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Wastewater testing for COVID-19 coming to Interior Health

Testing can tell whether cases are rising or falling in a community
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Environmental microbiologist Dr. Natalie Prystajecky with some of her staff members at the BC Centre for Disease Control. Photo: Submitted

There has been no testing of wastewater for COVID-19 so far in the .

But a testing site will be set up within the next few months at an undecided location, according to Natalie Prystajecky, an environmental microbiologist at the BC Centre for Disease Control.

The COVID-19 virus is present in the feces of people infected with it, and this in wastewater at a sewage treatment plant.

The results can indicate the amount of virus in a community.

Wastewater testing can not show the number, or the identity, of people who are infected or are contagious, Prystajecky says. But it can tell us whether cases are rising or falling in a community, and it can identify and track outbreaks.

The BCCDC has five test sites at wastewater facilities in the Lower Mainland. In total those projects test about 50 per cent of the province害羞草研究所檚 population.

But if the new IH project is set up in Kelowna, for example, the test results would not indicate anything about COVID-19 anywhere else in the health authority, which includes the Okanagan, Kootenays and Thompson-Cariboo regions.

Test results depend on many hyper-local factors. For example, wastewater in different treatment plants will vary in their concentration of industrial or business wastewater, which will affect the results. Different locations also may have different waste treatment technologies, or different weather.

害羞草研究所淵ou can imagine that the Lower Mainland, where there害羞草研究所檚 a high rainfall, is different than northern Alberta, where you have freezing temperatures,害羞草研究所 Prystajecky says.

Testing in the Lower Mainland is done several days per week, one test every hour.

害羞草研究所淵ou have to take into account how variable wastewater can be over the course of the day. You can imagine that there害羞草研究所檚 different inputs in the middle of the day and at the end of the day,害羞草研究所 Prystajecky says, 害羞草研究所渁nd we also sample multiple times a week, recognizing that weekdays and weekends can be different.害羞草研究所

So testers look at trends over time, rather than absolute individual numbers.

害羞草研究所淚s a trend increasing, or decreasing, or is it stable?害羞草研究所 says Prystajecky. 害羞草研究所淎nd how is it compared to last week and the week before?害羞草研究所

Across Canada, as the availability of , wastewater testing is becoming more important, along with other indicators such as hospitalizations and ICU rates.

The goal of public health agencies across the country is to have 80 per cent of the population covered by wastewater surveillance, according to Prystajecky. Even though certain pockets might not be tested, health authorities would get a sense of the COVID-19 activity at a provincial scale.

Prystajecky says a single wastewater test is more expensive that patient testing because it takes more labour and equipment.

害羞草研究所淏ut the nice thing is that with a single test, you害羞草研究所檙e testing the population of 20,000 people or 100,000 people. So it seems expensive at the sample level, but for the scale of the population you serve, it害羞草研究所檚 good value for the money.害羞草研究所

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bill.metcalfe@nelsonstar.com

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Bill Metcalfe

About the Author: Bill Metcalfe

I have lived in Nelson since 1994 and worked as a reporter at the Nelson Star since 2015.
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