Why do coronavirus predictions vary so widely?

Apr 24, 2020, 5:25 AM

Provo mask mandate KSL Newsradio Coronavirus questions...

FILE -- A sign outside the University of Utah Hospital. (Meghan Thackrey | KSLTV

SALT LAKE COUNTY – The questions about the spread of COVID-19 still persist.  When will the peak number of cases hit Utah?  Will we have enough beds and respirators?  The answers to these questions can vary wildly, depending on who you ask.  So, why is it so hard for researchers to agree on what the right answers for coronavirus predictions are?

Many health boards across the country rely on the Institute for Health Metrics and Evaluation model.  That projection shows the number of daily coronavirus deaths would hit a plateau in Utah around this weekend, although deaths and overall confirmed cases of the virus would start going down around May 6th.  However, if you ask the University of Utah, that plateau would last quite a bit longer.

Why, oh why, can’t these models agree?

Utah Department of Health Environmental Epidemiology Program Manager Sam LeFevre says, “All models are right and all models are wrong.”

Wait… what?

“It depends on what the model is designed to answer,” he clarifies.

When researchers create models to predict how quickly a virus will spread or how many patients are expected to become sick, they have to put certain parameters into their systems.  Some of these parameters may include how long it takes before someone shows symptoms, how long the illness lasts and how many people one person can infect.

If viruses have been around for a long time, researchers have a clear understanding of what kind of parameters they should be looking for.  However, COVID-19 is brand new, and LeFevre says some researchers are guessing.

“Over time, the models get better because we get a better understanding of what those parameters are and where they fit,” he says.

In his case, LeFevre is looking at it from a perspective of what if the state did absolutely nothing to slow the virus down.

He says, “The model that I’m running is designed to answer [what is] the worst-case scenario.”

However, he acknowledges models being used by the University of Utah may be more accurate, at times.  He says those allows researchers to look at things as they change.  Although are a few drawbacks with that type of system.  One, they much longer to formulate their predictions since thousands of data points have to be calculated.  Plus, every single change in the data has a huge ripple effect.

University of Utah Research Assistant Professor Lindsay Keegan says, “Sometimes, it feels like when you get a handle on one thing, another fire pops up.  There’s something new that might impact the modeling.”

Keegan’s model has a much wider range of parameters.  For instance, if restaurants allow customers to enter to pick up their orders, that changes the parameters.  If it allows in-house dining, that changes them even more.  She says every new policy that state or local governments make adds a new wrinkle to the modeling, for good or for bad.

When the state allows businesses to have a “soft” reopening next week, projections are going to change, again.

“As we life those measures, the number of [COVID-19] cases will start to go up, hopefully not by too much, and the peak will come sooner and sooner,” Keegan says.  “If we lift things too quickly, we might see a massive peak which might lead people to do another lockdown.”

Earlier this week, officials in China put the city of Harbin on lockdown, again, after a spike in COVID-19 cases.

How To Prevent the Spread of COVID-19Coronavirus

COVID-19 coronaviruses transmitted from person to person. It is a virus that is similar to the common cold and the flu. So, to prevent it from spreading:

  • Wash hands frequently and thoroughly, with soap and water, for at least 20 seconds.
  • Don’t touch your face.
  • Keep children and those with compromised immune systems away from someone who is coughing or sneezing (in this instance, at least six feet)
  • If there is an outbreak near you, practice social distancing (stay at home, instead of going to the movies, sports events, or other activities.)
  • Get a flu shot.

Local resources

KSL Coronavirus Q&A

Utah’s Coronavirus Information

UtahState Board of Education

Utah Hospital Association

The Church of Jesus Christ of Latter-day Saints

Utah Coronavirus Information Line – 1-800-456-7707

National Resources

Centers for Disease Control and Prevention

Commonly asked questions, World Health Organization

Cases in the United States


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Why do coronavirus predictions vary so widely?