No new COVID-19 cases involving the omicron coronavirus variant were reported in Minnesota on Monday, but the dominant delta variant was creating plenty of problems for the state.

COVID-19 hospitalizations in Minnesota increased to 1,570 on Friday, including 346 people receiving intensive care. The state reported a 98% occupancy rate of adult intensive care beds when including COVID and non-COVID patients, the highest in the pandemic.

Minnesotans can reduce the burden by getting COVID-19 vaccines and boosters and by limiting chances for viral exposure in gatherings and crowds, said Dr. Andrew Olson, a hospitalist and leader of the COVID-19 response for M Health Fairview. Among the 307 COVID-19 patients in the system's hospitals, 72% are unvaccinated.

"I think that life can go on," he said, "but life can't go on pretending that nothing is going on."

Minnesota leaders are watching closely for signs of a COVID-19 surge as a result of viral spread over Thanksgiving. The state's reported positivity rate of COVID-19 diagnostic testing increased for the first time in two weeks to 10.4%, keeping it above the 10% high-risk threshold for substantial viral spread. However, the rate dates back to the seven-day period ending Nov. 26, so the holiday's impact remains unclear.

The state also is monitoring for additional infections involving omicron, which was labeled a variant of concern after it was identified in South Africa because of its rapid spread and its potential ability to evade immunity from previous infection or vaccination.

"We don't yet know what impact this will have on the pandemic," said Dr. Andrew Badley, an infectious disease specialist leading Mayo Clinic's COVID-19 research task force, on Monday. "There are some reports that the disease penetration is lower with the omicron variant, meaning that people get less from it. If that's true, that's a very good thing."

On the other hand, omicron could produce so many infections that it results in more hospitalizations even if the rate of severe illness is lower, he said. Monoclonal antibody therapies might not work as well against omicron infections, though Badley said they will likely offer some benefit.

Minnesota last week reported one of the nation's first omicron cases in a Hennepin County man who traveled to New York for a convention in late November. State surveillance found seven other potential omicron cases, but genomic sequencing found that four did not involve the variant. Results for three others are pending.

The delta variant is the dominant strain in Minnesota, which had the highest rate of new infections in the U.S. over the past seven days, according to data Monday from the Centers for Disease Control and Prevention.

The Minnesota Department of Health on Monday reported another 38 COVID-19 deaths and 6,122 coronavirus infections, raising pandemic totals to 9,654 deaths and 933,025 infections.

Staffing shortages in nursing homes have contributed to the pressure on hospitals, giving them nowhere to send patients who are ready to be discharged but too frail to go home. The backup can be seen all the way into emergency departments where COVID-19 and other patients needing extended care are boarding for hours or days awaiting open inpatient beds.

"We don't have a choice right now," Olson said, "but that is much less safe than being on an inpatient unit."

The state responded Monday with the opening of a fourth alternative care site at Benedictine Living Community-Regina in Hastings. The 17-bed site will join with those in Brainerd, St. Paul and Shakopee to provide transitional care for patients after hospitalizations.

Gov. Tim Walz also announced that 50 specially trained members of the Minnesota National Guard would be arriving as early as Tuesday to support staffing at nursing homes in New Hope, Onamia and Fergus Falls. A new training program to put 1,000 certified nursing assistants into long-term care facilities by Jan. 31 was launched as well.

"We continue to deploy every resource we have available to support our overworked and understaffed doctors, nurses and long-term care staff who have been fighting on the frontlines of this pandemic for nearly two years," Walz said.

Staffing pressures have reduced bed capacity at Minnesota hospitals as well, though they reported that losses because of vaccine mandates were small. HealthPartners reported 99% compliance with its mandate for workers to get vaccinated or file exemptions. Of 133 workers put on unpaid leave for 30 days when they missed an Oct. 29 deadline, 70 met the mandate by the end of November and 63 did not return to work.

Greater Minnesota hospitals were admitting the majority of COVID-19 patients earlier this fall, but the share in Twin Cities hospitals has increased from 47% on Nov. 1 to 56%.

Mercy Hospital has been the busiest in terms of COVID-19 volumes, serving the highly populated metro area but also rural counties with low vaccination rates. The hospital averaged 122 COVID-19 inpatient cases per day in the seven-day period beginning Nov. 19 between its Coon Rapids and Fridley campuses. Two-thirds of its 31 ICU patients had COVID-19 as well.

Hospitals are delaying surgeries but also having to perform surgeries they delayed a month or two ago in the hopes that the pandemic wave would have eased by now. Dr. Ryan Else, Mercy's vice president of medical affairs, said there has been an increase in patients sent home with rehab instructions and outpatient support, including COVID-19 patients who are sent home with supplemental oxygen.

Breakthrough infections in fully vaccinated Minnesotans continue to make up a growing share of the pandemic wave. Health officials believe immunity begins to wane six months after vaccination, putting early recipients at risk and in need of booster doses.

Vaccinated people made up 42% of infections in the five weeks between Oct. 3 and Nov. 6, compared with only 31% in May through September.

The majority of COVID-19 hospitalizations and deaths involve unvaccinated Minnesotans, even though they make up only one-third of the state's population. The 133 COVID-19 deaths reported in the week beginning Oct. 31 included 85 people who were unvaccinated.

"We are starting to see a slight increase in vaccinated patients being admitted," Else said. "What we are seeing with that, though, is those patients who have been vaccinated do have much better outcomes."