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Stealth Omicron (BA.2 Variant)

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Stealth Omicron (BA.2 Variant)

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Stealth Omicron is a recently discovered sub-variant of the highly contagious Omicron coronavirus strain. Read the article below to get more information about this variant.

Written by

Dr. Sowmiya D

Medically reviewed by

Dr. N. Ashok Viswanath

Published At February 4, 2022
Reviewed AtAugust 23, 2023

What Is the Stealth Omicron Variant and Why Is It a Sub-Variant?

The WHO director-general has declared that it is premature for any country to surrender or claim victory against this COVID battle. The virus that causes COVID-19 is constantly evolving, and new variants of the virus emerge. WHO is now tracking four sub-lineages of the Omicron-variant, including BA.2. Some variants disappear, whereas others persist and cause more severe infections.

There are many variants that cause COVID-19 that are being tracked globally during this pandemic. Some of them have changes in their physical traits or changes in their genes. This can change the ability of viruses to resist the treatment or their ability to spread.

A lineage or sub-variant is a genetically closely related group of virus variants, and it is not very different from its original variants like Omicron. Omicron is an umbrella term for some closely related lineages of the SARS-CoV-2 Coronavirus, the most common of which is the BA.1 lineage. The Omicron variant has three sub-lineages which are B.1.1.529 OR BA.1, BA.2, and BA.3.

BA.2 is called a ‘stealth’ (one that is difficult to detect) variant. Omicron misses a target gene, which is integral in testing the variant with COVID PCR test kits. However, this is not the case with BA.2. BA.2 has the ‘S’ gene, missing in the original Omicron variant. This makes it difficult to track and confirm whether it is BA.2 or another variant. It does not mean that we cannot diagnose BA.2 with PCR tests. When someone tests positive for SARS-CoV-2, it will take longer to know which variant is responsible for the infection through genome sequencing. This had been the case with previous delta variants also.

What Are the Variants of Concern?

A variant of interest is one in which the changes in the genetic code are thought to have the potential to make the virus more harmful, and there is significant transmission in many countries.

Suppose this variant of interest is proven to be more infectious and escape protection from vaccination or previous infection and have an impact on the testing for the disease or treatment. In that case, it is labeled a “variant of concern.”

WHO has classified this Omicron as a variant of concern because of its potential to cause higher re-infection rates, increased transmissibility, and reduced protection from vaccines.

BA.2 is not yet described as a variant of interest or concern according to WHO, but it is being closely watched. It is a variant under investigation. Although the new sub-variant is said to be mild, the fact that it separates them is the ability to avoid detection.

Where Is BA.2 Spreading?

WHO says that the BA.2 sub-variant has been detected in 57 countries, and it is more infectious than its original sub-lineage. Stealth Omicron was first identified in South Africa in early December 2021. But now, it has begun to replace the more common original BA.1 version in countries like Denmark. According to a Danish study, they are estimated to be 1.5 times more transmissible than BA.1 but are less severe. The original BA.2 sub-variant accounts for more than 98% of Omicron cases worldwide, but the sub-variant BA.2 is already becoming dominant in countries like the Philippines, Nepal, Qatar, India, and Denmark. We need people to be more aware that this virus is continuing to circulate, continuing to evolve.

What Are the Symptoms of This Sub-variant?

There is not much evidence to tell if the new sub-variant is different from the original Omicron variant in terms of symptoms. It is believed that BA.2 also causes mild symptoms such as,

  • Runny nose.

  • Scratchy throat.

  • Headache.

  • Fatigue or tiredness.

  • Sneezing.

  • Body ache.

  • Night sweats.

  • Loss of appetite.

  • Vomiting.

Is BA.2 More Transmissible Than the Other Strains?

The exact properties of BA.2 are still under study. The primary threat posed by Omicron and its variants mainly depend on the following:

  1. How fast is the variant transmissible?

  2. How well do the vaccines or previous infection protect the infection and its transmission?

  3. How virulent is the variant when compared to others?

  4. How does the population understand this information and perceive them to follow control measures?

With such high transmission levels, the virus has abundant opportunities to reproduce and for errors and mutations. According to a Danish study, prior infection with BA.1 does not protect against BA.2.

How Severe Is the BA.2 Variant?

According to the laboratory studies issued by a team of Japanese scientists, the BA.2 variant, also called the stealth variant, can bring about serious diseases just like its previous counterpart, the Delta variant. However, this report has not yet been peer-reviewed.

There are three main factors that make the stealth variant a variant of concern:

  • The BA.2 variant has a capacity of producing increased disease severity.

  • It has similar immune escape properties like BA.1.

  • Treatment with monoclonal antibodies like Sotrovimab is ineffective against the stealth variant.

BA.2 variant is of concern because it has a capacity to show high rates of transmission and also to cause severe disease. Also, it has been estimated that a new wave, if it occurs with the Omicron variant, BA.2 variant, would be responsible for almost 98% of infections.

Although several pieces of research and reports about the severity of the stealth variant, according to the United Nations Organization and the Center for Disease Control and Prevention, BA.1 and BA.2 variants do not differ much in severity.

How to Get Protected From BA.2 Sub-variant?

Dr. Boris Pavlin of the World Health Organization has said that the vaccines will continue to provide similar protection against different forms of Omicron. WHO has suggested the following:

  • Enhance surveillance and sequencing efforts to understand the virus and its variants better.

  • Submit a complete genome sequence and associated information to publicly available databases such as GISAID.

  • Report cases associated with variation of concern to WHO.

What Are the Preventive Measures for BA.2 Sub-Variant?

Individuals are also reminded to take preventive measures that reduce their risk of COVID-19, which includes-

  • Wearing protective and well-fitted masks in public places.

  • Practicing good hand hygiene.

  • Physical distancing.

  • Avoiding crowded places.

  • Improving the ventilation of indoor spaces.

  • Getting vaccinated for COVID-19 can lower the risk of disease and spreading the virus.


The good news is that vaccines and boosters can still keep people out of the hospital or reduce the risk of life-threatening complications. We must remain observant and take up vaccinations. We are likely to see new variants, sub-variants, and lineages in the future. We must continue to follow all the protocols; test if symptoms develop and self-isolate ourselves.

Frequently Asked Questions


Does Vaccine Protect Us From Omicron?

WHO (world health organization) says that vaccines will continue to provide similar protection against different forms of Omicron. They protect against infection and hospitalization. Currently, research studies say that vaccines offer 30 to 40 percent protection against disease and around 70 percent protection against hospitalization without boosters.


What Is the Severity of the Omicron Variant When Compared to the Delta Variant?

Omicron appears to be less severe than the Delta variant, especially in those vaccinated. But, this cannot be categorized as mild because severe cases are reported also.


Can New Variants Emerge After Omicron?

Viruses keep evolving until they do not have any hosts to infect. Worldwide, many people are yet to be vaccinated, which means the Omicron is not the end. Newer viruses can emerge in the future too.


What Is the Mode of Transmission of the Omicron Variant?

Omicron spreads from the respiratory droplets of the mouth and nose at close range. It can also spread in areas of poor ventilation where the virus particles float in the air and stay suspended for quite some time.


Is BA.2 Sub-Variant Worse Than Omicron?

BA.2 subvariant is more transmissible, but the severity is less than the BA.1 sub-variant of the Omicron, which is the original version. According to Danish health officials, BA.2 maybe 1.5 times more transmissible than BA.1.


What Is the Incubation Period for the Omicron Variant?

The Omicron variant spreads faster than the original virus that causes COVID-19 and the Delta variant. The presence and severity of symptoms may vary depending on the COVID-19 vaccination status, the presence of other health conditions, age, and history of prior infection.


What Are the Symptoms of the Omicron Variant of COVID-19?

Omicron variant also seems to present with symptoms similar to previous variants such as:
- Runny nose.
- Scratchy throat.
- Headache.
- Fatigue or tiredness.
- Sneezing.
- Body ache.
- Night sweats.
- Loss of appetite.
- Vomiting.


Which Are the Organs Most Affected by the Omicron Variant of COVID-19?

WHO reported that the Omicron variant of Coronavirus affects the upper respiratory tract, causing milder symptoms than previous variants.


What Are the Complications of the Omicron Variant of COVID-19?

Omicron is most commonly causing an infection in the upper respiratory tract, but it also causes lung damage in the elderly and those with co-morbidities. The re-infection rates of previously infected individuals of COVID-19 are also higher when compared to other variants.


What Are Some Uncommon Symptoms of the Omicron Variant?

Sore throat, headache, body ache, pain, diarrhea, a rash on the skin, irritated eyes, and discoloration of the fingers are uncommon symptoms of the Omicron variant.
Dr. N. Ashok Viswanath
Dr. N. Ashok Viswanath

Infectious Diseases


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