Why is it so hard to cure the common cold?

翻译人员: Grace Man 校对人员: Yip Yan Yeung

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

2000 年，药物公司 维诺(ViroPharma)

针对药物普利康那利 (Pleconaril)开展了临床试验，

a new pill designed to treat the common cold.

这是一款用于治疗普通感冒的新药。

In many patients, the pill helped.

在很多患者身上，新药起到了效果。

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

然而，治疗才开始几天，研究人员 就在七名患者的体内发现了

researchers found mutated virus variants that were almost completely resistant

对新药几乎具有 完全抗药性的病毒的变异变体。

to pleconaril.

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

病毒时刻都在变异。 但是这次的病毒实在变异太快。

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

病毒几天的发展就轻松击败了 医学研究数年来的努力成果。

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

假如你没有免疫系统， 并且患上感冒，

the infection would quickly spread deep into your lungs.

病毒感染会 迅速蔓延至你的肺部深处，

Rampant viral replication would destroy tissue there,

疯狂的病毒复制会摧毁那里的组织，

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

直到你的肺部 不再能为身体提供足够的氧气，

and you’d asphyxiate.

你就会窒息。

Unfortunately, for millions of people around the world who live

不幸的是，地球上有数百万人

with a less-than-fully-functional immune system

免疫系统受损或者

or who are on immunosuppressant drugs,

需要依赖于免疫抑制药物。

this is a real risk:

对他们来说，风险很大——

“minor” infections can turn serious or even deadly.

“轻微”感染就可能导致重症甚至丧命。

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

但是如果你足够幸运地拥有 功能健全的免疫系统，

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

感冒可能只会给你带来 相对来说非常轻微的症状。

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

成年人平均一生会 患上超过 150 次的感冒。

And despite the fact that the symptoms are similar,

尽管症状相似，

the cause could be different each time.

但每次感冒的原因不尽相同。

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

至少有来自八类不同家族的病毒 均可造成普通感冒，

each of which can have its own species and subtypes.

每一类又具有自己的 病毒种类与亚型。

How can so many different viruses cause the same illness?

如此多不同的病毒 怎么会导致相同的疾病呢？

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

病毒仅能通过 以下几种方式入侵人体：

one is to come in on a breath.

首先是通过呼吸。

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

人都得呼吸，所以我们的免疫系统 设立了很多防御前线，

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

这些其实是 很多感冒症状的产生原因。

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

你的免疫系统困住病毒， 并把它们清扫出身体，

就形成了你淌出的黏黏的鼻涕。

Your fever is your immune system raising your body temperature

发烧则是因为免疫系统 通过升高体温的方式

to slow down viral replication.

减缓病毒复制进程。

And your inflamed, well, everything,

当身体出现炎症，

that’s your immune system widening your blood vessels

那是因为免疫系统扩张了你的血管，

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

并且召唤白细胞军团来杀死细菌。

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

如此多不同的病毒均可以 导致普通感冒，

is a cure even possible?

那么，治愈普通感冒 到底是否有可能呢？

Here’s one fact in our favor:

一件我们喜闻乐见的事：

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

30% 至 50% 的所有感冒 都来源于同一种病毒家族——

rhinovirus.

鼻病毒(rhinovirus)。

If we could eliminate all rhinovirus infections,

倘若我们可以 消灭所有的鼻病毒感染，

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

那将是我们在治愈普通感冒的路上 取得的巨大进步。

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

有两种对抗病毒的主要方法： 疫苗和抗病毒药物。

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

创造鼻病毒疫苗的首次尝试 是成功的——

but a short-lived one.

尽管这成功非常短暂。

In 1957, William Price vaccinated 50 kids with inactivated rhinovirus

1957 年，威廉·布莱斯 (William Price)

为 50 个孩子注射了 灭活的鼻病毒疫苗，

and gave 50 others a placebo.

为另一对照组的 50 名小孩 注射了安慰剂。

Soon afterwards, a rhinovirus outbreak spread throughout the kids.

不久后，鼻病毒爆发， 并在孩子当中传播。

In the vaccinated group, only 3 got sick.

注射过疫苗的孩子当中， 只有 3 人生病了。

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

对照组里，23 人生病了—— 几乎是疫苗组的 8 倍。

And despite the small numbers, this was promising:

尽管试验人数不多， 但结果令人振奋：

the immune systems of vaccinated kids were successfully

接受疫苗注射的孩子们的免疫系统

recognizing and responding to rhinovirus.

成功识别并对鼻病毒做出了应对抵抗。

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

但是该疫苗的后续试验显示 它并没有保护作用——完全没有。

This wasn’t Price’s fault—

这并不是布莱斯的错——

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

当时没人知道鼻病毒有多种亚型。

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

由于一些我们不能完全理解的原因，

didn't provide broad protection,

布莱斯的疫苗 不能提供更广泛的保护作用。

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

他的疫苗仅对一种或是几种 鼻病毒亚型有效——

out of 169 subtypes and counting.

亚型共有 169 种， 并且数量还在不断增加。

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

有时，我们研发出一种疫苗，

The mRNA COVID vaccines, for example,

比如，新冠肺炎 mRNA 疫苗，

effectively protect us against severe disease and death

它对于原始病毒以及 病毒变种都有效果，

across the original virus and variants too.

有效保护我们免于重症与死亡， 出现这种情况，我们就很幸运。

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

但是我们还没有发明出疫苗 用以广泛对抗鼻病毒

or any other virus that causes the common cold.

以及其他会引发普通感冒的病毒。

Okay, what about antiviral drugs?

那么，抗病毒药物呢？

Viruses hijack human cellular machinery to replicate and spread,

病毒劫持了人体的细胞运作机制 用以自身的复制与传播，

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

因此，想要让一个药物分子 只对病毒有害，

without also being toxic to the human.

却对人体无害，这是非常困难的。

And even if you manage to do that,

即使你成功做到了，

the virus could mutate out of reach of the drug.

病毒也可以通过变异来使药物失效。

Viruses are slippery beasts.

病毒是如此狡猾的怪兽。

We have, though, had some incredible successes:

其实我们已经在一些方面 取得了惊人的成果：

we eradicated smallpox thanks to an effective vaccine,

我们根除了天花， 这得益于有效的疫苗，

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

天花病毒不能藏匿于其他物种，

and its relatively low mutation rate.

以及病毒相对缓慢的变异速度。

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

可是，另外一些方面，比如艾滋病， 它实在是变异得太快了。

理论上，在一个未被治疗的人体中， 病毒基因序列当中

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

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

所有可能的单碱基突变， 都能在一天之内产生。

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

即使已经努力了几十年， 我们仍然没有发明出艾滋病疫苗，

But we do have an effective cocktail of HIV drugs

不过我们有了 一种有效的鸡尾酒药物疗法，

that the virus can’t easily mutate away from.

变异的病毒不会轻易地 对该药物产生抗药性。

Unfortunately, we are stuck with colds for now.

不幸的是， 我们目前还在与感冒纠缠，

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

但是过去的几十年，我们已经取得了 一些颠覆性的医疗突破，

medical breakthroughs, like mRNA vaccines and CRISPR.

比如 mRNA 疫苗与 CRISPR （规律间隔成簇短回文重复序列）。

CRISPR could be particularly promising as an antiviral agent,

CRISPR 作为一种抗病毒剂 极具前景，

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

因为它是由最初抵抗过 病毒攻击的细菌发展而来。

In fact, early in the COVID-19 pandemic,

事实上，在新冠早期，

a research team showed that a CRISPR system could degrade

曾有团队研究发现 一种 CRISPR 系统

coronavirus and influenza genomes in our lung cells.

可以降解肺部细胞中的 冠状病毒和流感病毒的基因组。

They called their system prophylactic antiviral CRISPR in human cells.

他们将该系统命名为 “人类细胞中的预防性抗病毒 CRISPR ”。

Or, for short, PAC-MAN.

其简称为 “PAC-MAN”（“吃豆人”）。