New COVID variant XEC now in half of states. Here’s what to know.

COVID-19 variant trackers are now closely watching the rise of a new virus variant called XEC, which has been spotted around the world and in half of states across the United States.
Health officials are so far not raising concern about this variant, unlike some previous, more highly mutated strains that worried experts. 
XEC’s emergence comes as COVID-19 trends remain “high” but are now largely slowing after a summer wave of infections that peaked last month. Centers for Disease Control and Prevention modelers estimate that the virus will likely climb again over the winter, peaking in mid-January.
Here’s the latest we know about the new XEC variant.
At least 25 states have already reported at least one case with the strain’s characteristic mutations, according to preliminary data obtained from the global virus database GISAID from more than 100 cases in the U.S.
Labs in New Jersey have reported the most XEC infections – at least 15 – of any state. Only California and Virginia have also reported at least 10 cases so far.
New Jersey’s detections come in large part from samples collected through the CDC’s testing program of arriving travelers clearing customs at Newark Liberty International Airport.
Some of the earliest U.S. cases were reported by scientists at a lab in Virginia Tech’s Fralin Biomedical Research Institute, sampled from patients in July.
“We do not see a particular trend. We should keep an eye on the samples coming and continue genomic screening more broadly,” said Carla Finkielstein, head of the institute’s molecular diagnostics lab, in an email.
Finkielstein said that the majority of their samples come from hospitals across the southwestern part of Virginia, though it is unclear why exactly they were tested.
“Unfortunately, we do not have demographic data on these patients, so we don’t know whether the patients were hospitalized or, for example, if their samples were collected during an emergency department visit,” Finkielstein said.
Variant trackers first proposed labeling the new strain as XEC in early August, after infections were reported around the same time from labs both in Europe and Virginia.
XEC’s growth in recent weeks across Germany, flagged by variant trackers like Australian consultant Mike Honey on X, has driven recent attention online to the variant’s ascent.
But others in the variant tracking community have been skeptical that the strain will outcompete other strains on the rise, especially since a closely related strain called KP.3.1.1 has already reached dominance in many countries.
KP.3.1.1 now makes up more than half of cases in the U.S., according to CDC estimates published last Friday, and has been dominant for several weeks.
If XEC grows to dominance, it could mark just the latest in months of variants that have led to relatively smaller shifts in the threat posed by circulating variants.
This is in contrast to the discovery of the highly mutated BA.2.86 variant that worried health authorities around this time last year, because it had accumulated a concerning number of genetic changes compared to earlier strains. 
A descendant of that BA.2.86 strain from last year, which was eventually dubbed JN.1, later rose to dominate last winter’s wave of infections.
The “X” in XEC’s name comes from the fact that the strain looks to be a “recombinant” of two other closely related parent variants called KS.1.1 and KP.3.3. Both KS.1.1 and KP.3.3 are descendants of the JN.1 strain.
“CDC is not aware of any specific symptoms associated with XEC or any other co-circulating SARS-CoV-2 lineage,” a spokesperson for the agency said in a statement.
Americans are still recommended to get this fall and winter’s round of updated COVID-19 vaccines, the CDC spokesperson said. Those shots were greenlighted last month with an update to target the KP.2 strain of the virus.
The Food and Drug Administration has defended its pick of KP.2 for this year’s revised vaccines in recent weeks, which overrode a recommendation from the World Health Organization and a panel of the agency’s outside advisers to target its parent JN.1 instead. 
The FDA said in a statement Wednesday that the agency was “highly confident” in the effectiveness of this season’s updated shots. 
How FDA officials think XEC will impact their pick is unclear. An FDA spokesperson did not immediately respond to a request for comment.
“At this time, we anticipate that COVID-19 treatments and vaccines will continue to work against all circulating variants. CDC will continue to monitor the effectiveness of treatment and vaccines against circulating variants,” the CDC spokesperson said.