Scientists studying the concentration of COVID-19 in Ottawa's wastewater say they've been seeing rising levels of the virus over the month of December, but the concentration is still below the highest levels seen in October.
The CHEO Research Institute and the University of Ottawa have been monitoring the wastewater for several months, as another way to measure how much of the virus may be circulating in the city.
"People with COVID-19 shed the causative SARS-CoV-2 virus in their stool, regardless of whether they have symptoms, receive a COVID-19 test or ever are diagnosed," a statement on the wastewater tracking page says. "Thus, in contrast to assessing community COVID-19 levels by measuring the number of active cases, which may miss asymptomatic infections as well as be subject to limited test availability, wastewater surveillance consistently captures most of the population with COVID-19 given that everyone goes to the washroom."
Speaking on CTV Morning Live, uOttawa Associate Professor Robert Delatolla said wastewater levels tend to rise a bit earlier than case numbers do.
"There is a little bit of a warning there that, as these numbers increase, we should try to curb our activities and mitigate this trend that we're seeing right now," he said.
The wastewater tracking showed a significant spike in the viral signal in mid-October. At the time, Ottawa was seeing the highest per capita rate of COVID-19 in Ontario. The latest data on the tracking webpage shows a slight decline at the very end of December amid a constant increase through the month.
Ottawa's rate of new COVID-19 cases per 100,000 residents in the past seven days has increased by 50 per cent since the end of 2020, but is still well below areas like Toronto, Peel Region and Windsor-Essex.
The viral signal detected in Ottawa's wastewater was lower in December than it was in October, and while daily case numbers are trending higher in the city, including a record 184 new cases reported by Ottawa Public Health on Sunday, Delatolla says the wastewater measurements don't always align with cases for a number of reasons.
"People might become sick, but when they become sick early on, maybe they don't feel so bad, maybe they don't get tested right away," he said. "There's also a large portion of the population who might be asymptomatic and people might start to fecally shed when they're presymptomatic. We sort of see, in the wastewater trend, a little bit of an early indication of what we're going to see in case numbers and in the per cent positivity a few days later."
Researchers hoping to track new COVID-19 variant
Delatolla said researchers believe they should be able to track any new COVID-19 variants through the wastewater, but they are still working on it.
"It's something that we're working on with our colleagues all across the country in order to find a way to follow that variant within the wastewater," he said. "We've sent our samples to various labs to different sort of testing, to do sequencing to measure the entire genome, to look at not only the UK variant but any kind of variant that may come our way."
In late December, the Ontario government confirmed that one person in Ottawa, who had recently travelled to the United Kingdom, tested positive for the UK variant.
Delatolla says he hopes that, as more people obtain COVID-19 vaccines, the concentration of the virus in the city's wastewater should also decrease.