A new COVID-19 subvariant has emerged. Here is why experts in Ontario say there is no reason to panic

A pharmacist holds a Pfizer and BioNTech COVID-19 vaccine shot on Thursday, April 24, 2025, in Portland, Ore. (AP Photo/Jenny Kane)

A new subvariant of COVID-19 that has been circulating in some parts of the world for months has now made its way to the United States but experts say that there is no cause for concern just yet.

According to the World Health Organization (WHO), NB.1.8.1 derives from the recombinant variant XDV.1.5.1 and is one of six current “variants under monitoring” due to its mutations and global spread.

Dr. Fahad Razak, Canada Research Chair at the University of Toronto and internal medicine physician at St. Michael’s Hospital, tells CTV News Toronto that a variant under monitoring—or a VUM—is different from variant of concerns, which often resulted in an exponential rise in transmission when they emerged and quickly became dominant during the pandemic.

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The key difference between both variant types, Razak says, is that VUMs will likely not swamp the health-care system or cause more severe illness like variants of concern will.

“Over the last couple of years, despite seeing many mutations, we have not had a new variant of concern emerge and this current variant, NB.1.8.1 is being called a variant (under) monitoring, meaning that it is clearly spreading, but it is not showing any of those concerning features that make us more worried,” Razak said.

Here’s what we know about the new subvariant so far:

What is NB.1.8.1?

The WHO says NB.1.8.1 has been detected in 22 countries as of May 18. This represented 10.7 per cent of COVID cases seen worldwide in the last full week of April, which the WHO says is a notable rise from the 2.5 per cent noted in the first week of April.

Compared to other co-circulating variants, the number of cases related to NB.1.8.1 is growing faster—however, the WHO notes its expansion has only recently started to rise and that some regions have not yet detected it.

Has it made its way to Ontario?

Based on the latest data from the Public Health Agency of Canada (PHAC), which breaks down the percentage of COVID-19 cases by variant grouping on a weekly basis, there are no cases of NB.1.8.1. recorded in the country.

Both Razak and Infectious diseases expert Dr. Isaac Bogoch say it is likely the new variant will make its way here eventually but Razak notes Canada does not provide a “reliable estimate across the country anymore.”

“We used to do regular testing for sequence across the country. They would be coordinated by public health labs in each province and then collated federally,” Razak said. “That was done during the peak of the pandemic and (had) a lot of value in helping us understand the degree of spread, especially when we had these variants of concern.”

If there was a new variant that showed more severe disease, a high degree of spread or evading the vaccine, Razak thinks many parts of the world would be vulnerable since the level of monitoring is not what it used to be.

“We don’t have the level of uptake of vaccines that we had two or three years ago, and so those factors would mean you could have something spread and you would have lower levels of protection, and so you could have a lot of people sick,” Razak said.

But, Razak says, that there hasn’t been a major variant of concern in years.

Public Health Ontario tells CTV News Toronto that, to date, this variant has not been included in its reporting but note its next report will be published next week.

Toronto Public Health, meanwhile, does not break down what variants of COVID-19 are seen in in the city. It does provide general data for how prevalent the virus is at this time.

The latest epidemiological data from TPH shows a 1.8 per cent positivity rate from May 11 to May 17, showing the activity levels of the virus are currently “low.”

Are the symptoms any different?

Bogoch says the symptoms from NB.1.8.1. are similar to what one would get if they contracted any Omicron sub-lineage in the last three years, which could cause fever, fatigue, cough, and shortness of breath.

“There’s a well-trodden path of who’s at greater risk for more severe manifestations of the virus, namely, people on the older end of the spectrum and people with underlying medical comorbidities,” Bogoch said. “So, it doesn’t sound like, apart from a subtle genetic change, it doesn’t sound like there’s anything new about this (variant) in terms of clinical presentation, risk factors for severity of illness (and) transmission.”

The guidance on how to protect yourself also remains unchanged, Razak says.

“When you have periods like this, like, let’s say we have started to see a high degree of spread in Canada, the advice that we’ve given the last few years would hold just as strongly. If your vaccine hasn’t been updated, update your vaccine,” Razak said.

Masking in crowded places, frequently washing hands and enhancing air circulation when indoors are also other methods to prevent the virus from spreading between person to person.

What if you haven’t had a recent vaccine?

Bogoch says that, for some time now, the COVID-19 vaccines “doesn’t protect against infection nearly to the same extent as it once did.”

“The vaccines can provide a little bit of protection against infection for a short period of time—they can—but the real role of the vaccine is to significantly reduce the risk of severe illness that is primarily in those with risk factors for severe illness,” Bogoch said. “Long are the days where the vaccine was a formidable force in preventing infection and subsequent onward transmission. We haven’t been that era in years.”

The vaccine can reduce the risk of infection but after about six months, its protection starts to wane, Razak says.

“Our National Advisory Committee on Immunization, they have continued to say that high-risk individuals—for example, older individuals, people who are immunosuppressed, people who are being treated for rheumatologic illness or cancer where their immune systems are notworking—they would benefit from getting their updates every six months,” Razak said.