An upward trend in the amount of COVID-19 virus in Calgary wastewater should caution people to more closely monitor the level of risk they’re taking when going out, experts say.
The provincewide wastewater project conducted by researchers at the University of Calgary and University of Alberta has noted an increase of SARS-CoV-2 virus in the wastewater in Calgary, Banff, Medicine Hat and Fort Saskatchewan after several weeks of decline. The wastewater data has been used as an early indicator for a spike in COVID-19 cases in Alberta communities for much of the pandemic.
In the Calgary area, the level of virus in wastewater began declining in mid-January but plateaued at the beginning of March.
“It’s been at that level, hovering around that level, and now we’ve seen a couple of points in the last week that have been going back up,” Dr. Maria A. Bautista, a member of the University of Calgary research team , said over the phone Wednesday.
“Right now we are sitting much higher than at the lowest point before Omicron. So, we haven’t gone back to the pre-Omicron levels and it seems we’re stalling and starting to go up. There is virus circulating in the community and it might be going up.”
Bautista said she encourages people to use the wastewater data to monitor their risk level.
“It’s a chance for 80 per cent of Alberta to look at their community and see how it’s doing and then make evidence-based choices,” she said. “You choose where you go, what you do, but you have the ability to look at the data and say, ‘Yes, I’m going to do this,’ or ‘I don’t feel comfortable doing this.’ ”
Another 1,900 cases of COVID-19 were confirmed from 8,317 PCR tests completed between March 18 and 21.
Dr. Deena Hinshaw, Alberta’s chief medical officer of health, said during a briefing Wednesday it’s difficult to say what percentage of cases the PCR tests are capturing. She announced the BA.2 variant — a subvariant of Omicron — has become the dominant strain among positive tests.
“The leading metric that is most useful at this time is our positivity rate, and between Friday and Monday this ranged from 20.6 per cent to 27.1 per cent,” said Hinshaw.
“We should expect to see transmission trending upward in the coming weeks, meaning those at risk of severe outcomes should revisit their precautionary measures and those who have not gotten their booster dose should do so as soon as possible.”
As of Wednesday, 4,044 Albertans have died due to COVID-19, an increase of 21 deaths since the last update a week ago.
“This is a reminder of the fact this infection is still a significant threat to many of us, our families and our friends,” said Hinshaw.
“It’s important to take this seriously as we move into activities we haven’t done for a while and consider how best to support those around us to mitigate the risks.”
There are 956 COVID-19 patients in hospital, including 56 requiring intensive care. Health Minister Jason Copping said the health system continues to recover from the fifth wave.
“There is no question that COVID is still with us, but as time passes we continue to see the impact is less than it has been in the past,” Copping said.
Sarah Otto, a professor of evolutionary virology and mathematical modeling at the University of British Columbia, said in an emailed statement there are early signs of a second Omicron wave in Alberta.
“We expect a second Omicron wave given the rise in frequency of the more transmissible BA.2 sublineage (roughly at 50 per cent frequency now in Canada), the waning of immunity from boosters (especially among the most vulnerable who were vaccinated more than four months ago), and the relaxation of public health measures,” Otto said.
Caroline Colijn, a COVID-19 modeller and mathematician at Simon Fraser University, said there’s more uncertainty because of the limited PCR testing in Alberta and other provinces that are now relying on people’s use of at-home rapid tests.
“When we remove masking and other measures and a lot of people are going back to a higher level of socializing than they were before, that does cause a bit of a surge, but we’re not seeing a huge surge or another huge Omicron wave ,” Colijn said over the phone.
Continuing to take certain precautions and monitoring the risk of transmission is still necessary as public health measures are removed, Colijn said.
“There are lots and lots of good things that are good for us that we don’t mandate as a rule; we don’t have to exercise every day, we don’t have to eat our vegetables,” she said.
“I think we do need to protect others and not just ourselves. And that’s a good rationale for keeping up with ventilation, socializing outside or wearing masks when feasible, even if it’s not mandated.”
Dr. Chuck Wurster, an Edmonton emergency physician, said on Twitter he saw a lot of COVID-19 patients Tuesday evening.
“COVID is not gone. Everyone who works in the hospitals knows it,” he said. “We can’t pretend that COVID is gone. We can’t make it look like it’s gone by not testing.”
He encourages people to wear good masks, limit indoor gatherings, open windows and get the booster dose they’re eligible for to protect themselves and their community.