More transmissible subvariant on course to displace original Omicron strain in Alberta

A more transmissible Omicron subvariant, known as BA.2, is eating up a larger proportion of the province's COVID-19 cases, and experts are worried this could jeopardize Alberta's downward trend in case counts and hospitalizations.

In a weekly update sent to community physicians last Friday, Alberta Health Services said BA.2 accounted for an average of 23 per cent of positive cases tested for variant strains between Feb. 25 and March 2.

That's up from the week before when the Omicron subvariant accounted for an average of 10 per cent of daily lab confirmed cases.

"If the trend continues, we should see BA. 2, this week, becoming the most common variant in Alberta," said Sarah Otto, a University of British Columbia professor and member of an independent COVID-19 modelling group.

Otto said, based on these numbers, BA.2 appears to be doubling in Alberta every week, and because it spreads more easily than the original Omicron strain (BA.1), the vulnerable are at risk.

"It will find those communities — find those pockets — where there aren't that many people immunized, either through boosters or through having had a recent Omicron infection."

A key problem for Alberta, according to Otto, is timing.

"We see BA.2 rising in frequency. We know it's more transmissible. At the same time, we're seeing restrictions ease up. This isn't a great recipe. It certainly makes me concerned about … whether we're going to see a surge because we've got this double whammy happening at the same time."

With virtually all public health measures eliminated in Alberta, Otto said it's difficult to predict what will happen. If enough Albertans choose to continue with measures such as masking on their own, that could mitigate spread, she said.

Hospitals still 'full'

Dr. Daniel Gregson, an infectious disease and medical microbiology specialist with the University of Calgary, is watching the numbers closely.

"The concern is that with a more transmissible variant and removing restrictions, there will be either a plateauing of our hospitalizations or an uptick in the hospitalizations," he said.

"It varies from hospital to hospital, but many of the hospitals are actually full."

He had hoped the provincial government would ease restrictions in a more cautious manner — waiting until acute care capacity was more manageable.

"That's obviously not going to happen. I think that the government says they're following the wastewater levels and will respond if those change. We'll see if that occurs. We're sort of stuck in this situation where they've made decisions and we'll have to see what happens."

Gregson does not expect a repeat of the fall, when hospitals were so overwhelmed, doctors were warning the health system was on the brink of collapse.

But, he said, the subvariant could still pose problems.

"I am concerned that our hospitals could continue to be full of patients with COVID, [and] it really disrupts our ability to care for the standard patients that come in on a regular basis. So it's a concern for overwork. It's a concern for our inability to provide usual care for patients. It's a concern for the cost associated with taking care of these patients in hospital as well."

Gregson said the growth of the subvariant underscores the need for people to get vaccinated and get their third dose if they haven't already.

In its update to physicians, Alberta Health Services noted the Omicron sublineage is on track to take over in Alberta.

"It appears the BA.2 is trending to higher proportions as has been seen in other countries where Omicron BA.2 is now the predominant strain," the letter stated.

Meanwhile, in a statement emailed to CBC News, Alberta Health said it continues to screen all lab-confirmed COVID-19 cases for variants of concern, including BA.2. This process resumed in February after it was halted over Christmas due to surging case numbers.

"At this time, fewer than 25 per cent of positive cases are BA.2. It is not the dominant strain of Omicron in the province. That being said, there is no evidence of higher severity than BA.1 or any other clinical differences, and initial analyses from the WHO (World Health Organization) indicates no increase in hospitalizations compared to BA.1," spokepserson Lisa Glover said in the email.

These numbers are based on PCR tests, which many Albertans have been unable to access since the province restricted testing to high-priority groups.

Glover said Alberta Health could not provide a prediction on when the subvariant would become the dominant strain.

"But [Alberta Health] continues to monitor the spread of COVID-19 in the province through wastewater surveillance, hospitalization data and PCR testing data for eligible Albertans."