The COVID-19 lull in the U.S. may soon come to an end, as a new family of SARS-CoV-2 variantsnicknamed FLiRT variantsbegins 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. Theyve 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.

Researchers are still learning about the FLiRT variants, and many questions remain about how quickly theyll spread, whether theyll cause disease thats more or less severe than what weve seen previously, and how well vaccines will stand up to them. Heres what we know so far.

Despite KP.2's rise in the U.S., its too soon to tell whether the FLiRT family will be responsible for a major surge in cases, says Dr. Eric Topol, executive vice president at Scripps Research, who wrote about the FLiRT variants in a recent edition of his newsletter. For now, the amount of SARS-CoV-2 virus in U.S. wastewater remains minimal, according to the CDC, and hospitalizations and deaths have also continued to decline steadily since their recent peaks in January. At the global level, case counts rose from early to mid-April, but remain far lower than they were a few months ago.

KP.2 and its relatives will likely cause an uptick in cases, but my hunch is it wont be a big wave, Topol says. It might be a wavelet. Thats because people who were recently infected by the JN.1 variant seem to have some protection against reinfection, Topol says, and the virus hasnt mutated enough to become wildly different from previous strains. A recent study from researchers in Japan, which was posted online before being peer-reviewed, also found that KP.2 is less infectious than JN.1.

Vaccines still provide good protection against COVID-19-related hospitalization and death. But two preliminary studiesthe one from Japan and another from researchers in China, which was also posted online before being peer-reviewedsuggest the FLiRT variants may be better at dodging immune protection from vaccines than JN.1 was.

That isnt good, Topol says, especially since many people who got the most recent boosterroughly 30% of adults in the U.S. got it last fall, meaning their protection has begun to wane.

In an Apr. 26 statement, the World Health Organization recommended basing future vaccine formulations on the JN.1 lineage, since it seems the virus will continue to evolve from that variant. The most recent booster was based on an older strain, XBB.1.5.

The virus continues to evolve, but public-health advice remains the same: stay up-to-date on vaccines, test before gatherings, stay home when you're ill, and consider masking and avoiding crowded indoor areas, especially when lots of COVID-19 is going around.

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What to Know About the 'FLiRT' Variants of COVID-19 - TIME