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[YAOUNDÉ] Research in Cameroon has confirmed what scientists have suspected for some years: that wild chimpanzees are the source of the human HIV/AIDS pandemic.

The finding, published today (26 May) in Science, is based on an analysis of chimpanzee faeces found in forests in the south of the country.

Researchers led by Beatrice Hahn of the University of Alabama at Birmingham, United States, found evidence of a virus called SIVcpzPtt in the chimpanzee subspecies Pan troglodytes troglodytes. Until now the virus has only been found in captive apes.

In some wild populations studied, as many as 35 per cent of the animals were infected with SIVcpzPtt. The virus is HIV's closest known relative but is not known to cause disease in chimpanzees.

By analysing the genetic make-up of the newly identified chimpanzee viruses, the researchers concluded that today's human AIDS epidemic was sparked by a single transmission of SIVcpzPtt from a chimpanzee to a human, probably in the early 20th century.

Hahn's teams says that SIVcpzPtt also jumped between a chimpanzee and a human on two other occasions to give rise to two rare forms of HIV known as N and O.

Type N has only been found in 12 patients in Cameroon, says co-researcher Paul Sharp from the University of Nottingham, United Kingdom. Type O is also rare and mainly found in patients in Cameroon, Gabon and surrounding countries.

Hahn points out that people get HIV from other people and not from chimpanzees, but says exposure to SIVcpzPtt in chimpanzee blood should be avoided.

"We hope to eventually learn why HIV is so pathogenic in people, while its chimpanzee precursor is not pathogenic for its natural host," Hahn told SciDev.Net. "We hope this will help the people in Cameroon and people with HIV infection worldwide."

The researchers say their study shows that endangered primates can be studied non-invasively, which may help in the future with other emerging infections in other parts of the world.

Link to full paper in Science*

Reference: Science Express doi 10.1126/science.1126531 (2006)

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