Giggle if you must, but letting scientists and engineers sift through your poop for signs of the coronavirus could save a lot of lives. Researchers at the University of Michigan are looking into whether sampling sewage systems for COVID-19 could sniff out the virus early on, before anyone shows up at a testing center with a fever and bad cough.
So how do researchers go about finding tiny viruses swimming in lakes of your leavings? And how could sewage surveillance help fill in the gaps of the current testing regimen?
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“When I first heard about this new SARS that came out, that’s the first thing I thought of. I wonder if this is excreted in feces and if so could we detect it before we’re seeing it in any communities,” Dr. Krista Rule Wigginton, a professor of civil engineering who’s leading the University of Michigan sewage surveillance research, told The Daily Beast.
As it happened, Wiggington’s early interest into SARS-CoV ( the predecessor of COVID-19 or SARS-CoV-2) gave her the perfect background for researching the current pandemic’s effect on wastewater systems. “I’m not an epidemiologist but I do know wastewater really well,” she said. Her early research focused on the behavior of coronaviruses—from the same viral family as COVID-19—in wastewater systems.
Working with a handful of colleagues, Wigginton quickly got a grant from the National Academy of Sciences and set up shop at Stanford, where she’s a visiting professor, to start sampling sewage from municipalities in the Bay Area to hunt for signs of COVID-19.
Canary in the coalmine
Why would anyone sift through liters of poop when there’s already a testing system being put into place? The idea isn’t to replace the kinds of brain-jabbing nasal swabs that make up the current system but to augment it with a method that can hopefully test more people earlier in the disease.
As the saying goes, everybody poops. It’s the one kind of test where everyone in the neighborhood is definitely contributing a sample on a regular basis. That helps any potential surveillance system make sure that they’re testing as many people as possible for signs of infection.
That’s especially important to capture two groups of patients who have fallen through the cracks of the current testing regimen: the asymptomatic and pre-symptomatic infected.
A number of studies now show that many people—including an estimated 30 percent in Wuhan, China—can carry the virus without any symptoms, awareness of infection, or a reason to get tested. And a recent CDC study of the long-term care facility in Washington which suffered a major outbreak found that half of those who tested positive and later became sick had no symptoms when tested. And it’s those patients who represent one of the biggest problems in containing the spread of the virus.
A recent study by a Dutch team of investigators at the KWR Water Research Institute showed that sewage surveillance might be able to provide that kind of early tripwire.
The team, led by microbiologist Gertjan Medema, sprung into action after the outbreak in China and began sampling the sewage systems of five Dutch cities and an airport in early February. That surveillance confirmed the presence of COVID-19 weeks before the first confirmed clinical case in the country.
“They detected really low levels in their wastewater,” Wigginton says of the Dutch study.
Privacy vs public health
The COVID-19 pandemic and the need to find, trace, and isolate people infected with the virus has raised plenty of privacy concerns. Countries like Israel, Russia, Singapore, and South Korea have developed apps to monitor people’s symptoms and movements to monitor exposure once someone is confirmed positive. The notorious Israeli hacking-for-hire company NSO Group, whose products have been implicated in a number of human rights abuses, is also now touting an app to trace infections.
Everyone may be able to smell your contributions to the local sewage system, but for privacy’s sake, no one can tell who dealt it. “You don’t need to have institutional review board approval to do this work because there’s no way you can trace back where it came from,” said Wigginton.
Dookie detective work
In testing wastewater for COVID-19, researchers are trying to find a few tiny microscopic viruses floating in large ponds of poo. Sampling that wastewater is much more involved than just dipping a swab in a tank.
“A lot of the effort up front is how do we get these low concentrations in big volumes down to higher concentrations in smaller volumes so then we can detect it,” says Wigginton.
Wigginton’s previous research into coronavirus behavior in wastewater found that “these viruses are sticky and they like to stick to the solids.” Since coronaviruses love to stick to proteins, researchers pour fetal bovine serum, a kind of liquid protein derived from calves, into the wastewater to tempt COVID-19 away from your turds.
“What those proteins do is just take up all of the sticky spots. What we’re trying to do is dislodge the virus from the solids, break up the solids, dislodge the virus or the viral RNA, and pull it off into solutions,” says Wiggington. Once that’s done, researchers can concentrate that remaining solution to test for COVID-19. Since wastewater changes in the course of a day, Wigginton’s team is collecting “composite samples where we collect a little bit over 24 hours and you test your composite samples to get an average over a day.”
Tell-all
As it turns out, your morning deuce can reveal a lot about both you and the health of your community. Scientists have been doing sewage surveillance for years and have used it to reveal everything from how much cocaine a city uses to more pressing public health concerns. In Israel, public health officials use sewage surveillance to monitor and suppress outbreaks of polio, which flared up in 2013.
The coronavirus is harder to track in wastewater relative to other diseases and methods of shedding the virus because it has a smaller footprint in your leavings than viruses like polio.
A number of studies from China have shown that the virus is definitely present and detectable in the poop of patients. But it’s much more detectable when testing the gunk from your respiratory system that you sneeze and cough up than the stuff from your bowels. In one study, only around 29 percent of COVID-19 patients tested had their poop show up positive for the virus compared with positive hits on sputum (72 percent) and nasal swabs (63 percent).
Biohazards
As promising as sewage surveillance might be, it’s run into some very recent hurdles thanks to new regulations from the CDC. On March 31, the CDC issued new guidelines for researchers working on concentrating sewage samples in search of COVID-19. That kind of research now has to be performed in a facility rated at biosecurity level two (BSL-2) with personnel using equipment normally reserved for BSL-3 facilities. Biosafety levels are used to spell out the kinds of safety equipment and procedures necessary for safely researching dangerous pathogens (some kinds of research can take place in BSL-2 facilities whereas BSL-3 labs are reserved for more dangerous organisms like anthrax).
“I think it’s going to set back this research a lot because most of the groups doing this research do not have access to BSL 3 equipment,” said Wigginton. “I think the work will be able to go on in other countries. In Europe they’ll keep being able to plow forward on this but this is definitely going to slow us down.”
