The doctor diagnosed with Ebola on Thursday in Manhattan is in stable condition, authorities say, and is talking to public-health workers as they try to trace his steps in recent days.

Craig Spencer, a doctor who had been caring for Ebola patients in Guinea, returned to New York a week ago. He reported a fever on Thursday morning and was isolated and transported by a special unit wearing personal protective gear.

Even as “disease detectives” work to determine who Spencer may have encountered and check the coffee shops and restaurants he visited, officials stressed that they felt they had the situation contained and urged calm among residents.

“New Yorkers who had not been exposed to an infected person’s bodily fluids are simply not at risk,” New York Mayor Bill de Blasio (D) said during a briefing Friday afternoon. “There is no reason for New Yorkers to change their daily routine in any way.”

Spencer “poses no threat to others,” de Blasio added.

The ongoing treatment for Spencer at Bellevue Hospital involves giving him fluid and electrolytes and monitoring his vital signs, said Ram Raju, head of the city’s Health and Hospitals Corporation. Spencer remains in good enough shape to talk on the phone and tell the disease detectives from the health department about his steps so far this week.

Spencer had “valiantly volunteered to work in Guinea,” Mary Bassett, the New York City health commissioner, said Friday during the same briefing. Since returning, he has been self-monitoring and taking his temperature, first reporting a fever of 100.3 degrees on Thursday morning, she said.

Ebola patients are only contagious when they have symptoms. Even though Spencer had no known symptoms before Thursday morning, Bassett said that authorities are working to trace his every movement since 7 a.m. Tuesday.

Disease detectives with the Health Department have visited and cleared a Blue Bottle Coffee location on the High Line in Manhattan and The Gutter, a bowling alley and bar, in Brooklyn, she said.

A restaurant called the Meatball Shop is still being assessed and is expected to reopen by 6 p.m. if it is cleared, she said.

It is still not known how Spencer contracted the illness, Bassett said. “We may never know how he became infected,” she said.

The Centers for Disease Control and Prevention, which dispatched a rapid response team to New York late Thursday night, said Friday that it had confirmed the positive Ebola test in its Atlanta laboratory. This followed a separate test conducted in the New York City Health Department’s facility a day earlier.

Because he had originally flown out of Guinea, stopping at Brussels along the way, Spencer was screened at John F. Kennedy International Airport on Oct. 17 using the enhanced screening measures put into place earlier this month. He had no fever at the time.