The World Health Organization (WHO) has already announced a special audit, British tabloids recently speculated about the “return of the masks”, in parts of the USA one is moving towards the hospitalization and death rates of the BA.1 wave: it was only a matter of time , until Federal Health Minister Karl Lauterbach (SPD) would board the corona alarm train again.

The trigger for all this is the omicron subvariant XBB.1.5..

Joachim Müller-Jung

Editor in the feuilleton, responsible for the "Nature and Science" department.

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"Hopefully we can get through the winter before such a variant can spread to us," Lauterbach tweeted, presumably after a lengthy stay in the global Omicron news stream that has dominated social media for the past few days.

In fact, XBB.1.5 pulls.

meanwhile almost completely attracted the attention of the experts.

26 countries already affected

But is the pathogen really as dangerous as Lauterbach's reaction suggests?

The fact is: The variant is spreading practically explosively from the Northeast of the USA.

Apparently it is even more infectious than all previous omicron subvariants.

Not everywhere, however, where XBB.1.5.

was proven, one is as alarmed as in the USA.

And not everywhere - officially at least - the number of Covid 19 cases is increasing so rapidly.

The variant is widespread: the WHO now has reports of XBB.1.5. evidence from 26 countries.

The spread dynamics in the USA, where the vaccination gaps are significantly larger than in Europe, is not the only reason why the UN health authority also expressed "cause for concern" in one of its recent press conferences.

Rather, it is the virus itself that is leading some experts to speculate.

For the first time it is XBB.1.5.

a so-called recombinant, i.e. a genetic mixture of different variants, and not just a mutated descendant of a coronavirus line.

And this recombinant quickly asserts itself against other virus variants and displaces them in a very short time.

Recombinations occur, for example, when parts of the genome of different viruses mix during replication.

This often happens in the case of multiple infections at times when many different types of pathogens are on the move at the same time and in large numbers.

In the case of XBB.1.5.

the "parents" were the long previously circulating omicron variants BJ.1 and BM.1.1.1.

- two virus variants out of hundreds of others that the world had hardly noticed before, and which also had not triggered a wave of infections anywhere.

Increased immune escape and easier attachment

With XBB.1.5.

it's obviously different.

This variant is a new evolutionary stage of the original recombinant XBB that has been modified by additional mutations.

And XBB had already attracted attention months ago in epidemiological studies and laboratory experiments due to an increased immune escape.

Antibodies that were formed after vaccinations or infections with older Sars-CoV-2 variants were unable to neutralize XBB.

This trait of immune escape is nothing new, in fact it has been the secret of Omicron's success from the very beginning.

But XBB was even more successful with this optimization strategy.

But now, with XBB.1.5, two mutations were added that give the virus a striking transmission advantage.

The two mutations are located at a very specific point in the spike protein, which is crucial for the infection; a crucial amino acid has been exchanged.

This double mutation called F486P now ensures that the virus can dock more strongly to the corresponding binding sites in the human nasal and oral mucosa.

XBB.1.5.

is therefore doubly optimized: in terms of immune escape - which also makes vaccinated people susceptible to repeated infections - and in terms of the risk of infection.

According to the corona experts, however, this does not mean that this recombinant is more dangerous in the sense of more deadly.

In any case, the increase in hospital admissions, especially among older people, is due to the vaccination gaps and the extremely rapidly increasing number of infections and has not yet been explained by increased pathogenicity.

The South African omicron expert Tulio de Oliveira therefore does not consider it a given that XBB.1.5. will prevail in other countries or even worldwide and trigger huge new pandemic will.

It is possible that the population's immunity to omicron, which has already been built up in large parts, is sufficient to keep the health consequences within limits.

"It is also not the first time that omicron recombinants with the spike mutation F486P have appeared," warns the South African virologist.

Long before XBB, the recombinant XAY, which also had the mutation F486P, had been detected in South Africa - but it soon disappeared again.