Recent research questioning whether most AIDS in Africa is spread through sex, which was reported in Discover last month, has prompted a rebuttal from evolutionary biologist Edward Holmes of the University of Oxford. He argues that if HIV in Africa is transmitted mainly through contaminated medical needles and transfusions—as anthropologist David Gisselquist claims—then it ought to spread in a fashion similar to that of another blood-borne virus, hepatitis C. When Holmes and his colleagues tracked the incidence of hepatitis C and HIV, however, they found remarkably different patterns. In South Africa, HIV infection rates rose from less than 1 percent of all adults in 1990 to almost 25 percent in 2000. Over the same period, the prevalence of hepatitis C remained steady at around 1 percent, although hepatitis C is more readily spread through contaminated blood.
"We tested one particular aspect of their model—and it failed that test," Holmes says. ...
