Wastewater surveillance and testing in Canada
The following is a summary of best available evidence from trusted sources that provide high quality information on the nature of SARS-CoV-2 wastewater surveillance.
- Published: January 15, 2021
Summary of Evidence
The Wastewater surveillance for population-wide Covid-19: The present and future literature review mentions that the detection of SARS-CoV-2 in wastewater may be a useful tool for inferring prevalence of COVID-19, and to detect early signs of increased transmission at community levels. In its Wastewater Surveillance guidance, the Centers for Disease Control and Prevention (CDC) highlights that data from wastewater testing can complement and enhance existing COVID‑19 surveillance systems by providing data from communities where timely COVID‑19 clinical testing is limited. The Wastewater surveillance for COVID‑19 evidence synthesis noted that countries including Australia, Spain, Italy, Netherlands, China, the United States of America, Germany, Japan, India, Czech Republic, Brazil, and Ecuador detected SARS-CoV-2 in wastewater samples. The government of Australia implemented a system where once a COVID‑19 outbreak is detected in a region’s sewage, people are to report to public health officials to be tested through nasal swab tests. The What is known about using wastewater surveillance to monitor the COVID‑19 pandemic in the community? rapid review reported that although wastewater-based surveillance is possible, no guidelines report the effectiveness of this method for ongoing surveillance or to inform decisions about lifting or imposing lockdown restrictions. Currently, no best-practises for wastewater surveillance have been identified.
Ottawa Public Health is one of the first public health units in North America to conduct daily wastewater readings from 91.6% of Ottawa’s population to detect and measure the presence of SARS-CoV-2 genetic material (ribonucleic acid or RNA). However, the municipality has noted that wastewater is a harsh environment which may breakdown the viral RNA and lead to lower readings of the virus. In its Phase 1 Inter-Laboratory Study: Comparison of Approaches to Quantify SARS-CoV-2 RNA in Wastewater report, the Canadian Water Network initiated the first phase of the Canadian COVID‑19 Wastewater Coalition’s proof of concept pilot to understand laboratory variability resulting from different lab techniques, to facilitate national and international data comparisons, and to inform Canadian public health. While a rapid review in May 2020 indicated that variations in methodology may contribute to inconsistency of findings and quality of evidence, although SARS-CoV-2 has been detected in untreated wastewater around the world, the review of results with different laboratories found that various approaches generally yielded comparable results with a critical caveat that sufficient quality assurance protocols must be in place and reported in adequate detail. The Canadian Water Network proposed the following recommendations to help characterize the variability of results expected using different methods deployed across Canada: 1) focus on how standard curves for quantification are generated; 2) address inhibition; 3) process controls; and 4) use faecal biomarkers to assist normalizing results.
The Sewage analysis as a tool for the COVID‑19 pandemic response and management: the urgent need for optimised protocols for SARS-CoV-2 detection and quantification suggested the need to develop a methodological protocol to detect and quantify COVID‑19 RNA in wastewater. Two single studies have displayed that SARS-CoV-2 genetic traces can be detected in different raw wastewater. The Quantitative analysis of SARS-CoV-2 RNA from wastewater solids in communities with low COVID‑19 incidence and prevalence study in Ottawa and Gatineau, Canada found that primary clarified sludge, compared to solids collected from post-grit sludge, showed a higher frequency of SARS-CoV-2 especially when COVID‑19 incidence is low in the community. The authors recommend using primary clarified sludge processing as an effective tool for monitoring trends during decreasing and low incidence of infection of SARS-CoV-2 in communities.
The Public Health Agency of Canada (PHAC) is providing laboratory analysis, result reporting and logistical support for the detection and monitoring of SARS-CoV-2 in wastewater from five high population centres (Vancouver, Edmonton, Toronto, Montreal, Halifax; representing 22% of the Canadian population). Results from the testing will be communicated back to the wastewater authorities who will share this with their local public health department. These data are being used to not only inform local public health, but also serve to help develop data structures and models that can be used across the country. Key collaborators include Statistics Canada (STC), Environment and Climate Change Canada (ECCC), and FPT public health counterparts.
To supplement recommendations for wastewater surveillance, the CDC reports guidelines for sampling strategies, testing methods, public health interpretation, and use of wastewater detection of COVID‑19 viral RNA.
The Department of Health and Human Services in Victoria, Australia released information on wastewater testing to provide early warning of COVID‑19 by showing if SARS-CoV-2 is present in the local community. The viral shedding may come from different sources such as used tissues, off hands and skin, or in stools. Find more information about wastewater testing here. The Canadian Water Network is bringing together Canadian experts to inform and guide SARS-CoV-2 wastewater surveillance. Find more information about this network here.
CanCOVID released a Speaker Series where Professor Frigon, from McGill University, discusses research on wastewater systems. He has been developing metagenomics tools for the surveillance of antimicrobial resistance in municipal wastewater. Watch the series here.