Risk Of HIV Transmission From Heterosexual Intercourse Could Be Underestimated, Study Finds

Main Category: HIV / AIDS
Article Date: 07 Aug 2008 - 7:00 PDT

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The standard method for assessing risk of HIV transmission through heterosexual intercourse could be flawed, according to a study published in the Lancet Infectious Diseases and presented at the XVII International AIDS Conference on Tuesday, AFP/iAfrica.com reports.

According to the study, a "yardstick" widely used by epidemiologists to determine HIV risk could have helped "fuel misperceptions" that HIV risk is lower for heterosexuals, AFP/iAfrica.com reports. The yardstick suggests that transmission of HIV occurs on average once per 1,000 acts of heterosexual intercourse by couples where only one individual is HIV-positive. However, the study said that the measurement is based on "stable couples" with few risk factors and that in other scenarios, risk factors can increase the chance of transmission by between several times and several hundred times, AFP/iAfrica.com reports.

The study, led by Kimberly Powers of the University of North Carolina, conducted a systematic review of estimated of heterosexual infectivity and found a wide range of results, ranging from zero transmission of HIV after more than 100 acts of heterosexual vaginal intercourse in one study to a rate of HIV transmission of once out of every 3.1 acts of heterosexual anal intercourse.

The study said HIV risks could be amplified by other factors, such as men who are not circumcised, partners who have genital ulcers or if a partner is at the early or late stage of HIV, when viral loads are higher. In addition, researchers do not know the risks of HIV transmission for certain sexual behaviors, including oral sex.

According to the researchers, "The use of a single, 'one-size-fits-all' value for the heterosexual infectivity of HIV-1 obscures important differences associated with transmission co-factors." They added that the measurement of one infection per 1,000 acts of intercourse "seems to represent a lower bound. As such, this value substantially underestimates the infectivity of HIV-1 in many heterosexual contexts" (AFP/iAfrica.com, 8/5).

The study is available online.

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