HIV Origins: Virus Arrived in United States from Haiti in 1969

A new study, published in Proceedings of the National Academy of Sciences, sheds new light on old issue: how did the HIV started in the United States? It came from Haiti, researchers say.

Michael Worobey, an assistant professor of ecology and evolutionary biology at The University of Arizona in Tucson, and colleagues investigated how the HIV got to the US. Their study titled ""The emergence of HIV/AIDS in the Americas and beyond," shows that the virus HIV that caused the epidemic of AIDS in The United States came (with a high degree of probability) from Haiti in or around 1969, a lot earlier of what was thought until today.

Previous thought on HIV spreading the US was that the epidemic of AIDS started in California in earlier 1980s. The new discovery by Worobey changes completely what has been known as the "Patient Zero" theory.

Previous research on AIDS done by the US Centers for Disease Control and Prevention (CDC) suggested that AIDS in the US spread in from one man in California who was dubbed as Patient O (Oh), for "Out of California."

Worobey and colleagues took archived blood samples of 5 early HIV patients to reveal the date of HIV arrival to the United States. All these 5 early HIV patients came from Haiti and had recently migrated to the United States. In addition of these 5 early HIV Haitian patients around 100 more blood samples obtained worldwide from earlier HIV patients were also analyzed. All these early sample contained a strain of HIV known as subtype B.

Researchers used a technique used in evolutionary biology that utilizes complex statistical formulae to construct a tree. It is some how like building your ancestry tree but on a bigger scale.

From these complex analysis (known as Bayesian Markov Monte Carlo phylogenetic analysis, Bayesian MCMC method, and Bayesian molecular clock method, among others) a tree can be built that traces the origin of HIV spreading in the US and beyond. This what Worobey and Colleagues did.