COVID-19 case levels worsened in multiple counties across Minnesota, according to data released Thursday, with six mostly rural or outstate counties reaching levels at which the state recommends all online K-12 classes.

Other counties including Hennepin and Ramsey showed declines in their rates of new cases, though, amid some optimistic signs of an easing in the pandemic that has now caused 1,942 deaths and 86,722 infections with the coronavirus that causes COVID-19.

Health officials urged individuals in these counties not to become complacent and local school officials not to overreact. The state reported relatively high daily tallies on Thursday of nine deaths and 931 lab-confirmed infections.

“We’re advising school policymakers to continue to be cautious in their decisionmaking,” said Kris Ehresmann, state infectious disease director.

The positivity rate of diagnostic tests in Minnesota dropped from 6% in late August to 4.8%. That is below the state goal of 15%, and the 5% threshold that health officials said reflects a concerning level of viral spread.

COVID-19 hospitalization numbers remained near two-month lows on Thursday — with 242 cases in hospitals and 132 of those patients requiring intensive care.

The state has surpassed 7,000 hospitalizations for COVID-19 since its first cases emerged in March. Among all known infections, 79,878 people have recovered to the point they are no longer considered infectious.

Current COVID-19 case data do not reflect all viral transmission that occurred over the Labor Day weekend, or with the resumption of K-12 and college classes, because it can take 14 days after infection for symptoms to emerge. Then it can take another two weeks for secondary infections, which can lead to exponential growth in COVID-19 illnesses.

Minnesota saw its rate of new cases per week per 100,000 people jump from 8 on July 4 to 13 on July 29, according to the state’s COVID-19 response dashboard.

“If we see some of the same impacts after Labor Day that we did from July 4, we may be anticipating seeing some increased case numbers in the future,” said Jan Malcolm, state health commissioner.

State surveyors have started going door to door in 180 neighborhoods across Minnesota this month to offer free diagnostic testing to find out if people have infections, and antibody testing to find out if they have recovered from prior infections.

Results of this surveillance testing will inform health officials about how widely the virus has actually spread, given that confirmed cases don’t include mild or asymptomatic infections that were never tested or diagnosed.

“Research like this gives us another window into how COVID-19 is spread in our state and the actions we can take to slow the spread,” said Dr. Ruth Lynfield, state epidemiologist, urging people to agree to testing if surveyors come to their doors.

A high rate of infections would suggest that Minnesota is getting closer to a level of “herd immunity” that makes it harder for the virus to spread.

State health officials also are planning for distribution if any experimental vaccines in clinical trials gain approval from the U.S. Food and Drug Administration.

The state received distribution guidance from the federal government on Wednesday and has until Oct. 16 to respond with its plan, Ehresmann said.

The basic plan will be to prioritize limited initial doses for health care workers and people at greatest risk of severe COVID-19 illness. High-risk groups include people with chronic disease or who are 70 or older. People in that older age range make up 80% of the COVID-19 deaths in Minnesota, including seven of the nine deaths reported Thursday. One involved an individual in the 40 to 44 age range.

Ehresmann said distribution will be complicated in practice because there could be multiple vaccines approved that are stored and handled in different ways, and administered at different time increments. Some vaccines could end up working better in certain demographic populations than others.

“This process will be infinitely more complex than any of the mass vaccinations we have done in the past,” she said, “even H1N1.”

The county-level data released Thursday is based on new cases in the two-week period through Sept. 5. The number of counties with low enough rates to recommend all K-12 in-person classes dropped from 35 in the prior period to 24 now.

The number of counties with cases high enough to now recommend all online classes increased from one to six — though case rates for the mostly smaller counties in this range tend to be volatile from week to week. Counties with new case levels in this high range include Waseca and Winona — the latter of which is being affected by a COVID-19 outbreak at Winona State University that includes more than 100 active infections among staff and students.