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Provincial health officer Dr. Bonnie Henry told Global News that officials have not seen the subvariant 'take off yet.'CHAD HIPOLITO/The Canadian Press

The British Columbia Centre for Disease Control has found five cases of the XBB.1.5 subvariant of Omicron, which is believed to have become the most dominant strain of COVID-19 in the United States over the holidays.

The provincial agency confirmed the cases on Tuesday but did not say when and where it detected XBB.1.5, which scientists say is more transmissible than other variants but may not cause more severe disease.

The subvariant appears to have first arrived some time in the week leading up to Dec. 10, according to a Dec. 21 report from the BCCDC on variants of concern. The report noted that XBB.1.5 had been detected in the Fraser Health Authority, which oversees a vast area to the east and south of Vancouver, but did not indicate how many cases had been found.

B.C., like other provinces, no longer offers widespread testing for COVID-19 and only tests the small proportion of cases involving patients with more severe illness or those at higher risk.

The federal government’s public case dashboard previously reported that XBB.1.5 was first detected in 0.1 per cent of the nearly 3,000 genomic tests done across the country the week of Nov. 20. The latest publicly available data, from the week of Dec. 11, show it was found in 0.6 per cent of the thousand or so samples tested.

Health ministries in Alberta, Manitoba and Ontario were not able to say Tuesday whether their testing regimes have found this subvariant of Omicron, which the U.S. Centers for Disease Control and Prevention estimates became the most dominant form of the virus in that country the week after Christmas Day, when it represented about 40 per cent of new cases.

In an interview broadcast Monday, B.C.’s Provincial Health Officer Bonnie Henry told Global News that officials have not seen the subvariant “take off yet.”

“It’s not increasing rapidly here but it is one of the subvariants that we know can take off, particularly areas where you have lower vaccination rates,” she said in a remote interview. “What we don’t know is: Is this a strain that’s going to cause more severe illness and hospitalization innately? It doesn’t look like that.”

Robert Delatolla, a professor of environmental engineering, and a team at the University of Ottawa are now waiting to test samples of waste water collected in Canada’s capital over the winter break, when their on-campus lab was closed because shipping and receiving services were unavailable. He said Tuesday that XBB.1.5 did not show up in samples collected before Christmas.

“We’re hoping we don’t see it, but considering everything out of Vancouver and B.C., we’re not as hopeful,” said Dr. Delatolla, whose team has been analyzing sewage for COVID-19 since April, 2020.

Last week, Dr. Delatolla said, his team drove to the treatment plants to pick up and test some samples for overall prevalence of all strains of the virus. They found the past five days of data showed concentrations of COVID-19 that were nearly half as high as the pandemic peak reached around this time last year when Omicron cases surged, he said. The week prior, all forms of the virus were only at about 20 per cent of that peak, he added

Although COVID-19 is not as threatening as it once was, public-health officials across the U.S. have expressed wariness of rising case counts, particularly as part of a “tri-demic” of COVID-19, respiratory syncytial virus (or RSV) and the flu. Parts of the U.S. have warned about localized shortages of drugs to treat sick patients, including some antibiotics and pain relievers.

Isaac Bogoch, an infectious-diseases specialist at the University Health Network in Toronto, said it is unsurprising that a new variant is overtaking others to drive infections and that tools exist for people and politicians to blunt its impact, namely boosters of vaccines and masking indoors.

Dr. Bogoch, who said the vast majority of people being hospitalized by the virus are older than 60, said it is important for governments across Canada to make boosters as easy as possible to get for immunocompromised people and seniors who haven’t had a shot in the past six months.

“That’s really the important one,” he said.

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