In recent weeks, you might have heard about a ‘stealth’ version of the highly-contagious Omicron variant that has thrown Australia into the deep end, with huge case numbers and hospitals pushed to the brink.

A ‘stealth’ version of the Omicron monster that keeps wearing us down sounds terrifying. The reality is, scientists have more questions than answers. They’re not sounding too concerned, yet.

Certainly, most scientists don’t believe this stealth version is a more dangerous or difficult variant than Omicron.

Others are saying it could prolong the pandemic.

According to an early report from The Guardian in the UK, the Omicron sub-variant known as BA. 2 was “spotted among Covid virus genomes … from South Africa, Australia and Canada”.

Yes, Australia. That was in the first week of December.

Why haven’t we heard more about this?

Firstly, the Omicron variant (known as BA. 1) was first detected and reported November 24 and quickly began driving up case numbers.

The new variant was spotted about a week or so later.

It got lost in the rush as a massive surge in infections worldwide was accompanied by confusion as to whether, and then where and when, Omicron (BA. 1) overtook Delta as the dominant variant.

In other words, it’s been a crazy seven weeks

The reason why the ‘stealth’ variant is making news now: rapidly rising BA. 2 case numbers, and rapid global spread.

As the Australian Financial Review reported on Tuesday: “Denmark is posting fresh records for positive cases of COVID-19, notching up almost 40,000 a day in a country of 5.8 million people. More than half its cases are now the BA.2 sub-lineage of omicron, rather than the original BA.1.”

Meanwhile, the variant has been found “in small numbers” in the US.

This week, with 400-plus cases identified, the UK Health Security Agency (UKHSA) formally declared BA. 2 a “variant under investigation”.

On Monday, the World Health Organisation (WHO) advised that:

“The BA. 2 descendant lineage, which differs from BA. 1 in some of the mutations, including in the spike protein, is increasing in many countries.

“Investigations into the characteristics of BA.2, including immune escape properties and virulence, should be prioritised.”

So far, this makes the new variant a footnote, because not enough is yet known about BA. 2 for the WHO to declare it a “variant of concern” (VOC). If it does become a VOC, then it could get its own Greek name.

Why is it called a ‘stealth’ variant?

The word ‘stealth’ suggests the virus can go undetected in sick people. That’s not quite the case. As The Guardian reported:

“The variant is still detected as coronavirus by all the usual tests, and can be identified as the Omicron variant through genomic testing, but probable cases are not flagged up by routine PCR tests that give quicker results.”

This is because the variant “lacks a particular genetic change that allows lab-based PCR tests to be used as a rough and ready means of flagging up probable cases”.

This poses problems for epidemiologists and virologists more than patients. But given that Denmark has identified more than half of its presenting caseload as BA. 2 – meaning that it is now the dominant strain in Denmark –  the stealth aspect is limited.

On the other hand, as The Washington Post noted: the fact that BA. 2 “appears the most widespread in Denmark … may be because the Scandinavian nation has a robust program of sequencing the virus’s genome”.

Is it a more dangerous variant?

So far, scientists aren’t freaking out. Denmark is the place to watch how this variant might play out.

Professor Anders Fomsgaard, a virologist at the State Serum Institute in Denmark, told The Washington Post that BA. 2 “accounts for about 65 per cent of new cases as BA. 1 is on the decline”.

He said that his team haven’t seen so far “major differences in age distribution, vaccination status, breakthrough infections and risk of hospitalisation”.

He said that despite the high infection rate of BA. 2, “the numbers of hospitalisations [in] ICUs are decreasing”.

Professor Pam Vallely, a virologist at the University of Manchester, told Newsweek that she hadn’t yet seen any evidence to suggest that “BA. 2 causes more severe disease than BA.1”.

But she conceded: “We need a few weeks’ more data to analyse.”

Potentially even more infectious

Dr Wesley Long, a pathologist at Houston Methodist in Texas, told AP there were some indications that BA. 2 was “as contagious or perhaps slightly more contagious” than the original omicron.

What’s the evidence?

Dr Tom Peacock is a virologist at Imperial College London. In a series of tweets (@PeacockFlu) he said:

“Consistent growth across multiple countries … suggested BA. 2 may be some degree more transmissible than BA.1. This is the main reason BA. 2 is currently in the news.”

However, he also tweeted: “I would be very surprised if BA. 2 caused a second wave at this point.”

He said that even with slightly higher transmissibility “this absolutely is not” a Delta-Omicron change, which was rapid. He said that if BA. 2 becomes the dominant strain, it’s “likely to be slower and more subtle”.

Again, the important thing to watch is rate of hospitalisations. If they go up suddenly as BA. 2 gains dominance, we’re certainly in for some pain.

But that hasn’t happened yet in Denmark where BA. 2 rules. Fingers crossed, it won’t happen. We have enough on our plate as it is.