Coronavirus infections linked to pre-K-12 students and staff have increased since the fall start of classes — with 820 infections reported in the week ending Sept. 11 and 859 so far in the week ending Sept. 18.

Thursday's Minnesota Department of Health update also listed 95 pre-K-12 schools with COVID-19 outbreaks of five or more infections in two weeks. The list more than tripled the 27 reported outbreaks last week and included Edison High School in Minneapolis, which shifted to remote learning because of a rise in infections this week.

While expected with the return of in-person classes, the outbreaks have increased pressure on school leaders — who are setting mask, quarantine and distance learning protocols on their own in the absence of an emergency order that empowered Gov. Tim Walz to enact statewide policies last school year.

Vaccination of more eligible people 12 and older remains the state's primary strategy to reduce outbreaks in schools, with Minneapolis Public Schools planning an Oct. 15 start of its requirement for staff to submit proof of immunization or recent negative COVID-19 tests.

"We know that vaccines are the best tool we have to slow the spread," said Doug Schultz, a state Health Department spokesman.

State guidance calls for removal of infected students from classes for 10 days and until they are fever-free, and quarantines ranging from seven to 14 days of unvaccinated close contacts that might have been exposed to the virus. Close contacts are defined as anyone spending 15 minutes within 6 feet of an infected person — except when both people are wearing well-fitted masks.

Policies vary widely, with some districts requiring masks and others such as Waconia Public Schools recommending them. Waconia — which has three schools on the state outbreak list — reviews any classroom with three infections and considers whether to require masks, quarantines or other measures to protect the room and school building.

Some advocates nationally have called for more aggressive use of rapid antigen testing to support a "test to stay" strategy being attempted in some schools. The idea involves daily testing of close contacts rather than automatic quarantines to keep them in class until their infection status is clear.

"Test-to-stay isn't just a theoretical idea," said Dr. Michael Mina, an assistant professor of epidemiology at Harvard University, in a series of tweets about the nation's underuse of testing resources. "We can do this, today, and change the toll of this virus."

Aggressive testing programs proved controversial last school year. Edina Public Schools in partnership with UnitedHealth Group launched a Test the Nest program of routine surveillance testing but found it underutilized as many families worried that it would result in quarantines for entire classrooms or sports teams.

More districts are taking advantage of state-offered testing supplies this year, though. The Minnesota Department of Education on Thursday reported that more than a quarter of the state's 2,500 school buildings have requested testing supplies, and 180 districts and charter schools have applied for grants to cover testing costs.

Education Minnesota called for continued caution against the pandemic, noting that the state on Thursday reported the first two COVID-19 deaths of school staff members this school year. Ten staff member deaths have been reported since the start of the pandemic 18 months ago.

"For at least a little while longer, our schools need to embrace masking, social distancing, vaccinations and all the other tools in the toolbox to keep schools open during the current surge of the virus," said Denise Specht, president of the teachers union.

The number of school-associated coronavirus infections the past two weeks almost doubled totals in equivalent weeks last September.

While some schools experienced earlier outbreaks that have declined — and may no longer have ongoing coronavirus transmission — they are removed from the state list only if they have reported no new infections for 28 days. The outbreaks include students and staff who might have been exposed to the virus in other locations in their communities but were infectious while in their school buildings.

Odds of severe COVID-19 are lower in children, but health officials remain concerned about the risks in students and their ability to transmit the coronavirus to older people at greater risk. Minnesota remains in the fourth wave of a pandemic that has caused 8,049 COVID-19 deaths and 694,320 known infections, including 24 deaths and 2,434 infections reported Thursday.

One of the deaths involved a Nicollet County resident age 45 to 49 while the rest involved seniors — who have made up 87% of the COVID-19 fatalities in Minnesota overall.

COVID-19 hospitalizations in Minnesota dipped slightly to 777 on Wednesday but remain above totals seen during the third pandemic wave this spring. Children's Minnesota earlier this week reported 10 hospitalized patients with COVID-19 between its Minneapolis and St. Paul campuses.

Health officials have encouraged continued COVID-19 vaccinations, especially in younger age groups with state data showing a first-dose rate of 53% in eligible people age 12 to 15, and 59% in eligible people age 16 to 17. Overall, more than 72% of Minnesota's eligible population has received at least a first dose of COVID-19 vaccine.

Jeremy Olson • 612-673-7744