The most prevalent strain of influenza spreading among pigs in China has sparked concern among scientists, who say it has certain properties that give it pandemic potential. Chief among them: The virus has infected humans. So far it isn’t known to spread from person to person, but the worry is that with further mutations, it could start to do so. Populations still battling the coronavirus SARS-CoV-2, which also emerged in China and is believed to have originated in animals, could be vulnerable again.
1. What’s the problem?
Pigs are routinely catching variations of the flu and mostly it’s not a big deal, because the viruses usually don’t spread to people. But that’s not the case with the most-common strain infecting pigs in China since 2016, dubbed the G4 EA H1N1 virus. In past years it jumped the species barrier to infect possibly dozens of humans, according to so-called serosurveys that look for the presence of antibodies in a person’s blood, which indicates prior exposure to the virus. New research published June 29 in the Proceedings of the National Academy of Sciences showed the virus can replicate in cells lining the human airway, and can be efficiently transmitted among ferrets, an animal used to study flu viruses. Those features led that research team to declare that it “possesses all of the essential hallmarks of a candidate pandemic virus” and poses “a serious threat to human health.”
2. How worried should we be?
It’s hard to say. Influenza pandemics occur when a virus, against which there is little or no existing immunity, emerges in the human population and efficiently transmits from person to person. Most people lack immunity to this strain, which has a novel variant of hemagglutinin, the surface protein flu viruses use to grip onto cells targeted for invasion. There are also no vaccines available. Michael Ryan, executive director of health emergencies at the World Health Organization noted that many novel flu viruses, including ones circulating in birds, have pandemic potential, and that G4 EA H1N1 has been closely watched by scientists in China and around the world. Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases in the U.S., said it’s not an immediate threat, but bears watching.