A new flu virus found in Chinese pigs has become more infectious to humans and needs to be watched closely in case it becomes a potential "pandemic virus", a study showed, although experts said there is no imminent threat.

A team of Chinese researchers looked at influenza viruses found in pigs from 2011 to 2018 and found a "G4" strain of H1N1 that has "all the essential hallmarks of a candidate pandemic virus", according to the paper, published by the US journal, Proceedings of the National Academy of Sciences (PNAS).