Death rates for patients hospitalized with COVID-19 have decreased in Minnesota since the start of the pandemic, as doctors have gained new drugs and understanding of how to treat the infectious disease.

A COVID-Net report provided this week by the Minnesota Department of Health examined outcomes of 4,356 patients hospitalized with COVID-19 through July and found that 12% had died, compared with an earlier report in May showing that 15% had died. Among those requiring intubation or the use of heart-lung machines due to breathing problems and complications from COVID-19, the death rate declined from 53% in the May report to 37%.

Doctors said these trends reflect progress made since the start of the pandemic, when there were no proven treatments for COVID-19, to a summer in which new drugs and therapies are emerging.

"It does feel like that is helping and there are fewer patients who are progressing from needing a little bit of oxygen to going all the way to the ICU," said Dr. Greg Siwek, an infection-prevention physician at Regions Hospital in St. Paul.

Treatments include dexamethasone, a steroid given to hospitalized patients that reduces the overreaction by the immune system that can be more lethal than the infection itself.

Supplies of the antiviral remdesivir have increased to the point that the drug is in broad use in Twin Cities hospitals, often in combination with steroids and experimental infusions of virus-fighting antibodies from the plasma of recovered patients.

Except for a spike in cases in late May — when more than 600 hospital beds were filled with COVID-19 patients — the pandemic hasn't caused the surges in Minnesota that overwhelmed hospitals in China and Italy at the earliest stages of the pandemic and in New York this spring.

A guiding premise of Gov. Tim Walz's pandemic response, including a 51-day statewide shutdown in the spring, was to delay and reduce COVID-19 case growth that could overwhelm hospitals.

Minnesota hospitals were able to learn from the experiences in other parts of the world that sustained these earlier COVID-19 surges, said Dr. Rob Gould, division director of critical care for M Health Fairview, which includes the COVID-only Bethesda Hospital in St. Paul. "Definitely being downstream from that initial surge helped us."

Hospitals also pivoted away from early and aggressive use of ventilators in COVID-19 patients with breathing problems to other less-intensive forms of oxygen support first.

Part of the reason for frequent ventilator use early on had been to prevent the hands-on interaction required of other forms of oxygen support that could increase virus exposure risks for doctors and nurses, Siwek said.

"Now, we're trying to prevent going on to the ventilators, giving the steroids and the other treatments a longer chance to work," he said.

The state's latest COVID-Net analysis showed that shortness of breath is the most common symptom, found among 56% of admitted patients, and that more than half reported fevers and coughs as well.

While loss of smell has been a widely discussed characteristic of COVID-19, only 5% of patients admitted to the hospitals reported that symptom.

Patients took a median time of six days after their first symptoms to seek hospitalization. The median time between symptoms and ICU admissions for patients who needed that level of care was seven days.

As of Tuesday, 304 patients were hospitalized for COVID-19 in Minnesota, and 154 required intensive care. Hospitalizations had been increasing slightly in July and August but numbers have started to level off.

State health officials see some signs that a second wave of COVID-19 cases has crested in Minnesota, where there have now been a total of 66,061 known infections and 1,721 deaths. That total included 359 newly confirmed infections and nine deaths reported on Tuesday.

The rolling 14-day average of daily confirmed cases has decreased over the past two weeks in Minnesota from roughly 700 to 600, according to the COVID Exit Strategy website.

The Health Department also reported that the positivity rate of diagnostic tests has declined from near 6% earlier this month to 4.9%. The positivity rate is an important indicator of viral activity, because it is somewhat independent of daily fluctuations in total numbers of tests performed.

The progress at least coincides with the statewide mask mandate that went into effect July 25, because it can take two to four weeks before public health strategies or other major changes in the pandemic affect the case numbers, said Jan Malcolm, state health commissioner. However, she cautioned there is no proof that the mask mandate had that impact.

"It's often really hard if not impossible to pin down precisely which interventions had which percentage of effect," she said, "but certainly the fact that we've seen a stabilization in our cases and even a trend downward certainly coincides in time with what we would expect to see from the mask mandate."

At least some of the progress in hospital outcomes is due to an increase in the proportion of patients who are younger, Siwek said. Group gatherings have increased the spread of the virus among young adults and teenagers amid efforts to reduce infections among the elderly residents of long-term care facilities who are at greater risk of complications from infection.

Among the 4,356 COVID-19 hospitalizations in the state's latest COVID-Net report, death rates varied dramatically by age. Only 2% of the 1,292 patients aged 18 to 49 died in hospital care, compared with 27% of the 706 patients 75 years and older.

Heart disease was a pre-existing condition in 30% of the hospitalized patients while 27% had diabetes and 35% had obesity.