Omicron subvariant BA.2 raises new questions about the mysterious evolution of the virus behind COVID-19.

BA.2 attracted the attention of virologists after it began to rise in multiple countries, including early signs of a slight rise in Canada. This suggests that it may be even more contagious than its predecessor.

“There is competition,” said Natalie Granvaux, a researcher and professor of biochemistry and molecular medicine at the University of Montreal. “It’s a bit like Delta vs. Alpha … does that mean we have another wave? That’s not what we can say so far.”

Denmark, in particular, has reported a surge in BA.2 infections, with subvariants accounting for almost half of all Omicron cases by the second week of January, up from about 20% at the end of 2021.

“During the same period, the relative frequency of BA.1 decreased,” said the Danish National Institute of Serum (SSI), a Danish research institute. Reported on January 20..

The UK is also closely monitoring BA.2, officials said Technical briefing in mid-January This subvariant can often fly under radar. BA.1 lacks one of the three target genes used in the extensive SARS-CoV-2 test, but is easy to find — a process known as S gene targeting disorder — BA.2. Cannot be detected in the same way.

By January 1, BA.2 accounted for 5% of UK S-gene positive tests, and that number continues to rise, according to the same report.

This means that a rapid S-gene disorder method to catch Omicron infection is “no longer sufficient to assess the spread of Omicron as a whole.”

So far, “there is no big alarm bell”

In contrast, for many of the first years of the pandemic, it was much easier to track and manage the evolution of this virus.

This changed first when the B117 variant (later called Alpha by the World Health Organization) appeared in late 2020, and the number of cases increased thanks to a series of mutations that helped to spread rapidly around the world. Did.

As the number of cases soared, the evolutionary process seemed to overdrive, and variants began to change.

Surprisingly, the Danish SSI states that the difference between BA.1 and BA.2 is even greater than the difference between the original strain of SARS-CoV-2 and the Alpha variant.

on Monday, World Health Organization said Studies on how BA.2 works should be “prioritized independently” from other Omicron subvariants.

Jesse Shapiro, an associate professor of microbiology and immunology at McGill University, has a global signal that the BA.2 subvariant is somewhat contagious, reflecting the early days of the Omicron epidemic.

“There is no big alarm so far,” he said, although it could drag the wave of infection.

Questions about immune avoidance

Still, questions remain about BA.2’s ability to respond to the increasing number of people who have already dealt with Omicron infection. Can that dramatic evolutionary change avoid the immunity of millions of people infected after late 2021 weeks ago?

With several recorded cases of reinfection in Norway, BA.2 could infect some people who have already recovered from BA.1 and boost the number of cases, SSI’s doctor and virus study Anders Fomsgaard said. During a recent interview with the Danish media..

However, Matthew Miller, an associate professor of infectious diseases and immunology at McMaster University, predicts that this type of reinfection is unlikely. Even more worrisome, he suggested, was the effect of his “sister” on Omicron, which spread to unprotected populations.

“I have only been vaccinated twice, or I have not been vaccinated, or [are] Due to incomplete vaccination, they may be as susceptible to BA.2 as Omicron. “

The reassurance (at least for now) about BA.2 is that the first analysis of the SSI shows that there is no difference in hospitalization when compared to BA.1. Further research is underway to understand the effects of variants on the efficacy of vaccines, according to SSI, but vaccines are expected to continue to provide protection against serious illnesses.

Subvariants also make up only a small fraction of the total number of known COVID-19 cases in Canada, but appear to be increasing, according to federal data.

Omicron infections account for more than 90% of recent cases in Canada, and almost all of them remain BA.1. However, BA.2 infections accounted for about 1% of cases reported in early January, up from only 0.2% in late December, and data in that range are still accumulating.

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Angela Rasmussen, a virologist at the University of Saskatchewan’s Vaccine Infectious Diseases Organization, emphasized that these minorities may remain the same, unlike the situation in Denmark, where potential takeover of BA.2 is a concern.

“The important thing to remember here is that Denmark is not Canada. Denmark is a different population and has different vaccine intakes, different medical histories and demographics,” she said. “Therefore, what is happening in Denmark is not always automatically translated into Canada.”

Mr. Granvo said that monitoring efforts will continue to be essential to capture and understand the spread of BA.2 cases, but given stealth, this can be a daunting task. Said it was expensive.

“We need to continue the sequence,” she said. “We need to know the behavior of this virus.”

Scientists confused by the origin of Omicron

Dallen Martin, a virologist at the University of Cape Town in South Africa, who warned the world of the existence of Omicron, also said it was important to understand why and how this variant evolved.

“We need to be serious and quickly find the conditions under which Omicron occurred, the mechanisms that work during the assembly of the complement of the mutation, and how to minimize the chances of these conditions recurring.” He said in an email interview in CBC News.

“The last thing we all want is another new super-evolutionary type. [variant of concern] Harvest every few months. “

Martin and a team of researchers recently shared Initial findings Note that for the original Omicron strain, many mutations in BA.1 are extremely rare and may not always be useful for evolving viruses.

Instead, those unique habits are part of the constellation of mutations that appear to give Omicron the mysterious ability to spread rapidly among human hosts and leave other variants in its dust.

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According to Martin, the concern is the fact that there are BA.2 and other strains as well as its mysterious original Omicron strain. All of these are closely related, but their unique characteristics raise questions about how they evolved fast enough to be discovered. By scientists around the same time.

“Viruses with much lower mutation rates than viruses like HIV and influenza, in a linear, step-by-step process, how each mutation reduces its fitness on its own, Was it possible to stitch together a large set of such interacting mutations? ”Martin asked.

“The conditions under which this evolution took place may need to be significantly different from the conditions for normal short-term SARS-CoV-2 infection.”

Some scientists theorize that Omicron suddenly spreads to humans with explosive power during long-term infections in immunocompromised patients or after it occurs in an animal host.

However, Omicron has come to suggest its presence, and its continuous morphological changes, the ability of the virus to evolve radically when infection remains at high levels around the world.

“It behaves as we can predict,” Granvo said. “Changes during transmission.”