Tuesday, February 7

How is the “stealth” variant of omicron, which worries the WHO and eludes antigen tests?

According to the latest data from Ministry of Health, the omicron variant has displaced delta, which has come to have an almost residual prevalence in Spain, with a representation of less than 10%.

Now Ómicron is responsible for between 79.6 and 98.7% of the infections that are being registered in our country, and the Valencian Community is the only Spanish region where this strain has a representation below 80%.

In contrast, four autonomous communities are close to 100%: Community of Madrid, Cantabria, Extremadura and Galicia.

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The new variant can evade the antigen tests of pharmacies

While ómicron continues unstoppable – in the last 24 hours there have been 27,249 positives and 253 deaths – a new subtype of this strain has appeared: BA.2 u also known by experts as “stealth omicron”.

This new subvariant of omicron has been sequenced in countries such as Denmark, United Kingdom, Sweden, China, Canada e India, where it is believed that the first cases occurred.

The World Health Organization has baptized this new variant as “stealth” for its ability to evade common detection methods Like the antigen test that are purchased at pharmacies.

And only in Denmark, according to the Pasteur Institute, already represents half of the infections that are currently being registered.

Such is the concern that the WHO has recommended putting the accent on research into the BA.2 version of omicron, which is gaining ground in the world.

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“It differs from the first in some mutations, including the spike protein,” explains the agency.

Where has BA.2 emerged?

Although the first cases of this omicron subvariant were detected in China, experts believe that its origin is in India.

Does it stream faster?

It is still early to know the transmissibility of the new variant, but the first investigations indicate that what is is more difficult to detect by current tests to identify mutations.

It would also be difficult in tests such as antigen tests, which would cause many false negatives.

It should be noted that, according to the data provided by the different countries where it has already been detected, most cases of BA.2 are asymptomatic or with mild symptoms.

In addition to the territories mentioned above, this strain is already present in other areas such as Sweden, Noriega, Greece, the Philippines, the United States and the United Kingdom.

In the latter, the Health Security Agency (UKHSA) is carrying out analyzes to find out the prevalence of stealthy omicron in the country, where, although there are still few registered cases, they are increasing rapidly.

BA.2 has been designated VUI: Variant Under Investigation.

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Is it more virulent?

To answer this question, we must go to Denmark, where the number of infections by BA.2 has grown exponentially since the first weeks of January.

If at the beginning of the year the subvariant only represented 20% of the infections detected, in this last week it already represents 50%.

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Different Fomsgaard, a researcher at the Statens Serum Institut (ISS), a research institute located on Copenhagen’s Amager Island, says he is “confused” about this strain, but not “concerned.”

The reason is that the first studies carried out in this center indicate that there are no differences in hospitalizations between the omicron variant (BA.1) and the stealthy omicron variant (BA.2).

“It is a possibility” that people infected with BA.1 can be reinfected with BA.2, so, he points out, we must be on alert.

«We must be prepared for it. And then we could actually see two peaks of this epidemic.”

A second wave of this variant is not expected

However the Dr. Tom Peacock, a virologist at Imperial College London in the United Kingdom, one of the first to raise the alarm about omicron, believes that BA.2 will not cause a second wave of this variant.

“I would be surprised if BA.2 caused a second wave, even with slightly higher transmissibility,” he wrote on his Twitter account.

On the effectiveness of the vaccines against the new subtype, Peacok is clear: “It is likely that there will be minimal differences in the effectiveness of the vaccine against BA.1 and BA.2.”

However, he believes that the new variant will displace omicron “in the coming months with an ‘optimized’ mutational profile”.


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