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Primary HIV Infection Associated with Oral Transmission

March 2000

Many persons have inquired about the results of a study presented as a poster at the recent 7th National Conference on Retroviruses and Opportunistic Infections, held January 30-February 2. The following questions and answers contain more specific information about the presented study results.

Question: What is this study about?

Answer: This study, one component of a primary and recent HIV infection study called the Options Project, is funded by the Centers for Disease Control and Prevention (CDC) at the University of California, San Francisco. The purpose of this particular study was to ascertain the extent of HIV transmitted by oral sex among men who have sex with men and who were identified with HIV within 12 months of becoming infected.

Question: Hasn't oral sex already been identified as a method of transmitting HIV?

Answer: Yes. However, this is the most definitive study to date. Earlier studies have been published (see the bibliography at the end of these questions/answers).

Question: What is the risk of HIV transmission from oral sex?

Answer: The likelihood of transmission of HIV from an infected person to an uninfected person varies significantly depending on the type of exposure or contact involved. The risk of becoming infected with HIV through unprotected (without a condom) oral sex is lower than that of unprotected anal or vaginal sex. However, a lower-risk activity will increase in risk when it is done often enough. The Options Project found that 7.8% (8 of 102) of recently infected men who have sex with men in San Francisco were probably infected through oral sex. Most of these men believed that the risk was minimal or non-existent.

Question: What are the exact ways that HIV was transmitted in this study?

Answer: Nearly half (3 of 8) of these cases reported oral problems, including occasional bleeding gums. Almost all (7 of 8) of these men reported to have had oral contact with pre-semen or semen.

Question: How do you know if the study participants were telling the truth about their sexual history?

Answer: Oral transmission of HIV is very difficult to single out as the only way that HIV is transmitted because few people engage exclusively in oral sex. A number of specific questions were asked by a trained evaluator. The participants' risk behaviors were assessed by using clinical interviews, counselor intervention, epidemiologic interviews, partner interviews when possible, and final disposition of transmission risk. Of the 8 cases, 4 reported protected anal intercourse -- without the condom breaking -- with persons who were either HIV-infected or had an unknown serostatus. Men in this study who reported that they were uncertain if the condom was used properly were eliminated from this study.

Question: Was this a surprise finding?

Answer: Yes and No. The risk of oral sex transmission (8%) in this study is higher than many researchers had previously thought or found in other studies. More media attention appeared to be placed on this particular study, probably because of the higher number of study participants. There appears to be evidence that higher-risk activities (anal sex) among men who have sex with men is decreasing while lower-risk activities (oral sex) among these men is increasing. Oral sex has always been considered a lower-risk activity but is certainly not risk free.

Question: What can be done to prevent HIV?

Answer: The study results emphasize that any type of sexual activity with an infected person is a risk of HIV transmission. Oral sex with someone who is infected with HIV is certainly not risk free. Prevention of HIV is more important than ever. Some persons have indicated that they are less concerned about HIV because of new treatments and are being less careful. This study presents a wake-up call to everyone -- that HIV is far from over and remains a serious, lifelong disease that is best to prevent. CDC' s recommendations on how to prevent sexual transmission of HIV remain the same. Protection requires abstaining from sexual activity or taking precautions with all types of intercourse -- either having sex with only one uninfected partner, using condoms for sexual intercourse and oral sex, and using lower risk activities such as mutual masturbation.

Question: Where can I get more information about transmission and prevention of HIV?

Answer: CDC operates a toll-free, confidential National STD/AIDS Hotline which can assist callers with these types of concerns. The English and Spanish service (24 hours a day, 7 days a week) can be reached by calling 1-800-CDC-INFO; TTY service for Deaf and Hard of Hearing is 1-888-232-6348.


  1. Berrey M, Shea T. Oral sex HIV transmission (letter). Journal AIDS 1997; 475.

  2. Bratt GA, Berglund T, Glantzberg BL, Albert J, Sandstrom E. Two cases of oral to genital HIV-1 transmission. International Journal of STD & AIDS 1997; 8:522-525.

  3. Clifford L. HIV seroconversion and oral intercourse. AJPH 1991;81:698. Edwards SK, White C. HIV seroconversion illness after orogenital contact with successful contact tracing. International Journal of STD & AIDS. 1995; 6:50-51

  4. Keet PM, Albrecht Van Lent IV, Sandfort TG, Coutinho RA, Van Griensven GJ. Orogenital sex and the transmission of HIV among homosexual men. AIDS 1992;6:223-226.

    9 cases in a cohort of 102

  5. Lifson AR, O'Malley PM, Hessol NA, Buchbinder SP, Cannon L, Rutherford GW. HIV seroconversion in two homosexual mean after receptive oral intercourse with ejaculation. AJPH 1991;80:1509-1510.

  6. Quarto C, Germinario C, Troiano T, Fontana A, Barbuti S. HIV transmission by fellatio (letter). European Journal of Epidemiology 1990;9:339-340

    (heterosexual female to male oral transmission)

  7. Robinson ED, Evans BGl. Oral sex and HIV transmission. AIDS 1999;16(6):737-8.

  8. Schacker T, Collier AC, Hughes J, Shea T, Corey L. Clinical and epidemiologic features of primary HIV infection. Annals of Internal Medicine 1996;125:256-264.

    (4 cases in a cohort of 46 reported only oral risk)

  9. Spitzer P, Weiner NJ. Transmission of HIV infection from a woman to a man by oral sex (letter). New England Journal of Medicine 1989;320:251.

For More Information

CDC National AIDS Hotline: 1-800-CDC-INFO
Deaf: 1-888-232-6348

CDC National Prevention Information Network: 1-800-458-5231
P.O. Box 6003
Rockville, Maryland 20849-6003

Internet Resources:

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This article was provided by U.S. Centers for Disease Control and Prevention. Visit the CDC's website to find out more about their activities, publications and services.
See Also
More Research on Oral Sex and HIV/AIDS