Anita Bertrand doesn’t remember much about the first time she stole narcotics she was supposed to administer to surgical patients. She doesn’t remember exactly when she installed the intravenous port in her ankle so she could inject the drugs more efficiently. And she doesn’t remember how many patients she may have put at risk before getting into treatment.

But she remembers how easy it was to get away with it.

“I was absolutely impaired, using narcotics while working. … And no one ever noticed,” says Bertrand, 49, a nurse anesthetist in Houston. “Did I make mistakes? I don’t know, and that’s the scary part. I’m not aware of any, but I certainly would not say I was immune to that.”

America’s prescription drug epidemic reaches deep into the medical community. Across the country, more than 100,000 doctors, nurses, technicians and other health professionals struggle with abuse or addiction, mostly involving narcotics such as oxycodone and fentanyl. Their knowledge and access make their problems especially hard to detect. Yet the risks they pose — to the public and to themselves — are enormous.

Read more: USA Today