May 19, 2024

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Arcturus: COVID-19 Omicron Variant XBB.1.16 spreading in 34 countries

Arcturus: COVID-19 Omicron Variant XBB.1.16 spreading in 34 countries


Arcturus: COVID-19 Omicron Variant XBB.1.16 spreading in 34 countries.

The Arcturus variant of COVID-19, a subvariant of Omicron, has been detected in 34 countries, with India the most affected.

The variant’s high transmissibility may be due to its ability to evade immunity from vaccination and previous infection.

While there is no data on the efficacy of vaccines against Arcturus, it is currently thought to be no more severe than previous variants, and scientists are developing vaccines to deal with this emerging strain.


Arcturus: COVID-19 Omicron Variant XBB.1.16 spreading in 34 countries



A new COVID variant, XBB.1.16, or “Arcturus,” has now been identified in at least 34 countries, including the UK. Arcturus is a subvariant of omicron that was first discovered in India in January 2023.

As of 17 April, the latest date the UK Health Security Agency (UKHSA) reported data for this variant in the UK, 105 cases of Arcturus had been sequenced across England. Five Britons who tested positive for Arcturus have died.

It’s worth noting that only a small percentage of people with COVID-19 have had their genes sequenced, so it’s likely there are many more cases of Arcturus. The UK Health Service recently reported that the variant accounts for 2.3% of sequences in the UK.

Meanwhile, Arcturus has been steadily rising in the U.S. in recent weeks, accounting for more than 10% of new COVID-confirmed cases as of the end of April.

But the variant has been dominant in India, which accounted for 61% of the world’s recorded Arcturus sequences as of mid-April. It has contributed to a huge increase in cases in India over the past month. The country records more than 10,000 COVID cases a day, with Arcturus accounting for two-thirds of all cases. Fortunately, that tide now appears to be descending.

Nonetheless, Arcturus has been listed by the World Health Organization as a variant of concern. So, what do we know about this variant, and should we be worried?



Where did Arcturus come from?

XBB.1.16, a descendant of XBB, is a recombinant Omicron strain, meaning it contains genetic material from two different varieties. Specifically, XBB is a mixture of two BA.2 sublines: BA.2.10.1 and BA.2.75.

Relative to earlier variants, XBB has shown higher transmissibility, possibly because it appears to be better at evading immunity from existing vaccinations and previous infections. Arcturus is very closely related to XBB.1.5, also known as Kraken. Compared to its parent strain XBB, Arcturus has three additional mutations in the spike protein: E180V, F486P and K478R. This is a protein on the surface of SARS-CoV-2 (the virus that causes COVID) that allows it to bind to and infect our cells.

Arcturus is known to be the most contagious subvariant to date, and these additional mutations may explain why.

Typical symptoms of COVID include fever, cough, runny nose and loss of taste or smell. However, doctors in India reported that children infected with Arcturus developed symptoms of conjunctivitis, which is not normally present during early COVID transmission.

What about vaccine protection?

The COVID vaccine targets the spike protein of SARS-CoV-2. Therefore, mutations in the spike protein may affect the effectiveness of the vaccine. There are currently no data on the efficacy of the vaccine against Arcturus. However, a recent study found that antibody responses to closely related XBB and XBB.1 strains were significantly lower than responses to other variants in vaccinated or previously infected people. Therefore, XBB subvariants may threaten current COVID vaccines and treatments. But importantly, the vaccine is likely to still provide good protection against severe disease.

While further research is needed to confirm Arcturus’ response to the vaccine, scientists are continuing to work on new vaccines that may offer greater protection against emerging variants.



The continued evolution of the omicron

Although the omicron was first detected in late 2021, it continues to evolve, leading to new subvariants. Arcturus is one of about 600 detected so far.

This is to be expected in a highly vaccinated population. New variants naturally evolve to evade existing defenses. Those strains that have a competitive advantage—that is, greater transmissibility and the ability to evade our immune response—will dominate. Arcturus could contribute to an increase in cases in the UK and elsewhere.

However, there’s no great reason to worry. While scientists will continue to monitor Arcturus, there is no evidence at this stage that it is more severe than previous variants. Also, we now have good protection from vaccines and natural infection.

Still, the ongoing evolution of COVID and the emergence of new strains like Arcturus remind us that this virus is still with us. For those who qualify for further intensive treatment, it is important to stay up to date on treatment strategies.


By Manal Mohammed, Senior Lecturer in Medical Microbiology, University of Westminster.




Arcturus: COVID-19 Omicron Variant XBB.1.16 spreading in 34 countries

(source:internet, reference only)

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Important Note: The information provided is for informational purposes only and should not be considered as medical advice.