DALLAS (CNN) -- A Texas doctor has apologized for what he calls mistakes in how his hospital handled Ebola, as schools close out of fear that they're vulnerable to the virus. Also on Thursday, officials are considering barring 76 hospital workers who treated an Ebola patient from boarding airplanes.
The director of the Centers for Disease Control and Prevention says a second Dallas nurse who tested positive for Ebola, who flew a day before it was known that she might be suffering from the virus, should not have been cleared to fly. She reported to the agency that she had a fever, she said, but was told she could go ahead and continue her travel. Now, 132 passengers on her flight are wondering if they were exposed.
As missteps grow, here's the latest on Ebola in the United States:
Hospital official: 'We are deeply sorry'
The Texas hospital where an Ebola patient died and two nurses became infected is apologizing for mistakes made when first confronted with the deadly virus.
Dr. Daniel Varga said Texas Health Presbyterian Dallas mishandled the case of Thomas Eric Duncan. Duncan was initially sent home from the facility despite having a fever and telling a worker he was from Liberia.
"Unfortunately, in our initial treatment of Mr. Duncan, despite our best intentions and a highly skilled medical team, we made mistakes," Varga, the chief clinical officer for Texas Health Services, said in written testimony to the House Energy and Commerce Committee.
"We did not correctly diagnose his symptoms as those of Ebola. We are deeply sorry."
Days after Duncan returned to the hospital, he died from the virus.
But Varga did outline a timeline of the hospital's preparation, saying hospital staffers were given guidance on looking for Ebola symptoms several times over the summer.
He said the hospital has made several policy changes, such as updating the emergency department screening process to include a patient's travel history and increasing training for staffers.
Nurse: 'We never talked about Ebola'
A Texas Health Presbyterian Hospital nurse is speaking out, telling NBC's "Today" show Thursday that nurses did not have mandatory Ebola training, except for an optional seminar that didn't allow them any hands-on practice.
"We never talked about Ebola. We never had a discussion," Briana Aguirre said.
She said she was not involved in treating Duncan, who received care at the hospital in late September and died there on October 8.
Training for Texas Health Presbyterian's nursing staff amounted to "just information," she said. "We were never told what to look for."
"All I know for sure is that he (Duncan) was put into an area where there are around seven other patients," she said. "We took around three hours to make first contact with CDC to let them know what we had of our suspicion. There were no special precautions other than basic contact precautions. No special gear."
She said the hospital did not know what to do with one of his lab specimens.
A lab technician told Aguirre the specimen was "mishandled," she said. "It was a chaotic scene."
She said there was an effort to contact the hospital's infectious disease expert to determine the correct Ebola treatment protocol.
"Their answer was, 'We don't know. We will have to call you back,' " she said.
Government might ground Texas hospital workers
The federal government is weighing putting those who treated Duncan on a list that would prohibit them from being able to fly, an official familiar with the situation told CNN.
In June 2007, federal agencies developed a public health Do Not Board list, which allowed domestic and international public health officials to request that people with communicable diseases who meet specific criteria and pose a serious threat to the public be restricted from taking commercial flights departing from or arriving in the United States. The CDC and the U.S. Department of Homeland Security manage the Do Not Board list.
The CDC is considering lowering the fever threshold that would be considered a possible sign of Ebola, the official also told CNN. The current threshold is 100.4 degrees Fahrenheit (38 Celsius).
The second Ebola-stricken nurse in Texas, Amber Vinson, flew home from Cleveland to Dallas while she had a fever.
Vinson called the CDC to report that she had a temperature of 99.5 Fahrenheit, a federal official told CNN, and she was not told she shouldn't get on the plane. However, it's unknown what exactly she was told.
CDC Director Tom Frieden said Vinson shouldn't have flown because she helped care for Duncan, and because another health worker who cared for him already had been diagnosed with the virus.
He said there's an "extremely low" risk to anyone else on that plane, but the agency is reaching out to everyone on the flight as part of "extra margins of safety."
Vinson, 29, is now being treated at Emory University Hospital in Atlanta, which has successfully treated two other Ebola patients and has not had any employees infected.
Staffing issues at the Texas hospital led to the decision to transfer Vinson to Emory, a federal official told Dr. Sanjay Gupta, CNN chief medical correspondent.
"What we're hearing is that they are worried about staffing issues and a possible walkout of nurses," the official said.
Texas Health Presbyterian Dallas is still treating Nina Pham, the first Dallas nurse who tested positive for Ebola. She also treated Duncan at the hospital.
Pham remains in good condition, officials said. It has not been determined whether she will be transferred to another facility.
Hospital employees can quarantine themselves
With two of its own nurses infected with Ebola, Texas Health Presbyterian said it will allow any concerned employee to have a hospital room.
"Texas Health Dallas is offering a room to any of our impacted employees who would like to stay here to avoid even the remote possibility of any potential exposure to family, friends and the broader public," the hospital said in a statement.
"We are doing this for our employees' peace of mind and comfort. This is not a medical recommendation. We will make available to our employees who treated Mr. Duncan a room in a separate part of the hospital throughout their monitoring period."
Several Texas and Ohio schools close
News of Vinson's travel on a Frontier Airlines plane led to school closures in two states.
In Texas, a few schools in the Belton Independent School District are closed Thursday because two students were on the same flight as Vinson from Cleveland to Dallas -- Frontier Airlines Flight 1143, the superintendent said.
And in Ohio, two schools in the Solon School District in suburban Cleveland are closed Thursday because a staffer "traveled home from Dallas on Frontier Airlines Tuesday on a different flight, but perhaps the same aircraft" as Vinson, the school district said in a statement.
"Although we believe what the science community and public health officials are telling us about the low risk of possible transmission of the virus through indirect contact, we are nonetheless taking the unusual step of closing the dual school building for Thursday so that we can have the schools cleaned and disinfected," the statement said.
Frontier Airlines grounds six crew members
The school districts aren't the only ones concerned about Vinson's travels.
Frontier Airlines placed six crew members on paid leave for 21 days "out of an abundance of caution," CEO David Siegel wrote in a letter to employees.
The airline also removed the plane's seat covers and carpet near where the infected passenger sat, even though it had not been asked to by the CDC, Siegel said.
Meanwhile, four major U.S. airports will begin enhanced screenings for Ebola on Thursday. They are Newark Liberty, Washington Dulles, Chicago O'Hare and Hartsfield-Jackson Atlanta.
Hospital fires back after claims
After scathing allegations by a nurses' union, a Texas Health Presbyterian spokeswoman said some of the claims were not true.
National Nurses United, citing interviews with nurses at the hospital, said Duncan was "left for several hours, not in isolation, in an area where other patients were present" during his second visit to the hospital.
But hospital spokeswoman Candace White said Duncan "was moved directly to a private room and placed in isolation" during his second visit.
And after the union claimed "there was no one to pick up hazardous waste as it piled to the ceiling," White said the waste was "well-contained in accordance with standards, and it was located in safe and containable locations."