The case involved a man who most likely transmitted HIV to his female sexual partner through deep kissing. The source of the infection was an HIV-positive man who had a history of gum disease. He reported that his gums frequently bled after he brushed and flossed his teeth. He reported that he generally engaged in sexual intercourse and deep kissing at night after he brushed his teeth. Under these circumstances, the woman he was kissing was exposed to saliva contaminated with blood. As you will note in Frequently Asked Questions about Safe Sex and Prevention, under the question, "Which body fluids can transmit the HIV virus, and which ones don't?" it specifically states:
"Saliva, tears, sweat and urine can have the virus in them, but in such small concentrations that nobody has ever been infected through them. However, if any body fluid is visibly contaminated with blood, the risk of transmission exists."
In this case, the woman was exposed to saliva mixed with blood. This is a known risk, due to exposure to blood. The woman also had a history of gum disease. When a person has gum disease, it is easier for them to become infected. If a person has gum disease, and they get blood, semen or vaginal secretions in their mouth, their risk of infection increases. This is because having gum disease would make it easier for HIV to enter the bloodstream. Therefore in this case, the woman was directly exposed to the man's blood, and the blood had a direct access to her bloodstream. For more information on gum disease and HIV, see the question, "Hypertension or Gum Disease a Symptom?"
In order for a person to become infected with HIV, three things must happen:
Under the circumstances in this case, all three requirements for transmission were met. The woman was directly exposed to blood, the blood had an access to her bloodstream -- especially since she had gum disease -- and the virus went from one person directly to the other.
Transmission through kissing is extremely unusual. In all of the thousands and thousands of cases of HIV/AIDS reported, this is the first case that was probably due to kissing. With all the kissing that occurs everyday, the fact that it took this many years to find our first case through kissing proves that this is an extremely unusual event. It was so unusual, that it got published in the medical literature.
There is still a chance that the woman was infected in ways other than kissing. This woman had protected vaginal intercourse with this man. Although condoms do significantly reduce the risk of transmission, they are not 100% effective. The couple did not report any condom failures that they were aware of. But the possibility of a condom failure that the couple did not notice cannot be excluded. There was also oral sex between this couple; however they reported that this did not involve the exchange of blood or semen between them. In addition, the woman stated that she had used the man's toothbrush on one occasion, and used his razor on another occasion. However she stated that she did not notice blood on either of them. So although deep kissing was the probable route of infection, these other possibilities cannot be excluded.
In a similar case, a man got infected when he got bitten by an HIV-infected woman. In this case too, there was visible blood in the woman's saliva, and the saliva had a direct route to the man's bloodstream (when his skin got broken by the bite). This too, was a very unusual event.
These two cases reinforce what I have been saying all along. Although saliva alone is a very low risk, if there is visible blood in saliva, then the risk of transmission does exist. Luckily, the vast majority of times, a person does not have visible blood in his or her mouth. Based on all available data, these two cases (the kiss and the bite) were extremely unusual events.
Do you want more information on AIDS, STDs or safer sex? Contact the U.S. Centers for Disease Control AIDS hotline, open 24 hours a day, seven days a week, at 1-800-CDC-INFO. Or visit The Body's Safe Sex and Prevention Forum.
Until next time . . . Work hard, play hard, play safe, stay sober!