John Bacon and Marjorie Owens

USA TODAY

Health officials scrambled to learn how a Dallas health care worker caught Ebola at a Texas hospital where she had cared for a man who died from the deadly virus.

The woman was identified Monday as nurse Nina Pham, her family confirmed.

Pham, 26, became infected while treating Thomas Eric Duncan, the first Ebola patient to die in the USA. Pham, who graduated from Texas Christian University's nursing program in 2010, is the first person known to contract the disease in the USA.

By evening, she had received a transfusion of plasma from Kent Brantly, a Texas physician who survived the virus, according to her pastor and the nonprofit medical mission group Samaritan's Purse, Associated Press reported.

Tom Frieden, director of the Centers for Disease Control and Prevention, said Monday that Pham was "clinically stable."

Frieden apologized to officials at Texas Health Presbyterian hospital in Dallas. He said his comments Sunday that Pham's infection was the result of a "breach of protocol" did not reflect on Pham or the hospital's efforts.

"I apologize if people thought I was criticizing the hospital," Frieden said at a news conference Monday. "And I feel awful that a health care worker became infected while helping an Ebola patient."

Frieden said investigators have yet to determine how Pham was infected. He stood by the protocols — including the use of masks, gloves and other equipment — saying they have proven safe for health care workers for decades.

"The existence of the first case of Ebola spread in the U.S. changes some things, and it doesn't change some things," he said. "It doesn't change the fact that we know how Ebola spreads. It doesn't change the fact that it's possible to treat Ebola safely. But it does change substantially how we approach it."

More than 4,000 people have died in the Ebola outbreak, the vast majority of them in the West African nations of Liberia, Guinea and Sierra Leone. Frieden urged hospital workers across the USA to watch for patients with fever or other Ebola symptoms who have traveled from those nations.

Duncan's medical records provided by his family to the Associated Press indicate there may be more than 70 hospital staffers involved in the care of the highly contagious man who died Oct. 8. The CDC has said it is monitoring 48 potential contacts.

There is even concern for Pham's beloved pet. In an interview with WFAA Monday, Dallas County Judge Clay Jenkins said Pham's dog — a King Charles Spaniel named Bentley — will not be killed, despite speculation that the dog could pose a health risk.

"When I met with her parents, they said, 'This dog is important to her, judge. Don't let anything happen to the dog," he said. "If that dog has to be the boy in the plastic bubble, we're going to take good care of that dog."

Bentley has been moved to an undisclosed location and is under the care of Dallas Animal Services.

Father Jim Khoi, Pham's pastor, said Pham is in good spirits, using Skype to communicate with her mother and asking for prayers.

World Health Organization Director-General Margaret Chan issued a statement Monday at a conference in Manila, calling the outbreak "the most severe, acute health emergency seen in modern times."

She said development of a vaccine or cure for Ebola has lagged because the virus is prevalent in such poor nations.

"The outbreak spotlights the dangers of the world's growing social and economic inequalities," Chan said. "The rich get the best care. The poor are left to die."

She said the outbreak is disrupting economies and societies around the world. She said 90% of economic costs of any outbreak "come from irrational and disorganized efforts of the public to avoid infection."

Adequately educating the public should allow governments to curb those disruptions, Chan said. Fear, she said, spreads faster than any virus.

"I have never before seen a health event attract such a high level of international media coverage, day after day after day," Chan said. "I have never seen a health event strike such fear and terror, well beyond the affected countries."

The effort to keep infected people out of the USA is slowly being ramped up. Screenings of people from the three West African nations began Saturday at New York's John F. Kennedy International Airport. Four more airports are scheduled to begin the enhanced screenings Thursday.

In Jacksonville, Baptist Medical Center said Monday it had isolated a patient who was being tested for Ebola, but the diagnosis is "highly unlikely." The hospital released a statement saying the patient had no fever, a common symptom of Ebola, but did report recent casual contact with a traveler from West Africa.

Across the nation, health care professionals evaluated how best to treat U.S. Ebola patients should more of them emerge. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, was asked on ABC's Good Morning America if Ebola patients should be sent only to highly specialized "containment" hospitals.

"That is something that should be seriously considered," said Fauci, an immunologist.

Rose Ann DeMoro, executive director of National Nurses United, a professional association with 185,000 members, said the infection of the Dallas nurse "only heightens the concerns" for medical professionals who could interact with Ebola patients.

DeMoro called for hospitals to implement emergency preparedness plans that would provide training, hazmat suits, isolation rooms and other steps.

"Nurses at multiple hospitals are alarmed at the inadequate preparation they see at their hospitals," DeMoro said in a statement. "The time to act is long overdue."

Marjorie Owens reports for WFAA-TV, Dallas-Fort Worth.