title: Viral load and heterosexual transmission of human immunodeficiency virus type 1. Rakai Project Study Group.
abstract: METHODS
  We examined the influence of viral load in relation to other risk factors for the heterosexual transmission of human immunodeficiency virus type 1 (HIV-1). In a community-based study of 15,127 persons in a rural district of Uganda, we identified 415 couples in which one partner was HIV-1-positive and one was initially HIV-1-negative and followed them prospectively for up to 30 months. The incidence of HIV-1 infection per 100 person-years among the initially seronegative partners was examined in relation to behavioral and biologic variables.
  
  
  RESULTS
  The male partner was HIV-1-positive in 228 couples, and the female partner was HIV-1-positive in 187 couples. Ninety of the 415 initially HIV-1-negative partners seroconverted (incidence, 11.8 per 100 person-years). The rate of male-to-female transmission was not significantly different from the rate of female-to-male transmission (12.0 per 100 person-years vs. 11.6 per 100 person-years). The incidence of seroconversion was highest among the partners who were 15 to 19 years of age (15.3 per 100 person-years). The incidence was 16.7 per 100 person-years among 137 uncircumcised male partners, whereas there were no seroconversions among the 50 circumcised male partners (P<0.001). The mean serum HIV-1 RNA level was significantly higher among HIV-1-positive subjects whose partners seroconverted than among those whose partners did not seroconvert (90,254 copies per milliliter vs. 38,029 copies per milliliter, P=0.01). There were no instances of transmission among the 51 subjects with serum HIV-1 RNA levels of less than 1500 copies per milliliter; there was a significant dose-response relation of increased transmission with increasing viral load. In multivariate analyses of log-transformed HIV-1 RNA levels, each log increment in the viral load was associated with a rate ratio of 2.45 for seroconversion (95 percent confidence interval, 1.85 to 3.26).
  
  
  CONCLUSIONS
  The viral load is the chief predictor of the risk of heterosexual transmission of HIV-1, and transmission is rare among persons with levels of less than 1500 copies of HIV-1 RNA per milliliter.
authors.affiliation: National Institute of Allergy and Infectious Diseases, Bethesda, MD, USA.
authors.forename: T C
authors.initials: TC
authors.lastname: Quinn
authors.forename: M J
authors.initials: MJ
authors.lastname: Wawer
authors.forename: N
authors.initials: N
authors.lastname: Sewankambo
authors.forename: D
authors.initials: D
authors.lastname: Serwadda
authors.forename: C
authors.initials: C
authors.lastname: Li
authors.forename: F
authors.initials: F
authors.lastname: Wabwire-Mangen
authors.forename: M O
authors.initials: MO
authors.lastname: Meehan
authors.forename: T
authors.initials: T
authors.lastname: Lutalo
authors.forename: R H
authors.initials: RH
authors.lastname: Gray
mesh_terms: D000293:Adolescent; D000328:Adult; D002944:Circumcision, Male; D018562:Disease Transmission, Infectious; D004522:Educational Status; D005260:Female; D015658:HIV Infections / Q000635:transmission* / Q000821:virology; D006679:HIV Seropositivity; D015497:HIV-1 / Q000276:immunology / Q000302:isolation & purification; D020010:Heterosexuality; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012367:RNA, Viral / Q000097:blood*; D012307:Risk Factors; D014195:Travel; D019562:Viral Load
chemical_list: D012367:RNA, Viral