Why scientists say wastewater monitoring should continue despite low COVID-19 levels
Despite most wastewater sites across the country reporting some of the lowest levels of COVID-19 since the analysis began, some researchers say this type of surveillance should continue so Canada can be prepared for the next pandemic.
Wastewater monitoring gained prominence in recent years by providing health officials with an overview of the rate of illness among Canadians during peaks in the pandemic. But its value beyond the coronavirus was quickly realized as a critical public health tool that could help protect people from future harmful infections.
Of the 39 sites followed by Canada’s Dashboard for COVID-19 wastewater monitoring, recent data shows that about 60 percent report falling levels of the virus. The rest of the sites are stable or slightly lower than their previous readings.
“In the past, I would say, several weeks, we’ve seen a relatively consistent downward trend,” said Dr. Guillaume Poliquin, vice president of the National Microbiology Laboratory, part of the Public Health Agency of Canada (PHAC).
Wastewater reporting began in 2020, not long after the pandemic was declared by the World Health Organization, with more and more locations being added.
While the amount of virus on many of PHAC’s sites appears to be at its lowest point since reporting began, Poliquin said there is a caveat.
“The techniques that are used, how accurate they are, how sensitive they are, have generally gotten better over time,” he said.
“Monitoring has changed over time. It’s not always comparable, but the trend is certainly reassuring.”
During the pandemic, it became clear that levels of COVID-19 will fluctuate based on the time of year. Disease spread is usually lower in the warm summer months, one reason being that people spend more time outdoors.
At the same time, 80.5 percent of Canadians are fully vaccinated against the virus and more than 4.6 million have become infected. according to PHAC data – although the website notes that due to changes in testing, the number of cases could be even higher.
How important is supervision?
The practice of collecting wastewater from different communities and analyzing it for COVID-19 is a public health tool that researchers say is useful for predicting disease trends and supporting public health policy decisions. But it’s also a strong indicator of things to come, as experts can tell if a new strain of the virus has emerged.
Initially, 21 percent of Canada’s population was monitored, but now that has grown to more than 60 percent nationwide, Poliquin said.
Questionnaire results published last month in The Lancet journal show that Canada was one of the top countries, of the 43 participating countries, whose wastewater monitoring efforts covered the majority of the population. The article further highlights how important these types of testing tools have proven to be in detecting current and emerging health threats.
Although the COVID-19 pandemic was recently downgraded from global emergency statusongoing monitoring of wastewater is still very important, said Eric Arts, Canada Research Chair in Viral Pathogenesis and Control at Western University in London, Ont.
“It’s too easy for the general public to see it and say, ‘Well, [COVID-19] isn’t there anymore, so why bother with this?’ And it’s getting the information out that says… “You don’t usually listen to the weatherman, but when you see a storm coming in, you really wish you had listened,” Arts said in an interview with CBC news.
“It prepares our healthcare system for an oncoming wave.”
Whether that’s a new sub-variant of COVID-19 or a range of other infectious diseases, Arts said advance warning could help move the healthcare system forward by rolling out protection and preventive measures.
Wastewater could indicate next pandemic
The federal government also routinely checks wastewater for polio, mpox (formerly known as monkeypox), flu, and respiratory syncytial virus (RSV).
But Arts said he’s most interested in using wastewater to get ahead of the unknown.
“[There are] new pathogens that can jump into the human population that we are not fully aware of,” he said.
But if scientists don’t know what they’re looking for, how can they tell it’s in the wastewater?
“There’s been a rapid advancement in technologies, and we can now track things that are new and coming into the population, as long as we keep these surveillance programs,” he said.
Arts said he is part of a program looking for a way to monitor all possible strains of coronaviruses and flu viruses that can infect humans.
“The tools we have on hand actually make monitoring those tens of thousands of tribes not that difficult and not that expensive,” he said.
“So if something shows up that shouldn’t be in human wastewater, we can say, ‘Hmm, that’s something to keep an eye on,’ and then alert public health authorities.”
Governments and health officials, he said, could make vaccines for these other potentially infectious strains and have them on hand for mass production should a pandemic break out.
But there is some concern among those in wastewater monitoring that, despite how essential this new technology is, monitoring could be reduced if governments tighten their budgets.
Will monitoring continue?
The federal government’s national wastewater monitoring system is currently working with local researchers and laboratories to collect information from key locations. In addition, some provinces and territories fund their own efforts to monitor wastewater on a more local level.
At the moment there is no obligation for provinces to collect this data, nor is there a set national strategy around a standardized procedure or a collaborative database to store this information.
Wastewater researchers are calling on Ottawa to develop a national strategy that will consolidate this data and better inform the country’s public health status.
The COVID-19 pandemic has shown scientists how useful wastewater can be for detecting infectious diseases. Now it’s being used to help identify other outbreaks, including monkeypox and polio.
While Poliquin, of the National Microbiology Laboratory, said he doesn’t have a “definitive” answer on next steps for this surveillance system, he told CBC News that talks are ongoing and work is underway to support and expand it.
“The technology has proven its worth,” he said. “There’s a lot of potential here and now that the network and infrastructure are in place, we want to continue to support it.”
Poliquin said its scale is also cost-effective, with an individual PCR test costing $50 to $100 per person and a wastewater sample test costing $100 to $200.
For a national strategy to be effective, Arts said, the government needs to get all public health agencies on board, look at standardizing the procedure across the country and ensuring that the work of specific centers is consolidated.
Border security top priority, say researchers
But if governments decide to scale back this type of warning system, researchers say it’s paramount to keep monitoring Canada’s points of entry, such as borders and airports.
“Twenty-five to 30 percent of Canada-US trade crosses the border at Windsor-Detroit, making it the strategic location to place resources to monitor for diseases emerging in the country,” said Mike McKay, executive director from the Great Lakes Institute for Environmental Research (GLIER) at the University of Windsor, in Windsor, Ont.
McKay, who has been monitoring wastewater in southwestern Ontario and parts of the United States since the early months of the pandemic, said this type of oversight will also help the private sector, making supply chains more resilient.
He said GLIER is working with groups from the University of Guelph, University of Waterloo, York University and University of Toronto to pitch a cross-border surveillance program to the federal government.
This includes monitoring in Ohio, Michigan and in Windsor, as well as the Fort Erie, Ont., and Buffalo, NY areas, he said.
The application will be submitted in September and Ottawa is expected to make a decision early next year. If accepted, the program would be part of a government-funded pandemic preparedness initiative.
