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  • On November 5th, 2020,

  • the United Kingdom went into lockdown.

  • They were trying to control a spike in Covid-19 cases.

  • And, if you look at the chart of cases,

  • it seemed to work.

  • But, despite having the same lockdown measures,

  • infections in Kent, an area outside of London, were still rising.

  • In early December, the overall drop in cases led the country to relax restrictions anyway.

  • And then this happened.

  • It wasn't until around this time that researchers realized

  • that somewhere in Kent, the virus itself had changed.

  • It was a new variant.

  • It was more contagious.

  • And it was spreading.

  • By the time scientists gave it a name, it had spread to most of southeast England.

  • Two months later, it was in 30 other countries.

  • Five months later, it was the most common form of the virus found in the United States.

  • Lately, more and more variants are emerging in various places around the world.

  • So why are they showing up now?

  • And what does this mean for the pandemic?

  • Viruses are very simple.

  • They're basically just a shell of protein surrounding some genetic material:

  • either DNA or RNA.

  • That genetic material is made up of molecules

  • that can be represented as a series of letters, like this.

  • Each part of this code contains instructions

  • for how to make one specific protein that allows the virus to function.

  • A virus has one goal: to make more of itself.

  • But because it's so simple, it can't do that on its own.

  • So it uses you.

  • Every time a virus infects a person, it uses their cells to make copies of itself--

  • replicating this complex code again, and again, and again.

  • But eventually, it makes a mistake.

  • Sometimes it deletes or adds a letter.

  • Sometimes it flips them around.

  • That mistake is called a mutation,

  • and it slightly changes the instructions for making the virus.

  • That slightly altered virus is a variant.

  • Since viruses are constantly going through this copying process,

  • it's normal for them to change over time.

  • For example, this chart shows some of the mutations

  • the SARS_CoV2 virus has made since December of 2019.

  • Most of the time, these mutations are harmless, or even make the virus weaker,

  • and they quietly disappear without making any notable difference.

  • But other times, a series of mutations occur that give the virus a slight edge over us.

  • Which is what scientists started to notice with SARS_CoV2, back in September of 2020.

  • You're seeing specific mutations that do allow the virus

  • to bind human receptors better, and enter cells better.”

  • Coronaviruses are covered in spike proteins,

  • that they use to bind with and infect human cells.

  • The thing is, that binding isn't a perfect fit.

  • So it doesn't always get past the cell's defenses.

  • But the B.1.1.7 variant, which scientists later renamed theAlphavariant,

  • has multiple mutations on the spike protein:

  • Mutations that make it easier for the virus to bind with cells.

  • Which can help make the virus more transmissible.

  • Which led it to become a dominant strain in many places around the world.

  • But if SARS_CoV2 has been mutating all along,

  • why do the variants today, like this Alpha variant,

  • suddenly seem so much worse?

  • It's important to remember that a virus doesn't make active decisions.

  • It's not as if it creates a strategy within your cells.

  • Mutations are random errors.

  • But the longer a virus is around, and the more people it infects,

  • the more it will change.

  • And the more those changes accumulate,

  • the more chances the virus has to evolve into something more dangerous.

  • These four variants, consideredvariants of concernby the World Health Organization,

  • all have mutations on the spike protein.

  • Delta, the most recent addition to this list, has been referred to as a “double mutant,”

  • because, while it has many different mutations, it has two significant ones we've seen before:

  • This mutation seems to make the virus more transmissible.

  • And a version of this one, found in two other variants,

  • makes it easier for the virus to reinfect people who have already had Covid-19--

  • meaning, these two mutations may have evolved to dodge our natural immune response.

  • Fortunately, the immune response we get from the vaccines

  • is much stronger than our body's natural immune response.

  • So, while we may see variants that make our vaccines somewhat less effective,

  • most experts think it's unlikely one will emerge that completely evades our vaccines.

  • But that doesn't mean it can't happen.

  • If you give the virus enough time and replicative cycles,

  • it will sample a very large evolutionary space,

  • and find a solution to the problem we've presented it--

  • which is vaccination and widespread immunity.”

  • But even if SARS_CoV2 doesn't get to that point,

  • as long as the pandemic continues, and as long as the virus continues to spread,

  • it will continue to make copies of itself.

  • So if we want to stop the variants,

  • we need to stop the virus.

  • The virus has evolved. But it hasn't morphed into something unrecognizable.

  • The vaccines we have still protect against all the variants.

  • The trouble is, we aren't getting those vaccines around the world fast enough.

  • Which is only giving the virus more time to change,

  • and ravage areas of the world that are still waiting.

  • The rise of variants is a reminder that the pandemic isn't over.

  • Even if it feels like it is to some of us.

  • We need to stop this, because we don't want a variant that affects immunity.

  • And so that involves stopping replication everywhere.”

On November 5th, 2020,

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冠狀病毒(Why so many Covid-19 variants are showing up now)

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    joey joey 發佈於 2021 年 06 月 17 日
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