This belief is, of course, misguided on so many levels that I wanted to give an overview of the general routes of transmission to try and achieve some kind of clarification.

Semen transmits some major diseases, namely, HIV, Hepatitis B and Hepatitis C. It can also transmit other diseases such as HTLV, a retrovirus that was once considered to be a possible cause of AIDS, but this isn’t worth worrying about for the average person. In any case, these conditions are blood-borne systemic infections, meaning that they need to get into the bloodstream somehow in order to cause the disease and that they infect the whole body, winding up in body fluids such as blood and genital secretions.

Obviously the person with the most risk of disease is the person receiving the semen into the body, not the donor of the semen. This is why men give these diseases to women more easily than they get them from women. Likewise among gay or bisexual men, those who receive semen anally are much more likely to become infected than those who don’t.

It should also be noted that women who engage in anal receptive sex are equally vulnerable. Infected semen is much more likely to get into the bloodstream through the anal tissue than through the vaginal tissue because the former is more delicate and because it is designed for absorption. Think of how medications (or even street drugs) can enter the body through the use of a rectal suppository. Narcotics addicts who no longer have good veins in which to inject drugs can get high by inserting pills (not needles, one would hope) into the rectum.

Cervical fluids in women can transmit the virus to men during intercourse, but this is much less likely because these fluids are generally less infectious than semen and because the opportunities for infection through the male urethra are obviously limited.

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