What’s up with this new ‘Arcturus’ subvariant of SARS-CoV-2?

COVID Variants

Arcturus (XBB.1.16) is a subvariant of the omicron variant that the World Health Organization recently classified as a “variant of interest”.

TL; DR: The Arcturus subvariant has been growing in dominance since it was first identified in January 2023. It was classified as a “variant of interest” as it seems to have a growth advantage, but whether it might cause more severe disease is still unclear.

As of this past week, Arcturus has been found in 30 countries and accounts for > 7% of SARS-CoV-2 infections in the U.S. In late March, the World Health Organization had classified it as a variant under monitoring and then a few days ago it was upgraded further to a variant of interest (which is a step below variant of concern).

Variants of interest (VOI) are those that have genetic changes that give the virus a growth advantage AND are predicted to affect:

* transmissibility (i.e. how easily it is passed from person to person),

* immune evasion (i.e., the ability of the virus to avoid getting detected by antibodies that were

produced by our body after getting vaccinated or infected),

* virulence (i.e. the severity of disease it causes), and

* extent to which the virus can be treated with available medications and detected by tests.

A VOI switches to a variant of concern (VOC) if there is a medium to high level of confidence that it will:

* cause worse clinical severity OR

* impact the ability of health systems to provide care to those with COVID-19 or other illnesses requiring major public health interventions OR

* significantly decrease the effectiveness of currently available vaccines.

For now, it remains unclear whether Arcturus will go on to meet the criteria for being classified as a VOC. Important to keep in mind, is that even if it does, it is very unlikely that genetic mutations in the virus would be so substantial as to completely render prior immunity from infection and/or vaccination completely ineffective.

The good news also is given that Arcturus is a subvariant of the omicron variant and the updated COVID-19 booster shot targets the omicron variant, getting a booster shot (if you haven’t already) should provide you decent protection. Some groups of people are also now eligible for a second updated booster dose (see our recent post here for more info), which is good timing!

As with other variants that have come on the scene in the past, the same tried and true tactics (i.e., wearing high-quality masks, avoiding crowded places, increasing ventilation) still apply as added layers of protection beyond vaccination.

Overall, while Arcturus is on the radar for potentially being more transmissible (and could therefore cause a surge in cases), there is not currently any indication that it causes more severe disease. Those Nerdy Girls will keep tabs on this new subvariant and share out any updates as the situation evolves.

Stay safe, stay well!

Additional Resources:

For more information on ‘Arcturus’, click here

More Arcturus information

For more information about how the World Health Organization defines variants under monitoring, of interest, or of concern, click here

Link to original Those Nerdy Girls Facebook post