Coronavirus infections linked to pre-K-12 schools have surged in the first month of classes, but health and education leaders remain confident that Minnesota can weather the latest pandemic wave with more mask-wearing and testing and fewer building closures and quarantines.

The Minnesota Department of Health on Thursday reported 1,973 infections in pre-K-12 buildings in the week ending Sept. 25, and 2,525 in the week before that — the highest totals since the start of the pandemic. The state also reported 405 outbreaks in which five or more students or staff members were in the same school building while infectious over a two-week period. That is an increase from 232 last week.

Gov. Tim Walz on Wednesday visited Carver Elementary School in Maplewood to highlight its testing and other strategies for reducing viral spread. The school, along with others in the North St. Paul-Maplewood-Oakdale District 622, requires mask-wearing and installed air purifiers in classrooms. It also uses surveillance testing every two weeks for staff members to spot any unknown infections and provides rapid take-home tests to students with suspicious symptoms and to members of their households.

Keeping schools open and children safe "are not mutually exclusive," Walz said. "They [both] can be done. We've learned a lot in the last 18 months."

While children are at lower risk of severe COVID-19, Walz said that coronavirus infections contributed to an "unacceptable" crowding of hospitals that left Minnesota with only two open pediatric intensive care unit beds at one point last week. State leaders also are concerned that children at lower risk can carry the virus to people at higher risk and increase Minnesota's toll beyond the current 732,001 coronavirus infections and 8,275 deaths.

The total includes 2,674 infections and 32 deaths reported on Thursday in Minnesota, which a month ago had one of the lowest infection rates in the country but now has one of the highest as other states emerge from severe COVID-19 waves fueled by a fast-spreading delta variant.

Despite the surge in pre-K-12 infections, schools haven't been as quick to close buildings or switch to full or hybrid distance learning models. Edison High School in Minneapolis and Vaughan-Steffensrud Elementary School in Chisholm returned to in-person classes this week following brief closures in response to viral activity. Quarantines of varsity teams that cancel seasons or games haven't been occurring as much, either.

Access to COVID-19 vaccine is a key reason, said Christine Tucci Osorio, district 622 superintendent. "Athletes take that very seriously because they want to be able to continue to play. When students are exposed, if they've already been vaccinated, they aren't out of the picture now because they're … protected."

The first-dose COVID-19 vaccination rate among Minnesotans 12 and older is 72.6%, according to state data, but remains below 60% in the 12 to 17 age group that is eligible for the Pfizer vaccine.

Walz said he expects eligibility to drop to age 5 by November. Pfizer on Thursday applied for emergency use authorization from the Food and Drug Administration to provide vaccine to this younger age group.

Walz commended schools such as Carver and predicted that broad use of COVID-19 testing will reduce quarantines and school closures.

"This building has done it," he said. "Those kids are in there learning and they are about as safe as we can make them. In about three weeks, we can make them a lot safer when we're going to be able to get the vaccine to them."

Walz no longer has the power under an emergency order to set school COVID-19 response policies, so districts have made their own plans.

The variation shows even among Minnesota's 60 largest districts. Thirty-seven of them have universal indoor mask-wearing requirements in effect while 13 do not. Another 10 limited their mask requirements to lower grades or buildings with high infection rates.

Centennial Public Schools requires masks for at least 10 days in schools with 5% rates of COVID positivity or illness, for example, while the Faribault district requires them in all schools until the local community infection rate drops below the substantial risk level.

Outbreaks have emerged in districts regardless of mitigation levels, partly because the threshold of five infections is low for schools with hundreds or thousands of students. Three outbreaks were reported in the 622 district despite its lauded efforts.

More outbreaks could be a function of more aggressive testing, but that is a worthwhile trade-off for early identification of infections before they spread widely, said Kelly Ayd, health services supervisor for the 622 district. "The more we know, the better we can fight the virus."

The district tests teachers and staff for COVID-19 regardless of symptoms using saliva molecular diagnostic tests, which take longer to produce results but are better at finding infections in people without symptoms. It then uses the BinaxNOW rapid antigen tests provided by the state to quickly identify whether sick kids are infected with the coronavirus.

Walz urged more districts to take advantage of free state test supplies, especially the rapid antigen test that has a slightly higher error rate but can provide instant information so that students and their close contacts aren't waiting.

"It's peace of mind," he said. "What we have found is the psychology of being able to test in your home and get results almost instantly [means] more people will do it."

More than 800 of 2,500 school buildings have requested free testing supplies from the state, and two-thirds of Minnesota school districts and charter schools have requested grants to cover testing costs.

Rochester Public Schools will be among the first in Minnesota later this month to try a "test-to-stay" approach to reduce quarantines for unvaccinated students in close contact with infected classmates. Close contacts at select schools can take rapid tests each morning at home and return to class if the results are negative. Otherwise, they need to quarantine.

The key as districts pursue unique testing strategies is for leaders to be clear about the goals with students and parents — who became suspicious and reluctant over testing last year when it resulted in so many quarantines and class disruptions, said Dr. Ethan Berke, chief public health officer for UnitedHealth Group, who evaluated testing programs last school year in Edina and Washington, D.C.

"The ones that are successful," he said, "are way up front in talking about the why."

Staff writer Glenn Howatt contributed to this report.

Jeremy Olson • 612-673-7744