The offspring of the omicron variant, known as omicron BA.2, or "stealth" omicron because it might be harder for tests to identify, has been confirmed in Wisconsin, according to Dr. Ben Weston, chief health policy advisor for Milwaukee County.
Weston tweeted Monday that it was detected "in Wisconsin," though he didn't specify where exactly the case was found.
At this point, the World Health Organization has not designated BA.2 a variant of concern. A study from the Statens Serum Institute in Denmark found that omicron BA.2 is 1.5 times more transmissible than the original omicron strain.
However, the University of Minnesota Center for Infectious Disease Research and Policy (CIDRAP) says that another study in Denmark found that while all people are susceptible to infection from BA.2 regardless of vaccination status, increased transmissibility is particularly higher in unvaccinated people compared to the original omicron strain.
As CIDRAP notes, the study "didn't find increased transmissibility from vaccinated or boosted people who had BA.2 breakthrough infections."
It's unclear if BA.2 is capable of causing more severe disease than the original omicron variant, known as BA.1, but health officials say that even though a person with natural or vaccine immunity can be infected with either omicron strain, vaccines are effective against symptomatic infection and reducing the risk of hospitalization and death.
On Friday, the Centers for Disease Control & Prevention said at least 127 cases of the omicron sub-variant had been confirmed in the U.S., though it was believed to be circulating at a low level, according to a report from CNBC.
The sub-variant has not been confirmed in any Minnesota residents, but last Thursday the Minnesota Department of Health Public Health Laboratory detected the BA.2 strain from a sample submitted from a Twin Cities testing site.
"The person from whom the sample was collected is not a Minnesota resident, and we have notified health officials in that person’s home state," MDH said.
It's also unknown if a person who previously was infected with the original omicron variant can be infected with omicron BA.2.