A global study has found strong evidence that a new form of the coronavirus has spread from Europe to the United States. The new mutation makes the virus more likely to infect humans but does not appear to make them sicker than previous variations of the virus, an international research group reported on Thursday.
“It’s now the dominant form that infects people,” Erica Ollmann Saphire of the La Jolla Institute for Immunology and the Coronavirus Immunotherapy Consortium, who worked on the study, told CNN.
“This is now the virus.”
The study, published in the journal Cell, is based on some previous work done by the team that was released on a suppression server earlier this year. Shared information about genetic sequences showed that a certain mutant version of the virus took over.
Now the team has not only checked more genetic sequences, but they have also conducted experiments involving humans, animals and cells in lab dishes that show that the mutated version is more common and that it is more infectious than other versions.
“We know that the new virus is fitter. At first glance, it doesn̵
The mutation affects the spike protein – the structure the virus uses to enter the cells it infects. Researchers are now investigating whether this affects whether the virus can be controlled by a vaccine. Current vaccines being tested are mainly targeted to the nail protein, but they were manufactured with older virus strains.
The study, published in the journal Cell, confirms previous work suggesting that the mutation had made the new virus variant more common. The researchers call the new mutation G614, and they show that it has almost completely replaced the first version spread in Europe and the United States, one called D614.
No effect on patient survival
“Our global tracking data shows that the G614 variant in Spike has spread faster than the D614,” wrote theoretical biologist Bette Korber of the Los Alamos National Laboratory and colleagues in her report. “We interpret this to mean that the virus is likely to be more infectious,” they added. “Interestingly, we found no evidence of G614’s impact on the severity of the disease.”
This may be good news, says Lawrence Young, professor of medical oncology at the University of the UK in Warwick, who did not participate in the study.
“The current work suggests that although the G614 variant may be more infectious, it is no longer pathogenic. There is hope that as the SARS-CoV-2 infection spreads, the virus can become less pathogenic, he said in a statement.
The team tested samples taken from patients across Europe and the US and sequenced the genomes. They compared these genome sequences to what was shared publicly. Comparison of these sequences helped them draw a map of the distribution of the two forms.
“Even on March 1, 2020, the G614 variant was rare outside of Europe, but by the end of March it had increased in frequency worldwide,” they wrote.
Even when the D614 form had caused widespread epidemics, in places like Wales and Nottingham in England, as well as in the state of Washington, the G614 took over as it turned out, they found.
“The increase in G614 frequency often continues long after home-home orders are in place and past the subsequent two-week incubation period,” they added. There are a few exceptions, including the Santa Clara, California, area and Iceland, where the older D614 form was never replaced by the newer G variant.
Three to nine times more contagious
The new version seems to multiply faster in the upper respiratory tract – the nose, sinuses and throat – which would explain why it passes more easily, the researchers say.
But tests on 1,000 hospitalized coronavirus patients in the UK showed that those infected with the new version did not fare any worse than those who received the original strain.
David Montefiore from Duke University and colleagues tested the virus in the lab. “We were able to test if the G-form of the virus was more infectious than the D-form,” Montefiore, director of the AIDS Vaccine Research and Development Laboratory, told CNN.
“All results agreed that the G-shape was three to nine times more infectious than the D-shape,” he added. “We now had experimental evidence that partially supported what Bette saw in her analysis of sequences worldwide – the G-shape had a fitness advantage in terms of infectivity.”
The laboratory tests of the virus in action confirmed what the genetic maps showed.
“These findings suggest that the newer form of the virus can be transmitted even easier than the original form. Whether or not that conclusion is ultimately confirmed, it highlights the value of what were already good ideas: wearing masks and maintaining social distance, Korber said in a statement.
Other mutations often go with the G614 mutation, but it is not clear what effect they have. “The earliest sequence we discovered carrying all four mutations was tested in Italy on February 20,” they wrote. “Within a few days, this haplotype was tested in many European countries.”
The G614 mutation can be neutralized by convalescent serum – the blood product taken from people who have recovered from a coronavirus infection, Saphire said. Her team tested blood donated by six coronavirus survivors in San Diego.
“We looked to see if the number of antibodies in human blood was as effective in neutralizing the new virus as the old virus and it was. It was actually a little better, she said.
“It was a relief.”
The researchers had been worried that if the new mutation caused the virus to grow faster and to higher levels, it would require more immune system efforts to neutralize it. “In these six San Diegans that was not the case,” Saphire said.
Of course, more work is needed to solidify the results and to see what the changes mean for the epidemic and for patients, the researchers said.
“There are potential consequences for the vaccines. We are actively investigating the possible consequences, Montefiore said.
And of course they keep an eye on other mutations. “We may have avoided a bullet with this specific mutation,” said Saphire. “But that’s not to say that another mutation couldn’t get on top of this,” she added.
“That would require us to remain vigilant.”
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