The prevalence of respiratory viruses is making it tough for Minnesotans to know the cause of their illnesses this winter — and straining the state's hospital capacity.

Thursday's weekly update showed that Minnesota had 8,308 occupied inpatient hospital beds Dec. 1. Overcrowding has been higher on only 14 other dates since the COVID-19 pandemic emerged in early 2020. The number declined to 8,138 Tuesday, but that remained above the 8,000-bed threshold that suggests scarcity.

Preliminary infection numbers after Thanksgiving make it unclear if another surge of patients may be coming — and whether influenza, RSV, COVID-19 or something else could be the driver.

"It is going to be a confusing respiratory infection season. Figuring out what's making people sick is going to be a conundrum," said Dr. Sandra Fryhofer, chair of the American Medical Association, earlier this week.

Flu-related hospitalizations in Minnesota dipped from 559 in the last full week of November to 501 in the week ending Dec. 3. But even that number is high for this time of year, before the usual surge in communicable illness during the holiday season.

Influenza-like outbreaks declined in schools in the first week after Thanksgiving break, but the 12 outbreaks that occurred in long-term care facilities suggest the virus is finding its way into new vulnerable populations.

Viral spread was so rapid in pediatric populations this fall that it might have peaked. Hospitalizations in the seven-county Twin Cities metro area caused by RSV, a respiratory virus harsher on infants, dropped from almost 200 four weeks ago to about 120.

Knowing which infection is at fault can be important for elderly people and others at elevated risk of severe illness, who should seek testing to receive appropriate antiviral treatments for flu or COVID-19, said Dr. Laurel Ries, a family practitioner at M Health Fairview's Rice Street Clinic in St. Paul.

Others should call doctors or seek virtual visits rather than clog up clinics and emergency rooms, said Ries, president-elect of the Minnesota Medical Association.

"If you're young, you're healthy, you are feeling crummy but doing OK, it really doesn't matter which one of these you have, because we're not going to treat it any different," she said. "And at every level of health care right now, there is terrible access."

COVID levels are gradually rising after being stagnant this summer and fall, according to Thursday's pandemic update. On Tuesday, the 616 patients diagnosed with COVID in Minnesota hospitals was the most since Feb. 22. Coronavirus infections confirmed through testing at clinics and state centers increased to at least 900 per day last week, a rate last seen in September that excludes results of at-home tests.

Sewage sampling last week at the Metropolitan Wastewater Treatment Plant in St. Paul found a 24% increase in viral load compared to the prior week, the highest readings since July.

Causes of these illnesses are tough to identify by symptoms. The flu produces higher fevers, but so does strep throat. Loss of taste and smell are COVID signatures, but they don't occur in all cases and have been rare this year.

"I've been doing this for a lot of years, and I don't think I've gotten any better, nor do I think anyone realistically has gotten any better, at distinguishing these on clinical grounds," said Dr. Beth Thielen, an adult and pediatric infectious disease specialist at M Health Fairview's University of Minnesota Medical Center.

"There is so much disease around right now," Thielen added. "We're seeing more people coming in with multiple things going on," such as RSV and influenza in the same patient, or infections from parainfluenza or rhinoviruses that aren't identified as often through tests.

The state has identified 28 influenza deaths so far among people with a median age of 79; none were children. The circulating A viral strain appears well-matched to the vaccine, so doctors encouraged people to seek shots ahead of holiday celebrations. Full immunization usually occurs two weeks after the shot.

COVID risks remain concentrated in the elderly, especially compared to fall 2021 when the delta variant exploited immunization gaps in Minnesotans and increased deaths among younger adults as well. The state has identified 218 COVID deaths so far in November — the highest monthly total since February — and 94% of the victims were seniors.

People who are sick can reduce viral spread by staying home and particularly avoiding the very old and the very young, said Dr. Ashley Strobel, an emergency medicine physician at Hennepin Healthcare who specializes in pediatrics.

In mild cases, knowing which virus is at fault is less important than following basic public health guidelines and home remedies, she added.

"The important part is recognizing that you or your child has a virus so that you can do what you can to take care of yourself and your child," Strobel said. "Hydrate, reduce fever, and for little children suctioning the nose makes a big difference."