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Online Tool Calculates Your Odds of Encountering Someone with COVID-19

An online tool developed at the Georgia Institute of Technology, calculates your odds of encountering someone with COVID-19.

NBC Universal, Inc.

As Americans ponder the perils of traveling and gathering for Thanksgiving amid a worsening pandemic, an online site seeks to quantify the risk.

You input your county and the number of people expected to be at the location where you will be, and the COVID-19 Risk Assessment Tool will calculate the odds at least one person there will be contagious.

The calculation will change as data on COVID spread is updated, but as of Thursday, inputting a Thanksgiving gathering of 10 people in Los Angeles County projected a 12-22% chance one of them has COVID. In Orange County, with lower spread, the likelihood is calculated at 6-12%; in San Bernardino, with a higher rate of spread, 15-29%.

The tool was developed at the Georgia Institute of Technology and went online in June. Since then it has had more than two million visitors, said co-developer Clio Andris, Asst. Professor of City and Regional Planning and Interactive Computing. Approaching Thanksgiving, interest has grown to the point that as many as 20,000 an hour have been going to the site, at times stressing the server and slowing response.

"I think most of the people checking this are being cautious," said Prof. Andris.

The tool does not attempt to calculate your odds of actually contracting COVID, she emphasized, noting that it does not consider the type of event, nor account for whether attendees are wearing face covering, social distancing, and taking the other precautions repeatedly stressed by public health officials.

It seeks only to calculate the odds that someone present is already infected.

Across the nation, public health orders vary. The tool will make a calculation for a gathering of thousands of people, something rarely seen except at some political rallies. At the low end, it will render a calculation for a group of 10 people but no fewer. The risk of COVID transmission at small gatherings was receiving less attention when the tool was launched.

In response to COVID, California has specifically prohibited large gatherings, and discouraged smaller ones. On October 12, Governor Gavin Newsom announced guidelines limiting home gatherings to three household groups, but did not set a ceiling on number of people. On Friday, November 13, Newsom was expected to discuss specifics for Thanksgiving travel and gatherings.

Prof. Andris said she hopes at some point, with an effective vaccine and other developments, demand for the tool will wane. In the meantime, she and Biological Sciences Prof. Joshua Weitz hope to expand its capabilities, and explore the impact of travel.

How Coronavirus Has Grown in Each State — in 1 Chart

This chart shows the cumulative number of cases per state by number of days since the 50th case.

Source: The COVID Tracking Project
Credit: Amy O’Kruk/NBC

"We're starting to examine what that movement is going to be doing to increasing risk in certain places, and decreasing risk in other places, especially for Thanksgiving," Andris said.

In urging Angelenos to avoid Thanksgiving travel and large gatherings, Los Angeles County Public Health Director Barbara Ferrer opened up and revealed she is "sad" she will not be visiting her grandchildren out of state.

"Like all of you, I wish it was different," said Ferrer. "But it's not."

Andris will not be traveling for Thanksgiving, she said, planning instead to stay in Atlanta with her pet bunny and join her family virtually.

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