VDH expert says daily COVID-19 numbers ‘don’t necessarily’ convey anything about the pandemic’s current spread

Coronavirus

VIRGINIA (WAVY) — Every day, 10 On Your Side reports the latest COVID-19 case numbers from the Virginia Department of Health.

The daily rise or fall in the count may cause you to panic or loosen your mask strings. But wait — VDH Respiratory Disease Coordinator Emily Stephens told 10 On Your Side the number of new cases reported daily “doesn’t necessarily convey anything about the pandemic itself.”

“[B]ut we know people have been trying to use those data over time because they are kind of a bellwether or more real-time aspect,” Stephens said.

The daily numbers do not actually tell the story of what’s happening today.

Stephens explained that from the day a person takes a COVID-19 test to the day VDH reports a positive case, the process takes about two weeks because they follow up with everyone in-person. 

“We’ll ask them questions like when they first developed symptoms or when they think they might have been exposed,” she said.

You’re actually better off looking at the numbers that show the date of symptom onset.

“Absolutely. You’re exactly right,” Stephens said. “So onset date is the most scientifically accurate way to look at the spread of the pandemic but because we know people will wait about a week between when their symptoms start to when they got to get tested, and then the test results may take a few days to come back, and then it will take up to a day for the lab to transmit it to VDH. So, there’s about a two-week lag between when symptoms start and when we can publicly report the case.”

That said, 10 On Your Side wanted to know what might have caused the spike in cases being reported now in Hampton Roads.  If most patients showed symptoms two weeks ago and the incubation period is up to two weeks before then, that’s right around the time of the protests against racial injustice.

We asked Chesapeake Health Director Dr. Nancy Welch if that could be contributing to the rise. She told us health officials are not asking patients about protest participation, so they can’t be sure.

When we asked EVMS Infectious Disease Expert Dr. Edward Oldfield, he concluded rallies are likely not the reason for the increase as they were outside and many wore masks.  He said it’s more likely related to phase 2 reopening.

The bottom line, according to Stephens: Don’t hang your hat on the daily numbers, watch the trends instead.  

“Look at it all with a grain of salt so you can say ‘This is what I think the trend is based on these graphs over time, but I’m going to assume its circulating more than it looks like it is,'” Stephens said.


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