How it takes over coronavirus mutations

The more people the virus infects, the more likely it is to evolve, according to Theodora Hatziioannou, a virologist at Rockefeller University who is studying the new variants.

Since the beginning of the pandemic, scientists using SARS-CoV-2 samples collected around the world have cataloged these genetic mutations. This allowed them to build a family tree that showed how the virus evolved.

Here are some milestones in the evolution of the virus that causes Covid-19 and how changes in its genetic code have led to new potentially more infectious strains making their way around 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, changes the shape of spike proteins on the surface of the virus, making it more efficient at binding and infecting cells.

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

“By June, it had replaced the ancestral virus,” said Jeremy Luban, a doctor at the University of Massachusetts who studied the mutation. “Wherever it went, it became the dominant strain.”

Summer spreadtime

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 early variants. Rather, it may have been at the right place at the right time – a popular European holiday destination at the height of summer. “It could be summer travel, it could be because you got rid of all restrictions or it could be because it’s more transmissible,” said Emma Hodcroft, an epidemiologist at the University of Bern in Switzerland who conducted a study on .

The new variants

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

Scientists believe that a mutation in these variants could help the virus attach and enter cells. The recently detected variant in Brazil shares a key spike-protein mutation with that in South Africa.

“What we see is exactly what we expect to see. The virus’s surface proteins are under tremendous pressure to change, “said Sean Whelan, a virologist at the University of Washington in St. Louis. Louis. “Everything he cares about the virus is multiplying … If it can get into the cells [host] and avoid that host’s immune system, it will multiply. Whether it causes disease is a different question. ”

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

Preliminary estimates suggest that the UK version is 50% -70% more transmissible than previous versions of the virus. Scientists in the UK have also recently said that early data suggest it could be even 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 South African variant has been reported in over 30.

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

The Centers for Disease Control and Prevention has projected that it could become the dominant domestic strain by mid to late March, unless steps are taken to slow it down. Variants first found in South Africa and Brazil were also detected in the USA

The full extent of their spread is difficult to measure. Apart from the United Kingdom and Denmark, few countries with active outbreaks have done extensive genetic sequencing of the virus, said Dr. Hodcroft.

“Right now, almost the rest of the world is deadlocked.”

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

Write to Daniela Hernandez at [email protected]