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City hospitals are on the verge of running out of swabs desperately needed for coronavirus tests, according to reports and city officials.

City health department deputy commissioner Demetre Daskalakis raised the issue in an alert to city healthcare workers on Saturday.

“There is a serious shortage of the swabs used for collecting upper respiratory specimens … required for SARS-CoV-2 testing. As the swab supply continues to decline, there is a real possibility hospitals will completely run out,” he wrote in the alert.

Hospital leaders acknowledged a shortage.

“The swabs have been in short supply all along,” Terry Lynam, spokesman for Northwell Health, told The Post Sunday.

Lynam said Northwell, the region’s largest private hospital system, has a backlog of 4,000 suspected COVID-19 patients currently awaiting testing and is processing 2,600 tests a day.

The shortage has prompted the department to direct healthcare workers to be stingy in how they use the remaining swabs in their supplies.

“At this time, providers are reminded to only test hospitalized patients in order to preserve resources that are needed to diagnose and appropriately manage patients with more severe illness,” Daskalakis wrote.

Word of the swab shortage comes as Gov. Andrew Cuomo and Mayor Bill de Blasio continue to urge more testing.

City Hall couldn’t immediately say how long the Big Apple’s supply would last, but a rep told Gothamist that the supply would likely dry up in “days, not weeks.”

The city has been reaching out to medical supply companies for more swabs, but has limited options, Health Department spokeswoman Stephanie Buhle told the outlet.

“It’s a supply chain issue — more demand than there is supply in the market,” she said. “It’s not just limited to NYC or to city-run testing sites.”

On Saturday, the city received 240 swabs and 240 testing tubes from the Missouri State Health Laboratory that are being distributed to hospitals in the five boroughs.

But, Buhle said, “they will not last long.”

Daskalakis said the supply of other protective gear or healthcare workers, “remains tenuous,” but urged staffers to continue to take precautions.

“It is therefore recommended that all employees within a health care facility that is providing care to patients wear a face mask,” the alert said. “The face mask should be worn by staff while they are in the health care facility, regardless of the type of setting or service being provided.”