#16,702
The rapid and ongoing evolution of Omicron is evident once again in this week's CDC Nowcast, which has added a 4th subvariant - BA.2.12.1 - to the existing (and original) B.1.1.529 Omicron (now < 1%), the rapidly eroding BA.1.1 variant (now at 6.1%), and the still dominant BA.2 (74.4%)
This new viral interloper wasn't even on our radar until last week's announcement by the State of New York (see NY State DOH Statement on Omicron Subvariants BA 2.12 and BA.2.12.1), which stated that BA.2.12.1 appeared to have a transmissibility advantage over BA.2 of as much as 27%..
As you can see by the map above, BA.2.12.1 is estimated to make up more than 50% of the new cases in the New York area, although its impact is still considerably less in other parts of the nation.
Based on backfilled estimates (see below), BA.2.12.1 does appear to be gaining ground faster than did BA.2, and is already estimated to account for 19% of cases nationwide. Impressive given that BA.2 only achieved dominance in late March.
Given the limits of surveillance, testing, and genomic sequencing around the country, all of these numbers should be viewed as rough estimates. They do, however, suggest that BA.2.12.1 could become dominant in the United States in the weeks and months ahead.
Assuming (as always) that something more biologically fit doesn't emerge in the meantime.
While we've been very lucky in that none of these Omicron variants has brought with it increased severity or mortality, it is concerning to see how quickly these new, `biologically fit' variants are emerging.
Instead of being measured in months - as we saw with Alpha and Delta - the dominance of the first two Omicron variants (B.1.1.529 & BA.1.1) has ended in a matter of weeks. And at the rate BA.2.12.1 is growing, BA.2 may not fare much better.
Unless and until COVID settles down, we need to be prepared for more surprises.
Stay tuned.
