The mayor also gave a dire prediction that the city could be shut down through May as New York remains the nation's hotspot.
De Blasio was asked on 'Good Morning America' if the closure through May was possible.
"I think we need to be ready for that," said de Blasio. "It's just a blunt reality."
He went on to say that for about 80 percent of those who get sick, they will get symptoms like the cold or flu.
"But for 20 percent who get infected it will be tough. It will be fatal," said de Blasio
A day earlier hizzoner said he could "barely comprehend" the COVID-19 numbers for the city: 21,873 confirmed cases and 281 people dead.
Elmhurst Hospital in Queens has borne the brunt of the crisis and is getting additional staff to help cope with the caseload.
He said the city has enough medical supplies to last this week but beyond that he just doesn't know. After working with the White House and FEMA, the city should be getting about 2,500 more ventilators by next week but the mayor said that won't be enough.