The virus, which researchers call G4 EA H1N1, was detected through analysis of 30,000 nasal swabs taken from pigs at slaughterhouses in China.
It has been described as a blend of influenza found in European and Asian birds and the H1N1 virus, which is believed to have killed up to half a million people worldwide in 2009.
The inclusion of H1N1 genes suggests the virus could adapt to spread from human to human, according to a study published in the peer-reviewed scientific journal Proceedings of the National Academy of Science (PNAS) on Monday.
“G4 viruses have all the essential hallmarks of a candidate pandemic virus,” wrote the researchers from China Agricultural University.
Following a sharp increase in prevalence since 2016, the new strain is now “the predominant genotype in circulation in pigs detected across at least 10 provinces,” they add.
Testing of swine workers also revealed that over 10 per cent tested positive for antibodies to G4. “Such infectivity greatly enhances the opportunity for virus adaptation in humans and raises concerns for the possible generation of pandemic viruses,” the paper adds.
“Controlling the prevailing G4 EA H1N1 viruses in pigs and close monitoring in human populations, especially the workers in swine industry, should be urgently implemented.”
Experts said that the likelihood of the strain causing another pandemic was low but cautioned that vigilance was still needed.
“Influenza can surprise us,” evolutionary biologist Martha Nelson told Science magazine. “And there’s a risk that we neglect influenza and other threats at this time.”
Prof Kin-Chow Chang, who has studied the virus and is based at Nottingham University, told the BBC that G4 was not a problem yet but added: “We must not lose sight of potentially dangerous new viruses.”