British Columbia

How Metro Vancouver sewage could become the next tool in tracking COVID-19

BCCDC researcher says humans can shed the virus that causes COVID-19 in their feces, even before they become symptomatic.

50% of people who contract COVID-19 will shed traces of the virus in their feces, even before they get sick

B.C. Centre for Disease Control environmental biologist Natalie Prystajecky is leading a project to detect COVID-19 in the waste water of five Metro Vancouver sewage treatment plants. (Michael Donoghue)

It may be number two in your toilet, but it's number one in the hearts of researchers who are using samples from Lower Mainland sewage treatment plants to track COVID-19.

The study out of the B.C. Centre for Disease Control's public health laboratory is made possible because 50 per cent of humans who contract COVID-19 will shed traces of SARS-CoV-2 — the virus that causes the disease — in their feces, according to microbiologist Natalie Prystajecky.

Those viral traces travel through our sewage system and into local waste water, where they become a potential gold mine of information on how the disease is trending.

"I think it has a lot of usefulness to understand, for example, if there is an outbreak in a community with a rapid increase in the number of cases," said Prystajecky. 

"It can be used to ascertain that it's no longer spreading in a population, and it may be able to be predictive, particularly in an area where there's been no COVID before." 

It's known that people can have the virus for days before they become symptomatic or can have the virus and be infectious without exhibiting any symptoms.

Prystajecky and her team have spent six months validating and optimizing testing methods in co-ordination with a network of researchers across Canada.

The Annacis Island waste-water treatment plant is one of five Metro Vancouver facilities providing samples for the COVID-19 study. (Metro Vancouver)

The next step is to start building a database using weekly samples from the five Metro Vancouver waste water treatment plants: Annacis Island in Delta, Iona and Lulu Island in Richmond, Lions Gate in West Vancouver and northwest Langley.

"We only moved to this routine sampling over the last month or so. We're just really getting to know the data," she said. 

Sewage surveillance has proven useful elsewhere as an early warning system or tracking device. 

In the Netherlands, for example, coronavirus was detected in the waste water from a plant in the city of Amersfoort, weeks before the first residents tested positive.

In Saskatoon, researchers recently predicted case counts there will continue to rise in the short term.

Prystajecky has used waste water testing to track norovirus. And the methods have even been used by Statistics Canada to look at drug use in certain parts of Canada, including Vancouver.

Prystajecky says the COVID-19 waste water project is still in its infancy, but over time could have potential as a public health tool .

"There's a lot of interest in this and we're gathering the data to be able to really demonstrate how it best can be used," she said.


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