Although the US respiratory virus season may be coming to an end, worries about a possible summer wave are raised by the emergence of a new subset of COVID-19 variants.
Following their mutations, the family of variants known as “FLiRT” included KP.2, which is currently the most common variant in the US. KP.2, the omicron subvariant that caused a spike in COVID cases last winter, has surpassed JN.1 in recent weeks.
The US Centers for Disease Control and Prevention’s most recent data indicates that KP.2 is responsible for one in every four infections in the country.
KP.2 was responsible for almost 25% of cases in the US during the two weeks ending April 27, an increase from roughly 10% during the two weeks ending April 13. JN.1 is the second most common variant after KP.2, making up 22% of cases. JN.1.7 and JN.1.13.1 are the two JN.1 subvariants that come next.
Although it is not as common as KP.2, another FLiRT variant known as KP.1.1 is also circulating in the United States. According to the CDC, it currently represents 7.5% of infections across the country.
The nation is experiencing a COVID-19 lull, but despite this, worries about a second wave of infections this summer are being raised by the new FLiRT variants.
Will the COVID-19 pandemic recur? What symptoms do the FLiRT variants present with? Do vaccines still work? To find out more, we talked to professionals.
FLIRT variants
The FLiRT variants, KP.2 and KP.1.1, were first found in wastewater samples from all over the nation. They are spinoffs of JN.1.11.1, a direct descendant of JN.1.
Dr. Albert Ko, infectious disease physician and Yale School of Public Health professor of public health, epidemiology, and medicine, says that the new variants have two additional mutations that distinguish them from JN.1 and appear to give them an advantage.
The Infectious Disease Society of America states that the moniker “FLiRT” is derived from the scientific terms for their mutations.
The FLiRT variants are members of the omicron family, as are other COVID-19 strains that have become more common in the United States over the last year, including JN.1, HV.1, EG.5, aka Eris, and XBB.1.16, or Arcturus.
The rise of KP.2 and other FLiRT variants, according to virologist Andrew Pekosz, Ph.D., of Johns Hopkins University, is the “same old story.”
A new, highly contagious strain of the SARS-CoV-2 virus emerges as a result of a mutation, eventually taking over as the predominant strain. “Compared to other viruses like influenza, it occurs in a timeline of three to six months, which is much faster,” says Pekosz.
Are the recent variants more contagious?
The experts point out that the fact that the percentage of cases caused by KP.2 is rising while the percentage caused by other variants is falling indicates that KP.2 possesses advantages.
Pekosz notes that KP.2 resembles its highly contagious parent strain, JN.1 quite a bit. “Except it has these two mutations. I think these two mutations together are making KP.2 a better virus in that it retains its ability to transmit, but now evades some of the pre-existing immunity in the population,” says Pekosz.
The CDC reports that over 97% of Americans are naturally or through vaccinations protected against the SARS-CoV-2 virus, although this immunity wanes with time.
A vulnerable population brought about by declining immunity and low vaccination rates could make the FLiRT variants more likely to proliferate. The experts say only time and more data will tell.
According to laboratory research, KP.2 is sufficiently mutated that current vaccinations and immunity from previous infections will only offer partial protection, according to Schaffner. “We’ll have to see how true that is, but it appears, over time, to be becoming a more prominent variant,” he says.