A new variant of COVID-19 called 'FLiRT' spreads in the US. These are its symptoms

The respiratory virus season may be coming to an end in the United States, but a new group of COVID-19 variants is already circulating in the country and raising concerns about a possible summer surge.

The family of variants, nicknamed FLiRT Due to its mutations, it includes KP.2, which is now the dominant variant in the country. In recent weeks, KP.2 has outperformed JN.1, the omicron subvariant that drove a surge in COVID cases last winter.

Currently, the KP.2 subvariant is responsible for one in four infections nationwide, according to the latest data from the United States Centers for Disease Control and Prevention (CDC).

During a two-week period ending April 27, KP.2 accounted for nearly 25% of US cases, up from about 10% during the previous two-week period ending April 13. After KP.2, the most common variant is JN,1, accounting for 22% of cases, followed by two subvariants of JN.1: JN.1.7 and JN.1.13.1.

Another variant also circulates in the US FLiRT, called KP.1.1, but is less widespread than KP.2. It currently accounts for about 7.5% of infections nationwide, according to the CDC.

Although cases and hospitalizations have decreased and the country is in the middle of a lull regarding COVID-19 infections, the new variants FLiRT are stoking concerns about another possible wave of infections this summer.

Will there be another wave of COVID-19? What are the symptoms of the variants FLiRT? Are vaccines still effective? We spoke to some experts to find out more about these new variants.

What are the variants FLiRT?

The variants FLiRT —KP.2 and KP.1.1— are derivations of JN.1.11.1, a direct descendant of JN.1, and were initially detected in wastewater samples throughout the country.

The new variants present two additional mutations that differentiate them from JN.1 and seem to give them an advantage over previous variants, Albert Ko, an infectious disease doctor and professor of public health, epidemiology and medicine at the School of Medicine, explains to .com. of Yale Public Health.

The nickname FLiRT is based on the technical names of their mutations, according to the Infectious Diseases Society of America.

Like other strains of COVID-19 that have spread across the US in the last year — JN.1, HV.1, EG.5 alias Eris, and XBB.1.16 or Arcturus — the variants FLiRT They are part of the Omicron family.

The appearance of KP.2 and other variants FLiRT It's “the same old story,” Andrew Pekosz, a virologist at Johns Hopkins University, tells .com. The SARS-CoV-2 virus mutates and creates a new highly contagious variant, which becomes the dominant strain. “The time frame in which this occurs, three to six months, is much faster than what we see with other viruses like the flu,” says Pekosz.

Are the new variants more transmissible?

“It's still early, but the initial impression is that this variant (KP.2) is quite transmissible,” William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center, tells .com.

The proportion of cases caused by KP.2 is increasing, while infections from other variants are decreasing, suggesting that KP.2 has characteristics that give it an advantage, according to experts.

KP.2 closely resembles its parental strain JN.1, says Pekosz, which is highly contagious. “Except it has these two mutations… I think these two mutations together make KP.2 a more effective virus because it maintains its ability to transmit, but now it also evades some of the pre-existing immunity in the population,” Pekosz says.

According to the CDC, more than 97% of the US population has natural or vaccine-induced antibodies against the SARS-CoV-2 virus, but this immune protection fades over time.

Low vaccination rates and waning immunity create a vulnerable population, which may allow variants FLiRT they take root. Experts point out that only time and more data will tell.

Laboratory studies suggest that KP.2 has mutated enough that current vaccines and immunity from previous infections provide only partial protection, according to Schaffner. “We'll have to see to what extent that's true, but it seems like it's becoming a more prominent variant over time,” she adds.

“It's still early for KP.2 to emerge, but I don't think there's any need to sound the alarm,” says Ko.

Will there be a rebound in the summer?

Experts say it is too early to know if the variants of FLiRT They will cause a wave or a summer rebound. However, it is clear that COVID-19 is still circulating and there will be no respite.

“We are seeing these infections throughout the year, at adjustable levels… We are probably not yet in the phase where COVID completely disappears at any time of the year,” says Pekosz.

Positive tests, an early indicator of case levels, stood at 3% as of April 20, down 0.4% from the previous week and a sharp decline from 12% in mid-January, according to the CDC. (The CDC no longer collects the total number of cases in the US.)

“We're not seeing a lot of hospitalizations, and we're at much lower levels than we were in the winter, so I would say we're at a low point, which is reassuring,” Ko says.

Wastewater data released by the CDC shows that the level of COVID-19 viral activity is currently “minimal,” having been considered high or very high for most of January and February.

“It seems like transmission is pretty low right now, and that makes sense because typically the big spikes occur in the winter, when people are indoors and in more contact,” Ko says.

Experts point out that COVID-19 has caused summer surges in the past, which are usually smaller than winter infections. “I don't think we're going to see any kind of massive increase in cases,” Pekosz says.

Based on current COVID-19 trends, Ko says: “KP.2 may cause a small surge, but not necessarily the big spikes we saw in the winter. However, it is too early to say.”

The seasonality of COVID-19 is something scientists are still trying to understand. “This virus is becoming integrated into our population and our way of life,” Schaffner says.

There are several reassuring factors, explains Ko. First, KP.2 is not a highly divergent variant, that is, it does not have a large number of new mutations that differentiate it from other strains. Second, many people have immunity from having recently been infected with the variant FLiRT predecessor known as JN.1. Finally, during the summer, people spend less time indoors, allowing the virus less opportunity to spread.

“I don't expect a big increase in summer but again, we have to be cautious and follow the data,” says Ko. “We always have to be cautious because SARS-CoV-2 has taught us a lot of new things.”

What are the symptoms of the new variants?

It is still early to know if the symptoms of KP.2 and other variants FLiRT They are different from those of previous strains.

“The variants FLiRT They probably aren't going to create very distinctive symptoms. At the moment it seems that they are going to be like the other subvariants,” says Schaffner.

Symptoms of variants FLiRT are similar to those caused by JN.1, which include:

  • Sore throat.
  • Cough.
  • Fatigue.
  • Congestion.
  • Runny nose.
  • Headache.
  • Muscle pains.
  • Fever or chills.
  • Loss of the sense of taste or smell.
  • Shortness of breath or difficulty breathing.
  • Nausea or vomiting.
  • Diarrhea.

According to the CDC, the type and severity of symptoms a person experiences typically depends more on their underlying health and immunity than on the variant causing the infection.

Like the JN.1 and other omicron subvariants, the variants FLiRT they seem to cause milder infections, Schaffer says.

“There is no evidence now to make us think that KP.2 is more virulent or that it can cause more severe disease than previous variants,” Ko says.

Do vaccines still protect us?

“Early laboratory studies indicate that the vaccines will continue to provide protection against the KP.2 variant. Maybe a little less protection, but by no means zero,” says Schaffner.

As the virus mutates, it is becoming progressively different from the omicron strain that the latest updated booster launched in fall 2023 focuses on. “We expected that to happen, and we anticipate that the plan is to have an updated vaccine in the fall that be available to everyone,” says Schaffner.

Even if vaccines don't prevent infection, they can still offer some protection by preventing serious illness, hospitalization and complications from COVID-19, .com previously reported.

“It is clear that the most serious cases that come to the emergency room predominate in people who are not up to date on their vaccines or who have not been vaccinated in a very long period of time,” says Pekosz.

Vaccination is especially important for older people, Pekosz says, which is why the CDC recently recommended adults age 65 and older get an extra dose of the COVID-19 vaccine that was updated for 2023-2024.

Unfortunately, vaccine uptake remains low, experts say. “Vaccines continue to show signs of effectiveness, but they are not used anywhere near the level they should be,” says Pekosz.

All current PCR and home tests detect the KP.2 variant and other variants FLiRT, experts say. (Although if you have COVID symptoms and test negative, it's a good idea to stay home to avoid potentially exposing other people, .com previously reported.)

If you use a home antigen test, always remember to check the expiration date and whether it has been extended by the US Food and Drug Administration (FDA).

“Antivirals (such as Paxlovid) also work well… There are no major signs of antiviral resistance in the population, which is a positive sign,” says Pekosz.

Tips to protect yourself

Although it is too early to know how the variants will develop FLiRT This summer, people can always take steps to protect themselves and others against COVID-19.

The CDC recommends:

  • Stay up to date on COVID-19 vaccines.
  • Get tested for COVID-19 if you have symptoms or have been exposed to the virus.
  • Stay home when you are sick.
  • Return to normal activities only when you are fever-free and symptoms have improved for at least 24 hours.
  • Practice good hand hygiene.
  • Improve ventilation in the places you frequent.
  • Wear a mask in closed and crowded places.
  • Practice social distancing.