LB.1 is the latest COVID-19 subvariant to make headlines as it circulates in the United States. The highly contagious strain, which emerged shortly after the “FLiRT” variants including KP.3 and KP.2, is causing an increasing number of infections.
As infections and emergency room visits rise in the US, some are concerned about a summer surge.
According to the most recent data from the US Centers for Disease Control and Prevention, LB.1 is currently the third most prevalent COVID-19 variant in the US, just behind the dominant variants KP.3 and KP.2.
As of June 22, KP.3 was estimated to account for 33% of cases in the US. The next most common variant is KP.2, which accounts for about 21% of cases, followed by LB.1, which accounts for 17.5% of cases.
Since late May, the number of cases caused by LB.1 has more than doubled, according to CDC data. Some experts say this new mutated variant is on track to surpass the FLiRT variants in the coming weeks.
While overall COVID-19 numbers, including hospitalizations and deaths, are relatively low compared to winter, it is clear that the virus is on the rise. Is the country facing a summer peak?
Here’s what we know so far about COVID-19 summer trends and the new LB.1 variant.
Is there a summer peak?
In recent weeks, cases have been increasing in most U.S. states, particularly in the West. The CDC estimates that as of June 25, COVID-19 case counts are growing or likely growing in 44 states, stable or uncertain in five states, and declining in one state, Hawaii.
“Right now (early July), we’re not seeing a big nationwide surge in cases, but cases are increasing in some places and leveling off in other places,” Andrew Pekosz, Ph.D., a virologist at Johns Hopkins University, tells TODAY.com. The country is likely at the beginning of a surge, Pekosz adds, but it’s too early to tell how COVID-19 trends will play out over the summer.
Test positivity was 8% on June 22, according to the CDC, up 1.4% from the previous week but down from a winter peak of 12%. A CDC map shows test positivity is highest in California and the Southwest.
Viral activity in wastewater is “low” nationwide, after being “high” or “very high” for most of the winter. (The CDC no longer tracks the total number of new COVID-19 cases in the U.S.)
According to Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center, what we’re seeing now is more of an expected “boost.” Unlike influenza, COVID-19 is not seasonal and still spreads in the summer, but these bumps are much less substantial than winter surges, Schaffner adds.
As summer vacations peak and people increasingly stay indoors in air conditioning to escape heat waves, COVID-19 is expected to continue to surge. “If it hasn’t shown up in your community yet, it likely will after all the travel over the Fourth of July,” Schaffner says.
What is LB.1?
LB.1 is part of the omicron family — the newest great-grandchild, so to speak, Schaffner says. The LB.1 subvariant is an offshoot of JN.1, which was dominant for most of the winter and spring.
“LB.1 is closely related to the FLiRT variants, but has a number of unique mutations in different parts of the spike protein,” Pekosz says. These include key mutations that impact LB.1’s ability to evade immunity.
“We have seen such mutations before in other variants (including JN.1). … They do not seem particularly concerning or a sign that the virus has changed dramatically,” Pekosz adds.
The emergence of LB.1 continues an ongoing trend, experts note. The SARS-CoV-2 virus mutates and gives rise to new variants, which are better able to escape immunity and outcompete other strains until a new one emerges.
According to the CDC, more than 97% of people in the US have natural or vaccine-induced antibodies to COVID-19, but these disappear over time.
Is LB.1 more contagious?
A characteristic of omikron subvariants is that they are highly contagious. “LB.1 is highly contagious and spreads very easily,” says Schaffner.
How does LB.1 compare to other emerging strains? “It’s too early to tell, but so far there’s no signal that it’s more contagious than the FLiRT variants,” Dr. Bernard Camins, medical director of infection prevention at Mount Sinai Health System, tells TODAY.com.
“It is possible that the disease escapes immunity acquired through infection or the vaccine, but it has not been shown to be more dangerous than previous subvariants,” Camins said.
The recent surge in cases appears to be driven by a combination of new variants, including LB.1 and the FLiRT strains. However, declines in testing and genomic surveillance are making it difficult to accurately track the virus. “It’s becoming increasingly difficult for us to get a good sense of how fast a variant is increasing,” Pekosz said.
What are the symptoms of LB.1?
The experts stress that LB.1 does not appear to cause any obvious or new symptoms and that there is no evidence of the disease becoming more severe.
The symptoms of LB.1 are very similar to those of the FLiRT variants, including:
The newer strains generally seem to cause milder infections, Schaffner says. But COVID can still cause a spectrum of illness.
“Some people have a very classic sore throat, runny nose, cough and low-grade fever,” Dr. Paul Sax, clinical director of the division of infectious diseases at Brigham and Women’s Hospital and a professor of medicine at Harvard Medical School, told NBC News. “Others have mostly nausea and diarrhea with very minimal respiratory symptoms. It can range from A to Z and beyond.”
And “some people may still experience severe symptoms, enough to require hospitalization,” Camins tells TODAY.com — particularly high-risk groups: people 65 and older, people with underlying medical conditions and individuals with weakened immune systems.
“There’s no single symptom where you say, ‘Hey, you probably have COVID,’” Dr. Steven Furr, a family physician in Jackson, Alabama, and president of the American Academy of Family Physicians, told NBC News. “Without a test, we’re not going to know for sure.”
According to the CDC, COVID-related emergency department visits increased 23% in the past week, but are still relatively low. Hospitalization rates are also stable.
According to Schaffner, antiviral drugs such as Paxlovid are effective against LB.1 and other recent strains.
Do vaccines protect against LB.1?
“The current vaccine protects against severe disease,” Schaffner said. The updated 2023-2024 COVID-19 booster, targeting the XXB.1.5 strain, is still available at this time. The CDC recommends that at-risk groups get an extra dose.
The updated 2024-2025 vaccine due out this fall is also expected to provide protection, experts point out. “LB.1 is closely related to KP.2, which looks like the strain that will be targeted in the vaccine next fall,” Pekosz says.
“Previous data shows that there is cross-reactivity, even though the vaccine does not exactly match what is circulating,” Camins said.
Experts are encouraging everyone eligible to get vaccinated against COVID-19 for 2024-2025 this fall.
COVID Guidelines 2024
If you develop COVID-19 symptoms or have been exposed, get tested, experts stress. Testing is an important tool to protect yourself and prevent the spread of the virus.
PCR and antigen tests detect LB.1 and other new variants, Camins notes. If you use an antigen test, follow FDA recommendations to avoid a false negative.
The CDC advises people who test positive to stay home while they are sick and avoid contact with others. The agency previously recommended isolating from others for at least five days after testing positive. But in March 2024, the isolation guidelines changed to say that people can return to normal activities after they are fever-free without medication. And the symptoms have improved for at least 24 hours.
“If you are in a risk group and test positive for COVID-19, we will give you Paxlovid to prevent serious illness,” Schaffner says.
How to protect against the LB.1 variant
As COVID-19 cases continue to rise this summer, consider taking extra steps to protect yourself and others. The CDC recommends that people:
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Stay up to date on COVID-19 vaccines.
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Wear a face mask in crowded indoor areas.
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Ensure good hand hygiene.
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Cover your nose when coughing and sneezing.
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Improve ventilation.
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Keep your distance.
This article was originally published on TODAY.com