You’re standing in line at the grocery store in Woodbury. You count about two dozen people and workers at the registers. How likely is it that one of them has the coronavirus?
Between 74 percent and 94 percent.
That’s the sobering — albeit roughly imperfect — result of a COVID-19 risk calculator created by Georgia Tech University to help people get a real sense of how widespread the virus is. And clearly it’s widespread right now in the Upper Midwest.
The tool can be found at covid19risk.biosci.gatech.edu.
Another example: The risk of at least one person having the coronavirus at a gathering of 10 in Hudson, Wis.: between 42 percent and 67 percent.
That same group in:
- Ramsey County: 36 percent to 60 percent.
- Otter Tail County: 56 percent to 82 percent.
- Foster County in central North Dakota: 89 percent to 99+ percent.
- New York City: 10 percent to 19 percent.
The online tool uses daily case information data from numerous sources and, using statistical probability, creates an interactive map that generates a percentage for each county, according to Clio Andris, an assistant professor at the School of Interactive Computing at Georgia Tech and part of the team that created the tool.
The percentages might seem precise, but the intention behind creating the mapping software was to give people around the nation and world a plain-language sense of how risky exposure would be if they were to travel.
There are obvious weaknesses.
The data is based on active COVID-19 cases. It does not account for the fact that some percentage of those cases will be hospitalized or at least isolated, and therefore out of circulation in the general population. On the flip side, large percentages of those infected and contagious are believed to exhibit no symptoms, at least early on, so there are invariably healthy spreaders who have no idea they’re infected — or have even been exposed — and thus would have no reason to believe they need to isolate.
And the tool doesn’t attempt to tell you the odds of catching the virus in any given setting. No one knows that, although it’s widely accepted that the riskiest situations are indoors, close together and unmasked, with the risk increasing the longer one is in that setting. Because people in grocery stores are universally masked, generally spaced apart and not in proximity for much time, grocery stores are not seen to be particularly high-risk.
The range of percentages in the tool is the result of two options users can enter: Whether each lab-confirmed case represents 10 actual cases, or whether it represents five. Minnesota officials last week said they believe the state is likely between those two options.