Christopher S Tyler,
Provo, Utah 84604
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I believe Matthew Grove missunderstands what The Perth Group is saying with regard uni/bidirectional transmission.
He states: ...surely both partners in a male homosexual relationship can be either passive or active in any given sexual act, and may be active on one occasion and passive on another. So transmission is bidirectional.
The statement, "So transmission is bidirectional." is incorrect.
A bidirectionally transmitted std can be transmitted by the active partner, and also recieved FROM the passive partner PER SEXUAL ACT. In other words, if a male homosexual couple were 100 consistent in practicing position, that is, one partner always being a 'top' and the other always a 'bottom', either could become infected with a bidirectionally transmitted std without switching positions. The top could get it from the bottom, the bottom from the top.
For a unidirectionally transmitted agent, it would indeed require both partners to 'swap' and practice either role, i.e., being passive (bottom) AND being active (top).
In a study published in 1984 Robert Gallo wrote: "of eight different sex acts, seropositivity correlated only with receptive anal intercourse...and was **inversely correlated with insertive anal intercourse**.1
Therein lies the problem with what is said to be HIV, as it (a positive antibody test) behaves like a unidirectionally transmitted std. This presents great problems for places like Africa where it is assumed that heterosexual sex is the leading form of transmission. In other words, a man transmits it to a woman, or a woman transmits it to a man. Example of bidirectional transmition: A man who is married goes and has sex with an infected prostitute through vaginal sexual intercourse and she transmits it to him (passive to active). He comes home and transmits it to his wife through vaginal sexual intercourse (active to passive). In other words, the man in this scenario has not been the passive partner, yet has acquired the infection from the passive partner.
The Perth Group argues that this scenario is not backed up by published data and a reason they cite the much discussed Padien study:
Heterosexual Transmission of Human Immunodeficiency Virus (HIV) in Northern California; Results from a Ten-Year Study.
"Prospective results. We followed 175 HIV-discordant couples over time, for a total of approximately 282 couple-years of follow-up...At last follow-up, couples were much more likely to be abstinent or to use condoms consistently, and were much less likely to practice anal intercourse (p < 0.0005 for all). Nevertheless, only 75% reported consistent condom use in the 6 months prior to their final follow-up visit... no seroconversions occurred among exposed partners".
Considering the data above, how then do men become infected if HIV is only transmitted from the active partner (male) to the passive partner (female)? Are the majority of antibody positive males in Africa bisexual and practice frequent receptive anal intercourse? This, I believe, is one of many reasons The Perth Group consistently ask for the data proving that HIV is a heterosexually sexually transmitted disease. There are many other reasons for a positive antibody test, but by and large, the assumption is that it is because of infection by a retrovirus.
It is therefore an assumption that when a gay man becomes antibody positive (whatever that may mean in a given location) it is because he is infected with a virus. The Perth Group question this assumption of bidirectionality.
----- 1. Goedert JJ, Sarngadharan MG, Biggar RJ, et al. (1984). Determinants of retrovirus (HTLV-III) antibody and immunodeficiency conditions in homosexual men. Lancet 2:711-6.
Competing interests: None declared