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The Mu variant of COVID-19 is in B.C. Here's what you need to know

Dozens of cases of the Mu COVID-19 variant — recently declared a variant of interest — have been identified in B.C. According to the B.C.
Mu strain
The Mu coronavirus strain discovered in Colombia raised concerns around the world after it caused isolated outbreaks in 2021. SEBASTIAN CONDREA, GETTY IMAGES

Dozens of cases of the Mu COVID-19 variant — recently declared a variant of interest — have been identified in B.C.

According to the B.C. Centre for Disease Control’s latest weekly update on variants of concern and variants of interest, there have been 46 Mu cases detected since June, including two in the most recent week.

Even before the World Health Organization declared the B.1.621 variant a variant of interest and named it Mu on Aug. 30, the B.C. centre had been keeping an eye on it through its whole genome sequencing system. In B.C., every positive COVID-19 test result is further analyzed to see whether it is a variant of concern, a variant of interest or an emerging variant.

The highly contagious Delta variant of concern that has taken over the world now accounts for close to 100 per cent of all cases in B.C. Other variants of concern — Gamma, Beta, Alpha and others — are now mostly non-existent in the province.

While the Mu variant is in B.C. in relatively very low numbers, it’s worth keeping an eye on. Here are some things to know:

What is the Mu variant?

It's a version of the coronavirus that was first identified in Colombia in January and has since caused isolated outbreaks in South America, Europe and the United States.

The World Health Organization last month listed it as a “variant of interest” because of concerns it may make vaccines and treatments less effective, though more evidence is needed.

Scientists monitor emerging COVID-19 variants based on suspicious genetic changes and then look for evidence to determine whether the new version is more infectious or causes more severe illness. Viruses evolve constantly and many new variants often fade away.

So far, the Mu variant doesn’t seem to be spreading quickly: It accounts for fewer than one per cent of COVID-19 cases globally. In Colombia, it may be responsible for about 39 per cent of cases. Most countries remain concerned about the highly contagious Delta variant; it is the dominant variant in almost all of the 174 countries where it's been detected.

Where has it been found?

Officials have been tracking the mu variant in Europe, where it has been seen in about a dozen countries. The French Ministry of Health recently said the Mu variant “does not seem to have increased recently” across Europe.

A report from England's public health agency last month suggested the mu variant might be as resistant to vaccines as the worrisome beta variant first seen in South Africa, but said more real-world data was needed.

WHO officials said the Mu variant appears to be rising in some countries in South America, but that the delta variant still spreads far more easily.

The Mu variant "is of interest to us because of the combination of mutations it has,” said WHO’s Maria Van Kerkhove. “But it doesn’t seem to be circulating.”

The U.S. is “paying attention to it,” but it isn't considered an immediate threat, said Dr. Anthony Fauci, the top U.S. infectious disease expert.

What threat does the Mu variant pose in B.C.?

In British Columbia, the Mu variant represents a very small number of new cases. Dr. Sarah Otto, in the department of zoology at the University of British Columbia, said that although Mu only received an official designation in August, it has been circulating in the province for a long time.

Forty-six cases of the variant have been identified in B.C. so far, but she notes that six of these cases were “reported from sequencing conducted through the end of June.”

Across the rest of the country, “the fraction of cases due to Mu has hovered at [a] low [percentage] for a long time,” she said. “If anything, [it] shows recent declines.”

And although Mu “better evades the ‘first’ step in our immune reaction (neutralizing antibodies),” Otto notes that there isn’t evidence that it has a higher transmission rate than Delta or that it has “an appreciably higher chance of evading all of the other steps in our immune response (cellular immunity).”

Dr. Jeffrey Joy, Assistant Professor, Department of Medicine, UBC also emphasized this point. He said the strain does have “a variety of mutations which laboratory studies have confirmed allow it to evade our immune responses more than many other variants of SARS-CoV-2” but that it doesn’t have the capacity to read as rapidly as the Delta variant.

“At this point, it is a bit early to say what kind of threat it poses to B.C.,” he said. “However, it would be expected to spread less rapidly than the Delta variant.”

— With files from Vancouver Is Awesome, The Canadian Press and the Associated Press