(CNN) At one hospital in Lansing, Michigan, the latest Covid-19 surge is as bad as health care workers there have seen.
And it may well be the leading edge of what's coming soon to the rest of the United States.
Already 23 states have had a more than 20% increase in case numbers in just the last two weeks, epidemiologist Michael Osterholm said Wednesday. Case spikes have hit the Northeast -- where governors are calling in the National Guard to help -- and surges in the Upper Midwest have been "dire," he said.
"We expect to see other areas of the country also light up in the next several weeks," Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told CNN's Erin Burnett.
Here's what you need to know about the surge underway now at Sparrow Hospital in Michigan's capital:
The vast majority of nurse Danielle Williams' Covid-19 patients are not vaccinated -- and had no idea they could get pummeled so hard by the virus, she told CNN.
"Before they walked in the door, they had a normal life. They were healthy people. They were out celebrating Thanksgiving," she said. "And now they're here, with a mask on their face, teary eyed, staring at me, asking me if they're going to live or not."
Michigan this week had more patients hospitalized for Covid-19 than ever as hospitalizations jumped 88% in the past month, according to the Michigan Health & Hospital Association.
"We're seeing more people die at a rate we've never seen die before," said Jim Dover, president and CEO of Sparrow Health System.
"Since January, we've had about 289 deaths; 75% are unvaccinated people," he said.
Of the very few vaccinated people who died, all were more than six months out from the last shot of their initial Covid-19 vaccine regimen, he said.
"So, we've not had a single person who has had a booster shot die from Covid."
Health experts say the best protection against Covid-19 is to get vaccinated and boosted. Only about 64.3% of eligible Americans had been fully vaccinated as of Thursday, while less than a third of those eligible for boosters had gotten one.
Among the new Covid-19 victims, nurse Katie Sefton has noticed a disturbing trend.
"We're seeing a lot of younger people. And I think that is a bit challenging," said Sefton, a 20-year nursing veteran.
She recalled helping the family of a young adult say goodbye to their loved one.
"It was an awful night," she said. "That was one of the days I went home and just cried."
Influenza is much more active this year than last year, putting a strain on hospital beds, officials in Michigan told CNN.
Heightened safety precautions against Covid-19 last year helped stymie the spread of the flu, said Dr. Mark Rosenberg, president of the American College of Emergency Physicians.
"Last year, more people staying home and covering their faces when they did go out kept flu numbers historically low," Rosenberg said in a written statement in September. But "this year the situation could be dangerously different."
Covid-19 and the flu can attack the lungs, potentially causing pneumonia, fluid in the lungs or respiratory failure, the US Centers for Disease Control and Prevention said. Each illness can also cause sepsis, cardiac injury and inflammation of the heart, brain or muscle tissues.
The emergency department at Sparrow Hospital has been overwhelmed for over a month, Chief Medical Officer Dr. Karen Kent-VanGorder told CNN.
"Perpetually, we have had ... emergency department patients in our emergency department that need to be on the floors," she said. But "we're stepping on the hose up here. There's nowhere for them to go."
Across Michigan, most hospitals and health systems have gone to code-red triage, meaning they won't accept transfers, Dover said.
"And as we go into the holidays, if the current growth rate that we're at today (holds), we would expect to see 200 inpatient Covid patients by the end of the month -- on a daily basis," he said. And that would mean "absolutely stretching us to the breaking point."
"We've already discontinued inpatient elective surgeries," Dover said. "In order to create capacity, we took our post-anesthesia recovery care unit and converted it into another critical care unit."