The question of exactly where the transfer of HIV

Where?

The question of exactly where the transfer of HIV to humans took place, and where the 'epidemic' officially first developed has always been controversial. Some have suggested that it is dangerous to even try to find out, as AIDS has frequently been blamed on an innocent person or group of individuals in the past. However, scientists remain keen to find the true origin of HIV, as most agree it is important to understand the virus and its epidemiology in order to fight it.

So did it definitely come from Africa?

Given the evidence we have already looked at, it seems highly likely that Africa was indeed the continent where the transfer of HIV to humans first occurred (monkeys from Asia and South America have never been found to have SIVs that could cause HIV in humans). In May 2006, the same group of researchers who first identified the Pan troglodytes troglodytes strain of SIVcpz, announced that they had narrowed down the location of this particular strain to wild chimpanzees found in the forests of Southern Cameroon¹⁹. By analysing 599 samples of chimp droppings (P. T. troglodytes are a highly endangered and thus protected species that cannot be killed or captured for testing), the researchers were able to obtain 34 specimens that reacted to a standard HIV DNA test, 12 of which gave results that were virtually indistinguishable from the reactions created by human HIV. The researchers therefore concluded that the chimpanzees found in this area were highly likely the origin of both the pandemic Group M of HIV-1 and of the far rarer Group N. The exact origins of Group O however remain unknown.

HIV Group N principally affects people living in South-central Cameroon, so it is not difficult to see how this outbreak started. Group M, the group that has caused the worldwide pandemic, was however first identified in Kinshasa, in the Democratic Republic of Congo. It is not entirely clear how it transferred from Cameroon to Kinshasa, but the most likely explanation is that an infected individual travelled south down the Sangha river that runs through Southern Cameroon to the River Congo and then on to Kinshasa, where the Group M epidemic probably began.

Just as we do not know exactly who spread the virus from Cameroon to Kinshasa, how the virus spread from Africa to America is also not entirely clear. However, recent evidence suggests that the virus may have arrived via the Caribbean island of Haiti.