Is the ‘Kraken’ surge starting? Cases of COVID Omicron subvariant XBB.1.5 shoot up in Ontario
Canada appears to be in for another wave of COVID-19 cases and associated hospitalizations as a new surge of the virus begins - this one fuelled by what the World Health Organization has called the most transmissible" subvariant seen so far.
New data released Tuesday by Public Health Ontario projects that XBB.1.5, known by the nickname Kraken," will be responsible for 22.2 per cent of all new COVID cases in this province before the end of the week.
Only three weeks ago, XBB.1.5 was responsible for just two per cent of Ontario's cases.
The report also shows that the Omicron subvariant BQ.1.1 remains the most prevalent lineage in the province, representing 31.3 per cent of cases, followed by BQ.1 at 9.5 per cent. Notably, BQ.1.1 has not become more prevalent over the past month.
In other words, you're getting this big surge in one variant and the other one is not, suggesting that this is the one that is going to take over," said Dr. Fahad Razak, an internist at St. Michael's Hospital and a professor at the University of Toronto's Institute of Health Policy, Management and Evaluation.
When you see that rise from two per cent to 20 per cent over a few weeks, that is exponential growth. So you're seeing a variant which is outcompeting other versions of the virus and displacing them."
The arrival of XBB.1.5 comes at a time when society seems to have largely moved on from the pandemic. We no longer test widely. Most health restrictions have been dropped. Hardly anyone wears a mask in public and our uptake of booster vaccines is low. In short, it is ripe pickings for a new, highly transmissible variant.
As for how many cases of XBB.1.5 are circulating, it's unclear. That's because Ontario no longer conducts widespread testing. Percentages are arrived at by testing a select group of people, such as high-risk patients, health-care workers and people in hospital, and assuming that the composition of variants detected represents the same in the greater population.
Of samples sequenced, XBB.1.5 was most prevalent in Ontario in people between the ages of 40 and 59, followed by those aged 20 to 39. To date, the public health units with the most XBB.1.5 detected are Niagara, Toronto, York and Haldimand-Norfolk.
The projections do not bode well for the rest of the country, as Ontario tends to dominate the signal in Canada, said Razak. Already, cases of the subvariant have been detected in British Columbia, Alberta, Saskatchewan and Quebec.
Currently, XBB.1.5 makes up 2.5 per cent of all cases in the country, according to the Public Health Agency of Canada.
Razak said it's likely the spread of XBB.1.5 in Canada will follow a similar pattern to that witnessed in the United States a few months ago. The variant was first detected in October in New York state and, within two months, became dominant in the U.S. northeast. By the end of last week, it had become the most common variant in the entire country, according to the Centers for Disease Control, representing some 43 per cent of all new infections.
On Jan. 6, World Health Organization director general Tedros Adhanom Ghebreyesus tweeted that XBB.1.5 is on the rise globally and had been identified in more than 25 countries.
Our concern is how transmissible it is," said Maria Van Kerkhove, the WHO's COVID-19 technical lead, earlier this month. It does have immune escape like we've seen with XBB. But it is another subvariant of Omicron that is in circulation and the more this virus circulates, the more opportunities it will have to change. We expect further waves of infection around the world."
XBB.1.5 is a descendant of the XBB Omicron subvariant, which is known as a recombinant" variant, essentially a mutant hybrid of two other sublineages of Omicron: BA.2.10.1 and BA.2.75.
Researchers at Peking University recently found in a preprint study that XBB seems to be capable of circumventing antibodies arising from both previous COVID infection and three-dose vaccinations, and even monoclonal antibody treatments.
Van Kerkhove said that while XBB.1.5 has a growth advantage over all other Omicron subvariants so far, there is no data that indicates it causes more severe disease.
However, Dawn Bowdish, a professor of medicine at McMaster University and Canada Research Chair in Aging and Immunity, notes that even if XBB.1.5 is not as severe, the fact that it is more transmissible means more people will get it, meaning more people will ultimately die.
There's a general truism in infectious disease that a highly deadly pathogen that doesn't transmit well is a smaller threat than a medium- or even a low-deadly pathogen that transmits very well, and that's because it's easier to find more vulnerable hosts," Bowdish said.
In truth, that's exactly what we saw with Omicron. Omicron outcompeted Delta because it was more transmissible, even though if you compare the clinical outcomes on a person-by-person basis, you would say Omicron is less deadly."
Indeed, more people died of COVID in Canada in 2022 than in any other year of the pandemic, while eight provinces, including Ontario, also saw more COVID deaths than in any other year.
With more people being infected, a mild to moderate increase can be expected in hospitalizations, said Razak, noting that typical protective strategies, such as masking and social distancing, will continue to be effective at limiting transmission.
Kenyon Wallace is a Toronto-based investigative reporter for the Star. Follow him on Twitter: @KenyonWallace or reach him via email: kwallace@thestar.ca