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Are we ready to ease coronavirus shutdown? How predictive modeling will help answer that question

Dr. Roger Lewis and his team are studying how reopening businesses and schools would result in possible increased coronavirus exposure and hospitals’ ability to handle surges

Projecting the impact of reopening businesses and schools vs. the possible increased coronavirus exposure and hospitals’ ability to handle surges will be a vital process as public health officials inch closer to easing stay-at-home orders in effect until May 15, a vital exercise will be.

RELATED: LA County creates team to plot easing of Safer at Home orders

Dr. Roger Lewis leads the team using statistical tracking to create models that show what Los Angeles County should expect to see in the weeks and months ahead, based on the approach to lifting such orders.

If the county fully relaxed its stay-at-home orders — and turned it off like a light switch — hospitals could expect to see the same type of catastrophic surge that was predicted earlier this month, he said during a recent interview.  It’s disheartening news for those struggling financially through the shutdown, but it doesn’t mean that things can’t start to reopen, Lewis said, applying a thoughtful, measured process.

“I think we need to think of the physical distancing as just one way to prevent spread but not the only way,” said Lewis, who chairs the emergency department at Harbor-UCLA Medical Center.

With increased testing capability and teams of investigators to trace the contacts made with infected people, Lewis said the virus could still be effectively contained — even without the most harsh stay-at-home demands.

“If we are better at isolating and treating people who are sick, then perhaps we can be less stringent on everybody restricting their movements,” Lewis said.

New modeling data presented by Lewis and his team showed that if social distancing measures continued the number of patients admitted to hospitals should remain relatively flat at about 1,600 patients on average at any one time, slightly lower than current levels and well within hospital surge capacity for COVID-19 patients of about 3,750 beds.

About 30% of those hospitalized will need intensive care units and roughly 20% will require ventilators. Both projections are within what hospitals think they can handle, according to the models.

How do officials come up with these models? The most common methodology in epidemiology — and the one used by Lewis and his team — is called a compartment model.

Populations are divided into compartments, such as:

  • Susceptible
  • Infectious
  • And recovered

Formulas using varied differential equations and dynamics are used to predict what will happen.

generic coronavirus
Staff at the Orange County Health Care Agency’s Public Health Laboratory conduct tests for the new coronavirus, also known as COVID-19. (Courtesy of Edward Mertz, Orange County Health Care Agency)

There are dozens of other models out there — the most prominent alternative being from the Institute for Health Metrics and Evaluation at the University of Washington. One way that Lewis said to verify a model is to look at what was predicted last week compared to the real world experience this week. By this account, Lewis said he’s confident the models LA County is using now are correct.

The models presented this week, showed that if physical distancing was eased off now, up to about 96% of LA County residents could become infected by August 1, according to an estimate presented by Lewis’ team this week.

There is some uncertainty, of course. If social distancing and closures continued until the summer, roughly 11% of residents will become infected.

But almost every public health official understands the public cannot keep up these closures that long. And most agencies are starting to plot out timetables for at least partial reopenings, with limitations.

“The current strategy, which is largely physical distancing, is effective and has helped us from having a really painful public health emergency,” Lewis said. “But we need to figure out what we are going to replace that strategy with and I believe public health is working really hard at figuring that out.”

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