A new omicron subvariant, XBB.1.16, is spreading in the United States, and some doctors are reporting that it may be causing unusual symptoms. The fast-growing COVID-19 variant already has a nickname on social media: Arcturus, named after the brightest star in the northern celestial hemisphere.
As the Biden administration prepares to end the federal COVID-19 public health emergency in the U.S. on May 11, some experts are watching out for a potential surge in cases driven by the highly contagious "Arcturus" subvariant.
Last week, XBB.1.16 accounted for an estimated 10% of cases in the U.S. compared to about 6% the previous week, according to the latest data from the U.S. Centers for Disease Control and Prevention.
"It’s now being transmitted widely and is the second most common variant we’re seeing in the United States," Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, tells TODAY.com.
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What exactly is the XBB.1.16 Arcturus subvariant, how transmissible is it compared to other omicron subvariants, and which symptoms should people be looking out for? We spoke to experts to find out.
What is XBB.1.16, aka Arcturus?
XBB.1.16 was first reported to the World Health Organization in January 2023. On April 17, WHO designated XBB.1.16 a "variant of interest." It has been detected in 33 countries so far, including the United States, but right now it is most prevalent in India.
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XBB.1.16 is a recombinant, or a hybrid of two BA.2 sublineages, according to the WHO. “It’s part of the omicron extended family, if you will,” says Schaffner.
"It looks very much like XBB.1.5, which is the dominant variant in the U.S. and has been the dominant variant here and in many other countries for some time," Dr. Andy Pekosz, a virologist at Johns Hopkins University, tells TODAY.com. Like Arcturus, XBB.1.5 is also considered a variant of interest, per the WHO, and has been circulating widely since last fall.
The WHO considers something a "variant of interest" if it meets two criteria: It's circulating widely, and it has suspected or known mutations that cause significant changes. In the case of XBB.1.16, its new mutations may impact its ability to spread and evade immunity, experts say.
Is Arcturus more transmissible than other variants?
"It seems to have a mutation that could make it even more transmissible than some of the other omicron strains. ... It spreads very readily. It's highly contagious," says Schaffner. Because of this, it may be able to "outrun" or outcompete other variants, he adds.
“It (also) has at least two mutations in the spike proteins that will probably cause it to evade some amount of vaccine-induced immunity or immunity-induced by infection with XBB.1.5,” says Pekosz. This means the variant is better at dodging antibodies the body has produced to help fight off the virus, TODAY.com previously reported.
The good news? "There is no indication at the moment that it’s causing more severe disease ... and it’s not driving more people into the hospitals," says Schaffner. The WHO said it is "carefully monitoring" for signs of increased severity in a risk assessment of XBB.1.16.
“Its ability to cause severe disease appears to be similar to prior omicron variants,” Dr. Albert Ko, an infectious disease physician and professor at Yale School of Public Health, tells TODAY.com.
While these mutations may give XBB.1.16 an advantage in terms of its ability to spread in the population and escape immunity, says Ko, there is not enough evidence yet to know the exact severity of illness it causes.
XBB.1.16 Arcturus symptoms
According to Schaffner, there have been “a slew of anecdotal reports" from doctors that the XBB.1.16 variant may be causing a few distinct and unusual symptoms, especially among children.
“One is that it tends to produce a bit more fever," says Schaffner. "That’s interesting because many COVID-19 infections (now) produce little, if any, fever.” Another potential odd XBB.1.16 symptom is conjunctivitis, or pink eye, he adds.
Otherwise, the symptoms of XBB.1.16 seem to be similar to those caused by other omicron variants, which include:
- Sore throat
- Runny nose
- Sneezing
- Cough
- Headache
- Fatigue
- Muscle aches
- Altered sense of smell
If you or your child has any of these symptoms, the experts recommend getting tested for COVID-19.
Does Arcturus cause pinkeye?
Doctors have anecdotally observed that Artcturus, or XBB.1.16, may be causing pinkeye, or conjunctivitis, experts tell TODAY.com.
"The most distinct aspect of (Arcturus) is that it has a tendency to produce inflammation of the external part of the eye and eyelids,” says Schaffner, adding that this can cause itching, redness, swelling and tearing or discharge that lasts for about a week.
Pink eye is most often caused by a viral infection, such as adenovirus, but it can also be caused by bacterial infections, allergies or injuries, per the Mayo Clinic. It is highly contagious.
“If you touch the pinkeye infection, you can get (it) on your hands and transmit it to someone else,” says Schaffner.
COVID-19 spreads through respiratory droplets from an infected person, which can be breathed in or enter through the mouth, nose or eyes, per the CDC.
Fortunately, the pinkeye observed in people with XBB.1.16 appears to run its conventional course and resolve in about a week, says Schaffner. “I haven’t heard of any long-term consequences (to the eyes). ... So far, this is something distinctive that's an annoyance."
Why this subvariant might invoke an inflammatory response in the eyes is not known, says Schaffner.
The experts emphasize that we're still learning about XBB.1.16 as it continues to spread.
“I haven’t seen anything firm to suggest that these (symptoms) are more than anecdotal right now," says Pekosz. "I think it requires more data before we can make a firm conclusion.”
How concerned should people be about Arcturus, aka XBB.1.16?
“There’s nothing particularly worrisome about this variant outside of a few mutations that may make it a little bit more resistant to immunity,” says Pekosz. There isn't any clear indicator that the variant is targeting specific populations yet, he adds.
Speculating, Pekosz says he wouldn’t expect XBB.1.16 to cause a massive surge in breakthrough infections because it’s still very closely related to the XBB.1.5 variant.
"However, everywhere we see 1.16, it does seem to start increasing at a pretty fast rate,” says Pekosz, adding that it is "something to watch."
XBB.1.16 is already taking off in the the U.S. and will likely climb, says Ko, and whenever cases go up, there is a potential for COVID-19 hospitalizations and deaths to go up, as well. But based on the data we have so far, that isn't happening yet, the experts note.
One caveat, Pekosz notes, is that the level of testing has decreased, and fewer cases are being sequenced compared to even just a year ago. "We’re at a very different stage of the pandemic, and many labs are no longer routinely sequencing large numbers of COVID-19 cases," says Pekosz, adding that this makes it harder to accurately track new variants.
Although the national COVID-19 public health emergency is ending soon, COVID-19 is not over, the experts note. "We have to remember that 200 to 250 die every day of COVID in the United States," says Schaffner. "I hope this motivates us to keep up our guard," he adds.
How to protect yourself against XBB.1.16
The best way to protect yourself from any subvariant is to stay up to date on your COVID-19 vaccinations, the experts emphasize.
Even if XBB.1.16 is better at evading immunity from the vaccine, it can still provide some protection, the experts note. "The current recommended vaccines are effective at preventing serious disease for all of the omicron variants," says Schaffner, adding that it seems like they will do the same for XBB.1.16.
Parents who are concerned about the potential new XBB.1.16 symptoms should vaccinate their children, the experts note. Although COVID-19 is one of the 10 leading causes of death in children in the U.S., says Schaffner, there is still a lot of hesitation and reluctance to get kids vaccinated.
"The vaccines are safe, they're effective, and they’re underutilized," Schaffner adds. Precautions like washing your hands, avoiding people who are sick and wearing a mask in crowded, indoor spaces can also help curb transmission.
Do people need another COVID-19 booster?
The CDC has backed a second round of reformulated bivalent booster shots for adults over 65 and those with weakened immune systems, which will be available in the fall, NBC News reported.
The experts encourage everyone who is eligible to get the updated booster shot. Given that the immunity from vaccines is temporary and the virus is changing, says Schaffner, people will need to be periodically revaccinated.
"They're starting to do this the way we do routinely with our influenza vaccine, which we update on an annual basis," says Schaffner, adding that annual boosters could become a norm in the future, especially for higher-risk groups.
This story first appeared on TODAY.com. More from TODAY:
