Aids 'dates from 1930s'

Aids has hit generations around the world from Romania...

An international group of scientists has said evidence suggests Aids first appeared 70 years ago - and not in the 1950s as previously thought.

US and UK scientists used a supercomputer to analyse genes of the human immunodeficiency virus, HIV, which leads to Aids.

In a paper in the journal Science, they explain that they used rates of genetic mutation to work out that the virus probably appeared in 1931.

... to Cambodia...

This early date is even more remarkable, given that HIV was not even recognised less than 20 years ago.

Researchers speculate that it may have been transmitted from apes to humans near the turn of the century and remained isolated in a small population until the 1930s.

Alternatively the virus might have jumped over to humans in about 1930 and started spreading immediately, or a decade or two later.

Constant rate

Research to determine the virus's ancestry was based on a "molecular clock" analysis of variations of certain HIV genes.

... to Uganda: Some African countries could see a 20% drop in their workforces due to Aids

Since genes mutate at a constant rate over time, it was possible to work back using this information and estimate when the main group of strains split off from a common origin.

Researchers led by Bette Korba, from Los Alamos National Laboratory, New Mexico, said this probably happened between 1915 and 1941 and gave 1931 as the most likely year.

Contradiction

One common theory holds that HIV emerged through polio vaccination programmes in Central Africa between 1957 and 1960.

It was thought that polio vaccines may have been grown in kidney cell cultures derived from chimpanzees kept at a research facility near Stanleyville, now Kisangani in the Democratic Republic of Congo.

But the new theory would appear to contradict that.

"Our analyses suggest that the HIV-1 M [main] group ancestral sequence occurred decades before the vaccination programmes and that the diverse subtypes were well established by 1957," said the researchers.

Aids was not identified as a clinical condition until 1981, but retrospective studies have revealed cases dating back to the 1970s.

New figures from the International Labour Organisation suggest that the Aids pandemic is so serious throughout Africa that in the next two decades it will lead to a 20% drop in the workforce of some countries.