Researchers in China have discovered a new type of swine flu that is capable of triggering a pandemic, according to a study in the US science journal PNAS.

Named G4, it is genetically descended from the H1N1 strain that caused a pandemic in 2009.

It emerged recently and is carried by pigs, but can infect humans, they say.

It possesses “all the essential hallmarks of being highly adapted to infect humans”, the authors said.

“It is of concern that human infection of G4 virus will further human adaptation and increase the risk of a human pandemic,” the researchers wrote.