- Scientists are tracking genetic errors, or
mutations , in the coronavirus' genome to study its evolution over time. - The virus has mutated as it spread worldwide, but the mutations haven't impacted how dangerous it is, experts say.
- The mutations are actually useful: Knowing the virus' history enables researchers to study where it originated and how it traveled.
- The new
coronavirus mutates slowly, which means a vaccine would most likely be effective long-term. - Visit Business Insider's homepage for more stories.
Emma Hodcroft spends a lot of time looking for typos, but not in the grammatical sense. Instead, she hunts for minute errors in one of the most important genomes in the world: that of the coronavirus.
"These typos help us track the virus and build a family tree of all the different samples we've collected," Hodcroft told Business Insider.
A geneticist at the University of Basel in Switzerland, Hodcroft and her colleagues differentiate their samples based on tiny mutations that get introduced into the virus' genetic codes as it replicates and spreads.
These mutations break a virus into separate trackable strains — a word that geneticists simply use to differentiate samples that aren't identical — whose spread can be mapped over time.
According to Hodcroft, the coronavirus' mutations are innocuous in terms of its risk to humans, at least so far. But they do help geneticists trace the virus' history in order to figure out how it got to and spread within the US, for example. Studying the virus' mutations also inform future vaccine development.
Tracking the coronavirus' spread
When labs around the world collect coronavirus samples, they sequence those samples' genomes and upload the information to Hodcroft's team's website — the project is called Nextstrain. Currently, Nextstrain has coronavirus samples from at least 36 countries on six continents. The group has divided these samples into genetic bins characterized by certain "typos."
The researchers use that sorting method to pinpoint how and when the virus came to different countries.
"It tells us how different outbreaks are connected and whether a particular outbreak is really a superposition of many small outbreaks or has a single source," Richard Neher, a molecular epidemiologist with Nextstrain, told Business Insider. "The
Nextstrain's maps also suggest the cases on the US's West and East Coasts came from different geographic sources.
"There were multiple paths the virus took to reach the US. There was a direct introduction from China that occurred in late Jan and there were multiple introductions from the European epidemic that occurred during the course of Feb," Trevor Bedford, an infectious-disease researcher in Washington state and co-developer of the Nextstrain platform, tweeted on April 12.
Hodcroft said she also thinks the cluster of infections that cropped up in the Seattle area came from China, while infections in the eastern US were linked to Europe.
According to The New York Times, genetic mapping has also revealed that the coronavirus strain in the US's first reported case — a patient in Snohomish County, Washington — was the same as those found later in cases of community transmission in the state. A strain that descended from that Washington one also cropped up in coronavirus samples in 14 other states, including Maryland.
But Hodcroft noted that Nextstrain still has too few coronavirus samples to draw major conclusions.
"We have 5,000 sequences, but that's a drop in the bucket of all these cases worldwide," she said. (More than 2.5 million infections have been reported since December.) "We can't discount that we may be missing transmission links in the middle."
One study shows European travelers brought the coronavirus to New York City
A preliminary study, which has yet to be peer-reviewed, found via a similar process of genetic analysis that the coronavirus was circulating in New York weeks before its first reported case on March 1. The research, from the Icahn School of Medicine at Mount Sinai, also revealed multiple introductions of the virus to New York City, mainly from Europe and other parts of the US.
Going forward, Hodcroft wants to more robustly map how the virus spread across North America. Preliminary mapping suggests it may have bounced from Washington state to Canada, then to Connecticut, but her team can't be sure until they get more samples from Americans who got sick during the early days of the outbreak.
"Knowing this route is important so we can prevent a repeat of old mistakes," Hodcroft said. She added, "this virus is not clever — whatever routes it used to transmit successfully in the past will be the same routes it uses again. It's those transmission routes that we need to pay attention to in the future."
The coronavirus is mutating, but slowly and in non-dangerous ways
The notion that multiple coronavirus strains are circulating has caused some concern about the virus' potential to morph into an even more dangerous, virulent threat.
A non-peer-reviewed study published on Sunday suggested that there were 30 strains of the coronavirus out there. But even that's not cause for concern, according to Hodcroft, since subtle differences between strains don't tend to affect how contagious a particular version of the virus is or how it spreads.
All viruses, including the coronavirus, mutate over time because as they replicate, minute errors are introduced into their genetic codes. Most viral mutations are innocuous. But some — those that help a virus spread quicker, or infect more people — can affect the severity of an outbreak. A mutation is most likely what enabled this coronavirus to jump from its original host species (probably bats) to other animals, including us.
But in this case, the typos haven't changed how the COVID-19 virus infects its hosts, or how dangerous it is.
Plus, Hodcroft and her colleagues have so far found that the virus's genome — which is made up of more than 29,000 complimentary molecules — mutates slowly, at least compared to the flu. So people shouldn't worry about it mutating out of control, she said.
"Even if we take the two most different novel coronavirus strains, we find that they're separated by about 40 differences over the course of 29,000," Hodcroft added.
The fact that the virus is nearly identical everywhere it has popped up is good
A slow mutation rate may mean a vaccine works for longer
The current form of the virus is stable for good reason, Hodcroft said.
"There's no need for the virus to diversify — it's spreading incredibly well between humans, and not under a lot of selection pressure to change," she said. "The virus already has asymptomatic transmission, there's nothing more it could do to get even more off the testing radar than it already has."
The coronavirus's slow mutation rate, however, increases the chance that when a vaccine is finally rolled out, it will remain effective for a long time — years, according to Bedford.
He tweeted last month that "it will take the virus a few years to mutate enough to significantly hinder a vaccine."
However, it's possible that the virus could mutate following the widespread use of a vaccine, necessitating occasional vaccine updates, according to Hodcroft. That's when her team's work in tracking its genetic changes will come in handy once again.
"We will need to watch out for mutations that will make that vaccine less effective," she said.
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