City, state, and federal officials are urging New Yorkers to remain calm after a Manhattan doctor was diagnosed this week with the city's first confirmed case of Ebola.

Speaking to reporters Friday at the Office of Emergency Management's headquarters in Brooklyn, Mayor Bill de Blasio reiterated the disease can not be contracted casually and that city residents should go about their business as usual.

The mayor referred to the situation as being a "health crisis" and that all people suspected of being at risk for Ebola must cooperate. He also urged all city residents to get a flu shot in order to reduce the number of cases of people who might display symptoms similar to Ebola.

"It sounds counter-intuitive at first, but it's very important because when you have the flu, it can seem like some of the same symptoms as Ebola," de Blasio said. "Every New Yorker who gets a flu shot, not only does it help prevent flu for them and their family, it also helps our medical teams.

The mayor's remarks come as Dr. Craig Spencer undergoes treatment at Bellevue Hospital.

The 33-year-old had been working with Ebola patients in the West African country of Guinea and returned to the U.S. on Friday, October 17.

City officials say Spencer called 911 around 10 a.m. Thursday after developing a 100.3-degree fever, not 103 as was first reported, and was taken to Bellevue, where he was placed in isolation.

His Ebola diagnosis came back later that night and has since been confirmed by the Centers for Disease Control.

"We know that the patient continues to be stable at Bellevue Hospital, where he remains hospitalized on the isolation unit in an intensive care unit setting, and so we are pleased that he continues to remain in stable condition," said city Health Commissioner Dr. Mary Bassett.

Ebola is transmitted only when someone shows symptoms, and city Health Commissioner Dr. Mary Bassett says Spencer displayed no symptoms throughout his travels or while making his way around the city.

City health officials stressed that Spencer took his own temperature twice daily since returning to the city last Friday JFK airport and being screened there.

They also say his low-grade fever of 100.3 likely means he was not highly contagious, although officials are still trying to track down people he may have come into contact with.

Bassett says on October 21, Spencer walked the High Line, visited the nearby Blue Bottle coffee shop and ate at The Meatball Shop on Greenwich Street.

The next day, he went for a run along Riverside Drive and visited a Williamsburg bowling alley called The Gutter.

"We are aware that he went on a three-mile jog, a sign that he was feeling quite well, and he also took the subway system. We know that he's ridden on the A train, the number 1 train, the L train," Bassett told reporters Thursday.

City officials say the coffee shop and bowling alley have both been evaluated and cleared.

The Gutter was expected to reopen Friday evening.

Health officials also assessed The Meatball Shop location Friday and gave it the all-clear to reopen.

Spencer's fiancee and two friends have also been quarantined but have not shown any symptoms.

As city officials addressed the ongoing safety efforts, Governor Andrew Cuomo joined New Jersey Governor Chris Christie on Friday to outline new protocols when dealing with people flying in from West Africa.

They include an automatic 21-day quarantine for any at-risk travelers who have had contact with someone infected with Ebola. Others will have a protocol developed to fit their particular circumstance.

New York and New Jersey are two of five states with airports accepting flights from West Africa.

Cuomo says they talked to the CDC and agreed that states have the right to establish their own guidelines for the screenings.

"We believe it is in the state of New York and state of New Jersey's legal rights to control access to their borders. We will establish an interview and screening process to determine an individual's risk level by considering the geographic area of origin and the level of exposure to the virus," Cuomo said.

"These actions that were taken today I believe are necessary to protect the public health of the people of New Jersey and New York and at the state level of both states," Christie said.

The scene outside Bellevue Hospital, where Spencer is being treated, was one of intense media interest, even as passersby described mixed reaction to the first day after news of the city's first Ebola case. 

"Relatively normal, yeah," said one passerby. "There are a lot of people out, a lot of people taking public transportation, acting normal. You don't see people sort of avoiding a lot of different things."

"There's unwarranted anxiety," said another. "I came down here. I gave a lecture this morning. Everyone was very calm."

"I'm scared," said a third. "You never know who got it."

Meanwhile, the first nurse infected with Ebola after treating a patient in Dallas is said to have been cleared of the virus.

The National Institutes of Health said Nina Pham would be released from the hospital Friday.

The 26-year-old arrived to the medical center last week after being flown from a Texas Presbyterian Hospital in Dallas.

Pham is one of the two nurses in Dallas who became infected with Ebola while treating Thomas Eric Duncan.

Duncan died of the virus on October 8.

Across the globe, the West African nation of Mali has confirmed its first case of Ebola.

The country's health minister says the patient is a 2-year-old girl from Guinea, where the Ebola outbreak started last December.

This makes Mali the sixth African country affected by the virus.

The World Health Organization says the disease has killed more than 4,800 people throughout the region and infected nearly 10,000.