The woman who arrived on Tuesday was traveling with her spouse. He is presumed to have contracted the highly contagious virus and was undergoing testing. The State would be contacting passengers on the flight and the driver of the car service that dropped them off at home.
The woman was believed to be contagious-free on the plane into New York and in the car service.
"Since they were healthcare workers, they contact Mount Sinai and took all precautions necessary," Cuomo said.
Cuomo and other state and city officials had said the emergence of a New York case was considered inevitable, given the city's role as a hub of international travel.
"In this situation, the facts defeat fear. Because the reality is reassuring," Cuomo said. "It is deep-breath time."
New York City's public laboratory will begin testing on Friday.
"If you have the symptoms, go get health care," said de Blasio on Monday. "This is not something you get through casual contact."
Health authorities had previously tested more than 30 New York patients who have reported symptoms consistent with the virus, but until now each suspected case had proven to be a false alarm.
"If you think you need care and you don't know where to turn, call 311. We will help you get to the healthcare that you need," said de Blasio.
More than 80,000 cases of COVID-19, the illness caused by the virus, have occurred worldwide since the virus emerged in China. About 3,000 people have died. The illness is characterized by fever and coughing and in serious cases shortness of breath or pneumonia.
Two COVID-19 related deaths were reported in Washington state over the weekend. Another four were reported Monday.
Rhode Island also confirmed its first case of the illness on Sunday, the same day that researchers said the virus may have been circulating in Washington state for weeks undetected.
While there is no evidence yet that the virus has been spreading in New York among people who haven't traveled, the addition of the city to the list of places with confirmed cases of the virus seemed likely to raise anxiety and potentially pose a threat to tourism.
New Yorkers and the city's millions of visitors spend their days in close proximity to each other. City officials have, for weeks, been urging people to frequently wash their hands and avoid touching their faces to cut down on the risk of catching an illness. They have also urged calm, saying repeatedly that the risk to most New Yorkers is low.
"As we confront this emerging outbreak, we need to separate facts from fear, and guard against stigma and panic," Dr. Oxiris Barbot, the city's health commissioner, said.
With the Associated Press