A new mutated version of the swine flu that can infect humans has been discovered in pigs in China.

Chinese researchers said the "G4" strain of the H1N1 virus had all the hallmarks of a candidate to be a pandemic virus.

Pig farm workers had elevated levels of the virus in their blood and scientists called for close monitoring of swine industry workers right away.

The study underlines of risks of viruses crossing species barriers into humans especially in densely populated regions like China.

A Chinese foreign ministry spokesman said the government is closely following developments and will take all measures to prevent the spread of any virus.

The researchers studied the virus in pigs from 2011 to 2018.

The study was published in the U.S. journal, "Proceedings of the national academy of sciences" .

The current coronavirus pandemic is believed to have originated in horseshoe bats in southwest China and could have spread to humans in a seafood market in Wuhan, where the virus was first identified.