What is a coronavirus? - Elizabeth Cox

1,887,973 views ・ 2020-05-14

TED-Ed


Please double-click on the English subtitles below to play the video.

Translator: 潘 可儿 Reviewer: Chak Lam Wan
00:07
For almost a decade, scientists chased the source of a deadly new virus
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將近十年嚟,科學家一直喺中國
最高嘅山同最偏僻嘅山窿
00:12
through China’s tallest mountains and most isolated caverns.
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尋找著一種致命嘅新型病毒
00:16
They finally found it here: in the bats of Shitou Cave.
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佢哋最終喺雲南洞穴嘅蝙蝠身上搵到
00:21
The virus in question was a coronavirus
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呢種未知嘅病毒係一種冠狀病毒
00:23
that caused an epidemic of severe acute respiratory syndrome,
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佢引發咗 2003 年 嚴重急性呼吸綜合征
00:27
or SARS, in 2003.
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即係沙士
00:30
Coronaviruses are a group of viruses
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冠狀病毒係一類
00:32
covered in little protein spikes that look like a crown—
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由細小蛋白刺突包裹嘅病毒 佢睇起身好似一個皇冠
00:36
or "corona" in Latin.
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用拉丁語講就係 corona
00:38
There are hundreds of known coronaviruses.
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已知嘅冠狀病毒有幾百種
00:41
Seven of them infect humans, and can cause disease.
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其中有七種會感染人類、令人病
00:45
The coronavirus SARS-CoV causes SARS, MERS-CoV causes MERS,
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譬如話,沙士冠狀病毒會引發沙士
中東呼吸綜合症冠狀病毒 會引發中東呼吸綜合症
00:51
and SARS-CoV-2 causes the disease COVID-19.
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新冠病毒就會引發新冠肺炎
00:56
Of the seven human coronaviruses, four cause colds,
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喺七種人類冠狀病毒之中 四種會引致感冒
01:01
mild, highly contagious infections of the nose and throat.
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鼻、喉嚨會受到輕度而高傳染性嘅感染
01:05
Two infect the lungs, and cause much more severe illnesses.
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兩種會感染肺部 並引發更嚴重嘅疾病
01:10
The seventh, which causes COVID-19, has features of each:
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而第七種,即新冠病毒 有頭六種嘅特徵
01:14
it spreads easily, but can severely impact the lungs.
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佢好容易傳播 嚴重影響肺部功能
01:18
When an infected person coughs, droplets containing the virus spray out.
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一個病毒感染者一旦咳嗽 含有病毒嘅飛沫就開始散播
01:23
The virus can infect a new person when the droplets enter their nose or mouth.
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當飛沫入咗鼻或者嘴 病毒就傳染畀另一個人
01:28
Coronaviruses transmit best in enclosed spaces,
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當好多人都喺同一個密閉空間嗰時
01:31
where people are close together.
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冠狀病毒就係傳播得最犀利
01:33
Cold weather keeps their delicate casing from drying out,
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而天氣寒冷,令冠狀病毒 脆弱嘅外殼免於脫水
01:36
enabling the virus to survive for longer between hosts,
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令佢哋喺宿主之間生存得更耐
01:40
while UV exposure from sunlight may damage it.
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陽光中嘅紫外線 或者可以破壞脆弱嘅外殼
01:43
These seasonal variations matter more for established viruses.
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雖然季節變化對已知病毒嘅影響大
01:47
But because no one is yet immune to a new virus,
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但由於冇人對呢種新病毒有免疫
01:50
it has so many potential hosts that it doesn’t need ideal conditions to spread.
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所以佢唔需要理想條件 就可以感染好多潛在宿主
01:55
In the body, the protein spikes embed in the host’s cells and fuse with them—
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喺人體之中,蛋白刺突嵌入 宿主細胞,並同佢結合
02:00
enabling the virus to hijack the host cell’s machinery
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因此,病毒可以綁架 成個宿主細胞機制
02:02
to replicate its own genes.
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要挾宿主細胞複製病毒嘅基因
02:05
Coronaviruses store their genes on RNA.
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冠狀病毒將佢哋嘅基因儲存喺 RNA
02:08
All viruses are either RNA viruses or DNA viruses.
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所有病毒都可以分為 RNA 病毒 或者 DNA 病毒
02:12
RNA viruses tend to be smaller, with fewer genes,
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RNA 病毒一般都比較細 攜帶較少嘅基因
02:15
meaning they infect many hosts and replicate quickly in those hosts.
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即佢哋可以感染好多宿主 仲可以喺宿主體內快速複製
02:20
In general, RNA viruses don’t have a proofreading mechanism,
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一般嚟講,RNA 病毒 都係冇校對機制嘅
02:24
whereas DNA viruses do.
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而 DNA 病毒就有
02:27
So when an RNA virus replicates,
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所以當一個 RNA 病毒複製緊
02:29
it’s much more likely to have mistakes called mutations.
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基因變異就更頻繁噉發生
02:33
Many of these mutations are useless or even harmful.
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呢啲變異好多都係冇用 甚至係有害
02:37
But some make the virus better suited for certain environments—
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但有啲變異可以令病毒 更加適應到某啲環境
02:40
like a new host species.
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譬如係一種新嘅宿主物種
02:42
Epidemics often occur when a virus jumps from animals to humans.
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當一種病毒從動物傳播到人類身上 流行病就會發生啦
02:47
This is true of the RNA viruses that caused
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引發伊波拉、寨卡、沙士 同埋新冠肺炎嘅 RNA 病毒都係噉
02:49
the Ebola, Zika, and SARS epidemics, and the COVID-19 pandemic.
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02:55
Once in humans, the virus still mutates—
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噉進入人體之後,病毒依然會變異
02:58
usually not enough to create a new virus,
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雖然唔會通常演變到成為一種新嘅病毒
03:00
but enough to create variations, or strains, of the original one.
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但都做到啲基因變異出嚟
03:05
Coronaviruses have a few key differences from most RNA viruses.
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冠狀病毒同大部分 RNA 病毒 有幾個關鍵嘅區別
03:09
They’re some of the largest, meaning they have the most genes.
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佢哋比較大隻 即係有最多基因
03:13
That creates more opportunity for harmful mutations.
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噉就更易令有害變異發生
03:16
To counteract this risk, coronaviruses have a unique feature:
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為咗降低呢種風險 冠狀病毒有一種獨特嘅特點
03:21
an enzyme that checks for replication errors and corrects mistakes.
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佢含有一種酵素,專門 負責檢查、糾正複製錯誤
03:25
This makes coronaviruses much more stable,
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咁就令到冠狀病毒更加穩定
03:27
with a slower mutation rate, than other RNA viruses.
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令到佢比其他 RNA 病毒變異得更慢
03:31
While this may sound formidable,
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雖然聽起嚟好恐怖
03:33
the slow mutation rate is actually a promising sign
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但係講到要瓦解冠狀病毒
03:36
when it comes to disarming them.
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變異得慢係好事嚟
03:38
After an infection, our immune systems can recognize germs
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因為當我哋感染病菌之後 我哋嘅免疫系統可以識別病菌
03:42
and destroy them more quickly if they infect us again
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而當我哋再次感染病菌時 就可以更快消滅病菌
03:45
so they don’t make us sick.
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噉佢哋就唔會再搞到我哋病
03:47
But mutations can make a virus less recognizable to our immune systems—
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但係病毒變異可以令我哋嘅免疫系統 冇咁容易識別到病毒
03:51
and therefore more difficult to fight off.
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噉擊退病毒就會難啲
03:53
They can also make antiviral drugs and vaccines less effective,
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而病毒變異會令抗病毒藥物 同疫苗,變得冇咁有效
03:57
because they’re tailored very specifically to a virus.
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因為藥物同疫苗 係專門針對某種病毒嘅
04:01
That’s why we need a new flu vaccine every year—
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噉就係點解我哋每年 都要重新打一次流感疫苗
04:04
the influenza virus mutates so quickly that new strains pop up constantly.
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因為流感病毒變異得好快 新嘅病毒不斷出現
04:09
The slower mutation rate of coronaviruses means
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冠狀病毒較慢嘅變異速率
04:11
our immune systems, drugs, and vaccines
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意味著我哋嘅免疫系統 同埋藥物、疫苗
04:14
might be able to recognize them for longer after infection,
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喺感染之後嘅一段長時間 都仲可以識別到呢啲病毒
04:18
and therefore protect us better.
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噉就可以更好咁保障我哋
04:21
Still, we don’t know how long our bodies remain immune to different coronaviruses.
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目前,我哋依然都未知我哋嘅身體 可以對唔同嘅冠狀病毒免疫幾耐
04:25
There’s never been an approved treatment or vaccine for a coronavirus.
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面對任何冠狀病毒,永遠都 唔會有一種肯定嘅療法或疫苗
04:29
We haven’t focused on treating the ones that cause colds,
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雖然科學家開始研發 針對 SARS 同 MERS 嘅治療
04:32
and though scientists began developing treatments for SARS and MERS,
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但我哋都仲未重點研究感冒治療
04:36
the epidemics ended before those treatments completed clinical trials.
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喺療法嘅臨床實驗完成之前 疫情就已經結束啦
04:40
As we continue to encroach on other animals’ habitats,
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有科學家話,鑒於我哋一直喺度 入侵其他動物嘅棲息地
04:43
some scientists say a new coronavirus jumping to humans is inevitable—
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新嘅冠狀病毒 係無可避免會傳播到人身上
04:48
but if we investigate these unknowns, it doesn’t have to be devastating.
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但如果我哋要探索未知 都唔一定次次要咁大劑嘅
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