The COVID-19 lull in the U.S. may soon come to an end, as a new family of SARS-CoV-2 variants—nicknamed “FLiRT” variants—begins to spread nationwide.

These variants are distant Omicron relatives that spun out from JN.1, the variant behind the surge in cases this past winter. They’ve been dubbed “FLiRT” variants based on the technical names for their mutations, one of which includes the letters “F” and “L,” and another of which includes the letters “R” and “T.”

Within the FLiRT family, one variant in particular has risen to prominence: KP.2, which accounted for about 25% of new sequenced cases during the two weeks ending Apr. 27, according to data from the U.S. Centers for Disease Control and Prevention (CDC). Other FLiRT variants, including KP.1.1, have not become as widespread in the U.S. yet.