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Banff, Canmore: a tale of two COVID trends in wastewater testing

“I’m not saying there isn’t COVID in Banff, but another relevant question is are people from Calgary going to the bathroom in Banff? If I were in Banff, I would still be careful.”

BOW VALLEY – For the first two years of the COVID-19 pandemic, testing was mostly conducted at hospitals and specific testing locations.

This allowed the provincial government to report infection numbers in daily briefings to the public.

As more Alberta residents move toward home testing, a new method is becoming popular to monitor provincial trends: wastewater testing.

This method differs from standard PCR testing. Instead of a sample being obtained from the throat or nose of an individual, it comes from a jar of wastewater.

“A sample of wastewater goes back to the lab, we mix it up, take a sample and extract the RNA,” said Casey Hubert, associate professor of Biological Sciences at the University of Calgary. “Fragments of the RNA are hanging around in the water. Then we do a PCR test on it. We really rely on a feature of the test that allows us to quantify the level.”

The main goal of the wastewater testing, and the graphs that are made available to the public online, is to see whether numbers are rising, falling, or holding steady.

“The way we interpret the data, you should only compare one location with itself,” Hubert said. “You can look at the trend line. Is it a steep rise, steep drop, or holding steady? Let’s not get too worried about the units on the Y-axis. Look at the line going up and down.”

In November and December, Banff saw a faster rise in infections than anywhere else in the province, while Canmore saw a slower rise. That trend is now reversed with Banff showing a slower rise than Canmore.

In December, Banff saw 1,800 copies of COVID-19 RNA per millilitre of wastewater. As of last week, that number was only 165 copies per millilitre of wastewater.

In Canmore, the community saw a high of 1,863 copies per millilitre of wastewater on Jan. 6. After hitting a high of 1,515 copies per millilitre of wastewater on April 12, the community currently sits at 669 copies per millilitre of wastewater.

“The wastewater in Canmore shows more evidence of a BA.2 variant resurgence,” said Hubert. “It is interesting in Banff that the numbers did not jump up again as they have in other places.”

While the use of wastewater testing is highly accurate, it presents problems in translating the figures to the public. The main reason it is harder to communicate wastewater results is that individuals are not being counted.

“We can say it is more than yesterday, and tomorrow is more than today, but we don’t have a number of people statistic that we can convert our data into,” Hubert said. “If the public can engage with this trend of what the sewage is showing, they can use that as a weather forecast. The weekend is coming up, should we invite people over, or should we go for a walk?”

Another issue for the Bow Valley is the number of people travelling through, and how many are stopping to go to the bathroom along their journey into, or from the Rocky Mountains.

“It boils down to how the virus gets from an infected person to the sampling point, which is the wastewater treatment plant,” Hubert said. “Where someone goes is actually an important determinant in how these signals play out in different places. It is connected to pooping effectively.”

As for whether the Bow Valley and the province is going through a sixth wave, Hubert states the data speaks for itself.

“In Calgary and Edmonton, it is pretty obvious. If you ask me about Alberta, it is clear,” Hubert said. “It is interesting that Banff is staying low, which is fascinating compared to what it did in December. Canmore seems to show more evidence of a sixth wave. Banff isn’t zero, but it is not screaming hot.”

Hubert also cautions not to see the low numbers in Banff as evidence of no COVID-19 risk in the community.

“I’m not saying there isn’t COVID in Banff, but another relevant question is are people from Calgary going to the bathroom in Banff? If I were in Banff, I would still be careful.”

To see the wastewater testing trends, visit https://covid-tracker.chi-csm.ca.