A strain of flu virus spreading in Chinese pigs has shown it can also infect humans, suggesting that another pathogen with pandemic potential waits in the wings behind the coronavirus.

The flu strain that jumped to humans has become predominant among pigs across China since 2016, according to a team of researchers that includes George Gao Fu, head of China’s Center for Disease Control and Prevention. The researchers based their findings on surveillance studies conducted in 10 provinces from 2011 through 2018.

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Influenza is one of the most frequent causes of pandemics, which occur when a new infectious disease that no one has immunity to sweeps around the world. Pigs are known to harbor flu viruses that can occasionally infect workers they come into contact with, creating a risk of wider outbreaks. Called G4 EA H1N1, the swine flu strain bears genes similar to those in the virus that caused the 2009 flu pandemic, according to the study published in the Proceedings of the National Academy of Sciences, a research journal. Tests found the virus in about 10% of 338 swine workers whose serum samples were collected between 2016 and 2018.

The human infections indicate that the flu strain “possesses all of the essential hallmarks of a candidate pandemic virus” and that it poses “a serious threat to human health,” the researchers concluded.

Zoonoses, diseases that jump from animals to humans, are one of the most common sources of dangerous new infections. Ebola, HIV, and the coronavirus itself are all examples of deadly pathogens that originated in animals. SARS-CoV-2, the cause of the COVID-19 pandemic that’s infected more than 10 million people and killed more than 500,000 of them, is widely considered by scientists to have come from bats, a natural reservoir of such pathogens.


©2020 Bloomberg L.P.