WASHINGTON – The dangers confronting health care workers who treat Ebola patients took center stage Friday in the nation's capital and in America's largest city.

While doctors in New York City closely monitored the condition of Dr. Craig Spencer, the nation's newest Ebola patient, others in Bethesda, Md., marveled at the rapid recovery of Nina Pham, a Dallas nurse who contracted the deadly virus only weeks earlier.

Pham is the sixth U.S. patient in the current epidemic to fully recover from the virus after treatment in one of the four specialized biocontainment facilities in the United States.

Spencer, 33, became infected while treating patients in Ebola-stricken Guinea, in West Africa, as a volunteer with the humanitarian group Doctors Without Borders. He's currently in stable condition at Bellevue Hospital Center as health officials try to retrace his travels and find people who he may have infected while he was contagious.

Pham, a nurse at Texas Presbyterian Hospital Dallas, became infected on her job while caring for a Liberian Ebola patient, Thomas Eric Duncan. She was one of more than 70 health care workers at the beleaguered Dallas hospital who were monitored for possible infection after they helped treat Duncan, who later died.

Mandatory quarantine

Also Friday, New Jersey Gov. Chris Christie and New York Gov. Mario Cuomo announced a mandatory quarantine for all health care workers who had direct contact with someone infected with Ebola in Liberia, Sierra Leone or Guinea, the three West African nations where the outbreak is ­centered.

"The steps New York and New Jersey are taking today will strengthen our safeguards to protect our residents against this disease, and help ensure those that may be infected by Ebola are treated with the highest precautions," Cuomo said in a statement.

On Friday, Pham, 26, looked healthy, happy and emotional as she left the clinical center at the National Institutes of Health in suburban Washington, where a medical team helped her beat the same Ebola virus that's killing 70 percent of people who become infected in West Africa.

With her mother, Diana, and sister, Catherine, in attendance, Pham thanked her care team, her public supporters and former Ebola patient Dr. Kent Brantly, for his "selfless act" of donating his plasma.

Because he recovered from Ebola, Brantly's plasma may have developed antibodies against the virus, which may have helped Pham "jump-start" her own immune response, said Jennifer Kanakry, assistant professor of medicine at Johns Hopkins University School of Medicine

"It's still experimental at this point," Kanakry said. "It's been used in a handful of patients with Ebola and it may have some benefits, but it's not been proven to have a benefit yet."

Pham didn't receive any experimental medications during her eight-day stay at NIH, said Dr. Anthony Fauci, director of the NIH's National Institute of Allergy and Infectious Diseases. Aside from Pham being young and very healthy and receiving intensive care immediately in Dallas after becoming infected, Fauci said it's impossible to say what made the difference in Pham's improvement.

"I can't pinpoint in one patient what is the turning point," Fauci said. "The only thing that we're really happy about (is) that the turning point occurred."

Pham seemed fully cognizant of her improbable recovery.

"As a nurse, I have a special appreciation for the care I have received from so many people," she told reporters. "Not just doctors and nurses, but the entire support team."

"I believe in the power of prayer because I know so many people all over the world have been praying for me," she added. "I do not know how I can ever thank you, everyone, enough for their prayers and their expressions of concern, hope and love."

Pham's colleague at the Dallas hospital, nurse Amber Vinson, 29, also contracted Ebola after treating Duncan. Vinson is hospitalized at the biocontainment unit at Emory University Hospital in Atlanta.