Arcturus now on CDC watchlist

A new coronavirus subvariant, “Arcturus,” has been making headlines in the US with the increased number of cases and no less than the US Centers for Disease Control and Prevention (CDC) has put it on its watch list.

Officially labeled XBB.1.16, Arcturus is the latest Omicron offshoot. It was first seen in India and has been on the WHO watchlist since the end of March.

Arcturus is now responsible for over 7 percent of COVID-19 cases in the US, next to the predominant Omicron variant XBB.1.5, which causes 78 percent of cases, according to the CDC.

What is novel about this subvariant is that it brings with it an all-new COVID-19 symptom – conjunctivitis or pink eye in children – which is rarely reported with the previous strains.

Too early to be certain

In February, the Arcturus strain accounted for 0.21 percent of cases around the world. A month later, this had risen to 3.96 percent, according to WHO figures.

 In the week ending April 15, Arcturus-related cases accounted for 7.2 percent of coronavirus infections in the US as reported by the CDC.

The WHO designated Arcturus a “variant under monitoring” on March 22. This means the variant has “genetic changes” that could affect its characteristics as a virus. A “variant under monitoring” is of lesser concern than a “variant of interest,” which is known to be more transmissible or virulent, or able to evade antibodies, according to the WHO.  

Nevertheless, a “variant under monitoring” could always eventually become a “variant of interest” or even a “variant of concern.”

 Arcturus or XBB.1.16 is similar to the prevalent XBB.1.5 variant but has one additional mutational mutation in the spike protein, which in laboratory studies has shown increased infectivity and potential increased pathogenicity, added the WHO.

“Arcturus is more transmissible but is in no way more dangerous than the other strains,” said Professor Paul Hunter from the University of East Anglia in Norwich, UK. There is no indication yet that Arcturus will cause more severe cases.

 “There’s no evidence this subvariant is any more severe — and probably it’s somewhat less severe than the previous strains — but it’s too early to be certain. And that’s almost certainly because of immunity,” he said.

 Tracking Arcturus

 The spread of the XBB.1.16 reportedly fueled a surge in COVID-19 cases in India recently and sparked the reintroduction of face mask mandates and mock drills in hospitals. 

 As of this writing, XBB.1.16 has also been detected in sequenced samples from countries including Britain, Canada, and Australia, according to the CoV-Spectrum website, which uses data from the GISAID Initiative to track coronavirus variants. [https://cov-spectrum.org/explore/United%20States/AllSamples/Past1M/variants?nextcladePangoLineage=xbb.1.16*&]

 The CDC variant tracker showed that XBB.1.16 is circulating at low levels in over a dozen states, including California, Colorado, Delaware, Florida, Indiana, Illinois, Iowa, Maryland, Missouri, New York, North Carolina, and Ohio in the US. [https://covid.cdc.gov/covid-data-tracker/#variant-proportions-state-jurisdiction]

“It does seem to be spreading more rapidly than any other variant right now, but this is always what happens: A new variant comes along, it spreads quite rapidly for a while, and then it peters out over a period of a few weeks, ultimately to be replaced by the next one,” Hunter said.

He shared that previous studies have shown that many people are benefiting from the hybrid immunity that comes from a combination of previous infections and vaccination, which should offer them better protection against severe disease “for quite a bit longer.”

Data also continue to mount on the retooled COVID-19 bivalent boosters’ ability to save lives and reduce hospitalization risk. [N Engl J Med 2023;388:764-766]

Since September 1, 2022, the Moderna and Pfizer–BioNTech bivalent COVID-19 vaccines, each containing equal amounts of mRNA encoding the spike protein from the ancestral strain and the spike protein from the BA.4 and BA.5 strains of the B.1.1.529 (Omicron) variant, have replaced their monovalent counterparts. This was following US FDA approval for its emergency use as booster doses in those >12 years and older, both in the US and in other markets. 

COVID-19 continues to evolve

Nevertheless, Los Angeles County Public Health Director Barbara Ferrer said people should not lower their guard against COVID-19. “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.”

“But the fact that we’re seeing new strains – just like Arcturus – with possible different symptoms should remind us that COVID continues to evolve,” she cautioned.