Wastewater monitoring

On this page

• About wastewater monitoring
• What we monitor for
• Where we monitor
• How we monitor
• What we're doing

About wastewater monitoring

When monitoring wastewater, we collect community or institutional sewage samples and test them to detect specific diseases or other public health threats. This provides community health data about the levels of disease over time. It's especially useful in situations where laboratory testing capacity is limited. This method only captures the presence of the disease or other public health threat in the community or institution. It can't be used to identify individuals or households.

Wastewater monitoring is a rapidly evolving tool for public health surveillance. It alerts public health officials to diseases like COVID-19 and mpox (monkeypox) that may be spreading in a community. It's a non-invasive, cost-effective approach to monitoring disease activity.

For some diseases, like COVID-19, individuals can also monitor wastewater trend data in their own communities. This data can help people make decisions about public health measures, such as masking.

What we monitor for

Diseases are selected for monitoring based on:

• how likely they are to pose a public health risk in Canada
• how active they are internationally

Scientists routinely monitor for:

• polio
• mpox
• COVID-19
• flu (influenza)
• respiratory syncytial virus (RSV)

Where we monitor

Communities

Site and bacteria or virus selection for wastewater testing is decided by provinces, territories and municipalities.

Wastewater monitoring takes place in all provinces and territories. Most major Canadian cities have a COVID-19 wastewater monitoring program. As well, some northern, remote, and isolated communities have community-led monitoring programs.

Learn more about:

• COVID-19 wastewater surveillance dashboard
• Science of Health blog: Community-led wastewater testing in northern, remote and isolated communities
• Map of current wastewater surveillance sites in Canada (PDF, National Collaborating Centre for Infectious Diseases)

Airports

We have a wastewater testing pilot project at Toronto Pearson International Airport to assess COVID-19 variants coming into Canada.

Samples are analyzed for emerging or important variants of concern. Results generally take 2 or 3 weeks, but this can vary depending on:

• sampling site
• travel time to the laboratory
• the complexity of the analysis

We compare wastewater data from airports to global and national data.

How we monitor

Some infectious diseases are shed in human waste (urine and stool) and can be detected in wastewater. Infected people can shed viruses and bacteria into the wastewater collection system, even if they don't have symptoms.

We work with municipalities to collect and ship wastewater samples to laboratories for analysis. Knowing the daily or weekly changes in the amount of infectious disease detected in wastewater can help manage:

• outbreaks through public health action, such as vaccination and testing
• health care resource allocation, such as hospital beds and staffing needs

Learn more about:

• Science of Health blog: Harnessing the power of wastewater testing to detect COVID-19 outbreaks

Information sources and collaborations

We get wastewater data from multiple sources and compare it to international data. This data supports evidence-based decision making as we monitor the levels and impacts of certain infectious diseases.

Approximately 3 to 4 weeks of COVID-19 wastewater data are needed for meaningful trend results.

To compile wastewater data, we collaborate with experts across Canada, including:

• academia
• Indigenous governments
• other federal departments
• provincial, territorial and municipal governments

Data interpretation

Where laboratory testing capacity is limited, wastewater data helps us make decisions to reduce the impact of outbreaks.

The number of infections in a community can't be directly estimated from wastewater testing data. However, wastewater signals do closely follow trends in the number of diagnosed infections in a community.

What we're doing

Wastewater monitoring is an evolving science. Scientists are still learning new things about how to detect and measure infectious diseases in wastewater. The scientific community is working to build a standard method to help scientists understand, compare and share data about detecting infectious diseases in wastewater.

The Public Health Agency of Canada is working to establish a pan-Canadian wastewater surveillance network to monitor the spread of COVID-19 in Canada. To do this, we're collaborating with other federal departments, provincial, territorial and municipal governments, and academia.

In addition to COVID-19, wastewater surveillance can be used to monitor other public health threats, such as:

• chemicals and pharmaceuticals, including illicit drugs
• antimicrobial resistance
• other communicable diseases, such as tuberculosis and polio

Canadian Wastewater Survey

Statistics Canada and the Public Health Agency of Canada have been collaborating since September 2020 on the Canadian Waster Survey. So far, they analyze COVID-19, RSV, and flu from samples collected from wastewater treatment plants in 5 cities:

1. Halifax
2. Toronto
3. Montréal
4. Edmonton
5. Vancouver

Learn more about:

• Wastewater trend analysis report: SARS-CoV-2 detection by N1 and N2 RT-qPCR (PDF, National Collaborating Centre for Infectious Diseases)
• Wastewater sequencing trend report: Detection of SARS-CoV-2 variants of concern by metagenomic sequencing (PDF, National Collaborating Centre for Infectious Diseases)
• Wastewater modelling report for SARS-CoV-2 (PDF, National Collaborating Centre for Infectious Diseases)
• Canadian Wastewater Survey
• Detailed information for the Canadian Wastewater Survey

Wastewater working groups

The Public Health Agency of Canada leads working groups and meetings related to wastewater surveillance for COVID-19. There are currently 6 working groups:

1. SARS-CoV-2 Variants of Concern in Wastewater Working Group
2. Wastewater Laboratory Detection of SARS-CoV-2 Working Group
3. Wastewater SARS-CoV-2 Surveillance Updates Working Group
4. Data Modelling and Epidemiological Interpretation Working Group
5. Wastewater-based Epidemiology: Antimicrobial Resistance Network
6. Wastewater-based Epidemiology: Respiratory Viruses Network

For any inquiries, please contact nmlwastewater@phac-aspc.gc.ca.

Learn more about:

• Public Health Agency of Canada's Wastewater Surveillance Program for COVID-19