Patient Zero (also known as Gaetan Dugas), who is thought to be the source of the HIV outbreak, is one of the most controversial patients in history. However, scientists have cleared his name over two decades after his death.

In a new study published in Journal Nature, it was revealed that the homosexual flight attendant was just one of thousands of HIV-infected individuals back in the 1970s. New York was also described as a hub for the transmission of the disease.

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The researchers analyzed stored blood samples that were intended for hepatitis trials in the 1970s. They found out that some samples also tested positive for HIV. They used a new way of viral genetic code reconstruction for the infected individuals.

Through reconstruction, the team from the University of Arizona was able to gather information necessary to build an HIV family tree and trace the arrival of the virus in the United States.

The technique known as "RNA jackhammering" enables the selective copying of the RNA virus' tiny fragments and unit them together. Researchers spent four years developing it. Serum samples from men who had intercourse with same sex between 1978 and 1979 were also analyzed.

Researcher Dr. Michael Worobey stated that the "samples contain so much genetic diversity that they could not have originated in the late 1970s." He added that when they used the most precise dates on the tracking process, it revealed that the epidemic started in 1970 or 1971.

The blood of Patient Zero also confirmed that he was not the origin the U.S epidemic. The US Centers for Disease Control first named the employee of Air Canada as Patient O due to his "Out-of-California" case. Eventually, the letter "O" was changed to "0" thus making Dugas "Patient Zero."

Professor Oliver Pybus of University of Oxford said that "it makes a very interesting point about Patient Zero, who has become a talking point in the origins of AIDS, yet no matter how attractive a narrative is, it doesn't have any scientific basis and it's really unfortunate that this person was identified." The demonized patient died in 1984.

Worobey stressed that "no one should be blamed for the spread of a virus that no one even knew about." He added that it is still an open question on how the immunodeficiency virus moved from the Caribbean to other countries, particularly the U.S., back in the 1970s.

The viral infection was first recognized in 1981 among gay men manifesting unusual symptoms.