Jul 01, 2020 04:25 PM

Scientists Identify New Swine Flu With Pandemic Potential

Pigs raised on a farm in the U.S. on May 5.
Pigs raised on a farm in the U.S. on May 5.

Chinese scientists have identified a new form of swine flu virus with the potential to cause a pandemic, according to peer-reviewed research published Monday in the U.S. science journal PNAS.

The pathogen, known as G4, genetically resembles the H1N1 variant that spread worldwide in 2009 and 2010. Experts said that there is no immediate danger of a new pandemic.

Nonetheless, the virus “carries all the essential hallmarks of being highly adapted to infect humans,” said the researchers, who are affiliated with several Chinese universities and the country’s Center for Disease Control and Prevention.

The paper comes at a time of heightened anxiety about virus strains jumping from animals to people and causing disease. The current Covid-19 pandemic, which has killed more than half a million people globally, is thought to have begun when a previously unknown, highly infectious coronavirus passed from animals to humans in central China.

The researchers took 30,000 nasal swabs from pigs in slaughterhouses across China between 2011 and 2018, which they used to isolate 179 flu viruses. Most were of the G4 variety, which has been predominant in pigs since 2016.

Further testing revealed that G4 is highly infectious, binds easily to human cell receptors, and replicates efficiently within them.

The scientists also found that it caused more severe symptoms in ferrets than other viruses. Ferrets are commonly used in flu research because they display similar symptoms to humans.

Additionally, the researchers showed that human exposure to seasonal flu viruses does not develop effective immunity against G4.

Some 10.4% of swine workers and 4.4% of the general population returned positive antibody tests for the virus, proportions that the researchers described as disconcerting. Younger workers showed higher infection rates than those over 35.

Having bridged the species gap, the virus could become a pandemic threat in future if it starts transmitting readily between humans, experts said.

Ian Mackay, a virologist at the University of Queensland in Australia, told Caixin in a phone interview that the virus “ticks a lot of boxes” for a potential pandemic pathogen.

“It does have a lot of the tools that make it quite a risk for spread somewhere down the track, with some adaptation,” he said. “Perhaps it’s already ready to go, it just hasn’t had the opportunities.”

“From the data presented, it appears that this is a swine influenza virus that is poised to emerge in humans,” Edward Holmes, an evolutionary biologist at the University of Sydney, told Science magazine. “Clearly this situation needs to be monitored very closely.”

However, other specialists said the virus cannot yet spread readily from person to person, a key characteristic of large epidemics.

“There’s no evidence that G4 is circulating in humans, despite five years of extensive exposure,” tweeted University of Washington biology professor Carl Bergstrom.

Contact reporter Matthew Walsh ( and editor Joshua Dummer (

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