COVID-19 is sweeping across Minnesota at an unprecedented pace, breaking records for new cases and daily deaths and raising concerns over the ability of hospitals to keep up.

Saturday's tally of 4,647 new cases — a figure that would have easily set a record during the first eight months of the pandemic — wasn't even close to the biggest single-day count of the past week. For the seven-day period ending Saturday, Minnesota reported more than 25,000 new COVID-19 cases, or more than 10% of the state's cases since March.

The Minnesota Department of Health reported another 34 deaths on Saturday, bringing the week's total to 168 — the second highest one-week count since the start of the pandemic. Hospitals, meanwhile, are scrambling to treat more COVID-19 patients even as the virus threatens to sideline more health care workers.

"The COVID situation has certainly accelerated over the last week and week and a half," said Dr. Pritish Tosh, medical director for emergency management at Mayo Clinic. "It's been an alarming increase."

With the Upper Midwest leading the way, the U.S. for the first time last week passed the grim marker of 100,000 new cases per day.

North and South Dakota once again led the nation Saturday for population-adjusted case growth, with readings that were significantly higher than last week, according to a tracking website from Brown University. Wisconsin and Iowa ranked fourth and fifth, respectively, while Minnesota was 14th.

"You're in the middle of the cyclone," said Dr. Timothy Brewer, a professor of epidemiology and medicine at the University of California, Los Angeles. "The critical issue right now is the very rapid growth in number of cases and case rates, and the associated, though slower, rise in deaths."

Last Thursday and Friday, Minnesota hospitals reported they were treating more than 1,000 COVID-19 patients each day — the highest volumes thus far in the pandemic. The surge is being felt across nine hospitals operated by Bloomington-based HealthPartners, said Dr. Mark Sannes, an infectious disease physician.

Hospitals are making adjustments, Sannes said, including diverting ambulances when they don't have room for new patients. But to sustain that long term, he said, the state's health care system needs case growth to slow down.

"This is the most concerned, I think, we have been in regards to capacity of the system to be able to handle what's coming," Sannes said.

At the end of last week, M Health Fairview hospitals were caring for 20 to 25% of all patients across Minnesota hospitalized with COVID, said Dr. Greg Beilman, a critical care surgeon. That's more than last spring, Beilman said, adding that the surge first appeared at greater Minnesota hospitals but is now intensifying in the Twin Cities.

COVID's spread also has affected more health care workers, who are either showing symptoms or having to self-quarantine due to possible exposure. Fairview is looking to hire traveling nurses to fill gaps and improve turnaround time on tests so healthy caregivers can get back to work faster, Beilman said.

"I'm not going to lie," he added. "This is very worrisome."

Hospitals are working together to match patients with available beds. In some cases, patients have been sent from the Twin Cities to Duluth or Rochester to create room in the metro for a patient in a rural medical center who needs more specialized care, said Dr. Rahul Koranne, chief executive of the Minnesota Hospital Association. There are plenty of hospital beds available, Koranne said, but it's getting harder for hospitals to find enough workers to staff them.

"That is a direct result of the explosive rise in this virus' transmission in our communities," he said. "The health care system in the state of Minnesota is getting stress-tested."

Saturday's one-day case count was the second highest of the pandemic so far. It came on a high volume of more than 44,738 newly completed tests, meaning roughly 1 in 10 tests came back positive. Over the past week, an average of about 12.6% of tests were positive, compared with about 6% in mid-October.

"When the case numbers are going up and positivity is going up, that should sound the alarm that the increase in cases is not an artifact of enhanced surveillance," said Jennifer Nuzzo, senior scholar at the Johns Hopkins Bloomberg School of Public Health. "It means more people are getting sick now."

Minnesota continues to expand coronavirus testing. Whereas the state's seven-day average was roughly 24,823 new tests per day two weeks ago, the comparable figure on Saturday was 33,689, an increase of more than one-third.

But the seven-day average for new cases per day during that same time span has grown at a much faster rate. Two weeks ago, the state reported an average of 1,576 new cases per day. As of Saturday, that figure more than doubled, to 3,783.

"This is not a function of more testing," said Dr. Timothy Schacker, vice dean for research at the University of Minnesota Medical School. "The larger point is: We're headed in the wrong direction, but we still have the ability to alter that trajectory."

Overall, Minnesota has reported 174,954 cases, 11,394 hospitalizations and 2,625 deaths from COVID-19. Long-term care and assisted-living residents accounted for 18 of the deaths announced Saturday and 1,818 deaths total.