By Chelsea Grinstead | With so many people using home tests to check whether they have Covid-19, you may wonder how accurate state-reported data are in framing the prevalence of the disease.
Short answer: State data are kind of like the fishwrap that newspapers become. The numbers indicate increases in Covid-19 cases within a population, but little more.
Weekly Covid-19 case numbers have been underreported to federal institutions throughout 2022 due to the wide availability of self-administered testing, according to a Charleston public health expert. But, those numbers still alert the public to spikes in Covid-19 transmission.
“When those numbers go up for the reported cases, it’s telling you that there really is an increase happening out in the community,” said Dr. Michael Sweat, director of the Medical University of South Carolina (MUSC) Center for Global Health. “They are real data — there’s weaknesses to them, but they’re better than nothing.”
Meanwhile, experts say wastewater testing is a more accurate way to measure the number of Covid cases.
“We know that [cases are] underreported — and so wastewater would be a more reliable indicator,” said Dr. Brannon Traxler, director of public health for the state Department of Health and Environmental Control (DHEC). “We have 15 sites in South Carolina and they are fairly well spread out … [but] there are a lot of places in the state [from which] we are not getting specimens.”
And Charleston County is one of them. Its wastewater treatment facilities were contributing data to the Centers for Disease Control and Prevention (CDC) and DHEC’s wastewater surveillance dashboard in 2021 and part of 2022. But, Sweat said the last data reported for Charleston County was in August 2022.
What experts say about weekly Covid numbers
The weekly Covid case numbers reported by the CDC and DHEC are best interpreted as a baseline for the actual transmission rates, Sweat said.
“The Wall Street Journal worked with several academic epidemiologists and came up with an analysis in May 2022. They very carefully looked at this issue and estimated based on the data that was analyzed that [the real number of cases is] about six to 10 times the number that we see [reported]. So right now [if] it’s like 22 cases per 100,000 — it’s probably more like 220 per 100,000.”
Biases have always existed in Covid case reporting, Sweat said, because since the beginning of the pandemic people who were infected with Covid-19 didn’t undergo reportable testing.
“I just think you have got to be careful that perfection doesn’t become the enemy of the good.”
Sweat described Covid weekly case counts as a canary in a coal mine. “The numbers give you a warning,” he said.
How severity relates to case quantity
Three years into the pandemic, the CDC and DHEC now urge people who want to better understand the virus to look at its community levels map to see the severity of cases instead of looking at the number of cases.
Community levels, which take into account transmission and hospitalization rates, became a metric about a year ago to indicate whether hospital systems are inundated with serious Covid-19 cases.
“The argument is: ‘We now have therapeutics and vaccination and immunity and what really matters is the impact on the hospital system, because we can’t really allow the hospital system to get overrun,’” Sweat said. “In essence, the CDC is saying, ‘We’re going to de-emphasize high transmission and focus on transmission coupled with impacts on hospitals.”
The community levels map demonstrates the severity of spikes by labeling state counties as red, yellow or green in relation to high, medium or low levels of Covid-19.
“What [DHEC has] stressed over the course of the pandemic is not necessarily that those daily case counts are incredibly important, but more to focus on the negative outcomes [such as] hospitalizations, severe illness and death,” said Louis Eubank, the director of DHEC’s Covid-19 Coordination Office. “And since we’ve seen an increase in the non-reportable tests, the numbers that DHEC reports now on a weekly basis seem lower than they have at other points in the pandemic.”
While it’s important to realize the virus is still present in every community in the state, Eubank said, the CDC created the map as a tool for the public to see the outcomes of viral transmission in the areas in which people live, travel and vacation.
“[County levels] also give families and individuals information as to their risk level based on their current health,” Eubank told the Charleston City Paper. “The situation could be very different for someone who’s immunocompromised — they may need to take different actions than someone like me who’s healthy and in their 30s. [The] levels really give you a tool to make those personal health decisions that are right for you.”
On wastewater analysis
Wastewater testing detects Covid-19 the same as you would in the nose or in the back of the throat, Traxler said. An analysis is performed on specimen samples to determine how much Covid-19 is present in wastewater to gauge the burden of infection in communities.
“Wastewater — that is one of the best metrics,” Sweat said. “It’s relatively easy to do and it predicts faster than the case rates by about two weeks, so it gives you an early warning. The problem we’re facing is [DHEC] stopped doing it in Charleston, the largest city in the state.”
Traxler said the issue with no samples being collected in Charleston after last August was a result of staffing shortages.
“The [plant is] submitting samples still as [it is] able, and as soon as staffing improves, [the plant is] committed to going back to the twice-a-week submission,” she said.
To Traxler, tracking the seriousness of cases takes precedence over tracking the quantity of Covid-19 present in communities.
“Certainly wastewater can give us information about what the viral burden is in the community,” she said, “but it doesn’t tell us anything about the severity of the virus.”
Chelsea Grinstead is a reporter with the Charleston City Paper, where this story first appeared. Have a comment? Send to: feedback@statehousereport.com
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