HIV-1 is a mutuation from SIV-1 (Simian Immunodeficiency Virus) a Chimpanzee virus.
Of course we know the virus has to enter the bloodstream; but, unfortunately, many thousands of those administered the oral dose were teething infants.
First concerned cases of AIDs were 1977, 20 years later. Central Africa was the point from which it spread to the rest of the world.
The resovoir was monkeys, but like ebola you caught it eating bush meat, or from scratches or bites. And it spread via truck drivers and men migrating to jobs where there were no wives, only prostitutes.
The River is one of many conspiracy theories out there. In the US They are harmless, but then the mullahs read them, forbid people from getting shots, and then kill the doctors giving medicine. And the kids die of course, but hey, the authors made their money so who cares.