Oral sex transmission rate is higher than expected

Research debunks myth that oral sex isn’t risky

Clinicians who need more proof when trying to convince HIV patients that they must use condoms during all sexual acts now can point to a study newly released by the Centers for Disease Control and Prevention (CDC) in Atlanta, which found that 7.8% of HIV-infected men who had oral sex with other men were infected with HIV through oral sex.

The CDC investigators cautioned that this might be an underestimate of transmission through oral sex because the study had stringent requirements for determining the mode of transmission.

CDC researcher Beth Dillion, MSW, MPH, presented the study’s findings at the 7th Confer ence on Retroviruses and Opportunistic Infec tions in San Francisco.

"What’s important about this particular study is it’s the most definitive look to date at the issue of HIV transmission and oral sex," says Ronald Valdiserri, MD, MPH, deputy director of the National Center for HIV, STD & TB Prevention at the CDC.

Valdiserri says researchers were surprised that the oral sex transmission rate was so high, and they are concerned that gay men consider oral sex to have little or no risk of HIV transmission.

"Although oral sex represents an infrequent mode of transmission, our concern is that people were taking the message that oral sex was safe sex and didn’t carry a risk of transmission," he says. "But what this study shows is that even a low-risk activity — and it is lower-risk than unprotected anal intercourse — can result in transmission."

The CDC collaborated with researchers at the University of California, San Francisco’s Options Project, to assess risk behavior among 102 gay and bisexual men who were recently infected with HIV. For eight of the men in the study, oral sex was the only risk behavior.1

New testing technology made it possible for researchers to find men who had become newly infected with HIV, which in turn made it easier to determine how they became infected.

"The older studies were hampered by the fact they were dealing with individuals who might have been infected for years, and that made it difficult to relate particular sexual activity to serosta tus," Valdiserri says. "This study looked at newly infected individuals."

The study determined the time period for transmission through the pairing of a sensitive HIV RNA test with a less sensitive antibody test in both men who had a suspected recent conversion or had a documented seroconversion within 12 months of the study’s enrollment. "For some men in this study, we were able to pinpoint the time they seroconverted," Valdiserri says.

While the study looked only at men who have sex with men, its findings have implications for oral sex among heterosexual and lesbian couples, as well. "There are reports of transmission through cunnilingus," Valdiserri says.

Clinicians should emphasize to their HIV patients and at-risk patients that oral sex is not safe unless participants use condoms or dental dams.

"We’re trying to get the word out to community-based organizations and also to partner organizations that provide information to adolescents," Valdiserri says. "Our concern is there have been other studies that report among groups of adolescents that oral sex is clearly being used as a substitute for vaginal sex as a way to protect virginity."

So youths need to be told that they can become infected with HIV, as well as other sexually transmitted diseases, through oral sex, he adds.

Another CDC study underscored the importance of continued emphasis on HIV prevention and safe-sex messages reaching targeted populations, including youths, women, minorities, and gay and bisexual men. This study of 1,976 HIV-negative or untested people at risk for HIV infection found that 31% were less concerned about becoming infected and 17% were less careful about sex or drug use because of the success of the new antiretroviral treatments.

The study, which also was presented at the retroviruses conference in San Francisco, drew its data from a seven-state HIV testing survey. The survey interviewed 693 gay and bisexual men recruited at bars, 683 heterosexuals recruited from STD clinics, and 600 injection drug users found on the street.

Injection drug users showed the least concern about becoming infected because of better treatments, with 40% expressing less concern about HIV infection and 25% reporting they were being less careful. Among heterosexuals, 30% said they were less concerned and 15% said they were less careful, and 25% of gay and bisexual men said they were less concerned, while 13% said they were less careful.


1. Dillon B, Hecht F, Swanson M, et al. Primary HIV infection associated with oral transmission. Abstract 473. Presented at the 7th Conference on Retroviruses and Opportunistic Infections. San Francisco; Jan. 30-Feb. 2, 2000.