The GNWT wastewater monitoring program is a partnership between the Department of Health and Social Services (HSS), Taiga Environmental Lab, Municipal and Community Affairs (MACA) and NWT communities. Weekly wastewater samples are collected from participating communities to test for respiratory viruses, including COVID-19, Influenza (flu), and Respiratory syncytial virus (RSV). Communities can choose to join the program at their convenience.

How Wastewater Virus Monitoring Works

• People infected with viruses like COVID-19, flu, or RSV can shed pieces of the virus in their stool (poop), even if they feel fine.
• The virus pieces travel from the toilet into the sewage system.

• Wastewater samples are taken from the sewage system before treatment and sent to Taiga Lab in Yellowknife.

• The lab tests the samples to check for the presence and amount of different viruses.
• The Office of the Chief Public Health Officer (OCPHO) and public health partners use this data, along with other information, to understand disease trends in communities and make decisions to prevent the disease spread.

Benefits of Wastewater Virus Monitoring

• Helps identify if COVID-19, influenza A and B, and RSV are present in a community.

• Act as an early warning if the number of infections is increasing or decreasing.

• Help public health officials make informed decisions, such as guidance on preventing infections, testing, and vaccination options.

Limitations of Wastewater Virus Monitoring

• Cannot prove that infections are absent in a community. Sometimes there may be too little virus in wastewater for a test to detect it.  

• Does not estimate the number of infected individuals in a community. Wastewater provides trends but not specific numbers of people who are sick.

• Cannot reliably compare trends between communities due to various factors affecting sample strength, like groundwater changes (e.g. snow melt), temperature, collection method, and other substances (e.g. cleaners and disinfectants). 

Interpreting Wastewater Virus Data

• Virus detection: Each sample is tested to check for presence or absence of the virus. A detection means the virus was found in the sample.
• Virus concentration: The amount of virus in the sample, or viral load, helps indicate if infection levels increasing or decreasing. The report uses a 7-day rolling average to smooth out short-term fluctuations in the data. 
• Viral load levels: The average viral load during the report is compared to the previous year's data and classified as high, moderate, low, or not detected. Communities with insufficient data are noted. 

Use caution when interpreting daily and short-term changes in the viral loads as wastewater signals can change from day-to-day. More sustained increases or decreases in the viral loads are more reliable for seeing trends. 

Data Notes:

• Qualitative results (detect/no detect): Determined using the Cepheid GeneXpert system, a PCR test that detects virus genetic material in wastewater.
• Quantitative results (viral load): Calculated by converting GeneXpert cycle threshold (ct) values to viral load values using the Canadian National Microbiology Lab's methods.

Citations

1. Hizon N, Mejia E, Hannah E, Gregorchuck BSJ, Medina N, Becker MG, Mangat CS. GeneXpert Wastewater Surveillance. GitHub repository. https://github.com/Wastewater-Surveillance/GeneXpert_WW
2. Daigle J, Racher K, Hazenberg J, Yeoman A, Hannah H, Duong D, Mohammed U, Spreitzer D, Gregorchuk BSJ, Head BM, Meyers AFA, Sandstrom PA, Nichani A, Brooks JI, Mulvey MR, Mangat CS, Becker MG. A Sensitive and Rapid Wastewater Test for SARS-COV-2 and Its Use for the Early Detection of a Cluster of Cases in a Remote Community. Applied and Environmental Microbiology. 2022. March 8th. doi: https://doi.org/10.1128/aem.01740-21