How what we flush could help predict second COVID-19 wave
Toronto researchers look to sewage to track remnants of virus
In Amsterdam, it appeared weeks before the first case was confirmed.
In the northern Italian cities of Milan and Turin, it was already there in wastewater in December, well before patients started showing up sick in hospitals.
And now in Toronto, researchers at Ryerson University are looking to sewage to track remnants of the virus that causes COVID-19, hoping that what we flush down the toilet can help provide an early warning system for a dreaded second wave of the disease. It could even identify spikes in hot spots around the city, they say, and no one can opt out.
“Everybody contributes to my research every single day,” Kimberley Gilbride, a professor of chemistry and biology, said with a laugh.
“Everything your body doesn’t want ends up in your poop.”
She and Claire J. Oswald, an associate professor in the department of geography and environmental studies, were already part of Ryerson Urban Water, a collective of researchers from different disciplines focused on urban water issues, prepandemic. When the university put out a call for rapid response research on the novel coronavirus this spring, they quickly put together a proposal and were just awarded $100,000 last week. The pair and their teams are among several groups in communities across the country, and the world, looking at tracking COVID levels in sewage.
“(Sewage testing can help find) the unseen pile of embers that might burst into flames again.” BERNADETTE CONANT CEO, CANADIAN WATER NETWORK
They’ll bring untreated wastewater treatment plant samples back to the lab at Ryerson where they’re looking, not for the live virus, but its ribonucleic acid or “RNA signature,” fragments of genetic material that are broken down in fecal matter, Gilbride said.
Because the virus has a long incubation period of up to two weeks, people might not show symptoms for a while, or ever, and might not get tested. But from the beginning they’re shedding the virus in feces. SARS-CoV-2 is known as an “envelope virus” because it has a layer of fat around it. That doesn’t make it to sewage, so it’s not infectious. But the RNA fragments, like a fingerprint, can tell scientists that the virus was there and help them find trends.
Sewage epidemiology can’t replace classic outbreak tools of testing, contact tracing and isolation. But the Ryerson researchers are working with Toronto Public Health, Toronto Water and Public Health Ontario and hope it can complement these other measures. Toronto Water will co-ordinate the samples to support the research, a spokesperson said in an email.
Public Health Ontario will provide scientific advice on the potential of the study and its findings “to inform public health surveillance and action,” a spokesperson confirmed by email. Toronto Public Health spokesperson Dr. Howard Shapiro, associate medical officer of health and director, healthy environments, said information collected from analysis of wastewater samples would be used as an “additional tool” to monitor COVID-19 in the city.
“By looking at the level of COVID-19 activity using this method, we would better be able to determine if COVID-19 infections are increasing, decreasing or stabilizing across the city,” he said in an email.
“The collection of this information could also help us to detect changes in rates of COVID-19 infection among the population more quickly in addition to the information that is collected through the direct testing of individuals.”
Infections are now slowing as regions across the province, including Toronto and Peel, start to reopen.
But, with the virus still around, it’s more important than ever to be vigilant.
“At some point, if we see the detection going up again, we know, oh, there’s going to be some more infectious people in the community in the near future, so we’re warning you guys,” Gilbride said.
This could help public health officials know when and where to introduce more strict restrictions, or ramp up testing in a certain area “so we don’t have another huge spike in cases.”
If all goes well, they hope to start looking beyond the treatment plant to monitor hot spots and look for trends in specific geographic areas, such as hospitals, long-term-care homes, even at airports.
“It’s not like we would be sampling individual houses or anything like that, there’s major privacy issues, more at a neighbourhood scale,” said Oswald. There’s “potential for monitoring certain locations where you might expect a new outbreak to happen.”
Gilbride and Oswald are part of a national COVID-19 Wastewater Coalition through the non-profit Canadian Water Network. Across the province and country, researchers are already providing samples to municipalities on similar projects.
The organization is rolling out a pilot, hoping to co-ordinate the efforts in a way that can be “both rapid and rigorous” and can help determine if the approach could work as a national early response system, said CEO Bernadette Conant.
Sewage testing has been done to monitor drug use in Canadian communities and has also been used by the World Health Organization to look for early signs of polio outbreaks, she said.
The science on COVID-19 in sewage is still new, but several recent studies out of Europe — including in Amsterdam, Turin and Milan, for example — have shown that the virus’s RNA shows up in wastewater.
Conant likens sewage monitoring to something that can help public health officials fighting the COVID fire as they shift from the immediate blaze in front of them to looking for “the unseen pile of embers that might burst into flames.”
She’s hoping for funding for the network to scale it up, as pandemic lockdowns are relaxed and governments try to figure out the right balance for living with the virus.
“As hard as shutting everything down was, opening up is much harder,” she said, and the threat of a second wave is still looming. “Winter is coming.”
Elsewhere, researchers Rob Delatolla and Dr. Alex MacKenzie are sampling twice a week at plants in Ottawa and Gatineau, looking for RNA fragments as well as proteins in sewage. They’re already providing the analysis to Ottawa Public Health.
“It’s still in beta testing,” said Delatolla, an associate professor of engineering at the University of Ottawa.
But so far the data is consistent with testing numbers showing cases going down in the region.
The approach has “tremendous appeal” as places start to open up, fast, added MacKenzie, a principal investigator at the Children’s Hospital of Eastern Ontario Research Institute.
“A real time metric to show things are slipping away here and we need to get back on track.”
Their team has aspirations to look at more targeted geographic areas, examine sewage for antibodies to study community immunity and even conduct “a CSI audit” on past samples, like what’s been done in some places in Europe to see when the virus showed up.
There are some disadvantages to sewage sampling. Wastewater is complex with all the chemicals and products that go down the drain, and trying to find fragments of the virus can be difficult, Delatolla said.
In Toronto, as in many cities, there are parts of the sewer system where storm water mixes in, which can dilute samples. But Gilbride and Oswald plan to be strategic about when they sample to overcome this.
Region of Peel Public Works staff have sent samples to researcher Mark Servos, a biology professor at the University of Waterloo and the Canada research chair in water quality protection, who believes the technique could be scaled up with the help of private labs, validated methods and protocols.
“It could be a powerful tool to support our interpretation of what’s going on,” he said. “And we save some lives.” Phil Dennis, principal scientist for Guelph-based private lab SiREM, said its sister office in Knoxville, Tennessee, is already working on tracking sewage for cities in the United States, as well as several college campuses, some of which are interested in looking at it down to the “dormitory level.”
It could be used to target samples at the pipe for places such as nursing homes, even casinos or large apartment complexes, he said.
Anumber of municipalities in Canada have expressed interest “so I think there’s demand out there.”
“Their first reaction is like ‘ick, sewage’ ” he said.
“But then, when you look at the benefits, you could be monitoring many thousands of people with a couple of tests.”
An early alert sewage monitoring system could have universal use, when COVID-19 is hopefully no longer the kind of threat it is now “to sample for any pathogen that comes into the city,” added Ryerson’s Gilbride.
“Which would leave us in better shape at the end of this for anything coming in the future.”
“As hard as shutting everything down was, opening up is much harder.”
BERNADETTE CONANT CANADIAN WATER NETWORK CHIEF EXECUTIVE