The strain, known as XEC, is gaining a foothold in the United States, accounting for an estimated 5.7% of new cases in the past two weeks, the Centers for Disease Control and Prevention said Friday.
“We don’t know if it will have legs and soar up in the charts,” said Dr. Peter Chin-Hong, a professor of medicine and an infectious disease specialist at the University of California, San Francisco. “But it has the features that could make it the one to watch.”
XEC caught the eye of experts as it spread quickly in parts of Europe in recent weeks. Still, a lot remains unknown about the strain.
“Once again, Covid is showing that it is not finished mutating, and we’re still seeing the limitations of our vaccines in controlling it,” said Rick Bright, an immunologist and the former director of the Biomedical Advanced Research and Development Authority, part of the Department of Health and Human Services.