How dangerous is it to be in a crowd in NC? Map helps you calculate the risk
A new tool can help determine how risky it is to be in a crowd in North Carolina during the pandemic.
The tool, created by the Georgia Institute of Technology and Applied Bioinformatics Laboratory, shows the chances of being exposed to the coronavirus at a gathering in North Carolina and in each county based on the size of the crowd and other factors.
It allows users to input the number of people in a crowd, or the type of event, and calculates the chances that at least one person there is infected with the virus.
As the size of the crowd goes up, so do chances of exposure.
Statewide, the chances of exposure at a dinner party — which the tool estimates is about 10 people — is 2.1% based on the situation of the pandemic on Monday.
The tool updates daily based on real-time COVID-19 data from the COVID Tracking Project. It also uses population data from the U.S. Census Bureau.
North Carolina reported an additional 1,827 cases of the virus Monday for a total of 87,528 cases since the start of the pandemic. Health officials also presume 55,318 have recovered as of July 6, the most recent estimate.
But officials have long said cases are likely undercounted due to asymptomatic infections that go undetected or a lack of testing.
To account for the “potential for under-testing and reporting,” the tool also analyzes the risk as if the situation were five times and 10 times the “current incidence.”
At five times, the chance of being exposed at a dinner party would be 10.1%. At 10 times, it would be 19.27%.
In a crowd of 100 people — which the tool estimates would be about the size of wedding reception — the chance of one person there being infected is 19.11% based on Monday’s numbers. That goes up to 65.52% at five times the incidence and to 88.25% at 10 times.
At larger gatherings, such as concerts or sporting events, it’s almost guaranteed at least one person there is infected with the virus, the data show.
The tool also breaks down the risk by county.
While most of the state’s 100 counties fall in the range of a 25% to 50% or a 50% to 70% chance of exposure given a 50-person crowd size, 19 have a 75% to 99% chance. The highest chance is in Tyrrell County, at 98%.
Tyrrell, on the coast, is the least-populated county in the state, but on Monday had 128 COVID-19 cases per 10,000 residents, data from the N.C. Department of Health and Human Services show.
If the crowd size were increased to 100, most counties would fall in the 75% to 99% chance of exposure range. Three — Duplin, Tyrrell and Hyde — would reach a 99% chance of exposure.
Duplin County has the highest per capita infection rate in the state, with 284 cases per 10,000 residents and is the state’s biggest hog producer. Meat processing plants have been hit especially hard by coronavirus outbreaks. Hyde County, home to part of North Carolina’s Outer Banks, has 65 cases per 100,000 residents.
But in a crowd of 10 people the risk drops significantly. Most counties fall in the 1% to 25% range.
Health officials have warned against large gatherings during the coronavirus pandemic and have urged residents to practice social distancing and wear masks in public. Gatherings in North Carolina are limited to 10 people indoors and 25 people outdoors under Phase Two of the state’s reopening plan.
This story was originally published July 13, 2020 at 3:00 PM.
