Calgarians can now track traces of COVID-19 in their wastewater

What’s in a flush? Calgarians can now find out online via the Centre for Health Informatics (CHI) COVID-19 Data Tracker, where real-time data shows levels of SARS-CoV-2 in Calgary’s wastewater. This data can help identify outbreaks early, and pinpoint areas of the city where infection rates are high.

This data sharing is made possible by the work of a team from the Cumming School of Medicine (CSM), Faculty of Science, and Schulich School of Engineering, Advancing Canadian Wastewater Assets (ACWA), The City of Calgary, and Alberta Health Services (AHS).

“Wastewater data is unbiased and comprehensive,” explains Dr. Michael Parkins, MD, associate professor at the CSM and section chief for the Division of Infectious Diseases for AHS. “It captures all cases in a defined population, including symptomatic and asymptomatic cases — not just those diagnosed cases.”

The data shows that high levels of traces of SARS-CoV-2 in wastewater are followed by a rise in clinically diagnosed cases. “These findings suggest that this technology can be used as an early warning system,” says Parkins. Alberta Heath Services is looking at the data as an additional tool to understand how COVID-19 is spreading in the community.

“The City has long supported wastewater research to strengthen efforts to protect public health and the environment,” says City of Calgary Water Services director Nancy Stalker. “The City is pleased to support these collaborative efforts in the fight against COVID-19.”

Calgarians can visit chi-csm.ca and see a map of Calgary, divided up into three areas, based on the collection zone for each City of Calgary wastewater treatment plant.

“Each data point represents a 24-hour period, where a 100 ml sample is taken every 15 minutes to generate a 10-litre sample,” says Parkins. “We then test to look for evidence of the SARS-CoV-2 RNA genetic material.” The tracker shows data starting in July 2020, when the group started gathering samples.

Danielle Southern, senior researcher at CHI, says that the wastewater data adds to the overall story that the tracker is telling. “What we like is that we can look at the number of cases and their trajectory, and then compare it to the trajectory of the wastewater data over time, and see how it lines up,” Southern says. The wastewater visualization was created by CHI data scientist Alexander Krusina.

The tracker has expanded over the past 11 months based on questions the CHI has received from policy-makers and government officials. “Originally it was, ‘what measures should we put in place?’, and now it’s shifted to, ‘what can we re-open safely?’”, she says. Understanding where transmission is happening is key to those decisions. A recent addition to the tracker breaks down the proportions of different sources of case transmission. For the last few weeks, around 35 per cent of sources are unknown.

Southern anticipates that future wastewater data will be of value to help answer the question of what can be re-opened safely, when so many sources are unknown. “Policy-makers might be interested to use wastewater tracking in specific locations, where you might be able to pick up on the outbreaks earlier and limit the spread,” she says. “The wastewater could give us some predictive tools. Say you’re seeing it in a high school, that means it’s probably out in your community, whereas if it’s in a hospital, those people are likely constrained to that one place.”

When can Calgarians expect this type of granular information? “Hopefully in several weeks we can introduce more data to the tracker from specific areas within Calgary,” says Parkins. “Due to the complexity of sample collection and processing, at this time we can’t assess each neighbourhood in the city, but instead are currently assessing a mixture of communities.”

Location-specific sampling is in the works as well, and the research team is looking forward to sharing results from those projects when they’re ready. “Wastewater testing has tremendous potential to help keep our communities safe, and catch outbreaks before they reach critical mass,” says Parkins. “The further we can take this research, the better.”