The surprising reason you feel awful when you're sick - Marco A. Sotomayor

翻译人员: Jenny Hsu 校对人员: Tricia Tay

It starts with a tickle in your throat that becomes a cough.

开始时你的喉咙有一点痒，接着你开始咳嗽，

Your muscles begin to ache,

肌肉变得疼痛，

you grow irritable,

情绪莫名的急躁，

and you lose your appetite.

变得没有胃口，

It's official: you've got the flu.

这些症状表明你得流感了。

It's logical to assume that this miserable medley of symptoms

我们理所当然的认为造成这一系列症状

is the result of the infection coursing through your body,

的原因是身体受到了感染

but is that really the case?

但事实真的是这样吗？

What's actually making you feel sick?

到底是什么让我们感到身体不适？

What if your body itself was driving this vicious onslaught?

如果是我们的身体在攻击它自己呢？

You first get ill when a pathogen like the flu virus gets into your system,

当流感病毒这样的病原体进入体内感染并杀死细胞时

infecting and killing your cells.

你才会感到生病

But this unwelcome intrusion has another effect:

但这种并不受欢迎的侵入却有另一种作用

it alerts your body's immune system to your plight.

它会使你身体的免疫系统注意于当下的状况

As soon as it becomes aware of infection, your body leaps to your defense.

只要发生感染，免疫系统便立刻作出反应

Cells called macrophages charge in as the first line of attack,

巨噬细胞作为第一线的攻击者

searching for and destroying the viruses and infected cells.

将会搜索并消灭病毒与受感染的细胞

Afterwards, the macrophages release protein molecules called cytokines

然后巨噬细胞会释放一种叫作细胞因子的蛋白质分子

whose job is to recruit

它会从免疫系统中征集并组织更多的

and organize more virus-busting cells from your immune system.

细胞来杀死病毒

If this coordinated effort is strong enough,

如果这一阶段的协调作用足够强的话

it'll wipe out the infection before you even notice it.

它会在你丝毫不知情的状态下清除感染

But that's just your body setting the scene for some real action.

但这只是你身体为一些实际行动所作出的准备

In some cases, viruses spread further,

在某些情况下，病毒进一步蔓延

even into the blood and vital organs.

甚至进入血液和重要器官

To avoid this sometimes dangerous fate,

为了避免这种可能发生的危险

your immune system must launch a stronger attack,

你的免疫系统必须发起更强的进攻

coordinating its activity with the brain.

协调与大脑的活动

That's where those unpleasant symptoms come in,

这就是那些引起不适的症状来源。

starting with the surging temperature,

体温开始升高,

aches and pains,

身体疼痛,

and sleepiness.

和昏昏欲睡。

So why do we experience this?

所以我们为何会经历这些？

When the immune system is under serious attack,

当免疫系统受到严重攻击时，

it secretes more cytokines,

它分泌更多细胞因子

which trigger two responses.

来触发两种反应:

First, the vagus nerve, which runs through the body into the brain,

首先，贯穿整个身体的脑神经，迷走神经

quickly transmits the information to the brain stem,

快速将信息传递到脑干

passing near an important area of pain processing.

路经一个控制疼痛过程的重要区域

Second, cytokines travel through the body to the hypothalamus,

其次，细胞因子穿过身体到达下丘脑

the part of the brain responsible for controlling temperature,

它是大脑中控制温度调节，

thirst,

口渴，

hunger,

饥饿，

and sleep,

在其他事情中还有

among other things.

睡意。

When it receives this message,

当下丘脑接受到这种信息

the hypothalamus produces another molecule

它会产生另一种分子

called prostaglandin E2, which gears it up for war.

叫做前列腺素E2，在战争中发挥了重要的作用

The hypothalamus sends signals that instruct your muscles to contract

下丘脑发出信号来控制你的肌肉收缩

and causes a rise in body temperature.

并导致体温上升

It also makes you sleepy,

它还会让你昏昏欲睡

and you lose your appetite and thirst.

感受不到饥饿和口渴

But what's the point of all of these unpleasant symptoms?

但是这些不舒服的症状有什么意义呢？

Well, we're not yet sure,

我们目前还不清楚

but some theorize that they aid in recovery.

但是有些理论认为这有助于恢复

The rise in temperature can slow bacteria

温度升高可以降低病毒活性

and help your immune system destroy pathogens.

帮助你的免疫系统摧毁病原体

Sleep lets your body channel more energy towards fighting infection.

睡眠可以让你的身体积蓄更多能量来对抗感染。

When you stop eating, your liver can take up much of the iron in your blood,

当你停止进食，你的肝脏可以吸收血液中大量的

and since iron is essential for bacterial survival,

细菌赖以生存的铁

that effectively starves them.

有效的消灭细菌

Your reduced thirst makes you mildly dehydrated,

感觉不到口渴会使你轻微脱水

diminishing transmission through sneezes,

减少通过打喷嚏，

coughs,

咳嗽，

vomit,

呕吐，

or diarrhea.

和腹泻传播的病菌。

Though it's worth noting that if you don't drink enough water,

不过值得注意的是，如果你没有喝足够的水

that dehydration can become dangerous.

脱水会变得十分危险。

Even the body's aches make you more sensitive,

你会对身体的疼痛更加敏感，

drawing attention to infected cuts that might be worsening,

特别要注意受感染的伤口可能会恶化

or even causing your condition.

甚至影响你的整体状态。

In addition to physical symptoms,

除了身体上表现出的症状

sickness can also make you irritable,

疾病也会让你感到烦躁，

sad,

and confused.

伤心，

和困惑。

That's because cytokines and prostaglandin

这是因为细胞因子和前列腺素

can reach even higher structures in your brain,

可以到达你大脑中更高的结构

disrupting the activity of neurotransmitters,

破坏神经递质活性，

like glutamate,

如谷氨酸，

endorphins,

内啡肽，

serotonin,

血清素，

and dopamine.

和多巴胺。

This affects areas like the limbic system, which oversees emotions,

这种行为会影响控制情绪的大脑边缘系统

and your cerebral cortex, which is involved in reasoning.

和进行推理的大脑皮层

So it's actually the body's own immune response

所以它是人体自身的免疫反应

that causes much of the discomfort you feel every time you get ill.

导致你每次生病时的不适反应

Unfortunately, it doesn't always work perfectly.

可惜，免疫系统并不是总能完美运行。

Most notably, millions of people worldwide suffer from autoimmune diseases,

最值得注意的是，全球数以百万计的人患有自身免疫性疾病

in which the immune system treats normal bodily cues as threats,

因为他们的免疫系统将正常的身体信号视为威胁

so the body attacks itself.

所以对自身进行攻击。

But for the majority of the human race,

但是对于大多数人，

millions of years of evolution have fine-tuned the immune system

免疫系统历经数百万年的进化

so that it works for, rather than against us.

不会对自身产生排斥反应。

The symptoms of our illnesses are annoying,

我们自身疾病所引发的症状令人不适

but collectively, they signify an ancient process

但总体来说，他们是一种古老的过程

that will continue barricading our bodies against the outside world

并将在未来的世纪中继续保护我们的身体不受外界影响。

for centuries to come.