New database calculates your risk of being near someone with COVID-19 at various-sized events

Online tool developed by Georgia Tech

COVID-19 test samples.
COVID-19 test samples. (WPLG)

BREVARD COUNTY, Fla. – There is a 26% chance that, if you attend an event in Brevard County with 10 people — say, a dinner party — at least one of the attendees will be infected with the coronavirus, according to a new database developed by Georgia Tech University.

The likelihood jumps to 53% at an event with 25 people, and to 78% at an event with 50 people. And if you go to an event with 100 people — like a wedding reception — there is a 95% chance you’ll be with at least one person with the coronavirus, News 6 partner Florida Today reports.

Georgia Tech assistant professor Clio Andris, who helped develop the database that now tracks every county in the United States, said, before attending gatherings, people should carefully consider the risks. That includes how many people will be at an event, whether the event will be indoors or outdoors, how close contact will be with others, and whether people will be wearing face coverings. Andris is an assistant professor in the School of City and Regional Planning, with a joint appointment in the School of Interactive Computing at Georgia Tech.

Joshua Weitz, a professor in Georgia Tech’s School of Biological Sciences who was the lead researcher on the database, said the issue of understanding risks associated with gatherings is even more relevant now, as many kinds of businesses, as well as sports and universities, are considering how to reopen safely. 

Brevard County Commission Chairman Bryan Lober said the findings contained in the database raise concerns.

"Unnecessarily attending mass events without taking adequate precautions, including social distancing, is akin to playing Russian roulette," Lober said. "If we continue to ignore the infectious-disease physicians and epidemiologists, our numbers will likely continue to worsen."

Lober also was critical of what he perceives as a lack of action by some public officials to institute policies to stop the spread of the coronavirus.

“If you aren’t a physician — or aren’t directly relaying a physician’s advice — stop pretending to be qualified to opine as to the risks we face,” Lober said. “This is a medical issue, not a political one. Current positivity rates illustrate the danger of complacency and a hands-off government afraid to act.”

Lober had pushed for a county policy requiring face coverings when inside local businesses, as a way the help stop the spread of COVID-19, but he could not get the support of the other four commissioners.   

Instead, commissioners voted 4-1 in favor of a non-binding proclamation to "strongly encourage" businesses to post their mask policies at their entrances. There will be no penalty for noncompliance.

Some Space Coast cities have gone further by instituted rules for face coverings.

Georgia Tech researchers say the database (found at https://covid19risk.biosci.gatech.edu/) accounts for widespread gaps in U.S. testing for the coronavirus, which can silently spread through individuals who display mild or no symptoms of illness.

“Precisely because of undertesting and the risk of exposure and infection, these risk calculations provide further support for the ongoing need for social distancing and protective measures,” researchers noted on an interactive dashboard showing their findings. “Such precautions are still needed, even in small events, given the large number of circulating cases.”

Andris said the database assumes that, on average, for every one detected case of COVID-19, there are 10 that are undetected, largely because the person has not been tested.

Andris said other experts have put that figure at anywhere from six undetected cases for every detected case to 24 undetected cases for every detected case.

Andris said, unless someone displays symptoms, in a gathering of a group of people, "you never know who that person is" who has COVID-19.

Weitz said the database takes the number of cases reported in the past 14 days in each county, and multiplies these by an undertesting factor to estimate the number of circulating cases in a particular county.  

Researchers at Georgia Tech recently expanded their database — called the "COVID-19 Event Risk Assessment Planning Tool" — to include county-by-county probabilities for every county in the United States. Previously, the dashboard estimated exposure for different-sized events by state, but not by county. 

The database shows that counties in Florida and other Southern states generally showed higher risks than counties in other parts of the country.

So, for example, in Brevard, there were 3,722 cases of COVID-19 reported as of Wednesday. Using a ratio of 10 undetected cases for every detected case, that would mean there have been 37,220 undetected cases in Brevard County, which has a population estimated by the Census Bureau at 601,942.

To keep up with the latest news on the pandemic, subscribe to News 6′s coronavirus newsletter and go to ClickOrlando.com/coronavirus.