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‘Hidden’ Omicron Variant Has No Cause for Alarm, But Could Slow the Case


Recently a “stealth” Omicron variant They brought to mind the idea that a new and nasty form of the corona virus was secretly creating a disastrous new wave of Covid.

Scientists say this scenario is highly unlikely. However, the new variant, which goes by the scientific name BA.2 and is one of the three branches of the Omicron viral family, can eliminate the Omicron surge in many parts of the world.

So far, BA.2 does not appear to cause more severe disease, and vaccines are as effective against it as against other forms of Omicron. But it shows signs of easier spread.

“This could mean higher peaks of infection in places that have not yet peaked and a slowdown in downtrends in places that have experienced an Omicron peak,” said Thomas Peacock, a virologist at Imperial College London.

Researchers in South Africa in November 2021 raised the alarm first It’s about Omicron, which carries 53 mutations that distinguish it from the first strain of coronavirus isolated in Wuhan. Some of these mutations allowed him to evade antibodies produced by vaccines or previous infections. Other mutations seem to have concentrated it in the upper airway. not in the lungs. Since then, Omicron’s genetic changes have propelled him to dominate the world.

But a few weeks after Omicron’s appearance, researchers in South Africa several surprising, Omicron-like variants. The viruses shared some of Omicron’s distinctive mutations, but lacked others. They also carried some unique mutations of their own.

It was soon realized that the Omicron consisted of three separate branches that diverged from a common ancestor. Scientists named the branches BA.1, BA.2 and BA.3.

The earliest Omicron samples belonged to BA.1. BA.2 was less common. Even rarer, BA.3, some kind of viral sex: BA.1 and BA.2 infected the same individual simultaneously and their genes were scrambled to form a new viral hybrid.

At first, scientists focused their attention on BA.1 because its occurrence was 1,000 to one higher than the others. A lucky break made it easy for them to follow.

Common PCR tests typically detect three coronavirus genes. But tests can only identify two of these genes in BA.1, due to a mutation in the third gene known as spike.

In December, researchers in South Africa discovered that a growing number of PCR tests are failing to detect the spike gene – a sign that BA.1 is becoming more common. (The time-dominant variant, known as Delta, did not cause spike errors in PCR tests.) Delta decreased as the Omicron rose.

Unlike BA.1., BA.2 lacks the spike mutation that causes PCR tests to fail. Without the ability to use PCR tests to monitor BA.2, some scientists have dubbed it the “hidden” version of Omicron.

But BA.2 wasn’t invisible: Researchers could still track it down by analyzing the genetic sequences of samples from positive tests. And with Delta nearly gone, scientists can use PCR tests to tell the difference between BA.1 and BA.2: Samples that cause spike errors contain BA.1, while samples that don’t contain BA.2.

In recent weeks BA.2 has become more common in some countries. Statens Serum Institut, BA.2 accounts for 65 percent of new cases in Denmark reported Thursday. But so far, researchers there have found that people infected with BA.2 are not more or less likely to be hospitalized than those infected with BA.1.

On Friday, the British government released another early analysis He found from BA.2 that the variant made up only a few percent of the cases out there. Still, surveys in the UK show it’s growing faster than BA.1 because it’s more contagious.

Reassuringly, British researchers found that the vaccines were just as effective against BA.2 as BA.1.

Trevor Bedford, a virologist at the Fred Hutchinson Cancer Center in Seattle, found a similar pattern in viral sequences from post-test samples in the United States. he estimated He added that about 8 percent of cases in the United States are BA.2, and that figure is climbing rapidly.

“I’m pretty sure it will become dominant in the US, but I don’t know yet what that will mean for the pandemic,” said Nathan Grubaugh, an epidemiologist at Yale University’s School of Public Health.

It is conceivable that BA.2 could lead to a new increase, but Dr. Grubaugh thinks Covid cases are more likely to continue falling in the coming weeks. It is also possible for BA.2 to create a small hump on its way down or just slow down the fall. Experiments currently being done on BA.1 could help scientists sharpen their guesses.





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