In the midst of COVID-19, the last thing we need is another pandemic. But scientists in China are now warning that they have identified a new flu virus in pigs that could possibly cause a future flu pandemic.
The virus, called G4 EA H1N1, is a genetic mix of the H1N1 "swine flu," which caused a flu pandemic in 2009, and other flu viruses. The study, published Monday (June 29) in the journal Proceedings of the National Academy of Sciences, found evidence that G4 EA H1N1 has infected workers on pig farms in China. But importantly, there is no indication that the virus spreads from person to person, according to CNN.
The authors caution that the virus is not an immediate health threat, according to the BBC. But they say that controlling this virus in pig populations and monitoring for signs of it in humans "should be urgently implemented."
The 2009 H1N1 flu pandemic is estimated to have caused between 151,700 and 575,400 deaths worldwide, and to have infected up to 1.4 billion people, according to the Centers for Disease Control and Prevention. After it ended, the virus became one of the seasonal flu viruses that circulates in people every year. Eventually, the virus must have spread from humans back to pigs, where it mixed with other flu viruses to create G4 EA H1N1, according to CNN.
In the new study, the researchers analyzed nearly 30,000 nasal swabs from pigs in slaughterhouses in 10 provinces in China collected between 2011 and 2018. From these samples, they found nearly 180 different strains of flu virus infecting pigs.
However, many of these viruses didn't circulate for long. They showed up one year and disappeared the next. But G4 EA H1N1 kept showing up, and has been the predominant flu strain in pigs since 2016, the authors said.
Tests in lab dishes showed the virus can bind to receptors on human cells and replicate efficiently in human airway cells.
What's more, when the researchers analyzed 338 blood samples from workers in the swine industry, they found that about 10% had antibodies to the virus, indicating they had been exposed to the virus. For younger workers ages 18 to 35, the percent of tests that turned up positive (called the positivity rate) was 20%, suggesting young adult workers have a higher risk of infection, the authors said.
Even though the authors say this virus has "the essential hallmarks of a candidate pandemic virus," experts caution that this doesn't mean it will definitely cause a future pandemic.
"Our understanding of what is a potential pandemic influenza strain is limited," Angela Rasmussen, a virologist at Columbia University, posted on Twitter. "Sure, this virus meets a lot of the basic criteria but it's not for sure going to cause a hypothetical 2020 flu pandemic, or even be a dominant strain in humans."
Still, the new study is a "salutary reminder that we are constantly at risk of new emergence of zoonotic pathogens," James Wood, head of Department of Veterinary Medicine at the University of Cambridge, who was not involved in the study, said in a statement. In particular, "farmed animals, with which humans have greater contact than with wildlife, may act as the source for important pandemic viruses," Wood said.
Originally published on Live Science.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.
Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.