If Canada’s coronavirus lockdown eases, could sewage act as an early warning system?

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Coronavirus outbreak: Trudeau stresses ‘it will be weeks more’ before government considers easing restrictions
WATCH: Prime Minister Justin Trudeau stresses "it will be weeks more" before government considers easing restrictions amid coronavirus pandemic – Apr 15, 2020

Sooner or later, governments across Canada will have to decide whether to ease lockdowns caused by the novel coronavirus.

Prime Minister Justin Trudeau managed expectations Wednesday, saying that it will be “weeks more” before any relaxation is possible and warning that doing it too early could lead to dangerous new outbreaks.

But it’s clear that, at some point, a new balance will have to be struck between protecting Canadians’ livelihoods and protecting their lives. On Wednesday, Denmark reopened schools across the country for children 11 and under, for example.

When that moment happens, how will we know that it was the right decision, and how would we get early warning if it turned out to be the wrong one?

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Regular testing of sewage for the virus could tell us quickly if there were danger signs, an expert says.

No country started testing sewage for the novel coronavirus more than a few months ago, and so far, the science isn’t able to say what a given community’s infection rate is based on traces of the virus in sewage.

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Coronavirus outbreak: Freeland says it’s ‘premature’ to set a date for lifting of U.S. / Canada border restrictions

What it can do, however, is show if levels of the virus are rising in relation to previous tests.

“One of the biggest, most powerful observations in this is the ability to look for change,” says Bernadette Conant of the Canadian Water Network, a non-profit. “It’s the fact that there’s a change that sort of makes you stand up and say, ‘Hm, I wonder why that’s happening?’”

“My own view on managing this is, is there an issue that we’ve missed the boat? My answer is no because I think the biggest power for this is really for the long term.”

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(A recent study from Harvard warned that we may be seeing the novel coronavirus come and go until 2022.)

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What would the starting point be? Oddly, Statistics Canada keeps a sort of sewage library, with samples from five provinces, to which scientists could refer.

The agency started collecting sewage samples from Vancouver, Edmonton, Toronto, Montreal and Halifax in early 2018 to test them for recreational drugs and has been gathering more ever since, Statistics Canada’s Audra Nagasawa wrote in an email.

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On the second Monday of every month, people in all five cities take samples of sewage from treatment plants, taken over seven consecutive days to keep things consistent. All the samples are stored in a freezer in a Health Canada lab.

“There is no firm plan” to test the samples for the novel coronavirus, Nagasawa wrote, but it’s a possibility.

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“Leveraging the Canadian Wastewater Survey is an option that may be considered given the existing infrastructure with respect to sampling, but [we] need to co-ordinate with scientists and labs with expertise to do this work to make sure that our results are comparable across Canada, and internationally,” Nagasawa wrote.

“To our knowledge, there are already a number of initiatives in place … but nothing is co-ordinated at a national level yet.”

For one thing, it’s not clear how much of the virus ends up being shed into someone’s waste if they are infected, though it’s obvious some does.

“It appears it could be an interesting way to track levels over time (are they going up or down)?” Nagasawa wrote.

Communities wouldn’t have to wait long for results.

“Based on our understanding, the turnaround time could be relatively short. Our sense is that samples could be gathered and analyzed within a week or two, which could allow for provision of short-term warnings and/or emerging problems.”

“At this time, the Public Health Agency of Canada is not aware of any Canadian studies collecting sewage samples for the detection and identification of COVID-19,” spokesperson Marie-Pier Burelle wrote in an email.

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Federal grants are funding 99 coronavirus research projects across Canada, but none concern wastewater testing.

Federal health minister Patty Hadju’s office did not respond to questions about whether the federal government had plans for sewage surveillance, or why none of the funded research related to it.

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Scientists in the United States, the Netherlands and Australia are all turning to their countries’ sewers to try to learn more about the spread of the novel coronavirus. The Dutch study, perhaps the most successful so far, found the novel coronavirus in sewage more or less in lockstep with positive tests on people on the surface. (The novel coronavirus was detected in sewage at Schiphol airport just four days after the first known Dutch case was reported.)

Canada has studied sewage in the past.

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In the early 2000s, a study of sewage from 14 Canadian communities found traces of various pharmaceutical products, including ibuprofen and two chemotherapy drugs. The results differed in some ways from similar studies in Europe.

Last year, Statistics Canada looked for traces of recreational drugs in sewage from Toronto, Montreal, Edmonton and Vancouver.

The sewage appeared to show higher rates of cannabis use in Halifax and Montreal and more methamphetamine use in Edmonton and Vancouver.

The study was part of a larger international project, which found that cocaine was the predominant drug in Europe and South America, while Australian and North American cities showed more methamphetamines.


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