03/28/2008 02:45 am ET Updated May 25, 2011

Scientists Pinpoint HIV's Arrival In US

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 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 decade before it was detected, beginning its global spread along the way.

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