New federal guidelines for health care workers stress practice and rituals in taking off protective gear while contacting Ebola patients. The Centers for Disease Control and Prevention issued the far more detailed guidance Monday night after two nurses became infected while taking care of Thomas Eric Duncan in Dallas.

The CDC had first issued Ebola guidelines to U.S. hospitals in 2008 and updated them just this past August, but the infections of nurses Nina Pham and Amber Vinson show they were not clear enough, CDC Director Dr. Thomas Frieden told reporters Monday night.

"The hospital caring for the first patient, Mr. Duncan, relied on these guidelines and two healthcare workers became infected. This is unacceptable," Frieden told reporters.

"We may never know exactly how that happened, but the bottom line is they didn’t work for that hospital," he added.

It's not so much which particular equipment is used, says Frieden. More important is that it is used correctly.

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"Anybody who is going to work with them is going to be trained in and demonstrate competency in anything they are going to be putting on and taking off," Frieden said. "Second, no skin may be exposed when PPE (personal protective equipment) is worn," he added. Every nurse, doctor or technician putting on or taking off PPE must be watched by another trained expert.

"We need to increase the margin of safety," Frieden said. He described it as an almost ritualistic approach. Gear must be wiped down with a virus-killing wipe before it comes off, and everyone will be told to take a shower after they get the PPE off, he said.

Health care workers are at especially high risk of catching Ebola because they are in very close contact with patients who are vomiting, sweating profusely and suffering diarrhea from the virus. Virus-laden droplets can get onto hands and into the eyes, nose and mouth if caregivers don't take the gear off precisely.

"The enhanced guidance is centered on three principles: All healthcare workers undergo rigorous training and are practiced and competent with PPE, including taking it on and off in a systemic manner; No skin exposure when PPE is worn; All workers are supervised by a trained monitor who watches each worker taking PPE on and off," CDC said in a statement.

"All patients treated at Emory University Hospital, Nebraska Medical Center and the NIH Clinical Center have followed the three principles. None of the workers at these facilities have contracted the illness."

Every U.S. doctor who has cared for someone with Ebola in the United States — there have been six patients, including Duncan, who died — has signed off on the guidelines, as have experts at Doctors Without Borders, also known as Medecins San Frontieres or MSF, which treats patients in West Africa.

"Focusing only on PPE gives a false sense of security of safe care and worker safety," the CDC added.

"Training is a critical aspect of ensuring infection control. Facilities need to ensure all healthcare providers practice numerous times to make sure they understand how to appropriately use the equipment, especially in the step by step donning and doffing of PPE. CDC and partners will ramp up training offerings for healthcare personnel across the country to reiterate all the aspects of safe care recommendations."

The whole country's been jumpy since Duncan turned up with Ebola, even though more than 40 people he was in contact with were cleared of Ebola over the past few days.

Frieden said the CDC has received more than 400 calls from hospitals who feared they had an Ebola patient. About 10 percent seemed worth investigating, he said. Not one since Duncan has turned out to actually have Ebola. But the CDC expects more cases could come so long as Ebola continues to ravage Guinea, Sierra Leone and Liberia.