Although it is well known that other sexually transmitted diseases, especially herpes, can be passed from the mouth to the penis, vagina or anus, no reliable report exists of a case where HIV was transmitted from the mouth to the genitals, except for a widely criticised French report describing two men who claimed to have no other risk factors for HIV infection apart from having been insertive in oral sex i.e. receiving a blow job (Rozenbaum).

There are a number of methodological problems with this report. First of all, the authors claim it to be part of a cohort study which was regularly monitored, yet data on this cohort has never subsequently been published in a peer–reviewed journal to allow independent validation of the methodology. The authors estimated that the chance of failure to recall or deception of the interviewers regarding sexual practices on the part of the five individuals reported to have been infected was minimal. The authors state:

We assessed the likelihood of these patients denying anal sex for psychological reasons, and concluded that it was unlikely: three patients had freely described participating in anal sex previously... .

There is, in other words, no evidence that the methodology was sufficiently adapted to account for lack of patient recall, or for a shame factor that could easily prevent someone confessing to unsafe sex. The fact that someone could happily admit to having unsafe sex before joining a safer sex study by no means precludes this kind of guilt at having unsafe sex after joining such a study.

One case of oral transmission has been reported in which a man who was impotent owing to diabetic illness claimed to have been infected after performing cunnilingus on a prostitute. It was subsequently established that the woman was HIV–negative, and that the man had in fact been infected through needle-sharing.