Wastewater monitoring is used by scientists and public health officials to track the spread of diseases in communities. Since the 1960s, wastewater has been used to monitor for diseases such as polio through the analysis of human waste.

Fragments of the COVID‑19 virus are shed in the feces of an infected person a few days before, and up to three weeks after a person begins to feel ill. These fragments are not infectious, but are flushed into the sewer system and mix with all other wastewater in the community.

Here’s how wastewater monitoring works:

  1. Wastewater samples are taken from a community location like a wastewater treatment plant or a high-risk facility like a retirement home.
  2. The wastewater samples are sent to labs and analyzed for the presence and spread of a disease by measuring specific targets such as concentration of virus fragments over time.
  3. The data is used by public health professionals to help them make decisions.

Monitoring wastewater gives a close to real-time way to track the spread of viruses, such as the COVID‑19 virus and other public health threats, including influenza, before people begin showing symptoms.

About the Wastewater Surveillance Initiative

In 2020, we established the Wastewater Surveillance Initiative to detect COVID‑19 in wastewater samples across Ontario.

Over the past few years, wastewater sampling and analysis has emerged as a unique, cost-effective tool that:

  • can monitor public health concerns whether or not people in a community seek health or hospital care
  • delivers data to public health decision makers so they can determine the appropriate response

The initiative uses wastewater sampling, clinical cases, and other public health data to:

  • help local public health units identify potential disease outbreaks, such as COVID‑19 in their communities
  • enable more timely decisions about how and where to mobilize resources in response

Academic and research partners

We built on the work that was already underway in several communities in Ontario and partnered with academic and research institutions to create a provincial network that would ensure more public health units have access to wastewater data. The academic and research institution partners include:

  • Carleton University
  • University of Guelph
  • Health Sciences North Research Institute
  • McMaster University
  • Ontario Tech University
  • University of Ottawa
  • Queen’s University
  • Ryerson University
  • University of Toronto
  • Trent University
  • University of Waterloo
  • University of Western Ontario
  • University of Windsor

The Ontario Clean Water Agency (OCWA) is also providing technical expertise and equipment for testing in sampling locations. The National Microbiology Lab, with the Public Health Agency of Canada, is providing scientific advice and lab analysis support.

Wastewater sampling locations

In April 2023, we introduced a strategic sampling plan to focus resources on community sites that:

  • provide reliable results
  • are representative of unique populations and geographical areas across Ontario

Wastewater sampling currently takes place at municipal wastewater treatment plants across the province in every public health unit. Locations were selected based on data analysis, and consultation with academic and research institutions and local public health units.

Research is also continuing at some:

  • First Nation communities
  • long-term care facilities
  • correctional facilities
  • hospitals
  • homeless shelters
  • retirement homes

The initial locations were chosen by participating municipalities, academic and research institutions and local public health units in consultation with the former Ontario Science Advisory Table members.

Additional locations were added in consultation with participating municipalities, academic and research institutions and local public health units.

Sampling and lab analysis guidance

Academic and research institutions are analyzing wastewater samples and producing reliable results for local public health units.

We developed a protocol document for analyzing wastewater samples. The protocol provides technical guidance to university and government lab scientists and commercial labs to help ensure quality assurance and control of sampling and analysis results.

Next steps

Ontario continues to use every tool available to protect Ontarians by monitoring trends and detecting virus outbreaks as early as possible. Wastewater surveillance can help keep Ontario open by monitoring trends in wastewater, as well as the detection and spread of viruses as they mutate over time.

Data from the initiative will also continue to be an important tool to inform the province’s understanding and response to virus outbreaks and could inform our response to future public health threats.