‘Stealth Omicron’ Starting to Get Noticed, Setting Off Some Alarms


Initial data suggest that it appears to be more infectious than even the highly infectious original Omicron variant.

“Something is rotten in the state of Denmark,” but it has nothing to do with Machiavellian political machinations that the quote alludes to in Shakespeare’s Hamlet. The rottenness this time around has to do with the activity of what some experts refer to as the “stealth Omicron”—BA.2—that appears to be much more infectious than even the highly infectious Omicron—or BA.1.

The Statens Serum Institut, a Danish research institute dedicated to fighting infectious diseases, said in a press release that “the subvariant BA.2 accounted for 20% of all COVID-19-cases in Denmark in week 52 increasing to approximately 45% in week 2. During the same period, the relative frequency of BA.1 has dropped.”

The Statens Serum Institut notes that the strain seems to be spreading in other countries, notably the United Kingdom, Sweden, and Norway. But the spread in those countries at the moment appears much less intense than what’s going on in Denmark.

Not so slow, however, that the health officials in those counties aren’t concerned. The U.K. Health Security Agency just today updated its list “SARS-CoV-2 Variants of Concern and Variants Under Investigation in England” to include stealth Omicron. “Omicron also contains the clade BA.2,” the Agency states. “This is being separately monitored and assessed from a technical perspective and is included in overall Omicron case counts.” The Agency states that it has confirmed 426 cases of stealth Omicron in the UK.

Meanwhile, the World Health Organization (WHO) says that it has identified over 8000 cases of stealth Omicron in more than 40 countries including the US.

Statens Serum Institute also states that “initial analysis shows no differences in hospitalizations for BA.2 compared to BA.1. Analyses regarding infectiousness and vaccine efficiency etc. are ongoing, including attempts to cultivate BA.2 in order to perform antibody neutralization studies. It is expected that vaccines also have an effect against severe illness upon BA.2 infection.”

So, just how much of a threat does stealth Omicron pose?

Like almost everything else about COVID-19, it depends on which expert you ask, although all experts at this point say that it’s too early to tell what stealth Omicron might be up to.

Vipin M.Vashishtha, MD, who serves on the advisory committee on vaccine and immunization practices at the Indian Academy of Pediatrics, Tweeted that the BA.2 version of Omicron may have 28 unique mutations compared to BA.1, even as the two Omicron strains share 32 mutations.

Statens Serum Institut states that “such differences can lead to different properties for instance concerning infectiousness, vaccine efficiency or severity. So far, there is no information as to whether BA.1 and BA.2 have different properties….”

Fortune magazine reports that some scientists … well, the Fortune headline sort of says it all: “What Is ‘Stealth Omicron’? The Rise of the Subvariant Is Alarming Some Scientists Who Say It Needs Its Own Greek Letter.”

The article states that “some researchers believe that BA.2 is so distinct from Omicron’s original strain that the World Health Organization should label it a variant of concern—reserved for variants that demonstrate increased transmissibility, among other factors—and give it its own name.”

One of those researchers is Shay Fleishon, PhD, who’s affiliated with the Israeli government’s Central Virology Laboratory, and who Tweeted that “I think the responsible thing to do is to relate to BA.2 as a completely different variant, outcompeting BA.1. Oh and if someone in the WHO is here—the letter Pi is still waiting. Just saying.”

Kevin Kavanagh, MD, a member of Infection Control Today®’s Editorial Advisory Board, agrees. “With the large number of new mutations, I feel BA.2 should be viewed as a new variant,” says Kavanagh. “The variant appears to outcompete Omicron.”

Even if individuals infected with stealth Omicron turns out to have only “mild COVID-19”—a term Kavanagh has argued is a misnomer—if it nonetheless also turns out to be more infectious than original Omicron, that will cause even more disruptions to medical supply chains and add more burden to already overstressed health care systems.

“I feel we can all agree that the speed with which these new variants are developing is causing unsustainable stress on our society,” says Kavanagh. “We need to all implement public health strategies to slow down spread, which will also slow down the emergence of additional variants.”

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