What the world doesn’t need now is a pandemic on top of a pandemic. So a new finding that pigs in China are more and more frequently becoming infected with a strain of influenza that has the potential to jump to humans has infectious disease researchers worldwide taking serious notice.

The disease, which researchers called the G4 virus, is genetically descended from the Swine Flu that caused a pandemic in 2009. But Dr. Angela Rasmussen, a virologist at Columbia University’s public health school, warned the public not to “freak out.”
“Our understanding of what is a potential pandemic influenza strain is limited,” she 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.”
When multiple strains of influenza viruses infect the same pig, they can easily swap genes, a process known as “reassortment. The virus is a unique blend of three lineages: one similar to strains found in European and Asian birds, the H1N1 strain that caused the 2009 pandemic, and a North American H1N1 that has genes from avian, human, and pig influenza viruses.
Further tests showed that G4 can infect humans by binding to our cells and receptors, and it can replicate quickly inside our airway cells. And though G4 holds H1N1 genes, people who have received seasonal flu vaccines won’t have any immunity. G4 already appears to have infected humans in China. There is no evidence yet that G4 could spread from person to person.