With publicly-funded PCR testing scarce and reserved for those considered “vulnerable” in Ontario, the province has begun to lean on wastewater surveillance from municipalities a little more as a potential alternative to track viral activity.
Last March, the Ford government invested in just over a dozen research and academic institutions to create a surveillance network to test wastewater samples taken from communities across Ontario.
“Together with clinical and public health data, wastewater monitoring can help local public health units identify potential COVID-19 outbreaks and enable more timely decisions about how and where to mobilize resources in response,” environment minister Jeff Yurek said after handing over $12 million in wastewater collecting initiatives.
Two years into the program, an estimated 75 per cent of Ontario’s population is now within the Ministry of the Environment’s (MOE) coverage area for the Wastewater Surveillance Initiative (WSI).
In recent weeks, the director of the Ontario Science Advisory Table Dr. Peter Juni and the province’s chief medical officer Dr. Kieron Moore have often cited the measure in reporting trends in COVID detection.
Toronto Public Health’s medical officer of health revealed in mid-January staff would be collaborating with academic partners to expand on the tool after discovering connections with the city’s clinical COVID numbers.
In Ottawa, the measure has been successful enough that the local public health unit regularly reports the data on its COVID-19 dashboard.
But not all medical officers are singing the praises of the measurement.
Hamilton’s medical officer of health on numerous occasions has publicly said the data “hasn’t been as useful” and “doesn’t correlate as well” with other COVID data sources the city’s public health unit has been using, like per cent positivity and COVID-19 hospitalization data.
“We definitely have seen in other systems, in Ottawa and other places, it has been very successful in terms of looking at overall Omicron data or COVID data,” Richardson said in a city update in January.
“It hasn’t been as useful here in Hamilton; we’re betting that’s something to do with our system, the way it’s set up.”
A spokesperson for the city says they are still engaged in the WSI collecting samples for a research group at the University of Ottawa but from fewer sites since the startup two years ago.
“Since 2020, Hamilton Water has collected samples from a number of locations across the city including Ancaster, Dundas and in the lower city,” Emily Trotta told Global News in an email.
“At this time, sampling is only active at the Woodward Avenue and Dundas Treatment Plants.”
Prof. Robert Delatolla with the department of civil engineering at the University of Ottawa didn’t share Richardson’s view of results coming from the Hamilton samples, insisting research has been “indicating a strong correlation to hospitalizations.”
“The wastewater data has shown a divergent trend to the daily new cases clinical testing data in Hamilton since the modification of COVID-19 testing eligibility in province,” Delatolla told Global News in an email.
“The data has also been able to identify increases and decreases of disease burden in the city.”
The science behind the method involves the SARS-CoV-2 virus’ appearance in the gastrointestinal tract of an infected individual and its eventual expulsion through human feces.
Surveillance involves collecting samples at water treatment plants, cleaning them to isolate and measuring trace levels of coronavirus particles.
Prof. Lawrence Goodridge, who’s leading researchers at the University of Guelph as part of the provincial initiative, says collections from wastewater treatment plants and passive sampling are the common methods of retrieving specimens.
Collection from the plants is through an auto sampling device which sifts amounts from the wastewater stream, but the passive method in a targeted campaign involves more manual work.
That process requires the popping open of a manhole cover and the dropping of a ‘ball’ or a ‘torpedo’ on a rope to collect samples travelling upstream.
“So the device is lowered to the bottom of the manhole, where the wastewater is flowing,” said Goodridge.
“Typically, these devices have holes in them so water can flow through the device and in contact with cheesecloth or other material that catches the virus.”
Goodridge says the samplers are then taken back to a lab and similarly genetic material is checked via a PCR test.
The compiled data is then sent to the Ministry of Health where it’s aggregated into a global view of trends that can be accessed by each public health unit in the province.
Early response and regional tracking data are advantages wastewater testing can provide for communities according to an infectious disease expert at Massachusetts General Hospital.
Dr. Emily Hyle says the science could help with the timing of public health campaigns for communities where more virus is circulating.
The idea is to identify trends and implement prevention measures in the hopes of decreasing potential hospitalizations.
“By the time you have enough circulating virus among particularly vulnerable communities, like the elderly or immunocompromised, you see that reflected in hospitalization and actually you’re acting a bit too late,” Hyle said.
“Getting a sense of when there’s an increase in circulating virus can be helpful at targeting and messaging towards social distancing and mask wearing behaviours.”
Hyle says over the two years of the pandemic, changes in estimated levels of wastewater in the Boston area have “correlated well” with the different waves and surges of COVID.
As average levels increase, she says surges can be a detector for new variants of concern or waning immunity among those vaccinated.
“I think the ability to get kind of a widespread surveillance picture has been quite good from our wastewater data over the time that it’s been in effect,” said Hyle.
Niagara Region is also a part of the Ontario program, having volunteered for the pilot project in 2020.
Acting medical officer of health Dr. Mustafa Hirji said initially the campaign was successful and showing some correlation of virus fragments detected in wastewater and surges in infections.
Since May of 2021, wastewater has been tested across all six of Niagara’s regions local treatment plants.
Despite some positive trends earlier in the pandemic, Hirji says some recent patterns have “not made” sense with a lot of “ups and downs.”
“I focused really on the Grimsby wastewater treatment plant, where it seemed to imply that there wasn’t really any COVID-19 going around in December when we were, of course, detecting lots and lots of infections,” Hirji said in a regional update on Jan. 31, 2022.
The Niagara top doc suggests the testing may be more conducive in communities with dense urban areas, with higher populations creating larger sample sizes.
“We have a relatively small population spread across six wastewater treatment plants, we are ending up with much more unreliable data and it’s harder for us to really interpret what a pattern is there,” said Hirji.
Goodridge, whose team collects samples from Niagara Region, concurs with Hirji’s assessment that “undertesting” in Niagara likely has much to do with the variable results.
He also suggests travellers, like those regularly crossing the border into Niagara Falls, may also sway results since they are not a part of the local community.
“If those people are positive for COVID, we pick that up and that will not necessarily be reflected in the cases (data) for Niagara,” said Goodridge.
Ontario’s WSI is the largest surveillance network in Canada sampling at over 170 locations across all 34 public health units, according to the MOE.
“Currently, samples are collected from 117 community sites and 57 upstream high-risk congregate locations,” spokesperson Lindsay Davidson told Global News in an email.