A prospective study of sexual transmission of human T lymphotropic virus (HTLV)-I and HTLV-II.
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.
Roucoux
Diana F
DF
Blood Systems Research Institute, University of California, San Francisco, San Francisco, California 94118, USA.
Wang
Baoguang
B
Smith
Donna
D
Nass
Catharie C
CC
Smith
James
J
Hutching
Sheila T
ST
Newman
Bruce
B
Lee
Tzong-Hae
TH
Chafets
Daniel M
DM
Murphy
Edward L
EL
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