Stealth Omicron: What Is The Omicron BA.2 Sub Variant? Detection, Symptoms And Other Details

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According to the UK, a new sub-strain of the Omicron coronavirus has been identified in over 40 countries, and the virus can evade even RT-PCR testing. The BA.2 substrain, commonly referred to as the "Stealth Omicron", has given rise to fears of a stronger wave sweeping across Europe.

In November of last year, the BA.2 strain of Omicron was identified, but it has been rapidly spreading in recent weeks. In Denmark, where COVID-19 infections have increased rapidly, the situation is particularly dire.

Stealth Omicron: Everything You Need To Know

The World Health Organization states that there are three sub-strains of the Omicron variant: BA.1, BA.2, and BA.3. The BA.1 sub-strain dominates Omicron infections reported throughout the world, while the BA.2 sub-strain is said to be spreading rapidly. It has been found in a substantial fraction in India, where the COVID-19 peak is expected within the next two weeks [1].

In India, Omicron has now become dominant in multiple metros, where new cases have been increasing exponentially. Moreover, in India, BA.2 lineage constitutes a substantial population. Therefore, testing using S gene dropouts would probably result in a high number of false negatives, according to INSACOG [2].

• Transmissibility: It is likely that BA.2 is more transmissible than BA.1, as evidenced by consistent growth across multiple countries.

• Virulence: India and Denmark have reported very early observations that suggest no significant difference in severity between BA.1 and BA.2.

• Immune evasion: Very small differences in VE antibodies. BA.1 and BA.2 infections are highly likely to have decent cross-reactivity with BA.2 infections, as well.

• Antigenicity: As compared to BA.1, Spike RBD mutations are likely to have relatively little effect on antigenicity.

Why Is It Called The 'Stealth Omicron'?

Upon discovering the Omicron variant, researchers noted that its original strain - the BA.1 - suffers from a mutation that manifests itself as a deletion in the "S" or spike gene, which was detected using PCR tests [3]. However, the BA.2 sub-strain does not possess the same mutation for which it has been dubbed "Stealth Omicron".

What Countries Have Detected Cases Of 'Stealth Omicron'?

In addition to the UK and Denmark, cases of the BA.2 sub-strain have been detected in Sweden, Norway, and India. The sub-strain has also caused concern among researchers in India and France who fear it might outpace the BA.1 sub-strain. As of 10 January, the UK had identified 53 sequences of the BA.2 sub-lineage, with the latest figures due to be released later this week [4].

Is 'Stealth Omicron' A Cause For Concern?

Researchers claim that despite sharing 32 strains with BA.1, Fortune reported that BA.2 might contain more than 28 unique mutations. In addition, researchers have discovered that BA.1, which has a mutation - the deletion in the "S" or spike gene - can be detected using PCR, making the diagnosis of Omicron relatively straightforward. The BA.2 strain, on the other hand, does not have the same mutation that makes it difficult to detect [5].

Are PCR Tests Ineffective Against 'Stealth Omicron'?

The BA.1 sub-strain may escape RT-PCR tests occasionally, but experts maintain that these tests remain the gold standard for detecting the virus. The lab RT-PCR test is the gold standard test, and with this test, there is no difference in the sensitivity of pick-up rates between Omicron and the previous Delta [6]. In the Omicron variant, over 30 mutations in the spike protein do not affect the sensitivity of the currently available testing kits.

Disclaimer: The information provided in this article is for general informational and educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or a qualified healthcare provider with any questions you may have regarding a medical condition.