other monsters for survival. Having no particular  interest in us, most of them are relatively  

孕育出了許多全副武裝的怪物，它們為了生存而與其他怪物搏鬥。

harmless, as our immune systems deal with  their weapons easily. But there are exceptions.

它們對我們沒有特別的意圖，

Naegleria fowleri is an amoeba  that has not only developed a  

大多數都是相對無害的，

deadly taste for human brains but is also a  match for our defences and stars in dramatic  

而我們的免疫系統對付它們的武器也是易如反掌，

headlines. What happens when  this monster enters your body?

但是總有例外。

Naegleria fowleri is an amoeba, a microbe with a  nucleus, one of the smallest lifeforms on earth.  

福氏內格里蟲是一種變形蟲， 不只發展出嗜吃人腦的食性，

It is a voracious hunter of bacteria and other  critters that it devours whole and rips into  

更是我們防衛系統的強大對手、

pieces. Like many amoebea it is able to transform  into different stages that help it survive,  

體內的戲劇性頭條明星

but most of the time Naegleria  fowleri is in its trophozoite stage,  

當這些怪物入侵你身體時發生了甚麼事？

during which it looks like a squishy blob  with tiny arms and hunts, divides and thrives.

福氏內格里蟲

Its natural home is in fresh water: ponds,  rivers, lakes and hot springs. But unfortunately  

是一種變形蟲，

it also feels happy in pipes, swimming pools,  fountains or spas when they are not properly  

地球上最微小的生命形式之一。

treated. The warmer the water, the more it thrives  and multiplies. So in the summer, when humans seek  

它是貪婪的細菌與微生物獵人，

to cool off and enjoy themselves, the chances  are highest that both species will interact.

將其整個吞下並撕成碎片。

Because this makes it hard to avoid, millions of  people regularly have contact with the amoeba,  

就像許多變形蟲一樣，

especially in warmer climates, and many people  even seem to have antibodies against it.  

他可以變形成不同型態階段以幫助生存，

And this is mostly ok, you can even  swallow it without consequences.

但大多數時間中，福氏內格里蟲處於其滋養體期(Trophozoite)，

Things turn bad when people dive or swim in water  contaminated with the amoeba and water splashes  

這段時間內的它看起來像個黏糊糊的斑點、

high up into their noses. In a single drop  of lake water there are millions of viruses,  

有許多迷你觸手狩獵、分裂

bacteria and amoebea and that isn't really a big  deal. But Naegleria fowleri is different. Let  

並成長茁壯。

us zoom into the nose of an unsuspecting victim  enjoying a great summer day and see what happens.

它的天然的家園是乾淨的水中：

First of all, the amoeba doesn't  really want to be inside your nose  

池塘、河流、及天然湧泉。

as it is not really looking for trouble,  it just wants to eat a few bacteria.  

但不幸的是，

Instead it is greeted by your natural defenses.  Unfortunately for humans, Naegleria fowleri  

當沒有適當環境時，

happens to be exceptionally good at generally  flying under the radar of your immune system.  

它也能在水管、

For example, the inside of your nose is covered  by mucosa, a slime filled with chemicals that  

泳池、噴泉、或溫泉池中自得其樂，

kill or stun possible invaders or alert immune  cells. But Naegleria fowleri is not particularly  

水溫愈高，它們愈是健旺與繁殖。

bothered by them and instead calmly checks out the  scenery, mildly annoyed about the whole ordeal.

所以一到夏天，人類尋求清涼與樂趣時，

Now, if you are unlucky, the tiny  critter stumbles over something  

這兩個種族產生互動機率將是最高的。

that actually sparks its interest: Nerve cells.

因此難以避免上百萬人

Your nose is filled with a large  network of olfactory nerve cells  

經常性接觸到變形蟲，

that pick up molecules from the outside and  transmit their information to your olfactory bulb,  

特別是在溫暖的氣候中，

the center of smell in your brain. To do  their job these cells talk to each other by  

且有許多人甚至似乎已經有了對抗它的抗體。

releasing various messenger chemicals and  recognizing them via specific receptors.  

大多數情況下這是沒關係的，

One of the most important of  these chemicals is acetylcholine.

就算你吞下它們也不會有任何後果。

Through sheer evolutionary bad  luck, Naegleria fowleri happens to  

但當人們在受變形蟲污染的水中，水花濺入鼻腔中時，一切就變了調。

have receptors that recognize acetylcholine.  

在單單一滴湖水中含有數百萬的病毒、細菌及變形蟲，

And it seems to attract them irresistibly, a  little like moths that are attracted by light.

這也不算甚麼大問題，

So as your olfactory nerve cells do their job,  using plenty of acetylcholine to talk to the  

但是福氏內格里蟲就不一樣了。

brain, Naegleria fowleri enters your tissue. It  seems to follow the chemical signals upstream.  

讓我們畫面放大，進入一個不疑有他地享受美好夏天的受害者的鼻子裡面，

Neutrophils, crazy suicide warriors begin to  attack the amoebae. Individually they have no  

一探究竟。

chance against them as the invaders are large and  pretty buff fighters, used to dealing with tough  

[第一階段：鼻腔]

enemies. So the defenders swarm the intruders  and kill them either by vomiting chemicals  

首先，其實變形蟲也沒有要進到你的鼻子裡的意思，

that punch holes into them or by literally  ripping parts of them off and devouring them.  

它也不想製造麻煩，

But the Naegleria fowleri train is still on track  and while the Neutrophil attacks slow them down,  

就只是想要吃點細菌而已。

they continue to follow the olfactory  nerves to their final destination:

不過，

Your brain.

它還是得面臨你的天然防禦系統，

This process can take between one and nine days  

對人類而言不幸的是，

and you'll probably not notice  anything during that time.  

福氏內格里蟲恰好是躲避免疫系統雷達的好手，

Until the amoebae reach the olfactory bulb, the  center of smell and entrance to your brain. Your  

舉例來說，在你的鼻子裡面覆蓋著黏膜，

brain cells are nothing more than helpless victims  and they all release that wonderful acetylcholine.

一種內含許多殺死或弄暈入侵者的化學物質的黏液，

Naegleria fowleri initiates a massacre and  releases an onslaught of various attack molecules.  

也能警示免疫細胞。

Some of them are basically little bombs  that rip holes into your cells on contact  

但福氏內格里蟲不會特別被這些干擾，反而能冷靜地欣賞風景，

so their pieces can be eagerly  consumed. But Naegleria fowleri  

對這全部的磨難感到稍稍惱怒。

is now multiplying - and it's also becoming  really creepy. In a feeding frenzy it can  

現在，如果你很不幸，這個小生物會跌跌撞撞，

develop up to a dozen suckers called food cups,  that look like giant eerie mouths. The amoebae  

來到某個東西面前，竟然

engage your brain cells, suck them in and  rip large “bites” out of them while they  

引起了它的興趣：

are still alive. Now things escalate quickly  and the disease that will kill you sets in.

神經細胞。

Alerted by the massacre, millions  of immune cells, Neutrophils,  

你的鼻子充滿了廣大的嗅神經細胞網路，

Eosinophils and microglias invade the  infected tissue. Which is a problem:  

可以收集來自外界的分子

your immune system is dangerous and not  exactly a careful fighter. It's like  

並傳送其訊息到你的嗅球(olfactory bulb)，

burning down a forest to kill the wolves  inside it. A really bad idea in the brain.

也就是在你腦中的嗅覺中心。

They waste no time and attack the amoeba,  using all the weapons available to them,  

為了執行這項工作，這些細胞透過釋放多種信使化學物質向彼此溝通，

from chemicals to trying to eat them  alive. Neutrophils explode themselves  

並以特殊的接收器來辨識這些物質。

to erect barriers spiked with deadly  chemicals. A fierce battle ensues.  

在這當中，其中一個最重要的化學物質是乙醯膽鹼(acetylcholine)。

Naegleria fowleri can actually fight back,  itself attacking and killing many immune cells.

純粹因為演化上的霉運，

The immune system now throws everything it has at  the invader but in vain. The complement system,  

福氏內格里蟲剛好擁有

tiny protein bombs that can kill intruders on  their own, are easily disabled. Antibodies,  

可以辨識乙醯膽鹼的接收器。

usually one of your superweapons, are just  destroyed or swallowed. A high fever that  

而這似乎對其有不可抗拒的吸引力，宛如飛蛾撲火一般。

usually slows enemies down does nothing,  as the amoeba actually thrives in the heat.  

所以當你的嗅神經細胞做著他們的工作，

All the while the amoebae continue to  multiply, fight and devour your brain cells.

用大量的乙醯膽鹼和大腦對話，

A disastrous chain reaction is taking place.  

[第二階段：嗅神經]福氏內格里蟲就進入你的組織當中，

One major thing your immune cells do when  they fight is to cause inflammation. Which  

興許是

directs large amounts of fluid from your  bloodstream into the site of an infection.  

為了追溯化學訊號的上游。

So as the battle rages on without a clear  winner, more and more fluid enters the brain.

嗜中性球(Neutrophils)，瘋狂的自殺戰士會開始攻擊變形蟲，

At this point the human will feel  symptoms that quickly escalate.  

雖然單一顆嗜中性球對上它們毫無勝算，

It all begins pretty vaguely, a headache, fever,  

因為這個入侵者既龐大、還是個開掛的打手、

nausea and vomiting. As the battle spreads  rapidly through the brain serious symptoms appear,  

足以應付頑強的敵人。

from confusion, inability to concentrate  to fatigue, seizures and hallucinations.  

所以守護者們大量湧向入侵者，藉由釋出化學物質、

The brain swells up massively but can't expand due  to the bones surrounding it. So it compresses and  

對它們穿孔或碎屍萬段(字面上的意思)再吞噬，以殺死它們。

disables the brainstem that controls things like  breathing. Usually within a week the patient dies.

但福氏內格里蟲依然勢不可擋，當嗜中性球的攻勢拖慢它們的腳步，

Up to 97% of patients infected by the  amoeba share this fate. In almost all cases,  

它們持續沿著嗅神經來到它們的最終目的地：

by the time an infection by Naegleria fowleri is  recognized the disastrous battle for the brain  

你的大腦。[第三階段：大腦]

is already so far along that there is almost  nothing to be done. Not only do we currently  

這整個過程可能花費1~9天，

not have effective treatments, there are also an  abundance of open questions about how an amoeba  

而你在這段時間內可能也沒注意到任何異常。

that usually enjoys its life in open water, is  able to overcome our immune system so effectively.

直至變形蟲抵達嗅球，

So how worried do you need to be about this  horrifying killer amoeba? Well, not very. While  

也就是嗅覺中心

the Naegleria fowleri is clearly extremely deadly  and the infection truly horrible, there have only  

兼通往大腦的入口。

been a few hundred cases in the last few decades.  You are way more likely to drown in a pool than  

你的腦細胞不過是無助的受害者，

to get infected. Not only does the amoeba need  to be flushed high up your nose, it also needs  

且它們全部都會釋放那美妙的乙醯膽鹼。

to get a good grip and it also has to make its  way through the first lines of your defences.

福氏內格里蟲展開了屠殺、

Ultimately Naegleria fowleri is neither evil  nor a huge public health risk. But every year  

並釋放多種攻擊分子的猛攻：

some unlucky people have to deal with it. We still  have so much to learn about it and until we find a  

有些基本上就像小型炸彈，接觸時會在你的細胞上炸出洞來，所以它們就能將細胞碎片大快朵頤。

way to treat it, Naegleria fowleri will continue  to be this vague and horrifying thing, hunting  

但福氏內格里蟲此時正要分裂繁殖，

in puddles and lakes and sometimes pools. Usually  for bacteria. And very occasionally, for people.

真的令人毛骨悚然。

- Oh hey, who are you?

再瘋狂進時的情況下他能衍生出許多吸盤，稱作食泡(food cup)，

It is me, your existential dread!

看起來就像是張巨大怪嘴。

- Uhm, ok.

變形蟲攻擊你的腦細胞，

I'm here to make you question your own  existence and everything you hold dear in life!

吸住它們，

- Could you not please.

並大口撕咬，

Tooooooo late, just look at all these amazing  posters FULL of humbling visualisations like the  

而此時腦細胞們還是活的。

scale of the universe. LOOK! How huge it is and  how small you are! Look at the education edition,  

但現在事情很快就加劇了，

how it dives deep into the history of evolution or  all these other scientific fields to make you feel  

這個會置你於死地的疾病到來。

bad for all the stuff you don't know! Or  look at this one, IT GLOWS IN THE DARK!

由於感知到這場屠殺，

- But Dread, these do make me feel good  actually! They do fill me with excitement  

數百萬的免疫細胞：嗜中性球、

and awe about how amazing our universe is and  I love learning! And look how pretty they are!

嗜酸性球(Eosinophils)及微膠細胞(Microglia)進入被感染的組織，

Nooooooooo, I can't persist in  the presence of awe. Graglgrglglg.

但這裡有個問題：

If you too want to overcome your existential  dread, make your life beautiful and also support  

你的免疫細胞雖然危險

Kurzgesagt so we can put thousands of hours  into our videos and release them for free,  

卻不算是個謹慎的打手，

you can get these and many many  more amazing posters or shirts or  

這就像燒毀森林以殺死裡面的狼群，

so many more things in our shop. We put as  much care into our products as into our videos,  

但發生在大腦裡，真的是個爛主意。

trying to find something clever or a new angle  that will challenge your perspective while still  

它們分秒必爭並攻擊變形蟲，用盡手上所有武器：

teaching you the core aspects. It's the best  way to support what we do on this channel.

像是化學物質或試著活生生吃了它。