LB.1 is the latest COVID-19 subvariant to hit the headlines as it circulates in the United States. This highly contagious strain, which emerged shortly after the variants FLiRTincluding KP.3 and KP.2, are causing an increasing proportion of infections.
As the number of cases and emergency room visits at hospitals across the country rise, some fear a summer surge in infections could occur.
According to the latest data from the Centers for Disease Control and Prevention (CDC), LB.1 is the third most widespread COVID-19 variant in the country right now, far behind the dominant KP.3 and KP.2.
As of June 22, the KP.3 variant was estimated to account for 33% of cases in the United States. The next most common variant is KP.2, which accounts for about 21% of cases, followed by LB.1, which drives 17.5% of cases.
Since late May, the proportion of cases caused by LB.1 has more than doubled, according to CDC data. According to some experts, this new variant could be on track to overtake the FLiRT variants in the coming weeks.
Although global 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 surge?
Here’s what we know so far about summer trends for COVID-19 and the new LB.1 variant.
Is there a summer rebound?
In recent weeks, cases have been increasing in most states across the country, especially in the West. The CDC estimates that COVID-19 cases are increasing or likely to increase in 44 states, are stable or uncertain in 5 states, and are declining in Hawaii.
“As of today (early July), we are not seeing any major increases in cases across the country, but cases are increasing in some places and stable in others,” Andrew Pekosz, a virologist at Johns Hopkins University, told .com. The country is likely at the beginning of a surge, Pekosz added, but it is still too early to tell how COVID-19 trends will play out in the summer.
According to the CDC, the positive test rate was 8% as of June 22, up 1.4% from the previous week but lower than the winter peak of 12%. A CDC map shows positive test results are highest in California and the Southwest.
Viral activity in wastewater is “low” nationwide, while it was “high” or “very high” for most of the winter. (The CDC no longer tracks total numbers of new COVID-19 cases in the United States.)
According to William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center, what we’re seeing now is more of an expected “bump.” Unlike the flu, COVID-19 is not seasonal and continues to spread in the summer, but these spikes are much less significant than winter surges, Schaffner adds.
As summer holiday travel increases and people increasingly coop up in air conditioning to escape heat waves, COVID-19 cases are expected to continue to rise. “If it hasn’t already gone up in your community, it probably will after all the Fourth of July travel,” Schaffner says.
What is the LB.1 variant?
LB.1 is part of the omicron family, the last 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 it has a couple of unique mutations in different parts of the spike protein,” Pekosz says. These include key mutations that affect LB.1’s ability to evade immunity.
“We have seen mutations like this before with other variants (including JN.1). They do not seem to be particularly worrying or a sign that the virus has changed dramatically,” Pekosz adds.
Experts say the emergence of LB.1 follows a current trend. 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.
In the United States, more than 97% of people have natural or vaccine-induced antibodies to COVID-19, but these fade over time, according to the CDC.
Is LB.1 more transmissible?
One characteristic of the omicron subvariants is that they are highly transmissible. “LB.1 is highly contagious and spreads very easily,” says Schaffner.
How does LB.1 compare to other new strains? “It’s too early to tell, but there’s no indication at this point that it’s more transmissible than the FLiRT variants,” Bernard Camins, medical director of infection prevention at Mount Sinai Health System, tells .com.
“It may be more likely to escape immunity acquired through infection or vaccination, 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 FLiRT strains. However, declining testing and genomic surveillance make it difficult to accurately track the virus. “It’s becoming harder and harder for us to get a good idea of how quickly a variant is increasing,” Pekosz says.
What are the symptoms of LB.1?
LB.1 does not appear to cause any different or new symptoms and there is no evidence that it causes more severe disease, experts stress.
Symptoms of LB.1 are very similar to those caused by the FLiRT variants, including:
- Sore throat
- Cough
- Fatigue
- Congestion
- Runny nose
- Fever or chills
- Headache
- Muscle pains
- New loss of taste or smell
- Nausea or vomiting
- Diarrhea
Newer strains appear to produce generally milder infections, Schaffner says. But COVID can still cause a broad spectrum of illness.
“Some people have a very classic sore throat, runny nose, cough and low-grade fever,” Paul Sax, clinical director of the division of infectious diseases at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School, told NBC News. “In others, it’s 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 hospitalize them,” Camins tells .com. This is the case for high-risk groups such as people 65 years of age or older, people with underlying medical conditions and immunocompromised individuals.
“There is no symptom right now that tells us, ‘You probably have COVID,’” 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.”
Emergency room visits for COVID have increased 23% in the past 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 offers protection against severe disease,” Schaffner says. At this time, an updated booster shot for 2023-2024 against the XXB.1.5 strain is still available. The CDC recommends that high-risk groups receive an additional dose.
The updated 2024-2025 vaccine due to be released this fall is also expected to offer protection, experts stress. “LB.1 is closely related to KP.2, which looks set to be the vaccine target strain for this upcoming fall season,” says Pekosz.
“Preliminary data show that, although the vaccine does not exactly match what is circulating, there is cross-reactivity that provides some protection,” says Camins.
Experts encourage everyone who is eligible to get vaccinated against COVID-19 this fall.
COVID Guidelines 2024
If you have symptoms of COVID-19 or have had an exposure, get tested, experts stress. Testing is an important tool to protect yourself and prevent the spread of the virus.
PCR and antigen tests will detect LB.1 and other new variants, Camins said. 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 they are sick and avoid contact with others. The agency used to recommend isolating yourself from others for at least five days after testing positive. But in March 2024, its isolation guidelines changed to say that people can return to normal activities after they have been fever-free without medication and symptoms have improved 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 explains.
How to protect yourself against the LB.1 variant
As COVID-19 cases continue to rise this summer, consider taking additional steps to protect yourself and others.
CDC recommends:
- Stay up to date on COVID-19 vaccinations.
- Wear a mask in closed and crowded places.
- Clean your hands well.
- Cover your mouth and nose when you cough or sneeze.
- Improve ventilation.
- Practice social distancing.
