[supercat]

My cousin was an intern at UCSF in the mid-1980s, and in 1985 he told me that anal sex between homosexual men was and would remain the principle vector of transmission.

Is there any reason to believe that anal sex between homosexual men is a more effective disease vector than anal sex between a man and a woman? My impression is that in Africa the latter is the primary disease vector.

[Sabertooth]

Is there any reason to believe that anal sex between homosexual men is a more effective disease vector than anal sex between a man and a woman? My impression is that in Africa the latter is the primary disease vector.

Yes, women are a natural, though not 100% effective, firewall against transmission and retransmission of the HIV virus. There are a few reasons.

First of all, heterosexual anal sex comprises quite a low percentage of all heterosexual acts, which is a large factor lower than its proportion of homosexual acts.

Also, anal sex is primarily a one way transmission, from the penetrator to the penetrated (there's an exception which I'll get to in a moment). Since women are viurtually never the penetrators of men during anal sex in a fashion which facilitates the transmission of the virus to the man, there is almost no retransmission. This also explains the low incidence of HIV infection among lesbians.

The exception I mentioned is the presence of another veneral disease in either partner. In cases where the woman has an active venereal disease, particularly with open lesions, vaginal or rectal retransmission to a man is possible. This explains almost all of the very few true instances where women have infected men with HIV via sexual contact.

All of this was explained to me by my cousin, now a cardiologist, back in 1985.

The aberrant AIDS data from Africa merit further study, however, some follow-up studies I've seen indicate that the data isn't all that aberrant from the model described to me by my cousin 17 years ago.

Bisexuality is far more common in Africa than is reported, in part because in many Third World countries, only the receiver in anal sex acts is considered to be homosexual. Therefore, homosexual transmission in Africa is underreported. Also, venereal diseases are more common in Africa, in part because of lower access to antibiotics, thus facilitating retransmission by women beyond the numbers seen in developed countries.

One more thing, and this is just my own hunch, but the greater incidence of blood-borne diseaes, biting insects, open sores, or other stress factors on immune systems in Africa may be increasing the susceptibility of Africans to HIV infection and the subsequent development of full-blown AIDS.