An unprecedented COVID-19 surge filled Minnesota hospitals this month, but doctors are seeing fewer severely ill patients and a more manageable pandemic wave.

Minnesota reported more than 1,500 COVID-19 hospitalizations on Wednesday and more than 8,000 inpatient beds occupied altogether — levels that typically indicate overcrowding. However, a rising share of COVID-19 patients were admitted for other reasons and their mild or asymptomatic infections were discovered upon routine screening.

Half of more recent COVID-19 patients in HealthPartners' hospitals in Minnesota and western Wisconsin were such "incidental" cases, said Dr. Greg Siwek, a HealthPartners infectious disease specialist. "It's not as if omicron can't lead to some severe outcomes; it certainly can. But the number of new consults we're getting for severely ill COVID patients is definitely less than it was a couple months ago."

Even incidental COVID-19 presents challenges. Numerous patients admitted to Regions Hospital in St. Paul for inpatient psychiatric care have tested positive, restricting their access to therapy, he said.

The feared rapid spread of the omicron coronavirus variant has been as advertised in Minnesota. It produced a seven-day rate of new infections on Jan. 10 that almost doubled the previous record, and it reached its apparent peak in 31 days.

The winter 2020 pandemic wave took 60 days to reach its peak, and last spring's alpha wave took 50 days. The delta wave lumbered 150 days last summer and fall. State health officials believe the delta wave was prolonged because many Minnesotans had immunity in the fall, because of early 2021 infections and vaccinations, that waned by winter.

Booster doses have proved protective against severe illness. Sanford Health on Tuesday reported 32 of 231 COVID-19 patients in its hospitals in Minnesota and the Dakotas have received boosters. Among 29 patients placed on ventilators, 23 are unvaccinated while five had received the initial COVID-19 vaccine series and one had received a booster dose.

Minnesota ranks second among states with more than 53% of fully vaccinated residents receiving boosters, but its progress has been patchwork. The rate of fully vaccinated residents is 72% in Hennepin County and 64% in northwestern Beltrami County. The rates of vaccinated residents who have received boosters are 56% and 45%, respectively.

Exactly how many COVID-19 hospitalizations are incidental is unclear. While HealthPartners screens all incoming patients for COVID-19 unless they had previous infections within 90 days, the Sanford and CentraCare systems only test patients with suspect symptoms or viral exposures. The limited testing likely reduces their number of incidental cases.

Additional reporting in Iowa indicated on Monday that COVID-19 was a secondary cause in 404 of 929 hospitalizations.

Minnesota's strongest indicator of declining pandemic severity is COVID-19 hospitalizations requiring intensive care. ICU cases have dropped from 299 on Jan. 1 to 230 on Wednesday, even though non-ICU cases increased from 1,015 to 1,313.

ICU cases of COVID-19 pneumonia remain as severe as ever, though, with poor outcomes and high mortality rates, said Dr. Cameron Berg, an ER physician for North Memorial Health. Minnesota on Thursday reported another 57 COVID-19 deaths and 14,633 more confirmed infections.

COVID-19 diagnosed secondarily is still a problem, because it can be hard to parse the infection's underlying role in heart disease or stomach problems and even complications from traumatic injuries, he added. "Sometimes it's hard to know what is attributable to COVID and what is some other condition with COVID being coincidence, if you will."

Influenza had contributed to COVID-19 hospital crowding, but Minnesota on Thursday reported a decline in those cases from more than 100 in the last week of December to 50 last week.

Infections among doctors, nurses and other caregivers also reduced the number of staffed beds in hospitals during the latest wave. Minnesota reached a $40 million contract to provide 600 nurses and other caregivers to address those shortages. More than 100 were dispatched last week to work 60-hour weeks for 60 days at 26 Minnesota hospitals. Another 100 were expected this week.