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The number of coronavirus cases in New York surged by more than 4,500 on Saturday, jolting the statewide number of infected past 11,600 on the eve of an unprecedented lockdown from Brooklyn to Buffalo aimed at containing the deadly bug.

New York City, which remained the epicenter of the nation’s COVID-19 crisis, accounted for the bulk of the alarming increase. More than 2,400 new cases were reported in the Big Apple, raising the total number of sick to 8,115, city officials said.

The virus killed at least 15 more people in the city on Saturday, officials said, bringing the death toll to 60. The day before, COVID-19 claimed 14 lives between 10 a.m. and 6 p.m., a troubling rate of more than one an hour. The statewide coronavirus death toll meanwhile exceeded 70.

Nationwide, there were more than 25,000 cases with 300 deaths, data Johns Hopkins University revealed Saturday, as New Jersey joined four other states — New York, California, Illinois and Connecticut — in imposing restrictions on movement to stop the spread of the virus.

In response to the mounting crisis — and the expectation that the grim numbers will continue to rise exponentially— Gov. Andrew Cuomo promised to purchase 6,000 new ventilators and two million virus-blocking N95 masks.

A million of the masks will be sent to health care responders in the city, and 500,000 would go to Long Island, he said.

“We are literally scouring the globe looking for medical supplies,” he said in a press conference.

Hospitals statewide have been directed to end elective surgeries and alter their space and staffing to accommodate the flood of infected.

“We are now working with hospitals to reconfigure space to get more beds and find more staff to manage the beds,’ Cuomo said.

New York is also reviewing four possible locations for temporary “field hospitals,” to be set up by the Army Corps of Engineers and operated with FEMA assistance, Cuomo said.

The four sites being mulled are the city’s Javits Center, SUNY Stony Brook, SUNY Westbury and the Westchester Convention Center.

The Javits Center could be turned into a 1,000-patient hospital in the next few days, Cuomo said.

The Army Corps has also been eyeing empty hotels and college dorms as potential medical space.

And the Navy still intends to send the USS Comfort to New York Harbor in the next few weeks, where overflow, non-coronavirus hospital cases would be treated.

New York’s goal is to increase the state’s number of hospital beds from the current 50,000 up to 70,000.

Shoring up existing hospital space — and building more — is vital.

Some 15 percent of the state’s sick have required some hospitalization — so far about 1,600 people.

In New York City, 1,160 people have required hospitalization, including 260 in an ICU.

“Every piston is firing,” Cuomo said. “Everything that can be done will be done.”

The governor continued urging all but essential workers to stay home, or at least stay apart.

A lockdown that takes effect 8 p.m. Sunday night will set tight limits on how New Yorkers shop, work, and play — all designed to minimize close contact and prevent a healthcare-system-crippling spike in cases.

That means all New Yorkers, even the young, the governor said, flatly telling young people who think they have immunity to the deadly bug: “You are wrong.”

Just over half of the state’s coronavirus patients — 54 percent — are 18 to 49 years old.

“You’re not Superman and you’re not Superwoman,” Cuomo scolded.

“You can get this virus and you can transfer the virus and you can wind up hurting someone who you love, or hurting someone wholly inadvertently,” he said.

Social distancing is vital to slow down the growth of contagion so that the state does not exhaust its medical personnel or its supply of ventilators, protective garb, and hospital space.

“We’re trying to reduce the spread to over a period of months,” Cuomo explained in a press conference.

“Over a period of months, our health care system can deal with the numbers.”

In some encouraging news the number of cases in Westchester — where the state’s first major outbreak was located — is slowing.

“That is good news,” the governor said, proof that the original “containment zone” is working. Still, there were at least 294 cases there as of Saturday.

In New Jersey, Gov. Phil Murphy signed an executive order directing most residents to stay home.

Jersey’s sick tally rose to 1,327 Saturday, with 16 deaths. That’s up from 890 cases and 11 deaths on Friday.

Both Murphy and Cuomo attributed their states’ hikes in reported infections on increased testing.

“No one is spiking any footballs, but we have been ahead of the curve on testing,” Murphy said.

“And the numbers will continue to grow.”

Further jangling area nerves, all flights were briefly suspended Saturday afternoon at airports from Philadelphia to Westchester after an air traffic controller trainee who was stationed at the FAA’s New York Air Route Traffic Control Center in Ronkonkoma tested positive for the virus.

The center, which handles high-altitude flights and flyovers, was shut for a deep cleaning.

Sunday night’s lockdown will force the shutdown of most of the state’s businesses, with the exception of grocery stores and bodegas, liquor stores, gas stations, laundromats and restaurant delivery services.

The city has appointed a “Food Czar,” Kathryn Garcia, to ensure no one goes hungry, Mayor Bill de Blasio said.

Those lucky enough to still be working in “non-essential” businesses must do so from home; and exercising out of doors was limited to such solitary, non-team endeavors as walking, biking and running.

Saturday’s sunny, low-50s weather drew crowds of New Yorkers — all eager to shake off the self-isolation blues — to the city’s parks and beaches.

“You should send these pictures to Cuomo, this place is too crowded,” one Central Park-goer shouted to a Post photographer on a west side foot path.

“I wanted to do something today with my friends,” Matt Johnson, 42, said of a birthday party he held on the sands of Rockaway beach.

Seven pals brought surfboards, a small vanilla cake and a can of Lysol.

“It’s kinda like your last meal on death row,” agreed Devin Romeo, 28, who was surfing nearby. “You are out in the sun and getting your last wave in and its bitter-sweet.”

In Washington Square Park, the virus couldn’t slow down chess players such as Sarfaraz Ahmed. “How long are you going to be in prison in your own house?” he asked. “I’ll take my chances.”

Additional reporting by Georgett Roberts, Rosemary Misdary, Sam Raskin and Bernadette Hogan and Post Wires