The first case of the so-called "stealth" subvariant of omicron has been detected in Illinois by Northwestern Medicine's Center for Pathogen Genomics and Microbial Evolution. The center says the subvariant was found over the weekend from a Chicago resident who was tested for COVID-19 on Jan. 18.
"There are still very few cases reported in the USA, but this is the fastest-growing variant currently," said Dr. Ramon Lorenzo-Redondo, the bioinformatics director at CPGME. "It has become the most prevalent in several countries like Denmark and India, so we will see how it develops."
But doctors say the "stealth" moniker is a misnomer; the variant, dubbed BA.2, is actually very easy to detect.
"It's a misrepresentation of what this variant will be detected with," Dr. Ramon Lorenzo-Redondo told NBC 5. "This variant can be perfectly detected with tests. There are some tests that are used to distinguish between omicron and other variants, and it won't be distinguished, but still, it can be perfectly detected."
He said at this point, there is no reason to believe the new variant is any more dangerous than its omicron predecessor, and there have been no alarming signs where it has already been found. But it's likely there are more cases already in Illinois.
"As soon as one variant is spread globally it's going to be found in several places," Dr. Lorenzo-Redondo said. "And we have to remember that the Chicago airport is one of the most interconnected airports in the world. So it's very likely that if we have detected this, we will keep detecting some of this."
If the variant follows the same pattern in the U.S. as has been observed in other countries like Denmark and the United Kingdom, he said, Americans could expect a slowing of the current decline in new cases. But he noted it's actually too soon to make that prediction, because there are still relatively few BA.2 cases in the U.S.
Preliminary data indicate vaccinations and boosters are similarly effective in preventing symptomatic cases of BA.1, the original Omicron subvariant, and BA.2.
"For sure it's around," he said. "But how prevalent it's going to become, that's yet to be known."