Arcturus Covid Strain Could be Most Infectious

A sub-variant of the Covid-19 virus known as Arcturus, or Omicron Variant XBB.1.16, is behind a surge of infections in India, and could be the most infectious variant yet.

Research indicates that Arcturus could be one 1.2 times more infectious than the last major sub-variant. it was first identified in January and has been monitored by the WHO (World Health Organisation) since 22nd March. It was upgraded it to a “variant of interest” in mid-April.

Addressing the emergence of Arcturus at a press conference on 29th March, Dr Maria Van Kerkhove, the WHO’s technical lead for Covid, said: “It’s been in circulation for a few months.

“We haven’t seen a change in severity in individuals or in populations, but that’s why we have these systems in place. It has one additional mutation in the spike protein, which, in lab studies, shows increased infectivity as well as potential increased pathogenicity.”

According to Matthew Binnicker, director of clinical virology at the Mayo Clinic in Rochester, USA, Arcturus, named after the brightest star in the Northern sky, may also be associated with a higher-grade fever than other variants.

Although the sub-variant, one of 600 spawned from Omicron so far, is seemingly no more dangerous than the others, it has already been responsible for five deaths in the UK. It is know to have spread to 34 countries so far, including Britain and the USA.


India, health resources reported 63,380 active Covid cases on 25th April. Figures have been rising for six weeks, prompting introduction of compulsory face masks in some states, and hospitals to carry out mock drills. Vaccine production has also been increased. According to WHO estimates, the Delta wave in 2021 contributed to 4.7m excess deaths in India in 2021.

Dr Vipin Vashishtha, a paediatrician and former head of the Indian Academy of Pediatrics Committee on Immunisation, sad in The Hindustan Times that Arcturus’s symptoms include a high fever, a cough and “itchy” conjunctivitis or ‘pinkeye’.

In the UK, the Health Security Agency has detected 135 cases of Arcturus and five deaths. Professor Paul Hunter of the University of East Anglia told The Daily Mail it is too soon to say that Britain could face a fresh surge in infections driven by Arcturus. “Although in India it has taken off in the past few weeks so far it has not been increasing rapidly globally,” Professor Hunter said.

“I suspect we will see a wave of infections with this variant but I doubt it will cause a big wave probably not even as great as the one we have just had in the UK and so probably not put as great a pressure on health services than recently.”


Scientists at the University of Tokyo comparing the Kraken strain of Covid, also known as XBB.1.5, which was the dominant form of the disease in Britain until February, to the Arcturus sub-variants have suggested that the newer strain spreads about 1.17 to 1.27 times more efficiently than its relative, warning that it “will spread worldwide in the near future” aided by the fact that it seems “robustly resistant” to antibodies lingering in the body from previous Covid infections.

In the USA, Arcturus is now responsible for 9.6 per cent of Covid cases, according to the Centers for Disease Control and Prevention and the WHO. Virologist Professor Lawrence Young from the University of Warwick told The Independent that the rise of the new variant in India is a sign that “we’re not yet out of the woods”, adding: “We have to keep an eye on it. When a new variant arises you have to find out if it’s more infectious, more disease-causing, is it more pathogenic? And what’s going to happen in terms of immune protection.

“These kinds of things highlight the importance of genomic surveillance but a lot of countries including our own have let our guards down a bit and we can’t be sure what variants are around and what level of infection they’re causing until we see a significant outbreak.”

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