Are the mutations making COVID-19 more infectious?

Gente con mascarilla paseando en Barcelona.

Although thousands of changes have been detected in the virus, until now scientists have only registered one that possibly alters its behavior

The coronavirus that is threatening the world right now is not the same as the coronavirus that first emerged in China.

SARS-CoV-2, the official name of the virus that causes the disease COVID-19, is mutating.

But while scientists have detected thousands of mutations, or changes in the virus’ genetic material, so far it has only been reported orna than could alter your behavior.

The crucial questions about this mutation are: does this make the virus more infectious, or lethal, in humans? And could it pose a threat to the success of a future vaccine?

This coronavirus is actually changing very slowly compared to a virus like the flu.

With relatively low levels of natural immunity in the population, no vaccine, and few effective treatments, it has no pressure to adapt.

The designated mutation, call D614G and located within the spike protein – the spike-shaped protein that the virus uses to penetrate our cells – appeared sometime after the initial outbreak in Wuhan, probably in Italy. It is now seen in up to 97% of samples worldwide.

Evolutionary advantage

The question is whether this domain means that the mutation gives the virus any advantage, or is it just by chance.

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The D614G mutation is located inside the spike protein, which the virus uses to penetrate our cells

Viruses don’t have a big plan. They constantly mutate And while some changes help a virus to reproduce, some can make it harder. Others are simply neutral.

They are a “by-product of the replicating virus,” says Dr. Lucy van Dorp of University College London. They “hitchhike” over the virus without changing their behavior.

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The mutation that has emerged could have become widespread only because it took place early in the outbreak and spread, something known as the “Founder effect”. This is what Dr. Van Dorp and her team probably explains why the D614G mutation is so common. But this is increasingly controversial.

An increasing number – perhaps most – of virologists now believe, as Dr. Thushan de Silva of the University of Sheffield explains, that there is enough data to say that this version of the virus has a “Selective advantage” -an evolutionary advantage- over the previous version.

Although still there is not enough evidence to say than “It is more transmissible” in people, says De Silva, he is sure that “it is not neutral.”

When studied under laboratory conditions, the mutated virus entered human cells more effectively than those without the variation, say Professors Hyeryun Choe and Michael Farzan, at Scripps University in Florida.

Changes in the spike proteins the virus uses to attach to human cells appear to allow it “Stick better and function more efficiently”.

But that’s where they put the limit.

Professor Farzan said that the spike proteins of these viruses were different in a way that was “consistent with, but did not demonstrate, increased transmissibility.”

Lab tests

At the Genome Technology Center at New York University, Dr. Neville Sanjana, who normally spends his time working on CRISPR gene editing technology, has gone one step further.

His team edited a virus to have this alteration in the spike protein and pitted it against a real SARS-CoV-2 virus from the initial Wuhan outbreak, without the mutation, in the cells of human tissues. He believes the results show that the mutated virus is more transmissible than the original version, at least in the laboratory.

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Van Dorp notes that “it is unclear” how representative these transmission results are in real patients. But Professor Farzan says these “marked biological differences” were “substantial enough to tip the evidence a little” in favor of the idea that the mutation is making the virus spread better.

Outside of a Petri dish, there is some indirect evidence that this mutation makes the coronavirus more transmissible in humans. Two studies have suggested that patients with this mutated virus have higher amounts of the virus in your samples swabs.

However, they found no evidence that those people got sick or stayed in the hospital any longer.

coronavirus particles in pink

Two studies have suggested that patients with the mutated version of the coronavirus have higher amounts of the virus in their swab samples.

In general, make it more transmissible doesn’t mean a virus is more deadly; in fact, the opposite is usually true. There is no evidence that this coronavirus has mutated to make patients more or less ill.

But even when it comes to transmissibility, viral load is just an indication of how well the virus is spreading within a single person. It does not necessarily explain how effective it is at infecting others.

The “gold standard” of research, a controlled trial, has not yet been carried out. That could involve, for example, infecting animals with one or another variant of the virus to see which one spreads the most in a population.

Professor Bette Korber of the Los Alamos National Laboratory in the USA and principal investigator of one of the studies said there was no consensus, but the idea that the mutation increases the viral load of patients is “less and less controversial as more data accumulates. “

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Mutation is pandemic

When it comes to looking at the population as a whole, it’s hard to see the virus become more (or less) infectious. Its course has been drastically altered by interventions, including quarantine measures.

But Professor Korber says that the fact that the variant now seems to be dominant everywhere, even in China, indicates that it may be more effective in transmission between people than the original version. Every time the two versions were in circulation at the same time, the new variant is imposed.

People with facemasks strolling in Barcelona.

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One of the measures taken to prevent the spread of the virus is the use of masks.

In fact, the D614G variant is so dominant which is now the pandemic. And it has been for some time, perhaps even since the beginning of the epidemic in places like the United Kingdom and the US east coast.

So even though the evidence is mounting that this mutation is not neutralIt does not necessarily change the way we should think about the virus and its spread.

On a more reassuring point, most developing vaccines are based on a different region of the spike, so this should not have an impact on their development.

And there is some evidence that the new way is just as sensitive to antibodies, which can protect you against infection once you have had it or have been vaccinated.

But since the science of covid-19 is moving so fast, this is something that all scientists, wherever they are about the meaning of current mutations, will be watching.

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