As COVID-19 cases surge across the U.S., a new variant known as LB.1 is gaining attention. This highly contagious omicron subvariant, along with the rapidly spreading FLiRT strains, is contributing to an expected summer wave, according to health experts.
In recent weeks, the nation has experienced increases in test positivity rates and emergency room visits. With millions of people traveling for summer vacations and seeking indoor refuge from heat waves, experts predict cases will continue to climb.
LB.1 is currently the third most common COVID-19 variant in the country, closely following the FLiRT strains, including the dominant KP.3.1.1 and KP.3 variants, as reported by the U.S. Centers for Disease Control and Prevention (CDC).
LB.1 is a derivative of the JN.1 variant with new mutations that distinguish it from previous strains. Since late May, the proportion of cases attributed to LB.1 has doubled, according to CDC data.
While hospitalizations and deaths remain lower compared to earlier pandemic waves, the SARS-CoV-2 virus is still spreading rapidly, causing widespread illness.
In the past month, several high-profile individuals, including President Joe Biden, U.S. Health & Human Services Secretary Xavier Becerra, and over 40 athletes at the Paris Olympics, have tested positive for COVID-19.
So, how severe is this year's summer wave? Are these new variants causing different symptoms? And what should you do if you get sick? Here's what we know about the current COVID-19 trends in the U.S. and the emerging LB.1 strain.
Is There a Summer Surge?
COVID-19 cases have been rising in nearly all regions of the U.S. The CDC estimates that as of July 30, cases are increasing in 32 states, stable in eight, and declining in just three.
Test positivity reached 17.6% during the week ending August 3, up from about 15% in the previous two weeks. For context, last winter’s peak was 12%. A CDC map indicates that test positivity rates are highest in the Southern region.
Nationwide, viral activity in wastewater is classified as "very high," with 44 states reporting "high" or "very high" levels. (The CDC no longer tracks the total number of new COVID-19 cases.)
Additionally, COVID-related emergency room visits have increased by 4% over the past week, and hospitalizations are on the rise, according to the CDC.
All signs point to an ongoing summer COVID-19 wave — though it's still too early to predict how trends will develop, says Dr. Andrew Pekosz, a virologist at Johns Hopkins University.
"When I look at the U.S. map of test positivity, I see a lot of variability," Pekosz notes, adding that reduced reporting of COVID-19 cases has made it harder to gauge the speed of these changes.
Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, adds that this recent spike in cases was anticipated. "Right now, there isn't a part of the country that's unaffected by this," Schaffner says. While COVID-19 has caused summer waves in the past, these tend to be less severe than winter surges.
Although COVID-19 hospitalizations remain lower than last winter, they have increased significantly in the last two weeks, Schaffner observes.
As summer travel hits its peak and people increasingly gather indoors to escape ongoing heat waves, COVID-19 cases are expected to keep rising.
"There are plenty of opportunities for the virus to spread from person to person, and when it does, it will find those at higher risk for severe disease, contributing to the rise in hospitalizations we're seeing," Schaffner adds.
What Is LB.1?
LB.1 is the latest member of the omicron family, says Schaffner. It’s a direct descendant of the JN.1 variant, which was dominant throughout most of the winter and spring.
"LB.1 is closely related to the FLiRT variants but carries unique mutations in different parts of the spike protein," Pekosz explains. These mutations influence LB.1's ability to evade immunity.
"We’ve observed similar mutations in other variants, including JN.1, but they don't seem to indicate that the virus has drastically changed," Pekosz adds.
The emergence of LB.1 continues the ongoing trend of the SARS-CoV-2 virus mutating to give rise to new variants that are better at evading immunity and outcompeting older strains.
While over 97% of Americans have some form of immunity from prior infection or vaccination, this protection fades over time, according to the CDC.
Is LB.1 More Contagious?
A defining trait of omicron subvariants is their high transmissibility. "LB.1 is highly contagious and spreading quickly," Schaffner notes.
Comparing LB.1 to other new strains, "It's too soon to say definitively, but there’s no indication yet that it’s more transmissible than the FLiRT variants," says Dr. Bernard Camins, medical director of infection prevention at Mount Sinai Health System.
"It might be more likely to escape immunity from previous infection or vaccination, but it hasn't shown that it’s more dangerous than earlier subvariants," Camins adds.
The recent spike in cases seems to be driven by a mix of new variants, including LB.1 and the FLiRT strains. However, with reduced genomic surveillance, tracking the virus accurately has become more challenging. "It’s getting harder to gauge how quickly a variant is spreading," Pekosz says.
What Are the Symptoms of LB.1?
LB.1 doesn’t appear to cause any new or unique symptoms, nor is there evidence that it leads to more severe illness, experts say.
The symptoms of LB.1 are similar to those caused by the FLiRT variants, which include:
- Sore throat
- Cough
- Fatigue
- Congestion
- Runny nose
- Fever or chills
- Headache
- Muscle aches
- Loss of taste or smell
- Nausea or vomiting
- Diarrhea
The newer strains generally seem to produce milder infections than those in previous years, says Schaffner. However, COVID-19 can still cause a wide range of symptoms.
“Some people experience a classic sore throat, runny nose, cough, and low-grade fever,” says Dr. Paul Sax, clinical director of the division of infectious diseases at Brigham and Women’s Hospital. “In others, it’s mostly nausea and diarrhea with minimal respiratory symptoms. It can vary widely.”
“Some people can still experience severe symptoms, leading to hospitalization," Camins adds — particularly high-risk groups like those over 65, people with underlying medical conditions, and immunocompromised individuals.
“There’s no single symptom that definitively indicates COVID-19,” says Dr. Steven Furr, a family physician in Jackson, Alabama. "Without testing, we can’t be certain."
Antivirals like Paxlovid are effective against LB.1 and other recent strains, Schaffner notes.
Do Vaccines Protect Against LB.1?
"The current vaccine offers protection against severe disease," Schaffner says. The updated 2023–2024 COVID-19 booster, targeting the XXB.1.5 strain, is still available, and the CDC recommends it for high-risk groups needing an additional dose.
The upcoming 2024–2025 vaccine, set for release this fall, is also expected to provide protection. "LB.1 is closely related to KP.2, which appears to be the strain targeted in this fall's vaccine," Pekosz says.
"Even if the vaccine doesn't match the circulating strain exactly, there’s enough cross-reactivity to offer protection," Camins explains.
Experts encourage everyone eligible to get the updated 2024–2025 COVID-19 vaccine this fall.
COVID Guidelines 2024
If you develop COVID-19 symptoms or have been exposed, testing is crucial to protect yourself and others.
PCR and antigen tests will detect LB.1 and other new variants, Camins notes. If using an antigen test, follow FDA guidelines to reduce the risk of a false negative.
The CDC recommends staying home while sick if you test positive and avoiding contact with others. Previously, the agency advised isolating for at least five days after a positive test, but as of March 2024, guidelines now suggest resuming normal activities once you've been fever-free for at least 24 hours without medication and your symptoms have improved.
"If you're in a high-risk group and test positive for COVID-19, Paxlovid can help prevent severe illness," Schaffner says.
Protecting Against the LB.1 Variant
As COVID-19 cases rise this summer, consider these additional precautions to protect yourself and others, as recommended by the CDC:
- Stay up to date with COVID-19 vaccinations.
- Wear a mask in crowded indoor spaces.
- Practice good hand hygiene.
- Cover your mouth and nose when coughing or sneezing.
- Improve ventilation in indoor spaces.
- Maintain social distancing.