To date, the evidence has been largely anecdotal. Researchers have identified 30 or so cases in which oral sex was the only reported risk factor but in the gay community, at least, many men have assumed that the risk is infinitesimal. Because doctors and scientists all agree that the risk is pretty low, many AIDS educators have also recently reduced their efforts to convince people not to have oral sex so they can focus all their attention on discouraging them from having unprotected anal sex.

Now researchers at the University of California at San Francisco have launched the first study designed to isolate the risk factors involved in oral transmission by comparing men who have been infected orally with those who have engaged in oral sex but have not been infected. "It's very important, so I'm really glad they're doing it," says Tim Teeter, associate director of treatment support at the San Francisco AIDS Foundation. "It's been such a gray area, and at a time when sero conversions are on the increase, this could help people to further assess their risk."

UCSF's Center for AIDS Prevention Studies is conducting the study in collaboration with the Oral AIDS Center at the university's dental school and AIDS Health Project, a San Francisco education and counseling organization. Kimberly Page-Shafer, an assistant professor at the Center for AIDS Prevention Studies and the principal investigator for the HIV Oral Transmission study, spoke recently with Salon.

Why was this something that needed to be done?

This is an issue that won't go away. The majority of sexually active people have oral sex and they want to know. Everybody asks about this when they go to get tested for HIV. And the fact is, we don't know what may increase or decrease a person's chances of acquiring it through oral sex. It's amazing to me how much supposed knowledge has built up around this issue when there is actually no scientific data.

What are some of the ideas about what makes oral transmission possible?

The kind of information that's circulating about that is amazing. I've talked to a lot of counselors, and none of them tell patients the same thing. Some say use mouthwash, others say don't use mouthwash. Some say don't floss or brush for an hour before and after, others say for four hours. One of the things that people are advancing as intuitive is having gingivitis increases the risk, but the truth is that everyone has gingivitis. Some clients want to know if they should have a Popsicle or drink tea beforehand to freeze the virus or burn it. I heard a counselor tell someone that they should be careful when they eat popcorn because a kernel could get stuck between the teeth or cut the gum and create a portal of entry.