Wastewater and other disease indicators for COVID-19 are beginning to increase in parts of Canada, infectious disease physicians say, as students and teachers return to school and people begin to congregate indoors more often.
It’s an end-of-summer trend that’s been consistent for the past few years, with doctors recommending Canadians consider precautions like vaccination, hand hygiene and staying home when sick.
Nationally, the wastewater viral activity level for COVID stands at moderate, with levels high in Vancouver, Calgary and Edmonton, Winnipeg and Montreal South, the federal government’s wastewater monitoring dashboard showed Friday.
“It’s all kind of going in the same direction, suggesting that we might end up with kind of that late-summer increase followed by fall/winter surge, although of course it remains unpredictable,” said Dr. Lynora Saxinger, an infectious diseases physician with the University of Alberta.
Nationally, the percentage of positive tests for the virus that causes COVID among people going to emergency departments for respiratory symptoms stands at 8.5 per cent. For the week ending March 22, the test positivity fell to its lowest level this year, at nearly two per cent.
While the extent of the increases in late August has varied from year to year, the upward trend as summer comes to a close is a common one.
For comparison, positivity hit 16.9 per cent at the end of August in 2024 and 13.4 per cent for the same week in 2023.
Current variants
As with influenza, COVID protection from past infection or immunization wanes over time. The virus that causes COVID changes over time and new variants emerge.
Saxinger says the variants currently circulating all riff off Omicron, which has dominated since late 2021.
Similar to what was seen last year, the current Omicron subvariant, XFG, causes mild to moderate illness, according to Lawrence Goodridge, a microbiology professor at the University of Guelph.
“The current vaccines that are in production and will be available in the fall, should provide protection” against XFG, said Goodridge, who conducts wastewater surveillance for COVID, influenza, RSV, avian influenza and measles.
By testing blood samples from vaccinated and previously infected individuals, scientists are able to predict how well COVID vaccines work against circulating variants.
Lessons learned
Classically, fall is a time when people get together indoors and the air may be drier, says Saxinger. She suggested people take this time of year as a reminder of “lessons learned.”
“They should stay home from work and school if they’re sick,” Saxinger said.
COVID infection still has the potential to be widespread and cause “a lot of potential harm,” she added, especially for people who haven’t been vaccinated in a long time and have risk factors like being over 65 or other medical conditions.
Saxinger said such people at high risk for severe complications from COVID should know antiviral medications remain an option to avoid needing treatment in hospital.
Even though some people are at a higher risk of hospitalization and death from COVID infection, infectious disease experts aren’t expecting pandemic level surges in cases.
Vulnerable groups include people over 65, particularly over 80, people living in long-term care homes and those with certain underlying medical conditions, said Dr. Isaac Bogoch, an infectious diseases specialist based at Toronto General Hospital.
“There are categories of people who ‘should’ get the vaccine and then everyone else is really in the ‘may get’ the vaccine,” Bogoch said, pointing to recommendations that stand from Canada’s National Advisory Committee on Immunization.
COVID vaccines are not yet available and are expected to start rolling out across Canada in the fall.
“The key thing here is if anyone has any questions, they really should be speaking with the healthcare provider,” Bogoch said.
