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While most prevalent in the Northeastern part of the country, XBB.1.5 continues to gain momentum across the nation, although the tag-team of BQ.1/BQ.1.1 still dominates in many regions.
The latest estimates in this week's CDC Nowcast put XBB.1.5 at just over 49% of all cases nationally.
In terms of gains and losses, only XBB.1.5 appears to be increasing its share, while other variants are either losing ground or remaining about the same as last week. Of all of its competitors, BQ.1.1 is showing the most resilience, giving away only 2% over last week's estimate.
The jury remains out on the relative severity of XBB.1.5 compared to earlier Omicron variants, but we have seen several new risk assessments over the past week, all of which characterize this variant as being among the most transmissible, and immune evasive, to date.
Preprint: Enhanced transmissibility, infectivity and immune resistance of the SARS-CoV-2 Omicron XBB.1.5 variant
ECDC Threat Assessment Brief (TAB) on Omicron XBB.1.5
No. XBB.1.5 Is Not More Likely To infect the Vaccinated (vs. Unvaccinated)
While XBB.1.5 appears to be a juggernaut here in the U.S., in the UK both CH.1.1 and XBB.1.5 in competition to see which will become the next dominant strain there, with the UKHSA reporting:
CH.1.1 and XBB.1.5 are currently the variants most likely to predominate in the UK following BQ.1, unless further novel variants arise. It is plausible that XBB.1.5 will cause an increase in incidence after the current wave, however it is currently too early to confirm this trajectory.
So far, CH.1.1 hasn't made enough of an impact in the United States to make the Nowcast list. But the same could have been said about XBB.1.5 a month ago.
The SAR-CoV-2 virus continues to evolve, and its rapid-replacement-cycle continues around the globe. While XBB.1.5 appears to be on track to dominate in the U.S. in short term, what we'll be dealing with 90 days from now is anyone's guess.
