Mayor Bill de Blasio updates New Yorkers on the City's preparedness efforts regarding COVID-19, March 4, 2020. EuropaNewswire | Gado | Getty Images

New York City has 3,615 confirmed coronavirus cases, including an inmate at Rikers Island, Mayor Bill de Blasio announced Thursday. The possibility of COVID-19 spreading throughout the densely populated U.S. prison system has been a major concern among public officials. "This inmate was in a housing unit with other inmates, all have been checked for symptoms," de Blasio said at a press conference, adding that eight other prisoners have symptoms and have been moved to isolation in the communicable disease unit. The number of infections in New York City jumped by more than 1,000 cases in a matter of hours — since Thursday morning when New York Gov. Andrew Cuomo said there were 2,469 infections in the city and 4,152 total infections across the state.

De Blasio said Cuomo's data was pulled at midnight, accounting for the difference. He said 22 people in the city have died so far. "We're seeing an explosion of cases here in New York City," de Blasio said, adding that the city has been ramping up its testing in recent days and identifying previously unknown cases. "This number is, nonetheless, very, very painful."

554 hospitalizations

Based on roughly 2,000 cases confirmed as of Wednesday, de Blasio said 554 were hospitalized and 169 were in intensive care. On Tuesday, de Blasio told New Yorkers to prepare for a "shelter-in-place" order in the coming days to contain the fast-moving virus. On Wednesday, however, Cuomo said he won't approve a "shelter-in-place" order for New York City, which he said is legally required. Cuomo said that he is concerned about the level of fear that such policies could create. "I spent half my day knocking down rumors that we're going to imprison people in their homes," he said earlier Thursday. De Blasio said he is speaking to Cuomo later Thursday night and plans to update the public Friday. "We need to be coordinated with the state of New York," de Blasio said at the press conference Thursday. "It doesn't matter if we've had disagreements along the way, we are in a crisis together right now." New York state and other hard-hit regions across the country are rolling out social distancing policies to slow the spread of the virus so that the nation's hospitals don't get overwhelmed. "Definition really matters," de Blasio said, adding that he thought a "shelter-in-place" order was fairly clear. "I think that San Francisco model is a clear, humane, smart version of shelter in place that really keeps the essentials going but gets rid of everything non essential. I think it's a smart approach."

What is shelter in place?