Here is the latest:

The patients

One patient is being treated at Bellevue Medical Center, and had a “fever, cough and a runny nose,” according to the city’s health commissioner, Dr. Oxiris Barbot.

Two others are being treated at hospitals in Flushing, Queens. They are both over 60 years old, with symptoms that include fever, coughing and shortness of breath, Dr. Barbot said.

All three had recently been in China.

The virus

The new coronavirus causes a respiratory illness whose symptoms include fever, cough and shortness of breath. Initially, it may resemble flu or a bad cold.

The virus can incubate for as long as two weeks before a person shows symptoms. During that time, there is an indication that some people can spread the virus to others.

For now, local health departments lack the ability to test for the virus, so samples have to be sent to the Centers for Disease Control and Prevention in Atlanta. The turnaround time for results is 36 to 48 hours at a minimum.

The context

In China, the number of cases has been surging since the virus began to spread late last year. Today, there are more than 20,400 confirmed cases in China, with nearly all of the more than 420 deaths in that country.

The advice

City officials have tried to reassure the public that the risk to New Yorkers is low and that the level of preparedness is high.

Still, in trying to assuage fears, city officials have at times given different guidance than scientists at the C.D.C.

At a news conference, Mayor de Blasio said transmission of the coronavirus required “substantial contact with someone who already has it,” adding that “you don’t get it” from touching a surface.

The C.D.C., however, has more cautious advice. It said it’s not clear if someone can get the virus “by touching a surface or object that has the virus on it and then touching their own mouth, nose or possibly their eyes.”