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

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

It possesses “all the essential hallmarks of being highly adapted to infect humans,” say the authors, scientists at Chinese universities and China’s Center for Disease Control and Prevention.

From 2011 to 2018, researchers took 30,000 nasal swabs from pigs in slaughterhouses in 10 Chinese provinces and in a veterinary hospital, allowing them to isolate 179 swine flu viruses.

The majority were of a new kind which has been dominant among pigs since 2016.

They found evidence of recent infection, carried by pigs, was starting in people who worked in abattoirs and the swine industry in China. According to blood tests which showed up antibodies created by exposure to the virus, 10.4 percent of swine workers had already been infected.

The researchers were concerned that it could mutate further so that it can spread easily from person to person, and trigger a global outbreak.

The researchers then carried out various experiments including on ferrets, which are widely used in flu studies because they experience similar symptoms to humans — principally fever, coughing and sneezing.

G4 was observed to be highly infectious, replicating in human cells and causing more serious symptoms in ferrets than other viruses.

Tests also showed that any immunity humans gain from exposure to seasonal flu does not provide protection from G4.

While it is not an immediate problem, the researchers said that it has “all the hallmarks” of being highly adapted to infect humans and needs close monitoring.

The scientists further said that measures to control the virus in pigs, and the close monitoring of swine industry workers, should be swiftly implemented.

Professor Kin-Chow Chang, who works at Nottingham University in the UK, told the BBC: “Right now we are distracted with coronavirus and rightly so. But we must not lose sight of potentially dangerous new viruses.”

While this new virus is not an immediate problem, he says: “We should not ignore it.”

Professor James Wood, head of the Department of Veterinary Medicine at the University of Cambridge, said the work “comes as a salutary reminder” that we are constantly at risk of new emergence of pathogens, and that farmed animals, with which humans have greater contact than with wildlife, may act as the source for important pandemic viruses.

A zoonotic infection is caused by a pathogen that has jumped from a non-human animal into a human.

The last pandemic flu the world encountered – the swine flu outbreak of 2009 that began in Mexico – was less deadly than initially feared, largely because many older people had some immunity to it, probably because of its similarity to other flu viruses that had circulated years before, said the BBC report.

That virus, called A/H1N1pdm09, is now covered by the annual flu vaccine to make sure people are protected.

The development comes as the world is still struggling to contain the COVID-19 pandemic that originated in China’s Wuhan city last December.

As of Tuesday, the virus has infected a total of 10,302,867 people globally, while the death toll stood at 505,518.

(With agency inputs)