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Vancouver sewage a 'treasure trove' for COVID-19 research

Co-op student Ziwen-Jo Ran and Dr. Melissa Glier handle samples in the B.C Centre for Disease Control's public health laboratory. (Courtesy BCCDC)

B.C. Centre for Disease Control study detects coronavirus in wastewater

Steady rise in official case counts correlate with sewage testing

'Thick' samples make separating viral particles time-consuming

VANCOUVER (NEWS 1130) – Your nose isn’t the only source of bodily fluids B.C. scientists are using to track the novel coronavirus.

While nasal swabs are the primary testing method for determining whether an individual has COVID-19, researchers are turning to sewage to test entire communities.

Natalie Prystajecky was leading a B.C. Centre for Disease Control study looking for evidence of diarrhea-causing viruses – such as the norovirus sometimes found in oysters – in wastewater until the beginning of this year, but that research was put on hold when the coronavirus came along.

A ‘fascinating project’

Prystajecky’s team pivoted to study the new virus in Metro Vancouver by analyzing sewage from five treatment plants in Vancouver and Surrey.

“Instead of testing an entire community of people, you could test the wastewater of an entire community and you could understand if there are cases in the community and if the quantity was increasing or decreasing,” she said.

The research is possible because humans shed viral particles in their feces and urine.

In June, Provincial Health Officer Dr. Bonnie Henry called it a “fascinating project” and a potential early warning system that could tip public health officials off to cases of COVID-19.

Virus rise tracked in sewage

At first, weekly samples showed no sign of the virus, but it has since been found consistently since the summer, closely following a steady rise in the official case counts.

“We haven’t yet been in that scenario where we’ve been able to predict that we were about to see an increase in cases, just because we have that sort of steady increase that was happening between August and now,” Prystajecki said.

“I think if we saw a drastic increase in cases, we might see a drastic increase in that amount in the wastewater.”

Do ‘thick’ samples smell?

When the raw sewage arrives in the lab, it is spun at high speeds, or centrifuged, to separate the virus RNA from “all the other material,” Prystajecky explains.

“The most time consuming part of the whole process is actually concentrating the virus from the wastewater sample,” she said. “You can imagine, it can be quite thick.”

The scientists then use a probe to amplify some genes in the coronavirus genome and a dye to detect its presence.

The polymerase chain reaction is the same as the one used to detect the virus in nose-swab samples, but the sewage testing can also detect the amount of virus in a sample, down to just 10 copies.

Asked whether it smells bad in her lab, Prystajecky said, “Not really.”

“We test all sorts of interesting samples in the lab. We are often testing samples for people who have diarrhea or we get samples … that could have an odor. So it’s not unusual for there to be smells in a microbiology lab.”

‘A treasure trove of information’

The BCCDC study is currently slated to go until the end of December, but Prystajecky said she is working with counterparts in other cities to potentially establish a national study.

She said wastewater can be used to track other diseases and even illicit drug use.

“It can be a treasure trove of information for scientists,” she said.