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Ratio Of Contracting AIDS During Protected Intercourse



I recall serious various studies about married couples where one was HIV+ and the other was not. They tracked frequency of intercourse, condom usage/breakage, and rate of infection.

Based on such research and other data, what statistically is a typical ratio of contracting the virus during protected intercourse? 1 in 10, 1 in 100, 1 in 500? I sometimes think I overworry.


The Odds of contracting HIV infection between couples is dependent upon a number of issues. First, HIV may be passed via a number of different routes. It can be passed during oral sex (mouth to genital contact), vaginal intercourse or rectal intercourse. The highest risk is rectal intercourse particularly if no lubrication is used and there is injury (bleeding) during sex. Second, if there are other venereal diseases (sexually passed infections) present they can increase the chances of passing HIV between partners. Third, the higher the amount of HIV in the blood of the positive partner, the more likely the risk of passage to the negative partner.

The studies done so far have mostly been done in Africa. The passage rate from a positive partner to a negative partner may vary in Africa and the USA. It also depends upon the factors listed above. On average, the rate of passage of HIV per sex act is 1 in 200. Over the course of one year, about 12-15% of negative partners became positive. Of those who report consistent use of condoms or other barrier methods (bite blocks, saran wrap,etc) the risk is much lower (2 to 5 times lower).

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Response by:

Carl   Fichtenbaum, MD Carl Fichtenbaum, MD
Professor of Clinical Medicine
College of Medicine
University of Cincinnati