• oral sex
• HIV transmission

It is well established that oral sex may lead to the transmission of a wide variety of STIs, including HIV.^1–4 As discussed elsewhere in this issue (see syphilis symposium, pp 309–26) oral sex appears to be important in the resurgence of early infectious syphilis in the United Kingdom. Many of these latter cases have been in HIV positive individuals and it is likely that co-infection with syphilis would increase the risk of (oral) transmission of HIV—as has been shown similarly in numerous studies of genital HIV/STI co-infection.

Despite recognising that transmission does occur, some feel that the underlying risk of HIV transmission via oral sex is so low as to be negligible. However, two recent studies (as yet unpublished in peer review journals) suggest that oral sex may be contributing to a higher proportion of new HIV infections than previously thought. In the first study, of 102 men who had recently seroconverted, eight (7.8%) were attributed to oral sex. Of these eight, unprotected oral sex was the only risk factor in four, but four had also had protected anal sex.⁵ A second study from my own unit was of 494 HIV positive patients (mostly homosexual) who completed a questionnaire on sexual behaviour. Six per cent believed themselves to have been infected because of oral sex alone. Further follow up of these and other patients in our unit, who believe themselves to have been infected by unprotected oral sex is ongoing and about half, where data are available, have had recurrent infections of the mouth, which could have increased their risk.⁶

A third report of two studies from Australia, gave contradictory results. An interview study found that a similar proportion, seven of 75 (9.3%), homosexual men gave receptive oral intercourse as the likely source …