There’s another potential pandemic looming on the horizon, and this time it might actually be a formidable flu.

Chinese researchers have discovered that a type of swine influenza virus widely circulating among domestic pig populations may also infect and transmit between humans. Their work was published in the American journal Proceedings of the National Academy of Sciences on Monday afternoon local time.

Liu Jinhua of China Agricultural University in Beijing and George Gao of the Chinese Center for Disease Control and Prevention led a team of researchers to investigate the influenza viruses in China’s pig herds.

While swine flu viruses seldom spread to humans, the occasional leap has led to incidents such as the 2009 H1N1 pandemic, which may have infected up to one-fifth of the world’s population.

The Chinese team found that a major type of swine influenza, dubbed G4, is genetically similar to the 2009 virus, and laboratory results suggested it can bind to and invade human cells as effectively as the H1N1 virus. Moreover, ferrets that were infected with G4 spread the virus to healthy ferrets similarly to how humans spread influenza viruses among one another.

When the team took samples from over 300 people working at pig farms across China, they found that about 10% had been infected with the G4 virus. This rate was much higher than in the general population, suggesting that the virus is transmissible from pigs to humans outside of a laboratory environment.

“G4 viruses have all the essential hallmarks of a candidate pandemic virus,” the team wrote in their paper. They further warned that over time, the virus could become better adapted to human hosts and, consequently, become more contagious.

It’s still unclear how lethal the G4 virus might be to humans, partly because infections so far have been sporadic. However, the team discovered G4 has undergone genetic reshuffling that appears to have rendered current influenza vaccines ineffective against it.

“G4 will be a completely new virus to humans if it starts to spread more widely,” Jun Wang, an influenza expert at the University of Arizona, told Sixth Tone. “We would be just as vulnerable to G4 as we are now to the COVID-19 virus.”

Wang, who was not involved in the study, said that ascertaining the virus’ threat level would help doctors be better prepared — for example, they might be able to start screening flu patients for this specific virus. Meanwhile, if researchers were to notice an uptick in G4-caused flu cases, they could quickly move to develop antivirals and vaccines against it.

“We’re almost always behind viruses when they strike. This is important research that could potentially prevent a pandemic,” Wang said. “We know they’re coming for us one day, so we should try and get a head start.”

Editor: David Paulk.

(Header image: Bloomberg Creative/Getty Creative/People Visual)