A second version of omicron is spreading. Here's why scientists are on alert

Just as the omicron virus starts to fade in some regions of the United States, scientists are keeping an eye on a new coronavirus variant spreading rapidly in Asia and Europe. It's formally known as "omicron BA.2," and scientists found cases of it this week in various states throughout the United States, including California, Texas, and Washington.

Although BA.2 is now rare in the United States, scientists predict it will expand next month. There's mounting evidence that it's just as contagious as the first omicron variant, known as "omicron BA.1," or possibly even more so.

"BA.2 may have a slight advantage," says Emma Hodcroft, an epidemiologist at the University of Bern who has been following variants all over the world via the Nextstrain project throughout the pandemic. "It's possible that BA.2 is 1% to 3% more transmissible, or anything along those lines."

So the central question now is whether that small differential will be enough to extend the current surge in the United States, as it did in Denmark?

What is omicron BA.2?

BA.2 might be thought of as a sibling of BA.1, according to Hodcroft. They have many mutations in general — about 30 —but also many unique mutations.

"They're a lot alike, but they're also very different," she explains. "In my opinion, they look a lot like siblings. Different, but linked."

When scientists in South Africa and Botswana found omicron in November, they didn't uncover just one type. The Phylogenetic Assignment of Named Global Outbreak Lineages at the University of Edinburgh discovered three, which they named BA.1, BA.2, and BA.3.

BA.1 was the first and spread quickly throughout the world, especially in the United States. Initially, it appeared that BA.2 and BA.3 were less capable of keeping up with BA.1.

"We felt, 'OK, BA.2 isn't quite as fit as its twin BA.1, and it'll fade,'" Hodcroft adds.

And that wasn't the case – not at all.

Is omicron BA.2 as transmissible as omicron BA.1?

Scientists have been shocked by omicron BA.2 over the last few weeks. And it's beginning to appear like it could be able to outcompete its sibling omicron BA.1 — and, indeed, any other variants — in some countries.

Omicron BA.1 produced a massive rise in cases in Denmark in December, similar to the surge in the US. However, just as the number of cases began to fall, BA.2 began to spread fast in Denmark. After only a few weeks, BA.2 took over the outbreak in Denmark, extending the outbreak's duration. The number of infections in Denmark is increasing rapidly, with more than 40,000 cases reported per day. According to the Statens Serum Institute in Copenhagen, BA.2 has been responsible for over half of those cases since the second week of January.

Omicron BA.2 is also spreading rapidly in England and Germany, responsible for at least 5% of cases in both countries. Scientists are afraid that it may extend surges in those areas and the United States.

This fact indicates that BA.2 is not the weaker sibling of BA.1; BA. 2 is quite powerful and may be more contagious.

Is BA.2 more dangerous than BA.1?

Compared to the delta version of the coronavirus, many studies have shown that infections with omicron BA.1 entail a lower risk of severe disease.

According to Dr Peter Chin-Hong of the University of California San Francisco, preliminary research from Denmark suggests that this will also be the case with omicron BA.2.

"Scientists there discovered that having BA.2 had no greater risk of going to the hospital compared to having BA.1," Chin-Hong explains. "Things could change, but for now, that's what we know."

In addition, there is cautious optimism about vaccines. According to preliminary data from the UK government, a third dose of the COVID-19 vaccine protects against BA.2 infection just as well as BA.1. In both cases, it lowers the chances of asymptomatic infection by roughly 60% to 70%. Furthermore, the spike proteins of BA.1 and BA.2 – the part of the virus that many antibodies target — are remarkably similar.

As a result, Chin-Hong believes the vaccines will provide excellent protection against severe disease.

"I can't guarantee you won't get infected or reinfected [if you've already had COVID-19], which means you might have the sniffles or think you have another cold, but I'm extremely confident you'll be protected. Against serious disease in the general population."

This distinction, according to Chin-Hong, is essential for COVID-19's future. Communities must shift their attention from preventing all infections to keeping everyone safe from severe disease and hospitalization in the future, he says.

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