The cause of "HIV" has never been established with absolute certainty.
The cause of HIV is HIV since HIV is not a disease it is a virus. HIV stands for human immunodeficiency virus previously known as human T-cell leukemia/lymphoma virus type 3.
Just because the AMA touts something does not make it fact. Historically many known "facts" are ultimately proven false. The earth was flat--until it was round. Doctors ridiculed and drove out of their profession the original physicians who advocated washing hands to reduce cross contaminations between patients.
And people used to think illness was punishment from the Gods. But this has since been proven false, as has the flat earth hypothesis and liver flushing. But there are still people to this day that believe diseases are God's punishment for sinning, that the earth is flat (The Flat Earth Society) and that liver flushing cleanses the liver.