Genetic studies trace the pandemic strain of HIV to a chimpanzee virus that spread in colonial Kinshasa around 1920, carried along railways and rivers by trade and labor migration.
Contested history
Consensus: HIV-1 descends from a chimpanzee virus (SIVcpz) that crossed into humans in west-central Africa in the early 20th century and spread from Kinshasa.
Spillover through bushmeat hunting (cut hunter)Established
Viral genetics tie HIV-1 group M to chimpanzee SIV in southeastern Cameroon, and molecular clocks date the jump to roughly 1900 to 1920.
Created by the CIA or U.S. government labsDebunked
The virus was circulating decades before genetic engineering existed, and the claim was spread by the Soviet KGB's Operation INFEKTION in the 1980s.
Spread by contaminated oral polio vaccine in the 1950sDebunked
Tests of surviving vaccine stocks found no chimpanzee SIV, and molecular dating places HIV's origin decades before the vaccine trials.
Colonial medicine campaigns amplified early spreadDebated
Some researchers argue unsterile injections in colonial health campaigns helped the virus spread, but how much they mattered is uncertain.