Scientists using genetically-sequenced blood samples from people infected by HIV have exonerated the man known as “patient zero,” who was blamed for setting off the AIDS epidemic.

A genetic analysis of stored blood samples found that HIV came to the U.S. from a pre-existing epidemic in the Caribbean, which arrived in New York in the early 1970s and then spread westward a few years later, after infecting people in the city. Among the samples analyzed, one belonged to Gaëtan Dugas, a Canadian flight attendant who became known as ‘Patient Zero,’ in the book chronicling the AIDS epidemic And the Band Played On.

Researchers from the University of Arizona found that blood belonging to Dugas, who was long thought the source of the outbreak in North America, contained a viral strain of HIV already infecting men in New York before he visited gay bars in the city while working for Air Canada in 1974.

“We…found neither biological nor historical evidence that he was the primary case in the U.S.,” the researchers wrote in the study, published Wednesday in the journal Nature.

According to the researchers, Dugas was not originally referred to as ‘Patient Zero’; early studies of HIV called him ‘Patient O’ to signify that he was from “outside Southern California,” where the study originated. The ‘O’ was later misread as a zero, making it seem as though Dugas originated the epidemic, since ‘Patient Zero’ is commonly used to indicate the initial case in an outbreak.

 

This article originally appeared on Time.com.