

A genetic mutation found mostly in people of African descent appears to increase their HIV infection risks by 40 percent.

But how far does this go towards explaining the African AIDS epidemic? Not far at all – though some journalists spun it otherwise.

The findings were published yesterday in Cell Host and Microbe, and my Wired Science post is here. In addition to epidemiology – a long-term analysis of 1,200 HIV-positive U.S. Air Force members – there's a convincing cell-level hypothesis: the mutation prevents red blood cells from blocking HIV's hunt for white blood cells. I felt perfectly comfortable writing about that.

But the researchers also surmised that, as around 90 percent of Africans have the mutation, it accounts for 11% of sub-Saharan Africa's AIDS burden. This angle made me uneasy – partly because it's a very preliminary study on which to base such a broad extrapolation, but mostly because it'd be easy to overstate the mutation's importance.

Seen in the wrong light, the numbers could present Africa's AIDS tragedy as a biological inevitability. Several press accounts do exactly that. The New York Times credits the mutation for "explaining why the disease is more common there than expected." Reuters says it could "help explain why AIDS has hit Africa harder than all other parts of the world," as this can't be fully rooted in "sexual behavior and other social factors." The Guardian says it "may go some way" to explaining the African prevalence of AIDS. And the Gene Expression blog titles its coverage, "Evolution, a reason for the African HIV epidemic?"

Not that the genetics of AIDS in Africa should be ignored. But let's put these findings in perspective: the World Health Organization estimates that 6.1 percent of adult sub-Saharan Africans are HIV-positive. Shave that 6.1 percent by one-tenth – the cases apparently attributable to the mutation – and it's still ten times higher than the 0.5 percent HIV infection rate of North America and western Europe. And when rates drop to 3% in Angola but jump to 20% or more in its neighbors, genes are the last place to start looking for clues.

To be fair, the study's authors themselves weren't at fault. Robin Weiss, a University College, London virologist, said the findings showed that "HIV rates in Africa aren't just the product of culture and behavior," but was quick to emphasize the continuing importance of drugs and counseling. If only everyone were so careful.

Images: Sign courtesy of Jon Rawlinson; map of African HIV rates from WikiMedia, derived from circa-2000 UNAIDS data.

Note: On the plus side, credit to the Times of London and HealthDay News for solid coverage.*

See Also:

WiSci 2.0: Brandon Keim's Twitter and Del.icio.us feeds; Wired Science on Facebook.