Scientists are getting seriously concerned: a new superbug gene has been discovered for the first time in the United States.

For a while now, the medical community has been worried about an overuse of antibiotics paving the way for the evolution of a superbug that we won’t be able to stop, and now scienists are worried that this newly discovered gene could be a sign that it is closer than we think, according to a U.S. Military HIV Research Program statement.

The gene is called mcr-1 and was found in a woman from Pennsylvania who had an E. coli infection. But this particular gene could likely be found in any bacteria, not just E. coli, which is what makes it so dangerous.

Mcr-1 is essentially found on pieces of DNA called plasmids, which bacteria can exchange between themselves.

The gene itself is not necessarily worrying, as it only protects against antibiotic called colistin, which isn’t used much due to the negative effect it has on kidneys. It’s considered an antibiotic of last resort.

But it does mean that those who get the superbug wouldn’t even have that last resort available to them, and this bacteria can spread quickly through hospitals and into the public.

“Colistin is one of the last efficacious antibiotics for the treatment of highly resistant bacteria. The emergence of a transferable gene that confers resistance to this vital antibiotic is extremely disturbing. The discovery of this gene in the U.S. is equally concerning, and continued surveillance to identify reservoirs of this gene within the military healthcare community and beyond is critical to prevent its spread,” reported Dr. Patrick McGann, MRSN, WRAIR.