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Mecklenburg Won't Release COVID Projections After Use Of Model Questioned

Mecklenburg County
Mecklenburg County will no longer release projections about the spread of COVID-19. A data scientist at the University of Pennsylvania said the county was using his model incorectly.

Mecklenburg County's health department said it will stop releasing projections about the spread of the coronavirus after a data scientist from the University of Pennsylvania said the county wasn't using his model correctly.

The county has been using a model from Penn Medicine known as CHIME. That model repeatedly projected the county would see an explosion of new cases, with hospitals being overwhelmed. 

The first CHIME projection from April showed county hospitals would be overwhelmed in mid-May. Mecklenburg then later released models that showed a peak of cases in June. The most recent county model showed a peak in mid-July, with hospitals not having enough ICU beds and ventilators.

But, for now, the number of COVID-19 patients in county hospitals has been declining, from a high of 111 on April 9 to 48 on Sunday.

Michael Draugelis, chief data scientist at Penn Medicine, said CHIME should only be used in the early stages of an outbreak. He said the model wasn't designed to work when cases begin to plateau, which is where Mecklenburg has been for roughly a month.

“We made a decision to fit (our model) on the front side of the curve,” Draugelis said. “We will assume that people are using this as they are ramping up into the epidemic and toward the peak, so it’s never going to fit you on the other side of the curve.”

Since the CHIME model is designed to simulate the start of an outbreak, it will show an explosion of cases, whether it's run on March 15 or May 15. 

CHIME comes with a notice on the website: The model is “limited to short term forecasting. It is only applicable during the period prior to a region’s peak infections, and it accounts only for a single significant social distancing policy.” 

Mecklenburg deputy health director Raynard Washington said last week it was OK to use CHIME after cases began to level.

But on Tuesday he said the county was changing course. He said the county will still monitor data and forecasts, but "we are not planning to release additional projections beyond the start of Phase 1 of the reopening plan."

He said the county is encouraging people to "monitor our state and local trends showing us how things are changing in real-time as we relax the stay-at-home order."  

"We’re not in the clear," he said. "The virus is still with us, and with increased social interactions/activity, spread can accelerate quickly."

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