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Wastewater surveillance now critical to detecting COVID-19 in B.C. as few eligible for tests

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VANCOUVER -

Now that B.C. health officials have dramatically limited who can be tested for COVID-19, wastewater surveillance has become the most important indicator of how many people are infected with the virus. 

Metro Vancouver, which handles water and sewage systems for much of the Lower Mainland, has been working with the B.C. Centre for Disease Control and UBC to track the coronavirus, which is expelled in stool by roughly half the people who get infected, whether they know it or not. 

"It's independent of the testing guidelines and also independent of test-seeking behaviours," said Natalie Prystajecky, the environmental biologist leading the BCCDC team. "Waste water detection was a nice research project that was supplementary for a long time and now you'll see across Canada that there's so much more attention, that it's making it into the public health reporting, it's front-page news." 

She said the results have been consistently mirroring pandemic waves tracked by lab-confirmed testing, until December. That's when the Omicron variant hit the province and testing centres were overwhelmed by demand and the testing system collapsed as the public was discouraged from getting tested, whether they had symptoms or not.

Then last week, the B.C. Centre for Disease Control quietly updated its testing guidance and now Vancouver Coastal and Fraser Health are denying both rapid tests and lab-based PCR tests for people unless they are unvaccinated adults, those who are moderately or severely compromised and people who live and work in high-risk settings, which includes health-care workers, first responders, congregate living settings and remote and Indigenous communities.

WORKSAFEBC ADVICE AN INDICATION OF LOOMING ISSUES

Many British Columbians are taking to social media to express frustration they can’t get tested, with some worried about implications for long-term health-care if they don’t have a definitive diagnosis, and others not wanting to expose loved ones who are high-risk.

Family doctors and the provincial health officer alike are assuring the public that medical care will be available, regardless of test results, and that everyone should be avoiding care homes or vulnerable family members if they feel at all unwell.

WorkSafeBC became a topic of discussion on Monday, when the agency tweeted that, “Having test results at the time you file your claim may speed up claim adjudication.” CTV News asked to speak with someone on the matter, but a communications staffer said no one was available and that they are reviewing their COVID-19 policies, but in the meantime, “Ideally, test results will be available, but if not we consider the available evidence and weigh that in light of all of the evidence provided by the worker and employer.”

LONGER-TERM QUESTIONS ABOUT TESTING AND SURVEILLANCE

University of Victoria school of nursing professor, Damien Contandriopoulos, who also has a doctorate in public health, raised concerns about the BCCDC’s public reporting methods, which can be impacted by rainwater or other factors. In Ottawa, for example, they publish COVID-19 levels that’ve been normalized for variables.

"Overall, the province could be doing more tests and decided not to," he pointed out, and it’s true that B.C. peaked testing on Dec. 23, with 21,163 tests that day, but has now dropped below 10,000 per day. 

"The number of people still dying of COVID is still very high, the pressure on hospitals is extremely high and they’re doing very risky things like mixing positive and non-positive patients, so we’re still very much in crisis mode," he said, suggesting that testing is still useful now and in the future.

"COVID isn't going to go away and I see absolutely no reason to believe this Omicron variant is the last one. Everything suggests we’re going to deal with more variants in the future for years."

Prystajecky said the BCCDC testing and lab infrastructure built up over the last two years is now scrutinizing the tests that are still taken, sequencing up to 4,000 positive samples per week to determine what new variants are arriving from travellers and causing the most severe illness in hospitalized patients.

"Even though we've changed who we're testing, we can still do surveillance on who we test and what's going on in the community," she said. "It still provides a good signal of what's happening."

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