“Child of Arcturus” – New XBB.1.16 mutations are causing experts concern

Regarded as the most contagious of all Omicron variants known to date: XBB.1.16 – and now this subline is upping the ante. The omicron recombinant behind the surge in Indian Covid cases has already mutated. This could help it gain another growth advantage, said top experts monitoring mutations in the Sars-CoV-2 virus, which ”
Times of India
“.

Indian and international genome sequencing experts are now calling the new variant XBB.1.16.1, describing it as “a new child of XBB.1.16”. For example, it has an additional T547I mutation.

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Which makes new mutations of Arcturus worrying

The Indian expert Vipin Vashishta, pediatrician and researcher at
Mangla Hospital and Research Center
in Bijnor, India, and a member of the WHO vaccine group, wrote on Twitter: Arcturus has additional mutations “to achieve a further growth advantage”. And further: “There were two additional mutations on Spike, including S494P, which are expected to better evade the immune system without affecting ACE2 binding affinity.”

In other words, the mutated variant will be even better at infecting those who are vaccinated or have already gone through Corona. But how strong the effect will be remains to be seen. So far there is no big wave in India. Nevertheless, experts closely monitor XBB.1.16 and its developments.

Arcturus and XBB.1.16.1: What you should know about the new Corona variant

Arcturus has been spreading in India since February. The new Corona variant XBB.1.16 has been increasing the number of cases there for a few weeks – albeit at a low absolute level. Still, it was enough to trigger a certain level of alertness.

The World Health Organization (WHO) put the variant on the list of variants to be observed (variants under monitoring, VUM) on March 22. Loud
current WHO report
it has already been demonstrated in 21 countries.

“The number ‘1’ was added after the period to indicate that this is the first mutation identified within the XBB.1.16 group,” said Rajesh Karyakarte, Genome Sequencing Coordinator and Principal Investigator at BJ Medical College ( BJMC), the Times of India. If other mutations are identified within this group, they can be named XBB.1.16.2, XBB.1.16.3, and so on.

Where did Arcturus originate?

The coronavirus is constantly mutating and evolving. That is his nature. XBB.1.16 now appears to be able to evade human-developed hybrid immunity—that arises when someone was both vaccinated and infected. In Pune, the first case of XBB.1.16 was detected on February 3, 2023 as “
Hindustan Times
‘ reported before it was officially labeled as such around the world on March 5. In Mumbai, the variant first appeared on March 11.

What is the structure of Corona variant XBB.1.16?

According to the Robert Koch Institute (RKI), the subline is characterized by three additional mutations in the so-called spike protein (E180V, K478R, S486P). That is not all. “XBB.1.16 has a number of other changes in the genome that not only affect the spike protein, but also the so-called ORF9b gene, which is involved in suppressing the interferon response,” explained Friedemann Weber, head of the institute for virology at the University of Giessen, the biological details for FOCUS online.

Interferons are messenger substances that are produced by infected cells to warn other cells of the infection and to initiate countermeasures. However, Sars-CoV-2 has a whole range of these so-called interferon antagonists, and ORF9b has not yet been one of the strongest representatives.

Therefore, Weber’s conclusion was: “I do not expect that the two XBB.1.16-specific mutations in ORF9b would radically change this. This, together with the new spike mutations, shows that XBB.1.16 certainly has potential to outperform existing immunity by a bit.”

How dangerous is Arcturus really?

Experts warn against panic, there is still hardly any reliable data. How well our immune system can fight off Arcturus will help determine how dangerous the variant becomes. XBB.1.16 can “skilfully bypass immunity,” explained Rajesh Karyakarte. The head of microbiology at the BJMC sequenced the first Arcturus representatives and informed the Ministry of Health on March 10th. According to one of his team members, this also applies to the robust immunity after vaccination and infection. At the same time, the variant is spreading even faster than its predecessors – and has now displaced them in the first regions.

However, the number of hospital admissions has not yet skyrocketed as a result. “Most patients had mild symptoms,” reported Karyakarte.
The Times of India
“.

What are the symptoms of XBB.1.16?

Rajas Walinjkar, doctor at Seven Hills Hospital, which treats many inpatients,
describes the symptoms as follows
:

• fever lasting less than 48 hours
• sore throat
• body aches

This is therefore a profile similar to that seen with the previous Omikron variants.

How sick does Arcturus make?

Little is known about XBB.1.16’s disease-causing ability. There have already been deaths associated with Arcturus in India. Otherwise, as mentioned, the courses are predominantly mild.

The Robert Koch Institute (RKI) writes about the XBB.1.5 subline currently predominant in Germany: Preliminary data do not indicate an increased severity of the disease.

Experts do not expect this for Arcturus either. “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. Especially people who have been vaccinated first and are then mildly/moderately ill have a very broad immunity – through antibodies as well as through T-cells. That applies to many in Europe. “This protects them very well against serious illness and no conceivable variant can completely avoid it.”

The number of Arcturus cases in Germany

Arcturus is a subline of the now dominant omicron recombinants XBB.1 in Germany. The total share, including all sub-lines of the variant, has increased compared to the previous weeks, according to the
latest weekly report
. It was 67 percent in the week of March 13. For Germany, the RKI expects a further increase in the proportion of XBB.1 sublines in the coming weeks.

So far, Arcturus has spoken of seven cases in Germany. However, experts do not know the numbers exactly. Because XBB.1.16 is not shown separately in the weekly report of the RKI.

The low number can also be related to the fact that not all infected people have a PCR test done, which is necessary for sequencing the variant.

Wastewater monitoring is therefore of greater importance. This paints a much more realistic picture of the corona situation in Germany. Some sites are reporting increasing viral loads in wastewater. The
pandemieradar
shows for the week before Easter (status: 06.04.23): Der
The proportion of sites with increasing viral loads in wastewater was 14 percent, 186 percent higher than in the previous week
(five percent). For 21 percent, the viral load remained the same, for 64 percent there was a downward trend.