Wastewater monitoring

On this page

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

About wastewater monitoring

When monitoring wastewater, the Public Health Agency of Canada (PHAC):

• collects community sewage samples
• tests samples to detect specific infectious diseases or other public health threats

This provides data on disease levels within communities over a specific time period.

Wastewater monitoring:

• can alert public health officials to diseases, like respiratory syncytial virus (RSV) and flu (seasonal influenza), that may be spreading in a community
• can detect pathogens in communities where laboratory testing capacity is limited
• can identify specific variants of a pathogen
• is a non-invasive approach to monitoring disease activity

Criteria for monitoring

Scientists continue to:

• learn how wastewater monitoring can be used to support other surveillance systems
• identify where wastewater monitoring may be an advantage

The criteria for using wastewater monitoring may include an evaluation of 1 or more of the following factors.

1. If there's a need for wastewater monitoring of a pathogen to fill gaps in existing surveillance systems.
2. If we can easily detect the pathogen in wastewater and determine its source (animal, human or environmental).
3. How the data can be used alongside other public health data to enhance monitoring of diseases in communities.

Scientists routinely monitor for:

• mpox
• respiratory viruses, such as COVID-19, flu and RSV

Learn more:

• National Wastewater Monitoring of Pathogens (NWMP) dashboard

Where we monitor

We collaborate with federal, provincial, territorial and municipal organizations to make decisions on:

• testing sites
• viral and bacterial targets for wastewater testing

Federal wastewater monitoring takes place in all provinces, as well as the Yukon and Northwest Territories.

Learn more:

• Canadian Wastewater Survey
• National Collaborating Centre for Infectious Diseases: National Wastewater Monitoring Program

How we monitor

Some infectious diseases are shed in human waste (urine, stool and other bodily fluids), and sometimes through skin. These can be detected in wastewater.

Infected people can shed viruses and bacteria into the wastewater collection system, even if they don't have symptoms. Infected animals can also shed viruses and bacteria, making it difficult to determine the source of signals for some infectious diseases. A signal refers to the concentration of genetic material from a pathogen (such as RSV) found in a sewage system.

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, especially where laboratory testing capacity is limited
• health care resource allocation, such as hospital beds and staffing needs

Information sources and collaborations

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

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

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

To identify meaningful trends in wastewater data, a minimum of 3 to 4 weeks of consistent sampling and testing is typically required.

During the COVID-19 pandemic, we also worked on pilot projects in collaboration with some Canadian airports to assess COVID-19 variants coming into Canada. This allowed us to compare wastewater data from airports against global and national data.

Data interpretation

Wastewater testing and data interpretation can be impacted by various factors, including:

• pathogens, or other substances in wastewater, that may degrade before the testing is done
• the composition of wastewater and wastewater collection systems, which can vary by community
• the presence of signals from animal or environmental sources, which can impact interpretations
• weather-related factors, such as heavy rains, flooding and snow melt, which may dilute the signals in wastewater

Wastewater monitoring also presents challenges. For instance, it cannot:

• identify individuals, only the presence of a disease in a community or site
• tell if a positive wastewater signal is from a community resident or a traveller

What we're doing

Wastewater monitoring is an evolving and complex science. It works most effectively with other surveillance systems (such as clinical testing) to:

• provide situational awareness
• obtain a complete view of trends

PHAC scientists continue to:

• improve methods for analyzing and interpreting wastewater data
• work with partners to refine laboratory testing methods and data interpretation approaches for tracking the presence of infectious diseases in wastewater

Wastewater can also be used to monitor other public health threats, such as:

• chemicals and pharmaceuticals, including illicit drugs
• antimicrobial resistance
• other communicable diseases, such as norovirus, poliovirus and measles

Contact us

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