Early start: The progenitor to HIV may have jumped from chimps to humans as early as 1884 a new study shows.
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Colonial spread
In other words, the ancestral virus began to be transmitted among humans at the start of the century – the estimated range is between 1884 and 1924.
The virus spread only very slowly at first, but got a vital foothold thanks to urbanisation during the colonial era, the authors speculate. It was transmitted through sex and then was taken further afield through commerce.
"The founding of and growth of colonial administrative and trading centres such as Kinshasa may have enabled the region to become the epicentre of the HIV/AIDS pandemic," they suggest.
Kinshasa was founded in 1881, Brazzaville (capital of today's Republic of Congo) in 1883 and Yaounde (Cameroun) in 1890, while Bangui (Central African Republic) was established in 1899.
All of these towns were founded before or at around the time that HIV-1 is believed to have entered the human population, the investigators note. The growth of these towns was at first slow. Until 1910, not one of them had a population of more than 10,000 people.
There are several theories that seek to explain how SIV leapt to humans. They hypothesise that an infected chimpanzee bit a human, or a SIV-infected ape was butchered and sold for bushmeat, and the virus entered the bloodstream through tiny cuts in the hand.
