An article by Justine Alford.
"Earlier work found that the common ancestor of group M emerged between 1884 and 1924, having jumped from a chimpanzee into a human living in south eastern Cameroon. This was likely from a hunter or butcher coming into contact with infected blood. The virus then probably circulated locally before making its way to Kinshasa around 1920.
From here, the virus began to rapidly spread thanks to the construction of a new railway that not only attracted large numbers of workers to the area but also allowed infected people to reach other major cities in central Africa. By the end of the 1940s, over one million people were travelling through Kinshasa on this railway each year, which helped establish secondary transmission regions.
During this time, another group of viruses, group O, was spreading in Cameroon at similar rates, but after the 1960s group M began to explode. The researchers think this was likely due to DRC achieving independence in 1960, an event that was coupled with huge social and cultural changes. The sex industry flourished and public health campaigns unfortunately led to the use of contaminated needles, allowing HIV to spread like wildfire. While the researchers can’t rule out the possibility that viral differences were key to the success of group M, they think that it’s more likely a case of “right place, right time.”
