We evaluated the association between HIV-1 RNA copies/mL in men and heterosexual transmission to their female partners among 493 couples in Thailand. Husbands were identified as HIV-positive when they were screened as blood donors; nearly all were infected with HIV subtype E. Wives had no known risks for HIV infection other than sex with their husbands. In multivariate analysis, each log10 increment of HIV RNA in the man was associated with an 81% increased rate of HIV transmission to his wife (odds ratio = 1.81, 95% confidence interval: 1.33-2.48). No transmission occurred at viral loads below 1094 copies/mL, and a dose-response effect was seen with increasing viral load in the man. In multivariate analysis, a history of a sexually transmitted disease in the man or woman, longer duration of hormonal contraceptive use, and the woman's onset of sexual activity at less than 20 years of age were also associated with increased seropositivity of the wife.
Address correspondence and reprint requests to Kenrad E. Nelson, Department of Epidemiology, Johns Hopkins University, 615 North Wolfe Street, E7132. Baltimore, MD 21209. U.S.A.; e-mail: firstname.lastname@example.org
Views expressed by the authors do not necessarily reflect those of the United States Agency for International Development or the Contraceptive Research and Development program.
Manuscript received April 16, 2001; accepted October 29, 2001.
© 2002 Lippincott Williams & Wilkins, Inc.