Sunday, February 6, 2011
AIDS and concurrency
Two very big, and related, questions we did not address this week are why is AIDS such a massive problem in Africa and why is AIDS largely a heterosexual disease in Africa?
One theory for this relates back to the sexual partner networks I showed you. It turns out that if you have say 3 sexual partners in a year it makes a big difference to disease transmission if you have these partners serially (ie one after the other) or concurrently (ie with some overlap).
One theory for the difference between Africa and other countries such as the US is that sexual partner networks in Africa may tend to have more concurrency even when the mean, and frequency distribution of sexual partners is not that different to the US.
This theory, as you might imagine because it involves topics of race, sexuality and perceived morality, is far from universally accepted but there are a number of papers supporting it and Helen Epstein's book, The Invisible Cure: Africa, the West, and the Fight Against AIDS, puts together a strong case for this theory and the implications of it for best dealing with AIDS in Africa.
She charges that Western governments and philanthropists, though well-meaning, have been wholly misguided, and that Africans themselves, who understand their own cultures, often know best how to address HIV in their communities. Most significant is Epstein's discussion of concurrent sexual relations in Africa. Africans often engage in two or three long-term concurrent relationships—which proves more conducive to the spread of AIDS than Western-style promiscuity. Persuade Africans to forgo concurrency for monogamy, and the infection rate plummets, as it did in Uganda in the mid-1990s. On the other hand, ad campaigns focused on condom use helped imply falsely that only prostitutes and truck drivers get AIDS.
Others disagree with Epstein: Concurrent sexual partnerships do not explain the HIV epidemics in Africa: a systematic review of the evidence. The debate is likely to continue. This is more than just an academic debate since it potentially affects how billions of dollars of aid are spent in Africa.