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What you need to know about BA.2.86, the new ‘highly mutated’ COVID variant

The new, highly mutated BA.2.86 "Pirola" variant is spreading. Here's what we know about its transmissibility, ability to escape immunity, and boosters this fall.

As the United States faces an end-of-summer coronavirus surge and gears up for respiratory virus season this fall, all eyes are on a new, highly mutated COVID-19 variant called BA.2.86, or "Pirola."

Health authorities are closely monitoring the variant, which has been detected in humans and wastewater samples in the U.S. and several other countries.

Fewer than 100 cases of BA.2.86 have been reported so far, and the new variant does not appear to be driving the recent increase in cases and hospitalizations in the U.S., experts told NBC News.

However, Pirola has set off alarm bells for some scientists due to its large number of mutations, which differentiate it from earlier omicron subvariants that have gained dominance since 2021.

According to the U.S. Centers for Disease Control and Prevention, BA.2.86 is notable because it has multiple genetic differences compared to previous versions of the virus, and it has been detected in several locations in a short amount of time, the agency said in an update on BA.2.86 on Aug. 30.

In its initial risk assessment of the variant, the CDC said it BA.2.86 may be more capable of bypassing existing immunity from COVID-19 vaccines or prior infection, but there is no evidence it causes more severe illness.

The concern about Pirola's ability to cause breakthrough infections comes as vaccine manufacturers race to release new boosters for the fall.

However, Moderna's updated COVID-19 vaccine appears to generate a strong immune response against BA.2.86, the drugmaker announced in a release on Wednesday.

Additional data from lab studies suggest the variant may be less contagious and immune-evasive than previously feared, NBC News reported.

The World Health Organization first classified BA.2.86 as a “variant under monitoring” on Aug. 17 because of its “large number of mutations identified."

As of Sep. 6, the BA.2.86 variant has been linked to 60 cases in 11 countries, per the global virus database GISAID. These include United States, Canada, Denmark, Sweden, Portugal, Israel, the United Kingdom, South Africa, Thailand, Australia and France. BA.2.86 has also been detected in wastewater samples in additional countries, the CDC said.

Early data show BA.2.86 has 34 more mutations in its spike protein than BA.2, which drove a COVID surge in 2022, and an additional 36 more mutations than XBB.1, which rapidly took over the U.S. in early 2023, according to an Aug. 24 paper in The BMJ.

It's unclear whether BA.2.86 will cause a surge in infections this fall, and the current rise in cases and hospitalizations in the U.S. is likely being driven by omicron XBB lineage viruses, the CDC said.

As scientists race to investigate BA.2.86 and whether it could become a global threat, there's no reason to panic, experts say.

Here's what experts know so far about BA.2.86, aka Pirola, the symptoms it's causing, its ability to spread and how it could impact COVID vaccine boosters this fall.

What is BA.2.86?

BA.2.86, which health experts dubbed “Pirola” on social media, was first detected in late July. It appears to have descended from the omicron BA.2 sublineage, which caused surges of the virus in early 2022, Andrew Pekosz, Ph.D., virologist at Johns Hopkins University, tells

“The critical thing about this variant (BA.2.86) is that it has a whole host of mutations compared to some of the omicron variants that emerged about two years ago,” says Pekosz.

The mutations or changes in the virus sequence can affect how contagious a virus is, how well it responds to treatment and how severely it affects people, per the CDC.

“It represents a highly mutated form of SARS-CoV-2,” says Pekosz — in other words, BA.2.86 looks very different from the prevailing omicron XBB subvariants circulating.

What are the symptoms of BA.2.86?

Right now, "there's no data on symptoms associated with infection because the case numbers are just too small," Pekosz says.

In its risk assessment of BA.2.86, the CDC said "at this point, there is no evidence that this variant is causing more severe illness," but this may change as additional scientific data comes in.

Common symptoms of other COVID-19 variants and subvariants include:

  • Cough
  • Sore throat
  • Runny nose
  • Sneezing
  • Fatigue
  • Headache
  • Muscle aches
  • Altered sense of smell

Based on what the CDC knows now about BA.2.86, existing tests and medications used to treat COVID-19 "appear to be effective with this variant," the agency said.

Where is BA.2.86 spreading?

As of Sep. 6, BA.2.86 has been linked to 14 cases in South Africa, 12 in Denmark, eight in the United Kingdom, five in Sweden, five in Thailand, five in the United States, three in France, three in Israel, two in Canada, two in Portugal, and one in Australia, according to GISAID.

The variant has been detected in at least four states in the U.S. in either people or wastewater, the CDC said. Human cases were documented in Michigan, Virginia and Ohio, and BA.2.86 has been detected in wastewater in New York City. GISAID also reported a case in Texas.

“The variant is probably spreading much more broadly than we’ve detected so far,” says Pekosz, adding that a lack of testing and sequencing is likely causing a delay in reporting.

Right now, the EG.5 or Eris subvariant, a descendant of the omicron XBB sublineage, accounts for the largest proportion, 21.5%, of COVID-19 infections in the U.S., according to the latest estimates from the CDC.

After EG.5, the next most common subvariant circulating in the U.S. is another omicron XBB descendant, FL.1.5.1, followed by the closely related XBB.1.16.6 and XBB.1.16 (or “Arcturus”) variants, per CDC data as of Sep. 2.

Globally, EG.5 and XBB.1.16 are the most prevalent COVID-19 strains, according to the latest WHO COVID-19 situation report.

Is BA.2.86 more transmissible?

Right now, it's too early to tell whether BA.2.86 is more transmissible than other variants, says Pekosz. "It's impossible to gauge anything about transmissibility or disease severity from that (small number of cases)," he adds.

However, based on what we know about the genetic sequence of BA.2.86 and the mutations in its spike protein, the variant will likely be able to escape preexisting immunity to COVID-19, Pekosz says.

The CDC echoed this in its BA.2.86 risk assessment, which stated that the variant could be more capable of causing infection in people who previously had COVID-19 or got vaccinated.

"Most of the mutations that we find in the spike protein are probably going to affect the ability of antibodies to bind and neutralize the virus," Pekosz adds.

In other words, BA.2.86 could escape not only immunity from vaccination or prior infection up until this point, but also vaccine-induced immunity from the coming fall vaccine, Pekosz adds.

"That's why this variant is very concerning to us from a scientific standpoint," he adds. "We need more sequences and cases to understand the variant's transmissibility."

According to the CDC, laboratories are currently researching the antibody neutralization of BA.2.86 to better understand how the immune system may interact with the virus.

Will BA.2.86 cause a surge in cases?

“We really don’t know if BA.2.86 will lead to increased numbers of cases,” Pekosz says. "The sequence can’t tell us how much disease the virus will cause, nor can it tell us how well it’s spreading," says Pekosz. Only time and more data will tell.

However, the BA.2.86 does not appear to be behind the recent summer COVID surge around the country. Over the last month, there has been an increase in cases and hospitalizations in the U.S., likely driven by a combination of the new EG.5 subvariant and other omicron variants circulating, previously reported.

In the last two weeks, there has been a 25.3% increase in the number of average daily COVID-19 hospitalizations, according to an NBC News analysis.

In mid-August, weekly COVID-19 hospitalizations were the highest they had been since April 2023. However, the death rate due to COVID is still decreasing week by week, per CDC data.

Despite the recent increases, the absolute number of cases and hospitalizations are relatively low compared to surges in past years, experts note.

How will BA.2.86 affect boosters this fall?

Vaccine manufacturers are currently working on an updated COVID-19 booster targeting the XBB.1.5 subvariant, which was dominant through most of 2023.

No shot has been approved yet, but experts anticipate the U.S. Food and Drug Administration will authorize the updated boosters in the coming weeks and they will be available in mid to late September, previously reported.

Previously, the reactivity of new boosters to BA.2.86 was predicted to be low, according to Pekosz. However, recent data has suggested that the vaccines set to roll out this fall may provide more protection than initially thought.

Moderna said that clinical trial data confirmed its updated vaccine "showed an 8.7 to 11-fold increase in neutralizing antibodies against circulating variants, including BA.2.86, EG.5, and FL.1.5.1."

The boosters will be well-matched to the other strains currently making people sick, says Pekosz — and they will still be effective at reducing severe disease and hospitalization, per the CDC — so it's important for people to stay up to date with COVID vaccines.

The CDC has not yet released any firm guidance around booster doses for the fall. When the agency does make recommendations about who should get the booster this fall, the experts anticipate it will be for high-risk individuals. These include people over the age of 65, those with underlying health conditions and the immunocompromised.

In addition to vaccination, people can protect themselves against COVID-19 by taking precautions such as wearing a mask, practicing social distancing, avoiding sick people and maintaining good hand hygiene.