health, Columbia University Mailman School of Public Health, New York, New York 10032, USA. mwawer@jhsph.edu
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Wawer
authors.forename: Ronald H
authors.initials: RH
authors.lastname: Gray
authors.forename: Nelson K
authors.initials: NK
authors.lastname: Sewankambo
authors.forename: David
authors.initials: D
authors.lastname: Serwadda
authors.forename: Xianbin
authors.initials: X
authors.lastname: Li
authors.forename: Oliver
authors.initials: O
authors.lastname: Laeyendecker
authors.forename: Noah
authors.initials: N
authors.lastname: Kiwanuka
authors.forename: Godfrey
authors.initials: G
authors.lastname: Kigozi
authors.forename: Mohammed
authors.initials: M
authors.lastname: Kiddugavu
authors.forename: Thomas
authors.initials: T
authors.lastname: Lutalo
authors.forename: Fred
authors.initials: F
authors.lastname: Nalugoda
authors.forename: Fred
authors.initials: F
authors.lastname: Wabwire-Mangen
authors.forename: Mary P
authors.initials: MP
authors.lastname: Meehan
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Quinn
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000453:epidemiology* / Q000473:pathology / Q000635:transmission*; D000293:Adolescent; D000328:Adult; D003075:Coitus; D005260:Female; D015497:HIV-1 / Q000302:isolation & purification*; D006801:Humans; D015994:Incidence; D008297:Male; D016012:Poisson Distribution; D012749:Sexually Transmitted Diseases / Q000635:transmission* / Q000821:virology; D013997:Time Factors; D014454:Uganda / Q000453:epidemiology; D019562:Viral Load