This, however, paved the way for wastewater testing to play an increasingly critical role in monitoring the transmission of COVID-19 within communities, according to Mark Servos, Canada’s Research Chair in water quality protection and professor at University of Waterloo in Ontario.  .
“Sewage is completely independent of whether you will be tested or not – everyone is hurting,” he told CTVNews.ca in a telephone interview on Monday.  “Sewage is really one of our only reliable tools for determining what is happening in terms of community dominance.”
Although recently in the spotlight, the Public Health Service of Canada (PHAC) has been monitoring wastewater samples for SARS-CoV-2 since the fall of 2020. The process involves measuring the concentration of COVID-19 genetic material in wastewater. to understand the prevalence in a community, explained Elizabeth Edwards, a professor in the Department of Chemical Engineering and Applied Chemistry at the University of Toronto.  Edwards is also part of a research team testing COVID-19 levels in wastewater from the greater Toronto area (GTA).
Studies have shown that traces of SARS-CoV-2 ribonucleic acid (RNA) can be detected in the feces of patients with COVID-19, which means that they are more likely to excrete the virus during waste excretion.  From the toilet, their waste enters the sewer system and is transferred to a municipal wastewater treatment plant.  A sample of the wastewater is then collected from the factory and transported to one of the many laboratories across the country for treatment.  Samples are usually collected three times a week.
In the lab, the sample is centrifuged so that its solid components can be separated from its liquid components as it is filtered, Edwards said.  This allows the researchers to extract the RNA from the sample and prepare it for PCR testing.
The PCR test is identical to that performed at COVID-19 clinics with a nasal swab, he said.  Detects genetic material from the SARS-CoV-2 virus and enhances it for analysis.
“Then we can relate the number of copies of this piece of RNA to the volume of water we started,” Edwards told CTVNews.ca in a telephone interview on Tuesday.  “If we know we have 100 pieces in those 500 [millilitres]we can have concentration “.
While PCR tests are also performed on wastewater samples, these tests target a different part of the virus, namely the N or E genes. The N gene, in particular, appears to remain well-preserved in the effluent, Servos said.
Once the data has been collected, the results are reported to the public health units on a regular basis.  The methodologies may vary slightly from province to province, but the goal is to identify existing COVID-19 levels, the Serb said.
INCREASING SIGNALS IN COVID-19 WASTEWATER
One of the reasons why wastewater testing has become so crucial to understanding the extent of the COVID-19 community spread is related to the high transmissibility associated with the Omicron variant, Servos said.
“Before Omicron appeared, we had a very good relationship between our sewage samples… and the number of clinical cases,” said the Serb.  “When Omicron came and flooded everything, clinical trials were minimized to just emergencies. [cases] and the relationship began to fall apart. “
The Ontario Sewage Monitoring Network consists of 14 laboratories working to detect COVID-19 levels in wastewater samples from 174 sites in approximately 70 cities or health areas, according to data from PHAC.  The results from the sewage analysis cover about 75 percent of the total population of the province.
Servos is based in Waterloo, Ont.  area, which includes the cities of Waterloo, Kitchener and Cambridge.  The samples processed through his lab at the University of Waterloo cover about 82 per cent of the area’s population, the Serb said.  As of April 2, Waterloo’s weekly average number of copies of the N gene per milliliter was about 415, representing a steady increase in COVID-19 concentration levels since mid-March.  A major driver of this growth was the rapid spread of the Omicron BA.2 sub-variant within the province, the Serb said.
“We have now seen that BA.2 is almost 100 percent in most wastewater [samples] “that we were studying”, said the Serb.
With the recent Omicron wave hitting Canada, which peaked in early January, COVID-19 sewage levels have risen sharply in Ontario, the Serb said.  After concentrations fell by February, the province is now seeing an increase in sewage signals again, he said.
“A lot of people get COVID at this point and the sewage signal is perfectly consistent with that,” he said.  “It is growing in all areas and we are seeing more and more people being infected with COVID.”
Wastewater data collected from the Ontario COVID-19 Scientific Advisory Board, received April 14, 2022.
Over the past four weeks, Ontario has seen a steady increase in COVID-19 wastewater signals, which will continue to grow, Servos said.  The province is already seeing concentrations well above those investigated in the Delta and Alpha waves, he said.
“The next week or two will be very crucial in trying to understand what is going to happen in this wave of pandemics,” the Serb said.
As part of the Alberta Wastewater Monitoring Initiative, researchers from both the University of Alberta and the University of Calgary collaborated to collect and test wastewater samples throughout the province.  Both universities work with Alberta Precision Laboratories to process samples from 20 locations in 42 cities and communities, which make up 79 percent of the province’s population.
Casey Hubert, a research fellow in geomicrobiology at the University of Calgary, is one such researcher.
In Calgary, Alta, where Hubert lives, he noted a steady increase in COVID-19 concentrations in wastewater collected over the past month or so.  Each data point collected and designed was higher than the previous one, he said.  While the latest data point shows a slight decrease in the amount of SARS-CoV-2 RNA copies detected per day, Hubert said he expects concentration levels to continue to rise overall.
“Unfortunately, I expect to see the data continue to grow,” Hubert told CTVNews.ca in a telephone interview Wednesday.
In British Columbia, wastewater samples are collected from five different locations in the Vancouver Metro and processed by the British Columbia Centers for Disease Control in collaboration with the University of British Columbia.  The samples cover about 49 percent of the county’s total population, says Natalie Prystajecky, a microbiologist at the BC Center for Disease Control public health lab.
Looking at the data from the Ontario sewage analysis, which Prystajecky said often preceded British Columbia in terms of pollution waves, she is slightly concerned.
Data from its province show a steady increase in COVID-19 concentration levels and in wastewater samples.  But those levels are nowhere near where they were at the top of the Omicron wave earlier this year, he said.
“There is nothing to worry about at this point,” Prystajecky told CTVNews.ca in a telephone interview on Wednesday.  “We are very far even from the middle of the Omicron peak.”
VARIABILITY IN DATA CAN LEAD TO “ERROR MARGIN”
One of the advantages of the sewage test is how cost-effective it can be, Hubert said, especially compared to individual PCR tests.  While it may be more expensive than clinical trials, it could be a fairly quick way to investigate COVID-19 levels in a large group of people, he said.
“It’s a very effective tool when you can take a single sample to cover a large part of the population,” Hubert said.  “In a city like Edmonton or Calgary, if you could do a single PCR test and get a signal from a million people, this is a really powerful way to assess the pandemic trajectory.”
It also does not depend on voluntary participation in the same way as the PCR test, the Serb said.
“It does not matter if you can not get tested or you are vulnerable or asymptomatic,” he said.  “Sewage collects it, so this is a complete signal that is independent of clinical trials.”
There are, however, some challenges with wastewater testing, which stem mainly from the variability of the data produced by each sample, Edwards said.
Processing facilities vary in age and design, he explained, which may lead to greater sample dilution at some sites compared to others.
“There is a large margin of error, easily 50 percent,” Edwards said.  “But what else can we do?  “We have to look at the data we have, no matter how noisy and uncertain, and make our best predictions.”
Several other factors can affect COVID-19 signals in wastewater, Hubert said.  In Calgary, for example, rainwater is kept separate from sewage collected in the sewer system, he said.  In other cities, both are combined, which would reduce the covid-19 signal in these samples.  Different communities also have varying proportions of domestic and industrial water use contributing to their municipal wastewater.
Hubert said he admits that while it may be tempting to compare levels between different cities or areas of health, those comparisons will not necessarily be accurate.
“Every sewage system for every community will have many variables,” he said.  “We just keep these variables …