Researchers in municipalities in six provinces are already testing wastewater for traces of SARS-CoV-2, the virus responsible for the disease. Many infected people shed the virus in their feces, even if they don’t have symptoms, the researchers say. But this type of test uses samples from wastewater treatment facilities and shows the results for an entire community. Researchers are currently unable to pinpoint the exact locations where epidemics are occurring.
“We all go to the bathroom, whether you have COVID or not, whether you are symptomatic or not,” said Dr. Doug Manuel, principal investigator at The Ottawa Hospital involved in the program.
“It’s a way of doing a survey or a census on everyone, every day. Instead of testing thousands of people, we can just test the sewage system once a day at the treatment plant.
The federal COVID-19 Immunity Working Group is supporting the efforts of several laboratories to use this technology to detect outbreaks that are occurring where the most vulnerable Canadians live.
The University of Ottawa, the University of Toronto and Ryerson University are working together on the project and their work is supported by this working group, said Bernadette Conant, CEO of the Canadian Water Network. A team from the University of Alberta is also planning to begin testing in long-term care homes with support from the federal government, she said.
Conant’s nonprofit launched a Wastewater Coalition in Canada to help coordinate the work of researchers across the country and to provide technical advice to scientists, laboratories, wastewater treatment services and to public health authorities.
“You want to know the neighborhoods where testing might need to increase, or where there are hot spots,” Conant said.
Health officials in the United States say such sampling may have helped them prevent an outbreak at the University of Arizona. When the sewage tests in the dormitories came back positive for COVID-19, two asymptotic students were identified and quickly quarantined.
“This could pick up an early signal”
Robert Delatolla is an engineering professor and researcher co-leading the University of Ottawa program. His work of daily monitoring the capital’s wastewater and posting the results online has caught the attention of the Prime Minister’s chief science advisers and the Public Health Agency of Canada.
Delatolla’s group plans to test samples of individual sewers connected to long-term care buildings in Ottawa and the Greater Toronto Area.
“He could pick up an early signal,” he said. “It could be like a smoke detector signaling that things are starting to come online, that epidemics are happening.
“By being able to monitor a facility that is functioning well and that does not have an outbreak, sewage is a potential tool to actually catch when this outbreak first occurs. ”
Delatolla reports on tests his team performed on July 17 that detected COVID-19 levels suddenly rising 400% at the Ottawa water treatment plant. The surge was discovered in sewage two days before Ottawa Public Health reported an increase in the number of people testing positive, he said.
Tests can detect the end of an epidemic
Dr Alex MacKenzie is a Principal Investigator at the CHEO Research Institute, which co-leads the team in Ottawa. He said the sewage test has acted as the “belt and suspenders” supporting the data epidemiologists get through swab testing sites – the data he says is “flawed” because not everyone ‘is not tested.
“It’s difficult to get a clear idea of the exact number of people infected in the community,” MacKenzie said. “We have the advantage here in Ottawa that we actually have a different window. ”
Researchers said more than 910,000 Ottawa residents now provide them with test samples through the sewage treatment system – more than 90 percent of the city’s population.
MacKenzie said applying wastewater testing in long-term care homes could be a way to ease the strain on frontline workers.
“It will be a way to monitor the epidemic within a facility and know when it has actually stopped,” he said. “So that’s going to offload some of these individual testing resources that we’re doing, ideally. ”
‘You would be able to intervene more quickly’
Currently, long-term care homes perform surveillance tests on residents every week or two. Residents are sometimes forgotten during this time, said Dr. Vera Etches, Ottawa’s chief medical officer of health. Wastewater testing could help monitor COVID-19 between these testing periods.
“You would get the signal potentially sooner,” she said. “So you would be able to intervene more quickly. ”
Dr Etches said this was important because “there can be a lot of exposure and a lot of spread” when people are asymptomatic, or in the days before patients start showing symptoms.
“Eighty-eight percent of the people who have died from COVID so far have been residents of long-term care homes,” she said. “This would therefore be an opportunity to try to limit this result. ”
But there are still challenges with testing.
Delatolla said rainwater can dilute samples and chemicals in wastewater can change them, causing variance in samples. Public health officials don’t yet know how quickly the virus appears in wastewater once someone contracts COVID-19, Dr Etches said.
She said she was using both COVID sample results and wastewater scans to get a better picture of outbreaks because the science is not advanced enough to depend solely on wastewater testing.
The COVID-19 Immunity Working Group has said funding deals for its most recent set of studies are not yet finalized, so it cannot comment publicly at this time.