FLiRT COVID-19 Variants Are Spreading: What to Know About KP.2, KP.3, and KP.1.1 Strains

• FLiRT COVID-19 variants, KP.1.1, KP.2, and KP.3 are spreading in the U.S.
• The current COVID vaccine may not protect against them as well as previous variants.
• It’s not clear if these are more infectious than other variants.

After a fairly quiet spring, COVID-19 cases are on the rise again in the U.S. and SARS-COV-2, the virus that causes COVID-19, keeps churning out new variants. The latest is a trio, KP.2, KP.3, and KP.1.1, known collectively as the FLiRT variants, and they’re leading an uptick in new COVID-19 infections in the U.S.

One FLiRT variant, KP.2 is now the dominant variant in the U.S., and it’s been quickly increasing in cases over the past few weeks. KP.2 now makes up 28.5% of COVID-19 cases in the U.S., according to data from the Centers for Disease Control and Prevention (CDC).

Meet the experts: Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York; Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security; William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine.

KP.3 came out of nowhere after being a blip on the radar in late April and now makes up nearly 13% of COVID-19 cases, just behind KP.2. But sister variant KP.1.1 is also rising in the ranks and currently makes up 9.2% of COVID-19 cases in the country. Collectively the FLiRT variants are causing plenty of issues around the U.S.

So, what are the FLiRT variants and how concerned should you be? Infectious disease doctors break down the latest COVID-19 strains.

The FLiRT variants are the collective name given to KP.2, KP.3, and KP.1.1. These are descendants of JN.1.11.1, a spinoff of JN.1, which was the most common variant in the U.S. until late April, explains Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York.

While the name “FLiRT” is cute, it isn’t random—it’s based on the technical names for their mutations, according to the Infectious Disease Society of America (IDSA). “These are part of the Omicron family,” Dr. Russo says. “They’re like siblings.”

There’s not a lot of detail about these variants available at the moment, but preliminary research shows that KP.2 has three changes in its spike protein compared to JN.1, Dr. Russo says. (In case you’re not familiar, the spike protein is what SARS-CoV-2 uses to latch onto your cells and infect you.)

In mid-May, the World Health Organization (WHO) said in an update that KP.2 and KP.3 were responsible for nearly 10% and 20% of cases, respectively, globally. The WHO has classified these variants as being “under monitoring,” meaning they’re on the radar but there’s no reason to sound an alarm about them at this point.

It’s worth pointing out that the portion of cases caused by KP.2 is increasing while the portion of cases caused by other variants is decreasing. That implies that there is something about KP.2 that gives it an advantage over the others, Dr. Russo says.

It’s worth pointing out that KP.2 and KP.3 have risen quickly when it comes to the number of COVID-19 cases they’ve caused, while cases caused by other variants are decreasing. That implies that there is something that gives them an advantage over the others, Dr. Russo says.

Overall, Dr. Russo says that the FLiRT variants “don’t seem to be more or less virulent than JN.1, but we are still learning about KP.2 and its siblings.”

As for KP.3’s quick rise, Dr. Russo says “time will tell” if this variant ends up behaving differently from its sibling FLiRT variants.

As of now, doctors say there’s nothing to suggest that the FLiRT variants are any more concerning to the general population than other recent COVID-19 variants. However, William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine, points out that there is some early data that show KP.2 may be able to evade the protection from the vaccine a little more than previous COVID vaccines. (More on that in a moment.)

But there’s no need to panic about new variants gaining steam in general. “As SARS-CoV2 continues to circulate, it will always be generating new variants,” says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security.

Doctors say that’s pretty tough. There’s nothing that you or your doctor would notice that would indicate that you have a FLiRT variant as opposed to another COVID-19 variant, Dr. Russo says.

In fact, the only way that the CDC has data on different variants is through genomic sequencing, which looks at the genetic code of the virus to see which variant you have—and that’s not something you’d get from even the best at-home COVID-19 tests or that your doctor would get from a rapid test in their office.

Doctors say it’s hard to tell for sure right now, but Dr. Schaffner points out that previous variants haven’t looked that different when it comes to symptoms, either.

According to the CDC, these are the most common symptoms of COVID-19:

• Fever or chills
• Cough
• Shortness of breath or difficulty breathing
• Fatigue
• Muscle or body aches
• Headache
• New loss of taste or smell
• Sore throat
• Congestion or runny nose
• Nausea or vomiting
• Diarrhea

Still, “the loss of taste and smell seems less common now,” Dr. Schaffner says. It could be because of changes in the virus itself or because people have developed more immunity, either through vaccinations or being infected, he says. “We’re all experienced now with COVID,” he adds.

Yes, Dr. Schaffner says that home tests should still be able to detect the FLiRT variants. However, keep in mind that these tests expire after a while—tests hanging in your medicine cabinet for years may be less effective or not efficient at all at picking up any COVID-19 variants if the expiration date has passed.

If you have COVID-like symptoms and plan to test yourself, just check the expiration date on the side of the box. Because some tests have had their expiration dates extended, you can double-check the actual date of yours on the U.S. Food and Drug Administration’s (FDA) website. Some dates have been extended while others have not, making it important to look.

Yes, the COVID-19 vaccine is protective against the FLiRT variants, although there is data to suggest that it might not be as effective as it’s been against other strains.

“It may be off to the side a little bit in regards to protection from the vaccine,” Dr. Schaffner says. “Protection is not zero, but it’s not quite as good as it was before.”

If you’re in a high-risk group and you haven’t gotten the updated vaccine, Dr. Schaffner recommends getting it to increase your protection throughout the summer. “For sure when the new vaccine comes out in the fall, we should all get it,” he says.

That’s not clear. “This is still very early days,” Dr. Schaffner says. As of right now, there is no indication that the FLiRT variants are any more risky for developing long COVID than other variants. However, that may change over time.

The bottom line

The FLiRT variants are just the latest in a long line of new variants that have surfaced from SARS-CoV-2. These strains are new to the scene and researchers are still learning more about them. However, they do seem to be more infectious than previous variants.

If you have symptoms of COVID-19, doctors recommend testing yourself and doing your best to prevent the spread of the virus, especially if you spend time around people who are high risk for severe complications of the virus. “We’re underestimating the severity of COVID,” Dr. Russo says. Stay up to date with the latest COVID guidelines and if you test positive, wear a well-fitting mask to protect others.

This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.