Credit CDC Nowcast
#16,555
Although we've known that the BA.2 Omicron variant has been in the United States for several weeks, today's updated CDC Nowcast is the first time we've seen an estimate of its prevalence, which is estimated at roughly 3.6% for the week ending February 5th.
The revised Nowcast (below) has added estimated prevalence for the previous two weeks as well. The Original BA.1, once estimated to be 99.9% of all cases, had slipped slightly to 96.6%. Delta, meanwhile, is nowhere to be seen.
It takes a few weeks for new variants to begin showing up reliably in these Nowcasts. When BA.1 first appeared, we saw several weeks of `adjustments' made to previous week's estimates, and that seems likely to happen with BA.2 as well.
The important thing to watch is how quickly BA.2 gains ground, and whether BA.1 is able to compete with this newer variant. If things go here as they have in Denmark, then BA.2 is likely to become dominant in North America in a matter of weeks.
So far there is no evidence to suggest that BA.2 causes more severe illness than BA.1, although it does appear to have a transmission advantage (see Preprint: Transmission of SARS-CoV-2 Omicron VOC subvariants BA.1 and BA.2: Evidence from Danish Households).
ECDC Rapid Risk Assessment On COVID Omicron - 19th Update
UKHSA: Risk Assessment On Omicron BA.2 Subvariant
