Testing has identified seven new instances of COVID-19 in Minnesota, bringing the state's total to 21 cases of the respiratory illness caused by the new coronavirus.

As the number continued to rise, Gov. Tim Walz announced that he will hold a news conference Sunday morning focused on a statewide schools response. Its details were not disclosed late Saturday.

One of the new COVID-19 cases occurred in south-central Minnesota's Renville County, making it the first in a largely rural county, the state Department of Health said. The state also has its first case affecting a teenager, in Dakota County.

While investigations of each case are ongoing, there is no evidence yet of community transmission of the virus from one person to another within the state, said Kris Ehresmann, infectious disease director for the Health Department. All patients so far appear to have been infected during travel to high-risk areas or by contact with infected travelers, she said.

Twenty of the 21 patients are recovering at home. One remains hospitalized in critical condition.

Ehresmann said the case of the teenager does not involve a student.

Walz and state Education Commissioner Mary Cathryn Ricker will hold a news conference at 10 a.m. Sunday in St. Paul to unveil a plan for schools.

On Friday, state officials said schools would remain open, partly so that health care workers don't have to stay home to provide child care, and partly due to epidemiological evidence that COVID-19 is not spreading rapidly among children and that school closures haven't been effective in this global outbreak. However, school closures could be ordered as the pandemic unfolds, Walz and state Health Commissioner Jan Malcolm said then.

A growing number of states have shut down schools. They include Wisconsin, where Gov. Tony Evers on Friday ordered the closing of all K-12 schools, public and private. The action affects more than 1 million children.

The state's 21 confirmed COVID-19 cases are based on 868 tests, mostly by the state's public health lab, of saliva or nasal samples from people with suspicious symptoms. Ehresmann said the state has limited testing capacity now and has been prioritizing testing of sick patients with relevant travel histories. However, doctors have the discretion to seek tests based on their patients' symptoms and situations, she added.

The state is using some of its testing capacity to search for instances of community transmission. Lab samples sent routinely by surveillance clinics to check for flu and other pathogens are now being checked by the state public health lab for the coronavirus as well.

None of the surveillance tests has found cases of COVID-19, Malcolm said. "It's not widespread," she said. "If it was, we would be seeing it."

Even so, she said it is possible there are community-transmitted cases in Minnesota that haven't been identified through testing. Roughly 80% of infections result in only mild symptoms.

"It would be pretty naive to think it won't be here and probably isn't already here," Malcolm said.

Ehresmann said the additional cases underscore the need for Minnesotans to do what they can to prevent the spread of the virus, including washing hands, and staying home when sick.

Saturday's updates followed a surge of closures, including almost all entertainment and sports venues, as well as a rise in the number of businesses urging employees to work from home. Most restaurants, bars and stores remain open, and many in the Twin Cities were bustling Saturday.

Staff writer Torey Van Oot contributed to this report. Jeremy Olson • 612-673-7744