HIV’s Patient Zero Who Wasn’t

Publish date:
Social count:

A new study finds HIV came to New York around 1971 via Haiti, then spread to San Francisco around 1976—and Patient Zero wasn’t to blame.

By Nathan Collins


HIV assembling on the surface of an infected macrophage. (Photo: Wikimedia Commons)

You’ve probably heard the alleged story about how HIV first arrived in the United States: It was Gaëtan Dugas, a Canadian flight attendant, later dubbed Patient Zero, who supposedly brought the disease from Europe and spread it from coast to coast. Long a dubious claim, that myth may finally be put to rest: Researchers writing in Nature report new evidence that HIV arrived in New York City from the Caribbean around 1971—one year before Dugas’ first sexual encounter in the U.S.—then diversified and spread to San Francisco around 1976.

Apart from providing some of the best evidence to date on how HIV arrived in and spread throughout the U.S., the study is also a reminder of the dangers of focusing too much on the idea of a patient zero, says Richard McKay, a science historian at the University of Cambridge and co-author of the new study. Dugas “was simply one of thousands infected before HIV/AIDS was recognized,” McKay told reporters Tuesday morning.

But if it wasn’t Dugas, how did HIV arrive in the U.S., and how did it spread? A 2007 genetic analysis led by University of Arizona evolutionary biologist Michael Worobey strongly suggested that the type of HIV most common in the U.S.—known as HIV-1 group M, subtype B—moved from Africa to Haiti in the mid-1960s, then came to America in the late ’60s or early ’70s. Exactly how it spread within the U.S. is less clear, because researchers didn’t at the time have contemporary data on the HIV genome in the U.S.

Researchers report new evidence that HIV arrived in New York City from the Caribbean around 1971 — one year before Dugas’ first sexual encounter in the U.S.

That changed when Worobey—the new study’s lead author—McKay, and their colleagues discovered blood samples from New York and San Francisco, originally collected in 1978 and 1979 as part of research on hepatitis B in men who have sex with men. Although time had left its mark on those samples, the team eventually recovered full HIV virus gene sequences from three men in San Francisco and five in New York.

An analysis of those samples revealed close similarities to HIV-1 strains typically found in Caribbean nations. Based on how those strains have subsequently evolved, the researchers estimate the Caribbean subtype B strains most likely arrived in the U.S. in 1971, give or take two years. Further analysis of HIV’s evolution in the U.S. suggested that New York HIV strains were already genetically diverse by 1979, meaning that the virus had a good amount of time to evolve into a number of different strains. Based on that observation, the researchers estimate the virus had probably made it to New York by about 1972.

The San Francisco samples, meanwhile, were substantially less diverse. Most likely, the researchers found, those cases originated with a New York strain introduced to San Francisco around 1976.

“You see a very tell-tale pattern of extensive genetic diversity in New York City, suggesting that New York City was the key hub of diversification for the virus, and restricted genetic diversity in San Francisco, suggesting San Francisco was a later dispersal out of this New York City hub,” Worobey says.

Meanwhile, several different factors contributed to Dugas’ infamy—most bizarrely, the misreading of an “O,” which originally stood for “outside of California,” as a zero in an early study of HIV/AIDS. (Some of the first cases of what would come to be called AIDS were identified in Los Angeles.) The flight attendant’s unusually lucid sexual history and, as McKay put it, our general desire to “seek reassurance, to cast blame, or to satisfy curiosity” also helped develop the impression Dugas was responsible for the epidemic.

And therein lies a warning: “One of the dangers of focusing on a single patient zero when discussing the early phases of an epidemic is that we risk obscuring important structural factors that might contribute to its development: poverty, legal and cultural inequalities, barriers to health care and education,” McKay said. “These important determinants risk being overlooked if we focus too readily on a patient zero.”