MINNEAPOLIS (WCCO) — As cases and testing of COVID-19 across the country rise, positivity rate has become a key metric to determine how quickly the virus is spreading.

So, what exactly does it tell us? Good Question.

The positivity rate — the percentage of positive cases among those who are tested — is one of the main metrics the Minnesota Department of Health uses to determine what should open or be dialed back. MDH also looks at hospitalization rates, ICU usage, new case growth and community spread.

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If the positivity is greater or equal to 15% or has daily increases of 5% over 14 days, then MDH officials would consider dialing back on the COVID restrictions.

Over time, the Minnesota’s positivity rates has changed in Minnesota. In late April, during the shelter-in-place, it peaked at 18%. Back then, Minnesota was testing about 3,000 people per day. Many of those people were sick or high risk.

Now, Minnesota is consistently testing three to four times that. On Monday, the seven-day rolling average was 4.7%. It’s up 7/10 of a percentage point over the past week.

Is a positivity rate of 5% actually good? WCCO asked University of Minnesota infectious disease expert Dr. Michael Osterholm.

“The only thing that’s OK with me is if we had no virus at all that was transmitting. Anytime you have that level of virus, it could increase substantially over the next few weeks,” Osterholm said.

He pointed to the increase in Florida from 5% in mid-June to almost 20% by early July.

According to the Johns Hopkins University School of Medicine, only Arizona (27%), Mississippi (21%) and South Carolina (19%) have higher positivity rates.

MDH Commissioner Jan Malcolm says she believes Minnesota has taken a measured approach to reopenings, but we can’t grow complacent.

“We’re not as wide open as some of the states that are having the more significant outbreaks, but we definitely are mindful of the speed with which those trajectories can change,” Malcolm said.

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Heather Brown

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