New COVID-19 FLiRT variants are now the dominant variant. Could there be a summer surge?

The Centers for Disease Control and Prevention has detected a new set of COVID-19 variants nicknamed FLiRT in wastewater surveillance, according to data from the agency.

From April 28 through May 11, the variant, labeled KP.2, makes up about 28% of the cases in the United States, according to the CDC. That makes it the new dominant variant in the country, overtaking JN.1. The JN.1 variant, which spread globally over the winter, made up about 16% of COVID-19 cases in the U.S. in the same two-week span.

KP.1.1, another FLiRT variant that is circulating, made up about 7% of COVID-19 cases in that two-week span, according to CDC data.

"The CDC is tracking SARS-CoV-2 variants KP.2 and KP.1.1, sometimes referred to as 'FLiRT,' and working to better understand their potential impact on public health," the agency said in an emailed statement to USA TODAY last week.

"Currently, KP.2 is the dominant variant in the United States, but laboratory testing data indicate low levels of SARS-CoV-2 transmission overall at this time. That means that while KP.2 is proportionally the most predominant variant, it is not causing an increase in infections as transmission of SARS-CoV-2 is low," the CDC said in the statement.

According to the CDC, only 22.6% of adults reported having received an updated 2023-24 COVID-19 vaccine since September 2023. Data also shows that vaccination coverage increased by age and was highest among adults 75 and older.

FLiRT variant:There's a new COVID-19 variant called FLiRT: Here's what you need to know about it

What are the 'FLiRT' variants?

FLiRT is the term being used to describe a whole family of different variants, including KP.2, JN.1.7 and any other variants starting with KP or JN that appear to have picked up the same set of mutations, according to Andy Pekosz, PhD, a professor in molecular microbiology and immunology at the Bloomberg School of Public Health at Johns Hopkins University, in an article posted by the university.

"They are all descendants of the JN.1 variant that has been dominant in the U.S. for the past several months," Pekosz said in the article. "Viruses like SARS-CoV-2 mutate frequently, and when they mutate to evade recognition by antibodies, this often weakens their ability to bind to the cells they want to infect. We then see mutations appear that improve that binding ability."

Will there be a summer surge in COVID cases due to 'FLiRT' variants?

Pekosz said a summer surge is certainly possible, and that the FLiRT variants would be high on his list of viruses that could cause another wave of infections in the U.S.

"That said, our definition of a wave has changed; while we still see case rates rise and fall throughout the year, we see much lower numbers of cases of hospitalizations or deaths than we saw in the first couple years of the pandemic," Pekosz said in the article.

Pekosz also noted that while the waves are becoming smaller, they are still impacting our susceptible populations: the elderly, people who are immunocompromised, and those with other secondary medical conditions.

Symptoms of COVID 'FLiRT' variant

According to the CDC, there are "no current indicators" that KP.2 would cause more severe illness than other strains. The agency said it would continue to monitor community transmission of the virus and how vaccines perform against this strain.

The "FLiRT" variant reportedly has similar symptoms to those from JN.1 which include:

• Fever or chills
• Cough
• Sore throat
• Congestion or runny nose
• Headache
• Muscle aches
• Difficulty breathing
• Fatigue
• New loss of taste or smell
• "Brain fog" (feeling less wakeful and aware)
• Gastrointestinal symptoms (upset stomach, mild diarrhea, vomiting)

The CDC notes that the list does not include all possible symptoms and that symptoms may change with new variants and can vary by person.

In general, the agency says, people with COVID-19 have a wide range of symptoms, ranging from mild to severe illness. Symptoms may appear two to 14 days after exposure.

Latest COVID guidance from the CDC

In March 2024, the CDC updated its COVID-19 guidance so people who test positive for the virus will no longer be directed to isolate at home for five days.

Health officials announced a new policy focusing on actions people can take to reduce spreading a variety of common respiratory viruses, such as influenza, respiratory syncytial virus (RSV) and COVID-19. Those actions include staying home when sick, staying up to date with vaccines, practicing good hygiene and improving indoor air quality.

The change marked the first time the agency has revised its coronavirus guidelines since 2021. It is intended for people and employers, not for hospitals or nursing homes that have separate guidance, the CDC said.

CDC officials called the change a streamlined approach that’s easier for people to understand and more in line with circulating respiratory viruses that spread the same way and have similar symptoms. 

Contributing: Eduardo Cuevas, Adrianna Rodriguez, Ken Alltucker, Mary Walrath-Holdridge and Mike Snider

Gabe Hauari is a national trending news reporter at USA TODAY. You can follow him on X @GabeHauari or email him at Gdhauari@gannett.com.