How coronavirus mutations take over

The more people become infected with the virus, the more likely it is to evolve, according to Theodora Hatziioannou, a virologist at Rockefeller University who studies new variants.

Since the beginning of the pandemic, scientists using SARS-CoV-2 samples collected around the world have been cataloging these genetic mutations. This has allowed them to build a family tree that draws the evolution of the virus.

Here are some milestones in the evolution of the virus that causes Covid-19 and how adjustments to its genetic code led to new potentially more infectious strains making their way into the world:

Decisive mutation

Earlier last year, scientists detected a mutation in Europe that makes the virus more transmissible than the original versions detected in China.

The mutation, called D614G, alters the shape of the tip proteins on the surface of the virus, making it more effective at binding and infecting cells.

Variants with the D614G mutation quickly outperformed previous versions of the virus.

“In June, it had replaced the ancestral virus,” said Jeremy Luban, a virologist at the University of Massachusetts School of Medicine who has studied the mutation. “Everywhere he went, he became the dominant strain.”

Summer broadcast

A new variant, known as 20E (EU1), was first detected in Spain last summer.

Since then it has spread widely throughout Europe.

20E (EU1) does not appear to have mutations that make it more transmissible than the early variants. Rather, it might have just been in the right place at the right time, a popular European summer vacation destination. “They could be summer trips, maybe it’s because you’ve removed all your restrictions or because it’s more transmissible,” said Emma Hodcroft, an epidemiologist at the University of Bern in Switzerland who led a study on the variant.

The new variants

Recently detected variants in the UK and South Africa have several new changes in their spike protein genes.

Scientists think a mutation shared by these variants could help the virus set in and enter cells. The newly detected variant of Brazil shares a key protein-tip mutation with that of South Africa.

“What we are seeing is exactly what we hope to see. The surface proteins of the virus are under enormous pressure to change them, ”said Sean Whelan, a virologist at the University of Washington in St. Louis. Louis. “Every virus that really cares multiplies … If it can get into the cells of the [host] and avoid this host’s immune system, it will multiply. Whether it causes disease is a different matter. ”

Some scientists worry that the South African variant may be better at eluting antibodies produced in response to natural infection and vaccination.

Preliminary estimates suggest that the UK variant is 50% -70% more transmissible than previous versions of the virus. And British scientists said recently that early data suggest it could also be more deadly.

Variants found in the UK and South Africa have become the dominant types in the countries where they were first detected.

The UK variant has spread widely abroad. By the end of January, it had been reported in 70 countries and territories. The variant from South Africa has been reported in more than 30.

The UK variant had been detected in more than two dozen US states by the end of January.

The Centers for Disease Control and Prevention projected that it could become the dominant domestic strain in mid or late March, unless steps are taken to curb it. Variants first found in South Africa and Brazil have also been detected in the US

It is difficult to measure its extent. Apart from the UK and Denmark, few countries with active outbreaks have carried out extensive genetic sequencing of the virus, Dr Hodcroft said.

“At the moment, almost the rest of the world is a blind spot.”

Additional sources: Nextstrain (phylogenetic trees); Emma Hodcroft, University of Bern

Write to Daniela Hernandez at [email protected]