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鈥檚 population.

But if the new IH project is set up in 琉璃神社, 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.

鈥淵ou can imagine that the Lower Mainland, where there鈥檚 a high rainfall, is different than northern Alberta, where you have freezing temperatures,鈥� Prystajecky says.

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

鈥淵ou have to take into account how variable wastewater can be over the course of the day. You can imagine that there鈥檚 different inputs in the middle of the day and at the end of the day,鈥� Prystajecky says, 鈥渁nd we also sample multiple times a week, recognizing that weekdays and weekends can be different.鈥�

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

鈥淚s a trend increasing, or decreasing, or is it stable?鈥� says Prystajecky. 鈥淎nd how is it compared to last week and the week before?鈥�

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.

鈥淏ut the nice thing is that with a single test, you鈥檙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鈥檚 good value for the money.鈥�

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bill.metcalfe@nelsonstar.com
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