The origins of AIDS: from patient zero to ground zero
- Correspondence to Dr Jacques Pépin, Department of Microbiology and Infectious Diseases, Université de Sherbrooke, CHUS, 3001, 12ème Avenue Nord, Sherbrooke, Qc J1H 5N4, Canada;
The HIV/AIDS pandemic has so far caused about 35 million deaths, while 34 million individuals currently live with HIV.1 ,2 Even if this will have no impact on the course of the epidemic, understanding the factors that allowed the successful emergence of HIV-1 is important, first as a moral obligation towards the victims, but also to draw lessons that could ultimately help mankind avoid facing similar threats in the future.
Over the last 12 years, much progress has been made in unravelling the complex chain of events that led to the worst pandemic of modern times. The source of HIV-1 group M (‘M’ for main) is the Pan troglodytes troglodytes chimpanzee of central Africa3 ,4 which inhabits southern Cameroon, Gabon, Equatorial Guinea, the Congo–Brazzaville, the southwest of the Central African Republic, the Cabinda enclave of Angola and a small part of the Democratic Republic of Congo north of the Congo river (figure 1). The true ‘Patient Zero’, the one who started the pandemic, must have lived somewhere within this territory. Sequencing evidence suggests that this may indeed have been in southeast Cameroon or the adjacent areas of the Central African Republic and Congo–Brazzaville. But after some local transmission to start with, HIV-1 eventually managed to flourish and diversify further down the Congo River.
Through sophisticated molecular clocks, it was estimated that the original cross-species transmission of HIV-1 group M, from chimp to man, occurred during the first three decades of the 20th century. By exclusion of other hypotheses, this initial event probably occurred through the manipulation of chimpanzee meat by a hunter or his wife, who manipulated the ape's carcass in order to cook it.1 Three other ‘groups’ of HIV-1 (groups …