The average person flushes the toilet five times a day, sending waste spiraling from homes, office buildings and businesses into sewers, pipes and test tubes to check for COVID-19.
At least, that’s the hope, says Aparna Keshaviah, a statistician with the data-tracking group Mathematica. In partnership with the Jackson County Health Department and the Tuckaseigee Water and Sewer Authority, Mathematica launched a pilot program in July to see if rural wastewater could show communal spread of the coronavirus.
Wastewater epidemiology has been used to track the spread of polio outbreaks and opioid use, according to the federal Centers for Disease Control and Prevention. Now, researchers have discovered that fecal matter sheds traces of SARS-CoV-2, the virus that causes COVID-19, long before a patient shows symptoms. The early warning signs can give health officials a head start as they work to track new outbreaks, explains Keshaviah.
“I saw the power of this data stream — literally — to overcome biases, lags of information and poor coverage that exist in a lot of traditional data sources,” she says. “We saw this as a really powerful way to overcome the gaps that exist in existing testing methods.”
Wastewater surveillance can detect COVID-19 outbreaks up to nine days before cases are reported to local and state health departments, Keshaviah explains. The process is simple: Scientists take a sewage sample (the dirtier the better, she says) and test for the virus’s genetic signature. Costs run $300-$600, depending on the sample size.
A Yale University study published Sept. 18 identified traces of COVID-19 in sludge earlier than any other testing method. Researchers found concentrations of the virus up to two days before a COVID-19 test was taken, four days before local hospital admissions and eight days ahead of positive test results by reporting date. For communities facing a delay between specimen collection and reported test results, the study says, “immediate wastewater results can provide considerable advance notice of infection dynamics.”
But while scientists can track trace amounts of the virus — a study from the Netherlands could detect one case per 100,000 people — there’s little reliable data to translate the recorded viral load into accurate case counts, Keshaviah says.
The CDC, the U.S. Environmental Protection Agency and the U.S. Department of Health and Human Services are working to develop a national wastewater surveillance system; pilot studies from across the country will guide the eventual plan, Keshaviah says. There wasn’t much research on wastewater testing in rural areas before the Jackson County study, she adds, primarily because viral detection is more challenging with a smaller population.
“The study really adds to the picture of what’s happening in rural communities,” she says. “For an underrepresented region like the mountains, I wanted to make sure there was data in the discussion as this method is validated.”
Smells like success
When the Jackson County team took its first sewage sample on July 28, the wastewater revealed a relatively high viral load for the county’s 44,000 residents. Two days later, students began moving into dorms at Western Carolina University. The next sample, taken Aug. 3, showed another high reading. Three days later, county health officials reported a new spike in cases.
The wastewater data aligned with the COVID-19 cases recorded at the county level and matched proxy measures like doctor visits and a Facebook symptom study, Keshaviah says. “When you look at all of these data sources, you’re essentially seeing the same trend, but the wastewater data gives that information at least a week ahead of time.”
The pilot study allowed the Jackson County Health Department to analyze data and determine how this type of testing could be used to identify future outbreaks, says Melissa McKnight, Jackson County’s deputy health director. Targeted testing in specific neighborhoods would allow officials to pinpoint where the coronavirus is coming from, she continues.
If wastewater testing from a single neighborhood showed traces of COVID-19, McKnight adds, health officials could ask all residents to get tested, hopefully catching asymptomatic carriers before the virus spreads further.
The infrastructure for widespread testing is already in place, Keshaviah adds. Staff at more than 15,000 wastewater treatment plants nationally already take daily samples to test for a range of toxins, bacteria and viruses; it takes “minimal effort” to collect an additional sample to send to a lab testing for COVID-19, says Daniel Manring, executive director of the Tuckaseigee Water and Sewer Authority. “Any tool deemed useful in this pandemic is worth exploring further,” he says, noting TWSA will continue to participate in studies if the data gathered are found to be beneficial.
Full stream ahead
The Jackson County pilot study was funded by a $3,000 grant from Dogwood Health Trust. Now, Keshaviah says, the team is applying for additional funding to expand testing into surrounding counties. Officials in Buncombe and Macon counties are reviewing testing protocols, and Haywood County has confirmed interest in participating, should funding be secured.
In Buncombe County, health officials have recorded approximately 80,000 individual COVID-19 tests since March. But a single test at Buncombe’s central wastewater treatment plant could cover 176,000 people, Keshaviah says.
Health officials are currently unable to track COVID-19 cases linked to out-of-town visitors, but wastewater tests may help gauge how prevalent the virus is in the area — tourists included, Keshaviah hypothesizes. As visitors flock to the region to see fall foliage and to attend events like the Maui Invitational basketball tournament, which will be held in November at Harrah’s Cherokee Center – Asheville, wastewater testing could help measure the impact of tourism on potential coronavirus outbreaks.
“The power of this tool is that it can give an early warning for a second or third wave of infections,” Keshaviah says. “Our hope is to launch this kind of surveillance before these big upcoming tourist events.”