School officials across the state are wrestling with one of the thorniest questions in pandemic-era education — at what point should they close classrooms in favor of distance learning to slow the spread of COVID-19?

Despite state guidelines to help school districts decide whether or when to switch to hybrid or full-time remote learning models, the recommendations are nonbinding, leaving it to district administrators to make the final call amid ever-shifting medical science and fluctuating daily COVID-19 case counts.

"It puts schools in a bind," said Dr. Beth Thielen, assistant professor of pediatrics at the University of Minnesota Medical School. "As things are changing very rapidly, they are having to adjust course very rapidly, and I don't envy them that task of having to change their education plans for every few weeks, based on where things are."

The Mankato district, home to 8,700 students, kept all 19 of its schools fully or partly open throughout September despite being in a county considered a COVID-19 hot spot.

Even when Blue Earth County jumped to 57 positive cases per 10,000 residents midmonth, district Superintendent Paul Peterson opted not to close schools after reviewing up-to-the-minute information that showed case rates declining. The county's case rate dropped to 35 per 10,000 residents the following week.

"We were fairly confident that the [next week's rate] was going to be lower, and it was," Peterson said, noting that the team that advises him on the issue monitors county-level infection rates and district-level data daily.

He said the team also knew that recent mass-testing events in the area might be skewing the state's numbers higher.

Looking ahead

"We also have data from the next 14-day outlook … that will be reported a week from today, and those numbers will decrease again," Peterson said late last week. "So it's that that makes us more comfortable staying in our hybrid learning model."

Like Peterson, district administrators across Minnesota are evaluating data and making changes daily.

Last week, Brainerd High School switched from classroom to distance learning for 14 days following a cluster of COVID-19 cases at the school. And Sauk Rapids-Rice Public Schools, spotting an increase in virus spread, moved its elementary students to distance learning and its middle and high schools to a hybrid model, with students working part time both at home and in the classroom. The case rates in the counties where each school district is located were lower than those in Blue Earth County.

Farther north, the 400-student Wrenshall School District, southwest of Duluth, moved entirely to distance learning until at least Nov. 8. The decision was made after a high number of staff members and students fell ill with COVID-19 symptoms, Superintendent Kimberly Belcastro said in a letter to parents. Wrenshall is in Carlton County, which last week showed a case rate of fewer than 7 per 10,000 residents.

The rates are a bit higher in Hennepin and Ramsey counties, where all Minneapolis and St. Paul public school buildings are closed to in-person learning. Hennepin County has reported 15 positive cases per 10,000 residents, while Ramsey's rate is 13 cases per 10,000.

Surveillance is key

Medical experts say the decision to shift to distance learning should be influenced by how well a school can track COVID-19 symptoms. That includes daily monitoring and the ability to test many people and quickly learn results.

Knowing whether a case is isolated or part of a cluster can make the difference between needing to quarantine several people, a classroom, or an entire school.

"It really depends on how good your surveillance is at your school and how comfortable you feel that you have truly identified all the cases that are there," the U's Thielen said. "You could have many rounds of transmission before it came to anyone's attention, if you're not looking for it carefully."

With the school year only several weeks in, it's too early to know whether in-person learning is leading to greater virus spread, given its incubation period of two to 14 days, said Dr. Ruth Lynfield, the state epidemiologist. But experts are watching the data closely.

Outbreaks in child-care centers, which opened months earlier than schools, have shown that undetected clusters can readily spread among kids and adults.

At a small day care in Salt Lake City, an 8-month-old child gave its parents COVID-19 after showing mild symptoms June 15. Contract tracers determined the child was the third in an infection chain that began with an employee who last worked at the day care May 29.

In the same city in June, an outbreak at an 84-person day care infected 10 kids and five staff members. One mother was hospitalized after being infected by her asymptomatic child. The virus spread from child to child, children to adults and adults to children.

Those examples, from the CDC's MMWR publication this month, provide more context about kids' transmission risks, since other studies have shown children are less likely to get the virus, have symptoms or spread it to others.

Statewide, children 14 and younger have made up 7% of the state's 97,638 lab-confirmed cases of COVID-19, and one of 2,015 deaths.

Since the start of the pandemic in Minnesota, children 14 and younger have accounted for about 6% of the diagnostic tests given and about 6% of the positive results. Teens 15 to 19 make up 6% of the tests given and 9% of the state's cases.

Other data also show younger children appear to be less likely to transmit the virus.

Transmission trends

One widely noted study analyzed 10,592 household contacts of all ages in South Korea and found children 9 and younger spread the virus 5% of the time, less than half the average of all age groups combined (11.8%). But that study was done while schools were closed and included only a small number of contacts from the youngest children.

"It does seem like in households, an adult is more likely to pass it on to a child than vice versa," Children's Minnesota pediatric and infectious disease physician Anupama Kalaskar said. "But I wouldn't say that is definite by any means."

Older children are more likely to transmit the virus, which is reflected in distance-learning trends.

In Minnesota, about half of K-5 classrooms are doing in-person education, while only a third of middle schoolers and a quarter of high schoolers are doing so, according to the state Education Department's Safe Learning Model Dashboard.

It's still not known why children tend not to suffer severe effects if they do catch the virus. Clinical data and public-health planning show the younger children are, the lower their chance of needing hospitalization or intensive care. One explanation could be that children have fewer underlying health problems and can more easily recover.

But children are not the only ones in classrooms who may be exposed to the virus. Educators worry about their own health and that of their families, too.

"If we're not careful enough as educators, the consequences are terrifying," said Denise Specht, president of Education Minnesota, the state's teachers union. "Everyone wants to feel safe at work, but that's very hard for educators in the classroom right now. What we know, or think we know, about the risks of COVID-19 in schools keeps changing."

Joe Carlson • 612-673-4779