Dr. Craig Spencer, who is being treated for Ebola in Manhattan after becoming New York's first resident to be diagnosed with the deadly virus, is in serious but stable condition and looks better, a hospital official said Sunday.

Dr. Ram Raju, president of the New York City Health and Hospitals Corporation, said he spoke earlier Sunday with Spencer, who was experiencing "the expected symptoms of the virus."

"The patient looks better than he looked yesterday, but he remains in serious but stable condition," Raju said at a press conference, declining to elaborate on symptoms that Spencer is experiencing, citing patient privacy. "He tolerated the plasma treatment well (from an aid worker who had been ill with Ebola) and had a good night sleep."

Spencer recently returned from treating Ebola patients in Africa with Doctors Without Borders and was diagnosed in New York on Thursday. He received a plasma transfusion from Nancy Writebol, an aid worker who contracted the deadly disease in Africa and survived.

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New York City Mayor Bill de Blasio said at the press conference that he spoke by phone with Spencer for a few minutes Saturday afternoon. He described the physician as "energetic, focused" and "concerned for others," with "great sense of humor."

"The best way to stop this epidemic is to help the people in West Africa."

He urged New Yorkers to remain calm while the hospital cared for the city's first Ebola patient.

"There is no reason for New Yorkers to change their habits in any way," he said. "New Yorkers are strong, resilient and focused, and they understand there is no cause for alarm."

Meanwhile, a debate continued Sunday over whether health workers returning from Ebola-hit countries should be forced into quarantine, after the governors of New York, New Jersey and Illinois imposed mandatory quarantines at airports over the weekend.

Kaci Hickox, the first aid worker to be quarantined under the new policy in New Jersey, wrote in a first-person account in the Dallas Morning News that she encountered fear and disorganization when she returned from caring for Ebola patients in Sierra Leone.

Dr. Anthony Fauci, director of the National Institute of Allergies and Infectious Diseases at the National Institutes of Health, warned against "draconian" requirements for health care workers returning from West Africa, suggesting that mandatory quarantines may go too far.

"The best way to stop this epidemic is to help the people in West Africa," he said Sunday on NBC's Meet the Press. "We do that by sending people over there, not just from the U.S.A, but from other places. We need to treat returning people with respect."

But New Jersey Gov. Chris Christie defended the quarantine on Sunday. "I don’t believe when you’re dealing with something as serious as this that we can count on a voluntary system," he told Fox News. "This is government’s job. If anything else, the government’s job is to protect the safety and health of our citizens."

De Blasio, though, said Sunday that Hickox's treatment was "inappropriate." "We have to think how we treat the people who are doing this noble work," he said.