Meet the sewage sleuths tracking Toronto’s COVID levels

The samples are key to tracking the rise and fall of infection rates, which are no longer accurately recorded by individual testing.

Alexandra Johnston and Eric Anderson take a short walk through crisp snow from the car park to the manhole cover a stone’s throw from the Humber River in Toronto’s northwest.

The pair of recent postgraduates show up here several times a week, part of a more than 100-kilometre round trip to six community sites where they collect wastewater samples to test for COVID-19 levels.

Those samples — and others collected at major treatment facilities in the east and west ends of Toronto and several downtown sites — are key to tracking the rise and fall of infection rates, which are no longer accurately recorded by individual testing.

“There’s always a lovely aroma with wastewater,” Johnston said as she lifts the cover of the sampler box Toronto Water installed next to the manhole and pulls out one of the bottles it had partially filled over a recent 24-hour period.

Winter’s frozen temperatures can make it more difficult to get enough samples for a composite, says the 26-year-old, who has worked with her alma mater X University (formerly Ryerson University, currently in the midst of a name change) on the project for almost a year.

On this visit, the site could only offer a one-off “grab sample” for the pair to send back to the laboratory for processing.

The university (along with the University of Toronto) teamed up with the province, the city’s Toronto Public Health and Toronto Water, and Unity Health’s St. Michael’s Hospital in the surveillance initiative, which has taken on more relevance since Ontario tightened testing requirements at the end of 2021.

The site just north of Highway 401 collects wastewater from 100,000 residents living upstream from it.