Coronavirus mutations not (necessarily) cause for alarm

Recent mutation, one of many, may increase infectiousness, but doesn’t seem to increase COVID-19 severity.
August 20th, 2020
man looking into a microscope at coronavirus mutation, while DNA shows on the screen.
The coronavirus’s RNA genome consists of about 30,000 base pairs. Since Chinese scientists first decoded the virus’s genetic code in December, it has accumulated an average of one or two random mutations a month. Source: Getty Images.

Organisms mutate. That’s often a good thing. If it weren’t for mutations, we might all still be single-celled organisms clinging to hydrothermal vents in the ocean’s black depths.

Mutations – random, inevitable changes to life’s genomic code – don’t always turn slime into Shakespeare, though. Viruses mutate also.

SARS-CoV-2, the virus behind the COVID-19 pandemic, is no exception. The coronavirus’s RNA genome consists of about 30,000 base pairs. Since Chinese scientists first decoded the virus’s genetic code in December, it has accumulated an average of one or two random mutations a month. One in particular, called D614G, may well have boosted disease’s infectiousness.

That particular coronavirus mutation has raised questions about the future of the coronavirus – and, by extension, the possible impact on the civilization the virus has attacked.

Viral mutations come and gone

Viral mutations have been well documented. The 1918 Spanish flu pandemic was caused by a virus that mutated (probably from waterfowl who weren’t bothered by it) to infect humans. That virus, H1N1, hung around in people until 1957, when some combination of mutations and increasing immunity caused it to fade from our species. In 1977, a mutated version of H1N1 emerged again and jumped from pigs to humans in China. The same thing happened in 2009, causing the H1N1 swine flu outbreak. That H1N1 strain still circulates as a seasonal flu virus whose mutations have now changed fully 15 percent of the original Spanish flu genome. The good news: in general, H1N1 has become less virulent with time.

That’s not by chance. If you’re a virus with the sole goal of proliferating as widely as possible, mutating to cause a mellower infection makes sense. (Even HIV may be evolving into a less-dangerous form.)

view of the coronavirus mutation
A computer model of the spike protein of the SARS-CoV-2. A recently identified mutation subtly changed the spike’s shape and, probably, made the coronavirus more contagious. Image courtesy of NIH and UT Austin/McClellan Lab.

“In general, viruses do want to replicate better and faster and spread themselves faster,” said Dr. Thomas Campbell, a University of Colorado School of Medicine and UCHealth infectious-disease specialist.

But other flu types have mutated less happily for humans. H3N2, another seasonal flu, originated in Hong Kong in 1968 and has mutated such that the antibodies that normally alert our immune system to the virus have a hard time binding to it. H3N2 influenza now almost universally has that mutation, one was first detected during the 2014-2015 flu season.

The D614G coronavirus mutation spread even faster. At some point earlier this year, an A changed to a G at position 23,403 of the coronavirus’s RNA genome. It was a classic random mutation, one that could have hurt the virus’s fitness, helped it, or made no difference at all. In this case, the mutation subtly changed the shape of the necks of the spike proteins protruding from it.

One research team investigating the mutation in a lab has concluded that the change made the spike stronger and therefore better able to maintain its shape and bind like a key to the lock of a human cell’s ACE2 receptors. That team’s conclusion followed that of the team that had reported the mutation in the journal Cell. The mutation made the G614 version of the coronavirus perhaps 10 times more likely to spread, cell-for-cell in a lab setting, than the original D614 coronavirus that took root in China.

Today, pretty much every coronavirus case has the G614 mutation.

Bad news and good news about coronavirus mutation

In a commentary accompanying the Cell study’s findings, scientists noted that the new variant’s vastly greater infectiousness in the lab doesn’t necessarily translate into the same thing in the noses and lungs of human beings. In addition, the G614 mutation that became dominant could also have done so through random chance – combined with the fact that Chinese spread of disease with the D614 variant had slowed to a trickle by the time the G614 version was rampaging through Europe, the United States and beyond. But from what we know about Darwinism, the mutation probably conferred a competitive advantage.

If the bad news is that the mutation probably makes the coronavirus more infectious and therefore hard to stop its spread, the good news is that the mutation doesn’t appear to make the disease of COVID–19 more severe. And while D614G mutation changes slightly the shape of the coronavirus’s notorious surface-spike proteins, the change doesn’t appear to impact the binding site atop of the protein spike. That binding site is what SARS-CoV-2 viruses use to unlock human cells – and it’s also the primary target of the most promising vaccine-development efforts.

Dr. Campbell talks about coronavirus mutation.
Dr. Thomas Campbell, a University of Colorado School of Medicine and UCHealth infectious-disease specialist.

“The mutation seems to have spread more rapidly around the world than the original virus that was first described in Wuhan, China, in December,” Campbell said. “As far as we know, this specific mutation should not affect the efficacy of vaccines as it’s not located at the part of the spike protein where vaccines would have their specific effect.”

Mutations can bedevil vaccine developers, though, says Campbell, who is leading the Colorado site of the major Moderna vaccine trial.

Mutations have been “a huge issue for developing an HIV vaccine, and it’s also an issue with influenza vaccines,” Campbell said. “It’s a big reason why we have to have a different flu shot every year.”

Thanks to built-in error-correction, the novel coronavirus mutates slower than HIV and influenza viruses. That doesn’t necessarily translate into an easier path to a vaccine – any more than rapidly mutating viruses such as measles thwarted vaccine developers.

For now, the coronavirus has no need to evolve anyway. In a few short months, SARS-CoV-2 has taken up residence in all corners of the planet (save, for now, Antarctica). It took the single-celled vent-dwellers that became ants, oak trees, and us about four billion years to do the same.

About the author

Since 2008, Todd Neff has written hundreds of stories for University of Colorado Hospital and UCHealth. He covered science and the environment for the Daily Camera in Boulder, Colorado, and has taught narrative nonfiction at the University of Colorado. He was a 2007-2008 Ted Scripps Fellowship recipient in Environmental Journalism at CU.

His latest book, "The Laser That’s Changing the World," tells the story of the inventors and innovators who saw, and ultimately realized, the potential of lidar to help solve problems ranging from smokestack-pollution detection, ice-sheet mapping, disaster recovery, and, ultimately, autonomous-vehicle guidance, among many other uses. His first book, "From Jars to the Stars," recounts how Ball Aerospace evolved from an Indiana jar company - and a group of students in a University of Colorado basement - to an organization that managed to blast a sizable crater in the comet 9P/Tempel 1. "Jars" won the Colorado Book Award for History in 2012.

Todd graduated with a business degree from the University of Michigan, where he played soccer, and with a master’s degree from the Fletcher School of Law and Diplomacy at Tufts University. Before becoming a journalist at the turn of the millennium, he was an IT and strategy consultant. He once spoke fluent Japanese and still speaks fluent German.

When not writing, he spends time with teenage daughters and wife Carol, plays soccer, and allows himself to be bullied by a puggle he outweighs by a factor of seven.