Our primate relatives harbour diseases that can spread to humans through the foodchain. Credit: © Alamy.com

Hunting and butchering of bushmeat is infecting people in Central Africa with a new virus, scientists say. The virus hasn't caused illness in those infected, but its spread hints that future pandemics might follow HIV out of the jungle.

The same practice of hunting and eating animals such as monkeys and chimpanzees is thought to have sparked the HIV pandemic, when animal forms called SIV crossed into humans. But researchers do not know what other viruses these animals harbour, or whether they are being passed to people.

To get a handle on this, a team of researchers from the United States and Cameroon studied simian foamy virus, which is endemic in wild primates but does not cause them disease. They examined the blood of nearly 1,100 people from nine separate villages for signs of infection with the virus, and report their findings in The Lancet1.

Ten people carried antibodies to simian foamy virus in their blood, suggesting they had been exposed to it. And at least three picked up the virus from separate animals - a gorilla, a mandrill and a type of monkey called a De Brazza's guenon - based on comparison of viral DNA sequences in their blood with those from the animals.

"Now we're forced to think these viruses are infecting humans on a much more frequent basis," says study leader Nathan Wolfe of Johns Hopkins University in Baltimore, Maryland.

The researchers do not know if simian foamy virus has the potential to cause disease in humans. None of those showing signs of infection were ill, but the team do not know if different strains of the virus could spread from person to person or prove more deadly, as certain strains of SIV proved to be in humans.

Jungle fever

The study strengthens calls to curb the trade in bushmeat, says Beatrice Hahn of the University of Alabama in Birmingham, who studies the evolution of HIV. Politicians, public-health officials and local inhabitants need to work out ways to provide communities with alternative means of sustenance and income, she says: "You can't just go over there and say 'don't do it'."

HIV is thought to have crossed into humans from other primates many times over, eventually taking root some 50-100 years ago and spawning today's pandemic. Wild primates are also suspected of triggering Ebola outbreaks and an infection called HTLV that can cause leukaemia.

Wolfe's study shows that viruses pass to humans frequently and pins it convincingly on contact with bushmeat. All the individuals who showed signs of infection said they had hunted and killed wild primates or kept them as pets. "That was the 'eureka' moment," Wolfe says. "It allows us to clearly nail where it came from."

In order to predict the next disease to surface from the African jungle, experts are keen to identify other viruses already leaping into humans and work out which might pose a threat. Wolfe is now analysing the same human samples for signs of other wild primate viruses.