(SAN FRANCISCO, CA) -- A significant number of gay men are becoming infected with the AIDS virus through oral sex -- an activity that was rumored to be safe, researchers said on Tuesday.

A study presented at a meeting of AIDS researchers found nearly 8 percent of recently infected men in the San Francisco area were infected through oral sex.

``This was higher than we expected,'' said Dr. Frederick Hecht of the University of California San Francisco, who helped lead the study.

Hecht's team and a group at the Centers for Disease Control and Prevention (CDC) surveyed 102 gay and bisexual men recently infected with HIV and found oral sex was the only risky behavior that eight of the men had engaged in.

``It's certainly sobering news,'' Dr. Ronald Valdiserri, deputy director of the CDC's HIV prevention center, said in a telephone interview.

``We've known ... that there was a risk of HIV transmission through oral sex. Of course scientists indicated that they thought it was a much smaller risk compared to anal or vaginal sex.''

Hecht said many of the men he interviewed did not know there was much of a risk at all. ``Even though oral sex might be low-risk, it is not without risk,'' he said in an interview. And if people do it often enough ``it can add up''.

Studies have shown that some gay men consciously substitute oral sex for anal sex. ``They think they are being careful,'' Hecht said. The study showed this could be a deadly mistake.


LOBBYING FOR PREVENTION AND TREATMENT

Valdiserri said the news was even more disappointing because the men involved lived in San Francisco -- a city where the gay community has been very actively involved in studying AIDS and lobbying for prevention and treatment.

``Here are men from San Francisco, a city which probably compared to many American cities has more community-based resources for gay men ... and these men did not really understand that receptive oral intercourse could lead to HIV infection,'' he said.

HIV is passed on through bodily fluids such as semen or blood, which is why sexual activity and injecting drug use are so risky.

Having a cut or sore inside the mouth greatly increases the chances of transmission, and many people can have tiny abrasions of the mouth or gums without being aware of them.

``It doesn't have to be a gaping sore or ulcer,'' Valdiserri said.

He said the study was very carefully done, and the men were able to pinpoint exactly when they became infected.

``We definitely believe that this is perhaps the most definitive study to date on oral sex transmission among gay men,'' Valdiserri said.

The researchers did not count a man as having been infected through oral sex if he said he had engaged in any other risk behaviors. ``Because of these stringent requirements, 7.8 percent may be an underestimate of transmission through oral sex in this group,'' the CDC said in a statement.

Dr. Paul Denning of the CDC told the conference that gay men were starting to return to risky behaviors. ``We are working to expand surveillance and counseling,'' he said.

Other studies suggest people are becoming complacent about the risks because of drugs that keep HIV-infected people alive. And Denning said some people just have not heard the messages. ``Every year, a whole new generation of kids becomes sexually active, and often they are not provided with sex education,'' he said.