Why XBB.1.5 — the latest Omicron offshoot — could 'outcompete' other COVID-19 subvariants
CBC
It's been a year since Omicron burst onto the scene, spiking COVID-19 case counts to new heights and dramatically changing the trajectory of the pandemic.
Since then, the variant has spawned a family of highly transmissible cousins. Some have fuelled rolling waves of infections; others largely disappeared.
Most recently, multiple mutated versions of the original Omicron seemed locked in a delicate dance for dominance.
In the U.S., there's now a likely winner: XBB.1.5.
The Omicron offshoot is rising rapidly south of the border, and the U.S. Centers for Disease Control projects it will soon hit roughly 40 per cent of COVID-19 cases. Meanwhile, surveillance data in the U.K. suggests it represents 1 in 25 COVID-19 cases, and could eventually become the next dominant strain.
The situation in Canada is more murky, given delays in data collection from across the provinces over the holidays.
"At this time, it is too early to tell if the XBB.1.5 variant is growing in Canada," the Public Health Agency of Canada (PHAC) told CBC News in a statement on Tuesday.
A day later, PHAC said it is aware of 21 detections of XBB.1.5 in Canada — though the full tally, based on the latest-available provincial and regional surveillance, appears slightly higher.
As of Wednesday, 12 cases of XBB.1.5 had been detected in B.C. in the Vancouver Coastal Health and Fraser Health regions, according to the B.C. Provincial Health Services Authority, while Art Poon, a professor in viral evolution and bioinformatics at Western University, said he knows of 24 genomes classified as XBB.1.5 that have been submitted nationally to date.
Those were largely sampled from Ontario, plus one from Nova Scotia and a few from Quebec — representing only a "small fraction of infections."
But that could change.
"I would expect that it will eventually outcompete the currently predominant BA.5-derived lineages in Canada," Poon wrote in an email to CBC, "although there are other lineages that we expect to grow in frequency as well."
XBB.1.5 was first detected in October, according to World Health Organization (WHO) officials, and has since been identified in 25 countries.
The SARS-CoV-2 subvariant evolved out of Omicron's BA2 offshoot, making it one of the latest members of a family tree that's "incredibly branched and tangled and confusing," said Angela Rasmussen, a virologist with the University of Saskatchewan's Vaccine and Infectious Disease Organization.
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