As the holiday season winds down and Covid-19 cases start to pick up, a variant called JN.1 has now become the most common strain of the virus spreading across the United States.
JN.1, which emerged from the variant BA.2.86 and was first detected in the United States in September, accounted for 44 percent of Covid cases nationwide by mid-December, up from about 7 percent in late November, according to data from the Centers for Disease Control and Prevention.
To some extent, this jump is to be expected. “Variants take some time to get going,” said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center. “Then they speed up, they spread widely, and just when they’re doing that, after several months, a new variant crops up.”
JN.1’s momentum this month suggests that it may be more transmissible or better at evading our immune systems than other variants currently circulating, according to a C.D.C. report published Dec. 22. The agency said that Covid remains “a serious public health threat,” especially for those who have always been at high risk of severe disease, such as older adults, infants, people with compromised immune systems or chronic medical conditions and those who are pregnant.
