November 30, 2022

A new subvariant is spreading rapidly in the United States.

7 min read


In early 2021, scientists in Colombia discovered a worrying new strain of the corona virus. This type, ultimately known as Mu, had a number of disturbing variations that experts thought could help the immune system avoid defenses.

In the following months, Mu spread rapidly in Colombia, Covid 19 is a new addition to the case.. By the end of August, it was known in dozens of countries and the World Health Organization. He was nominated “A kind of interest.”

“Mu was making some noise globally,” said Joseph Fower, a genomic epidemiologist at the University of Nebraska Medical Center and its author. A recent study on variables.

And then he got upset. Today, everything is different.

For each delta or اومیکرون A gamma, Iota or Mu, is a variety that gave rise to local growth but never reached global dominance. Experts say that while understanding Omicron is a top public health priority, there is a need to learn from these low ancestry.

Joel Wertheim, a molecular epidemiologist at the University of California, San Diego, said “there is no incentive to stop the virus from adopting and developing.” “And seeing how it has done in the past will help us prepare for what it can do in the future.”

Even-Rains’ study sheds light on surveillance differences and policy errors – provides further evidence that US international travel restrictions were not effective – and suggests that the virus is successful. That in the early stages of the epidemic, transmission was more important. Compared to immune theft.

The research also sheds light on the importance of context. The variety that affects some places never sets foot in others. As a result, it is difficult to predict which species will prevail, and will require comprehensive, almost real-time monitoring to stay ahead of future variations and pathogens.

“We can gain a lot by looking at the viral genomic sequence and saying, ‘This is probably worse than the other,'” said Dr. Wertheim. “But the only way to know for sure is to watch it spread, because there are so many potentially dangerous species that can never be caught.”

Looking at Mu here

Of Corona virus It is constantly changing, and most new species never appear or take names. But other people sound the alarm, either because they are becoming more common or because their genomes look ugly.

Both were right about Mu because it had spread to Colombia. “There were some variations that people were watching very closely,” said Marie Petron, a genomic epidemiologist at the University of Sydney and author of the new Mu paper. Numerous mutations in its spike protein were documented in other immune variables, including beta and gamma.

In a new study, which has not yet been published in a scientific journal, scientists compared the biological properties of Mu to alpha, beta, delta, gamma and the original virus. Dr. Fowler said that Mu did not replicate faster than any other type, but it was the group’s strongest immune system – more resistant to antibodies than any other known type except omecron.

Credit …Vanessa Jimenez / Agence France-Presse – Getty Images

By analyzing the genomic sequence of mu samples collected from around the world, the researchers reconstructed the different types of proliferation. They concluded that Mu may have emerged in South America in mid-2020. Then it kept circulating for months before it was discovered.

Genomic surveillance was “complex and incomplete” in many parts of South America. Jesse Bloom, a viral evolutionist at the Fred Hutchinson Cancer Research Center in Seattle. “If there had been better surveillance in these areas, it would probably have been easier to gauge how much people are worried about Mu.”

Mu presented another challenge. This involves a type of mutation called a frame shift mutation, which was rare in coronavirus specimens. Such variations were marked as errors when scientists, including Dr. Fower, attempted to upload their Mu configuration. GISAIDAn international repository of the viral genome used to track new species.

This complication led to a delay in the public participation of the Mu continuity. The researchers found that when the virus sample was collected from the patient and when it was made publicly available on GISAID, it was consistently longer for Mu cases than for Delta cases.

“The genome was essentially creating an artificial surveillance space,” said Dr. Fowler. “The result is that, at least in our experience, when we’re usually trying to get it out in days, we don’t get the data for weeks.”

(GISAID’s quality control systems are important, the researchers emphasize, and the stock has solved the problem.)

Combine these sects of surveillance with Mu’s defensive behavior and it seems that its form is ready to disappear. But that did not happen. Scientists found that instead, Mu spread from South and Central America to other continents but did not circulate widely after arriving there. “This is an indication that this variant may not fit as well as we would expect in North American and European populations,” said Dr. Petron.

This was possible because Mu found himself competing with an even stronger type: Delta. Unlike Delta Moo, it was not as skilled at evading antibodies, but it was more transferable. “So, in the end, the delta spread out,” said Dr. Bloom.

Credit …Shannon Stapleton / Reuters

The right kind, the right time

Studying successful variables tells only half the story. “Different situations that do not prevail are, in a way, negative controls,” said Dr. Petron. “They tell us what’s not working, and, doing so, helps fill the knowledge gap about different fitness.”

Delta outperformed many other immune variables besides Mu, including beta, gamma and lambda. This pattern suggests that immune theft alone was not enough to allow a species to progress beyond the highly transmissible version of the virus – or at least not during the early stages of the epidemic, when very few people Was exempt.

But the wave of vaccinations and infections has changed the immune system. Scientists say that a highly immune-resistant variety should now have the upper hand, which is probably part of the reason why Omicron has been so successful.

Another recent study found that Gamma, an immune defender in New York City There was a tendency to improve In pre-existing high-level neighborhoods, in some cases because they were severely affected by the first coveted wave. “We can’t see a new species in space, because it comes in the shadow of all the species that came before it,” said Dr. Wertheim, author of the study.

In fact, the clash of variations of the past shows that success depends on context. For example, New York City Iota may have a variety of birthplaces, which It was first discovered In virus samples collected in November 2020. “And that’s how he got his start,” said Dr. Petron. Even after the arrival of the more mobile alpha variant, Iota remained the dominant variant of the city for months, before it was exhausted.

But in Connecticut, where both Iota and Alpha appeared in January 2021, things turned out differently. “Alpha flew immediately, and Iota had no chance,” said Dr. Petron. Study of variables in both regions.

Credit …Andre Coelho / EPA, via Shutterstock

A similar pattern has already begun to play out with the various lineages of Omekron. In the United States, BA.2.12.1, the first identified subtype in New York, Has taken offWhile in South Africa, BA.4 and BA.5 are a new addition..

This is another reason to study the diversity, said Sarah Otto, an evolutionary biologist at the University of British Columbia. One variable that was poorly matched for a particular time and place can be moved to another. In fact, Mu’s misfortune was that it soon emerged. “There may not be many people who really have an exemption for this type of promotion.” Dr. Otto said.

But the next type of concern could be the offspring of an immune lineage or something similar that has never fully taken hold, he said.

A look at past variations can also provide insight into what worked – or didn’t – work to incorporate them. The new gamma study provides further evidence that International travel restrictionsAt least as the United States has implemented them, it is unlikely to stop any kind of globalization.

Gamma was first identified in Brazil in late 2020. In May of the same year, The United States has barred most non-U.S. Citizens from traveling in the country from Brazil, a ban that remains in place Until November 2021. Nevertheless, Gamma was discovered in the United States in January 2021 and soon spread to dozens of states.

Since gamma has never dominated the world, a study of its spread provided a “clear” picture of the effect of travel restrictions. Said Tatiana Vasileva, a molecular epidemiologist at the University of California, San Diego and author of the study. “When it comes to studying different species, let’s say, Delta – something that has created a huge epidemic everywhere – it’s really hard to find specimens at times, because it’s so large and It happens very fast, “he said. .

Dr. Fower said that in the current global health emergency, with a virus that is changing rapidly, there is an understandable desire to focus on the future. And as the world’s attention shifted to Delta and then to Omicron, he and his colleagues discussed whether to continue reading the old news.

“We were like, ‘Does anyone care about Mu now?'” Dr. Fower recalled. “But we think there is still room for high-quality studies that ask questions about previous types of anxiety and try to look at what happened.”



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