Simian Immuno Deficiency Virus?

Question

Human Immunodeficiency Virus originated in the chimpanzee's of cameroon as S.I.V., But how did it pass on to humans as H.I.V.?

Answer 1

HIV originated in primates as far as is known. Possible ways for this virus to have originally infected humans include the hunting and eating of the original primate species; a bite would be another possible route. From this point, the virus ultimately spread to the rest of the world.

If a cross species jump is indeed the origin of HIV then the following conditions would most likely be required:
a large human population,
a large nearby population of a host animal,
a pathogen that eventually mutates to spread from animal to human,
interaction between the species to transmit enough of it to humans to establish a human foothold, which may take millions of individual exposures,
a mutation of same pathogen that can spread from human to human,
some method that allows the pathogen to disperse widely so it does not "burn out" in a local population of humans.

Such requirements existed in the remote past with smallpox, and also with the 20th century Spanish Flu.

Two species of HIV infect humans: HIV-1 and HIV-2. HIV-1 is more virulent and more easily transmitted. HIV-1 is the source of the majority of HIV infections throughout the world, while HIV-2 is less easily transmitted and is largely confined to West Africa.

Both species of the virus (HIV-1 and HIV-2) are believed to have originated in West-Central Africa and jumped species (zoonosis) from primates to humans. HIV-1 evolved from a Simian Immunodeficiency Virus (SIVcpz) found in the chimpanzee subspecies Pan troglodytes troglodytes. DNA sequencing indicates that HIV-1 (group M) entered the human population in the early 20th century, probably sometime between 1915 and 1941. HIV-2 crossed species from a different strain of SIV, this one found in sooty mangabeys (an Old World monkey) of Guinea-Bissau.

Answer 2

It is thought that HIV may have originated in Africa. Tissue samples form the 1950s is what got researchers excited. Bites are the most likely scenario for transmission or perhaps there was some voodoo rituals, possibly tribal rituals involving the blood of monkeys.