The Centers for Disease Control on Monday issued new guidelines for health care workers caring for patients stricken with Ebola, one week after two workers at a Dallas hospital came down with the deadly virus.

No skin may be exposed when wearing protective gear, and workers are to be repeatedly trained in putting on and taking off the equipment, CDC Director Tom Frieden said at an evening telephone press conference. Hospital workers are to check each other as they come in and go out, and hospital workers will be expected to exhaustively practice getting in and out of the equipment.

The goal is to "ritualize" the process, Frieden said.

"Even a single health care worker infection is unacceptable," he said.

Frieden also said that 50 people who came into contact with Thomas Eric Duncan, a Liberian national who died earlier this month after becoming the first confirmed U.S. Ebola case, have passed the 21-day monitoring period, during which people who may have been infected either show symptoms or are cleared. Frieden added that some people were still being monitored.

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The new guidelines go into greater detail than typical CDC directions, and especially focus on taking off protective gear, which is when the greatest risk arises, Frieden said.

Frieden said existing guidelines for Texas Health Presbyterian Hospital in Dallas, where Duncan was treated and two nurses, Nina Pham and Amber J. Vinson, later became infected, were not sufficient.

Meanwhile, authorities are looking to expand the number of hospitals that are designated to handle Ebola patients. Currently only four hospitals have been designated to handle Ebola cases by the U.S.: Emory University Hospital in Atlanta, the National Institutes of Health in Bethesda, Md., St. Patrick Hospital in Missoula, Mont., and Nebraska Medical Center in Omaha.

"We need to have more than just the four [hospitals] in which you have people who are pre-trained, so that you don’t come in, and then that’s the first time you start thinking about it," Dr. Anthony Fauci, the head of the National Institute of Allergy and Infectious Diseases, told NBC's "Meet The Press" on Sunday. "It can’t just be four. We may not even need any more, and we hope we don’t."

The Associated Press contributed to this report.