A year after the discovery of a variant of the coronavirus called Omicron, virologists are still trying to keep up with its rapid evolution.

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A gloomy forecast

On November 26, 2021, the World Health Organization announced that a new variant of the coronavirus, now known as Omicron, had been found in southern Africa.

It soon became dominant around the world, causing a record spike in cases of the disease.

Now, biologists are still trying to keep up with Omicron's strange evolutionary twists, but it's mutating very quickly.

Instead of a single line, the mutations have grown into hundreds of lines, each with its own alphanumeric name (such as XBB, BQ.1.1, or CH.1) and resistance to the human immune system.

"It's hard to remember what came from what," says Jesse Blum, a virologist at the Fred Hutchinson Cancer Center in Seattle.

"But unless some radically different variant appears, this confusing mixture of sub-variants will persist, and it will make it difficult for scientists to plan new vaccines and treatment methods."

"It will always be like it is now," predicts Dr. Blum.

"There will always be a bunch of new options."

Omicron gave birth to mice?

When Omicron appeared last November, it carried more than 50 mutations that distinguished it from other variants of the coronavirus.

Many researchers have supported the idea that Omicron originated in a single person, possibly with a weakened immune system, who had a chronic, months-long case of COVID-19.

However, last month, a group of scientists from the University of Minnesota suggested that at some point in the pandemic, an early form of the coronavirus infected mice, and in rodents the virus turned into Omicron, which then reinfected humans.

Either way, Omicron began to dominate within weeks of its discovery due to its mutations.

Some of them allowed the virus to more successfully penetrate inside the cells.

Others allow it to evade certain antibodies that have arisen after vaccination or previous infections.

Most antibodies attach to the spike-like protein on the surface of the coronavirus and block its penetration into the cell.

But some of Omicron's mutations have changed parts of the spike protein so that some of the most powerful antibodies can no longer stick to it.

Omicron was ready for an evolutionary explosion

In February 2022, a virologist from Rockefeller University in New York, Theodora Hadzyianu, and her colleagues conducted an experiment that showed that Omicron was ready for an evolutionary explosion.

Dr. Hadzyianu's team tested Omicron for 40 different antibodies that could still block this variant.

The scientists discovered that a few additional mutations made him resistant to almost all forty antibodies very easily.

Surprisingly, when the researchers gave the same mutations to the spike-like protein of the original version of the coronavirus, it did not affect its resistance to antibodies.

Dr. Hadzyianu suspected that the large number of new mutations in Omicron had altered its evolutionary landscape, facilitating the development of even greater resistance.

"We were really concerned when we saw it," she said.

In the following months, Omicron justified these fears.

Due to the huge number of infections, he had more opportunities for mutations.

And he acquired some of the disturbing changes that Dr. Hadzyianu and her colleagues discovered in their experiments.

Where do new mutations lead

Mutations accumulate quickly because they give viruses a great evolutionary advantage.

In the first year of the pandemic, most of those infected had no antibodies.

Now, most people have them.

Therefore, viruses that have additional resistance to antibodies easily defeat other variants that do not have such resistance.

"The current evolution of the virus is the fastest it has been so far," says Sergei Pond, a virologist at Temple University in Philadelphia.

Competition among subvariants may prevent one of them from gaining the upper hand, at least for the time being.

In the United States, the once-dominant BA.5 now accounts for only 19 percent of new cases.

His descendant BQ.1 grew to 28 percent.

And BQ.1.1., a descendant of BQ.1, is now the cause of 29 percent of cases.

Thirteen other Omicron subvariants make up the remaining percentage.

Elsewhere in the world, other subvariants rise to the top.

Singapore, for example, experienced a surge in the XBB, a hybrid of two different BA.2 sub-variants.

But XBB is rare in most other parts of the world.

The one who sowed the territory first has an advantage, says Thomas Peacock, a virologist from Imperial College London.

As each lineage acquires more mutations, fewer types of antibodies work against them.

Last month, Peking University biochemist Yunlong Cao and colleagues reported that XBB and three other subvariants became completely resistant to antibodies in blood samples from people who had been vaccinated against or had contracted COVID-19.

A threat to the most important method of treatment

These viral developments threaten what has been one of the most important defenses against COVID-19: the monoclonal antibody.

To create this drug, scientists at the beginning of the pandemic collected the blood of patients with COVID-19, isolated their most powerful antibodies and made a huge number of new molecules.

One such drug, called Evushheld, can prevent infection in people with weakened immune systems.

But as resistant subvariants become more common, these treatments will no longer work.

"I can't be sure whether monoclonal antibodies will play an important role in the future," says Dr. Blum of the Fred Hutchinson Cancer Center.

"It is very important to develop a new generation of antibody cocktails that will hopefully work longer."

A new hope for medics

Recent booster vaccinations cause the birth of spiked proteins of both the original version of the virus and BA.5.

Studies of people who have received this bivalent booster show that their antibodies are better at neutralizing BQ.1.1 and other subvariants than the antibodies produced by the original COVID-19 vaccine.

But even in this case, subvariants can evade many bivalent antibodies.

Fortunately, the new sub-variants do not appear to be any more lethal than the earlier Omicron forms.

Despite their increased ability to evade antibodies, Dr. Hadzyianu said the subvariants probably won't be able to completely evade immunity from vaccines or previous infections.

Moritz Gerstung, a biologist at the German Cancer Research Center in Heidelberg, said that the lessons scientists are now learning from the convergence (mixing) of the Omicron may allow them to predict its future evolution.

And these predictions, in turn, can allow authorities to prepare more effectively for the next phase of COVID-19.

"It gives me great hope for the future as a paradigm," said Dr. Gerstung.

"This is an example of how you can basically get ahead of the virus."

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• Siarhei Ablameyka

  Radio Svaboda journalist

  ablameikos@rferl.org

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