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New virus variants can arise, among other things, in people with a weakened immune system and then spread through the population (symbol image)
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JEROME FAVRE / EPA
The coronavirus has shown again how unpredictable it is.
Although experts had suspected that it will continue to mutate - this is part of the nature of the pathogen.
However, the number and composition of mutations that researchers have now discovered in the omicron variant is unusual.
"I'm surprised to see so many mutations in the virus," said Christian Drosten from the Berlin Charité on ZDF.
In the spike protein alone, which the coronavirus uses to gain access to human cells, Omikron has more than 30 mutations compared to the original virus.
The variant shares some of them with worrying mutants such as the alpha or delta variant.
Others are so new that their possible effects are completely unknown.
Due to the many mutations, Omikron is very different from the forms of the virus that have so far spread around the world.
"The virus does not appear to be a daughter of Delta or a grandson of Beta, but to represent a new line of Sars-CoV-2," writes a group of South African researchers who were involved in the discovery of Omikron in an article in "The Wire Science".
Not a daughter of Delta, not a grandson of Beta
Since the beginning of the pandemic, experts have been observing how the genetic makeup of the coronavirus is developing.
To do this, they collect information from samples around the world in which the complete genome of Sars-CoV-2 with all its mutations has been examined.
The result is family trees, with the help of which it is possible to understand how variants were created and spread across the world.
The genetic blueprint of the first omicron samples has now also been fed into the Nextstrain software.
The results suggest an unusual gap in the family tree.
The closest known evolutionary link from Omikron is to virus variants that were detected in mid-2020, writes Trevor Bedford, who studies the evolution of viruses at the University of Washington, on Twitter.
According to Bedford, two explanations for the more than a year long gap in the family tree are conceivable.
Accordingly, it could be that the virus has been circulating for some time in regions where the genetic make-up of the pathogen is rarely analyzed in corona cases.
The virus was first detected in South Africa.
But that does not mean that the variant actually developed in the country.
The second possible explanation, according to Bedford, is that the omicron developed in the body of someone with a compromised immune system and chronic infection.
Other researchers also think this is likely.
Accelerated evolution in the body
If the immune system is weakened by an HIV infection, for example, there is a risk that it can fight the coronavirus but not completely eliminate it.
The result is a chronic infection that lasts for weeks or even months.
Variants of the virus can accidentally develop that escape the immune system even better than the pathogen with which the person was originally infected.
Since the variants have an advantage compared to the original virus, they can prevail.
If those affected infect others, the modified virus can then spread to the population.
It's a kind of time-lapse evolution.
more on the subject
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New variant in South Africa: The concern about B.1.1.529 by Irene Berres and Nina Weber
In fact, HIV is now so treatable that the virus can no longer be detected in the body and hardly causes any damage.
In South Africa, however, there are many people with advanced HIV disease who do not have access to effective therapy.
That makes it more likely that such a case could have happened in the country.
In addition, South Africa experienced a devastating wave with the Delta variant.
Carsten Watzl, Secretary General of the German Society for Immunology (DGfI), believes that Omikron developed in a patient with HIV or another form of immunodeficiency as conceivable and likely. In people with a weakened immune system, the virus could multiply over many weeks, he told the dpa news agency. "In this process, isolated mutations can occur that may not bring the virus any benefit, but which can still multiply due to the lack of control by the immune system." This could result in additional mutations that could then be advantageous in combination.
According to the expert, in order to prevent such extensively changed variants from spreading, it would be important to identify and isolate immunocompromised people with a corona infection until they are no longer contagious.
"Because even if the virus mutates strongly in such a person, only passing on the mutated virus is really dangerous," he explains.
With material from dpa