Minnesota will update its COVID-19 modeling to forecast possible second wave

Predictive modeling that guided Minnesota's initial response to COVID-19 is being "recalibrated" with the latest pandemic data and will offer new forecasts about the spread of the infectious disease.

While growth in COVID-19 cases, hospitalizations and deaths has eased in Minnesota, state health economist Stefan Gildemeister said Tuesday that modeling on the downside of the initial pandemic wave can help prepare the state long-term. Updated COVID-19 forecasts by researchers at the University of Minnesota and Minnesota Department of Health should be released by mid-July.

"There is a need for modeling and we will continue to carry it forward," Gildemeister said. "This epidemic will last until the virus has traveled through enough of the population (that we develop) natural immunity, or we gain immunity through a vaccine."

The pandemic has caused 33,469 lab-confirmed cases of COVID-19 and 1,393 deaths in the state, but case growth has leveled off — with the health department reporting 245 cases and nine deaths on Tuesday. Hospitalizations have increased since Sunday — with 339 patients being hospitalized for COVID-19 on Tuesday, and 158 needing intensive care — but that is below the peak of 606 hospitalizations on May 28.

Updated modeling will try to assess the timing of any second wave of COVID-19 cases as state restrictions ease and social distancing compliance diminishes, and whether it will exhaust the state's hospital resources, Gildemeister said. A delayed second peak in the winter could be problematic as it coincides with the start of the influenza season.

"As more people mix, the more the virus will be passed on to other individuals," Gildemeister said. "Some people will get very sick. Some people will die. The question is, when shall we expect that?"

Minnesotans are moving about more as Gov. Tim Walz has gradually repealed restrictions designed to reduce the spread of the virus.

A statewide stay-at-home order ended on May 18; retail shopping, church services and outdoor dining resumed on June 1; and indoor restaurants, fitness clubs and entertainment venues reopened at limited capacities on June 10.

Highway traffic volumes that were 70% below normal in mid-April in the Twin Cities were just 25% below normal on June 16. And June 6 was the first day in months when there was more "unpredictable travel" in the Twin Cities — meaning more people were taking short trips and running multiple errands.

Other models have already predicted more cases due to the relaxation of restrictions. The Institute for Health Metrics and Evaluation in Washington state predicts 3,191 COVID-19 deaths in Minnesota by Oct. 1.

Minnesota is one of 23 states currently rated by the COVID Exit Strategy website as "making progress" or "trending better" due to slower growth in COVID-19 cases.

State health officials have reported progress in reducing outbreaks among the most vulnerable populations in long-term care facilities and assisted living facilities — where increased diagnostic testing has sought to identify infections before they spread.

The majority of COVID-19 deaths in Minnesota — 1,101 — still involve residents of these facilities, though. Risks of severe COVID-19 appear highest among the elderly and people with underlying health conditions such as diabetes, asthma and diseases of the lungs, kidneys and heart.

A recent uptick in cases in younger people is raising concerns, especially as people return to restaurants and public gatherings, said state infectious disease director Kris Ehresmann. "With reports from our own staff of crowded venues with lots of people not wearing masks, we will likely see more cases," she said.

Some of that increase is due to workplace outbreaks, including at food-processing plants in Mower County that have contributed to 813 lab-confirmed COVID-19 cases and two deaths there.

Younger people also were involved in protests following the May 25 police killing of George Floyd, and health officials worried that the mass gatherings would spread the virus as well.

However, less than 2% of tests of people involved in the demonstrations have turned up positive for the virus, which Ehresmann said is "very encouraging."

Gildemeister said the updated modeling will benefit from the latest information about the outbreak in Minnesota. Earlier versions were more reliant on the origins of the pandemic in China and its spread to Europe.

Modeling in Minnesota has been politically controversial, with Republicans questioning the high death counts of initial models and questioning whether they pushed Walz to prolong an economically crippling stay-at-home order. Nearly 800,000 unemployment insurance claims have been filed since the start of the pandemic.

The latest state models predicted that Minnesota would see 1,441 deaths from COVID-19 by the end of May and a peak of cases on June 29, under a scenario by which its stay-at-home order ended on May 18. The actual death count at the end of the month was 1,050.

Gildemeister said the latest data on the pandemic in Minnesota will increase the precision of modeling, though he stressed that it was designed to assess how social policies would reduce deaths and cases — not to predict precise COVID-19 counts.