A global study has found clear evidence that a new form of the coronavirus has spread from Europe to the US. The new mutation makes the virus more infectious but does not seem to make people any sicker, an international team of researchers reported Thursday.
The mutation affects the spike protein — the structure the virus uses to get into the cells it infects. Now the researchers are checking to see if this affects whether the virus can be controlled by a vaccine. Current vaccines being tested mostly target the spike protein.
The study, published in the journal Cell, confirms earlier work suggesting the mutation had made the new variant of virus more common. The researchers call the new mutation G614, and they show that it has almost completely replaced the first version to spread in Europe and the US, one called D614.
“Our global tracking data show that the G614 variant in Spike has spread faster than D614,” theoretical biologist Bette Korber of Los Alamos National Laboratory and colleagues wrote in their report. “We interpret this to mean that the virus is likely to be more infectious,” they add. “Interestingly, we did not find evidence of G614 impact on disease severity.”
What this means: This could be good news, said Lawrence Young, a professor of medical oncology at the UK’s University of Warwick, who was not involved in the study. “The current work suggests that while the G614 variant may be more infectious, it is not more pathogenic. There is a hope that as SARS-CoV-2 infection spreads, the virus might become less pathogenic,” he said in a statement.
About the study: The team tested samples taken from patients across Europe and the US and sequenced the genomes. They compared these genome sequences to what’s been shared publicly. Comparing these sequences helped them draw a map of the spread of the two forms.
“Through March 1, 2020 the G614 variant was rare outside of Europe, but the end of March it had increased in frequency worldwide,” they wrote.
Even when the D614 form had caused widespread epidemics, in places such as Wales and Nottingham in England, as well as in Washington state, G614 took over once it appeared, they found.
“The increase in G614 frequency often continues well after stay-at-home orders are in place and past the subsequent two-week incubation period,” they added.
The new version seems to multiply faster in the upper respiratory tract — the nose, sinuses and throat – which would explain why it passes around more easily, the researchers said. But tests on 1,000 hospitalized coronavirus patients showed those infected with the new version did not fare any worse than those who caught the original strain.
Other mutations often go along with the G614 mutation, but it’s not clear what effect they have. “The earliest sequence we detected that carried all 4 mutations was sampled in Italy on Feb. 20,” they wrote. “Within days, this haplotype was sampled in many countries in Europe.
The G614 mutation can be neutralized by convalescent serum – the blood product taken from people who have recovered from a coronavirus infection, the researchers said.
“But it will be important to determine whether the D614 and G614 forms of SARS-CoV-2 are differentially sensitive to neutralization by vaccine-elicited antibodies or by antibodies produced in response to infection with either form of the virus,” they added.
More work is needed, of course, to solidify the findings and to see what the changes mean for the epidemic and for patients, the researchers said.