The newest strain of the COVID-19 virus, XEC, is spreading across the country.
According to data from the Global Influenza Surveillance and Response System (GISRS), the new variant has been reported in at least 25 states in the United States, WebMD reported.
States with the highest number of cases (more than 10 each) include California, New Jersey and Virginia, according to the data.
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As of Friday, the variant was not yet being tracked by the U.S. Centers for Disease Control and Prevention (CDC) or the World Health Organization (WHO).
Infectious disease experts say XEC is a mix of two descendants of last year’s JN.1 strain. (iStock)
According to the CDC website, KP.3.1.1 is still considered the “dominant variant” of the virus.
Dr. Jake Glanville, CEO of San Francisco, California-based Centivax and an infectious disease expert, told Fox News Digital that XEC is a mix of two descendants of last year’s JN.1 strain.
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“Coronaviruses are continually mutating and when a new strain becomes dominant it tends to be because that strain has an advantage in terms of infection or transmission over all other circulating variants,” he told Fox News Digital in an on-camera interview.
XEC is an example of such a new variant, doctors confirmed.


Last month, the U.S. Food and Drug Administration (FDA) approved improved COVID-19 vaccines from Moderna Inc. and Pfizer Inc. for the 2024-2025 season. (REUTERS/Dado Ruvic/Illustration/File Photo)
“Right now there doesn’t appear to be any obvious symptoms or mode of transmission,” Glanville said.
“It may be a little more contagious than other strains so it’s becoming more dominant, but there’s no reason for the public to be particularly concerned.”
Current vaccines are based on the KP.2 strain, which is itself a descendant of JN.1 and a close match to XEC, Glanville noted.
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“XEC does not display any unusual symptoms of infection and is very similar to the vaccine strain selected by the FDA this year, so XEC is not of particular concern at this time,” the expert said.
“This is something vaccine developers are monitoring to understand at what point they may need to create new vaccines, because eventually XEC and other strains will mutate and escape the current vaccine designs.”


“Vaccine makers are monitoring these strains because it is possible that XEC or other strains will eventually mutate and escape current vaccine designs,” the infectious disease expert said. (iStock)
Glanville noted that while it’s always possible that a new variant could evolve into a mutation that causes a new type of illness, that hasn’t happened in XEC so far.
“This seems to be a coronavirus we’re familiar with,” the doctor said.
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Dr. Mark Siegel, a senior medical analyst at Fox News and professor of clinical medicine at New York University Langone Medical Center, agreed that the current 2024-2025 vaccines will need to cover the newly emerging XEC subvariants.
“Common symptoms include sore throat, stuffy nose, cough, fatigue, nausea and loss of taste,” he told Fox News Digital.
“Eventually, XEC or another strain will mutate and escape the current vaccine design.”
Siegel recommends the updated vaccine for older adults, those who are immunocompromised or have chronic illnesses, as well as young children who haven’t previously received a COVID vaccine.
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Last month, the U.S. Food and Drug Administration (FDA) approved improved COVID-19 vaccines from Moderna Inc. and Pfizer Inc. for the 2024-2025 season.
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The FDA said the improved mRNA vaccines Comirnaty and Spikevax have been fully approved for people 12 years of age and older, while the Moderna Inc. COVID-19 vaccine and the Pfizer-BioNTech COVID-19 vaccine have been granted emergency use authorization for children aged 6 months to 11 years old.
Fox News Digital has reached out to the CDC for comment.