Hospital leaders endorsed Gov. Tim Walz’s decision to end the statewide stay-at-home order on Monday, but urged Minnesotans to remain vigilant to reduce the spread of the COVID-19 virus that could still overwhelm them and leave them unable to care for some patients at the peak of the pandemic.

Minnesota appears to have a razor-thin margin of critical hospital supplies — including critical care beds and ventilators — to weather the surge of COVID-19 infections that is expected this summer, according to new state modeling results. But if reality proves worse than predicted, hospital officials said the governor will need to be quick about reinstituting restrictions that reduce face-to-face contact and the spread of the virus.

“We are definitely pleased that the governor has his finger on this dial and he is fine-tuning this dial — turning it up as conditions appear more favorable,” said Dr. Rahul Koranne, chief executive of the Minnesota Hospital Association. “But a dial that can be turned up should and can be turned down … if some of the metrics become concerning.”

Hospitals have dramatically increased their capacities over the past two months. As of Thursday, the state reported a supply of 1,443 ventilators in hospitals — with only 529 in use by patients with COVID-19 or other unrelated medical problems. The state also has a surge supply of 1,401 more ventilators and another 858 on back order for delivery, for a total of 3,702.

State emergency officials also have selected several alternate care sites to serve as overflow for stable, non-COVID patients if hospitals fill up and estimated that the first of those — a former long-term care facility in Roseville — should be renovated and ready by May 25.

Modeling released Wednesday by the University of Minnesota and the Minnesota Department of Health illustrated the state’s narrow margin. The scenario that most closely resembles the state’s current pandemic response predicted a peak of cases on June 29 that would require 3,397 ICU beds with ventilators. The margin of error of that estimate means that demand could exceed the state’s ventilator supply.

Walz is replacing the stay-at-home order with a new strategy branded “Stay Safe MN” that allows retailers to resume Monday with plans in place to reduce virus transmission among workers and customers, and plans for bars and salons and other service businesses to resume June 1. Group gatherings of 10 or more people would still be prohibited, but the governor also set out conditions for summer camps and school classes to resume.

The key is that Minnesotans can’t get complacent, Walz said in a radio address on WCCO Thursday morning, and must still practice social distancing, hand washing and other efforts to prevent the spread of the virus.

“The whole purpose of this was just to push this thing out, flatten it and slow down. You’re not going to prevent it,” Walz said. “I think it’s hard for people to wrap their head around [that] folks are still going to get this. The fear was, you saw this in other places, they weren’t ready and it overwhelmed the system.”

State health officials on Thursday identified new metrics they will be closely watching for signs that the pandemic is taking a turn for the worse. One bad sign would be if diagnostic testing finds positive COVID-19 cases 14% of the time, or if the rate of positive tests increases by 5 percentage points over 14 days. The current seven-day average is a positive rate of around 12%

Another threshold would be a doubling of COVID-19 cases every five days or less. The current rate is 9.5 days.

As of Thursday evening, the state health department reported 13,435 lab-confirmed COVID-19 cases in Minnesota and 663 deaths. There were 498 COVID-19 cases that required hospital care as of Thursday, including 203 needing intensive care. Of all confirmed cases, 9,136 had fully recovered and were no longer required to isolated themselves to avoid spreading the virus.

Another new key metric for the state is the share of people whose infection sources couldn’t be pinpointed to others, such as their spouses or co-workers. The current rate is 36%, which is already above the Health Department’s threshold of a seven-day average of 30% that is concerning.

“This gives us a sense of whether there is more widespread transmission in our Minnesota community,” said Dr. Ruth Lynfield, state epidemiologist.

Spikes in any of these measures could result in recommendations to the governor to consider new social distancing restrictions.

The state on Friday also expected a third shipment from the federal government of remdesivir, the antiviral drug that received emergency authorization for use against COVID-19 because clinical trials showed it shortened hospital stays. The latest shipment would provide therapy for at least 145 people, based on a 10-day course, Lynfield said.

The state has published ethical guidelines on which COVID-19 patients in hospitals should receive it first. The federal government is managing shipments of the drug, with future shipments to Minnesota based on the number of COVID-19 cases in hospitals.

U researchers were involved in the initial national clinical trial of remdesivir and recently began a second trial to see whether the drug in combination with another medication can reduce the immune-system overreactions that cause some of the worst complications in some infected patients.

Other pandemic preparations on Thursday included the activation of 20 medically trained members of the state National Guard to conduct diagnostic testing in long-term care facilities, where elderly and sick residents have suffered some of the harshest outcomes. Among all COVID-19 deaths, 537 involved residents of long-term care or assisted-living facilities.

State lawmakers on Thursday also debated a pressing issue of lawsuits against nursing homes, hospitals and other care facilities — and whether to shield them from liability for any delivery of care during the COVID-19 peacetime emergency, which started March 13. Operators of long-term care facilities support the legal protection, noting they have suffered amid the pandemic from shortages of protective gear and staff — sometimes because workers suffered COVID-19 infections and had to stop providing care immediately.

“The medical profession is taking extraordinary risks that I don’t think the public fully appreciates or understands,” said Sen. Michelle Benson, R-Ham Lake, chairwoman of the Health and Human Services Finance and Policy committee, who introduced the bill.

State health officials are hoping that the prolonged stay-at-home order not only delayed the peak of COVID-19 cases but reduced that peak number of cases as well.

Modeling by the U and the Health Department generally predicted that these restrictions only delayed the peak, but Mayo Clinic’s chief executive on Thursday said his organization’s unpublished modeling predicted a “flattening” of the peak.

“Mayo Clinic’s predictive modeling shows that the anticipated COVID-19 very high peak has been diminished, and we will experience varied levels of infection rates in the coming months until an effective vaccine is available,” wrote Dr. Gianrico Farrugia. “Based upon this data, we support the incremental reopening of public spaces in our communities.”

Staff writers Christopher Snowbeck, Chris Serres and Joe Carlson contributed to this report.