New York went on alert Friday as authorities sought to calm fears among the city's 8.4 million residents after a doctor tested positive for Ebola.
Craig Spencer, 33, was rushed to the hospital with fever and gastrointestinal symptoms on Thursday, a week after returning from treating Ebola patients in Guinea with charity Doctors Without Borders.
He tested positive for the disease, which has killed nearly 4,900 people in West Africa, at Manhattan's Bellevue Hospital Center and has been placed in isolation in intensive care.
"The last word on the patient this morning is he continues to be stable," New York City health commissioner Mary Bassett told CNN.
Spencer is New York's first case of Ebola and the first in the United States outside Texas.
In Dallas, two nurses contracted the virus after treating a Liberian patient who later died of Ebola.
Health officials said the one of the two women, Nina Pham, has been declared free of the virus and will leave the hospital Friday.
Relatives of the other nurse, Amber Vinson, said she was declared free of Ebola earlier this week.
Officials in New York said Spencer had been monitoring himself for signs of the disease and called Doctors Without Borders on Thursday when his temperature rose to 100.3 (37.9 Celsius).
New York authorities said they learned from mistakes in Dallas, and were preparing for a possible Ebola case for weeks.
Officials stressed that the disease can only be transmitted by bodily fluids and that there was no risk to the public.
"It was handled exactly right. A team went out with protective gear. He was picked up. Brought to a pre-prepared isolation unit. So it couldn't have proceeded better," New York state governor Andrew Cuomo told CNN.
Fears of contracting Ebola on the streets or subway are irrational, he said.
"We feel good that we were fully prepared, there's no reason for New Yorkers to panic or feel that they have anything to worry about on the subway system, et cetera," Cuomo said.
Republican politicians have expressed outrage that the doctor took the subway the day before falling ill and gone bowling in Brooklyn. They called for a mandatory quarantine for health workers returning from Ebola-infected areas.
Politicions made fresh calls for the US administration to impose a travel ban from West Africa and quarantine those exposed to Ebola-afflicted countries.
"I think we immediately need to look at travel bans and quarantines," Republican Congressman from Utah Jason Chaffetz told CNN.
"I don't buy into the idea of a self-quarantine. That's obviously not working, and we're sending a lot of mixed signals," said Chaffetz, a member of a committee which is holding a hearing on the response to Ebola on Friday.
New York's JFK airport introduced health screenings on October 11, taking the temperatures of passengers arriving from West Africa.
Airport workers assessed travelers for signs of the illness and questioned them about their health and exposure history.
Spencer flew home on October 17, arriving via Europe, at JFK. Officials say he then made an attempt at self-isolation, taking his temperature twice a day, although he was in close contact with his fiancee and two friends.
On Friday, dozens of journalists camped outside his apartment building in West Harlem that has been sealed off.
The bowling alley he visited on Wednesday, The Gutter, announced that it had closed voluntarily on Thursday evening "as a precautionary measure." The business said doctors had informed them staff and customers were at no risk.
"We are working with the NYC health department to have the bar cleaned and sanitized under their supervision and expect to be open sometime today," it said.
The patient's fiancee and two close friends are healthy and being quarantined, officials said.