Academics Calculate the Risk of Running Into Someone With COVID-19 in a Portland Crowd

It's a coin flip.

Powell’s and other retailers have limited their capacity during the pandemic. (Wesley Lapointe)
By Rachel Monahan

As case counts continue to climb, Portlanders face a significant risk of running into someone with COVID-19.

Professors at the Georgia Institute of Technology, along with researchers at the Applied Bioinformatics Laboratory and Stanford University, have put an exact number on it—to help individuals and policymakers assess risk. The academics developed a tool that indicates how likely it is to run into a person with COVID-19 at a gathering, depending on crowd size. (An article documenting the analysis and the assumptions appeared earlier this month in the science journal Nature.)

The model assumes that for every official case of COVID-19, 10 more go undiagnosed.

Right now in Multnomah County, Gov. Kate Brown has capped the number of people who can gather for an indoor church service at 25. What's the risk of running into an infected person among such a flock?

It's not good—and the odds are getting worse. Using the model, we compared the risk of encountering a COVID-carrying person in a Portland crowd of 25 with that in 10 other similarly sized cities.

What are the chances that someone in a crowd of 25 people has COVID-19?

91% in Salt Lake City

87% in Denver

86% in Minneapolis

66% in Miami

49% in Portland

41% in Seattle

39% in Atlanta

30% in Portland, Maine

29% in Austin

22% in San Francisco

18% in Burlington, Vt.

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