A rider waits for the L train today in New York City. Craig Spencer, a Doctors Without Borders physician who recently returned from Guinea, had taken the train before being hospitalized Thursday with Ebola.

NEW YORK — A doctor who became New York City’s first Ebola patient was praised for getting treatment immediately upon showing symptoms, and health officials stressed that the nation’s most populous city need not fear his travel in the days before his illness began.

Mayor Bill de Blasio and Gov. Andrew Cuomo urged residents not to be alarmed by the doctor’s diagnosis Thursday, even as they described his movements since returning from Guinea a week ago. De Blasio said all city officials followed “clear and strong” protocols in their handling and treatment of him.

“We want to state at the outset that New Yorkers have no reason to be alarmed,” de Blasio said. “New Yorkers who have not been exposed are not at all at risk.”

The doctor, Craig Spencer, a member of Doctors Without Borders, reported Thursday morning coming down with a 100.3-degree fever and diarrhea. He was being treated in an isolation ward at Manhattan’s Bellevue Hospital, a designated Ebola center.

New York City’s health department today confirmed the doctor’s temperature was 100.3. At a news conference Thursday night, officials had incorrectly said Spencer had a temperature of 103.

The Centers for Disease Control and Prevention has dispatched an Ebola response team to New York.

Health officials have been tracing Spencer’s contacts to identify anyone who may be at risk. The city’s health commissioner, Mary Bassett, said Spencer’s fiancee and two friends have been quarantined but have showed no symptoms.

According to a rough timeline provided by city officials, in the days before Spencer fell ill, he went on a 3-mile jog, went to the High Line park, rode the subway and got a taxi to a Brooklyn bowling alley.

He felt tired starting Tuesday and felt worse on Thursday when 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.

Health officials say the chances of the average New Yorker contracting Ebola, which is spread through direct contact with the bodily fluids of an infected person, are slim. Someone can’t be infected just by being near someone who is sick with Ebola.

Bassett said the probability was “close to nil” that Spencer’s subway rides would pose a risk. Still, the bowling alley was closed as a precaution, and Spencer’s Harlem apartment was cordoned off.

Spencer, 33, works at NewYork-Presbyterian/Columbia University Medical Center. He had not seen any patients nor been to the hospital since his return, the hospital said in a statement, calling him a “dedicated humanitarian” who “went to an area of medical crisis to help a desperately underserved population.”