No variant has ever been so contagious: The new Omicron subline XBB.1.5 is currently spreading in the USA, and there is already evidence in Germany. Scientists gave it the nickname “octopus”. What you need to know about the Corona sea monster.

Since mid-December it has dominated the infection process in the USA, and it has already arrived in Germany: the new omicron variant XBB.1.5, also known as “octopus”, is considered to be highly contagious. According to initial data, changes to the spike protein make it easier for it to enter human cells. FOCUS online clarifies the most important questions about infectiousness, disease progression and development.

According to experts, the subline XBB.1.5 of the Corona variant Omikron could also spread widely in Europe and Germany in the coming weeks and months. “One can say with some prognostic certainty that the variant will also become the dominant variant for us,” said Bremen epidemiologist Hajo Zeeb. But there is no cause for great concern. “We’re seeing a little more cases in the US, but there’s not a huge wave going on there.”

XBB.1.5 has rapidly increased in frequency in the northeastern United States and has dominated the infection process there since mid-December, said Richard Neher, head of the research group Evolution of Viruses and Bacteria at the Biozentrum of the University of Basel. Outside of the northeastern United States, the variant is even less common, but the proportion is increasing.

“The basic variant has been known since October,” said Zeeb, who heads the Leibniz Institute for Prevention Research. “It was seen for the first time that the combination of subvariants had occurred.” The special feature of XBB.1.5 is the even higher infectivity. “It had already been developed at Omikron, and now XBB.1.5 tops it again.”

Corona specialist Maria van Kerkhove from the World Health Organization (WHO) said on Wednesday in Geneva that the subline was more easily transferrable than any of the previously known variants. The EU health authority ECDC announced on Thursday that XBB.1.5 is believed to have a “major growth advantage” over the previously circulating lines in North America and Europe. However, this assumption is still associated with considerable uncertainties.

What is special about XBB.1.5 is a “critical double mutation”, as physician Eric Topol writes on Twitter. This is responsible for the immune escape and the high level of infectivity. This is now indicated by a new study by Chinese scientists published in the preprint. The variant is therefore changed in comparison to XBB.1 at two points of the spike protein. This would allow XBB.1.5 to bind better to human ACE2 receptors, facilitating entry into cells.

“This means that the new variant XBB.1.5 is also more contagious in addition to the immune escape because it requires a lower infection dose, i.e. fewer viruses, to trigger an infection,” emphasized virologist Alexander Kekulé in an interview with FOCUS online.

And virologist Hendrik Streeck said “RTL”: “The XBB.1.5 variant shows greater transmissibility, even in vaccinated or just recovered.”

Federal Health Minister Karl Lauterbach (SPD) has already expressed concern. On Thursday he tweeted: “Hopefully we can get through the winter before such a variant can spread to us.”

According to Neher, there is little information about the severity of diseases with the new subline. Cases and hospitalizations have increased across the US, not just in regions where XBB.1.5 is prevalent, the expert said. This is at least a first indication that the severity of XBB.1.5 infections does not differ significantly from that of other variants currently circulating. Virologist Kekulé also confirmed that there is no data to date that indicates more severe courses.

And what does the subline mean for Germany? “XBB.1.5 is encountering a receding immunity from people who were vaccinated or infected a long time ago,” explained Zeeb. “First in the USA and then also here in Germany.” However, the number of XBB.1.5 records in Germany is currently still very low. “You don’t have to think about new measures yet.”

According to the Robert Koch Institute, the subline was detected for the first time in a random sample in Germany at the end of November. According to ECDC, it could have an increasing impact on the number of corona cases in Europe, but not within the next month. The frequency of XBB.1.5 has been doubling about every week, Neher said. If this trend continues, a share of three to six percent can be expected in the first half of January.

It is important to keep a close eye on developments, said Zeeb. The ongoing sequencing of samples is very important and must be maintained at a high level. To do this, you have to work together across Europe. “A good proportion of cases from all countries should be sequenced. This is important in order to identify really relevant changes as early as possible.”

The Canadian biologist Ryan Gregory first called the variant “octopus”. “XBB.1.5 definitely deserves a nickname with its record-breaking growth advantage and both very high immunity and ACE2 binding,” he wrote on Twitter just after Christmas. Since then, many scientists have been using the hashtag “kraken” on social media, and the international press has meanwhile picked up the name.

The WHO no longer gives the subvariants Greek letters because they differ less from each other than, say, alpha from beta. That is why scientists use such so-called “street names” so that the population can better remember the names of the variants. For example, the omicron variant BQ.1.1 was called “Cerberus”, like the hellhound that guards the entrance to the underworld in Greek mythology.

The octopus is also said to symbolize a dangerous animal, a sea monster. Even if, as biologist Gregory admits, this does not come from Greek mythology.