CLEVELAND, Ohio – Researchers across Ohio are studying what you flush to get a jump on the spread of the COVID-19 coronavirus in your community.
The idea is simple.
People often shed coronavirus before they exhibit symptoms and get tested. But traces of that virus show up immediately in bodily waste. By monitoring raw sewage, health officials might get an early warning about a surge in cases.
“People could be shedding the virus and not even know it,” said Rebecca Fugitt, assistant chief of the Bureau of Environmental Health and Radiation Protection at the Ohio Department of Health.
How does it work?
Once an hour over each 24-hour testing period, wastewater treatment plants collect samples of sewage flowing into the plants, Fugitt said. The samples are then sent to labs for analysis.
Researchers look for coronavirus RNA in the samples, measuring it in terms of millions of genes per day. Over time, that data provides a baseline measurement for the community served by the treatment plant, Fugitt said.
If a rise in those gene copies is observed, that can give health officials early warning that cases in the community are on the rise, allowing them to take preventive steps.
Fugitt estimates that sewage sampling provides warnings seven to 10 days sooner than an alert from diagnostic test results from patients.
“This is all about trends and the data,” she said, “If we start to see a change upward, … if we start to see an uptick, then we ought to be able to see what’s happening to cases.”
Can the testing predict the number of cases in an area?
No. At least not yet.
The testing only shows the level of the coronavirus RNA present in the raw sewage flowing into the treatment plant. But researchers are working on modeling that might allow case load predictions, Bohrerova said.
It’s tricky because there are many factors to build into the modeling, including:
The number of people living in a plant’s service area.Other materials in the wastewater that could affect the samples.The sewage temperature.How far the wastewater must travel from a household to the plant.
“One of the big uncertainties is how much do people shed,” Bohrerova said.
She likened the modeling to those used to predict hurricane paths. The models generate many possibilities used to predict a path.
“The same way you see a hurricane map with a line that’s surrounded by a cone,” she said.
The Ohio Department of Health, partnering with the Ohio Environmental Protection Agency, the U.S. Environmental Protection Administration, the Ohio Water Resources Center at Ohio State University and several other universities, have been analyzing samples taken since June at wastewater treatment plants around the state.
The effort grew out of a request by Gov. Mike DeWine after he read an article about wastewater “surveillance,” the term associated with this kind of testing, Fugitt said.
The project is funded with $2 million from emergency coronavirus relief funds from the federal government.
Can the public see the results?
Yes. The state Health Department began posts test results online for each site via an interactive map and presents answers to frequently asked questions.
How often is testing done?
Initially once a week.
But an effort is underway to expand that to twice a week, Fugitt said. About half the treatment plants in the network have done so already.
Why is more sampling needed?
More sampling allows researchers to more quickly establish the baseline levels and more rapidly observe changes, said Zuzana Bohrerova, the associate director of the Ohio Water Resources Center, the federally designated water research institute in Ohio.
That in turn allows labs to more quickly determine if an increase in coronavirus RNA is a one-time anomaly or a trend, expanding the early warning window.
Testing every day would be best, Bohrerova said, but that is beyond plant capabilities now.
How broad is the network?
The first efforts targeted treatment plants serving seven of Ohio’s largest cities – Columbus, Cleveland, Cincinnati, Toledo, Akron, Dayton and Youngstown.
Now samples are collected from 36 treatment plants. In Greater Cleveland, three Northeast Ohio Region Sewer District plants, Akron’s treatment plant and a plant in Lorain are part of the network.
Where are the labs?
Ohio State, Kent State, the University of Akron and the University of Toledo all have testing labs.
Bowling Green will be added soon, as will a second OSU lab, Fugitt said, allowing for samples from 10 more treatment plants to be tested.
The state also intends to add a commercial lab that would expanding testing to another 25 plants.
Is wastewater surveillance a new science?
In the 1990s, it was used with efforts to eradicate polio transmission.
“Testing sewage for poliovirus RNA is four to five times more sensitive in detecting outbreaks than monitoring communities for an atypical increase in cases of acute flaccid paralysis and has allowed entire communities to be continuously monitored,” researchers from the Department of Public Health in Syracuse, New York, wrote recently in Nature Biotechnology.
Use of wastewater surveillance to detect coronavirus began gaining traction in the spring as states were beginning to reopen, sparking fears of increased COVID-19 spread.
“There is real hope that this can be a sensitive, early warning,” Peter Grevatt, CEO of the nonprofit Water Research Foundation said in an interview with the health-oriented news site STAT.
Over the summer, the Centers for Disease Control and Prevention pitched the idea as a new tool for understanding spread of the coronavirus.
Could sewage surveillance have other applications?
Among other uses, it could influenza outbreaks or the level of use of opioids.