Department of Medical Physics, Royal Perth Hospital, Perth, Western Australia,
John Papadimitriou, Barry Page, David Causer, Helman Alfonso
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The claim that HIV is heterosexually transmitted should not be accepted merely on the basis of assumptions and opinions
In Tony Floyd’s Rapid Response “Most Experts Suggest 90% of African Adult HIV is from heterosexual transmission, Gisselquist 30%” (5th April 2003), he wrote “The fact that 'most experts claim it is 90%, and that Gisselquist thinks it approximately 30%, leads one to ask why he has been cited to support claims that HIV isn't sexually transmitted?”
It needs to be stressed that what “most experts claim” is only an assumption (as his quote from Gisselquist points out: "For more than a decade, most experts have assumed that more than 90% of HIV in African adults results from heterosexual transmission”) as no proof has been provided.
Furthermore he quotes Gisselquist: “In this exercise, we show how data from studies of risk factors for HIV can be used to estimate the proportion from sexual transmission, and we present our estimates. Calculating two ways from available data, our two point estimates - we do not estimate confidence intervals - are that 25-29% of HIV incidence in African women and 30-35% in men is attributable to sexual transmission".
Apparently, Tony Floyd has only read the abstract from which he quoted. Had he read the article by Gisselquist he would have understood that various assumptions were made to obtain the stated estimate and that confidence limits could not be given. That is, it was only an “exercise” as stated to provide insight into estimates that could be obtained based upon the assumptions made. In the discussion section of the paper the authors wrote “We recognize that many questions can be raised about the data and about our procedures and we encourage those questions…We cannot and do not intend our estimates to be the last word, but rather a step toward better evidenced-based estimates of the proportions of HIV in Africa from sexual and other modes of transmission”.
This is backed up in their conclusion where the authors wrote “There are many considerations – focused on specific parameters – that suggest that the estimates we present are too high or too low”. Thus from this “exercise” nobody including Gisselquist has come to the conclusion that there is a 30% heterosexual transmission of HIV.
We neither misinterpreted nor falsely cited Gisselquist “to support claims that HIV isn’t sexually transmitted” as Tony Floyd stated. This is the quote from Gisselquist, which we cited in our rapid response “HIV in South Africa” (13 March 2003): “HIV is not transmitted by ‘sex’, but only by specific risky practices”. We gave the reference in our rapid responses of 13th March 2003 and 24th March 2003. We gave the reference again as well as its location in the article in our rapid response of 27th March 2003.
In Tony Floyd’s Rapid Response of 7th April 2003 “Heterosexual Intercourse Found to be the Major Mode of HIV Transmission in a Group of Thai Fisherman”, he wrote “Aside from David Gisselquist being falsely cited in support of alternative AIDS theories, the response entitled "HIV in South Africa" (1) provides another curious example. A 1994 article by Caceres CF and van Griensven was used to support a theory that ONLY anogenital insertive intercourse and oroanal sex are HIV risk factors.” (italics ours)
Wrong. What Caceres and van Griensven wrote and we quoted was: “(1) unprotected anogenital receptive intercourse poses the highest risk for the sexual acquisition of HIV-1 infection; (2) anogenital insertive intercourse poses the highest risk for the sexual transmission of HIV-1 infection;… (5) no or no consistent risk for the acquisition of HIV-1 infection has been reported regarding other sexual practices such as anogenital insertive intercourse and oroanal sex”.
Tony Floyd misleads by using the word “Found” in his title, since the authors did not claim to have “found” but merely “suggest that heterosexual intercourse is the major mode of transmission in this population”. If Tony Floyd had read their paper rather than merely the abstract then he should have asked van Griensven the following questions:
· How is it possible that a sexually transmitted virus in gay men is only transmitted from the insertive to the passive partner but heterosexual Thai fisherman can get it from their passive partner?
· Why a test which is not good enough to prove HIV infection in Australia is good enough to prove HIV infection in poor Thai fishermen?
· How it is possible to claim proof for heterosexual transmission from a cross-sectional study? Especially when there are so many other risk factors.
We are very disappointed because it appears that Tony merely reads abstracts and then quotes from them out of context because he hasn’t taken the time to read the papers themselves.
Competing interests: None declared