A new variant of COVID-19, KP.3, is now the dominant strain in the United States. KP.3 is part of a family of COVID-19 variants called “FLiRT”, which is generating a growing proportion of cases across the country and raising concerns about a potential summer wave.
The FLiRT variants — which include KP.3, KP.2, KP.1.1 — now account for more than half of all COVID-19 infections nationwide, according to the latest data from the the US Centers for Disease Control and Prevention.
These new strains, which scientists have dubbed “FLiRT” due to their mutations in the spike protein, have been circulating in the US since early spring. In April, KP.2 quickly surpassed JN.1, O omicron subvariant who directed a increase in COVID cases last winter.
In recent weeks, the KP.3 variant has surpassed KP.2 to become the most prevalent strain in the US, according to the CDC.
During a two-week period ending June 8, KP.3 accounted for about 25% of U.S. cases, up from about 9% in early May. After KP.3, the next most common variant is KP.2, another FLiRT variant that gained dominance in May and now accounts for about 22% of cases. It is followed by LB.1, a JN.1 subvariant, and another FLiRT variant, KP.1.1.
Together, the FLiRT variants account for about 55% of cases in the US
While hospitalizations have declined and the country appears to be in a COVID-19 lull, there has been an uptick in test positivity and emergency room visits, according to the latest data from the CDC. These trends, along with waves from the previous summer, fueled fears about a rise in infections this summer.
Scientists warn that the FLiRT variants may be better at evading the immune system due to their mutations in the spike protein, and that waning immunity and poor absorption of the latest COVID-19 vaccine have created a more susceptible population.
Will there be another wave of COVID-19? What are the symptoms of FLiRT variants? Are vaccines still effective? We spoke to experts to find out more.
What are the FLIRT variants?
The FLiRT variants – KP.3, KP.2 and KP.1.1 – are derived from JN.1.11.1, a direct descendant of JN.1, and were initially detected in wastewater samples from across the country.
The new variants have additional mutations that differentiate them from JN.1 and appear to give them an advantage over previous variants, said Dr. Albert Ko, an infectious disease physician and professor of public health, epidemiology and medicine at the Yale School of Public Health. . TODAY. with.
The nickname ‘FLiRT” is based on the technical names of its mutations, according to the Infectious Disease Society of America.
Like other COVID-19 strains that gained dominance in the US last year – JN.1, HV.1, EG.5 also known as ErisIt is XBB.1.16 or Arcturus — FLiRT variants are part of the omicron family.
The emergence of KP.2 and other FLiRT variants is the “same old story,” Andrew Pekosz, Ph.D., a virologist at Johns Hopkins University, told TODAY.com. The SARS-CoV-2 virus mutates and gives rise to a new, highly contagious variant, which becomes the dominant strain. “The time frame in which this happens, 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 days, but the initial impression is that this variant is quite transmissible,” Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, told TODAY.com.
The proportion of cases caused by KP.2 and now KP.3 is increasing, while the proportion caused by other variants is decreasing, suggesting that the FLiRT variants have characteristics that give them an advantage, experts note.
KP.2 is very similar to its parent strain JN.1, says Pekosz, which is highly contagious. “Except it has these two mutations… I think these two mutations together are making KP.2 a better virus because it maintains its ability to transmit, but now it also evades some of the pre-existing immunity in the population,” he said. says Pekosz.
More than 97% of people in the US have natural or vaccine-induced antibodies against the SARS-CoV-2 virus, according to the CDC, but this immune protection wears off over time.
Low vaccination rates and waning immunity create a vulnerable population, which may allow FLiRT variants to become established. Only time and more data will tell, experts note.
Laboratory studies suggest that the FLiRT variants have enough mutations that current vaccines and immunity from previous infections provide only partial protection, Schaffner says. “We will have to see how true this is, but it appears that over time it is becoming a more prominent variant,” she adds.
“It’s still too early for KP.2 to emerge, but I don’t think we need to sound the alarm just yet,” says Ko.
Will there be a sudden spike in the summer?
It’s too early to say whether the FLiRT variants will cause a summer surge or surge, experts note. However, it is clear that COVID-19 is still circulating and will not catch a break.
“We are seeing these infections throughout the year, at modulating levels. We’re probably not at the stage yet where we’ll see COVID disappear completely at any time of the year,” says Pekosz.
Test positivity, which is an early indicator of case levels, was 4.5% on June 7, a 0.4% increase from the previous week but a sharp decline from a peak of around 12% in mid-January, according to the CDC. (The CDC no longer tracks the total number of cases in the US)
“We’re not seeing a lot of hospitalizations and we’re certainly much lower than we were in the winter, so I would say right now we’re at a low point, which is reassuring,” says Ko.
Wastewater Data published by the CDC show that the level of COVID-19 viral activity is currently “low” – it was considered high or very high throughout most of January and February.
“It appears that transmission is quite low right now, and that makes sense because typically the big spikes occur in the winter, when people are indoors and in greater contact,” says Ko.
COVID-19 caused summer waves in the past, experts note, they are many times smaller than winter waves. “I don’t think we’re going to see any kind of massive increase in cases,” Pekosz says.
Speculating 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 — again, it’s too early to tell.”
The seasonality of COVID-19 is something that scientists are still trying to understand. But one thing is obvious: “This virus is now integrating itself into our population and our way of life,” says Schaffner.
There are several reassuring factors, says Ko. Firstly, KP.2 is not a highly divergent variant – in other words, it does not have a very large number of new mutations that differentiate it from other strains. Second, many people have immunity because they were recently infected with the JN.1 predecessor FLiRT variant. Lastly, during the summer, people spend less time indoors, which allows fewer opportunities for the virus to spread.
“I don’t expect a big increase in the summer, but again, we have to be cautious and watch the data,” says Ko. “We always have to be humble because SARS-CoV-2 has taught us many new things.”
What are the symptoms of the newest COVID variants?
It is still too early to say whether the symptoms of KP.3, KP.2 and other FLiRT variants are different from previous strains.
“FLiRT variants are unlikely to create very distinct symptoms. At the moment, it seems to follow the other subvariants”, says Schaffner.
Symptoms of FLiRT variants are similar to those caused by JN.1, which include:
According to the CDC, the type and severity of symptoms a person experiences often depends more on the person’s underlying health and immunity than on the variant that caused the infection.
Similar to JN.1 and other omicron subvariants, the FLiRT variants appear to be causing milder infections, Schaffer says.
“There is now no evidence that makes us think that KP.2 is more virulent or more capable of causing serious disease than previous variants,” says Ko.
Do vaccines protect against newer variants?
“Early laboratory studies indicate that the vaccines will continue to provide protection against KP.2 – a little less protection, but by no means zero,” says Schaffner.
As the virus mutates, it becomes progressively different from the micron strain targeted in the latest booster updated launched in the fall of 2023. “We expected this to happen and anticipate that the plan is to have an updated vaccine available to everyone by the fall,” says Schaffner.
Preliminary laboratory data from Japan, which has not been peer-reviewed, suggests that current COVID-19 vaccines in the US may be less effective against KP.2 than JN.1, NBC News previously reported.
advisors from US Food and Drug Administration met on Tuesday, June 5, to decide which strains to include in updated COVID-19 vaccines for 2024–2025. The committee voted unanimously to recommend a monovalent vaccine targeting the JN.1 variant for this fall, the agency said in a news release.
Even if vaccines do not prevent infection, they can still offer some protection by preventing serious illness, hospitalization and complications from COVID-19. TODAY.com previously reported.
“It is still clear that the most serious cases that arrive at the emergency room predominate in people who are not up to date with their vaccinations or who have not had the vaccine for a long time,” says Pekosz.
Vaccination is especially important for seniors, Pekosz says, which is why the CDC recently recommended that adults 65 and older receive an additional dose of the vaccine. Updated COVID-19 Vaccine 2023-2024.
Unfortunately, vaccination adherence is still poor, experts note. “The vaccines are still showing signs of effectiveness, but they are not being used anywhere near the level they should be,” says Pekosz.
As of April 27, 2024, only about 22% of adults and 14% of children reported having received the updated COVID-19 vaccine released in September 2023, According to the CDC.
All current PCR and home tests recognize KP.2 and other FLiRT variants, experts note. (Although if you have COVID symptoms and negative testIt’s a good idea to stay home to avoid potential exposure to others, TODAY.com previously reported.
If you are using a home antigen test, always remember to check the expiration date and whether it has been extended by the FDA.
“Antivirals (like Paxlovid) are also working well. … There are no major signs of antiviral resistance in the population, which is a positive sign,” says Pekosz.
How to protect yourself against new FLiRT variants
While it’s too early to say how FLiRT variants will develop this summer, people can always take steps to protect themselves and others from COVID-19.
The CDC recommends the following prevention strategies:
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Stay up to date with COVID-19 vaccines.
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Test for COVID-19 if you have symptoms or exposure.
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Stay home when you are sick.
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Return to normal activities only after you have no fever and symptoms have improved for at least 24 hours.
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Practice good hand hygiene.
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Improve ventilation.
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Wear a mask in closed, crowded spaces.
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Practice social distancing.
This article was originally published in TODAY.com
