Nurses and doctors are also falling sick themselves. “The winter is traditionally a very stressful time in health care, and everyone gets taken down at some point,” says Saskia Popescu, an infection preventionist at George Mason University, who is based in Arizona. The third COVID-19 surge has intensified this seasonal cycle, as health-care workers catch the virus, often from outside the hospital. “Our unplanned time off is double what it was last October,” says Allison Suttle of Sanford Health, a health system operating in South Dakota, North Dakota, and Minnesota. Many hospitals have staff on triple backup: While off their shifts, they should expect to get called in if a colleague and their first substitute and the substitute’s substitute are all sick. At least 1,375 U.S. health-care workers have died from COVID-19.

The first two surges were concentrated in specific parts of the country, so beleaguered hospitals could call for help from states that weren’t besieged. “People were coming to us in our hour of need,” says Madad, from NYC Health + Hospitals, “but now the entire nation is on fire.” No one has reinforcements to send. There are travel nurses who aren’t tied to specific health systems, but the hardest-hit rural hospitals are struggling to attract them away from wealthier, urban centers. “Everyone is tapping into the same pool, and people don’t want to work in Fargo, North Dakota, for the holidays,” Suttle says. North Dakota Governor Doug Burgum recently said that nurses who are positive for COVID-19 but symptom-free can return to work in COVID-19 units. “That’s just a big red flag of just how serious it is,” Suttle says. (The North Dakota Nurses Association has rejected the policy.)

Short-staffed hospitals could transfer their patients—but to where? “A lot of smaller hospitals don’t have ventilators or staff trained to take care of someone in critical condition,” says Renae Moch, the director of Bismarck-Burleigh Public Health, North Dakota. “They’re looking to larger hospitals,” but those are also full.

Making matters worse, patients with other medical problems are sicker than usual, several doctors told me. During the earlier surges, hospitals canceled elective surgeries and pulled in doctors from outpatient clinics. People with heart problems, cancers, strokes, and other diseases found it harder to get medical help, and some sat on their illness for fear of contracting COVID-19 at the hospital. Now health-care workers are facing an influx of unusually sick people at a time when COVID-19 has consumed their attention and their facilities. “We’re still catching up on all of that,” says Choo, the Oregon physician. “Even the simplest patients aren’t simple.”

A nurse breaks down at ​Lenox Hill Medical Center in New York City (Kevin C. Downs / Redux)

For many health-care workers, the toll of the pandemic goes beyond physical exhaustion. COVID-19 has eaten away at the emotional core of their work. “To be a nurse, you really have to care about people,” Neville said. But when an ICU is packed with COVID-19 patients, most of whom are likely to die, “to protect yourself, you just shut down. You get to the point when you realize that you’ve become a machine. There’s only so many bags you can zip.”