Gene study clears 'Patient Zero' as cause of US HIV epidemic

Genes taken from archived blood samples show the U.S. AIDS epidemic started in New York in the early 1970s, definitively debunking the long-held belief that the virus was spread in the early 1980s by a flight attendant who became vilified as "Patient Zero" for seeding the U.S. outbreak.

Scientists have long suspected that HIV had been circulating in the United States for a decade before the first few AIDS cases were identified in Los Angeles 1981. The new study, published in the journal Nature, offers some of the first genetic proof.

"What we've done here is tried to get at the origins of the first cases of AIDS that were ever noticed," said Michael Worobey, the evolutionary biologist at the University of Arizona who led the study.

Using a painstaking new approach, Worobey and colleagues pieced together the entire genetic sequence of the HIV virus from eight archived blood samples taken in 1978 and 1979 from gay and bisexual men participating in a hepatitis B study.

The team traced genetic changes in the virus samples taken from male patients in New York and San Francisco. The researchers found that the HIV virus first jumped from the Caribbean to New York City around 1970, triggering the North American epidemic.

The team used the same approach to extract the full HIV genetic code from "Patient Zero," a flight attendant identified as Gaetan Dugas in the Randy Shilts 1987 bestseller "And the Band Played On."

Shilts, who wrote his book after Dugas had died, identified him as playing a key role in spreading the virus; media accounts painted him as a villain. The new study, however, found no biological evidence suggesting Dugas was the primary cause of the HIV epidemic in North America.

Dugas was first associated with the epidemic through a study by the U.S. Centers for Disease Control and Prevention that connected AIDS to sexual transmission of the disease in a cluster of 40 homosexual men.

In the study, Dugas was identified as "Patient O" because he was from outside of California, where the outbreak was believed to have started. That letter "O" was later mistaken for the number "0" and Dugas eventually became known as "Patient Zero," meaning the first patient infected in an epidemic.

"This individual was simply one of thousands infected before HIV was recognized," study co-author Richard McKay, a medical historian at the University of Cambridge, told reporters in a telephone briefing.

Worobey said the technique developed to extract and restore HIV genes from old blood samples borrows from technology used to identify ancient DNA.

Once they had the genetic code, the team evaluated the mutations made by the virus as it copied itself. This allowed the team to build an HIV family tree. Worobey believes a chimp first infected a human in Africa in the early 20th century. The virus that caused the U.S. 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, Worobey said. The virus spread to a large number of people "many years before AIDS was noticed," he said.

The team believes the virus arrived in San Francisco in 1975. The first five cases of AIDS were identified in California 1981, and they were first attributed to HIV in 1984.

"Our analysis shows that the outbreaks in California that first caused people to ring the alarm bells and led to the discovery of AIDS were really just offshoots of the earlier outbreak in New York City," Worobey said.

(Reporting by Julie Steenhuysen; Editing by David Gregorio)