AIDS originated from the human immunodeficiency virus (HIV), which is believed to have come from non-human primates in West-central Africa. Specifically, HIV-1, the main cause of the global AIDS pandemic, is thought to have originated from a simian immunodeficiency virus (SIV) found in chimpanzees in southern Cameroon. The virus crossed over to humans likely through exposure to infected blood during hunting or butchering of chimpanzees (bushmeat activities). This cross-species transmission is estimated to have happened in the early 20th century, possibly around the 1920s in Kinshasa (then Leopoldville) in the Democratic Republic of the Congo. HIV then spread undetected for decades before AIDS was first recognized in the early 1980s.

Summary:

• HIV-1 originated from SIV in chimpanzees in West-central Africa (Cameroon).
• Transmission to humans likely occurred through hunting/butchering activities.
• The earliest human infection dates back to around the 1920s in Kinshasa.
• AIDS was first identified as a disease in the early 1980s.