Chinese researchers have discovered a new type of swine flu that can infect humans and has the potential to cause a future pandemic, according to a study released on Monday, though scientists have cautioned that the virus does not pose an immediate global health threat.

The disease, which researchers called the G4 virus, is genetically descended from the H1N1 swine flu that caused a pandemic in 2009. G4 now shows “all the essential hallmarks of a candidate pandemic virus,” said the study, published in the scientific journal Proceedings of the National Academy of Sciences (PNAS).

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.”

Chinese researchers based at several institutions, including Shandong Agricultural University and the Chinese National Influenza Center, discovered the G4 virus during a pig surveillance program. From 2011 to 2018, they collected more than 30,000 nasal swab samples from pigs in slaughterhouses and veterinary teaching hospitals across 10 Chinese provinces.

From these samples, researchers identified 179 swine influenza viruses — but not all of them posed a concern. Some only showed up one year out of the program’s seven, or eventually declined to nonthreatening levels.