Yale Medicine Experts think this new, highly transmissible variant could soon take hold in the U.S. A new highly transmissible coronavirus subvariant is starting to spread in the United States. Experts say it could become the dominant SARS-CoV-2 strain just in time for winter, when COVID-19 infections and hospitalizations tend to peak.
The variant is called XEC. It’s a subvariant of the SARS-CoV-2 Omicron strain, which has spawned multiple descendants since it surfaced in the U.S. in 2021. XEC first appeared in Germany in June 2024 before spreading rapidly throughout other parts of Europe.
The good news is that so far there is no evidence that XEC causes different symptoms or more severe disease than other recent strains—although a COVID infection is always a concern for certain people, including those who are older or immunocompromised.
So far, XEC is responsible for 5.7% of COVID infections in the U.S.—making it the fifth most prevalent strain here, according to a Centers for Disease Control and Prevention (CDC) estimate at the end of September.
“One reason for the concern is that XEC has moved quickly enough to outpace the growth of all other SARS-CoV-2 variants in a few areas in Europe,” says Scott Roberts, MD, a Yale Medicine infectious diseases specialist. “The rate of infections from XEC they’re seeing in some countries rose pretty quickly compared to previous variants in those same places.” By the end of September, XEC had been detected in at least 25 states in the U.S., he adds.
The XEC COVID strain is also rising at a time when people are starting to get the updated 2024-2025 COVID vaccines that became available in the U.S. in August. Dr. Roberts is encouraging everyone ages 6 months and older to get vaccinated with the updated shot for protection against the virus.