Sewage swirling through drain pipes across Winnipeg could reveal the spread of COVID-19 in the community, but wastewater data remains backed up because the province says it’s "highly technical."
For nearly 18 months, Manitoba public health officials have received regular reports from the Public Health Agency of Canada on the prevalence of COVID-19 in wastewater samples collected at three locations in Winnipeg.
However, unlike a dozen other jurisdictions, including Calgary and Saskatoon, Manitoba does not publish the findings of wastewater surveillance conducted by the federal agency and scientists at the National Microbiology Laboratory in Winnipeg.
University of Manitoba epidemiologist and community health sciences professor Souradet Shaw said with limited access to COVID-19 PCR testing, the importance of studying sewage to understand the epidemic has increased considerably.
People infected with the virus that causes COVID-19 can shed remnants in their feces and monitoring the level of virus in wastewater can provide early indications of increased spread and declines in transmission.
“Although its use for the pandemic is relatively new, (level of virus in wastewater) has shown potential for understanding population-level patterns and trends of the virus, as well as an early-warning system for virus detection." — Souradet Shaw
"Although its use for the pandemic is relatively new, it has shown potential for understanding population-level patterns and trends of the virus, as well as an early-warning system for virus detection," Shaw said, adding results should generally be considered with other COVID-19 signals.
"It certainly isn’t a silver bullet, but in the context of other indicators, it can be helpful for the public to understand where we stand in the pandemic," Shaw said.
NDP Leader Wab Kinew called on the government to be more transparent by providing high-quality pandemic data, including from wastewater surveillance.
"Just give us the guidelines," Kinew said. "What (are) the parameters, what is the COVID situation really like here in Manitoba and what can we expect in terms of future steps."
Kinew said the province appears to cherry-pick the data it shares, which contributes to scepticism among Manitobans.
"The reason that I think the PCs have done that is to try and make a case that is to their political advantage," Kinew said. "The actual solution to that is to just publish this data regularly and completely."
On Jan. 5, the Manitoba government significantly restricted eligibility for PCR testing following a surge of people showing up for swabs and a laboratory backlog that swelled to more than 10,000 samples.
“Just give us the guidelines. What (are) the parameters, what is the COVID situation really like here in Manitoba and what can we expect in terms of future steps." — Wab Kinew
For the past three weeks, most Manitobans have been given rapid antigen tests if they are symptomatic, the results of which aren’t collected by public health. Officials say that policy is unlikely to change. Consequently, two key pandemic measurements — case counts and test positivity rates — are no longer reliable.
Earlier this week, the Free Press asked the province to provide the latest data and analysis it had received from PHAC related to wastewater monitoring in Winnipeg. The public health agency has developed a model to estimate cases in a community based on how much virus is in wastewater.
In response, a spokesperson for the Manitoba government said surveillance data indicated a peak in the viral load in Winnipeg on Jan. 1.
No other information about the results, including the rate of decline in the following weeks, was provided.
A spokesperson said Tuesday that was due to the "highly technical" nature of the data and ongoing analysis.
On Wednesday, chief provincial public health officer Dr. Brent Roussin said the province had not yet reached the peak of the Omicron wave.
Since the start of the new year, there has not been a dramatic decline of COVID-19 in Winnipeggers’ waste, Roussin told reporters.
He described the viral load in the city as "more of a plateau" with significant variability but with current levels fluctuating around the January high-water mark, when an average of 1,540 cases was reported.
“We always have to be cautious in our interpretation of that. But we’ll be looking at most notably the hospital and ICU admissions, as well as some other indicators.” — Dr. Brent Roussin
"We always have to be cautious in our interpretation of that," the doctor said. "But we’ll be looking at most notably the hospital and ICU admissions, as well as some other indicators."
Roussin said his office is working to make wastewater surveillance data public, but the way the federal agency has reported results has delayed publication.
He said the latest trend in case counts, hospitalizations and wastewater data could suggest the Omicron wave will peak in about a week.
Wastewater surveillance data can be a useful tool for the public to weigh their personal risk while in the community and to decide whether more protective measures are needed, said Massachusetts-based infectious disease expert Dr. Emily Hyle.
"One of the ways that anecdotally it’s been powerful is by people’s behaviour changing when that kind of data is publicly available," Hyle said. "I think there’s a lot of power in that as long as the data itself are accurate and as long as the communities from which the sampling is occurring are large enough so that data aren’t identifiable."
Testing reveals only a fraction of cases in the community as some people don’t go for tests or can’t access them, Hyle said. Wastewater surveillance, on the other hand, appears to be a more accurate reflection of the amount of virus circulating in the community when collected correctly.
"If you aren’t able to make it quickly, publicly available, then you lose some of those benefits," Hyle said.
Danielle Da Silva
Danielle Da Silva is a general assignment reporter.