Can Omicron’s sub-variant, ‘BA.2’, also known as the ‘Stealth Variant’ evade RT-PCR testing?
A new coronavirus variant has been discovered, sparking concern amongst the scientific community. Omicron’s sub-variant BA.2 was first detected in Europe in late January and has since spread across the world, becoming the dominant strain of all new COVID-19 infections in at least 18 countries and counting – and it has also been found in every U.S. state.
Despite the fact that variant BA.2 is spreading at such a rapid rate, with one study in Japan stating that this strain spreads up to 30% more easily than the original Omicron variant, it has been dubbed ‘Stealth Omicron’.
It is titled as such due to the fact that it doesn’t show up on PCR-tests as an S-gene target failure, in the same way that Omicron does. Essentially, it lacks the omission of the spike gene, which is the contagious protein that is responsible for mutation.
In this way, PCR tests are not designed to detect this variant, although this is not to say that PCR tests do not show positive readings for coronavirus from Stealth Omicron.
Laboratory testing will still show a result for COVID-19, it is just that further genetic sequencing will need to be done to the sample, to determine whether or not this is the Stealth variant. So, although RT-PCR tests are considered the gold standard for detecting COVID-19 (with research showing that in laboratory settings the tested RT-PCRs achieved 100% sensitivity on positive samples, and more than 96% specificity on negative tests), when it comes to the ‘Stealth Variant’, this becomes much more difficult to name the variant, as it is not made up of the same protein spike deficiencies that a PCR test is capable of detecting.
Dr Wesley Long, a pathologist at Houston Methodist in Texas explains this best to the Associated Press, stating that, “It’s not that the test doesn’t detect it; it’s just that it doesn’t look like Omicron”.
However, it is important to note that although RT-PCR tests detect stealth Omicron as a subvariant strain of coronavirus, it is somewhat difficult to detect BA.2 through throat or nasal swabbing. This is because, unlike the coronavirus strains that we know, BA.2 infects the gut, and not the lungs, hence traces of coronavirus are not likely to be found in the mouth or nose for testing. That is why it is essential to look out for the signs and symptoms and to get tested and self-isolate, even if you come back with a negative result, to avoid putting others at risk.