A damning myth about the origins of HIV in North America spun out of a single “ambiguous oval,” according to the authors of a new genetic study on the virus.

The study, published today in Nature, uses reconstructed genetic sequences to show that the virus landed in the US around 1971, a full decade before AIDS was identified in 1981 and discovered to be caused by a retrovirus in 1983. And the man vilified for having delivered it to the United States, a French Canadian airline steward named Gaëtan Dugas, aka Patient Zero, had nothing to do with its arrival, the study authors report. In fact, Dugas’ moniker “Patient Zero” was actually a misinterpretation of the identifier “Patient O” used in a dataset for an AIDS cluster study centered in California. Patient O was meant to signify that he was a patient from Outside California.

In that early 1980s cluster study, researchers tracked down Dugas after several HIV/AIDS patients reporting have sex with him. The detective work allowed the researchers to link sexual activity with the virus’ spread. However, the study was published with the now infamous number rather than the letter, locking the misnomer into the scientific literature and history books.

“Although the authors of the cluster study repeatedly maintained that Patient 0 was probably not the ‘source’ of AIDS for the cluster or the wider US epidemic, many people have subsequently employed the term ‘patient zero’ to denote an original or primary case, and many still believe the story today,” wrote the authors of the new Nature study, led by Richard McKay, a medical historian at the University of Cambridge. Most notably, Randy Shilts identified Patient Zero by name in his 1987 book And the Band Played On and strongly insinuated the Dugas brought HIV to the US from Africa. Dugas died of AIDS in 1984.

To dispel the myth and clarify the history of HIV in the US, McKay and colleagues turned to thousands of archived blood samples collected during 1978 and 1979 from gay men in San Francisco and New York City as part of a hepatitis B virus study. They found that 6.6 percent of the New York samples tested and 3.7 percent of the San Francisco samples tested were positive for HIV.

The researchers next tried to decipher the genetic sequences of some of those HIV viruses. This was incredibly difficult since the viruses had degraded during long-term storage. To get around the problem, the researchers developed a new approach they called “jackhammering,” which allowed them to recover tiny fragments of genome that they could then piece together with overlapping code.

In the end, they were able to reconstruct the genomes of three HIV viruses from San Francisco and five from the Big Apple. Comparing those eight sequences to a database of others, the researchers found that they were most similar to strains circulating in the Caribbean. By clocking the evolution of the genetic sequences and the virus’ geographic spread, the researchers estimate that HIV arrived in the Caribbean from Africa around 1967, hopped from the Caribbean to New York City around 1971 (between 1969 and 1973), and landed in San Francisco by about 1976.

With that timeline, Dugas would have just been a teenager at the time HIV first arrived in the US, not yet a globe-trotting airline steward. The researchers added Dugas’ HIV genome sequence into their analysis and found it was typical of the viruses circulating in the US in the 1970s—not the root of strains that spread through the country.

“This individual was simply one of thousands infected before HIV/AIDs was recognized,” McKay said in a press conference. The study highlights how challenging—both ethically and scientifically—it is to pinpoint “Patient Zero.”

Nature, 2016. DOI: 10.1038/nature19827 (About DOIs).