A quick search on google will reveal a conspiracy that states HIV origins was made-man at Fort Detrick, Maryland or unintentionally injected into "high risk groups" during an 1974 Hepatitis B trials vaccination program done by the NIH geared toward gay men, injected drug users, some health care workers and prison workers.

Some state that HIV is a hybrid virus or recombinant meaning two seperate viruses superinfected the same cell and recombined RNA strands into a new hybrid virus. They reason HIV cannot be traced due to theory and the evolution which has taken place. This can easily be done in chicken embryos which are the standard for reproducing live virus.

The National Institute of Health(N.I.H) did infact derive early polio vaccinations from monkeys and also derived the early experimental Hep B vaccinations from internal monkey organs such as the liver which is known to be filled with SIV in alot of wild green african monkeys.

I would put my money on conspiracy theory #2 which is the HEP B vaccination program/early polio that explains why certain groups were the first to show signs of infections. This is an accidental theory as we weren't aware of SIV at the time and might have made a recombinant virus even.

Hunter theories and others exist but doesn't properly explain the patterns of infection.