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Our sewage isn’t as healthy as we might like – even by sewage standards.
While far lower than the viral load recorded in January, levels of SARS-CoV-2 detected in wastewater increased significantly after the mask mandate was lifted earlier this spring. However, those levels dropped significantly through May before ticking up at the end of June, according to data recently released by Metro Vancouver.
On March 10, provincial health officer Dr. Bonnie Henry announced the mask mandate was being lifted.
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The decision was being made, Henry explained, due to a drop in rates of transmissions as well as a “consistent decrease” of the virus in wastewater.
Beginning in April, we thought it would be a good idea to take a quick look at the rates of virus in the wastewater at the Annacis Island treatment plant and see where the rates were and where they are. But first, a quick explanation of how it’s done.
How it’s done
Three times a week, researchers from the B.C. Centre for Disease Control and UBC examine untreated wastewater, testing what they find to track rates and possible mutations in COVID-19.
“Studies have demonstrated that approximately 50 percent of COVID-19 cases have the virus in their feces,” said Dr. Natalie Prystajecky, program head of environmental microbiology at the BCCDC Public Health Laboratory while speaking to Environmental Science & Engineering Magazine.
By getting separate data from each wastewater treatment plants, the information can be an early indicator of COVID-19 within the community, lead researcher Dr Melissa Glier told the Burnaby Beacon.
“It’s most informative for establishing trends—to see the increasing or if it’s stable or decreasing within the incidence in community cases,” Glier said.
At the beginning of the pandemic, researchers detected SARS-CoV-2 in the city of Amersfoort before any COVID-19 cases had been confirmed in the city.
The data can serve as a tool for health authorities to judge whether the health measures being used are effective. However, the testing can’t offer a definitive account of the number of British Columbians who are infected or contagious, according to a release from Metro Vancouver.
Where we were
In early January, when daily case counts in Fraser Health were roughly in the 1,600 range, researchers found 406,000 billion gene copies of SARS-CoV-2 in one day’s worth of wastewater.
By Valentine’s Day, that figure had plummeted to 53,000 billion copies, a drop of nearly 87 percent. By that point, daily case counts in Fraser Health were in the 500-800 range.
Judging by wastewater reports at Annacis Island, the viral load continued to decrease through early spring, dropping to 29,000 billion copies by March 7, just before Henry moved to ease restrictions.
Where we are
After seven weeks in decline, the viral load recorded in the wastewater at the Annacis Island treatment plant ticked up last week.
Three tests taken between Sept. 14 and 19 added up to approximately 159,335 billion gene copies, according to the latest figures released by Metro Vancouver. Those tests represent a 40 percent increase from the previous week.
Between Sept. 7 and 12, researchers recorded three tests totalling 114,098 billion gene copies – the lowest one-week total since mid-March.
The viral load hit a peak in early July when researchers documented three tests that added up to 296,003 billion gene copies. The viral load subsequently trended downward throughout much of July and August, dipping by approximately 60 percent over the space of two months before rebounding last week.
- Sept. 14-19: 159,335
- Sept. 7-12: 114,098
- Aug. 31-Sept. 5: 126,534
- Aug. 24-29: 137,362
- Aug. 17-22: 158,944
- Aug. 10-15: 162,046
- Aug. 3-8: 182,272
- July 27-Aug. 1: 188,281
- July 20-25: 249,623
- July 13-18: 223,505
- July 6-11: 296,003
- June 29 – July 4: 242,207
- June 22-27: 193,611
- June 15-20: 176,626
- June 8-13: 170,730
- June 1-6: 177,852
- May 25-30: 195,530
- May 18-23: 227,766
- May 11-16: 230,498
- May 4-9: 250,547
- April 27-May 2: 315,339
- April 20-25: 335,681
- April 13-18: 282,196