BA.2, known better under the moniker ‘stealth Omicron’, is a new Covid-19 sub-variant currently ‘under investigation’ by the UK Health Security Agency (UKHSA).
The variant was identified in the UK in January and has since spread across the country – with over 1,000 confirmed cases in England alone so far.
The variant has been reported in 40 countries, with Denmark seeing the most significant rise in BA.2 cases.
Here is all you need to know about the new variant.
What is the stealth Omicron variant?
BA.2 is a sub-lineage of the original Omicron – BA.1 – but appears to have certain differences that may make it both faster at spreading and harder to detect.
BA.2 shows positive for the S-gene (the largest of the four major structural proteins found in coronaviruses, sometimes called the spike gene) while BA.1 does not. The fact BA.1 lacked the S-gene was key to detecting and tracking the spread of Omicron early on, as it distinguished it from Delta.
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It’s not clear where BA.2 emerged from, though the first cases were recorded in the Philippines.
Tom Peacock, a virologist from the Imperial College of London said there may be some evidence it is spreading faster – but more research is needed.
He tweeted: ‘BA.2 appears to be the major Omicron lineage in (part of) India and the Philippines and there is evidence it is growing compared to BA.1 in Denmark, the UK and Germany.
‘Consistent growth across multiple countries is evidence BA.2 may be some degree more transmissible than BA.1. This is the main reason BA.2 is currently in the news.’
What are the symptoms of the stealth Omicron Covid variant?
Currently, no new symptoms have been identified.
As the new variant is a sub-lineage of Omicron, it can therefore be expected that similar Omicron symptoms could present.
These include:
- Fatigue
- Night sweats
- Scratchy throat
- Dry cough
- Mild muscle aches
In data published by the UKHSA on January 14, they found that NHS test and trace data revealed a loss of smell or taste was reported less often by Omicron cases than Delta cases (13% of Omicron cases, 34% of Delta cases).
However, officials at the World Health Organisation (WHO) assured that BA.2 symptoms are just as mild as the original version.
‘Looking at other countries where BA.2 is now overtaking, we’re not seeing any higher bumps in hospitalization than expected,’ Dr Boris Pavlin, a member of the WHO’s Covid-19 Response Team, said during a briefing.
‘Vaccination is profoundly protective against severe disease, including for Omicron. BA.2 is rapidly replacing BA.1. Its impact is unlikely to be substantial, although more data are needed.’
Why is it called the stealth Omicron variant?
BA.2 has many shared characteristics of the original Omicron – BA.1 – but the new variant gets its stealth nickname from one of its key differences.
Omicron was relatively easy to track because of a specific trait – the deletion of a spike gene. This made it stand out on PCR tests without the need for extra genome sequencing.
But the new stealth Omicron strain does not appear to have this, making it more difficult to monitor.
It means that while PCR tests will still spot if someone has this version of Covid-19, the samples would need to be sent for further lab analysis to determine if someone had stealth Omicron.
Is stealth Omicron more transmissible than normal Omicron?
Although it is too early to know for certain, early reports indicate that BA.2 is even more infectious than the already extremely contagious BA.1 Omicron.
In England, a preliminary analysis of contact tracing from December 27 to January 11 by the UK Health Security Agency (UKHSA) suggests that household transmission is higher among contacts of people infected with BA.2 – the new variant has a household transmission rate of 13.4%, compared with 10.3% for normal Omicron cases.
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