As stubborn as the idea is that the Sars-CoV-2 pandemic virus could have escaped from the central virological laboratory in the Chinese metropolis of Wuhan at the end of 2019 after experiments with manipulated bat viruses, the ground on which this “laboratory thesis” is based is still very thin .

For a good year and a half there has been no new, convincing evidence of this.

Almost everything remains speculation.

The official investigations of the World Health Organization (WHO) had come to nothing for the time being.

Nevertheless, the idea is repeatedly boiled up energetically.

The enormously important question of what triggered the pandemic, fueled not least by China's uncooperative behavior, has become a propaganda battle.

Conspiracy theorists and pseudovirologists ignite, science broods in the offside.

The Berlin coronavirus specialists led by Christian Drosten, who used molecular biology to get to the bottom of the Sars-CoV-1 virus that became epidemic almost twenty years ago, began to carefully dissect Sars-Cov-2 soon after the pandemic began.

One of the results, which has now been published in the journal "Communications Biology", which is part of the "Nature" group, is as important as it is unspectacular: it speaks strongly for a natural origin of Sars-CoV-2 - and thus supports the doubts on the laboratory construct.

Strictly speaking, it is about one of the most important scientific arguments of the laboratory theses speculators: the so-called furin cleavage site.

A crucial hinge in the spike molecule,

with which the virus attaches to the ACE2 surface molecule on the cell surface and thus gains access to the cell.

The two subunits of the spike protein are connected to each other at this molecular hinge.

And only if the protein is cleaved quickly after the virus has docked can the pathogen penetrate and multiply effectively.

The entry is therefore a complex process, because other molecules and enzymes are also required.

How can something like this occur in nature?

The question is so interesting because it became clear early on that Sars-CoV-2, the new coronavirus first found in Wuhan, has this furin cleavage site - but Sars-CoV-1 does not.

Furin cleavage sites have also been detected in other viruses, but the bat virus RaTG13, which is highly regarded as the closest relative of the pandemic virus, does not have this conspicuous sequence, which is encoded by the very special sequence of base molecules.

This exclusivity had stimulated the imagination of the virology critics: Was the furin cleavage site of Sars-CoV-2 possibly constructed and perhaps inserted into the virus for propagation experiments in Wuhan?

The answer from the Berlin virologists around Drosten, Anna-Lena Sander and Felix Drexler: extremely unlikely.

This is because the furin cleavage site is not as complicated and unusual as one would expect from a possibly artificially improved virus.

Rather, the furin cleavage site that appeared in Sars-CoV-2 seems to be a slightly modified spike molecule section "off the shelf".

The Charité virologists searched for similar furin cleavage sites in some virus archives.

They didn't even have to resort to Chinese stocks to do this.

In the faecal samples of four different European bat species from Italy, Spain, Bulgaria and Slovenia, individual viruses with fragmentary, quasi mutilated furin cleavage sites in the spike were found,

And not only that: The experiments in the laboratory showed that the key properties of the pandemic virus molecule can be produced very easily by what the publication calls a “conservative molecular mechanism within the bat reservoir”.

Such mechanisms are also known from influenza viruses: the exchange of a single molecule in the molecule segment can activate the furin cleavage site, so to speak.

This does not require any complex genetic engineering interventions, but individual small gene mutations are sufficient, or the recombination of gene sections of the virus genetic material that is possible during virus replication in the cell can be considered.

In other words: the central interface between virus and human being is possibly a cheap whim of nature,

This is not a refutation of the laboratory thesis, and it is not formulated that explicitly in any section of the virologist report from Berlin.

Nevertheless, it becomes very clear how much more likely the researchers consider a natural origin than a construction of the virus surface molecule.

Not least because of analogous molecular observations of influenza viruses, and because there are also many indications of this in the European corona viruses, the scientists write: “Our analysis shows possible ways for the furin cleavage site in Sars-CoV-2 to develop naturally, what for a natural evolutionary source in bats with or without the involvement of an intermediate host speaks"