A new COVID variant called the "stealth omicron" is being monitored by scientists and health experts around the world, and has now been detected in Illinois and Wisconsin, NBC Chicago reported.
According to officials at Northwestern University, the first case of the BA.2 omicron subvariant was detected in Illinois on Jan. 31. The case was discovered by Northwestern Medicine's Center for Pathogen Genomics and Microbial Evolution.
This version is widely considered stealthier than the original version of omicron because particular genetic traits make it somewhat harder to detect on PCR tests.
The World Health Organization classifies omicron overall as a variant of concern, but it does not give BA.2 a designation of its own.
"There's nothing that we've seen at this point that is raising a high level of concern but please rest assured we're watching it and we'll let you know if there's anything to be interested or concerned about," Chicago Department of Public Health Commissioner Dr. Allison Arwady said.
Doctors advise the same precautions they have all along: Get vaccinated and follow public health guidance about wearing masks, avoiding crowds and staying home when sick.