New Corona variant “under observation” – what we know about Acrux

The World Health Organization (WHO) has added the XBB.2.3 coronavirus variant to its watch list. The experts see “characteristics that indicate an increased capacity for infection”. In fact, Indian experts predicted as early as the end of April that XBB.2.3, called Acrux, may replace the currently most contagious corona variant Arcturus (XBB.1.16).

“A new contender for dethronement has arrived – Acrux (XBB.2.3), arguably the fastest of the currently circulating XBB clan,” wrote Indian expert Vipin Vashishta, a pediatrician and researcher at Mangla Hospital and Research Center in Bijnor, India, and a member of the WHO Vaccine Group, on Twitter. Acrux would come with a highly immune-evading mutation – S:T478K from the deadly Delta variant.

Why is XBB.2.3 called Acrux?

The currently circulating XBB lines are getting nicknames due to mutations and traits (immune escape, ACE2 binding, etc.), growth advantage, and remarkable distribution. The new nickname system uses astronomical names to convey information about ancestry. The explains T. Ryan GregoryCanadian evolutionary and genomic biologist and Professor in the Department of Integrative Biology and the Biodiversity Institute of Ontario at the University of Guelph.

The representatives of the “World Health Network” explain the background to the new system: “Astronomical names are numerous and can be assigned in such a way that they indicate variants that are not apparent with Greek letters or PANGO alias names.” In the specific case So from Acrux this means:

• Begins with AH = BA.2 ancestry
• The name contains an R in the name = a recombinant or a progeny of a recombinant.

Also good to know: “Acrux” is pronounced with an A as in “space” and a U as in “trucks”.

What mutations does Acrux bring with it?

Acrux, XBB.2.3, hat Vashishta according to four defining mutations:

• Spike mutations: S:D253G and S:P521S
• ORF mutations: ORF1a:G2091S and ORF7a:A13V
• Beyond XBB.2, Acrux has spike mutations P521S and S486P

Acrux also quickly develops many offspring. One of them, XBB.2.3.2, is considered to be the fastest. This one also has an interesting ORF1a mutation that has already appeared in several fast-growing lines.

Still other XBB variants are predominant

With Acrux, there are currently seven variants on the WHO’s watch list (variants under monitoring, VUM). Two others, XBB.1.5 and XBB.1.16, are at the next level and are therefore “variants of interest” (VOI). Currently, no variant is listed at the highest WHO level of “variants of concern” (VOC).

Arcturus (XBB.1.5) is still the most widespread. This variant accounts for 44 percent of global cases, followed by XBB.1.16 at 12 percent. For comparison: Acrux (XBB.2.3) is currently just under five percent, with a slight upward trend.

According to the Robert Koch Institute, Arcturus is still the most common in Germany with 20 percent, followed by XBB.1.9.1 with 17 percent. XBB.1.16, on the other hand, accounts for only about three percent, and Acrux (XBB.2.3) even less.

How dangerous are the XBBs?

Even if the corona virus mutates continuously, the danger does not change at the same time. So far, there is no evidence of a more sickening ability for any of the XBB variants compared to the previous lines. The RKI, citing the European health authority ECDC, also writes that the currently dominant subline XBB.1.5 for the general population a low risk represents. As in the previous weeks, for the listed sub-lines, with increasing distribution no increase in disease severity observed.

This is also the result of a new epidemiological study from Singapore, which was unable to find any significant differences in the number of cases and hospital stays between the various XBB lines.

“I don’t think that Arcturus will lead to many severe courses again,” said Ulf Dittmer, Director of the Institute for Virology at the University Hospital in Essen, when asked by FOCUS online. In particular, people who have been vaccinated first and are then mildly to moderately ill have a very broad immunity – through antibodies as well as through T-cells. That applies to a lot of people in Europe. “This protects them very well against serious illness and no conceivable variant can completely avoid it.”