When will evolution take place in humanity

The constant mutation of the Covid-19 pathogen : How humans can shape the evolution of Sars-CoV-2

Viruses mutate. All. All the time. It is the basic requirement for their evolution, their adaptation to the reproductive conditions that humans offer them. Researchers in the Sars-CoV-2 virus can follow this mutation, this process of gradual change, in real time and more precisely than ever before.

Has the virus changed since January? Are there more infectious variants, more aggressive, more dangerous for the patient? Or do the rules of distance and face mask laws ensure that only certain viruses can multiply? Do humans help shape the virus?

One mutation every 14 days

Just a few days after the discovery of the pathogen causing Covid-19 at the end of December 2019, Chinese researchers made the genetic sequence of Sars-CoV-2 publicly available. Since then, information about newly sequenced virus genomes from all over the world has been incorporated into the databases on a daily basis.

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Sometimes they resemble known Sars-CoV-2 variants, sometimes they differ, because the virus is constantly mutating - "on average, about one mutation every 14 days," says Richard Neher, head of the research group on the evolution of viruses and bacteria at the university Basel. He only means those mutations that are “left over”. Because every time the virus attacks a cell and is multiplied there, the copier makes mistakes - hundreds, thousands. Andreas Bergthaler from the Research Institute for Molecular Medicine of the Austrian Academy of Sciences in Vienna speaks of a whole "Cloud of Variants in a Person". Most of them lead to elementary defects - the end of the line.

Most of the few remaining mutations are "silent", so they do not improve or worsen anything. But a few may increase the infectivity of the virus, worsen the Covid 19 disease or change the survival time of the viruses, for example in aerosols.

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Knowing and mapping the mutations is one thing. This is made possible by Neher's “Nextstrain.org” project. The website collects and sorts the different Sars-CoV-2 variants "so that the diversity and evolution of the viruses can be tracked," says Neher.

The mutations only serve as a “signature”, as “identification” for the origin of the virus. For example, it can be seen that the current Sars-CoV-2 outbreak in Beijing is probably due to virus variants from Europe.

What causes a mutation can only be investigated in experiments

It is much more difficult to find out whether a certain mutation in one of the genes of the virus genome changes the properties of the pathogen. To do this, you have to test the mutated viruses experimentally. This is time-consuming, not least because such experiments can only take place in safety laboratories.

"Six months after the start of a pandemic, you cannot expect that we will already know about every mutation"says Neher. It is currently speculated that a mutation called “D614G”, which is also present in European virus variants, optimizes the stability of the “spike” protein of Sars-CoV-2, i.e. the “sting” that gives the pathogen access to the cell.

Experiments on cell cultures indicate this - it would be the first functional change in the virus. But there is no evidence that viruses are now spreading better or otherwise behaving differently because of this mutation, emphasizes Neher.

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Although this virus variant caught on relatively quickly in Europe, says Neher, it was probably due to a “founder effect”: Viruses with this mutation happened to be involved in one of the fast-growing outbreaks in February, which is why they are so common now.

"We cannot conclude from the dominance of this mutation that viruses with this mutation spread faster", says Neher, "because coincidences play a very, very important role, especially at the beginning of these exponentially growing outbreaks." So far, it has been assumed that "the mutations that we have observed so far do not make any significant difference to the transmission or virulence of the viruses “Says Neher.

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Michael Ryan, the head of the World Health Organization's emergency program, says there is “no information about a particularly pathogenic virus variant or virus mutations that could possibly render the vaccines or drugs now developed ineffective.

The behavior of the host helps determine which viruses can multiply in the future

It is clear that the framework conditions will determine which viruses will be selected from the “clouds” of variants in the future. If the virus is forced to multiply in a population that wears masks and keeps its distance, then it is possible that "only those viruses will be able to multiply that protect their host for longer and allow it to run around healthily for longer so that it can infect others", says Friedemann Weber, director of the Institute for Virology at the University of Giessen.

The virus "doesn't care at all" how sick it makes the infected person or whether he diesas long as this person passed the virus on beforehand.

But "if we use masks to extend the time until the next host can be infected, we align the selection to those virus variants that predominantly stay in the upper throat and tend to protect the host and make them less sick," says Weber. Because this way the virus has a higher chance of transmission. "So it may well be that we are driving the evolution of the virus in this direction through all the hygiene measures."

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