The COVID-19 variant XBB.1.5 is continuing to account for more and more new cases nationwide, and is now particularly dominant in the Northeast, including New York City. The NYC Department of Health and Mental Hygiene noted Friday that based on the latest sequencing data, XBB.1.5, which numerous health agencies have described as the most transmissible COVID variant yet, made up 73 percent of all sequenced cases in the city as of December 31. Early last month, the DOHMH began once again advising New Yorkers to voluntarily mask up indoors amid the high circulation of flu, RSV, and COVID.
XBB.1.5, a recombinant Omicron subvariant which was first detected in New York this fall, is also on its way to becoming the dominant strain nationally. As of the week ending January 14, the CDC estimates that XBB.1.5 accounted for 43 percent of new U.S. cases, up from about 30 percent and 20 percent the preceding two weeks. The CDC also estimates that XBB.1.5 now makes up more than 80 percent of cases in the Northeast.
While the variant’s proportions are, for now, far lower in the rest of the country, some scientists believe it’s just a matter of time until XBB.1.5 becomes dominant nationally and globally. Also, because of the ever-declining amount of lab testing and sequencing being done of COVID cases, it’s impossible to know for sure just how many cases there are, regardless of which strain caused them.
What impact XBB.1.5 ultimately has in the U.S. and abroad remains to be seen. The best-estimate numbers of cases and COVID-19-linked deaths have been trending upward in the U.S., though at nowhere near the the same pace or levels seen in previous major waves. Regardless, XBB.1.5 may very well drive a new surge of some size.
Across the pandemic, the label “most transmissible” has long been a recurring superlative awarded to emergent strains that have evolved to more easily infect and spread. In XBB.1.5’s case, scientists have pointed to a mutation in the virus’s spike protein which may be enabling the variant to outcompete other strains. There isn’t evidence to suggest that XBB.1.5 is more virulent, and the WHO has noted that it does not carry mutations known to lead to more serious illness, but XBB.1.5 is apparently better able to get around antibodies than its predecessors.
With any surge of a new immune-evading COVID variant, the best defense against severe illness remains being fully vaccinated — which means getting the newest bivalent COVID boosters, the uptake of which has been markedly low across the U.S. That is particularly important for seniors, who remain woefully undervaccinated in the country, and remain, by far, the population both most at risk of and most adversely affected by COVID-19.