By LAURA ROMERO, ABC News

(NEW YORK) — As coronavirus cases and hospitalizations in the U.S. continue to set new records, blood centers and hospitals are sounding the alarm again over a shortage of donations amid the ongoing closure of schools, colleges and other collection locations.

Blood donations are not only important for conducting important surgeries and treating those with serious illness, but also affect the ability to harvest convalescent plasma, an antibody-rich serum made from the blood of recovering COVID patients that is used to treat those who are seriously ill.

According to America’s Blood Centers, 13 community blood centers have a one-day supply or less while 22 centers have a two-day supply or less. The organization has 59 community blood centers across the country.

The issue is particularly acute in the rural healthcare system, where medical facilities rely on blood to stabilize patients while they are transferred to other facilities.

In New York alone, high schools and colleges account for 75,000 donations each school year.

“Across our state and country, we are seeing an alarmingly low supply of blood,” said Dr, Joan Uehlinger, the director of transfusion medicine at Montefiore Health System, in a statement released by the New York Blood Center.

To prepare for the winter, a typically slow season for blood donations, the Blood Center has partnered with hospitals to increase donations. Currently, in New York, donations are at just 65% of pre-pandemic levels, well below what is needed by hospitals.

“Giving blood was as easy as skipping chemistry,” Andrea Cefarelli, senior executive director at the New York Blood Center, told ABC News. “But with school and college campuses closed as well as other locations like places of worship, there is a chronic deficit between what we need and how many people are giving blood.”

Cefarelli said she is concerned that hospitals may cancel elective surgeries, a step they took in the spring amid the initial surge in cases.

Dr. Justin Juskewitch, a clinical pathologist at Mayo Clinic, echoed similar concerns about “individuals who have cancer, individuals who need to undergo surgeries, trauma patients.”

“These are individuals who require blood transfusions,” Juskewitch said. “There’s a lot of need.”

Versiti, a healthcare organization that supplies blood in Wisconsin, Indiana and Michigan is reporting a shortage in blood supply and convalescent plasma as well (a treatment for severely ill COVID-19 patients made from the blood of those who recovered).

Last week, the organization issued an urgent plea to coronavirus survivors to donate.

Even though the company started collecting plasma early on, Dr. Dan Waxman, the vice president of transfusion medicine and senior medical officer at Versiti, told ABC News that about a month ago, distribution started to increase beyond what the company is collecting.

“We’ve had to bring in plasma from other parts of the country to meet the needs of hospitals,” said Waxman. “It’s a real problem. The demand just in the last three to four weeks has shot up exponentially.”

Paul Sullivan, the senior vice president at the American Red Cross told ABC News that the organization is also seeing a “significant” shortage of convalescent plasma.

“We are sending convalescent plasma to our hospitals at a rate faster than we’re collecting it,” Sullivan told ABC News. “So we need to obviously turn that around. Demand is high and we need more people to come out to our blood drives.”

For Dr. Jay Bhatt, a practicing internist and ABC News contributor, doctors are having to “think creatively” about blood supply to have enough for patients in need.

“The wave of blood supply shortages we are seeing is deeply concerning and pushing caregivers to the brink of not having a vital substance to save lives,” Bhatt said. “We can’t sustain more cases.”

In Delaware, Beebe Healthcare announced a partnership with the Blood Bank of Delmarva to make up for the shortfall caused by the coronavirus pandemic.

The healthcare system’s CEO, Dr. David Tam, said he is concerned about the impact blood shortages have on rural healthcare systems. He said they depend on blood to stabilize patients who are later transferred to a place with a higher level of care.

Mobile donations at the Blood Bank of Delmarva are at just 43% of pre-pandemic levels.

“Having worked in emergency rooms and trauma rooms for many years, I know there are situations where you can use your entire hospital blood supply on one patient,” said Tam. “Everyone needs to donate.”

“Blood is necessary,” said Tam. “It saves lives.”

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