Can there be evolution without mutations?

"The selection pressure on the virus is increasing"

Interview with Richard Neher from the University of Basel about the evolution of the coronavirus

Reports of new variants of the Sars-CoV-2 coronavirus have been increasing for weeks. Richard Neher researches the evolution of viruses and bacteria at the Biozentrum of the University of Basel. From 2011 to 2017 he was a research group leader at the Max Planck Institute for Developmental Biology in Tübingen.

Prof. Neher, coronaviruses have so far been considered a comparatively stable group. How is it that there are now more variants?

Sars-CoV-2 mutates less quickly than flu viruses or HIV, but the differences are not great. The resulting genetic lines enable us to reconstruct the path of spread of the virus. Until recently, however, there was little evidence that these mutations significantly alter the properties of the virus.

It has now been shown that some variants spread faster than others. Preliminary results from cell cultures also indicate that antibodies are less able to recognize some virus strains. However, we do not yet know whether this will actually affect immunity.

What is also new is that in some variants five, ten or more mutations appear at once. I would not have expected that.

How do you explain the rapid evolution?

It could be an indication of increasing and sustained selection pressure. A rising level of immunity in the population, for example, favors virus variants that can partially escape the body's defenses.

Under what conditions can such selection pressure arise?

It can occur at the level of an individual or population. In people with a weakened immune system, for example, who cannot fight the virus effectively, the pathogen has the opportunity to try new things over a longer period of time. In the end, the variants that escape the body's defenses most effectively remain.

Regions in which the first wave of the pandemic was particularly strong, such as parts of South America and South Africa, exert strong selection pressure, because many people there develop immunity after a Sars-CoV-2 infection. New virus variants may have an advantage here.

Excellent researchers are also working in South Africa and Brazil and are closely following the development of the virus. This is how these remarkable variants were discovered and investigated early on. There may be similar variants in other places that we don't know about yet.

Can there be herd immunity to Sars-CoV-2 under these circumstances?

Probably not globally, but locally with a high vaccination rate maybe for a certain time. The viruses change too quickly for herd immunity to develop in the population over the long term.

Is it conceivable that new variants of Covid-19 could cause death rates similar to Sars-CoV, which occurred in southern China at the end of 2002? After all, the Sars virus from back then is related to today's Sars-CoV-2.

There is no reason to expect anything like this. Sars-CoV and Sars-CoV-2 have been going their separate ways for a long time and therefore differ significantly from one another on a genetic level. These differences go well beyond the level of mutations we have seen so far. Therefore, in my opinion, it is very unlikely that Covid-19 could cause death rates similar to Sars-CoV 2002/2003.

In the future, will we have to be vaccinated against corona every year like against the flu?

At the moment it does not look as if the vaccination protection against Sars-CoV-2 wears off as quickly as with the flu. But I could imagine that the vaccination will have to be refreshed every few years with an adapted vaccine against the most common virus variants.

Interview: Harald Rösch