TheBA.2 subvariantof COVID-19 ’s Omicron line may be starting to make itself known within the United States , epidemiologist revere . Nevertheless , its spread has not followed the steep upward path there that it has in some other countries , nor that shown by the original Omicron ,

BA.2 is a form of Omicron – different enough to be deserving observe , but like enough it has n’t been founder its own letter . virologist sayit is more of a sibling to the original Omicron than a descendant , share a remote ancestor . It ’s now present inalmost every country . In some , such as Denmark and South Africa , it has outpaced other strain , conduct public health officials to brace for yet another wave of the computer virus .

In other lieu , however , its numbers have been small or conk entirely , but no one knows why .

" A lot of us were assume that it was going to quickly take off in the United States just like it was doing in Europe and become the new predominant variant,“Dr Nathan Grubaughof the Yale School of Public Health toldNPR .

First detected in the USA in other January and making up only 3.9 per centum of new infection in mid - Februaryaccording to the CDC , that has n’t happened . By contrast , Omicron ’s two earlier successful subvariants BA1.1 and BA1.1.529 went from a handful of cases to complete dominance in the space of December .

Nevertheless , that does n’t mean BA.2 is a non - threat , nor that America is somehow immune . After all , on the same CDC data point , the strain doubled between the week ending February 5 and February 12 . Another calendar month at that rate , and it could unleash yet another undulation on the continent ’s battered health care system .

The affirmative scene , expressed by Grubaugh as a chance but not a certainty , is that recent contagion with Omicron will bear witness protective against BA.2 . With so many hoi polloi in that category , the wave could fizzle out , despite its high transmissibility .

Somesee signsof this come about in Australia , where BA.2 contagion rates have been static for weeks . Others are more disquieted , orient to the dramatically high rate of spread line in apre - printdescribing BA.2 ’s appearance in Denmark .

Decisions both at the politics and item-by-item floor will playact a part . If BA.2 ’s cash advance has been delayed because the people most susceptible are wearing masks and avoiding crowded shoes , cocksureness could grant it to take off .

" There is this lurking terror of BA.2 . And we need to ensure this is n’t go to be a trouble before we wheel back all the mandates , before we state everybody that it ’s safe , " The Rockefeller Foundation’sDr Samuel ScarpinotoldNPR .

The spot with BA.2 is complicate by the fact it’sharder to differentiatefrom Omicron BA.1 than Omicron was from old variants . PCR screen canstill recognizethe so - called “ stealth wedge - variant ” , but take longer to do so , making progression harder to track .

Despite Omicron sometimes being presented asmild , it hasnow caused more deathsin the United States than the Delta undulation .