Toronto's wastewater shows an uptick in COVID-19 across the city

Toronto’s wastewater surveillance program to track COVID-19 in the city is showing signs that infection rates are creeping back up.

Shortly after Ontario stopped providing publicly funded PCR COVID-19 testing to most of the population, Toronto began releasing wastewater surveillance data to the public.

“Wastewater surveillance does not replace traditional COVID-19 testing, but can provide a broader understanding of COVID-19 activity,” Toronto Public Health said in a statement at the time.

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Released every Wednesday afternoon, Toronto’s wastewater surveillance shows that COVID-19 is no longer dropping in the city, and is now on the rise.

Wastewater surveillance March 22/Toronto Public Health

For wastewater, red indicates an increase of more than 10% change per 100,000. Yellow indicates either a change of less than +/-10%, or a statistically insignificant change, and green means a decrease of 10% change per 100,000.

While wastewater signals showed a significant decrease when public health measures remained in place, they are now rising again. A look at the archived wastewater data shows that while this week’s surveillance may not be showing large increases over the previous week, they are certainly no longer in decline.

Wastewater surveillance has not shown a decline in any of the monitored wastewater treatment plants since March 1, when Ashbridges Bay showed a decrease over the previous week.

Wastewater surveillance/Toronto Public Health

The trends show that COVID-19 detection in Toronto wastewater is rising across the board. Earlier this month, Ontario’s chief medical officer of health told reporters that actual COVID-19 case rates are about 10 times higher than reported. This would indicate that on Wednesday, Toronto likely had more than 6,000 positive COVID-19 infections.

1/2: #COVID19 update: As of Mar 23, 8:30 a.m. there have been 295,730 cases (641 new), 70 are in hospital (6 new), 4,129 deaths (6 new) & 288,394 recoveries (461 new): https://t.co/CkCG04C1q3 pic.twitter.com/wOPBZFpUdB

— Toronto Public Health (@TOPublicHealth) March 23, 2022

Last week, Ontario’s COVID-19 Science Advisory Table released modelling that showed an increase in COVID-19 in wastewater across the province.

There is no clear indication of how prevalent COVID-19 is in Ontario. Since the province restricted testing and removed most public health measures, the virus has free rein to spread.