A study of homosexual men living in San Francisco who were recently infected with HIV-1 suggests that in about 7%of cases the virus was likely to have been transmitted during oral sex.
Dr Frederick Hecht of the University of California, San Francisco, and colleagues there and at the Centers for Disease Control and Prevention (CDC) in Atlanta evaluated 122 people recently diagnosed with HIV-1 infection who were presumed to have acquired their infection between June 1996 and June 1999. They tried to determine how the men contracted the disease.
The researchers used a new HIV testing method that makes it possible to determine if an individual has been recently infected. The subjects were interviewed in unusual depth and, whenever possible, excluded from the “oral sex” category.
Of all the cases, researchers determined that 20 were potentially acquired through oral sex. On further evaluation, and elimination of cases in which HIV-1 transmission may have occurred through another means, the researchers classified eight cases (7%) as probably due to oral transmission.
All eight cases were men who reported that they thought oral sex carried no risk or only minimal risk of transmission. “I think this is the best data available to date,” said Dr Robert Janssen, director of the division of HIV/AIDS prevention at the CDC. He added: “I think it reinforces what we've said already—which is that condoms should be used for whatever type of sex you have.”
Earlier research suggested that HIV transmission was possible during oral sex, but the new study is being received as the strongest evidence that it may actually occur at a significant rate.
The new findings, which are based on retrospective data and subject to recall bias, may not resolve the question entirely. None the less, the researchers concluded that, even though oral sex was associated with a lower risk of transmission than were other sexual behaviours, it might be an important mode of transmission because of its frequency.
The results were presented at the recent 7th conference on retroviruses and opportunistic infections in San Francisco.