Scientists Track Time and Place of HIV's Arrival
Monday, November 5, 2007
In the decades since young gay men in the United States started dying from a mysterious syndrome in the 1980s, scientists have wondered how and when the AIDS virus arrived. Many scenarios have been proposed, including one early but now-discounted theory that the disease was imported by a promiscuous Canadian flight attendant dubbed "patient zero."
Now, however, scientists reconstructing the genetic evolution of the deadly virus say they have traced its true path -- concluding that the insidious pathogen used Haiti as a steppingstone from Africa to the United States and arrived much earlier than had been thought. It then simmered silently here for more than a decade before it was detected, beginning its global spread along the way.
"This is the first time that we've been able to bring together the geographical picture with the timing picture to show with a pretty high degree of certainty where the virus went from Africa, and when," said Michael Worobey, a professor of ecology and evolutionary biology at the University of Arizona in Tucson, who led the research.
Others praised the detailed genetic analysis of human immunodeficiency virus (HIV) from around the world as an impressive bit of biomedical sleuthing.
"For those of us who have been interested in HIV evolution and the origins of the virus, this is very interesting," said Beatrice H. Hahn, a professor of medicine at the University of Alabama in Birmingham. "It's a very nice piece of work."
In addition to writing a key chapter in the history of the AIDS pandemic, the new insights into the genetic variability of the virus could aid the long-frustrated efforts to develop an effective vaccine.
"What this might tell us is how the virus might evolve molecularly," said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases. "That might have an impact on the virus that you put in your vaccines. So this not only has historical value but practical implications for vaccine design."
The new work fills in the latest piece of the puzzle of the origins of the AIDS pandemic. Hahn and her colleagues had previously established that HIV originally jumped from chimpanzees to humans, possibly when hunters in Africa butchered animals infected with a version of the virus. In 2000, Bette Korber of Los Alamos National Laboratory and her colleagues found that the virus began to proliferate in Africans around 1930.
But the exact route the virus took as it crept out of Africa before exploding in other parts of the world has been the subject of intense debate and speculation.
"We know that the virus has a deep history in Africa," Worobey said. "I wanted to find out how it emerged from Africa and became the pandemic that we know today."
Worobey started by retrieving six blood samples from cold storage at the federal Centers for Disease Control and Prevention in Atlanta. Arthur E. Pitchenik of the University of Miami had collected them in 1982 and 1983 from Haitian immigrants who had died from a mysterious syndrome, later determined to be AIDS.
"We now know that these are samples from several of the earliest Haitian AIDS patients in the United States," Worobey said.