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HIV Transmission Possible Despite Effective Treatment

Risk of HIV transmission between serodiscordant partners increases over time

FRIDAY, July 25 (HealthDay News) -- While individual risk of HIV transmission per sexual encounter is fairly small when one partner is effectively treated and the other is seronegative, the rate of transmission over large numbers of sexual encounters may be substantial, according to research published in the July 26 issue of The Lancet.

David P. Wilson, Ph.D., of the National Centre in HIV Epidemiology and Clinical Research at the University of New South Wales in Sydney, Australia, and colleagues estimated the cumulative risk of HIV transmission between an effectively treated HIV patient and a serodiscordant partner using a simple mathematical model.

Assuming each discordant couple had 100 sexual encounters per year, the cumulative risk of transmission in the non-infected partner is 0.43 percent for male-to-female transmission, 0.22 percent for female-to-male transmission, and 4.3 percent for male-to-male transmission. In a hypothetical population of 10,000 serodiscordant partnerships over 10 years, one would expect 215 female-to-male, 425 male-to-female and 3,524 male-to-male transmissions, the investigators report.

"Our analyses suggest that the risk of HIV transmission in heterosexual partnerships in the presence of effective treatment is low but non-zero and that the transmission risk in male homosexual partnerships is high over repeated exposures," the authors write. "If the claim of non-infectiousness in effectively treated patients was widely accepted, and condom use subsequently declined, then there is the potential for substantial increases in HIV incidence."

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