The Cold War contained a lot of ignominious events for all how participated in it. One of them lingers in conspiracy theories to this day. There was a conspiracy involved — just not the ones the theorist generally believe in.
During the Cold War, the USSR started a disinformation campaign that blamed the creation of AIDS on the CIA. This particular campaign, although given a title of its own — Operation Infektion — wasn't really a standalone idea. Both the U.S. and the USSR had spent years flinging biological warfare conspiracy theories at each other. It was hard for the public on either side to separate the fact from the fiction. When AIDS came along, that too became ammunition.
The first accusation was published in 1983. The Indian paper Patriot printed a letter from an "anonymous U.S. official." It both accused the United States of developing the virus in a CIA lab, and stated that the lab researching the virus would be moved to Pakistan, India's political opponent. American officials believed the letter to be from the Soviet Union because it seemed to follow the form of other biological warfare accusations made by the USSR and because of some awkward phrases that didn't seem to come from a native English speaker.
The Patriot letter first raised the alarm, but the accusation stayed on the back burner until the AIDS crisis spread through the world, and the US lobbed a few more biological warfare accusations at the USSR. Now looking for credibility, the Soviet Union turned to East German doctors and scientists to give the idea academic credit. The most prominent among them was Dr Jakob Segal, a passionate Marxist believer and a scientist accomplished enough to explain the science of the AIDS virus. He was given biased information and wrote accordingly. He claimed that AIDS had first been identified, and first began to spread, in the United States. It likely originated there. When two CIA agents (some say they were two Soviet double-agents) showed up at Segal's house and interrogated him, he was even more convinced. He spoke out in papers and at conventions.
Once the accusation was established in countries outside Russia, Soviet propagandists started cranking out pamphlets inside Russia, disseminating the information. Working under the theory that enough repetition manufactured belief, they kept exposing people to the idea until it took root. Even the eventual collapse of the USSR, and the confessions of some of the people who had been in on the plot, did not change the perception. Segal believed that AIDS was manufactured by the CIA until his death. If anyone unearthed AIDS cases outside the United States prior to its spread inside the U.S., he accused them of lying.
Today the conspiracy theory, and different permutations of the theory, continue to percolate. One writer, Johannes Simmel, believed that the CIA spread the disease by first infecting homosexual prison inmates in San Francisco and New York. Some people believed, and still believe, that the method of infection was "AIDS-oiled condoms." This can, in some cases, drive down the rate of condom usage. It appears that disinformation not only outlives its own usefulness, but outlives even the government that creates it.