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Not Now, Ominous New Swine Flu Strains

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Piglets resting in their sty at the Lower Drayton Farm in the UK.
Piglets resting in their sty at the Lower Drayton Farm in the UK.
Photo: Christopher Furlong (Getty Images)

Researchers in China are sounding the alarm over strains of the influenza virus that have become common among some farm pigs—strains that have the potential to erupt into an easily transmissible pandemic in people, they warn. But while the threat is serious and worth keeping an eye on, it’s not an urgent risk of doom.

The scientists’ findings were published in the Proceedings of the National Academy of Sciences on Monday. They detail the troubling emergence of certain influenza strains that have become commonly transmitted between studied pigs in China since 2016. These strains, which the researchers have dubbed G4, appear to be the result of different flu viruses mixing and swapping genes inside pigs, particularly avian flu viruses native to birds living in Asia and Europe. What makes it scarier is that G4 viruses also appear to contain genes seen in the last virus that went pandemic before covid-19, a strain of H1N1 flu that circled the globe between 2009 and 2010 and may have killed around 200,000 people worldwide.

The G4 viruses “have all the essential hallmarks of a candidate pandemic virus,’” the researchers wrote.


Influenza viruses are a persistent source of pandemics because of their ability to quickly mutate and spread between different species. A flu virus that starts in birds can migrate to pigs and then be transmitted to farm workers, along the way picking up or rearranging genes that render them largely unrecognizable to our immune system (meaning little immunity to infection in the general population) and easily transmittable between people. When that unlucky mix of factors happens, you can get a pandemic flu.

That makes these G4 viruses all the more worrying, because they appear to have already checked off some of these steps. But importantly, potential pandemic strains of flu also often flame out and never mutate into something that can spread easily between people. The scientists cite blood testing results showing the presence of antibodies to G4 viruses in 10 percent of tested pig farm workers, as well as 20 percent of pig farm workers between the ages of 18 to 35. But there’s no evidence cited that these viruses have spilled out into the general public, suggesting that they’re only spreading from animals to humans, not humans to humans. Right now, we also don’t have any indication about whether human infections of G4 flu cause serious disease.


“Basically, this virus is certainly worth watching, but there’s no evidence it is going to cause an imminent pandemic,” Angela Rasmussen, a virologist at Columbia University, told Gizmodo.

This doesn’t mean that the findings should be dismissed as nothing to worry about, assuming they’re validated by other research. Potential pandemic diseases, as the world has sorely learned this year, are near impossible to stop once they pick up steam and start spreading between people. So scientists need an early warning system that can identify possible globe-spanning pathogens before they show up out of nowhere. That’s especially key for influenza, since, unlike with covid-19, we have the capability to create relatively effective flu vaccines in a short time that should provide some protection.


“What is clear is that there will be other pandemics in the future, and this study is yet another reminder that the single most important thing we can do to protect public health is to prepare for the novel emerging viruses, whatever they may be. That includes influenza viruses like this one, as well as other viruses that are capable of infecting humans and causing disease,” Rasmussen said.

For the average person, though, it’s the pandemic in front of us that still remains the present danger.