WASHOE COUNTY, NV (NBC News/WCMH) – One woman is dead after traveling abroad and contracting a rare superbug that was resistant to every antibiotic available in the United States.

NBC News reports that the Nevada woman was in her 70s, and tests showed that she was battling a dangerous mutation of bacterial group known as carbapenem-resistant Enterobacteriaceae (CRE). The mutation itself is known as NDM-1.

CRE is an entire bacteria family that are resistant to drugs. Half of the people who become infected by a CRE die. Most CREs in the states can be killed with last-ditch antibiotics, but the NDM-1 is resistant to even more types of antibiotics, and doctors usually don’t know which drug will work.

The woman isn’t the first in the US to die from a near-ultimate superbug, but public health experts say this is a stark reminder that unkillable bacteria are spreading and evolving.

Dr. Lie Chen of the Washoe County Health District wrote that the woman had been hospitalized several times in India over the last two years for a right femur fracture and subsequent benign tumors known as osteomas.

“We feel it is likely this is where the infection was acquired,” Randall Todd of the Washoe County health department told NBC News. “Hospitals should be reminded that they have got to take a travel history and be open to the possibility that an uncommon infection might be responsible.”

Doctors and staff in Washoe County worked closely with the CDC to identify the bacteria, but the bug mutated and evolved too quickly.

“It just evolved too fast,” Chen said. “The physicians tried their best to rescue her.”