New county COVID-19 data shows what a difference a week can make — with 27 counties seeing enough changes in the spread of the infectious disease to end up in different categories when it comes to school reopening plans.

The changes underscore the volatile nature of COVID-19 numbers at the local level, amid a pandemic that has caused 58,640 lab-confirmed infections and 1,636 deaths in Minnesota, and the challenges school districts face in sizing up infection risks for the fall.

Gov. Tim Walz acknowledged the difficulties during a press event Thursday in which he lamented that his son will start eighth grade with online instruction in St. Paul; engaged a teacher in an impromptu exchange about her fears; and asked Minnesotans to maintain the mask-wearing and social distancing that can help keep businesses and schools open.

“I would tell teachers, students and parents, I wish there were more certainty around this, but the virus is not allowing us that,” the governor said. His comments came after he visited the Community Action Partnership of Ramsey and Washington Counties on Thursday to highlight state benefits and assistance programs that remain available to Minnesotans as the $600 weekly federal unemployment benefit ends.

Lincoln County saw its 14-day case rate per 10,000 people decrease from 70 last week to 40 in updated data released Thursday. That moved it under the state’s new school reopening plan from a recommendation for only online instruction to at least a hybrid approach of in-class and online learning for elementary school students.

Meanwhile, Norman County in northwestern Minnesota saw its rate bump up from nine to 15 — enough to switch from a recommendation of in-person learning in all schools to a hybrid approach in middle and high schools.

When Walz announced his school reopening plan last week, he urged people to not dwell too much on the county numbers, even though they offered guidance to local school districts on what to do. His plan offered a graduated scale of recommendations from all in-person classes in schools in counties with case rates of less than 10 per 10,000, but all online instruction in counties with case rates of 50 or more per 10,000.

Other circumstances are a factor, the governor said, including whether social distancing of 6 feet can be adequately maintained.

“If you’re in an old building with narrow halls, you may not be able to do it,” Walz said during an exchange on Thursday with a teacher.

Ellen Gurrola, an eighth-grade science teacher in the Anoka-Hennepin School District, came across the press event while taking her 2-year-old son to the dentist.

“Governor Walz!” she called out from the street. “I’m a teacher and I’m scared!”

Walz walked over and listened as Gurrola expressed frustration about getting information.

“Some teachers in districts are frustrated right now because we feel like we’ve become the enemy when just asking for safe returns,” Gurrola told reporters after talking with the governor. “It’s hard because, when we ask these questions — how it’s going to happen — the answers aren’t very clear.”

The Anoka-Hennepin School District is the state’s largest and has elected for hybrid instruction of online classes three days a week and in-person classes two days a week for all students.

That approach conforms to the state recommendations for schools in counties with case rates between 20 and 30. The latest Hennepin rate is 23 but the Anoka rate is 17.

One challenge is assessing the availability of teachers and other staff members who have health or other reasons for not wanting to return to school buildings. The majority of deaths from COVID-19 in Minnesota have involved people who are 70 or older or who have underlying health problems such as diabetes and heart disease that exacerbate COVID-19.

The district so far has received requests from 600 of 8,000 workers to either be placed on leave or to work only from home due to personal needs or their caregiving of others at heightened risk for COVID-19 complications.

The school district will finalize a plan in the next two weeks once it knows how many workers opt out and how many students decline in-person learning and need online instruction only, district spokesman Jim Skelly said.

In comments to reporters, Walz said the state was right to leave reopening decisions to local school districts, but one negative consequence is that schools come to answers at different times and messages can get confused.

“It’s distressing when you hear stories of teachers who right now should be thinking about getting back in that classroom — and the joy of those faces that first day — they’re worrying about how to stay safe in their classroom and keep their [children] safe,” Walz said. The governor said despite his initial reaction to the decision by St. Paul Public Schools, he trusted leaders were making the best decision they could with available data.

The COVID-19 pandemic is caused by a highly infectious coronavirus that causes mild or no symptoms in most cases but severe breathing problems and respiratory symptoms in others.

The Minnesota Department of Health on Thursday reported 867 new lab-confirmed infections and seven deaths. The state on Thursday also reported that 319 Minnesotans were hospitalized for COVID-19, including 153 who needed intensive care.

County case rates generally increased over the last week in the state’s most populous counties — with Sherburne County showing an increase from 15 new cases per 14 days per 10,000 people to 23.

Case rates increased only slightly in Hennepin and Ramsey counties, where Minneapolis Public Schools and St. Paul Public Schools have already opted to start the school year online.

Counties with small case numbers and populations are expected to see rapid changes in COVID-19 rates from week to week. Lincoln County officials had expected their numbers to decline this week after recovering from an outbreak last month that had been tied to a campground concert.

No additional cases have been linked to the North Star Stampede rodeo that owners held in Itasca County in late July in disregard for state capacity and social distancing requirements — and with many attendees not wearing masks. One person at the event tested positive for the SARS-CoV-2 virus.

The lack of cases could be due to the reduced spread of the virus outdoors that also led to fewer-than-expected infections following the riots and protests over the May 25 police killing of George Floyd in Minneapolis. Health officials are worried, though, that rodeo attendees are hesitant to disclose their attendance at an event that defied state COVID-19 safety rules.