SUNDAY, Aug. 2 (HealthDay News) -- For the first time, researchers have found evidence that the AIDS virus traveled from gorilla to human, another confirmation that the disease continues to evolve even as scientists race to vanquish it.
French scientists reported Sunday that a woman in the West African country of Cameroon carried a strain of the AIDS virus that is closely related to a similar virus found in gorillas.
It's not yet clear whether this strain of HIV, the virus that causes AIDS, is common among humans or whether it's especially dangerous.
"Findings like these remind us that primates continue to transmit viruses to humans just as they did before we knew about AIDS," said Rowena Johnston, vice president of research with the Foundation for AIDS Research (AmFAR) in New York City. "HIV continues to broadside us from directions we do not necessarily expect."
Previously, scientists had believed that HIV mainly made its way to humans via chimpanzees, Johnston said. A kind of monkey known as a sooty mangabey is also thought to have transmitted the disease.
The virus could have been passed through blood as people ate bushmeat -- meat from wild animals -- or prepared it.
But the Cameroonian woman appears to have a strain that originated in a gorilla, according to the report in the Aug. 2 online issue of Nature Medicine.
The 62-year-old woman, diagnosed with HIV in 2004, hasn't developed the symptoms of AIDS even though she's not being treated with medications. She lives in Paris, where she moved from Cameroon.
The study author was not available for comment. Johnston, who is familiar with the findings, said the woman may have been infected via sexual contact with someone who hunted gorillas, or she could have gotten the disease by having contact with gorilla meat. Or it could have been transmitted through several people before reaching her.
It's not clear how long the strain has been in existence, but the research suggests that it has made it through several "rounds" of infection, Johnston said.
"The jury is still out as to whether this is bad news relative to strains of HIV that are already circulating," she said. "We just can't draw those kinds of conclusions from one person."
The woman's case is unusual, however, and that fact may be revealing, said Dr. Philip R. Johnson, an AIDS specialist and chief scientific officer at Children's Hospital of Philadelphia.
The level of virus in the woman's body is high but she doesn't appear to have symptoms, potentially suggesting that the strain isn't strong, he said.
In the big picture, it's possible that the disease didn't pass directly from gorillas to humans, but instead took another route, Johnson added.
"More cases will need to be found. The key is that [researchers] now have the tools to look [for them]," he said.
It's possible, he said, that scientists missed similar cases in the past because testing technology couldn't detect them.
Find out more about HIV/AIDS at the U.S. Centers for Disease Control and Prevention.
SOURCES: Rowena Johnston, Ph.D., vice president, research, Foundation for AIDS Research, New York City; Philip R. Johnson, M.D., chief scientific officer, Children's Hospital of Philadelphia, and professor, pediatrics, University of Pennsylvania School of Medicine, Philadelphia; Aug. 2, 2009, Nature Medicine, online