MINNEAPOLIS (WCCO) — Minnesota health officials reported Thursday 551 new cases of COVID-19 and three more deaths as the Delta variant continues to spread in the state.

The latest update from the Minnesota Department of Health shows that daily new case counts have climbed to levels not seen since mid-May. The rolling seven-day average for new cases is now at 5.5 per 100,000 people, slightly above the figure which health officials consider the threshold for caution.

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In the last 24 hours, nearly 18,000 tests were processed in the state, suggesting a daily positivity rate of slightly above 3%. As of last week, the average positivity rate hit 3%, a figure nearly three times higher than it was at the start of the month.

Health officials attribute the rise in case counts to the highly-contagious Delta variant, which they say is spreading rapidly among unvaccinated people. While people who are fully vaccinated can also get the virus, health officials say that having had the vaccine greatly reduces the chance of getting the pathogen and suffering severe symptoms.

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As case counts have risen, so have hospitalizations. As of Tuesday, 208 people were battling the virus in Minnesota hospitals. Of those patients, 57 were in intensive care beds. In the last two weeks, ICU hospitalizations have nearly tripled.

On Wednesday, Minnesota health and education officials recommended that all students, teachers and staff wear masks when returning to classrooms this fall, regardless of whether or not they are vaccinated. The new mask recommendation came a day after the Centers for Disease Control updated its mask guidelines, suggesting that people (whether vaccinated or not) wear masks indoors in areas where the Delta variant is spreading.

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Since the start of the pandemic last March, a total of 612,001 people in Minnesota have contracted the virus and 7,663 people have died. Currently, 57% of Minnesotans eligible for the vaccine (those 12 and up) have had at least one vaccine shot while 54% are fully inoculated.