A flu strain being found in more and more pigs in China has the potential to jump to humans, according to an article on ScienceMag.org. The strain, being called the “G4 variant,” is an avian flu strain with “bits of mammalian strains mixed in,” ScienceMag.org reported. Humans have no immunity to avian flu, they noted.

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. The G4 variant is especially concerning because its core is an avian influenza virus—to which humans have no immunity—with bits of mammalian strains mixed in.

Two cases of G4 influenza infections of humans have been documented and both were dead-end infections (from pig to human) that did not transmit to other people.

Robert Webster, an influenza investigator who recently retired from St. Jude Children’s Research Hospital, says it’s a “guessing game” as to whether this strain will mutate to readily transmit between humans, which it has not done yet. “We just do not know a pandemic is going to occur until the damn thing occurs,” Webster says, noting that China has the largest pig population in the world. “Will this one do it? God knows.”

Read more at www.sciencemag.org