As cold winter weather drives people indoors and flu, colds, and other seasonal respiratory viruses circulate, SARS-CoV-2, the coronavirus that causes COVID-19, has continued to mutate and spread. Most recently a strain called JN.1 moved swiftly to become the most widely circulating variant in the United States, accounting for an estimated 83% to 88% of all circulating variants toward the end of January.
While it can be difficult, if not impossible, to predict the evolution of the coronavirus and its descendants, the Centers for Disease Control and Prevention (CDC) projects that JN.1 cases will continue to rise through the winter. The World Health Organization (WHO) has declared it a “variant of interest.” There is no evidence that JN.1 causes more severe disease, the CDC says, but its rapid spread suggests it is either more transmissible or better at evading the immune system than other circulating variants.
Meanwhile, COVID activity in general has been rising, notes Heidi Zapata, MD, PhD, a Yale Medicine infectious diseases specialist. (That includes infections from variants such as HV.1, which in late January accounted for 5.3% of cases.) “I would say the most important thing for people to know is that the virus is out there, as are respiratory syncytial virus [RSV] and the flu. Any new subvariant is a sign that the SARS-CoV-2 virus is still evolving; it’s still here with us, and we can’t ignore it,” she says.