Highly contagious corona variant: What is known about XBB.1.5

The new corona variant XBB.1.5 is currently spreading rapidly in the USA and has also been detected in 28 other countries. The omicron subtype also circulates here in Germany. Answers to the most important questions.

How fast does the omicron subtype spread?

According to the WHO, it is the most contagious subvariant of the coronavirus to date. In the USA in particular, the omicron subtype XBB.1.5 quickly displaced the previously dominant corona variants: Since November, the proportion of new infections with XBB.1.5 has doubled there every week, while the absolute number of infections is also rising again.” At the end of the year, XXB.1.5 has risen to become the dominant variant in the USA with 40.5 percent, estimates the US health authority CDC. According to media reports, the number of XBB.1.5 cases is also increasing in Great Britain.

The virus subtype has also been detected in Germany. Current figures from the Robert Koch Institute on the XBB.1.5 share in Germany are not yet available – the next weekly report with new data will be published on January 12th. The virologist Alexander Kekulé does not consider it unlikely that the virus could spread just as well in Europe as in the USA. In which countries the virus variant is currently spreading and how quickly is difficult to estimate, warns epidemiologist Maria Van Kerkhove, Covid-19 specialist at the WHO. Because globally there is less and less sequencing.

How dangerous is XXB.1.5?

The new subvariant is more contagious, but so far there is no evidence that it also leads to more severe disease progression, according to the WHO. The WHO is planning a precise risk assessment for the next few days. In Germany, the spread of XBB.1.5 is being monitored, explained Federal Health Minister Karl Lauterbach on Twitter.

It is still unclear how the new variant affects the infection process. “We’re seeing an overall increase in hospital admissions across the country,” Barbara Mahon, director of the CDC’s coronavirus and other respiratory viruses division, told NBC television. But in the north-east of the USA, where the XBB.1.5 variant is particularly widespread, there is no unusually high increase.

The possible spread of the new omicron variant is irrelevant for the fight against the corona virus in Europe, according to Kekulé, for the average person it simply means that one can become infected with corona several times a year.

How do mutations arise?

In order for viruses to be able to multiply, they have to copy their genome. There are always mistakes. Most mistakes go unnoticed, but a few can also give the pathogen new properties. If this new property means the virus is better able to replicate or evade the host’s immune system, then that’s a competitive advantage in a way. This appears to be the case with XXB.1.5.

How is XBB.1.5 different from the previous Omicron variants?

According to Chinese scientists, the XBB.1.5 mutation can now bind to cells much better. This could help spread it. The supervariant XBB arose from a recombination of two BA.2 sublines. From this developed XBB.1.5. Even the predecessor variant XBB was able to evade the human immune system surprisingly well as an immune escape variant. The XBB.1.5 that was created later is also even more contagious, as indicated by initial data from the Biomedical Pioneering Innovation Center (BIOPIC) in Beijing on a preprint server.

How does the WHO classify the variant?

The WHO closely follows virus variant development and regularly updates one List of all current corona variants. There is currently only one “variant of concern” (VOC) – i.e. a variant classified as causing concern, and that is the Omikron B.1.1.529 variant. The subvariant XBB.1.5 is currently not a “variant of concern”, but it is observed by the WHO – just like BA.5 and other omicron variants.

These meet three specific criteria: they are an omicron subvariant, they have a higher transmission rate, and they have additional amino acid changes. These changes are believed to be the reason for their greater spread among humans.

There is also the category “variants of interest” (VOI). These are variants that could be of interest for future infection events. They have genetic changes that are predicted or known to affect certain viral properties, such as transmissibility. And these variants have also been shown to be responsible for significant transmission in multiple countries. However, there is currently no “variant of interest”.