As the risk of transmission through oral sex is estimated to be much lower than for vaginal and anal intercourse in the absence of antiretroviral therapy, it is implausible that the risk of transmission through oral sex is not affected in the same way as other sexual transmission risks when effective treatment suppresses viral load. When HIV is not fully supressed, the risk of HIV transmission through the mouth is certainly smaller than through vaginal or anal intercourse.
If undamaged, the tissues of the mouth and throat are thought to be less susceptible to infection than genital or anal tissues, and an enzyme in saliva also acts to inhibit HIV. Very few cases of transmission through oral sex have been reported amongst gay men despite the continued practice of oral sex often with ejaculation into the mouth by large numbers of men over many years. There are no reliable reports of HIV being transmitted from the mouth to the genitals.
Cases of transmission via cunnilingus are extremely rare, and the reliability of these reports is questionable. There are no reported cases of HIV transmission through kissing. HIV is not able to infect most cells in the mouth. Only one cell type found in the mouth is vulnerable to HIV infection Campo. The tissue of the mouth and oesophagus is also very thick compared with genital tissues, and fluids stay in contact with it for a very short time because swallowing clears the mouth regularly.
The mouth is therefore generally regarded as an unlikely route of HIV transmission. Saliva contains numerous factors that have been found to inhibit HIV and stomach acid is likely to inactivate HIV in the same way as other viruses Malmud. Case reports of infections through oral sex suggest that factors which may increase the chance of HIV infection through oral sex include:. Brushing the teeth and gums often causes mild abrasions and stimulates bleeding. Safer sex guidelines have sometimes suggested that recent brushing can increase the risk of infection through oral sex.
The risk of HIV transmission through vaginal or anal intercourse is effectively zero if a person with HIV is on treatment and has a fully suppressed viral load. It is logical that if HIV cannot be transmitted through anal or vaginal intercourse when viral load is fully suppressed, the same will apply to oral sex.
