"We are all deeply concerned ... this is quite clear this is a fast-growing crisis", he said at a press conference. "Folks have to understand that right now, with so many New Yorkers losing employment, losing paychecks, dealing with all sorts of stresses and strains, I'm hearing constantly from people who are tremendously anxious about how they're going to make ends meet".
Residents of the affected Northern Californian counties aren't supposed to go to work unless their job is deemed essential - like health care workers - and they're only supposed to leave their homes for tasks like picking up groceries and prescriptions, or seeking medical help.
"We've never been here before", de Blasio said of the possible "shelter-in-place" order. "Any blanket quarantine would require the State action and as the Governor has said, there is no consideration of that for any locality at this time".
Commuters walk in a near-empty Grand Central Station Terminal on Monday morning in New York City.
In reality, there are doubts as to how this would be enforced: "There are so many exceptions to this quarantine, to think an officer is going to proactively stop people who are out, and go through a myriad of questions, is absolutely not realistic, San Jose police Chief Eddie Garcia told The Mercury News".
"This has to be done with the state because it's the only way it works, and if it happens, it's because the state thinks it's the right thing to do", he said. "It is not that long before we hit 10,000 cases, that is a true statement".
De Blasio said there were 814 confirmed cases of COVID-19, the illness caused by the novel coronavirus, in New York City: 248 in Queens, 277 in Manhattan, 157 in Brooklyn, 96 in the Bronx, and 36 in Staten Island. He added seven people in the city have died so far and 124 people are in the hospital.
As of Tuesday evening, more than 6,300 people in the USA had tested positive for COVID-19 and at least 108 people had died. "Ideally whatever we do we will do regionally with the other states", Cuomo said, and went on to reference yesterday's shuttering of onsite service at restaurants and bars, a measure that he undertook simultaneously with the governors of CT and New Jersey to prevent "state shopping", or people crossing state lines to pack into restaurants or night clubs.
Federal and state officials have significantly tightened restrictions on social movement in recent days as the coronavirus sweeps across the US. Various states have also closed public schools.