HIV Arrived in U.S. From Haiti 10 Years Earlier Than Previously Believed, Study Says

October 31, 2007

The most widespread HIV subtype outside Africa likely emerged in Haiti in the 1960s and arrived in the U.S. a few years later -- about 10 years earlier than previously believed -- according to a study published Tuesday in the Proceedings of the National Academy of Sciences, the Los Angeles Times reports.

For the study, Michael Worobey, an evolutionary biologist at the University of Arizona, and colleagues analyzed five blood samples collected in 1982 and 1983 from Haitian HIV/AIDS patients in Miami that had been frozen and stored by CDC (Chong, Los Angeles Times, 10/30). In addition, the researches examined genetic data from 117 early HIV/AIDS patients worldwide (Dunham, Reuters, 10/29). The researchers examined two viral genes and compared their sequences with viruses found worldwide, using HIV samples from Central Africa considered to be some of the earliest forms of HIV as a baseline.

The researchers then constructed a timeline of HIV development by measuring how much the genes in recent blood samples differed from early samples. According to the study, samples from Haitians were genetically the most similar to the African virus, indicating the Haitian viruses were among the earliest to branch off. The researchers found a 99.7% certainty that HIV subtype B originated in Haiti, Worobey said.

Worobey concluded that the virus was brought to Haiti by Haitians who traveled to the Democratic Republic of Congo after it became independent in 1960. He added that the virus was then carried to the U.S. by Haitian immigrants between 1966 and 1972 (Los Angeles Times, 10/30). The researchers believe an unknown Haitian immigrant likely arrived in a large U.S. city, such as New York or Miami, and the virus circulated in the U.S. population and then to other nations before it was discovered. The mutation timeline of the virus presented in the study places the virus in the U.S. about 12 years before the disease was recognized by scientists in 1981, Reuters reports (Reuters, 10/29).

The study's findings confirm many scientists' suspicions that the virus was imported to the U.S. from Haiti and subsequently spread to Australia, Canada, Europe and Japan, AFP/Yahoo! News reports. HIV/AIDS prevalence among Haitians living in the U.S. was 27 times higher than in the broader U.S. population in the early days of the U.S. epidemic, according to AFP/Yahoo! News. In addition, the researchers concluded that HIV spread from Haiti to Trinidad and Tobago, fueling the Caribbean epidemic (AFP/Yahoo! News, 10/29).

"Once the virus got to the U.S., then it just moved explosively around the world," Worobey said (AFP/Yahoo! News, 10/29). Worobey added that there likely were "hundreds of thousands of infections" before HIV was discovered. Arthur Pitchenik, a study co-author from the University of Miami, said the study "gives [scientists] more clear insight into the history of" the HIV/AIDS pandemic and "what path the virus took" (Reuters, 10/29).

Worobey added that the study did a "good job of settling the debate" over whether the virus arrived in the U.S. from Africa or Haiti. "This shows quite clearly that the data is really only consistent with a Haiti-first origin," Worobey said. Beatrice Hahn, a virologist at the University of Alabama-Birmingham who was not involved with the study, said the study's "calculations are as good as the currently available methods allow." Hahn cautioned against blaming the spread of HIV/AIDS on Haitians or Central Africans. "These viruses are fairly clever, and they have to survive. They will find niches. ... You realize chance events play a very important role," Hahn said (Los Angeles Times, 10/30).

The Miami Herald on Wednesday examined how the study's findings have "stoked controversy among researchers and Haitians" by "reopening deep wounds over the medical community's role in perpetuating a stigma against people from the island" (Tasker/Charles, Miami Herald, 10/31).

NPR's "Day to Day" on Tuesday included a discussion with NPR science correspondent Richard Knox about the study (Brand, "Day to Day," NPR, 10/30). Audio of the segment is available online.

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