What is a coronavirus? - Elizabeth Cox

1,915,927 views ・ 2020-05-14

TED-Ed


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翻译人员: Ethan Huang 校对人员: Yolanda Zhang
00:07
For almost a decade, scientists chased the source of a deadly new virus
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在近十年间,从中国的 最高峰到最偏远的洞穴里,
00:12
through China’s tallest mountains and most isolated caverns.
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科学家们一直在追寻一种 新型致命病毒的源头。
00:16
They finally found it here: in the bats of Shitou Cave.
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他们最终在“石头洞”的蝙蝠 身上找到了答案。
00:21
The virus in question was a coronavirus
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人们所找寻的病毒是 一种在 2003 年引发了
00:23
that caused an epidemic of severe acute respiratory syndrome,
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严重急性呼吸系统 综合症流行病,
00:27
or SARS, in 2003.
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简称非典型肺炎(SARS)的冠状病毒。
00:30
Coronaviruses are a group of viruses
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冠状病毒是一群表面有着 棘突蛋白的病毒,
00:32
covered in little protein spikes that look like a crown—
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看起来很像皇冠——
00:36
or "corona" in Latin.
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在拉丁文中意为“冠状物”。
00:38
There are hundreds of known coronaviruses.
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目前已知的冠状病毒有数百种。
00:41
Seven of them infect humans, and can cause disease.
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其中的七种可以传染给人类 并且引起疾病。
00:45
The coronavirus SARS-CoV causes SARS, MERS-CoV causes MERS,
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冠状病毒 SARS-CoV 可引起非典型肺炎, MERS-CoV 可引起中东呼吸系统综合征,
00:51
and SARS-CoV-2 causes the disease COVID-19.
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而 SARS-CoV-2 则可引起 新型冠状病毒肺炎(COVID-19)。
00:56
Of the seven human coronaviruses, four cause colds,
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七种会感染人类的冠状病毒中, 有四种会导致感冒,
01:01
mild, highly contagious infections of the nose and throat.
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即症状温和 且具有高传染性的鼻喉感染。
01:05
Two infect the lungs, and cause much more severe illnesses.
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有两种会感染肺部并且 引起更严重的疾病。
01:10
The seventh, which causes COVID-19, has features of each:
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引起 COVID-19 的第七种病毒 综合了上述两类的特征:
01:14
it spreads easily, but can severely impact the lungs.
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不仅极易传播, 而且会严重地影响肺部。
01:18
When an infected person coughs, droplets containing the virus spray out.
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当受感染者咳嗽时,含有病毒 的飞沫就会喷溅而出。
01:23
The virus can infect a new person when the droplets enter their nose or mouth.
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当飞沫进入其他人的鼻腔或口腔时, 这些人就会被病毒感染。
01:28
Coronaviruses transmit best in enclosed spaces,
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冠状病毒在封闭的 空间内最易传播,
01:31
where people are close together.
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在这些地方人与人之间距离很近。
01:33
Cold weather keeps their delicate casing from drying out,
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寒冷的天气可以防止病毒的 精密外壳变干,
01:36
enabling the virus to survive for longer between hosts,
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使得它们在宿主之间 传播时能够存活更长时间。
01:40
while UV exposure from sunlight may damage it.
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但是紫外线的照射 可能会消灭它们。
01:43
These seasonal variations matter more for established viruses.
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这些季节上的变化对于 已经存在的病毒影响更大。
01:47
But because no one is yet immune to a new virus,
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但是因为至今没有任何人 对新出现的病毒免疫,
01:50
it has so many potential hosts that it doesn’t need ideal conditions to spread.
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所以它有很多不需要在理想环境下 就可以感染的潜在宿主。
01:55
In the body, the protein spikes embed in the host’s cells and fuse with them—
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进入人体后,棘突蛋白会嵌入 宿主的细胞内并与它们融合——
02:00
enabling the virus to hijack the host cell’s machinery
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这个过程让病毒能够控制 宿主细胞的运转体系,
02:02
to replicate its own genes.
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以复制其自身的遗传基因。
02:05
Coronaviruses store their genes on RNA.
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冠状病毒把它们的基因 储存在 RNA 内。
02:08
All viruses are either RNA viruses or DNA viruses.
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所有病毒都是 RNA 或者 DNA 病毒。
02:12
RNA viruses tend to be smaller, with fewer genes,
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RNA 病毒通常更小, 携带更少的基因,
02:15
meaning they infect many hosts and replicate quickly in those hosts.
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这意味着它们可以感染众多宿主, 并且在宿主体内快速复制。
02:20
In general, RNA viruses don’t have a proofreading mechanism,
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一般来说,RNA 病毒没有校对机制,
02:24
whereas DNA viruses do.
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而 DNA 病毒则有。
02:27
So when an RNA virus replicates,
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因此,当 RNA 病毒进行自我复制时,
02:29
it’s much more likely to have mistakes called mutations.
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更有可能发生错误,即所谓的“突变”。
02:33
Many of these mutations are useless or even harmful.
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大多数的突变都是对其自身 无用,甚至是无益的。
02:37
But some make the virus better suited for certain environments—
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但是有一些变异可以帮助病毒 更加适应某些特定的环境——
02:40
like a new host species.
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比如说新的宿主物种。
02:42
Epidemics often occur when a virus jumps from animals to humans.
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传染病通常在病毒从动物 传染到人类时出现,
02:47
This is true of the RNA viruses that caused
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比如由 RNA 病毒导致的
02:49
the Ebola, Zika, and SARS epidemics, and the COVID-19 pandemic.
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埃博拉、寨卡和非典传染病,以及 COVID-19 全球性大流行病。
02:55
Once in humans, the virus still mutates—
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进入人体以后, 病毒仍然会发生突变——
02:58
usually not enough to create a new virus,
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虽然这种突变不足以 创造新型的病毒,
03:00
but enough to create variations, or strains, of the original one.
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但足以使原本的病毒 产生变化,或产生新株系。
03:05
Coronaviruses have a few key differences from most RNA viruses.
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相比大多数 RNA 病毒, 冠状病毒有几个主要的差别。
03:09
They’re some of the largest, meaning they have the most genes.
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它们是体积最大的 RNA 病毒, 有着最多的遗传基因,
03:13
That creates more opportunity for harmful mutations.
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也就更可能出现 对自身有害的变异。
03:16
To counteract this risk, coronaviruses have a unique feature:
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为了抵消这种风险,冠状病毒 展现出了一种独有的特性:
03:21
an enzyme that checks for replication errors and corrects mistakes.
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一种可以检验基因复制错误 并进行纠正的酶。
03:25
This makes coronaviruses much more stable,
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这一特征使得冠状病毒 比其他 RNA 病毒的
03:27
with a slower mutation rate, than other RNA viruses.
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突变速度更加缓慢, 因此更加稳定。
03:31
While this may sound formidable,
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虽然这可能听上去很可怕,
03:33
the slow mutation rate is actually a promising sign
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但是当涉及到削弱其致病性,
03:36
when it comes to disarming them.
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其缓慢的突变速率 实际上是一个很好的现象。
03:38
After an infection, our immune systems can recognize germs
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在被感染以后,我们的 免疫系统可以识别病菌,
03:42
and destroy them more quickly if they infect us again
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并且在它们再次感染我们时 快速地摧毁它们,
03:45
so they don’t make us sick.
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从而起到免疫效果。
03:47
But mutations can make a virus less recognizable to our immune systems—
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但是突变会让病毒变得更不易 被我们的免疫系统察觉——
03:51
and therefore more difficult to fight off.
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因此也就更难去击溃它们。
03:53
They can also make antiviral drugs and vaccines less effective,
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它们也会使抗病毒药品 和疫苗的效果大打折扣,
03:57
because they’re tailored very specifically to a virus.
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因为这些药物都是 为每种病毒而特别定制的。
04:01
That’s why we need a new flu vaccine every year—
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这就是为什么我们每年都 需要研发新的流感疫苗——
04:04
the influenza virus mutates so quickly that new strains pop up constantly.
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因为流感病毒的突变发生得太快, 新株系会持续地出现。
04:09
The slower mutation rate of coronaviruses means
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冠状病毒更慢的突变速率意味着
04:11
our immune systems, drugs, and vaccines
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人体的免疫系统、药品以及疫苗
04:14
might be able to recognize them for longer after infection,
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也许在感染之后的 更长时间内依然可以辨别它们,
04:18
and therefore protect us better.
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从而更好地保护我们的健康。
04:21
Still, we don’t know how long our bodies remain immune to different coronaviruses.
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目前,我们还不知道被冠状病毒感染后, 人体的免疫时间能持续多久。
04:25
There’s never been an approved treatment or vaccine for a coronavirus.
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对于冠状病毒,我们也尚未研发出 被证实有效的治疗方法或者疫苗。
04:29
We haven’t focused on treating the ones that cause colds,
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我们还从未专注于应对 引起感冒的冠状病毒,
04:32
and though scientists began developing treatments for SARS and MERS,
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虽然科学家们已经开始钻研 非典和中东呼吸综合征的治疗方法,
04:36
the epidemics ended before those treatments completed clinical trials.
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但是疫情都在治疗方案 尚未完成临床实验时就结束了。
04:40
As we continue to encroach on other animals’ habitats,
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随着我们继续不断侵占 其它动物的栖息地,
04:43
some scientists say a new coronavirus jumping to humans is inevitable—
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科学家们宣称,新型冠状病毒 从动物传染给人类是无法避免的——
04:48
but if we investigate these unknowns, it doesn’t have to be devastating.
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但如果我们调查清楚这些未知事物, 就可以避免大规模的破坏性后果。
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