Has the new coronavirus mutated to be more contagious? Experts weigh in
TORONTO -- Scientists are cautioning that it’s still too early to know how the novel coronavirus (SARS-CoV-2) mutates, after a preliminary study in the U.S. claimed that a new strain of the virus has emerged that is more dominant and contagious than the original.
The preprint study by scientists at Los Alamos National Laboratory in New Mexico was published Tuesday on BioRxiv, a website for academics to share their research before it’s peer-reviewed.
In the paper, the scientists said they discovered a new strain of the coronavirus, which first appeared in Europe in February. Since then, the new strain migrated to the U.S. East Coast and other regions and has become the dominant form of the virus in the world, according to the researchers.
The study’s authors said this one particular mutation, named D614G, appears to be more contagious than its predecessors because it has quickly infected more people than earlier strains of the virus that first emerged in Wuhan, China.
The scientists came to this conclusion by analyzing more than 6,000 coronavirus sequences from around the world, which were collected by the German-based organization the Global Initiative for Sharing All Influenza Data (GISAID).
They tracked the virus across different regions since its emergence and said they identified 14 mutations related to the now-infamous spike protein that is visible on the surface of the virus. They focused their attention on the spike protein because this is what allows the virus to enter human respiratory cells.
Of the mutations they discovered, the researchers said D614G appeared to be of the most concern because it became dominant wherever it was spread, although they said it’s still unclear why that is.
What’s more, the study didn’t show that the mutated strain of the virus actually made people sicker. The team studied data from 453 hospitalized patients in Sheffield, England and found that, while people with the particular mutation had higher viral loads in their samples, they weren’t sicker or in the hospital for longer periods.
“There was, however, no significant correlation found between D614G status and hospitalization status,” the study said.
While the academics didn’t suggest the mutated strain was more lethal than its predecessors, they did warn of a possible risk that coronavirus patients will be “susceptible to a second infection” if they believe they have immunity to the virus after being infected with only one strain of it.
The scientists said the newly discovered strain was of “urgent concern” as it could have important implications for vaccine development already underway if those scientists are not aware of its mutated form.
‘WE NEED MORE INFORMATION’
While the suggestion of a more virulent mutated strain of coronavirus might stoke fears, experts in the field say more evidence is needed to prove its existence.
Rob Kozak, a clinical microbiologist at Sunnybrook Hospital who helped isolate SARS-CoV-2 in March, said the fact that the virus is mutating is not a cause for alarm because all viruses mutate as part of their life cycles. He explained that when a virus makes contact with a host, it will make new copies of itself so it can go on to infect other cells.
“As the virus replicates, it makes mistakes in copying itself and some of these mistakes will accumulate over time,” he told CTVNews.ca during a telephone interview on Thursday. “It will replace one nucleic acid with another just by accident, so that the genome of the virus at the beginning of a flu season, for example, is going to be a little bit different from the one at the end.”
For the most part, mutations tend to be neutral and will have only a slight effect on how the virus functions. In some cases, mutations may actually weaken a virus and cause it to peter out.
On rare occasions, a mutation can benefit the virus and help it to proliferate, as the study suggests is happening with COVID-19.
Dr. Isaac Bogoch, an infectious diseases physician and scientist with the Toronto General Hospital, said the study didn’t prove that the mutated strain is more virulent just because it was more common in their sample size.
“It’s not to say it can’t happen. It’s not to say it won’t happen, but they don’t provide the level of proof to determine that this has happened,” he said.
“It’s not that a mutation didn't occur. It’s not that there aren’t different variants of this virus around. But does this mutation confer some special advantage over other strains of this virus? And the answer is maybe, maybe not, but they don’t show that in this paper.”
Kozak said the researchers can’t prove that the mutation is associated with better transmission or more virulence until they start doing rigorous scientific experiments using animals and cell cultures.
“Mutations on their own don’t really mean anything until we actually do proper animal models and proper scientific experiments to understand it,” he said.
Kozak also said the study’s sample size of genomes comprised of only about one per cent of all the viruses out there from coronavirus, which has infected more than 3.8 million people globally.
“We’re not really getting a very fulsome picture of everything that’s there,” he said.
The microbiologist said the study also didn’t take into account epidemiological factors, such as how those with the virus isolated themselves or if they travelled extensively while they were infected.
“If a country really locked down, put in social distancing, insisted that businesses be shut down, you’d probably see there might be less transmission of a particular virus based on that,” he explained.
As for the study’s potential impact on vaccine development, the team from Los Alamos National Laboratory explained that was why they published the results of their research before it had been peer-reviewed.
“These findings have important implications for SARS-CoV-2 transmission, pathogenesis and immune interventions,” the authors wrote.
Bette Korber, a computational biologist and the study’s lead author, did not respond to a CTVNews.ca request for comment.
While Kozak agreed that sharing data is a good idea because it stimulates discussion and new ideas within the scientific community, he said it’s important to remember some of the study’s limitations and that it hasn’t undergone that proper peer-review process.
“It’s always a balance because you want to put information out there because maybe it’ll be helpful to people,” he said. “But it’s a risk when people don’t say ‘We got to take this with a grain of salt. We need to not jump to conclusions. We need more information before we can really make a conclusion.”