Vanderbilt COVID-19 model predicts best scenario of mid-May statewide peak, encouraging Shelby numbers

By , Daily Memphian Updated: April 11, 2020 3:14 PM CT | Published: April 10, 2020 6:15 PM CT
<strong>Registered nurse Shoniece Tate swabs a drive-thru patient during testing on March 21 at a tent behind the Christ Community Health Services clinic. Patients were screened before they could be tested to determine if they had symptoms associated with COVID-19.</strong> (Jim Weber/Daily Memphian)

Registered nurse Shoniece Tate swabs a drive-thru patient during testing on March 21 at a tent behind the Christ Community Health Services clinic. Patients were screened before they could be tested to determine if they had symptoms associated with COVID-19. (Jim Weber/Daily Memphian)

A Vanderbilt University COVID-19 model, which includes some heartening news for Shelby County, projects the disease will peak in Tennessee by mid-June under the state’s status quo but could start winding down by mid-May if the state gets more aggressive with testing and contact tracing.

On the other hand, if Gov. Bill Lee were to lift a “stay at home” order prematurely, allowing Tennesseans to go back to their normal routines, the rate of infections could increase precipitously with no end in sight, the model’s researchers say.


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The governor is using the new Vanderbilt projections to make his decisions, especially with an April 14 deadline looming to extend or lift his executive order keeping Tennesseans at home except for essential trips to work, the grocery store, pharmacies and other places deemed vital. He is expected to make an announcement, likely Monday, before the order expires.

“The epidemic cannot be ordered into submission,” said Melinda Buntin, a researcher working on the Vanderbilt model.

Vanderbilt’s researchers recommend the governor relax his orders only when the rate of infection starts flattening and when speedy, widespread testing is available in conjunction with a robust contact tracing program. The idea is to reach the point where one person carrying the disease is infecting one or fewer people, which means a flattening of the curve.

The model shows the rate of infections in Shelby County could be leveling out already at about 65 to 70 new cases a day. Once the number of new daily cases starts to drop, it would mean Shelby is moving back toward normal, but only if the county’s “stay at home” order and other restrictions remain in place until the disease is under control, researchers said.


Tennessee at 4,862 cases, including 98 deaths


As of Friday, April 10, Shelby County has 1,085 cases out of 4,862 cases statewide. Across Tennessee, 98 people have died from the disease, according to the Tennessee Department of Health.

<strong>Gov. Bill Lee</strong>

Gov. Bill Lee

Researchers pointed out Tennessee’s epidemic could have been sparked by as few as 10 people.

John Graves, who is heading up Vanderbilt’s projection, pointed out the Memphis area has made drastic improvements already by reducing its transmission rate from five people to 1.5 people, meaning one person with the disease is now infecting only 1.5 other people, instead of five others.

“The turnaround of testing in the Memphis area has been very consistently among the best in the state to date,” Graves said.

That enables officials to get a better handle on who is infected so they can be treated and quarantined before spreading the disease.

Graves noted the Mid-South started off with a high transmission rate, likely reflective of its urban nature, and then dipped “very fast,” likely because of social distancing.

“It seems that people complied and that transmission rate dipped from around five to the where the rest of the state is, around 1.5 or below, very quickly,” Graves said.

Researchers could not determine the potential impact of Arkansas and Mississippi residents on transmitting the disease into Memphis and Shelby and their impact on hospitals.

Davidson/Williamson combined rates have started to dip from a high of about 80 cases a day to about 50 cases daily, and the rest of the state is starting to level out at just over 100 cases each day.

To reach toward a point of normalcy, the state would need to see a sustained decline of cases for 14 days, hospital capacity for all patients, which is now available, and a system to test all residents for the virus.

According to Lee, no person seeking a test is being turned down in the state. Tests with a five-minute turnaround are being offered in some locations, too, but so far, the state hasn’t started offering testing to every resident to ensure no one is spreading the disease unsuspectingly.

The Vanderbilt model differs from an Institute of Health Metrics at the University of Washington model primarily by using Tennessee statistics. The model the nation and state have been depending on is based largely on information from Wuhan in China, Italy and Spain, where the disease started and spread rapidly.

That model, which was changed dramatically this week, showed a mid-April peak in Tennessee and mid-May flattening. The Vanderbilt study, in contrast, shows a late June flattening if aggressive testing and contact tracing are done and an August or later flattening under the status quo.

Topics

John Graves Melissa Buntin Vanderbilt University
Sam Stockard

Sam Stockard

Sam Stockard is a Nashville-based reporter with more than 30 years of journalism experience as a writer, editor and columnist covering the state Legislature and Tennessee politics for The Daily Memphian.


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