After COVID-19, China Warns New Swine Flu Strain Has Pandemic Potential

A study published by a team of Chinese researchers is sounding the alarm about an influenza strain found in Chinese pigs called "G4 EA H1N1" that might trigger the next global pandemic. Thus far, the G4 virus is only transmissible between pigs and can't be transmitted from person-to-person — yet.

The danger that this might occur in the future, however, led the study authors to urge closer monitoring of this flu virus. Prevalent among pigs in China, G4 is a blend of a similar strain found in European and Asian birds.

This is the H1N1 strain that caused the 2009 swine flu pandemic (from January 2009 to August 2010, leading to the death of 18,000 humans) and a North American H1N1 that caused the 2009 flu pandemic in North America.

Chinese researchers analyzed 30,000 swabs collected from pigs at slaughterhouses in 10 Chinese provinces from 2011 to 2018. They found 179 swine influenza viruses, most of which were G4.

The study said the G4 virus "has shown a sharp increase since 2016, and is the predominant genotype in circulation in pigs detected across at least 10 provinces." It documented two cases of G4 infections in humans. The virus, however, can't be transmitted from person-to-person. Flu outbreaks in the past, however, have proven influenza viruses often jump from pigs to humans.

The study said G4’s inclusion of genes from the 2009 H1N1 pandemic “may promote the virus adaptation,” allowing for human-to-human transmission. As a result, the study urged the monitoring of farms and workers in China as further transmission might cause the G4 virus to “adapt and become a pandemic.”

It pointed out all the evidence indicated the G4 EA H1N1 virus "is a growing problem in pig farms, and the widespread circulation of G4 viruses in pigs inevitably increases their exposure to humans." This view isn't widely shared, however.

“The likelihood that this particular variant is going to cause a pandemic is low,” said Dr. Martha Nelson, who read the study. Dr. Nelson is an evolutionary biologist at the U.S. National Institutes of Health’s Fogarty International Center who studies pig influenza viruses and their spread to humans.

“You’re really not getting a good snapshot of what is dominant in pigs in China,” according to Dr. Nelson, who also said there is a need for more sampling.

The study is titled, "Prevalent Eurasian avian-like H1N1 swine influenza virus with 2009 pandemic viral genes facilitating human infection." It was published Monday in the peer-reviewed journal, Proceedings of the National Academy of Sciences.