The human immunodeficiency virus (HIV) has infected 75 million people, since the pathogen was transmitted from great apes to humans. AIDS has rightly been seen as one of the most devastating diseases to have adapted to human hosts.
However, the how, where and when of its emergence have not been studied extensively. It is this gap that a collaboration of scientists from the universities of Oxford and Louvain as well as a team of IRD researchers aimed to fill with their recent study published in Science magazine.
Chimpanzees from South Cameroon had previously been identified as potential originators of HIV, and indeed there have been known cases of human contamination by these great apes, yet only one of them must have led to the global AIDS pandemic that is with us today.
By using genome sequencing and the latest phylogeographic techniques to study viruses collected in the areas surrounding the Congo Basin, the researchers were able to determine that the disease emerged around the year 1920 in Kinshasa, the capital city of what is currently the Democratic Republic of Congo.
Once the geographical location where the virus originated was established, the scientists could tie this new knowledge to the historical events of the period. The archives kept by Belgian settlers on the former colony Zaire reveal that there was an important trade route between South-East Cameroon and the Congolese capital with goods such as ivory and rubber transported by river. It is probably due to this arrangement made at the beginning of the twentieth century that the epidemic broke out in Kinshasa rather than the areas where human contamination by infected chimpanzees had in fact occurred.
Between 1920 and 1950 Kinshasa was one of the most urbanized and connected cities in Central Africa. As a result of advances in railway transportation, over a million people would pass the Congolese capital each year on their way to other parts of the country or the continent by the end of the 1940s. All of this contributed to the rapid spread of HIV, which was only exacerbated by certain social practices in place after the 1960s, such as the rise in prostitution and non-sterile needle use in hospitals.