A Dallas nurse who tested positive for Ebola after caring for a patient who died of the disease arrived Wednesday evening at the Atlanta hospital where two other Americans have recovered from the virus.

Amber Joy Vinson, 29, the second nurse diagnosed after caring for Ebola patient Thomas Eric Duncan at a Dallas hospital, arrived at Emory University Hospital in Atlanta at about 8:30 p.m. ET.

Amber Vinson, the second health care worker to be diagnosed with Ebola in Dallas, has been transported to Emory University Hospital in Atlanta for treatment.

She will be treated in the special isolation unit where three other American Ebola patients have been treated, the hospital said Wednesday night — Dr. Kent Brantly and Nancy Writebol, who both were successfully treated and discharged, and a third unidentified American still being treated there.

Ebola Patient Heads to Atlanta for Treatment

Vinson was flown by ambulance plane to Atlanta from Dallas, where she had been treated in isolation since Tuesday at Texas Health Presbyterian Hospital, the hospital where she works. She had reported a fever Tuesday and been immediately isolated there within 90 minutes, officials said.

Medical records provided to The Associated Press by Thomas Eric Duncan's family show Vinson was actively engaged in caring for Duncan in the days before his death. The records show she inserted catheters, drew blood and dealt with Duncan's body fluids.

Another Dallas nurse who treated Duncan and is currently battling the virus, 26-year-old Nina Pham, is in good condition at Texas Health Presbyterian and will stay in that hospital for now.

On Wednesday night, sources confirmed to NBC 5 that local leaders and the CDC are considering plans to move Pham from Presbyterian Hospital to Emory University Hospital.

The decision will ultimately be up to Pham and how she's feeling. A decision is expected as early as Thursday morning.

CDC: New Diagnosis "a Serious Concern"

Pham and Vinson are two of the 77 hospital workers who are being monitored for Ebola symptoms after caring for Duncan before he died Oct. 8.

Both worked on Sept. 28, 29 and 30, days when Duncan experienced "extensive production" of diarrhea and vomiting, the CDC said Wednesday. Ebola is spread through direct contact with bodily fluids of a sick person or exposure to contaminated objects such as needles.

Missing Attachment The Texas Department of Health confirms that a second helath care worker at Texas Health Presbyterian Hospital is in isolation after testing positive for Ebola.

Still, it is not clear how Pham or Vinson contracted the virus, leading the CDC to call the new diagnosis "a serious concern."

Vinson flew to Dallas from Cleveland one day before she showed symptoms of Ebola, in violation of CDC guidelines, the CDC said Wednesday. She had also taken a Frontier Airlines flight from Dallas to visit her mother and fiance in Akron, Cleveland officials said.

The Cleveland Clinic and The MetroHealth System had employees on the Frontier flight from Dallas to Cleveland, returning from a nursing conference in Texas. In a joint statement with University Hospital, both health systems have placed those employees on plaid leave while their health is being monitored.

"We are confident that these nurses are at low risk of exposure since we understand that the Dallas nurse did not have symptoms at the time. We have taken this measure as an extra precautionary step for our employees, patients, and visitors," they said.

Although Vinson had reported no symptoms or fever, she should not have flown on a commercial flight since she was being monitored, Frieden said.

The agency now wants to talk to all 132 people who flew on that Fronter Airlines flight to Dallas Monday night. It does not believe Vinson could have spread the virus to anybody on that flight, however, because the CDC says people people are not contagious before symptoms develop.

Officials Brace for More Possible Cases

More cases could surface among those who helped treat Duncan before he died, Dallas health and city officials cautioned Wednesday. Health officials are once again completing "contract tracing" to identify people who may have been exposed, in what they call a "two-front fight" against the virus.

Another 75 hospital workers are being actively monitored for symptoms, along with several dozen more people who may have had contact with Duncan or a close associate outside the hospital. However, those who may have been exposed before he was hospitalized are nearing the end of the monitoring period and are now less likely to show symptoms.

"We are preparing contingencies for more, and that is a very real possibility," Dallas County Judge Clay Jenkins said Wednesday.

He and Dallas Mayor Mike Rawlings reassured residents, however, that the system in place to monitor potential exposures and identify symptoms was working and that officials would contain the virus' spread.

"The only way we are going to beat this is person by person, moment by moment, detail by detail," Mayor Rawlings said. "It may get worse before it gets better, but it will get better."

"This is not going to be a situation where we’re going to put protective orders on 75 heath care workers," Jenkins added. "The system right now is working. If they have any temperature or any loose stool or any other symptom, they immediately go to isolation in the hospital, and they are tested."

Missing Attachment Dallas County Health and Human Services director Zach Thompson discusses the second diagnosis of Ebola in a Dallas health care worker, Oct. 15, 2014.

Jenkins hailed Vinson for the "grit and grace" with which she had confronted her diagnosis, comparing her determination to Pham's. "We pray that, like Nina, she will get on a good track," Jenkins said.

"Breach of Protocol" Blamed for 1st Nurse's Infection

The CDC has said Pham's infection was the result of a "breach of protocol" and warned in recent days that more cases could surface among other workers who may have been exposed during Duncan's care.

The confirmation of a second case lends support to nurses' claims this week that they have inadequate training and, in some cases, protective gear, to take care of Ebola patients. It also highlights the need to quickly determine how the health care workers contracted the virus and how many of the other 75 who treated Duncan are at risk.

"They're not prepared" for what they are being asked to do, said RoseAnn DeMoro, executive director of National Nurses United, a union with 185,000 members.

Based on statements from nurses it did not identify, the union described how Duncan was left in an open area of the emergency room for hours. It said staff treated Duncan for days without the correct protective gear, that hazardous waste was allowed to pile up to the ceiling and safety protocols constantly changed.

DeMoro refused to say how many nurses made the statement about Texas Health Presbyterian Hospital, but insisted they were in a position to know what happened.

"We are looking at every element of our personal protection equipment and infection control in the hospital," said Dr. Daniel Varga, chief clinical officer for Texas Health Resources, which operates Texas Health Presbyterian Hospital Dallas.

The second case may help health officials determine where the infection control breach is occurring and make practices safer for health workers everywhere.

For example, if both health workers were involved in drawing Duncan's blood, placing an intravenous line or suctioning mucus when Duncan was on a breathing machine, that would be recognized as a particularly high-risk activity. It also might reveal which body fluids pose the greatest risk.

Missing Attachment Among the things the CDC will investigate is how the workers took off protective gear, because removing it incorrectly can lead to contamination. The CDC is also stiffening protocols as needed.

Frieden said initially that safety measures in place at the hospital should have prevented the virus' spread. But some have questioned how ready and equipped the hospital in Dallas was to treat Duncan and prevent spread of the illness there and whether patients should instead be routed to special facilities that have successfully treated Americans who fell sick with Ebola while abroad.