The risk of HIV transmission associated with fellatio remains a contentious issue following the finding of the Sydney Men and Sexual Health Study (SMASH) that unprotected oral sex alone does not lead to HIV infection.
This prospective cohort study of over 700 men has found that 95% of men who had casual sexual partners reported having oral sex without a condom. Although receptive oral sex with ejaculation was reported by 26% of men, it was not associated with an increased risk of seroconversion.
According to researcher Garrett Prestage from the National Centre for Epidemiology and Clinical Research, SMASH found that "if you control for anal intercourse without a condom then there was absolutely NO risk of seroconversion associated with oral sex". Nevertheless, Mr Prestage did acknowledge that transmission is possible "under unusual circumstances (such as recent dental work or sores in the mouth)".
"With oral sex being almost universal among gay men, and oral sex with ejaculation also being very widespread, you would have to think that if seroconversions were very likely during oral sex then HIV infection would have to be far more commonplace among gay men," Mr Prestage said.
These Australian findings conflict with a highly publicised study presented at the recent Retroviruses Conference which found that 8% of seroconversions in San Francisco can be attributed to oral sex.
Interestingly, interviews with 75 seroconverters in Sydney indicated that unprotected receptive oral sex was the likely source of HIV infection in seven cases. These men denied having unprotected anal sex around the time of seroconversion.
The researchers have explained these contradictory findings by questioning the reliability of reported behaviours after seroconversion. Garrett Prestage told aidsmap that "the seroconversion study data are based on interviews with men after they have seroconverted. It is difficult to assess just how much weight to give the few interviews where oral sex was intimated as the reason. How much is rationalisation? How much is denial? What we do know is that it was only a few interviews; there are even some peculiarities and uncertainties about some of these which suggest that they should be treated with caution."
The studies were reported at the HIV/AIDS and Related Diseases (HARD) Social Research Conference in Sydney, Australia, 13-14 May 2000.
Grulich AE, Prestage G et al. Oral sex as a risk factor for HIV: a review of Australian data, HARD Conference, Sydney, 2000.