through a series of channels called bronchi,

通過一系列稱為支氣管的通道。

and finally reaches little clusters of air sacs called alveoli.

最後到達被稱為肺泡的小氣囊群。

There are some 600 million alveoli in the lungs,

肺部約有6億個肺泡。

adding up to a surface area of roughly 75 square meters—

加起來大約75平方米的面積-。

the size of a tennis court.

網球場的大小。

These tiny sacs, only one cell thick, facilitate a crucial exchange:

這些只有一個細胞厚的小囊，促進了關鍵的交換。

allowing oxygen from the air we breathe into the bloodstream

讓我們呼吸的空氣中的氧氣進入血液。

and clearing out carbon dioxide.

並清除二氧化碳。

Pneumonia wreaks havoc on this exchange.

肺炎在這次交流中大肆破壞。

Pneumonia is an infection of the alveoli that causes them to fill with fluid.

肺炎是指肺泡感染，導致肺泡充滿液體。

There are many different kinds of pathogens that can cause pneumonia.

能引起肺炎的病原體有很多種。

The most common ones are viruses or bacteria.

最常見的是病毒或細菌。

These microscopic invaders enter the body via droplets either in the air we breathe,

這些微觀入侵者通過飛沫進入人體，要麼是在我們呼吸的空氣中。

or when we touch our eyes, noses,

或當我們觸摸我們的眼睛，鼻子。

or mouths after touching a contaminated surface.

或接觸汙染表面後的嘴。

Then, they face the respiratory tract's first line defense:

然後，他們面對的是呼吸道的一線防線。

the mucociliary escalator.

粘液自動扶梯。

The mucociliary escalator consists of mucus that traps invaders and tiny hairs

黏膜自動扶梯由黏液組成，可以捕捉入侵者和微小的毛髮。

called cilia that carry the mucus toward the mouth, where it can be coughed out.

稱為纖毛，將粘液帶向口腔，在那裡可以咳出。

But some of these invaders may get past the mucociliary escalator

但這些入侵者中的一些人可能會通過粘膜自動扶梯。

into the lungs, where they meet the alveoli.

進入肺部，在那裡它們與肺泡相遇。

Because alveoli serve as critical exchange points

因為肺泡是關鍵的交換點

between the blood and air from the outside world,

外界的血液和空氣之間。

they have their own specialized types of white blood cells, or macrophages,

他們有自己專門的白細胞類型，或巨噬細胞。

which defend against foreign organisms by enveloping and eating them.

它們通過包圍和吃掉外來生物來抵禦外來生物。

When pathogens enter the lungs, the macrophages work to destroy them.

當病原體進入肺部時，巨噬細胞會努力消滅它們。

The immune system releases additional white blood cells in the alveoli to help.

免疫系統會在肺泡中釋放額外的白血球來幫助。

As these immune cells fight the pathogens, they generate inflammation—

當這些免疫細胞對抗病原體時，它們會產生發炎--。

and fluid as a by-product of the inflammation.

和液體作為發炎的副產品。

When this fluid builds up,

當這種液體積聚起來的時候。

it makes gas exchange inside the alveoli much more difficult.

它使肺泡內的氣體交換更加困難。

As the level of carbon dioxide in the bloodstream begins to rise,

隨著血液中二氧化碳含量開始上升。

the body breathes more quickly to try to clear it out and get more oxygen in.

身體呼吸更快，以嘗試清除它，並獲得更多的氧氣。

This rapid breathing is one of the most common symptoms of pneumonia.

這種快速呼吸是肺炎最常見的症狀之一。

The body also tries to force the fluid out of the alveoli through coughing.

身體也會試圖通過咳嗽將肺泡中的液體逼出來。

Determining the cause of pneumonia can be difficult,

確定肺炎的原因是很困難的。

but once it is established, doctors can prescribe antibiotics,

但一旦確定，醫生就可以開出抗生素。

which may include either antibacterial or antiviral treatments.

其中可能包括抗菌或抗病毒治療；

Treatment with antibiotics helps the body get the infection under control.

用抗生素治療有助於身體控制感染。

As the pathogen is cleared out,

隨著病原體的清除。

the body gradually expels or absorbs fluid and dead cells.

身體逐漸排出或吸收液體和死亡細胞。

The worst symptoms typically fade out in about a week,

最嚴重的症狀一般一週左右就會消失。

though full recovery may take as long as a month.

雖然完全恢復可能需要一個月之久。

Otherwise healthy adults can often manage pneumonia at home.

否則健康的成年人通常可以在家中處理肺炎。

But for some groups, pneumonia can be a lot more severe,

但是對於一些群體來說，肺炎的病情會嚴重很多。

requiring hospitalization and oxygen, artificial ventilation,

需要住院和吸氧、人工呼吸。

or other supportive measures while the body fights the infection.

或其他支持性措施，同時身體對抗感染。

Smoking damages the cilia,

吸菸會損害纖毛。

making them less able to clear even the normal amount of mucus and secretions,

使其連正常的粘液和分泌物都無法清除。

let alone the increased volume associated with pneumonia.

更何況是與肺炎相關的體積增大。

Genetic and autoimmune disorders

遺傳性和自身免疫性疾病

can make someone more susceptible to pathogens that can cause pneumonia.

可以使人更容易受到可引起肺炎的病原體的影響。

Young children and the elderly also have impaired clearance

幼兒和老人的清除能力也受損

and weaker immune systems.

和免疫系統較弱。

And if someone has viral pneumonia,

而如果有人得了病毒性肺炎。

their risk of bacterial respiratory infection is higher.

他們發生細菌性呼吸道感染的風險更高。

Many of the deaths from pneumonia are due to lack of access to healthcare.

許多因肺炎而死亡的人都是由於缺乏醫療服務。

But sometimes, even with appropriate care,

但有時，即使是適當的護理。

the body enters a sustained fight against the infection it can't maintain,

身體進入持續對抗感染的狀態，無法維持。

activating inflammatory pathways throughout the body,

激活全身的發炎途徑。

not just in the lungs.

不僅僅是在肺部。

This is actually a protective mechanism,

這其實是一種保護機制。

but after too long in this state organs start shutting down,

但在這種狀態下時間太長後，器官開始關閉。

causing shock and sometimes death.

導致休克，有時甚至死亡。

So how can we prevent pneumonia?

那麼如何預防肺炎呢？

Eating well and getting enough sleep and exercise

良好的飲食、充足的睡眠和運動

helps your body fight off infections.

幫助你的身體抵抗感染。

Vaccines can protect against common pneumonia-causing pathogens,

疫苗可以預防常見的致肺炎病原體。

while washing your hands regularly helps prevent the spread of these pathogens—

同時，定期洗手有助於防止這些病原體的傳播--。

and protect those most vulnerable to severe pneumonia.

並保護最容易患嚴重肺炎的人。