Actually, many species of non-human apes and monkeys are indeed affected by HIV or very similar viruses. It is generally thought that the human strain was transmitted from apes or monkeys to humans via contact with an ape or monkey with a bite or exposure to infected blood. The genetic similarity between humans and other species of apes would make it more likely that a strain of the virus could adapt to infect and be spread by a human.

So, indeed, it is very likely that the strains infecting non-human animals actually came first, and adapted into the human variety

Actually to the reality AIDS virus is infected to the humans from animals  like monkeys so Aids virus existed in african monkey which passed to the human generation