Stopping a Second Wave: How health experts use models to help guide preventative measures

“It’s reasonable to assume today’s news will not be the last positive case we hear about in our region,” said Joe Parisi, executive for Dane County.

Since then, experts have been trying to understand how far the spread could go. The first public model from the Wisconsin Department of Health Services in late March estimated, without action, the state could have 22,000 cases and between 440 to 1,500 deaths by April 8th. Other projections, based on how the virus was spreading elsewhere, were far worse.

But additional models would help experts understand what could happen if they took action, such as requiring people to stay home as much as possible.

“It gives us a lot more evidence than just making guesses,” said Shaun Truelove, an assistant scientist with the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health

Truelove used a series of models to better understand how the pandemic could play out in the state. The scenarios that were created for the state are based on a methodology developed by the JHU Infectious Disease Dynamics group. For instance, it takes into account predictions on initial infections through travel, data on how people interact with each other, the infection rate, and the probability that a case will become severe, among other issues.

“We don’t just want to know how many people are hospitalized overall, but we actually care about how many are overlapping,” Truelove said.

He created the latest model released by the Wisconsin Department of Health Services. It shows how prolonging the Safer at Home Order could impact the peak in cases.

“This gives us a really good sense of how we might need to respond or how we can respond,” Truelove said.

So far, the scenarios show a peak in hospitalizations has been nearly cut in half compared to no action. This is true for both acute and peak calculations after lifting the stay at home order after at least a month.

“The JHU-IDD scenarios suggest that, without interventions, Wisconsin would experience at least threefold excess deaths and a sixfold higher number of patients needing beds than

Wisconsin hospitals can provide,” the state report said.

“What happened was the community responded exactly as they need to from a hospital standpoint. And that is, the community stayed at home, they washed their hands, they exercised social distancing,” said Dr. Marilu Bintz, Chief Population Health Officer for Gundersen Health System.

The curve is flattening.

“We’re in a much better position from a hospital capacity standpoint to handle what we think will be waves of coronavirus probably for the next 12 to 18 months,” Bintz said.

But, the model shows that when the Safer At Home order is simply lifted after one month, two months or three months, there’s little difference in hospital occupancy, ICU capacity or ventilators needed. This is true for both acute and peak scenarios were testing and isolation is not included.

Table 3. Projected counts of hospital occupancy and ICU capacity at peak, as well as cumulative deaths and infections.

We provide counts for two periods: Plan 1 = Acute, through May 1 and Plan 2= Peak, which varies by scenario.

Scenarios are 1) Uncontrolled, 2) Safer-At-Home, 1 month, 3) Safer-At-Home, 2 months, 4) Safer-At-Home, 2months + Test/isolate, 5) SaferAt-Home 3, months, and 6) Safer-At-Home, 3months + Test/isolate

1 From JHU-IDD report Table 1, which provides total number of cases within the specified time interval, but does not include ICU or

Ventilators.

2 From JHU-IDD report Tables 2-7, which provide ICU “daily peak capacity” through the end of the specified period up to Oct 1.

3 Ventilator estimates are estimated based on the percent of ICU cases that were under ventilations in the US (Seattle 70%)

“The JHU-IDD presents scenarios during which the Safer-At-Home order persists for one, two, and three months, but no follow-up testing and isolation. Each of these scenarios exhibits a similarly shaped and substantial peak that would dramatically overflow hospital resources,” the state report noted.

However, the delay in peak under these scenarios, just lifting the order, gives medical experts time to find better pharmaceuticals, ramp up testing and expand isolation capacity.

“So all of this is trying to slow things down, give us more time to respond and not overwhelm current capacities,” Bintz said.

While these are just scenarios and should not be considered as definitive forecasts, Dr. Marilu Bintz said Gundersen Health System is anticipating additional waves.

“Everything the community has done to flatten that curve will avoid that big peak,” Bintz said.

They are confident in their PPE supplies and supply chain, but they will keep limiting visitors, will consider reopening services slowly, and keep protecting patients through separation.

“We’re in a good place in terms of our supplies to protect our staff and patients but also care for our patients. We would not even consider reopening any services at all if we felt that we were in a position where our hospital capacity to care for patients would be overwhelmed,” Bintz said.

There is one way these scenarios could vastly change without a vaccine or cure–widespread testing and isolation.

“With comprehensive testing and isolation, the magnitude of the number of cases in Wisconsin will be below the threshold of hospital capacity,” the state report said.

“We’ve surpassed a million Americans who have been diagnosed with COVID. It may be five or 10 times that,” said Dr. Sean Dowdy, chair for the division of Gynecologic Oncology at Mayo Clinic.

Dowdy said part of the problem is there no national testing plan. There are issues with coordination, organization and strategy.

Some parts of the country are without supplies to conduct a test. Others might not have enough staff to process the tests.

“We have a testing plan for patients at Mayo Clinic. We don’t yet have a strategy for the state of Minnesota or Wisconsin,” Dowdy said.

He said Mayo Clinic proposed a strategy to state health officials to run 40,000 blood tests and 12,000 PCR tests a day. The plasma tests to show if someone has been exposed or recovered from COVID-19, while the nasal swab could tell if someone is currently sick.

“That’s a totally different strategy in testing the wider population instead of just patients who are presenting to Mayo Clinic for care,” Dowdy said.

This is, in part, why questions of when to stop social distancing and reopen businesses is a tough one.

“It’s very difficult to answer those questions if we don’t understand what the current disease status is and we’re only going to accomplish that through additional testing and a coordinated effort to do that,” Dowdy said.

According to DHS, based on the model, if we can catch people early, we may suppress or delay a substantial second wave, well below the threshold of hospital capacity.

“Under testing and isolation, all symptomatic cases are tested and all cases testing positive are isolated. Contact tracing is also implemented, and the close contacts of all individuals testing positive are also tested and isolated if testing positive,” the report said.

“We can presumably limit the infections quite a bit until we do have something like a vaccine,” Truelove said.

Doing so may very well help us return to normal life faster while saving lives.

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