New Mutation Sped Up Spread of Coronavirus
November 13, 2020 – The virus that causes COVID-19 is not the same strain that first emerged from China. A new study shows it’s changed slightly in a way that makes it more contagious to humans.
Compared to the original strain, people infected with the new strain – called 614G – have higher viral loads in their nose and throat, although they don’t seem to get any sicker. But they are much more contagious to others.
“It makes sense,” says Ralph Baric, PhD, professor of epidemiology, microbiology and immunology at the University of North Carolina at Chapel Hill.
The new strain has changed its spike proteins – the regions of its outer shell that attach to and infect our cells. The change makes them a much more efficient predator. It moves quickly from cell to cell in our body, copying itself at a breakneck pace.
Baric’s experiments help explain why strain 614G, which first appeared in Europe in February, quickly dominated global release.
He says the virus likely got out of bats and discovered a whole new population of human hosts, with more than 7 billion of us on the planet to infect. None of us have an immune defense against this, so we are prime targets. Viruses with genetic advantages that help them copy themselves faster and jump between hosts faster are the versions that survive and will be passed on.
“So it can pass from person to person, it will be the most competitive virus in terms of maintaining the virus,” says Baric, one of the world’s leading coronavirus experts. His new study is published in the journal Science.
The new study confirms previous research by a team of scientists led by Bette Korber, PhD, at the Los Alamos National Laboratory in New Mexico. The team first noticed the rapid spread of the new strain and wondered if the virus was evolving to spread more easily between people.
In new experiments, animals infected with the new strain 614G transmitted it much faster to healthy animals than those infected with the original strain.
Researchers at the University of Wisconsin at Madison infected 16 hamsters with the SARS-CoV-2 virus. Eight hamsters were infected with the new strain 614G. Eight more were infected with the original strain which was first identified in China. Each infected hamster was paired with a healthy hamster that was separated by a partition in a cage so that the animals could not touch each other but breathed the same air. By day two of the experiment, five of eight healthy hamsters sharing air with animals infected with strain 614G had become ill and were shedding virus themselves, but none of the healthy hamsters associated with those infected with strain d. he originally fell ill. . The original strain eventually sickened the healthy animals, but it took 2 more days for this to happen, proving that the changes helped speed the spread of the virus.
Baric and his team also questioned whether changes in the structure of the virus would affect how future therapies – including a vaccine – might work against it, since all treatments currently in development were designed to counter the original strain that emerged. from China.
They tested antibodies taken from the blood of people who had survived COVID-19 infections on the new and old strains, and they found no significant difference in the effectiveness of these antibodies to neutralize the virus.
This is good news, because it means that people recovering from infection with the original strain may still have some protection against the new strain.
In the United States, the original strain was imported from China and began to circulate on the west coast, while the new strain was imported from Europeans who traveled mainly to New York and the rest of the coast. is.
Baric and his team also tested the antibodies that are developed as treatments to give people passive immunity to the virus. These seemed to work well too.
“The vaccines, which are all based on the original Chinese strain, make a good immune response that protects against that strain, so that’s good news,” he says.
While current treatments and prevention efforts don’t appear to be much affected by this change in the virus, the mutation raises questions about how quickly new strains emerge and whether or not any of them might be causing a problem. in the future, says Baric. .
Coronaviruses, as a group, are extremely stable. They have a special molecule – aptly called a proofreader – that ensures the virus is copied correctly.
Because of this proofreader, the speed of emergence of these new strains of the novel coronavirus has been somewhat surprising to scientists studying them.
A development that Baric and other scientists are watching closely is the emergence of new strains found in mink farms in Denmark and the Netherlands that infect humans.
Work is underway to confirm that at least one of these strains – the so-called cluster 5 virus – may have evolved enough changes in its spike proteins to help it escape the vaccine.
Baric says the research needs to be verified, but early work suggests the virus appears to have changed to help it infect minks more efficiently, while retaining its ability to infect humans.
When a virus evolves in a way that allows it to circulate in an animal species, “it becomes more difficult to eradicate that virus,” he says.
Baric says that if the virus continued to be transmitted in mink, if we vaccinated everyone in Denmark, but left the minks, the virus would hang around until there were enough new susceptible hosts – usually young children – then would fall back into humans. .
Because of this, he says mink farms may need to take other measures, such as vaccinating their animals or, in the worst case, killing their mink, to control the spread.
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