GENETICISTS have pinpointed the origin of the Aids virus to the turn of the 20th century, decades earlier than it was previously believed to have emerged.
Human tissue samples from Africa show that the most pervasive global strain, HIV-1, probably jumped from chimpanzees to humans some time between 1884 and 1924, with the best estimate being 1908. Scientists previously believed the virus originated in
around 1930.
Research published today in the journal Nature suggests the rise of large cities in west-central Africa was a major factor in the spread of the virus. The first major settlements were founded by European colonialists in the late 1800s, but populations did not start to exceed 10,000 until after 1910.
Key to the work was the discovery of an infected lymph node specimen, taken in 1960 from a woman in Leopoldville in the Belgian Congo, now Kinshasa, the capital of the Democratic Republic of the Congo.
It is the world's second-oldest genetic sequence of HIV and was compared by scientists with dozens of other previously known samples to build up a "family tree" for the viral strain, confirming a common ancestor existed around 1900.
Professor Michael Worobey, of Arizona University, last year with his colleagues showed that a similar sub-type of HIV probably arose from a single strain that was carried from Africa to Haiti, before spreading to the United States and onwards.
He said: "I would bet that cities, and the high-risk sexual behaviours found in them, are necessary to allow one of these sporadic viral jumps to get a toehold in the human population."
Professor Paul Sharp, of Edinburgh University's Institute of Evolutionary Biology, said: "The interpretation that HIV-1 was spreading among humans for 60 to 80 years before Aids was recognised should come as no surprise.
"If the epidemic grew roughly exponentially from only one or a few infected individuals around 1910 to the more than 55 million estimated to have been infected by 2007, there were probably only a few thousand HIV-infected individuals by 1960, all of them in central Africa."
The sample was recovered from the 1958-62 archives of the Department of Anatomy and Pathology at the University of Kinshasa. The boxes were transferred to the University of Arizona, where eight lymph node, nine liver and ten placenta samples from 1958-60 were selected for HIV screening. It is hoped that more HIV-1-infected specimens in the archival banks of west central African hospitals can help scientists to trace the evolution of Aids viruses.
The full article contains 433 words and appears in The Scotsman newspaper.
