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How Is Stealth Omicron Different From Its Original Version?

Medically reviewed by Regina Victoria Boyles, MD · Pediatrics

Written by Lorraine Bunag, R.N. · Updated Mar 25, 2023

How Is Stealth Omicron Different From Its Original Version?

In early 2022, the Department of Health confirmed that the Philippines already had cases of the “stealth” Omicron variant. What do we need to know about this sub-lineage and will this development affect our efforts to end the pandemic? Find out here. 

Why the Variant Is Dubbed “Stealth” Omicron

Before we discuss its possible effects, let’s first talk about why the experts call it the “stealthy” version of Omicron. 

Omicron was first detected in November of 2021 in South Africa. Upon its discovery, experts announced that this COVID-19 variant has numerous mutations, which means it might be more transmissible and better at “escaping” immunity. 

Note that when Omicron first surfaced, people were most afraid of the Delta variant, which the World Health Organization said was the “fastest and fittest” variant. 

To identify if a patient has Delta or Omicron (or any other variant), experts need to do genomic sequencing. 

Genomic sequencing looks for features that uniquely represent the variant. For instance, experts can quickly identify the original Omicron (BA.1) due to its “S gene target failure.” 

“Stealth” Omicron or BA.2 doesn’t have this specific genetic feature. 

Does That Mean We Cannot Identify Stealth Omicron at All?

BA.2 may not have S gene target failure, but health officials say we can still detect it. The technicians in the laboratory may just need more time to identify it.

Being stealthy also doesn’t mean that PCR tests give false-negative results. If you have a stealth Omicron infection, standard COVID-19 testing will still give you positive results. 

Where Has BA.2 Spread?

We may only be hearing more about stealth Omicron now, but reports say dozens of countries have already detected it back in November 2021 — around the same time the original Omicron variant was discovered. By January 2022, it had spread to 49 countries. 

In the United States then, numbers remained low. But the cases were higher in Europe and Asia. In fact, stealth Omicron appears to have gained ground in Sweden, Denmark, the United Kingdom, and India then.

A DOH official also stated that stealth Omicron became more common in local cases in our regions. 

Should We Be Worried?

Besides the missing genetic quirk, reports say stealth Omicron also had 28 mutations identified then, that were different from the original Omicron. This is why some people previously called for the authorities to declare BA.2 as a variant of its own. However, authorities still saw no significant difference between the clinical presentations. 

In Denmark, which had many cases of BA.2, researchers noted that there’s no difference in the number of cases that require hospitalization. Based on the data then, patients infected with stealth Omicron don’t appear to require hospital confinement more than patients infected with BA.1. 

We still don’t know if stealth Omicron is even more transmissible than its original version. But judging by its spread in multiple countries, experts say the possibility is there. 

What Happens Next

Because we still lack data on BA.2, the World Health Organization encouraged public health officials to monitor the new sub-lineage independently and comparatively to BA.1. They said officials should prioritize assessing stealth Omicron’s ability to escape immunity and cause disease. 

Key Takeaways

The Department of Health confirmed in January 2022 that stealth Omicron is already in the country and that it was prevalent in local cases in the regions. 
Stealth Omicron or BA.2 is a sub-lineage of the original Omicron, BA.1. Its stealthy feature comes from the absence of “S gene target failure,” a characteristic that makes it easier for experts to identify the original Omicron variant. 
As of this moment, they don’t see a significant difference between the clinical presentations of BA.1 and BA.2. Still, the World Health Organization calls for public health officials to closely monitor the sub-variant. 

More on Health News here


Hello Health Group does not provide medical advice, diagnosis or treatment.

Medically reviewed by

Regina Victoria Boyles, MD


Written by Lorraine Bunag, R.N. · Updated Mar 25, 2023

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