UPDATE: The research written about below was published October 26, 2016, in Nature; for related news, read “Guess What: AIDS ‘Patient Zero’ Was No Zero.”

A genetic study of blood samples taken from the 1970s gives a clearer picture of how the epidemic unfolded in the United States, and the results further disprove the idea that a single person—a sexually voracious “Patient Zero”—spread the virus across America.

The findings were presented at the 2016 Conference on Retroviruses and Opportunistic Infections (CROI) in Boston.

Researchers led by evolutionary biologist Michael Worobey, PhD, of the University of Arizona in Tucson looked at blood samples taken from gay and bisexual men in 1978 and 1979 as part of a hepatitis B study. They also looked at a blood sample taken from a Canadian flight attendant named Gaëtan Dugas, a.k.a. Patient Zero.

A 1987 book by Randy Shilts about the AIDS epidemic, And the Band Played On, had identified Dugas as the “Typhoid Mary” of AIDS in North America, a myth that took hold in the public’s mind. In fact, as POZ reported earlier, it wasn’t until the 2013 book Plane Queer: Labor, Sexuality, and AIDS in the History of Male Flight Attendants that Shilt’s then-editor Michael Denneny admitted that Patient Zero was cooked up to boost sales.

Worobey’s research offers further proof to debunk the myth. Looking at the blood samples, they created a family tree of the virus. Degas fell in the middle of the tree, not at the beginning.

The genetic snapshot showed that HIV likely moved from Africa to the Caribbean by 1967 before then moving to New York City by 1971, and from there another single virus moved to San Francisco around 1975. In New York City, the virus spread enough to exhibit genetic diversity by the end of the 1970s.

“In the context of these insights into the early spread of HIV/AIDS in North America,” write the researchers in their abstract, “the genesis and persistence of beliefs about ‘Patient 0’…are unsupported by scientific data.”

Below, you can watch a clip of Dugas speaking at a 1983 AIDS community event in Vancouver. The video is part the “30 30 Campaign,” created in 2013 to celebrate the 30th anniversary and HIV history of AIDS Vancouver.