You’ve probably been hearing the term “flatten the curve” a lot these days. It's the idea that society can slow the rate of infection for contagious diseases by taking measures like canceling schools, closing businesses, or sheltering in place. The hope is to reduce the number of patients who need urgent medical care all at once.

The term was actually coined by University of Michigan medical historian Dr. Howard Markel. We talked to him about how he came up with the phrase that’s now being used by people all over the world. Markel said that it all began while conducting research with the CDC regarding flu outbreaks in 2005.

Markel and his cohorts designed a study of the 1918-19 flu pandemic to compare cities that did flatten the curve-taking measures to reduce a spike (or tall curve) in infections and instead stretching them out over a longer (flatter) period of time-with those that didn't.

“And indeed the cities that we studied that did those things did far better than those that did not,” he says.

He says he wasn't suprised when the concept of flattening the curve reemerged during the COVID-19 pandemic because "it’s been a matter of not if there’s a pandemic, but when.”