As COVID-19 activity remains high across the United States, a new hybrid variant called XEC is spreading rapidly in Europe and other parts of the world. The XEC variant has been detected in at least 27 U.S. states so far, and some experts are projecting that XEC could become the dominant strain this fall. The emergence of XEC comes as the U.S. sees a slight decline in COVID-19 activity following a summer wave. However, wastewater data from the U.S. Centers for Disease Control and Prevention show that COVID activity is still “high” or “very high” in 34 states.
XEC is a recombinant variant of two previous variants, KP.3.3 and KS.1.1. Experts note that while XEC is similar to its parental strains, it has additional mutations which may give it an advantage over other variants. The World Health Organization classified XEC as a “variant under monitoring” on September 24. XEC is spreading rapidly in Europe, North America, and Asia, with at least 32 countries reporting cases of this variant. In the U.S., nearly 300 sequences of XEC have been detected in 27 states and the District of Columbia as of October 2.
XEC has been identified as a highly contagious variant, similar to other omicron subvariants. While it is easily spread from person to person, it is unclear whether XEC will outcompete other variants. Experts state that there is no evidence yet that XEC is significantly more transmissible than other circulating variants. Some estimate that XEC may cause a surge in cases as fall approaches and respiratory virus season begins in the U.S., but the severity and timing of any potential surge remain uncertain.
There is limited information available about the symptoms of XEC, as it is still early in the emergence of this variant. However, XEC does not appear to be causing any distinctive symptoms or more severe disease compared to previous omicron variants. Symptoms of XEC include sore throat, cough, fatigue, headache, congestion, runny nose, fever, shortness of breath, nausea, diarrhea, and loss of sense of taste or smell. People in high-risk populations are more likely to develop severe disease.
The updated COVID-19 vaccine for 2024–2025 is recommended for everyone ages six months and older. While the vaccine targets the previously dominant KP.2 variant, early laboratory studies suggest that the updated vaccine may offer protection against severe disease caused by XEC. COVID-19 vaccines are safe and effective at preventing severe illness, hospitalization, and death. It is important for people at higher risk of developing severe disease to get vaccinated to protect themselves as the virus continues to circulate.
To protect against XEC and other respiratory viruses as fall approaches, individuals can take steps such as staying up to date with vaccines, staying home when sick, avoiding contact with sick individuals, wearing masks in crowded indoor spaces, improving ventilation, maintaining good hand hygiene, practicing social distancing, and following testing and isolation guidelines as recommended by health authorities. Antivirals such as Paxlovid are also effective and recommended, particularly for those at high risk for severe disease.
