Testing community wastewater provides information about the health of a community.
There are many ways to get information on a person’s health when someone is unwell, a doctor may ask them to collect a sample of their poop (called a stool sample). Poop or stool can provide a lot of information as it can contain some infectious pathogens, medications or drugs.
Testing the community’s wastewater (water from toilets and sinks in households and businesses) for bacteria and viruses can provide a lot of information about the health of a community.
People with COVID-19 shed SARS-CoV-2 virus in their stool, whether they have symptoms or not. Samples of untreated community wastewater can be collected and tested for the COVID-19 virus in the BCCDC Public Health Laboratory using PCR testing. Multiple results collected over a period of time provide useful information about whether COVID-19 cases are increasing or decreasing in a community.
Because people with COVID-19 can shed SARS-CoV-2 even if they do not have symptoms, wastewater monitoring can provide an early warning if COVID-19 is increasing in a community. Other benefits of wastewater testing include:
- Provides information on the COVID-19 levels in communities where testing or access to healthcare is not readily available
- Is less invasive and cheaper than community-wide testing
- Provides unbiased and consistent population-level data on the COVID-19 incidence which can help inform the appropriate public health responses.
Photo: Michael Donoghue
Samples collected from wastewater treatment plants (WWTP) in urban regions across the province are sent to the BC Centre for Disease Control for testing.
Samples are collected two to three times per week. The BCCDC Public Health Laboratory tests the samples and shares SARS-CoV-2, influenza A, influenza B and Respiratory syncytial virus (RSV) levels on the respiratory surveillance wastewater surveillance dashboard.
Wastewater Dashboard
- Annacis Island WWTP (covering Fraser North and South)
- Iona Island WWTP (covering Vancouver)
- Lions Gate WWTP (covering North Shore)
- Lulu Island WWTP (covering Richmond)
- Northwest Langley WWTP
- McLoughlin Point WWTP (covering Victoria)
- Comox Valley Water Pollution Control Centre
- Regional District of Nanaimo WWTP
- Kamloops Sewage Treatment Center
- City of Kelowna WWTP
- City of Penticton WWTP
- City of Prince George WWTP
Testing of wastewater can provide information on how levels of SARS-CoV-2 virus are changing within an area over time. Since samples are collected from catchments that serve a large population, wastewater data cannot be used to identify which people in a community have COVID-19. Also, due to individual differences in viral shedding, wastewater monitoring cannot determine how many people have COVID-19 or whether people have symptoms or not.
Important considerations when analyzing data:
- Surveillance data is most useful and reliable when studied over a longer period of time (for example, consistent increases in SARS-CoV-2 levels over several weeks tell us more than a single day increase).
- The daily viral load changes day-to-day therefore changes in SARS-CoV-2 levels are best observed as trends over time (we call this percentage % change).
- Each catchment has unique contribution sources (i.e. residential, industrial, commercial), and therefore, trends within each catchment should be evaluated individually.
- Wastewater data should be integrated with other surveillance systems (i.e.
COVID-19 case and hospitalization data) to get an overall
COVID-19 situational analysis.
Photo: Michael Donoghue - Use wastewater to distinguish between different variants of SARS-CoV-2 including emerging and circulating variants of concern by sequencing.
- Research to develop ways to test wastewater for other viruses, bacteria and substances that are important to population health.
Photo: Michael Donoghue
