The computer model Tennessee and Shelby County are using to predict and prepare for the surge in COVID-19 cases dramatically changed Monday and for the better.

Predictions on COVID-19 surge differ, but all agree it’s coming

New projections released Monday by the Institute for Health Metrics and Evaluations forecast that the peak in COVID-19 cases and deaths will happen on April 15, four days earlier than projected.

More importantly, the revised forecast suggests that the number of deaths caused by the novel coronavirus will not exceed 600 statewide.

On April 2, the model suggested Tennessee would see more than 3,000 deaths.

The revised forecast also suggests that the number of hospital beds, ICU beds and ventilators needed across the state to handle COVID-19 cases will not exceed the number already in place. Not by a long shot.

On April 2, the model predicted that the number of hospital beds, ICU beds and ventilators needed statewide to treat local COVID-19 patients would exceed the number currently available by this Thursday -- April 9.

But the revised forecast released Monday suggests the state will need 1,232 hospital beds to handle coronovirus cases. The state has 7,812 beds. On April 2, the model was projecting a need for 15,000 beds statewide.

It suggests the state will need 245 ICU beds, and it already has 629. It suggests the state will need 208 ventilators compared to nearly 2,000 on April 2.

Memphis Mayor Jim Strickland said Monday the updated figures are encouraging, and show, in part, that strict social distancing measures here and elsewhere are slowing and reducing the spread of the virus.

Strickland: New COVID optimism based on social distancing

But he cautioned that “models change every day” and that the public should continue to limit social contacts. To emphasize the point, he extended the city’s “Safer at Home” order for two weeks until April 21.

”We can’t let up,” Strickland said. “We certainly hope for the best but we must continue to plan for the worst. ... The virus feeds on social interaction. We need to starve the virus.”

Strickland also said that the revised and rosier forecast will not alter plans by the state or the local task force to add temporary hospital beds, ICU beds and ventilators.

The Army Corps of Engineers will continue its plan to set up a temporary hospital at the Gateway Shopping Center on Jackson Ave., he said. And the state is expected to announce a location for a second temporary hospital in Memphis later today.

The computer model was developed by the University of Washington’s Institute for Health Metrics and Evaluation, or IHME.

It’s the model that prompted Gov. Bill Lee to issue his statewide “stay-at-home” order April 2, and the model he is using to prepare state health care systems for the COVID-19 surge.

It’s one of the models the Memphis and Shelby County COVID-19 Task Force is using to prepare local hospitals for an expected surge in coronavirus cases later this month.

The revised forecasts reflect “a massive infusion of new data,” Dr. Christopher Murray, IHME director at the University of Washington’s School of Medicine, said in a statement that accompanied the updated figures.

“As we obtain more data and more precise data, the forecasts we at IHME created have become more accurate,” Murray said. “And these projections are vital to health planners, policymakers, and anyone else associated with caring for those affected by and infected with the coronavirus.”

The revised forecast includes updated figures from a number of states and international locations where coronavirus cases and deaths are peaking.

It also — for the first time — “assumes full social distancing through May 20, 2020.”

The revised model considers the date on which officials imposed stay-at-home social distancing measures and how much transmission was already underway by that point.

It also considers how strict the measures are. It gives greatest weight to states that have imposed all three of the following:

Closing educational facilities, closing nonessential businesses, and issuing stay-at-home orders.

Tennessee Gov. Bill Lee issued a statewide stay-at-home order April 2. Mississippi Gov. Tate Reeves made the order April 3.

Memphis and Shelby County officials issued “Safer at Home” orders March 24.

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The revised projections clearly show that social distancing policies are working, said Dr. Manoj Jain, an epidemiologist and infectious disease expert hired to advise Memphis on its coronavirus response.

“It shows that we have learned from Italy and New York City and other places where social distancing began too late and the virus overwhelmed the health care systems. We must continue to follow social distancing and other guidelines.”

A team of epidemiologists in Memphis have been using another computer model developed for individual hospitals by the Predictive Healthcare team at the University of Pennsylvania.

It’s called the COVID-19 Hospital Impact Model for Epidemics, or CHIME.

It predicts the surge will crash into Memphis-area hospitals weeks in mid-May or possibly even later in summer, and won’t be nearly as steep or lethal.

The CHIME model also considers the impact of local social distancing measures, and the potential impact of varying degrees of compliance.

For example, it presumes that a community achieving 35 percent compliance will suffer more infections and deaths and sooner than a community achieving 65 percent compliance.

In this ‘maybe’ world, all we can do is prepare and stay home

Local epidemiologists have been working with Vanderbilt University to adjust either or both computer models for Memphis and Shelby County.

For example, they need a model that accounts for the likelihood that Shelby County’s health care system also will be taking care of COVID-19 patients from North Mississippi and East Arkansas.

The IHME model was the same model that prompted President Trump to announce on March 29 that he would extend federal “social distancing” guidelines through April 30.

The updated model still predicts a national “surge” in COVID-19 cases by April 15.

But it also shows a steep decline in the number of projected COVID-19 deaths nationally.

Late last week, the model was suggesting that the nation would suffer up to 170,000 deaths by Aug. 4.

The new updated model suggests that number will be about 80,000.

The updated model also shows a steep decline from 260,000 to 140,000 in the projected peak number of hospital beds needed nationally to care for coronavirus patients.

“Compared with our release on April 2, today’s predictions indicate the same peak date for daily COVID-19 deaths in the US – April 16 – but some states have seen shifts to earlier timing of COVID-19 peak deaths.

“At this peak date, the country’s daily COVID-19 deaths are now estimated to reach 3,130 (estimate range of 1,282 to 7,703) (see below) – again, similar to our last release. Our updated national projections for cumulative COVID-19 deaths through the first wave are lower than our April 2 model, with an estimate of 81,766 total COVID-19 deaths (estimate range 49,431 to 136,401).

“More detailed information in the form of technical appendices will be published online by Tuesday, April 7.”

In recent days, critics have said the IHME computer model has overestimated the COVID-19 crisis.

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The April 2 figures did not factor in the potential impact of Trump’s social distancing guidelines, first unveiled on March 16.

The April 2 model did factor in which measures state officials had imposed, how strict they were, when they began, and how much transmission was already underway by that point, as measured by the number of COVID-19 deaths.

The model gave the most weight to states that had closed schools and nonessential businesses and issued stay-at-home orders.

But both Tennessee and Mississippi issued “stay-at-home” orders after the April 2 numbers were crunched.

Coronavirus Live Blog, April 6: Shelby County deaths now at 17

Some critics say the IHME model has been overestimating the crisis for weeks.

“Whereas the Murray model had predicted more than 100,000 hospitalizations by April 1, the states reported only about 30,000,” the American Spectator reported Monday.

On March 26, the IHME predicted that “41 states will need more ICU beds than they currently have available and that 11 states may need to increase their ICU beds by 50% or more to meet patient needs.”

The April 6 report predicts that only eight states will not have enough beds -- Alaska, Connecticut, Maryland, Massachusetts, Nevada, New Jersey, New York and Rhode Island. And Alaska and Nevada will need only slightly more than they already have.

“If these projections were missing the mark so badly less than a week after they were issued, how could anyone trust IHME model forecasts of what the patient load would be in mid-April or later?” the Spectator asked.

The models creators as well as its critics agree that the revised figures show that social distancing, widespread testing, isolation and quarantining, and other efforts to slow the spread of the virus are working.

“None of this debunking of doomsday forecasts should be interpreted as an argument against ‘social distancing,’” the American Spectator said. “In fact, the effectiveness of these mitigation efforts may explain why the pandemic has failed to become the disaster that the projection models predicted.”

Murray, who developed the IMHE model, also warned the public not to underestimate the value of strict precautions.

“As we noted previously, the trajectory of the pandemic will change – and dramatically for the worse – if people ease up on social distancing or relax with other precautions,” Murray said in his statement.

“Our projections are strengthened by the new downturns in more regions. This is evidence that social distancing is crucial. Our forecasts assume that social distancing remains in place until the end of May.”