A new Covid-19 strain, nicknamed “stealth Omicron ”, is being officially monitored by UK health officials.

Early data shows that it is more contagious than the original Omicron strain.

However, according to a Mirror report, initial studies have not shown a difference in the risk of hospitalisation.

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Known as the BA.2, the sub-variant is believed to have emerged from a mutation of the Omicron variant.

It may be both more transmissible and better able to evade vaccines than the more common BA.1 sub-lineage.

Data says the BA.1 lineage accounts for 98 per cent of all cases globally but in Denmark, the BA.2 has grown rapidly.

In Denmark in the last week of 2021, it accounted for 20 per cent of all positive cases.

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But, by the second week of 2022, it accounted for 45 per cent of cases.

Such is the rise that yesterday (January 26) it was reported that BA.2 had become the dominant strain in Denmark.

Danish Health Minister Magnus Heunicke said, when addressing the nation: "There is no evidence that the BA.2 variant causes more disease, but it must be more contagious."

Statens Serum Institut, Denmark's top infectious disease authority, have shown calculations that reveal that BA.2 could be 1.5 times more infectious than BA.1.

But this is, so far, not showing difference in the risk of hospitalisation for BA.2 compared to BA.1.

"There is some indication that it is more contagious, especially for the unvaccinated, but that it can also infect people who have been vaccinated to a greater extent," SSI's technical director Tyra Grove Krause at the briefing.

The new strain has been dubbed the “stealth Omicron” as it is poses a challenge for scientists to track, unlike the original Omicron that stood out on the widely-used PCR tests without the need for extra genome sequencing.

It shows up as being S-gene positive under PCR tests, whereas the BA.1 did not.

The World Health Organisation, has said that BA.2 sequences have been reported in more than 40 countries, including the UK, Sweden, Norway, Singapore and India.

Under investigation

The UK Health Security Agency last Friday designated BA.2 a “variant under investigation” – one level below a “variant of concern” – saying it could have a growth advantage.

Dr Meera Chand, incident director at the UKHSA, explained: "It is the nature of viruses to evolve and mutate, so it's to be expected that we will continue to see new variants emerge,"

"Our continued genomic surveillance allows us to detect them and assess whether they are significant.

"So far, there is insufficient evidence to determine whether BA.2 causes more severe illness than omicron BA.1, but data is limited and UKHSA continues to investigate.”

According to Reuters, there have been 426 cases of the BA.2 sub-lineage have been sequenced in the UK, and the UKHSA said early analysis suggested an increased growth rate compared to BA.1.

Tom Peacock, one of the first virologists to raise the alarm over Omicron, tweeted that "very early observations from India and Denmark suggest there is no dramatic difference in severity compared to BA.1. This data should become more solid (one way or another) in the coming weeks.”

He added that "there is likely to be minimal differences in vaccine effectiveness against BA.1 and BA.2. Personally, I'm not sure BA.2 is going to have a substantial impact on the current Omicron wave of the pandemic.

"Several countries are near, or even past the peak of BA.1 waves. I would be very surprised if BA.2 caused a second wave at this point. Even with slightly higher transmissibility this absolutely is not a Delta-Omicron change and instead is likely to be slower and more subtle," he continued.

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