NEW YORK – The first case of Ebola arrived in New York City on Thursday.

Mayor Bill de Blasio and Gov. Andrew Cuomo said that a doctor who recently returned from West Africa, working with Doctors Without Borders treating Ebola patients, had tested positive for the infection.

“There is no reason for New Yorkers to be alarmed,” the mayor said. “Ebola is an extremely hard disease to contract.”

He was identified as Craig Spencer, 33, an emergency physician at New York Presbyterian Hospital. He was taken to Bellevue Hospital after experiencing fever and other symptoms Thursday, less than a week after returning from Africa.

Officials said they were in contact with four people with whom he had contact since returning and that none have symptoms. One of the contacts has been hospitalized as a precaution, officials said.

“For the relevant period of time, he was only exposed to a very few people,” Cuomo said.

Officials said he had ridden subways, taken a Uber taxi and visited a bowling alley in Brooklyn, but that they did not believe he was symptomatic at the time.

“You can only get Ebola by being exposed to bodily fluids,” Howard Zucker, acting state health commissioner, said in an evening news conference. “We look forward to a quick recovery for him.”

Spencer is on the staff at New York-Presbyterian Hospital, which released a statement on Thursday night saying “he has not been to work at our hospital and has not seen any patients at our hospital since his return from overseas.”

“We are as ready as one could be for this circumstances,” Cuomo said, contrasting New York’s preparations with those in Dallas, where the first Ebola patient on U.S. soil died and two nurses were infected.

The doctor returned to the United States through JFK airport on Oct. 17 and passed all screening for Ebola, he said.

“The patient reported a fever to local health officials for the first time today,” the CDC said in a statement. The agency will conduct tests to confirm the Ebola diagnosis.

Uber, the online ride dispatch service, confirmed one of its affiliated drivers gave the doctor a ride Wednesday evening. Uber said in a statement that it had been in touch with the U.S. Centers for Disease Control as well as city health officials and was told “neither our driver partner nor any of his subsequent passengers are at risk.”

Officials sought to reassure city residents.

“New York City is taking all necessary precautions to ensure the health and safety of all New Yorkers,” a statement posted on the New York City Health and Hospitals Corporation’s website said. “The chances of the average New Yorker contracting Ebola are extremely slim. Ebola is spread by directly touching the bodily fluids of an infected person. You cannot be infected simply by being near someone who has Ebola.”

City officials say Spencer acknowledged riding the subway and taking a cab to a Brooklyn bowling alley in the past week before he started showing symptoms.

His Harlem apartment was cordoned off, and his fiancee, who was not showing symptoms, was being watched in a quarantine ward at Bellevue. The Department of Health was on site across the street from the apartment building Thursday night, giving out information to area residents.

Mayor Bill de Blasio said proper protocols were followed every step of the way and it didn’t appear the doctor had been showing symptoms for very long.

“The patient is in good shape and has gone into a great deal of detail with our personnel as to his actions the last few days so we have a lot to work with,” de Blasio said earlier in the day. “We have a patient who has been very communicative and precise and who has only been back a very short time and has been quite clear about individuals he had close contact with.”

According to a rough timeline provided by city officials, Spencer’s symptoms developed Wednesday, prompting him to isolate himself in his apartment.

When he felt worse Thursday, he and his fiancee made a joint call to authorities to detail his symptoms and his travels. EMTs in full Ebola gear arrived and took him to Bellevue in an ambulance surrounded by police squad cars.

Welch reported from Los Angeles