A nurse who was infected with Ebola after treating a sick patient said she didn't have enough training beforehand on how to protect herself.

"The first time that I put on the protective equipment, I was heading in to take care of the patient," Amber Vinson told NBC's "Today" show in an interview broadcast Thursday.

Vinson was one of the more than 70 medical personnel who were involved in the care of Thomas Eric Duncan at Texas Health Presbyterian Hospital Dallas. After being sent home from the emergency room Sept. 26, Duncan returned two days later and was quickly diagnosed with the virus. He died Oct. 8.

"We didn't have excessive training where we could don and doff, put on and take off the protective equipment, till we got a level of being comfortable with it," Vinson said. "I didn't have that, and I think that's very important for hospitals across the nation, big and small."

But Vinson told CNN in an interview broadcast Thursday night that she has no idea how she became infected.

"I go through it almost daily in my mind: What happened, what went wrong. Because I was covered completely every time. I followed the CDC protocol for donning and doffing every time. I never strayed," she told CNN. "It is a mystery to me."

Vinson flew Oct. 13 on a commercial jet from Cleveland to Dallas, one day before feeling the first symptoms of her virus. She said in the "Today" interview that she monitored her temperature and checked in with health officials before flying. She said reports that she felt sick while traveling were false.

The federal Centers for Disease Control and Prevention in Atlanta has acknowledged that Vinson wasn't stopped from flying. CDC Director Tom Frieden later said that was a mistake on the agency's part.

"I would never go outside of guidelines or boundaries or something directly from the CDC telling me I can't go (or) I can't fly," Vinson told the "Today" show.

Vinson attended to Duncan on Sept. 30, the day he tested positive for Ebola, according to medical records that Duncan's family released to The Associated Press. Like another nurse who became infected, Nina Pham, the reports note that Vinson wore protective gear and a face shield, hazardous materials suit, and protective footwear. At the time, Duncan's body fluids were highly infectious if someone made contact with them. At one point, Vinson inserted a catheter into Duncan.

She said she became fearful after learning that fellow nurse Pham, who also treated Duncan, was suspected of having Ebola.

"I was floored," she said told the "Today" show. "I was afraid for myself and my family because I did everything that I was instructed to do every time and I felt like if Nina can get it, any one of us could have gotten it."

Medical experts say an Ebola patient who survives the disease gains lasting immunity to the strain with which they were infected. Vinson said Thursday that she feels good, but still gets tired sometimes. Asked whether she would be willing to treat another Ebola patient, Vinson said "absolutely."

She told CNN that her engagement ring was among her personal items that were destroyed when her apartment was decontaminated. "I was crushed," she said.

Also Thursday, Texas health officials said the last of 177 people known to have been in contact with Duncan, Pham or Vinson would come off monitoring Friday. In addition, those who flew on the same flights as Vinson have also recently been cleared from monitoring. None of those people became infected.