Gorillas Missing Link in HIV Mystery

Scientists have discovered the origin of the third of three strains of HIV known to infect humans.

Of the three strains of HIV known to infect humans, two types - the one causing the global AIDS epidemic and another that has infected a small number of people in Cameroon - came from a chimpanzee virus called SIV, NewScientist.com reports. The source of the third strain, which infects people in western central Africa, was a mystery. Now we know it came from gorillas.

Scientists at the University of Montpelier in France have discovered the virus in the droppings of gorillas living in remote forests in Cameroon. The infected gorillas lived up to 400 kilometers apart, so the researchers think it must be a normal or endemic virus in the animals, as SIV is in chimps.

The next mystery is how the gorillas got it. The gorilla virus is descended from the chimp variety, but gorillas are vegetarian and rarely encounter chimps.

There is little mystery about how humans contracted the virus, though: local people picked it up hunting gorillas for food and traditional medicine. That means the virus could yet cross again and create another HIV strain, say the researchers, especially as growing demand for "bushmeat" leads to more hunting.