The coronavirus appears to have mutated. What does that mean for contagiousness?

While small mutations in the virus's genetic code are evident, it's unclear what these changes mean for people, if anything at all.
A transmission electron microscopic image of the virus that causes COVID-19.
A transmission electron microscopic image of the virus that causes COVID-19.National Institutes of Health / AFP - Getty Images

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/ Source: NBC News
By Erika Edwards

A new study has sparked fears that the coronavirus has mutated to become more contagious, but experts say there is no evidence these changes make it any more dangerous or transmissible than it already is.

"Viruses mutate all the time, [and] most mutations have no significance even if they spread," said Adriana Heguy, director of the Genome Technology Center at New York University, who was not involved with the research.

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The study was posted on the preprint server bioRxiv on April 30. Preprints are studies that have not undergone the rigorous peer-review process required for publication in medical or scientific journals. In the rush to share new research on COVID-19, many scientists have been sharing their work online before undergoing the full review process.

The authors, who included researchers from the Los Alamos National Laboratory in New Mexico, analyzed the genetic sequences of samples of the virus gathered worldwide, zeroing in on a mutation called D614G.

"We were concerned that if the D614G mutation can increase transmissibility," the study authors wrote, "it might also impact severity of disease."

The corresponding author at the Los Alamos National Laboratory did not respond to an interview request from NBC News.

The hypothesis is concerning for a virus that has already infected millions and is responsible for more than 260,000 deaths worldwide.

But outside experts were quick to point out that changes in viruses — especially coronaviruses — are common, and may mean nothing at all.

Dr. Gregory Poland, director of the Mayo Clinic's Vaccine Research Group in Rochester, Minnesota, explained viral mutations using the analogy of an automobile.

"If the mutation takes out your carburetor, the car can no longer operate," Poland said. "On the other hand, if the mutation changes one spark plug, the car can still operate."

What's unclear is whether the D614G mutation slows or speeds the viral "car" or, in fact, does nothing.

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Heguy said the D614G mutation had already been identified in viral sequences from around the globe, particularly in Europe.

The researchers "used that for their model to see if there was an indication that this particular mutation ... would make it more transmissible. According to their model, it is possible," Heguy said. "Having said that, it is only a model."

That is, models only reflect what could possibly happen in the future. Scientists have not found the virus has evolved to become any more dangerous or deadly in people.

Mutations are common in viruses, but the coronavirus "so far has been pretty darn stable with little mutations around the edges," Dr. William Schaffner, an infectious diseases expert at the Vanderbilt University Medical Center in Nashville, said.

"That's what these investigators are looking at," Schaffner said. "They're trying to determine whether these little mutations have implications for how well it's transmitted." But, there is "no evidence that this is happening that I can see clinically," he added.

Dr. Robert Gallo, the co-founder and director of the Institute of Human Virology at the University of Maryland School of Medicine, said "the paper, I believe, is a strong paper by a quality group."

But, he said, "no conclusions can be made about biology or functionality" of the virus based on this study.

Potential implications

While the research may not be reflective of any impact on patients, scientists say it's still incredibly useful as a way to track how the virus acts over time.

Poland noted that experts tracking the virus through its genetic sequencing have found that while it is changing, it's not doing so very quickly.

"Unlike influenza, this virus accumulates mutations more slowly, which is a good thing," he said. "It gives us time to track it and to understand what's happening."

Rapidly mutating viruses make it more difficult for researchers to develop vaccines. Flu vaccines, for example, are notoriously difficult to get right because the various strains of influenza have a tendency to change and mutate quickly.

If this virus were to follow suit, it might mean trouble for ongoing COVID-19 vaccine research.

"It's possible that you'll get vaccines early enough and quick enough to prevent [a person's] first infection with the coronavirus," Gallo said. "We may look like heroes that stop this early on."

But, if the virus mutates too much, and the vaccine proves to be a poor match to future strains of the coronavirus, "we may be chasing our tail like with influenza. And that's not a bright prospect with a virus that is already so infectious."