‘The virus doesn’t know what the borders of counties are’: A closer look at the CDC’s new color-coded map


RALEIGH, N.C. (WNCN) — Every county in North Carolina is bordered by another that is either colored orange or red on the Centers for Disease Control and Prevention’s latest alert map, signifying a recommendation for residents to wear masks indoors to fight the fast-spreading COVID-19 delta variant.

“The virus doesn’t know what the borders of counties are,” Dr. Rachel Graham, an epidemiologist with the University of North Carolina’s Gillings School of Global Public Health, said.

The CDC’s updated guidance recommends people living in counties considered substantial (orange) or high (red) transmission areas wear masks indoors, even if they are already vaccinated.

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That goes for 79 of North Carolina’s 100 counties — including Wake County and almost every county south of it.

But a CBS17.com analysis of the data that goes into the map shows even those counties colored yellow (moderate) or blue (low) are at risk because the speed at which the more infectious variant can spread renders county lines essentially meaningless.

Source: Centers for Disease Control and Prevention.

“We don’t all just stay in our county every day,” Paul Delamater, a UNC professor and an expert in health geography, whose website nc-covid.org tracks pandemic trends, said.

He continued, “When I leave home, I cross county lines to go to work every day. It is important to look at your county. I think that gives you a general idea of how many infected people are in and around your daily lives. But I do think people need to think about that you may be going into a county that has significant transmission right now.”

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The CDC map released earlier this week is driven by two key metrics — how many new cases per capita a county had during the last week and the percentage of tests found to be positive.

Counties shaded orange had between 50 and 99 new cases for every 100,000 people from July 19-25, and a percent positive of 8-percent or higher up to 10-percent.

Red counties had 100 or more new cases and a percent positive of at least 10-percent.

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Additionally, most of the 41 red counties in North Carolina are located in the southern half of the state near the border with South Carolina. 

In 23 of those both the case count and percent positive exceed the thresholds for the red zone. That total includes five in the CBS 17 viewing area: Cumberland, Hoke, Harnett, Lee and Moore.

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“I’ve been looking at the state and monitoring how things are changing, and it’s changing fast,” Delamater said.

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So fast that the county alert map the state Department of Health and Human Services released last week — with only one red county, meaning COVID-19 is having a critical impact there — is already out of date.

Source: NCDHHS.

“People should keep in mind that the state maps, especially, are a little bit behind,” Graham said. “We’re talking about the coronavirus, infection and transmission, a week is a very, very long time. So go with the most up to date information you can and right now, that’s the CDC maps.”

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