AIDS found to originate from heavy "poppers" (highly toxic nitrite inhalant drug) usage among male homosexual community and the disease is NOT contagious. This has been known since 1981 - but was totally suppressed by the powers-that-be.
SOURCE: America's Frontline Doctors
I think that’s too narrow a cause, even if it’s one factor, but it’s better than a ‘virus’ that materialised out of nowhere the blink of an eye ago in human history.