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  • - [Narrator] New coronavirus variants

  • have been detected in over 40 countries,

  • including the UK, South Africa, Nigeria and Brazil

  • where they first emerged.

  • - Now health officials say a new threat

  • is identified in South Africa.

  • - British officials imposed a new lockdown across England.

  • - Recent reports of a highly contagious coronavirus variant

  • in the United States.

  • - [Narrator] In the US, multiple states

  • have reported new variants

  • or versions of the virus with mutations

  • that could change how it spreads.

  • New research suggests

  • that some of these variants are highly transmissible

  • and at least one may reduce how well vaccines work.

  • With countries around the world

  • already facing escalating infections

  • and overwhelmed hospitals,

  • these mutations could make ending

  • the pandemic more difficult.

  • We'll explain.

  • Like other viruses, the coronavirus spreads

  • by infecting cells and then reproducing within them,

  • creating copies of itself that spread throughout the body.

  • As new versions are made, the virus' genetic code,

  • which holds the instructions

  • for building new virus particles is copied over

  • and over again.

  • But the code isn't always reproduced correctly.

  • Small genetic mistakes or mutations

  • can create new viral variants.

  • If the new version of the virus has mutations

  • that allow it to spread faster

  • than the current most common variant,

  • it could lead to a surge in new cases.

  • This is already happening in places

  • like the UK and South Africa

  • where some of the newest ones were first found.

  • Current data suggests that the UK variant

  • could be 50% to 70% more transmissible

  • but the research is still early.

  • To determine how transmissible

  • and dangerous a virus mutation might be,

  • scientists run a series of experiments in the lab.

  • The first step is genetic sequencing.

  • - Genetic sequencing gets to the blueprint

  • of what the viruses are.

  • We can use samples and data

  • from actual humans to figure out

  • what the genetics of the viruses are.

  • - [Narrator] To do this, scientists take a sample

  • of the mutated virus and sequence its genes.

  • Then computation programs

  • help scientists identify mutations.

  • - Once we know what they are

  • and now we can see that oh well,

  • this is an important population,

  • we can start manipulating the virus.

  • We can either start working with clinical islets

  • of that virus or we can actually make the strains.

  • So putting those individual mutations

  • into the backbone of viruses that we already have.

  • - [Narrator] After sequencing the virus,

  • scientists test the variant in a lab.

  • - What we do is we compare how well the virus replicates

  • in different types of cells.

  • And so there are two ways.

  • We will just do infections and kind of measure the level

  • of the virus over time in these cell types.

  • And the other thing that we'll do is a competition,

  • where we'll take 50% of the wild type,

  • the original strain and 50% of the mutant strain

  • and then compare how well they grow.

  • If there's an advantage, we'll see that

  • that advantage 24 hours or after 48 hours,

  • one of the two might out compete.

  • - [Narrator] During lab experiments,

  • researchers can also test whether human antibodies created

  • by infection or vaccines

  • are effective at fighting the new form of the virus.

  • After culture testing,

  • scientists typically move on to animal models

  • and then sometimes to humans.

  • Right now, the research is still early

  • but scientists are beginning to get a clearer picture

  • of what these variants look like.

  • From sequencing, they know the UK variant

  • has 17 key mutations.

  • - These variants that we're seeing,

  • these changes give a small advantage

  • in terms of the ability of the virus

  • to replicate or transmit.

  • - [Narrator] This has a lot to do with the spike protein,

  • which is critical to how the virus spreads.

  • A portion of the spike bonds to a receptor

  • on human cells like a key fitting into a lock.

  • This enables it to enter and infect.

  • Scientists found that the UK variant's spike proteins

  • have eight amino acid changes.

  • Previous research appears to show

  • that some of these changes may be increasing

  • the protein's ability

  • to cling onto and enter human cells.

  • This could be making it more transmissible,

  • which means a higher vaccination rate may be needed

  • to reach herd immunity.

  • Another big question is the virulence

  • or how harmful these new versions of the virus could be.

  • Scientists say that most likely the new variants

  • don't cause a more severe form of COVID-19.

  • Another question is whether the new versions

  • will show up on tests.

  • Early data appears to show that most COVID

  • and antibody testing will continue to work.

  • - We should still be able to tell if you have COVID.

  • What's less clear is if we can tell

  • if you have a specific variant or not.

  • - [Narrator] The most pressing issue

  • is whether vaccines will still be effective.

  • For the UK variant, it appears that they will.

  • However, for the variant originating in South Africa,

  • preliminary data is worrying some scientists.

  • Researchers say that any of the more transmissible variants

  • could eventually become dominant.

  • - We've seen variants take over

  • in terms of the D614G mutation

  • and it wouldn't surprise me if the South African

  • or the UK variant do a similar thing

  • where it becomes a dominant variant around the world

  • just because of a small fitness advantage

  • or small changes that make the virus more fit.

  • - [Narrator] To try to stem the spread,

  • certain countries like the UK

  • have already imposed strict lockdown measures.

  • - The number of patients in hospitals in England

  • is now 40% higher than the first peak in April.

  • It is inescapable that the facts are changing

  • and we must change our response.

  • And so we have no choice

  • but to return to a national lockdown.

  • - [Narrator] While the new variants are concerning,

  • experts say that current prevention measures

  • should continue to work.

  • - This isn't something that's completing overcoming masks

  • or distancing and so if these measures

  • were put in place in more stricter,

  • more effective ways,

  • it'll be just as effective, if not more effective.

  • And the outcome may be that being a little bit more serious

  • about this will get transmission as a whole

  • to be reduced and I think that's an ideal.

  • - [Narrator] Scientists say the coronavirus pandemic

  • could be on the cusp of a major shift

  • but more research is needed

  • to know how severe the impact

  • of the new variants will be.

  • (dramatic music)

- [Narrator] New coronavirus variants

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The Coronavirus Is Mutating. Here’s What We Know | WSJ

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    joey joey に公開 2021 年 05 月 30 日
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