New coronavirus subvariant Arcturus is now in L.A. Is there reason to worry?

Pedestrians walk in downtown Los Angeles.
It’s unclear how many Arcturus cases have appeared in California. At least three have been identified in L.A. County.
(Genaro Molina / Los Angeles Times)

Los Angeles County has identified its first cases of an emerging Omicron coronavirus subvariant dubbed Arcturus, a strain global health authorities are watching closely as it has been linked to an upswing in cases in India.

Officially designated XBB.1.16, the subvariant also has attracted attention after anecdotal reports linking it to what has been a rare COVID-19 symptom: pink eye.

However, it remains unclear whether this symptom is more pronounced in Arcturus than earlier Omicron strains. The latest subvariant has not been shown to cause more severe illness.


It is possible, however, that Arcturus is even more infectious than the dominant coronavirus strain in the U.S., XBB.1.5. Though that probably isn’t enough to trigger another surge in cases, any uptick in transmission heightens the risk for vulnerable individuals — and, health officials say, reinforces the value of protective measures.

“When we hear messages that ‘The pandemic’s over,’ or that ‘COVID-19 is now endemic,’ it gives the impression that people no longer need to be aware of its impact or take any steps to protect themselves and others,” L.A. County Public Health Director Barbara Ferrer said at a briefing Thursday. “Just the fact that we’re seeing new strains with possible different symptoms should remind us that COVID continues to evolve.”

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It’s unclear how many Arcturus cases have appeared in California. At least three have been identified in L.A. County, according to Ferrer.

Because Arcturus is an Omicron subvariant, Ferrer said it’s likely that current vaccines and therapeutic drugs will be effective on this strain.

Still, she said in an interview, “With any new mutation that crowds out what’s already there ... they’re likely to be able to more easily pass on infection. So you could see a bump.”

The unofficial moniker Arcturus is Latin and originated from the Greek word arktouros, which means guardian or watcher of the bear. It’s also the name of the fourth-brightest star in the night sky.


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It’s now believed to be the second-most common coronavirus strain in circulation nationwide, accounting for an estimated 7.2% of cases, according to data from the U.S. Centers for Disease Control and Prevention. That’s up notably from its estimated share of 2.1% over the week ending April 1.

XBB.1.5, meanwhile, comprised an estimated 78% of new cases nationwide over the week ending Saturday.

For the southwestern U.S. — including California, Arizona, Nevada, Hawaii and the Pacific territories — Arcturus accounted for an estimated 9.8% of cases, up from an estimated 2.6% over the week ending April 1.

“This is one to watch. It has been in circulation for a few months,” Maria Van Kerkhove, the World Health Organization’s technical lead on COVID-19, said recently.

In India, authorities say Arcturus has begun replacing older versions of the coronavirus.

“From early reports in India and more than 20 countries, it doesn’t seem it’s proportionately sending more people to the hospital. But it is causing an increase in cases,” said Dr. Peter Chin-Hong, an infectious-diseases expert at UC San Francisco. With case rates in the U.S. at relatively low levels, “if you give a little bit more edge to a particular subvariant, it will cause an increase in cases.”

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There have also been anecdotal reports of pink eye, or conjunctivitis, in coronavirus-infected people in India, particularly in children.


Before Arcturus, pink eye had been associated as a symptom in 1% to 3% of coronavirus cases, according to Chin-Hong and Ferrer.

If left untreated, pink eye can go beyond mere pain and itchiness to damage the cornea, Ferrer said.

“It’s always been a side effect [of COVID-19], although very rare,” she said. “Untreated, it can actually cause more damage to people’s eyes. If you have pink eye — for whatever reason — it needs to be treated.”

Pink eye can be caused by other viruses and bacteria. According to the National Eye Institute, “It’s one of the most common eye problems for both children and adults.”

“Just because you have pink eye doesn’t necessarily mean you have COVID. You should go and get tested, particularly if you have some other symptoms,” Ferrer said.

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According to the National Eye Institute, people who are around someone with pink eye should wash their hands often with soap and water or use hand sanitizer with alcohol in it.


Always wash your hands before touching your eyes and after you touch a person with pink eye or something they have used.

“Don’t share personal items that the person with pink eye has used — including pillows, towels, makeup or glasses,” the institute said.

People with pink eye who wear contact lenses should consult with their eye doctor on how to clean, store and replace their lenses. They should also throw away any lenses, solution and cases they used while they had pink eye. The same goes for face or eye makeup, as well as makeup brushes or sponges.

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Coronavirus cases are relatively stable at lower levels in California. As of Thursday, there was no sign of an increase in coronavirus levels in L.A. County wastewater or in officially reported coronavirus cases.

“But it’s always possible: I would anticipate that if we do see an increase, my hope would be it would be relatively small,” Ferrer said.

For the most recent week, L.A. County reported 44 COVID-19 deaths.

“Compared to other points in the pandemic, we are seeing much lower numbers of people dying,” Ferrer said Thursday. “However, these deaths are not insignificant. And COVID continues to be one of the leading causes of death in L.A. County and across the country.”


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In general, people at higher risk of dying are older and not up to date on their COVID-19 vaccinations and boosters, or haven’t been treated with anti-COVID drugs, experts say.

Just 42% of eligible L.A. County seniors have received the updated vaccine since it became available in September.

Though many believe the time of hospitals being overwhelmed by COVID-19 patients is over, any bump in cases could still lead to an increase in hospitalizations, underscoring the importance of staying up to date on vaccines (particularly for older people) and asking for therapeutic anti-COVID drugs such as Paxlovid and molnupiravir — which are free — should you become infected.

Data continue to mount that the updated COVID-19 vaccine saves lives and reduces risk of hospitalization. L.A. County residents who got the updated booster were half as likely to die compared with people who were vaccinated but had not received the updated booster, according to data for the 90-day period that ended March 27.

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People who got the updated booster were roughly one-tenth as likely to die compared with unvaccinated L.A. County residents. Immunity from surviving a past infection alone doesn’t reliably provide the same kind of protection as vaccines.

“This data illustrates the very real protection offered by the bivalent booster, even against the newer variants that are circulating now,” Ferrer said.


She also encouraged infected residents to take anti-COVID drugs such as Paxlovid when prescribed, even if they don’t feel seriously ill.

“Paxlovid has a really good track record at reducing severe illness. And the one thing you don’t want to do is wait until you have severe illness before you take it, if you’re in a higher-risk category,” Ferrer said.

Studies suggest that vaccination and Paxlovid also reduce the risk of long COVID.

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Chin-Hong said he suspected the rise in the latest subvariant was a factor in federal officials moving this week to make another booster dose available to older and immunocompromised people.

“I don’t think we’ll ever see anything like a quote-unquote ‘regular surge’ again. But we will see these little bumps. And I feel like XBB.1.16 may cause a little bump in our cases, a little bump in hospitalizations,” he said. “But we’re so low now that when you’re so low, you can only go one way, which is up.”

L.A. County’s COVID-19 vaccination clinics began offering the additional updated doses Thursday.


Angelenos who need help accessing the updated vaccine, anti-COVID therapeutic drugs or other COVID-19 resources can call (833) 540-0473, seven days a week, from 8 a.m. and 8:30 p.m.