Adéu a Nihil Obstat | Hola a The Catalan Analyst

Després de 13 anys d'escriure en aquest bloc pràcticament sense interrumpció, avui el dono per clausurat. Això no vol dir que m'hagi jubilat de la xarxa, sinó que he passat el relleu a un altra bloc que segueix la mateixa línia del Nihil Obstat. Es tracta del bloc The Catalan Analyst i del compte de Twitter del mateix nom: @CatalanAnalyst Us recomano que els seguiu.

Moltes gràcies a tots per haver-me seguit amb tanta fidelitat durant tots aquests anys.

dilluns, 30 de març de 2009

Esl 10 mites sobre la Sida

A la revista científica "The Lancet", gens sospitosa de conservadurisme o de vinculacions vaticanes, James D Shelton va publicar el desembre del 2007 un article de lectura imprescindible titulat "Deu mites i una veritat sobre la Sida". Un article de gran actualitat després de l'absurda nova polèmica provocada per les paraules del Papa sobre els preservatius. Una polèmica entre fanàtics del condó i de l'anticondó que ignora el que diu la ciència. Publico l'article sencer perquè només és accessible per a subscriptors.

Despite substantial progress against AIDS worldwide, we are still losing ground. The number of new infections continues to dwarf the numbers who start antiretroviral therapy in developing countries.1, 2 Most infections occur in widespread or generalised epidemics in heterosexuals in just a few countries in southern and eastern Africa. Although HIV incidence has fallen in Uganda, Kenya, and Zimbabwe, the generalised epidemic rages on. Something is not working. Ten misconceptions impede prevention.

1) HIV spreads like wildfire—Typically it does not. HIV is very infectious in the first weeks when virus levels are high,3 but not in the subsequent many-year quiescent phase. Only about 8% of people whose primary heterosexual partners have the virus become infected each year.4 Thus Kenya has more couples in which only one person is infected than couples in which both are (figure).5 This low infectiousness in heterosexual relationships partly explains why HIV has spared most of the world’s populations. However, the exceptional generalised epidemics in Africa seem largely driven by concurrent partnerships, in which some people have more than one regular partner. This pattern allows rapid dissemination when a new infection is introduced6 and probably involves more frequent risky sex than in sporadic or exclusive relationships.

2) Sex work is the problem—Formal sex work is uncommon in these generalised epidemics. In Lesotho, fewer than 2% of men reported paying for sex in the previous year, although 29% reported multiple partners.7 Nuanced economic support is an important enabler of regular concurrent partnerships and transactional sex, but the targeting of sex work in prevention campaigns has limited usefulness.

3)Men are the problem—The behaviour of men, including cross-generational and coercive sex, contributes substantially to the establishment of generalised epidemics. But a heterosexual epidemic requires some women to have multiple partners.3 The importance of women in generalised epidemics is evidenced by the high proportion (sometimes the majority) of discordant couples in which the woman, not the man, is HIV positive (figure).5

4)Adolescents are the problem—Generalised epidemics span all reproductive ages. Although adolescent women are affected through sex with older men, HIV incidence increases in women in their 20s and later in life.8 Men are infected at even older ages. Thus interventions in young people, including abstinence, although important, have limited usefulness.

5)Poverty and discrimination are the problem—These factors can surely engender risky sex. But HIV is paradoxically more common in wealthier people than in poorer people, perhaps because wealth and mobility support concurrent sexual partnerships.9 Moreover, HIV has declined without major improvements in poverty and discrimination, notably in Zimbabwe (notwithstanding substantial economic and social distress).

6) Condoms are the answer—Condom use, especially by sex workers, is crucial to the containment of concentrated epidemics, and condoms help to protect some individuals. But condoms alone have limited impact in generalised epidemics. Many people dislike using them (especially in regular relationships), protection is imperfect, use is often irregular, and condoms seem to foster disinhibition, in which people engage in risky sex either with condoms or with the intention of using condoms.8

7) HIV testing is the answer—That learning one’s HIV status (hopefully with counselling) should lead to behavioural change and reduced risk seems intuitive. However, real-world evidence of such change is discouraging, especially for the large majority who test negative.3 Moreover any changes must be sustained for years. And very newly infected people, who are highly infectious, do not yet test HIV-positive.

8)Treatment is the answer—Theoretically, treatment and counselling might aid prevention by lowering viral levels (and infectiousness) in those treated, reducing denial about HIV, and promoting behavioural change. However, no clear effect has emerged. Indeed these salutary effects might be outweighed by negative effects, such as resumption of sexual activity once those on antiretrovirals feel well, and disinhibition when people realise that HIV might no longer be a death sentence.

9) New technology is the answer—Many resources are devoted to vaccines, microbicides, and prophylactic antiretrovirals. Unfortunately any success appears to be far off. Moreover, such innovations might be mainly targeted only at very high-risk populations, rely on behavioural compliance, and engender disinhibition.10 Similarly, treatment of sexually transmitted infections to prevent HIV has been disappointing.11 Even male circumcision, an already available, unmistakably effective, and compelling priority will take years to have additional substantial effect.

10) Sexual behaviour will not change—Actually, facing the prospect of deadly illness, many people will change. Homosexual men in the USA radically changed behaviour in the 1980s. And the reductions in HIV incidence in Kenya and eastern Zimbabwe were accompanied by large drops in multiple partners,8, 12 probably largely as a spontaneous reaction to fear.

Truthfully, our priority must be on the key driver of generalised epidemics—concurrent partnerships. Although many people sense that multiple partners are risky, they do not realise the particular risk of concurrent partnerships. Indeed, technical appreciation of their role is recent.6 But partner limitation has also been neglected because of the culture wars between advocates of condoms and advocates of abstinence, because it smacks of moralising, because mass behavioural change is alien to most medical professionals, and because of the competing priorities of HIV programmes.

Fortunately we can enhance partner-limitation behaviour, akin to the behaviour change that many people have adopted spontaneously. State-of-the-art behaviour-change techniques, including explicit messages, that are sensitive to local cultures, can raise perception of personalised risk. Even modest reductions in concurrent partnerships could substantially dampen the epidemic dynamic. Other prevention approaches also have merit, but they can be much more effective in conjunction with partner-limitation. Now, more than 20 years into HIV prevention, we have to get it right.

I thank Daniel Halperin and Willard Cates for helpful ideas on this Comment. My views here are not necessarily those of USAID. I declare that I have no conflict of interest.


1 UNAIDS, WHO. AIDS epidemic update. (accessed Nov 21, 2007).
2 World Health Organization, UNAIDS, UNICEF. Towards universal access: scaling up priority HIV/AIDS interventions in the health sector. Progress report, April 2007. (accessed Nov 21, 2007).
3 Cassell MM, Surdo A. Testing the limits of case finding for HIV prevention. Lancet Infect Dis 2007; 7: 491-495. Summary | Full Text | PDF(115KB) | CrossRef | PubMed
4 Wawer MJ, Gray RH, Sewankambo NK, et al. Rates of HIV-1 transmission per coital act by stage of HIV-1 infection, in Rakai, Uganda. J Infect Dis 2005; 191: 1403-1409. CrossRef | PubMed
5 Central Bureau of Statistics, Ministry of Health Kenya, Kenya Medical Research Institute, Centers for Disease Control and Prevention Kenya, ORC Macro. Kenya demographic and health survey 2003. (accessed Nov 21, 2007).
6 Halperin D, Epstein H. Concurrent sexual partnerships help to explain Africa’s high level of HIV prevalence: implications for prevention. Lancet 2004; 364: 4-6. Full Text | PDF(92KB) | CrossRef | PubMed
7 Ministry of Health and Social Welfare Lesotho, Bureau of Statistics Lesotho, ORC Macro. Lesotho demographic and health survey 2004. (accessed Nov 21, 2007).
8 Shelton JD. Confessions of a condom lover. Lancet 2006; 368: 1947-1949. Full Text | PDF(65KB) | CrossRef | PubMed
9 Shelton JD, Cassell MM, Adetunji J. Is poverty or wealth at the root of HIV?. Lancet 2005; 366: 1057-1058. Full Text | PDF(46KB) | CrossRef | PubMed
10 Imrie J, Elford J, Kippax S, Hart G. Biomedical HIV prevention—and social science. Lancet 2007; 370: 10-11. Full Text | PDF(49KB) | CrossRef | PubMed
11 Gray RH, Wawer MJ. Randomized trials of HIV prevention. Lancet 2007; 370: 200-201. Full Text | PDF(49KB) | CrossRef | PubMed
12 Gregson S, Garnett GP, Nyamukapa CA, et al. HIV decline associated with behavior change in eastern Zimbabwe. Science 2006; 311: 664-666. CrossRef | PubMed
a Bureau for Global Health, US Agency for International Development, Washington, DC 20523, USA