The HIV virus may have originated from wild chimpanzees living in South Cameroon, researchers claim.

An international team, including scientists from the Universities of Nottingham, Montpellier and Alabama, has discovered a crucial missing link in the search for the origin of HIV, the virus responsible for human AIDs.

That missing link is the origin of the virus, which the team found to be in wild-living chimpanzees in southern Cameroon with SIVcpz (Simian Immunodeficiency Virus), which is similar to HIV.

The findings, released yesterday, will be published in an upcoming issue of Science magazine.

Although researchers have long known that some chimpanzees are infected with the SIVcpz virus, only a few captive apes had been found to harbour it.

In collaboration with the Project Prevention du Sida au Cameroun (PRESICA) in Cameroon, researchers from Montpellier and Alabama analysed ape faecal samples collected by trackers from the forest floor in remote jungle regions of Cameroon.

They detected SIVcpz in 35% of chimpanzees in some communities.

The University of Alabama team, headed by Dr Beatrice Hahn, went on to determine the genetic sequences of the chimpanzee viruses.

All of the data was then sent to The University of Nottingham for evolutionary analysis, which revealed the extremely close genetic relationship between some of the new chimpanzee virus samples and strains of HIV.

The Chimpanzees in south-east Cameroon were found to have the viruses most similar to the form of HIV that has spread throughout the world.

Paul Sharp, professor of genetics at the University of Nottingham said: “Particularly when you consider that HIV probably originated more than 75 years ago, it is most unlikely that there are any viruses out there that will prove to be more closely related to the human virus; thus, the initial jump of a virus from a chimpanzee to a human probably occurred in that region.”

As well as finding the origin of the virus, the research paves the way for future work exploring the natural history and behaviour of SIVcpz.

Despite its close relationship to the HIV virus, the researchers discovered that SIVcpz does not cause any AIDS-like illness in chimpanzees.

Professor Sharp said: “We’re currently working to understand which genetic differences between SIVcpz and HIV-1 evolved as a response to the species jump.”

Yusef Azad, Director of Policy and Campaigns at the National AIDS Trust said: “This research is interesting as all discoveries which relate to the history and origins of HIV could be of value to the vital work being carried out by scientists in developing a HIV vaccine.”

According to a World AIDS Day report last year by EuroHIV, who monitor figures for the whole of Europe, the United Kingdom has seen the largest increase in HIV cases in any country in Western Europe in the last four years.

The number of reported cases increased by 69% in the United Kingdom, but just by 20% overall in the remaining 10 countries in Western Europe that compile reliable HIV figures.