Perth Group reasoning 2 March 2004
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Peter J Flegg,
Consultant Physician
Blackpool, UK, FY3 8NR

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Re: Perth Group reasoning

I have already said that I do not have the time to deconstruct every claim that the Perth Group make, but I urge all those following this debate (including Julian Turningheart, who seems to think the Perth Group produce notably erudite and thorough papers) to consider the following as a sample of their deductive reasoning (1).

Quote: “Gray et al concluded: "The probability of HIV transmission per sex act in Uganda is comparable to that in other populations, suggesting that infectivity of HIV subtypes cannot explain the explosive epidemic in Africa". If: (i) there is no more heterosexual transmission in Africa than anywhere else; (ii) in the Padian prospective study the transmission was zero; then in Africa, like anywhere else, "HIV" is not sexually transmitted”.

As an example of a non-sequitur, this statement takes some beating. I have seldom seen such a good example of circuitous logic. Lets look at it again:

(i) Someone suggested that HIV transmission frequencies in Africa are similar to those recorded elsewhere, and (ii) Someone else saw no HIV transmission in a prospective study in Northern California. Ergo: HIV is not sexually transmitted (In Africa or anywhere).

However, as incredible as this statement appears, things get even worse, for neither of the studies referred to support what the Perth Group claim they do. Dissidents have consistently misrepresented these studies over a number of years and distorted their findings to fit their preconceptions.

The first study is by the Rakai Project Team, which has published widely on heterosexually acquired HIV in Uganda. The statement contained in its Lancet study (2) about HIV transmission probabilities tells but part of the story, and is out of context. One of the study’s key proposals was to study differing infectivity of HIV-1 subtypes. (“The eastern and southern African HIV epidemic is predominantly caused by HIV-1 subtypes A, C, and D, and the rapid progression of the epidemic in these parts of Africa might, in part, be associated with greater infectivity of these HIV -1 subtypes. We assessed this possibility by examining transmission probabilities for subtypes A and D in Uganda. Conversely, some have postulated that the slower evolution of the HIV epidemic in western Africa might be due to the higher proportion of less transmissable recombinant HIV-1 subtypes in that region. To address these issues, we estimated the per-contact probability of HIV-1 transmission among monogamous, heterosexual HIV-1-discordant couples in rural Rakai District, Uganda, in which the HIV-1 epidemic is due to viral subtypes A and D.”)

So part of their study proposal was to determine if differing subtypes of HIV had differing infectivity. They state: “since the transmission probabilities per act of sexual intercourse in these populations are similar, the generalised HIV-1 epidemic in Uganda is unlikely to be caused by a greater infectivity of subtypes A and D” and conclude: “…greater infectivity of predominant HIV-1 viral subtypes is unlikely to account for the explosive HIV-1 epidemic in sub-Saharan Africa.”

This statement does not mean what many dissidents imply (i.e. that sexually-transmitted HIV cannot account for the “AIDS” epidemic), but merely that subtype variability does not account for the explosive nature of the epidemic in Uganda. Indeed, the Rakai Project authors give clues as to what is really relevant, since their “headline” conclusion was that “Higher viral load and genital ulceration are the main determinants of HIV -1 transmission per coital act in this Ugandan population.“

It is difficult to construe how this is evidence that HIV is not sexually transmitted in Africa. The principal Investigator with the Rakai Project, Professor Maria Wawer has testified in 2003 to the US Senate on prevention of HIV spread in Africa; a glance through her testimony will offer readers an idea of how she thinks HIV is transmitted (3). I would rather trust the Rakai Project’s investigators’ conclusions about the relevance of their own study than the Perth Group’s reinterpretation.

The second paper to be misconstrued by the Perth Group is the “Padian study” (4), so beloved by dissidents over the years because it found a low transmission rate of HIV in heterosexual couples (hardly surprising, because the couples had already demonstrated a low likelihood of transmission prior to study entry, they all entered the study well after the highest risk transmission period for HIV (which is around seroconversion), they were all advised on safe sex precautions during the study and widely used barrier techniques). The Perth Group actually refer to only one part of Padian’s study (naturally enough the part that can be most easily reinterpreted as corroborating their claim). However, overall there was still a transmission rate of 16% between the 442 serodiscordant couples in the study.

Again, I would prefer to accept Padian’s interpretation of what her own studies show, rather than what the Perth Group thinks they show. Professor Padian has even had to publicly refute some of the dissident claims concerning her studies (5).

These papers, like those of the Rakai Project, do not support any possible interpretation that HIV is not sexually transmitted. To use them as “proof” of such merely demonstrates how shallow is the science base upon which the PG relies for their “evidence”.

(1) Perth Group. More responses to Christopher Noble. BMJ rapid responses, 24 Feb 2004.

(2) Rakai Project Team. Probability of HIV-1 transmission per coital act in monogamous, heterosexual, HIV-1-discordant couples in Rakai, Uganda. The Lancet 2001; Volume 357: Pages 1149-1153.

(3) Wawer, Maria. AIDS Crisis in Africa. Testimony to the US Senate Committee on Health, Education, Labor and Pensions. March 27, 2003.

(4) NS Padian, SC Shiboski, SO Glass and E Vittinghoff. Heterosexual transmission of human immunodeficiency virus (HIV) in northern California: results from a ten-year study. American Journal of Epidemiology, 1997; Vol 146, 350-357.

(5) Jay Levy, Nancy Padian, Jeff Sheehy. Proven Connection - HIV Causes AIDS. Differences between U.S. and African epidemics don't disprove cause of both. San Fransisco Chronicle Tuesday, May 30, 2000

Competing interests: None declared