title: A prospective study of sexual transmission of human T lymphotropic virus (HTLV)-I and HTLV-II.
abstract: BACKGROUND
  Cross-sectional studies support sexual transmission of human T lymphotropic virus (HTLV)-I/II; however, prospective incidence data, particularly for HTLV-II, are limited.
  
  
  METHODS
  A cohort of 85 HTLV-positive (30 with HTLV-I and 55 with HTLV-II) blood donors and their stable (>or=6 months) heterosexual sex partners were followed biannually over the course of a 10-year period.
  
  
  RESULTS
  Four of 85 initially seronegative sex partners of HTLV-I and -II carriers seroconverted, for an incidence rate (IR) of 0.6 transmissions/100 person-years (py) (95% confidence interval [CI], 0.2-1.6). This includes 2 HTLV-I transmissions/219 py (IR, 0.9 transmissions/100 py [95% CI, 0.1-3.3]) and 2 HTLV-II transmissions/411 py (IR, 0.5 transmissions/100 py [95% CI, 0.06-1.8]), with no significant difference by HTLV type. There were 2 male-to-female (IR, 1.2 transmissions/100 py [95% CI, 0.1-4.3]) and 2 female-to-male (IR, 0.4 transmissions/100 py [95% CI, 0.05-1.6) transmissions. HTLV-I or -II proviral load was 2 log10 lower in newly infected partners than in index positive partners who transmitted HTLV (P=.007).
  
  
  CONCLUSIONS
  The incidence of sexual transmission of HTLV-II may be similar to that of HTLV-I, and female-to-male transmission may play a more important role than previously thought. HTLV-I and -II proviral load may be lower in sexually acquired infection, because of a small infectious dose.
authors.affiliation: Blood Systems Research Institute, University of California, San Francisco, San Francisco, California 94118, USA.
authors.forename: Diana F
authors.initials: DF
authors.lastname: Roucoux
authors.forename: Baoguang
authors.initials: B
authors.lastname: Wang
authors.forename: Donna
authors.initials: D
authors.lastname: Smith
authors.forename: Catharie C
authors.initials: CC
authors.lastname: Nass
authors.forename: James
authors.initials: J
authors.lastname: Smith
authors.forename: Sheila T
authors.initials: ST
authors.lastname: Hutching
authors.forename: Bruce
authors.initials: B
authors.lastname: Newman
authors.forename: Tzong-Hae
authors.initials: TH
authors.lastname: Lee
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Chafets
authors.forename: Edward L
authors.initials: EL
authors.lastname: Murphy
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D015490:HTLV-I Infections / Q000453:epidemiology / Q000635:transmission*; D015491:HTLV-II Infections / Q000453:epidemiology / Q000635:transmission*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012749:Sexually Transmitted Diseases / Q000453:epidemiology / Q000635:transmission* / Q000821:virology*; D012959:Socioeconomic Factors; D014481:United States / Q000453:epidemiology