This article appears in the Witness section of the Winter 2016 issue of the New Humanist. Subscribe today.

Gaetan Dugas is one of the most demonised patients in medical history. A gay Canadian flight attendant, he was an HIV patient and Aids activist who for many years was known as Patient Zero.

A study published in the American Journal of Medicine in 1984 traced many early HIV infections to an unnamed gay male flight attendant. Dugas was named – and prominently featured – in the 1987 book And the Band Played On, which documented the outbreak of the Aids pandemic in the US. Author Randy Shilts portrays Dugas as reckless, allegedly intentionally infecting or at least recklessly endangering hundreds of others with the virus. The book does not claim that Dugas was the principal disseminator of the virus, but the theory became widespread.

Now, a new study in the journal Nature has shown that Dugas was one of thousands of infected people in the 1970s. Aids was only recognised in 1981 when unusual symptoms began to appear in gay men in Los Angeles; but scientists have long suspected that HIV had been circulating in the US for a decade before these first few cases were identified.In the study, researchers from the University of Arizona looked back further by analysing stored blood samples – some of which contained HIV – from 1970s hepatitis trials. Using a new method which borrows from technology used to identify ancient DNA, they reconstructed the genetic code of the virus in those patients, and screened 2,000 samples from New York and San Francisco. After this, scientists could build a “family tree” of HIV and trace when it arrived in the US.

Michael Worobey, the evolutionary biologist at the University of Arizona who led the study, said he believes that the virus that caused the US epidemic emerged from Africa in the mid-to-late 1960s, and caused an outbreak in Haiti and other Caribbean countries. In 1970 or 1971, this strain hopped from Haiti to New York, making the city a hub of transmission. The virus spread to a large number of people, many years before Aids was noticed.

After building this family tree, the researchers then analysed the genetic code of HIV taken from Dugas’s blood. The results showed that the virus in his blood was not the “father” of the US epidemic. This conclusively shows that Dugas, who died in 1984 of kidney failure caused by an Aids-related infection, was not Patient Zero after all.