TRENTON, Canada (AA) – Omicron offshoots are gaining traction in the US and Canada, it was reported Thursday, the same day mandatory coronavirus testing for arrivals from China takes effect in both countries.

Many variants are battling to become the most prevalent virus and the US Centers for Disease Control and Prevention predicted about 40% of the country’s cases are from offshoots of the virus while in the UK, they account for one-in-25 cases.

Reports are that the Omicron variant, XBB.1.5, is the dominant offshoot in the US. But in Canada figures are not completely reliable since provinces were tardy in reporting cases due to the holiday season.

“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 the Canadian Broadcasting Corporation (CBC) in a statement Tuesday.

But PHAC reported Wednesday that it has knowledge of 21 XBB.1.5 cases but said it could be higher.

Experts said XBB.1.5 will likely become the dominant virus amongst a field of several contestants.

“I would expect that it will eventually outcompete the currently predominant BA.5-derived lineages in Canada,” Art Poon, a professor of viral evolution and bioinformatics at Western University in Canada, told the CBC.

Since the XBB.1.5 variant was discovered in October, it has been found in 25 countries, according to the World Health Organization.

The problem is that XBB.1.5 could include mutations that attach to human cells and slip through immune systems.

Still, no one is hitting the panic button just yet.

“At this time there is no alarm,” said researcher and variant tracker Fiona Brinkman, from Simon Fraser University in British Columbia. “But we are definitely cautiously watching this and other variants that are showing signs of having key mutations.”

It could, however, lead to more infections as hospitals are struggling to cope with COVID cases.

Officials said mandatory testing of Chinese travelers is due to a rise in cases in that country and a lack of information from Beijing about case numbers.