Mayor Bill de Blasio, urging calm, strategized Thursday with top city officials on how to detect and contain any potential Ebola virus infection in New York City.

Meeting for almost two hours at City Hall, they hashed out "what-if" scenarios for handling a local outbreak of Ebola, which the World Health Organization says has already killed 3,800 people globally, nearly all in West Africa. On Wednesday the virus claimed its first fatality in the United States, a traveler from Liberia in Dallas.

"We now face the possibility of being affected by a pandemic," de Blasio said.

Dr. Mary Bassett, New York City's health commissioner, emphasized that there have been no known cases in the city, and that the virus is transmitted only by direct contact with the bodily fluids of a sick person.

Since July 31, the city has screened 88 people worried they contracted Ebola, but none of them did.

Most had no serious illness, but eight had malaria and one had typhoid. Only one patient's symptoms and recent personal history warranted an Ebola test, and it came back negative.

Participating in the City Hall meeting were dozens of city officials from agencies overseeing health, police, jails, housing, sanitation, education, emergency management and more, as well as the U.S. Department of Homeland Security. On speakerphone was a representative from the U.S. Centers for Disease Control and Prevention.

The team discussed four or five scenarios -- such as a passenger on a city-bound plane from West Africa who is sick with fever and vomiting, said Joseph Esposito, the city's commissioner of emergency management.

"The devil's always in the details, and when we go through step by step, we always identify things that we need to think more about," Bassett said.

Bassett said one of the take-aways from the meeting was the need to plan for caring for a child of a potential Ebola carrier while the parent is tested.

Officials urged anyone with Ebola symptoms -- fever, nausea, diarrhea -- who has traveled to the affected region of Africa in the last three weeks, or had contact with an infected person, to go to a hospital emergency room immediately or call 911.

"Diagnose. Isolate. And treat," de Blasio said. "It's a straightforward protocol."

All major city hospitals have isolation units to quarantine a person suspected of being infected.

Starting Saturday, screeners will question travelers arriving at Kennedy Airport from the affected region and take their temperature. The screening process is set to expand to other airports, including Newark Liberty.