A day after a nurse who treated an Ebola-stricken patient in Dallas was diagnosed with the virus, public health officials are still trying to figure out how many health-care workers may have had similar exposure.

It is still unclear how, exactly, the nurse at Texas Health Presbyterian Hospital Dallas became the first person to contract the virus in the United States, said Thomas Frieden, director of the Centers for Disease Control and Prevention.

But if one health-care worker was infected, “it is possible other people could have been infected as well,” Frieden said during a briefing with reporters on Monday.

This infection “substantially” changes how public health authorities will respond to the virus in the United States, he said.

“We have to rethink the way we address Ebola infection control, because even a single infection is unacceptable,” Frieden said.

Thomas Frieden, director of the Centers for Disease Control and Prevention, provided an update Monday to the investigation into the spread of the Ebola virus to a nurse at a Dallas hospital. Frieden also apologized for his initial remarks about the nurse's infection, which seemed to blame the nurse or other health care workers for the infection. (AP)

The nurse remains in stable condition at the same hospital that treated Thomas Eric Duncan, a Liberian man who was diagnosed with the virus and died last week. She had “one and only one contact” during the period when she may have been infectious, a person who is being monitored and has exhibited no symptoms of Ebola. In addition, the 48 people who are known to have had possible contact with Duncan before his hospitalization continue to show no symptoms, Frieden said.

Still, the uncertainty about how the nurse was infected — and the fact that she was infected while Duncan was isolated at a hospital — raises more questions about how prepared hospitals and health-care workers are to deal with the additional Ebola cases that authorities say are likely to occur.

“We need to consider the possibility that there could be additional cases, particularly among the health-care workers that cared for [Duncan] when he was so ill,” Frieden said. “We would not be surprised if we did see additional cases in the health-care workers who also provided care to [Duncan].”

Some health-care workers in the U.S. are questioning the adequacy of equipment and protocol in light of reports that a Dallas nurse contracted Ebola after caring for a patient with the virus. (Reuters)

Figuring out exactly what protocols need to be strengthened and who else may have been exposed is particularly difficult because it is not known how the nurse was infected. The CDC is looking at every aspect of patient treatment, ranging from what types of equipment can be used to how protective gear is placed on and off, to try and determine if the current guidelines are strong enough.

“We have not identified a specific problem that led to this infection,” Frieden said. “We have identified a series of things where we can make the care safer and easier for the health-care workers that are providing it.”

Workers have already implemented several improvements over the last day, Frieden said. Among other things, the CDC now says a “buddy system” will be in place for health-care workers removing gear. It is unclear if such a system was in place before in Dallas, as the CDC has previously recommended the buddy system.

While public health authorities will look at all aspects of the way patients with Ebola are cared for, Frieden stressed that they want to make sure the treatment remains safe and effective, as this will encourage anyone else with Ebola to seek care.

At the same time, on Monday afternoon — nearly two full days after the nurse in Dallas was tested — it also remained unclear exactly how many people involved in Duncan’s treatment could have been exposed.

“We do not today have a number of such exposed people or potentially exposed health-care workers,” Frieden said. “It’s a relatively large number, we think….We cast a wide net and then narrow that down.”

About 70 hospital staffers were involved in Duncan’s care, according to medical records obtained by the Associated Press.

Frieden also apologized Monday for his initial remarks about the nurse’s infection. He had said Sunday that a “breach in protocol resulted in this infection,” a remark that was criticized for seeming to blame the nurse or other health-care workers. Frieden said he felt awful that a health-care worker was infected and was sorry if his remarks blamed the nurse or other workers.

“People on the front lines are really protecting all of us,” he said. “People on the front lines are fighting Ebola.”

A Houston hospital has been following guidelines from the Centers for Disease Control by screening all visitors for Ebola since August as a precaution. (Reuters)

National Nurses United, the largest union of registered nurses in the United States, has said that most hospitals are still not prepared to properly deal with Ebola.

Meanwhile, the enhanced screening that began at John F. Kennedy International Airport in New York on Saturday has flagged 91 travelers who came from the three West African countries where Ebola has been so prevalent. Five people were stopped for additional screening, Frieden said. None of these people had a fever or Ebola, he said.

This screening will roll out at airports in Washington, Atlanta, Chicago and Newark on Thursday.

[This post has been updated. First published: 1:50 p.m. Last update: 7:04 p.m.]

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