4 Things We Know So Far About XEC, the Latest COVID Subvariant

A new subvariant of COVID-19 that has been spreading throughout Europe recently made its way into the United States, and experts believe it may drive another wave of infections in the coming months.

The XEC subvariant was first identified in Germany in June and has since spread to three continents and dozens of other countries, including the UK, Denmark, Poland, Ukraine, and now the United States. Eric Topol, MD, a board-certified cardiologist and the director of the Scripps Research Translational Institute, told the Los Angeles Times XEC is “just getting started.”

Dr. Topol took to X to offer his insight on the emerging variant, suggesting it “appears to be the most likely one to get legs next.” But with its presence in the U.S. hardly detectable right now, many questions about how it will actually affect infection rates remain.

Here’s we know about XEC so far:

1. It’s a subvariant of Omicron

Dr. Topol says XEC is a mix of established subvariants KS.1.1 and KP.3.3, both of which have been circulating for several months. KP.3.3 is closely related to KP.3, one of the FLiRT variants that has been responsible for the majority of COVID cases reported since early August.

All of these are subvariants of the Omicron variant, which was first detected in 2021 and has been the dominant coronavirus variant worldwide for several years now.

2. XEC appears to spread quickly

Since XEC was first identified in June, infections caused by the subvariant have increased rapidly throughout August and early September, indicating that the subvariant could be more contagious than others that have circulated recently. Last week, XEC cases increased 16 percent in Denmark and 17 percent in Germany. With the data being about one week behind and with schools now being back in full swing, it’s likely those figures will soon rise in the U.S. as well, Dr. Topol suggests.

Experts are estimating that XEC’s presence is growing at a quicker pace than JN.1—the variant that dominated last winter and spring and continues to show up in the Centers for Disease Control and Prevention (CDC)’s variant tracker. Although XEC has been detected in the U.S., it is not yet registering on the official tracker. According to Scripps COVID-19 epidemiology tracker Outbreak.info, 23 cases of XEC had been confirmed in the U.S. heading into Labor Day weekend. At least three of those were in California.

Currently, KP.3.1.1 accounts for over half of all COVID cases in the U.S. The next closest subvariant circulating is KP.2.3, with 12 percent of cases. Based on data from Europe, experts are forecasting XEC to overtake KP.3.1.1 in the U.S. over the next several weeks.

3. Symptoms are familiar

So far, reports from across the pond indicate XEC’s symptoms mirror those related to colds, flus, and other strains of COVID—the most common seem to be fever, aches, sore throat, and cough.

4. The new COVID boosters should offer protection against XEC

Vaccine makers develop their products knowing COVID will continue to mutate, but with the hope that the shot will still provide protection against infection and serious illness. Both Pfizer and Moderna recently rolled out their latest COVID boosters, which are tailored to the KP.2 subtype. Experts have signaled XEC is related closely enough to KP.2 that the latest vaccines should provide at least some protection against the subvariant.

“The lab studies, which have been very predictive in the past, give us every reason to be confident that what’s in the vaccines now will indeed protect us during the winter,” William Schaffner, MD, previously told Well+Good.

The recommendations for who should get those shots have not changed. The CDC recommends everyone ages six months and older get vaccinated against COVID, but it is especially important for people who are 65 and older, at high risk for a severe case of the virus, or immunocompromised.

As we have seen with previous waves of COVID, cases are likely to grow as temperatures cool and people gather indoors more often. While we don’t know for sure how XEC will spread, we do know that tried-and-true measures—like regular handwashing, staying home when sick, masking up in crowded settings, and getting vaccinated—help reduce the spread of any virus.

—medically reviewed by Jennifer Logan, MD, MPH