Why is Minnesota's COVID-19 test positivity rate rising?

Targeted testing may be part of the answer.
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coronavirus, COVID-19 test

Minnesota health officials on Wednesday did their best to explain why a higher percentage of COVID-19 tests in recent days are on the rise. 

For the majority of April and May, Minnesota's test positivity rate reached nearly 15% during the peak of the first burst of the novel coronavirus, but it had been dropping since late May, falling as low as 2.9% in a 14-day period from June 7-20. 

That's a critical component for the economy, as the World Health Organization has advised government leaders that the positive test rate should be at or below 5% for 14 consecutive days in order to safely keep the economy open. 

Thus the reason for concern in Minnesota over the past three days of reporting, as Monday's test positivity rate was 7.6%, followed by 10.2% Tuesday and 5.9% Wednesday. 

The Minnesota Department of Health (MDH) uses a 5-day delay in its test positivity rate reporting to ensure all data is properly captured, but the positive rate over the most recent seven days is 4.4%. That's up from 3.6% the week prior. 

Week-over-week, the past seven days has seen 7.9% more positive tests, according to the MDH. 

Why is the positivity rate is rising?

It's too soon to definitely say, but Kris Ehresmann, director of the Infectious Disease Epidemiology, Prevention, and Control Division at the MDH, hypothesizes that it could be the factor of targeted testing. 

"One thing to consider is that when we see a small increase in our positivity rate, it may be that we are doing a better job of targeting," said Ehresmann.

She used examples of targeted testing events in St. James and Madelia within the past week or so, where the pair of southern Minnesota cities have seen increased levels of COVID-19. Once known to be in a specific location, health officials will target the area for increased testing, which can lead to a slightly higher positivity rate. 

In short, health officials knew where the virus was and were able to test in those locations, making it more likely they'd find it. 

Jan Malcolm, commissioner of the MDH, said the rising rate isn't all that surprising "given what we've seen in other states and given the continued increase in social interactions" since Minnesota's bars, restaurants and gyms reopened June 10. 

Minnesota is one of 23 states currently under the WHO's test positivity rate threshold of 5% over a two-week period, but there are more states – many of them which reopened businesses before Minnesota – that have seen rapidly increasing levels of COVID-19. 

"One thing that we really want to watch is how do these numbers and the age demographics change in the next 2-3 weeks," said Malcolm, who noted that Minnesota is currently experiencing a surge in younger people contract the virus. 

Younger people are less likely to develop severe symptoms, so despite increasing COVID-19 levels in Minnesota, the hospital capacity remains stable for now.  

Daily testing totals were made available for the public's eyes in Minnesota on Saturday, Mar. 28. Below you can see 14-day positivity rates from then through the Fourth of July. 

  • March 29-April 11: 5.4% positive (20,626 tests, 1,119 positive)
  • April 12-25: 14.3% positive (23,413 tests, 3,348 positive)
  • April 26-May 9: 14.3% positive (57,245 tests, 8,213 positive)
  • May 10-23: 9.6% positive (98,303 tests, 9,465 positive)
  • May 24-June 6: 4.9% positive (125,827 tests, 6,157 positive)
  • June 7-20: 2.9% positive (160,623 tests, 4,614 positive)
  • June 21-July 4: 3.3% positive (169,597 tests, 5,664 positive)

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