At a news conference on Friday, Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, announced that nurse Nina Pham is "free of Ebola" and said it was "a privilege" to treat her at the National Institutes of Health in Maryland. (AP)

Nina Pham, the first nurse diagnosed with Ebola in the United States, walked out of the National Institutes of Health on Friday morning after doctors there declared her free of the Ebola virus.

Pham, 26, had cared for an infected Ebola patient in Dallas. She was treated at the Bethesda, Md., facility, which has a special unit for patients who need advanced isolation and extended stays.

“She has no virus in her,” said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, at a news conference. “She feels well.”

He described Pham as “an extraordinarily courageous and lovely person” and “a devoted nurse.”

Prior to the start of the news conference, Pham stood with NIH doctors and staff and her mother and sister, smiling and wearing a black suit with a turquoise shirt at the NIH facility. She then read a statement and did not take any questions.

“I feel fortunate and blessed to be standing here today,” Pham said. “I would first and foremost like to thank God, my family and friends. Throughout this ordeal, I have put my trust in God and my medical team. I am on my way back to recovery, even as I reflect on how many others have not been so fortunate.”

Pham later in the day met with President Obama at the White House. At his daily press briefing White House press secretary, Josh Earnest said the president’s decision to greet Pham was “an opportunity, first of all, to thank her for her service.”

Pham did not undergo any additional medical testing before greeting — and hugging — the president, Earnest said, noting that she had been shown to be free of the virus on five separate occasions before being released.

At the news conference in Bethesda, Pham said she looked forward to returning to Texas and to a normal life with her dog, Bentley. The King Charles spaniel was quarantined after Pham was diagnosed. He tested negative for Ebola but is still in his 21-day incubation period until the end of the month, according to Texas officials.

Pham was the first person to contract the disease on U.S. soil and had been part of the team that treated Thomas Eric Duncan, a Liberian man who flew to Dallas last month before being diagnosed with Ebola.

“She was with a very sick person,” Fauci said.

Duncan later died.

On Thursday, officials announced that a doctor in New York became the fourth person to be diagnosed with Ebola in the United States. He had recently returned from treating patients in West Africa. On Friday afternoon, officials in New York said the patient, Craig Spencer, was in stable condition.

The Special Clinical Studies Unit at NIH, where Pham was treated, opened in 2010. It is one of four in the country with a special bio-containment unit. They were designed in the aftermath of the Sept. 11, 2001, terrorist attacks to protect against bioterrorism.

The unit in Bethesda was originally designed to care for personnel working at the U.S. Army Research Institute of Infectious Diseases in case they were exposed to infectious agents. More recently, it has been used to house healthy volunteers participating in live vaccine trials.

Fauci said that doctors and staff at NIH did not administer any experimental drugs to Pham.

Patients infected with the Ebola virus require a large number of staffers to provide care round-the-clock. At NIH, that comes out to about 27 people a week — doctors, nurses, support staff — for one patient, said John Gallin, director of the NIH Clinical Center. With about 50 to 60 such personnel specially trained for infectious disease and critical care, NIH can only care for two Ebola patients at a time, he said.

Amber Vinson, the second Dallas nurse who became stricken with Ebola at Texas Presbyterian, “is making good progress in her treatment,” Emory University Hospital in Atlanta said in a statement Friday. “Tests no longer detect virus in her blood.”

Vinson, who was transferred to Emory for treatment last week, remains within the hospital’s Serious Communicable Diseases Unit “for continued supportive care.”

“We do not have a discharge date at this time,” the statement said.

Vinson also worked as a nurse at Texas Presbyterian Hospital in Dallas, where Duncan was treated. She flew from Cleveland to Dallas a day before being diagnosed.

Another person infected with the disease, NBC freelance cameraman Ashoka Mukpo, was also declared Ebola-free. He contracted Ebola in Liberia and was treated at Nebraska Medical Center in Omaha.

Dana Hedgpeth, Josh du Lac, Juliet Eilperin and Lena Sun contributed to this report.