Omicron subvariant BA.2 being watched 'very closely' in Canada: Tam

Canada's top doctor says the Public Health Agency of Canada (PHAC) has detected more than 100 cases of a new Omicron subvariant known as BA.2, doubling the number of infections from the virus lineage that were reported earlier this week.

Dr. Theresa Tam said during Friday's federal COVID-19 update that the BA.2 subvariant was first detected in Canada in November 2021, and has since been "closely" monitored by experts.

"We're one of the first countries to actually pick up on this variant, and we have at least over 100 identifications," Tam said.

In an emailed statement to CTVNews.ca, PHAC previously said it had detected 51 cases of the BA.2 subvariant as of Wednesday. The agency added that the majority of infections have been from international travellers.

BA.2 is a descendant of the highly transmissible Omicron variant and has been found in nearly 50 countries as of Friday, according to global coronavirus data sharing platform GISAID.

While the World Health Organization (WHO) has not yet dubbed BA.2 a "variant of concern," it is tracking the sub-lineage's spread.

The Omicron variant B.1.1.529 has four sub-lineages: BA.1, BA.1.1, BA.2 and BA.3.

The BA.2 sub-lineage is widely considered "stealthier" than the original version of Omicron because some of its genetic traits make it harder to detect. Some scientists say it could also be more contagious, however they acknowledge there are still a lot of unknowns about the subvariant.

"We're still learning, of course, about this subvariant, but at the moment, the international data suggests that it could potentially have an increase advantage on spread," Tam said. "There doesn't seem to be any specific increase in hospitalizations or the severe outcomes compared to BA.1, but we'll be tracking that very closely."

While cases of the subvariant are increasing around the world, Tam said it is still too soon to know how it will impact Canada amid the current wave.

"The vast, vast majority of our identifications are the BA.1, but that doesn't mean BA.2 couldn't pick up later on. There's always a possibility that that could occur, but we don't actually know that yet," Tam said.

"At the moment it is really a BA.1 Omicron wave," she added.

PHAC told CTVNews.ca on Wednesday BA.2 has "many similarities" to BA.1, but does exhibit some differences, including in mutations that may affect transmissibility, detection and possibly immunity evasion.

"There is very limited evidence at present to determine how impactful the differences between BA.1 and BA.2 may be, hence the ongoing efforts by PHAC scientists to monitor cases here in Canada and track developments internationally," PHAC said in the statement.

Despite ongoing uncertainty around the subvariant, the health agency says Canadians should continue to follow the advice of public health officials.

"While the impact of all variants continues to be monitored in Canada, the Government of Canada knows that vaccination, in combination with public health and individual measures, is key to reduce the spread of COVID-19 and its variants," PHAC said.