Scientists have discovered a gorilla strain of HIV in a Cameroonian woman.
The HIV-1 strain, which is responsible for most human HIV infections, came from a chimpanzee virus called Simian Immunodeficiency Virus (SIV) . It is believed it was transferred to humans who came into contact with infected bush meat.
The Health Protection Agency estimates that, in the UK, up to 10,000 gay men have HIV without knowing, with one in four men infected with the virus unaware of their HIV status.
This is the first time the strain present in gorillas has been found in a human, Nature Medicine reports.
The 62-year-old woman is currently living in Paris but previously lived in a semi-rural area of Cameroon.
Doctors noticed discrepancies in her routine viral load tests and subsequently found the virus was more closely related to SIV from gorillas rather than HIV.
She did not come into contact with gorillas or bush meat and it is thought she came into contact with someone carrying the virus.
Researchers say they expect to find more people carrying that particular strain.
Study co-author Dr David Robertson, from the University of Manchester, told the BBC that this is the first definitive transfer of HIV from a source other than chimpanzees.
He said: “This demonstrates that HIV evolution is an ongoing process.
“The virus can jump from species to species, from primate to primate, and that includes us; pathogens have been with us for millions of years and routinely switch host species.”
Dr Robertson added that the emergence of the new strain is not thought to pose any new problems.
“If some day we do manage to develop a vaccine, there’s no reason to believe it wouldn’t work,” he said.
“There’s no reason to believe this virus will present any new problems, as it were, that we don’t already face.”