Five years ago, Mary Millard went to the hospital for heart surgery. A contaminated medical instrument gave her an infection that led to septic shock. Her heart struggled, and her lungs and kidneys started to fail.

“What I caught was pseudomonas, and it’s a very virulent superbug,” says the 60-year-old former nurse who lives in Baton Rouge, La. This bacterium no longer responds to most antibiotics, and “it lives in you permanently, so I’m on lifetime antibiotics,” she says.

Her doctor prescribed one of the most powerful antibiotics available, and there is no clear backup for her if that stops working. “It’s kind of a wait-and-see. And that’s what’s scary.”

Millard is just one of about 2 million Americans who have been infected with a superbug. Tens of thousands die each year, and the numbers are vastly higher on a global scale.

More from NPR here.