Maria Belen-Perez had been putting off COVID-19 vaccination for months — figuring her relative youth at 36 along with mask-wearing and hand-washing would be enough — then the coronavirus found her.

Gasping to breathe, the Minneapolis woman was panicked as her 15-year-old son called for the ambulance Sept. 1 that rushed her to HCMC.

"I noticed my son's face. He was worried," Belen-Perez said through an interpreter. "I had to say goodbye to my family."

As Minnesota hospitals have filled amid a fourth COVID-19 wave in 18 months, doctors have reported something different — an increase in younger adult patients, mostly unvaccinated and usually surprised that the coronavirus hits them as hard as it does.

The median age of the state's COVID-19 hospitalizations was 65, with a typical range of 50 to 77, last winter, but it has dropped to 50 since June, with a typical range of 30 to 76, according to a September COVID-19 hospital outcomes report from the Minnesota Department of Health. An increase in younger adult patients occurred in the spring as well when a fast-spreading alpha variant of the coronavirus was circulating, but doctors said the trend is more noticeable with the faster-spreading delta variant now dominant in Minnesota.

"The age distribution is really different," said Dr. Matthew Prekker, an HCMC emergency and critical care specialist who treated Belen-Perez. "It's almost all people under 50 that we're admitting — day after day now."

Minnesota reached the weekend with some hope of a peak in the latest wave and the pressure it placed on hospitals. COVID-19 hospitalizations in the state reached 791 on Monday before declining on Thursday to 752.

Hospital leaders don't expect a peak until early to mid-October, though, based on modeling estimates and earlier delta waves in other countries. Some hospitals are deferring nonemergency procedures for the next few weeks, while all are reporting transfers of patients across the state or even out of state when their own beds are full.

The pandemic has caused 697,182 coronavirus infections and 8,076 COVID-19 deaths in Minnesota. The state has used a variety of strategies including $100 incentives to try to protect more people through vaccination. Minnesota ranks 21st among states with a first-dose vaccination rate of 74.4% among eligible residents 12 and older, according to the Centers for Disease Control and Prevention. However, the rate drops steadily by age and explains to many hospital leaders the age shift in their inpatient wards.

"The folks that haven't had the vaccine are coming in sicker and tend to be staying longer," said Dr. Jeremy Cauwels, chief physician of Sanford Health, which operates hospitals in the Dakotas and Minnesota.

Sanford's unvaccinated patients are 57 on average while its vaccinated patients are around 72 — and have other problems contributing to their hospital needs, Cauwels said. "Really, with our 57-year-olds that haven't been vaccinated, COVID may be their only problem or they may have obesity as their other big risk factor."

Belen-Perez figured her work as a housecleaner left her with few close contacts that would put her at risk for infection, but she made vaccine appointments for herself and her son after a trip last month to see relatives in Pennsylvania. Body aches started upon her return home, followed by nausea and headaches and then a shortness of breath she had never felt before.

Her son was infected as well and had mild flu-like symptoms, while her 10-year-old daughter briefly lost her senses of taste and smell. Patients coming from households full of COVID-19 seem to be another trend in the pandemic because of the ease with which the delta variant spreads.

"That was not nearly as common with some of the other variants," said Dr. Heidi Erickson, an HCMC critical care specialist, who along with Prekker has contributed to national research showing that COVID-19 vaccines remain strongly protective against hospitalizations.

Monitoring of Belen-Perez in the ER showed a telltale decline in blood oxygen levels, prompting her admission to the hospital and treatment with the antiviral remdesivir. Belen-Perez felt scared and confused, grabbing at her oxygen mask and rolling in bed — with each move causing a coughing fit and dip in blood oxygen.

"I felt like I wasn't breathing," she said. "Even when they put the oxygen on me, I felt like I wasn't breathing."

Doctors were considering placing her on a ventilator to take over her breathing when a Costa Rican medical resident spoke with her in Spanish and calmed her. The treatment team resolved to try to treat her without ventilation and prescribed the steroid dexamethasone to reduce inflammation and support her lungs.

Hospital survival odds have improved, partly because of standardized COVID-19 treatments compared with the guesswork in early 2020 — when ventilators were used early and aggressively to prevent violent coughing fits that could spread the virus to doctors and nurses.

Minnesota's first COVID-19 outcomes report in spring 2020 reported an 11% death rate for hospitalized patients, but the total for the pandemic has declined to 9% — with recent rates being even lower.

Monoclonal antibody therapies were underused in the spring and summer but have helped in the latest COVID-19 wave — with the caveat that they need to be provided within 10 days of symptom onset to work. More than 1,100 courses of monoclonal antibodies were administered in the seven-day period ending Thursday, according to federal COVID-19 hospital data for Minnesota, compared with less than 20 per week in June at a low point in pandemic activity.

One challenge is that younger unvaccinated patients tend to wait as long as possible before seeking medical attention, Cauwels said. Monoclonal therapies don't work if taken too late, "because all of that inflammation, all of that reaction to the virus, is already in their system."

Younger patients do have the advantage of youth, which generally means stronger immune systems and better recovery odds. The increase in severe illness in younger Minnesotans has coincided with a decline in the average age of COVID-19 deaths, though. A review of state death certificate data showed the average age of COVID-19 deaths in Minnesota was 80 before Aug. 1, but 71 since that time.

Prekker said one challenge in treating Belen-Perez without a ventilator was keeping her hydrated and fed without causing her to vomit or have a coughing fit. Nurses gave her protein shakes when possible, but Prekker said another benefit of youth is that patients have nutritional reserves that can last several days.

Belen-Perez spent 15 days in the hospital — including a week in intensive care — but gradually started to breathe without supplemental oxygen. She was desperate to see her children, who had been watched by a relative at home and were not allowed to visit.

"I committed a grave error in not getting vaccinated when I could have," she said.

Still feeling weak and occasionally dizzy, she planned to take some time before returning to work. Belen-Perez went home Sept. 15.

Four days later, Emanuel Moreno awoke at home in St. Paul with a pressure on his chest that left him unable to breathe. His parents had COVID-19, but mild cases perhaps because of their vaccinations, and his 9-year-old sister was sick as well.

At 26, Moreno distrusted advice about the COVID-19 vaccine and didn't think he would get sick without the shot. Speaking Friday on his fifth day of recovery at Regions Hospital in St. Paul, Moreno said he was wrong.

"I didn't think it was going to hit me like this," he said.

Jeremy Olson • 612-673-7744