EXPLAINER: What is known about the ‘stealth’ version of omicron?

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Scientists and health officials around the world are keeping an eye on a descendant of the omicron variant that has been found in at least 40 countries, including the United States.

This version of the coronavirus, which scientists call BA.2, is considered stealthier than the original version of omicron because particular genetic traits make it slightly harder to detect. Some scientists fear that it could also be more contagious.

But they say there’s still a lot they don’t know about it, including whether it evades vaccines better or causes more serious disease.

WHERE HAS IT SPREAD?

Since mid-November, more than three dozen countries have uploaded nearly 15,000 BA.2 genetic sequences to GISAID, a global platform for sharing coronavirus data. As of Tuesday morning, 96 of those sequenced cases were from the US.

“So far, we haven’t seen it start to gain traction” in the US, said Dr. Wesley Long, a pathologist at Houston Methodist in Texas, who identified three cases of BA.2.

The mutant seems much more common in Asia and Europe. In Denmark it accounted for 45% of all COVID-19 cases in mid-January, up from 20% two weeks earlier, according to the Statens Serum Institut, which reports to the Danish Ministry of Health.

WHAT IS KNOWN ABOUT THIS VERSION OF THE VIRUS?

BA.2 has many mutations. About 20 of them in the spike protein that studs the exterior of the virus are shared with the original omicron. But he also has additional genetic changes not seen in the initial version.

It’s not clear how significant those mutations are, especially in a population that has been found with the original omicron, said Dr. Jeremy Luban, a virologist at the University of Massachusetts Medical School.

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For now, the original version, known as BA.1 and BA.2, are considered subsets of omicron. But world health leaders could give it its own Greek-letter name if it’s deemed a “variant of concern” of global importance.

The rapid spread of BA.2 in some places raises concerns that it could take off.

“We have some indications that it may be as contagious or maybe a little more contagious than the (original) omicron in that it may compete with it in some areas,” Long said. “But we don’t necessarily know why that is.”

An initial analysis by scientists in Denmark shows no difference in hospitalizations for BA.2 compared to the original omicron. Scientists are still investigating the infectivity of this version and how well current vaccines against it work. It’s also unclear how well the treatments will work against you.

Doctors also don’t know for sure if someone who already had COVID-19 caused by omicron can get sick again from BA.2. But they are hopeful, especially that a previous omicron infection might lessen the severity of the disease if someone later gets BA.2.

The two versions of omicron have so much in common that it’s possible that infection with the original mutant “provides cross-protection against BA.2,” said Dr. Daniel Kuritzkes, an infectious disease expert at Brigham and Women’s Hospital.

Scientists will test to see if antibodies from an infection with the original omicron “can neutralize BA.2 in the lab and then extrapolate from there,” he said.

HOW CONCERNED ARE HEALTH AGENCIES?

The World Health Organization classifies omicron overall as a variant of concern, its most serious designation of a mutant coronavirus, but does not single out BA.2 with a designation of its own. However, given its rise in some countries, the agency says investigations of BA.2 “should be given priority.”

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Meanwhile, the UK Health Security Agency has designated the BA.2 as a “variant under investigation”, citing the increasing numbers found in the UK and internationally. Still, the original version of omicron remains dominant in the UK.

WHY IS IT MORE DIFFICULT TO DETECT?

The original version of omicron had specific genetic characteristics that allowed health officials to quickly differentiate it from delta using a certain PCR test due to what is known as “S-gene target failure.”

BA.2 does not have this same genetic peculiarity. So in the test, Long said, BA.2 looks like delta.

“It’s not that the test doesn’t detect it; it just doesn’t look like omicron,” he said. “Don’t be under the impression that ‘stealth micron’ means we can’t detect it. All of our PCR tests can still detect it.”

WHAT SHOULD YOU DO TO PROTECT YOURSELF?

Doctors are recommending the same precautions they’ve always taken: get vaccinated and follow public health guidelines about wearing masks, avoiding crowds and staying home when you’re sick.

“Vaccines still provide a good defense against serious illness, hospitalization and death,” Long said. “Even if you’ve had COVID 19 before, you’ve had a natural infection, the protection from the vaccine is even stronger, longer-lasting and, in fact, good for people who have been infected before.”

The latest version is another reminder that the pandemic is not over.

“We all wish this was all over,” Long said, “but until we vaccinate the world, we are at risk of new variants emerging.”

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

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George Holan

George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.

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