The origins of HIV/AIDS can now be traced

The origins of HIV/AIDS can now be traced back at least 32,000 years to African monkeys infected with a precursor to the virus, scientists report. The mystery is how that precursor persisted for centuries and posed relatively little risk to humans before evolving into the virus that causes AIDS and now afflicts more than 33 million people worldwide.

The latest findings, published this week in Science, come out of a study, led by Tulane University's National Primate Research Center and the University of Arizona, involving 79 monkeys from the African island of Bioko, which split from the mainland 10,000 years ago.

Fayez Nureldine, AFP / Getty Images

A 1983 study on macaque monkeys infected with simian immunodeficiency virus helped establish the link between SIV and HIV.

Monkeys from four species on the island were infected with simian immunodeficiency virus (SIV). The viral strains infecting the monkeys were similar to those in the same species on the African continent, which indicates that the virus existed before the island and the mainland parted.

In other words, the HIV precursor is older than 10,000 years and probably existed somewhere between 32,000 and 75,000 years ago, based on how quickly it mutated in subsequent computer-based lab tests.

Earlier attempts at tracking the evolution of HIV had pegged the virus at a few hundred years old. But "that just didn't seem right," Dr. Beatrice Hahn, a virologist at the University of Alabama, told The New York Times.