LB.1 is the latest COVID-19 subvariant to make headlines as it circulates in the United States. This highly contagious strain, which emerged shortly after the “FLiRT” variants, including KP.3 and KP.2, is causing a growing proportion of infections.
As the United States sees a surge in cases and emergency room visits across the country, some are worried about a summer surge.
LB.1 is currently the third most common COVID-19 variant in the United States, just behind the dominant KP.3 and KP.2 variants, according to the latest data from the U.S. Centers for Disease Control and Prevention.
As of June 22, KP.3 accounts for about 33% of cases in the United States. The second 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 share of cases caused by LB.1 has more than doubled, according to CDC data. Some experts say this new mutated variant could be on track to outcompete the FLiRT variants in the coming weeks.
Although overall COVID-19 numbers, including hospitalizations and deaths, are relatively low compared to the winter, it is clear that the virus is on the rise. Is the country facing a summer surge?
Here’s what we know so far about COVID-19 summer trends and the new LB.1 variant.
Is there a summer surge?
In recent weeks, case numbers have increased in most U.S. states, particularly in the West. The CDC estimates that as of June 25, COVID-19 cases are increasing or likely increasing in 44 states, stable or uncertain in 5 states, and decreasing in one state, Hawaii.
“Right now (early July), we’re not seeing a major spike in cases nationally, but cases are increasing in some places and leveling off in others,” Andrew Pekosz, Ph.D., a virologist at Johns Hopkins University, tells TODAY.com. The country is likely in the early stages of a surge, Pekosz adds, but it’s too early to tell how COVID-19 trends will evolve this summer.
The test positivity rate was 8% as of June 22, according to the CDC, up 1.4% from the previous week but lower than the 12% peak seen in the winter. A CDC map shows that test positivity is highest in California and the Southwest.
Viral activity in wastewater is “low” nationwide, down from “high” or “very high” for most of the winter. (The CDC no longer tracks total new COVID-19 cases in the U.S.)
What we’re seeing now is more like an expected “surge,” according to Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center. Unlike the flu, COVID-19 is not seasonal and continues to spread in the summer, but these surges are much smaller than winter surges, Schaffner adds.
As summer holiday travel peaks and people increasingly gather indoors in air conditioning to escape the heat waves, COVID-19 is expected to continue to surge. “If the virus hasn’t hit your community yet, it probably will after all the Fourth of July travel,” Schaffner says.
What is LB.1?
LB.1 is part of the omicron family — the newest member of the family, so to speak, Schaffner explains. The LB.1 subvariant is an offshoot of JN.1, which dominated for most of the winter and spring.
“The LB.1 gene is closely related to the FLiRT variants, but it has a few unique mutations in different parts of the Spike protein,” Pekosz explains. These include key mutations that affect the LB.1 gene’s ability to evade immunity.
“We have seen mutations like this before with 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 the LB.1 variant is part of an ongoing trend, experts point out. The SARS-CoV-2 virus mutates and gives rise to new variants, more able to escape immunity and supplant other strains until a new variant emerges.
In the United States, more than 97% of people have natural or vaccine-induced antibodies to COVID-19, but that number fades over time, according to the CDC.
Is LB.1 more transmissible?
The Omicron gene subvariants are characterized by their high transmissibility. “LB.1 is very contagious and spreads very easily,” explains Schaffner.
How does the LB.1 strain compare to other new strains? “It’s too early to tell, but so far there’s no indication that it’s more transmissible than the FLiRT variants,” Dr. Bernard Camins, medical director of infection prevention at Mount Sinai Health System, told TODAY.com.
“It may be more likely to evade immunity acquired through infection or vaccine, but it has not been shown to be more dangerous than previous subvariants,” Camins says.
The recent surge in cases appears to be driven by a combination of new variants, including LB.1 and the FLiRT strains. However, declining testing and genomic surveillance are making it difficult to accurately track the virus. “It’s becoming increasingly difficult for us to get a clear picture of how quickly a variant is spreading,” Pekosz says.
What are the symptoms of LB.1?
LB.1 does not appear to cause any distinct or new symptoms and there is no evidence that it produces more severe disease, experts say.
Symptoms of LB.1 are very similar to those caused by FLiRT variants, which include:
According to Schaffner, the new strains generally appear to produce milder infections.
“Some people may still experience severe symptoms, severe enough to require hospitalization,” Camins says — namely, high-risk groups: people aged 65 and older, people with underlying health conditions and people who are immunocompromised.
Emergency room visits increased 23% last week but remain relatively low, and hospitalization rates remain stable, according to the CDC.
Antivirals such as Paxlovid are effective against LB.1 and other recent strains, Schaffner notes.
Do vaccines protect against LB.1?
“The current vaccine will provide protection against severe disease,” Schaffner says. Currently, the updated 2023-2024 COVID-19 booster vaccine targeting the XXB.1.5 strain is still available. The CDC recommends that high-risk groups receive an additional dose.
The updated vaccine for 2024-2025, which will be marketed this fall, should also offer protection, experts point out. “LB.1 is closely related to KP.2, which seems to be the strain targeted by the vaccine for the upcoming fall season,” Pekosz says.
“Previous data shows that even if the vaccine doesn’t match exactly what’s circulating, there is cross-reactivity that gives you some protection,” Camins says.
Experts are encouraging everyone who is eligible to get vaccinated this fall against COVID-19, version 2024-2025.
Guidelines on testing and isolation in 2024
If you develop symptoms of COVID-19 or are exposed to it, get tested, experts say. Testing is an important tool to protect yourself and prevent the spread of the virus.
Both PCR and antigen tests will detect LB.1 and other new variants, Camins notes. If you use an antigen test, follow FDA recommendations to avoid a false negative result.
The CDC recommends that people who test positive stay home while sick and avoid contact with others. Current isolation guidelines state that people can only return to their normal activities after they are fever-free (without medication). And symptoms have been improving for at least 24 hours.
“If you are in a high-risk group and test positive for COVID-19, we will give you Paxlovid to prevent severe illness,” Schaffner says.
How to protect yourself 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 with COVID-19 vaccines.
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Wear a mask in crowded indoor spaces.
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Practice good hand hygiene.
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Cover your cough and sneeze.
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Improve ventilation.
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Practice social distancing.
This article was originally published on TODAY.com