To investigate, he and his team traversed Cameroon's back roads by Jeep and on foot, collecting blood from hunters and their prey. Lab analysis of viral DNA extracted from the hunters' blood samples confirmed his hypothesis: Multiple nonhuman viruses were present, including a number of previously undiscovered viruses from the same family as HIV. One of these, HTLV-3, has a known counterpart in nonhuman primates, and Wolfe's team thinks another, HTLV-4, probably has a simian analogue too. Not all viruses have epidemic potential. But one that has a high mutation rate could spread quickly, first infecting members of a hunter's family, then people in nearby towns and beyond. "Nathan's work has important implications for predicting where emerging diseases could occur," says Don Burke, one of Wolfe's Johns Hopkins colleagues.