Q1. What is this MMWR about?

This MMWR describes the possible transmission of human immunodeficiency virus (HIV) by an unknown route from an HIV-infected man to his previously uninfected female sex partner. The findings from the epidemiological and laboratory investigations suggest that the woman was infected through mucous membrane exposure to the man's blood-contaminated saliva.

Q2. How was the female partner exposed?

While the exact route of transmission could not be determined with certainty, the most likely possibility is that the woman was infected through her mucous membrane by exposure to blood in her partner's saliva. This exposure most likely occurred during "deep kissing."

Q3. Does this mean that HIV can be transmitted by saliva?

Exposure to saliva itself is considered only a theoretical cause of HIV transmission for at least five reasons: 1) saliva has proteins that reduce HIV-1 infectivity; 2) HIV is rarely isolated from saliva; 3) none of the approximately 500,000 cases of AIDS reported to CDC have been attributed to exposure to saliva; 4) levels of HIV are low in the saliva of HIV-infected persons, even in people with periodontal disease (bleeding gums or lesions); and 5) HIV transmission by kissing has never been documented in studies of nonsexual household contacts of HIV-infected persons. However, there have been extremely rare instances of transmission by severe human bites, in which the infected person's saliva was contaminated with HIV-infected blood.

Many factors in this case point to a blood-to-mucous membrane exposure. Both partners had extensive dental problems, including gingivitis (and the man had been diagnosed with oral hairy leukoplakia). Both had been undergoing dental treatment during the time exposure occurred. During this period, the man's CD4+ count was low, which may be associated with an increased infectivity and risk for transmission.

The couple reported engaging in deep kissing several times each month. The man reported that his gums frequently bled after he brushed and flossed his teeth, and that they usually engaged in sexual intercourse and deep kissing at night after he brushed his teeth.

Q4. Could the dentist have transmitted HIV to the woman?

The dentist was tested for HIV after the case was reported to CDC and tested negative.

Q5. Could the man have transmitted the virus to his partner during intercourse?

This is unlikely. The couple reported using a male latex condom during each act of vaginal intercourse. They said they did not have anal sex. They were not aware of any incidents of condom breakage or slippage between June 1994 and July 1995 (the interval during which seroconversion in the woman occurred); further, they stated that the condom had remained in place each time the penis was withdrawn. Although occasional instances of unprotected oral sex reportedly did not involve the exchange of semen or blood, this cannot be definitively ruled out as a possible route of transmission.

Q6. Could she have contracted it through some other route?

During the interval between her last negative HIV test and her first positive test, the woman reported having no known risk exposure to HIV (i.e., other sex partners; injection- and noninjection-drug use; sexually transmitted diseases; blood transfusion; artificial insemination; occupational exposure to HIV; or acupuncture, tattoos, body piercing, or other percutaneous injections).

Q7. Didn't the woman also report using the man's toothbrush and razor?

Yes, the woman reported using the man's toothbrush and razor on one occasion each. She reported that no blood was visible on either device, and she could not remember when these events occurred. Those possible exposures are not considered to be the source of HIV transmission in this case.

Q8. Hasn't transmission occurred in those ways?

Although HIV has been transmitted between family members in a household setting, this type of transmission is exceedingly rare. These transmission episodes are believed to have resulted from contact between skin or mucous membranes and infected blood. To prevent even such rare occurrences, precautions, as described in previously published guidelines, should be taken in all settingsCincluding the homeCto prevent exposures to the blood of persons who are HIV infected, at risk for HIV infection, or whose infection and risk status are unknown. For example, gloves should be worn during contact with blood or other body fluids that could possibly contain blood, such as urine, feces, or vomit. Cuts, sores, or breaks on both the care giver's and patient's exposed skin should be covered with bandages. Hands and other parts of the body should be washed immediately after contact with blood or other body fluids, and surfaces soiled with blood should be disinfected appropriately. Practices that increase the likelihood of blood contact, such as sharing of razors and toothbrushes, should be avoided.

Q9. How was CDC able to document the exposure so thoroughly?

The man and woman were enrolled in a study in which one partner is HIV- positive, the other is negative (also known as a discordant couple study). As part of this study they were periodically administered questionnaires and tested for HIV. The woman was HIV-negative in July 1994, but tested positive in July 1995 and again 6 weeks later in September 1995.

It should be noted that although sexual exposure through vaginal intercourse is a plausible route of transmission for this case, large studies of HIV-discordant couples over time show that HIV transmission is rare when heterosexual couples use condoms consistently and correctly for vaginal intercourse.

Q10. Will this change CDC's position regarding kissing and HIV transmission?

No. CDC maintains that casual contact through closed-mouth or "social" kissing is not a risk for transmission of HIV. Because of the potential for contact with blood during "French" or open-mouth kissing, CDC still recommends against engaging in this activity with an infected person.

Q11. What is the risk of HIV infection from oral sex?

Getting semen, vaginal secretions, or blood from an infected person in your mouth puts you at risk of HIV infection. The risk of getting HIV from oral sex is not as high as from anal or vaginal sex, but there is a risk. Sores or cuts anywhere in your mouth or on a partner's genitals would make oral sex even more risky.

Q12. Where can I find out more about this MMWR and HIV transmission in general?

The CDC National AIDS Hotline (1-800-CDC-INFO) has information specialists to answer questions or provide referrals on HIV infection and AIDS. Copies of this MMWR (July 11, 1997; vol. 46/no. 27) may be ordered through the Hotline.