HIV: Nil By Mouth?

Dr. Shay Keating writes about the risks of oral transmission of HIV

One of the most frequently asked questions of a HIV specialist is ‘what is the risk of getting HIV from oral sex’?

This is a very difficult question to answer. There have been few well-designed studies undertaken, and most cases of HIV, reported to be as a consequence of oral sex, rely on the accurate disclosure of risk i.e., no anal or vaginal sex.

There are several cofactors which may, hypothetically, increase or decrease susceptibility to HIV infection through oral sex.These include dry mouth, trauma, sores, inflammation, concurrent sexually transmitted diseases, ejaculation and immunosuppression. It also depends on the probability that the sex partner – either the person performing or receiving oral sex – is HIV positive.

Saliva contains HIV-inhibitory properties; in other words, it does not support the replication of the virus. Therefore, if one has dry mouth (xerostomia) the risk of HIV infection may be theoretically be increased. Next, it has been speculated that poor oral health and hygiene, or recent gum or oral surgery, may play a role in increasing the risk of acquiring HIV through oral sex, due to the damage of the mucosa. Similarly, other sexually transmitted infections such as gonorrhoea or syphilis, may increase oral transmission of HIV. Smoking cigarettes also predisposes one to oral ulceration, and especially for a short period following smoking cessation. Ejaculation into the mouth would increase susceptibility, and scientific evidence suggests that tonsillar tissue is particularly susceptible to infection. Infection is also believed to be higher if the non HIV positive partner is immunocompromised, for example, on cancer chemotherapy or high dose steroid medication.

Partner infectiousness is also a risk. One would need to know the risk that the sexual partner is HIV positive. If so, the viral load, or level of the virus in the blood, would be higher at extremes or infection, at seroconversion or very early disease, and in advanced disease. Reported risk of unprotected oral sex with a HIV positive partner, who is not on antiretroviral medication, (ART) is 1 in 2500.

When on appropriate and effective ART, and when the viral load is undetectable, the risk of acquiring HIV through the oral route must be very low indeed. It could be argued that HIV acquisition following unprotected oral sex, in the absence of any oral, penile or vaginal disease, is extremely low with a partner who is virally suppressed on ARTs. Reports of such transmission of HIV through oral sex, when virally suppressed, are awaited, and we cannot definitively say that there is no risk.

Dr. James (Shay) N. Keating, BA Mod, MB, PhD. MRCP, Dip GUM, Dip Occ Med., has his clinic at the Harold’s Cross Surgery, Harolds Cross, Dublin 6W, and is a Specialist in Genitourinary Medicine at St. James’s Hospital, Dublin. Contact Phone: (01) 497 0022 or (087) 234 5551

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