title: Determinants of per-coital-act HIV-1 infectivity among African HIV-1-serodiscordant couples.
abstract: BACKGROUND
  Knowledge of factors that affect per-act infectivity of human immunodeficiency virus type 1 (HIV-1) is important for designing HIV-1 prevention interventions and for the mathematical modeling of the spread of HIV-1.
  
  
  METHODS
  We analyzed data from a prospective study of African HIV-1-serodiscordant couples. We assessed transmissions for linkage within the study partnership, based on HIV-1 sequencing. The primary exposure measure was the HIV-1-seropositive partners' reports of number of sex acts and condom use with their study partner.
  
  
  RESULTS
  Of 3297 couples experiencing 86 linked HIV-1 transmissions, the unadjusted per-act risks of unprotected male-to-female (MTF) and female-to-male (FTM) transmission were 0.0019 (95% confidence interval [CI], .0010-.0037) and 0.0010 (95% CI, .00060-.0017), respectively. After adjusting for plasma HIV-1 RNA of the HIV-1-infected partner and herpes simplex virus type 2 serostatus and age of the HIV-1-uninfected partner, we calculated the relative risk (RR) for MTF versus FTM transmission to be 1.03 (P = .93). Each log(10) increase in plasma HIV-1 RNA increased the per-act risk of transmission by 2.9-fold (95% CI, 2.2-3.8). Self-reported condom use reduced the per-act risk by 78% (RR = 0.22 [95% CI, .11-.42]).
  
  
  CONCLUSIONS
  Modifiable risk factors for HIV-1 transmission were plasma HIV-1 RNA level and condom use, and, in HIV-1-uninfected partners, herpes simplex virus 2 infection, genital ulcers, Trichomonas vaginalis, vaginitis or cervicitis, and male circumcision.
authors.affiliation: Department of Biostatistics, University of Washington, Seattle 98195-7232, USA. jphughes@u.washington.edu
authors.forename: James P
authors.initials: JP
authors.lastname: Hughes
authors.forename: Jared M
authors.initials: JM
authors.lastname: Baeten
authors.forename: Jairam R
authors.initials: JR
authors.lastname: Lingappa
authors.forename: Amalia S
authors.initials: AS
authors.lastname: Magaret
authors.forename: Anna
authors.initials: A
authors.lastname: Wald
authors.forename: Guy
authors.initials: G
authors.lastname: de Bruyn
authors.forename: James
authors.initials: J
authors.lastname: Kiarie
authors.forename: Mubiana
authors.initials: M
authors.lastname: Inambao
authors.forename: William
authors.initials: W
authors.lastname: Kilembe
authors.forename: Carey
authors.initials: C
authors.lastname: Farquhar
authors.forename: Connie
authors.initials: C
authors.lastname: Celum
mesh_terms: D000328:Adult; D000349:Africa; D017280:Condoms / Q000706:statistics & numerical data; D005191:Family Characteristics; D005260:Female; D005838:Genotype; D015658:HIV Infections / Q000635:transmission* / Q000821:virology*; D015497:HIV-1 / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012367:RNA, Viral / Q000235:genetics; D018570:Risk Assessment; D012725:Sexual Behavior / Q000706:statistics & numerical data*; D019562:Viral Load
chemical_list: D012367:RNA, Viral