Here’s what we know about COVID subvariant XBB. 1.5 in Canada

A new highly transmissible COVID subvariant that has drawn the concern of the World Health Organization and now makes up at least 40 per cent of COVID cases in the United States is making itself known in Canada, too.

At least 21 cases of XBB. 1.5, an Omicron subvariant, have been detected in this country, the Public Health Agency of Canada says.

The agency is tracking the spread of the subvariant, though it is not yet listed as a variant of concern.

“PHAC scientists continue to monitor cases in Canada and track developments internationally,” PHAC said. “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.”

South of the border, XBB. 1.5 has been on a trajectory that doesn’t appear to be slowing down.

In mid-November, only 0.3 per cent of COVID cases in the U.S. were confirmed to be XBB. 1.5, according to data from that country’s Centers for Disease Control. By the end of December, XBB. 1.5 was responsible for more than 40 per cent of cases.

In late October, the World Health Organization reported the XBB. 1.5 subvariant had been detected in 35 countries and cited higher reinfection risks compared to other circulating Omicron sublineages. XBB and its sublineages are a recombination of the Omicron BA2.10.1 and BA. 2.75 variants, WHO said, meaning the viruses exchanged genetic material to create a new subvariant.

In British Columbia, 12 cases of XBB. 1.5 were detected in the Vancouver Coastal Health and Fraser Health regions, according to the British Columbia Centre for Disease Control. It’s unclear how many XBB. 1.5 cases are circulating in that province as PCR tests — the tests needed to sequence the virus to identify variants — are used mainly in health-care settings, such as hospitals.

The British Columbia Centre for Disease Control said XBB. 1.5 is “of interest” because it has acquired additional mutations that enhance its binding properties. “These mutations may indicate that this variant is able to spread more easily but it does not mean that it is more severe,” the centre said.

For the week of Dec. 11, the latest publicly available data from the federal government’s COVID-19 epidemiology update, BA. 5 made up most COVID-19 cases in Canada, sitting just above 92 per cent of all tested cases. Less than one per cent of cases at that time were caused by XBB. 1.5