A new flu virus found in Chinese pigs has become more infectious to humans and needs to be watched closely in case it becomes a potential “pandemic virus”, a study said, although experts said there is no imminent threat.

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

China took action against an outbreak of avian H1N1 in 2009, restricting incoming flights from affected countries and putting tens of thousands of people into quarantine. The new virus identified in the study is a recombination of the 2009 H1N1 variant and a once prevalent strain found in pigs.

Who conducted the study?

A team of Chinese researchers looked at influenza viruses found in pigs from 2011 to 2018 and found a G4 strain of H1N1 that has “all the essential hallmarks of a candidate pandemic virus”, according to the paper, published by the US journal, Proceedings of the National Academy of Sciences (PNAS).

According to the scientists, including those from the Chinese Center for Disease Control and Prevention, these G4 viruses bind to receptor molecules in human cells, and can replicate in the outer layer of the respiratory system. 

What does the study say?

The PNAS study demonstrated that the newly identified virus can efficiently infect ferrets via aerosol transmission, causing severe clinical symptoms in them like sneezing, wheezing, coughing, and a mean maximum weight loss ranging from 7.3 to 9.8 per cent of the mammals’ body mass.

The study also noted that humans are not protected from the G4 virus by the immunity offered by other human influenza vaccine strains, indicating that there is no preexisting population immunity to the virus.

The study highlights the risks of viruses crossing the species barrier into humans, especially in densely populated regions in China, where millions live close to farms, breeding facilities, slaughterhouses and wet markets.

Pig farm workers showed elevated levels of the virus in their blood, the authors said, adding that “close monitoring in human populations, especially the workers in the swine industry, should be urgently implemented”.

The scientists said two recent cases of G4 virus infection, reported in 2016 and 2019, were of a 46-year-old and a nine-year-old, respectively. According to the study, the two patients had neighbours who reared pigs, suggesting that G4 virus “could transmit from swine to humans, and lead to severe infection and even death”.

How experts reacted to the study?

The World Health Organisation (WHO) will read the Chinese study carefully, spokesman Christian Lindmeier told a Geneva briefing, saying it was important to collaborate on findings and keep tabs on animal populations. “It also highlights we cannot let our guard down on influenza and need to be vigilant and continue surveillance even in the coronavirus pandemic,” he added.

Chinese foreign ministry spokesman Zhao Lijian told a daily news conference that China was closely following developments. “We will take all necessary measures to prevent the spread and outbreak of any virus,” he said.

While it is capable of infecting humans, there is no imminent risk of a new pandemic, said Carl Bergstrom, a biologist at the University of Washington. “There’s no evidence that G4 is circulating in humans, despite five years of extensive exposure,” he tweeted.

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