Quote
If it is true that the HIV epidemic was caused by a single stupid vaccine producer using chimp serum then I would change that. But I have no clue if that is true.
There was a well supported hypohesis that the development of oral polio vaccine (OPV) could have played a role in the early propagation of the HIV epidemic. However, when supporting evidence was sought, it was not found. Now it is generally not thought to have played any role in the HIV epidemic.
The most accepted theory is that the precursor to HIV is a virus known as SIV that occurs in monkeys. HIV closer to that seen in humans has been documented in a particular (protected) chimpanzee population that feeds on SIV-infected monkeys. There are two common strains of SIV and it is believed they recombined within chimpanzees to form a virus closer to HIV. (It is possible that colonization and destruction of habitat caused migration of the chimpanzees and exposure to monkeys with different sorts of SIV)
It is likely that human hunters became infected with HIV from hunting chimpanzees. By estimating the changes in genetic patterns between the HIV found in chimpanzees and the first HIV infections in humans it is thought that HIV first crossed into humans somewhere betweeen 1915 and 1945. The first confirmed cases (from stored samples) were in West Africa in the late 1950s, USA in a teenager in the late 1960s and in Norway in the mid-70s.
Recently another retrovirus (SFV or simian foamy virus) has been shown to have spread from non-human primates to human hunters. (SFV doesnt cause serious illness in humans). This confirms that cross species transmission of retroviruses occurs.