AIDS and Networks

The origin of the Aids pandemic has been localized to a single source, a colonial-era city then called Leopoldville which became, as Kinshasa, the biggest urban center in Central Africa and a bustling focus for trade, including a market in wild “bush meat” captured from the nearby forests.

A genetic analysis of thousands of individual viruses has confirmed beyond reasonable doubt that HIV first emerged in Kinshasa, the capital of the Belgian Congo, in about 1920 from where it spread via the colonial railway network to other parts of central Africa.
The study, based on analyzing the subtle genetic differences between various subtypes of HIV, found the human virus had evolved from a simian virus infecting chimps which were hunted for food by people who had probably carried HIV with them into Kinshasa.
"Commercial sex workers" (aka "whores") and the re-use of dirty syringes, aided the transmission of the virus which was also carried to distant parts of the Congo by the millions of passengers who used the newly-built railway network.
Independence in 1960 helped the virus to “break out” from small groups of infected people into the wider population, including immigrant workers from Haiti who then carried their infection back home from where it would eventually be transmitted to visitors from the US.