Dear Editors,

On June 20th PLoS ONE published a study examining the association between HIV prevalence in the general population and proportion of women engaged in commercial sexual activity 1. The author made extensive use of data on the proportion of women who engage in sex work, which we had compiled in a publication 2. We feel the data in our paper were inappropriately used and we hereby wish to voice our concerns about this paper.

The paper by Talbott is an ecologic study. It’s main finding was “a fairly robust correlation between the number of commercial sex workers as a percentage of a country’s population and the HIV/AIDS prevalence rate for the country’s entire population”. At the same time the study did not support a protective role of male circumcision against HIV acquisition. While ecologic studies may be appealing there are major problems associated with this type of studies, including ecologic bias; problems related to the control for confounding; and lack of adequate data 3. Unfortunately Mr Talbott seems to ignore these problems and states that his study provides “strong” evidence. As it happens, the history of research on the association between risk of HIV infection and male circumcision is a textbook example of how the evidence for this association has been accumulating and becoming progressively stronger. The ecologic analysis by Bongaerts et al 4 generated the hypothesis that male circumcision is associated with a reduced risk in men of acquiring HIV infection through heterosexual intercourse. This hypothesis was subsequently tested and confirmed by a series of individual level risk factor analyses that allowed controlling for confounding by sexual behaviour 5. Finally, the strongest evidence for a protective role of male circumcision in heterosexual men was provided by three randomised trials that have been published over the past few years 6,7,8 . So, the “evidence” the paper by Talbott presents against the role of male circumcision in the spread of HIV infection, has already been surpassed by much better evidence provided by descriptive epidemiological research and experimental studies.

Moreover, the study is seriously flawed because the data on male circumcision and on the proportion of women who engage in sex work, are crude, incomplete and of questionable reliability. This obviously puts into question the validity of the results of the analysis. For the variable “male circumcision” a proxy was used, i.e. the proportion of men in the population who are Muslim. However, in sub-Saharan Africa many populations traditionally practice male circumcision, regardless of whether they are Muslim or not. The variable “proportion of women who are commercial sex workers” was extracted from our publication. This publication was part of a series of publications in a supplement of Sexually Transmitted Infections entitled “Improved methods and tools for HIV/AIDS estimates and projections”. The objective of the publication was to try and provide an estimate of the numbers of commercial sex workers in different regions in the world, in order to try and refine the estimates of the number of people in the world who are infected with HIV. We were very careful to discuss all the problems that arise when one tries to estimate numbers of sex workers, starting with the problem of the definition of “commercial sex worker”. But these subtleties were apparently lost to Mr Talbott. Based on incomplete data from less than 60 countries in the world he boldly concludes that “on average Africa has more than four times as many CSW’s as the rest of the world…”. We can not agree with such a sweeping statement, simply because there is too much uncertainty about the estimates that are available and we conclude our paper by the recommendation that “more efforts should be made …to obtain reliable estimates of the population size of these vulnerable women…” 2.

In conclusion this paper does not add anything to our understanding of the dynamics of the spread of HIV. But one wonders whether that is Mr Talbott’s primary concern. As president of “Africans against AIDS” he positions himself as an activist with a strong opinion on what needs to be done in order to stem the spread of HIV in sub-Saharan Africa. While we agree with him that we can do better on interventions targeting sex workers (and their clients), we are very concerned about some of Mr Talbott’s propositions and we take exception to statements such as: “a working prostitute in an HIV/AIDS infected country has the same wanton disregard for human life (as a drunk driver)” 9. Working with sex workers in Kinshasa (Democratic Republic of Congo), Abidjan (Ivory Coast), Cotonou (Bénin), Kisumu (Kenya) and Karnataka State (India) has taught us that sex workers eagerly adopt prevention interventions 10,11,12…but on condition that one approaches and respects them as a human being.

Anne Buvé (Institute of Tropical Medicine, Antwerp, Belgium), Michel Alary (Université Laval, Québec, Canada), Judith Vandepitte (MRC/UVRI Uganda Research Unit on AIDS , Entebbe, Uganda)

1. Talbott J. Size matters: the number of prostitutes and the global HIV/AIDS pandemic. PloS One 2007 (http://www.plosone.org/ar...).
2. Vandepitte J, Lyerla R, Dallabetta G, Crabbe F, Alary M, Buvé A. Estimates of the number of female sex workers in different regions of the world. Sex Transm Infect 2006; 82 (Suppl 3): iii18-25.
3. Morgenstern H: Ecologic studies, in Rothman KJ, Greenland S (eds): Modern Epidemiology, 2nd ed. Philadelphia, Lippincott-Raven Publishers, 1998: pp 459-480.
4. Bongaarts J, Reining P, Way P, Conant F. The relationship between male circumcision and HIV infection in African populations. AIDS 1989; 3: 373-377.
5. Weiss HA, Quigley MA, Hayes RJ. Male circumcision and risk of HIV infection in sub-Saharan Africa: a systematic review and meta-analysis. AIDS 2000; 14: 2361-2370.
6. Auvert B, Taljaard D, Lagarde E, Sobngwi-Tambekou J, Sitta R, Puren A. Randomized, controlled intervention trial of male circumcision for reduction of HIV infection risk: The ANRS 1265 trial. PloS Med 2005; 2(11): e298.
7. Bailey RC, Moses S, Parker CB, et al. Male circumcision for HIV prevention in young men in Kisumu, Kenya: a randomised controlled trial. Lancet 2007; 369: 643–56.
8. Gray RH, Kigozi G, Serwadda D, et al. Male circumcision for HIV prevention in men in Rakai, Uganda: a randomised trial. Lancet 2007; 369: 657–66.
9. http://www.africansagains... (Accessed on 5th July 2007 at 6pm).
10. Laga M, Alary M, Nzila N, et al. Condom promotion, sexually transmitted diseases treatment, and declining incidence of HIV-1 infection in female Zairian sex workers. Lancet. 1994;344:246-8.
11. Ghys PD, Diallo MO, Ettiègne-Traoré V, et al. Increase in condom use and decline in HIV and sexually transmitted diseases among female sex workers in Abidjan, Cote d'Ivoire, 1991-1998. AIDS 2002, 16:251-258.
12. Alary M, Mukenge-Tshibaka L, Bernier F, et al. Decline in the prevalence of HIV and sexually transmitted diseases among female sex workers in Cotonou, Benin, 1993-1999. AIDS 2002, 16:463-470.