How coronavirus mutations are taking over

The more people the virus infects, the more chances it has to evolve, said Theodora Hatziioannou, a Rockefeller University virologist who studies the new variants.

Since the start of the pandemic, scientists using SARS-CoV-2 samples around the world have cataloged these genetic mutations. This has enabled them to build a family tree that charts how the virus evolves.

Here are some milestones in the evolution of the Covid-19-causing virus and how alterations to its genetic code have led to the new, potentially more contagious species making their way around the world:

Decisive mutation

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

The mutation, called D614G, changes the shape of spike proteins on the surface of the virus, making it more efficient at binding to and infecting cells.

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

“It replaced the ancestral virus by June,” said Jeremy Luban, a University of Massachusetts Medical School virologist who has studied the mutation. “Wherever it went, it became the dominant species.”

Spread in the summer

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

It has since spread widely across Europe.

20E (EU1) does not appear to have mutations that make it more transmissible than early variants. Rather, it may have been in the right place at the right time – a popular European holiday destination in the middle of summer. “It could be traveling in the summer, it could be because you’ve gotten rid of all your restrictions, or it could be because it’s more transferable,” said Emma Hodcroft, an epidemiologist at the University of Bern in Switzerland who researched the variant.

The new variants

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

Scientists believe that one mutation these variants share could help the virus attach to and enter cells. The recently discovered variant from Brazil shares an important peak protein mutation with that from South Africa.

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

Some scientists are concerned that the South African variant might be better at evading 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 recently said early data suggested it could be more deadly, too.

The variants found in the UK and South Africa have become the dominant types in countries where they were first discovered.

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

The UK variant had been found in more than 20 US states by the end of January.

The Centers for Disease Control and Prevention predicted it could become the dominant domestic species by mid to late March unless steps are taken to slow it down. The variants first found in South Africa and Brazil have also been found in the US

The full extent of their distribution is difficult to estimate. Aside from the UK and Denmark, few countries with active outbreaks have done extensive genetic sequencing of the virus, said Dr. Hodcroft.

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

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

Write to Daniela Hernandez at [email protected]