Study adds 50 years to HIV history

New Delhi, Oct. 2: A lymph-node tissue biopsy from 1960 suggests that HIV began spreading among humans in the 19th century, perhaps 100 years before AIDS was recognised in the early 1980s.

An international research team recovered fragments of HIV genes from a lymph-node tissue collected from a woman in Kinshasa, Congo, 48 years ago and compared it with genes from the oldest HIV sample known from 1959 – also from Kinshasa.

The scientists found that the two virus samples – from 1959 and 1960 – were genetically so different that any common ancestor would have had to be several decades older, that is, it would have existed around 1900.

However, the researchers also found that the 1900 virus itself would have been genetically different from the original virus that spread from chimpanzees to humans – and that it would have taken several years for this genetic divergence to take place.

G.S.Mudur, for The Telegraph

Therefore, the study, which appeared in the journal Nature today, suggests that HIV may have begun spreading among humans as early as 1884, and 1900 was the probable time of the origin of a strain that scientists have named HIV-1 group M. Till now, it was believed that HIV began spreading among humans around 1930.

"The picture that has emerged is how changes the human population experienced may have opened the door to the spread of HIV," biologist Michael Worobey, lead author of the study at the University of Arizona, Tucson, said.

The new estimated time of origin coincides with the rise of urban centres in west-central Africa where HIV emerged.

Researchers believe the growth of cities in the region between the 1880s and 1920s, and the associated high-risk behaviours, may have allowed the virus to flourish.

Previous research had shown that HIV spread from chimpanzees to humans in south-eastern Cameroon. Worobey believes the resulting epidemic among humans parallels the growth of urban centres in the region.

The genetic diversity of the 1959 and 1960 virus samples suggests a large number of people in the region had already been infected by 1960. American and European doctors began to recognise AIDS as a new, distinct illness only in 1981, and HIV was isolated by French biologist Luc Montagnier and Robert Gallo in 1983-84.

"Understanding the genetic history of HIV and how it has evolved gives scientists a level of insight into how the virus may mutate in the future," said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in the US.

"This understanding can help researchers develop new treatment or prevention approaches that might be effective in the long term," Fauci said.

The 1959 and 1960 samples – both from Kinshasa – are the oldest links to the HIV epidemic, Worobey said. The next oldest specimens have been recovered from the tissues of patients from the 1970s and 1980s.

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