Why is it so hard to cure the common cold?

譯者: Winston Chung 審譯者: Zoe Walmsley

In 2000, a company called ViroPharma ran clinical trials of pleconaril,

2000 年，ViroPharma 藥廠做了一個臨床實驗，

a new pill designed to treat the common cold.

Pleconaril， 一個專治感冒的新藥，

In many patients, the pill helped.

在許多病人身上見效，

But in 7 of them, just a few days into the treatment,

但是實驗開始幾天後，

researchers found mutated virus variants that were almost completely resistant

研究人員在其中七人身上 發現病毒變異株，

而且幾乎對 pleconaril 有完全抗藥性。

to pleconaril.

Viruses are always mutating, but this one mutated so quickly that it managed

病毒隨時都在突變， 但是這病毒的突變速度之快，

to outmaneuver years of research and development in just a few days.

快到只花幾天時間 就超越多年的研究發展。

If you didn't have an immune system and caught a cold,

如果你在沒有免疫力時得到感冒，

the infection would quickly spread deep into your lungs.

發炎會迅速擴散到肺部。

Rampant viral replication would destroy tissue there,

病毒大量複製，破壞組織細胞，

until your lungs couldn’t supply your body with enough oxygen

直到你的肺無法供應 足夠的氧氣給身體，

and you’d asphyxiate.

然後窒息而死。

Unfortunately, for millions of people around the world who live

不幸的是，全世界有幾百萬人

with a less-than-fully-functional immune system

有免疫系統不全的問題，

or who are on immunosuppressant drugs,

或是服用的藥會壓抑免疫系統，

this is a real risk:

他們面臨著一個風險：

“minor” infections can turn serious or even deadly.

「輕微」的感染可能 轉成重症，甚至致命。

But if you're fortunate enough to have a fully functional immune system,

但是，如果你運氣好，免疫系統健全，

a cold will probably give you a few relatively mild symptoms.

感冒可能就只有少數輕微症狀。

On average, adults catch more than 150 colds throughout their lives.

平均而言，成人一生 感冒的次數超過 150 次。

And despite the fact that the symptoms are similar,

雖然症狀都很類似，

the cause could be different each time.

造成感冒的原因卻可能次次不同。

Common colds are caused by at least 8 different families of virus,

一般的感冒是由至少八種 不同的病毒群組所引起，

each of which can have its own species and subtypes.

每個群組又有各自的品種和亞型。

How can so many different viruses cause the same illness?

這麼多種不同的病毒 為什麼能造成相同的疾病？

Well, viruses can only invade our bodies in a few ways:

因為病毒入侵人體的途徑就是那幾個：

one is to come in on a breath.

透過呼吸道進入是其中之一。

We have to breathe, so our immune system sets up a bunch of frontline defenses

我們必須呼吸，因此免疫系統 設了一堆前線抵禦措施，

and these are actually what produce many of the symptoms of a cold.

而它們才是造成許多感冒症狀的原因。

Your mucus-y, dripping nose is your immune system trapping and flushing out virus.

流鼻涕其實是免疫系統 將病毒攔截、排出體外。

Your fever is your immune system raising your body temperature

發燒是因為免疫系統藉由 升高體溫，減緩病毒複製。

to slow down viral replication.

And your inflamed, well, everything,

而任何的發炎反應則是因為……

that’s your immune system widening your blood vessels

免疫系統將血管擴張

and recruiting its white blood cell army to help kill the virus.

以便集結白血球大軍來幫助圍剿病毒。

So, if the common cold is caused by many different viruses,

那麼，如果感冒可由 多種不同的病毒引起，

is a cure even possible?

那有可能找到治療方法嗎？

還好有個對我們有利的因素：

Here’s one fact in our favor:

a single family of viruses causes 30 to 50% of all colds:

有 30%-50% 的感冒 是由同一個病毒群組造成的：

rhinovirus.

Rhinovirus ── 鼻病毒。

If we could eliminate all rhinovirus infections,

只要能排除所有鼻病毒的感染，

we’d be a long way towards curing the common cold.

就離治癒一般感冒很近了。

There are two main ways to fight a virus: vaccines and antiviral drugs.

主要對付病毒的方法有兩個： 疫苗和抗病毒藥劑。

The first attempt to create a rhinovirus vaccine was a success—

首次嘗試開發鼻病毒疫苗成功了，

but a short-lived one.

但是很短暫。

In 1957, William Price vaccinated 50 kids with inactivated rhinovirus

1957 年，威廉‧布萊斯為 50 名孩童接種非活化的鼻病毒，

and gave 50 others a placebo.

給另外 50 個孩子打安慰劑。

Soon afterwards, a rhinovirus outbreak spread throughout the kids.

沒多久，爆發鼻病毒疫情， 傳染到這群兒童身上。

In the vaccinated group, only 3 got sick.

接種疫苗的那群只有三個生病，

In the placebo group, 23 did— almost 8 times as many.

安慰劑那組則有 23 人染病， 幾乎是前者的八倍。

And despite the small numbers, this was promising:

雖然實驗的樣本數很小， 結果卻很被看好：

the immune systems of vaccinated kids were successfully

注射疫苗的兒童的免疫系統 成功地辨識、對抗鼻病毒。

recognizing and responding to rhinovirus.

But later trials of the vaccine showed no protection at all— none.

但後期的實驗結果卻沒看到 任何保護力， 一點都沒有。

This wasn’t Price’s fault—

那不是布萊斯的錯──

no one at the time knew that rhinovirus had multiple subtypes.

當時沒人知道鼻病毒有多種亞型。

Price’s vaccine, for reasons we don’t fully understand,

布萊斯的疫苗，因為一些不明的原因，

didn't provide broad protection,

沒有全面的保護力，

meaning it was only effective against one or maybe a few subtypes of rhinovirus—

也就是說它只對一種 或少數幾種鼻病毒亞型有效 ──

out of 169 subtypes and counting.

而它的亞型多達 169 種， 且還在持續增加。

Sometimes, when we make a vaccine, we get lucky.

有時候，開發疫苗還是得看運氣。

The mRNA COVID vaccines, for example,

舉例來說，COVID 的 mRNA 疫苗，

effectively protect us against severe disease and death

能有效預防重症及死亡，

across the original virus and variants too.

無論是病毒原型還是變種病毒。

But we have yet to create a broadly protective vaccine against rhinovirus,

但是我們尚未開發出一個 效力廣泛的鼻病毒疫苗，

or any other virus that causes the common cold.

或對其他感冒病毒的有效疫苗。

Okay, what about antiviral drugs?

那麼，抗病毒藥劑呢？

Viruses hijack human cellular machinery to replicate and spread,

病毒劫持人體細胞的功能， 幫它複製、擴散，

so it’s hard to make a molecule that’s toxic to the virus

所以很難做出一個分子能專攻病毒，

without also being toxic to the human.

卻不對人體有害。

And even if you manage to do that,

即使真的做出來了，

the virus could mutate out of reach of the drug.

病毒也能透過突變，讓藥劑失效。

Viruses are slippery beasts.

病毒是很油滑的東西。

We have, though, had some incredible successes:

過去，我們也曾有些了不起的成就：

we eradicated smallpox thanks to an effective vaccine,

我們滅絕了天花， 歸功於：一個有效的疫苗、

the fact that it can’t hide out in other species,

天花不能潛藏在其他物種的特性、

and its relatively low mutation rate.

它的突變速度也相對緩慢。

HIV, on the other hand, mutates so quickly that in an untreated individual,

相形之下，HIV 病毒 突變的速度之快──

在沒接受治療的病患身上──

every possible single-letter mutation in the virus’s genetic code

能快到一天內用掉 所有單一字母的基因編碼。

could, in theory, be produced in a single day.

Despite trying for decades, we still don’t have a vaccine.

經過幾十年的努力，目前尚未有疫苗，

But we do have an effective cocktail of HIV drugs

不過，還是有一個有效的 HIV 雞尾酒療法，

that the virus can’t easily mutate away from.

讓病毒不容易靠突變逃脫。

Unfortunately, we are stuck with colds for now.

不幸地，我們目前還甩不掉感冒。

But the last few decades have featured some entirely game-changing

不過，過去數十年來 有些醫學上的顛覆性突破，

medical breakthroughs, like mRNA vaccines and CRISPR.

像是 mRNA 疫苗 及 CRISPR（基因編輯技術）。

CRISPR could be particularly promising as an antiviral agent,

CRISPR 最被看好的是 它能作為抗病毒媒介，

because it originally evolved in bacteria as an immune defense against viruses.

因為它本來就是細菌演化出來 對抗病毒的免疫機制。

In fact, early in the COVID-19 pandemic,

事實上，在 COVID-19 的疫情初期，

a research team showed that a CRISPR system could degrade

有個研究團隊發表了 一個 CRISPR 系統，

coronavirus and influenza genomes in our lung cells.

能讓肺部細胞中的 新冠及流感病毒的基因組降解。

They called their system prophylactic antiviral CRISPR in human cells.

他們把這系統命名為「人體細胞 預防性抗病毒 CRISPR」，

Or, for short, PAC-MAN.

也用縮寫暱稱為 PAC-MAN （吃豆人電子遊戲）。