Health experts: Reopening businesses in Minnesota will spread COVID-19, but how much?

Epidemiologists broadly agree that reopening "nonessential" businesses and public spaces will lead to increased transmission of the virus that causes COVID-19, though the uptick won't be visible immediately.

It's already happening in some states that reopened nonessential businesses, like Alabama, South Dakota and Texas, former Food and Drug Administration Commissioner Dr. Scott Gottlieb has said. Minnesota is gradually allowing nonessential businesses and public spaces to reopen, based on judgments about how well each kind of setting can prevent transmission and monitor for new cases.

But because some increased transmission is inevitable when economies reopen, the big question is whether the increase will be manageable, or if it will lead to soaring rates of new transmissions that trigger a "second wave" and force governments to reimpose mitigation strategies.

Some data experts are using a statistic called the reproduction rate to predict if a spike will occur after reopening, while others in public health say more attention should focus on adequately preparing for a potential surge in cases.

Michael Osterholm, director of the University of Minnesota Center for Infectious Disease Research and Policy, said special attention needs to be paid to the 36% or more of Minnesota's population who are at increased risk for severe or fatal COVID-19 disease because of conditions including advanced age, heart disease, chronic obstructive pulmonary disease, uncontrolled asthma, diabetes, and obesity with a BMI of more than 40.

New York-based data scientist and machine-learning expert Youyang Gu has produced national and state-specific models that show Minnesota's social distancing and mitigation strategies have successfully brought the state's level of transmission just a hair below a self-sustaining outbreak.

The model — one of a dozen tracked by the Centers for Disease Control and Prevention — uses death data to conclude that Minnesota has moved just slightly below 1.0 in a critical threshold that measures how many people a person with the virus is expected to infect, known as the virus' reproductive rate.

Minnesota's SARS-CoV-2 reproduction rate is at .97, according to estimates from the machine-learning model developed by Gu.

Using that reproduction rate, the model predicts daily deaths from COVID-19 in Minnesota will peak at 117 fatalities per day during the last week of June, and then taper to about 60 deaths per day by the first week of August. (No model is perfect, but Gu noted his model came within two days of correctly predicting the date when the U.S. would hit 80,000 deaths, which happened Monday.)

But the Minnesota modeling could change with reopenings. Because reopening a state is likely to increase its COVID-19 R value by as much as 20%, that could bring Minnesota well above 1.0, he said.

"Because of the reopenings that Minnesota is undertaking, there is a likelihood that … the R value will increase above 1. And that will cause a rise in infections and a rise in deaths," Gu said in an interview. "This is not a for-sure thing, but we think it is possible, and perhaps likely."

Minnesota's modelers at the Minnesota Health Department and the University of Minnesota use a higher estimated reproduction rate, saying that one ill person is infecting up to four others on average — underscoring that each model uses a different set of assumptions.

"If you pick an R-naught that you want to use as your target, you run the risk of not being able to achieve that R-naught and basically being left in a position where social distancing is all you have left," said Dr. Amesh Adalja, senior scholar with the Johns Hopkins University Center for Health Security. "I think hospital capacity is really the main driver."

Because reopening more businesses will inevitably cause more transmission, the key is to make sure that the health care providers have capacity in place to handle a surge in cases.

An unexpected spike in cases could put local hospitals into crisis, unless they're prepared with adequate amounts of regular and intensive-care beds, personal protective equipment such as face masks and gowns, and critical care devices like mechanical ventilators, Adalja said.

In Minnesota, hospitals could restart elective surgeries Monday if they've secured enough supplies to care for their scheduled patient load and a number of COVID-19 cases that is predicted to peak this summer.

But businesses aren't being asked to survey their local health care capacity before reopening. Instead, they have to make plans to minimize spread among workers and customers and monitor their workforce to detect and respond to new cases.

As of Tuesday, the state had 280 open ICU beds and the ability to convert another 1,355 beds to intensive care, public data show. The state had 881 unused ventilators, and "vent surge" capacity to add another 1,401. The central state stockpile has an inventory of 5.5 million face masks and 622,000 N95 respirators, but only 39,000 surgical gowns. And the state has just under 40,000 child-care slots for health care workers' children.

Since COVID-19 first developed as a public health threat, epidemiologists have learned more about disease transmission, including the large role of asymptomatic spread.

"It does complicate things," said Ryan Demmer, an epidemiologist at the University of Minnesota School of Public Health. "It really reinforces the importance of social or physical distancing."

State policymakers need to think about long-term consequences before making decisions about lifting restrictions, he said, including options that could protect public health and the economy.