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  • A war has been going on for billions of years  that breeds well armed monsters, who struggle with  


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

    武装した怪物が生まれては 生存をかけて戦っている

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

    人類に特段の関心はなく ほとんどは比較的無害だ

  • Naegleria fowleri is an amoeba  that has not only developed a  

    免疫系が彼らの武器を 簡単に処理できる

  • deadly taste for human brains but is alsomatch for our defences and stars in dramatic  


  • headlines. What happens when  this monster enters your body?

    Naegleria fowleri というアメーバは 人間の脳を食べて死に至らせ、免疫系にも対応する

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


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

    この怪物が体内に侵入したら 何がおきるのか?

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

    Naegleria fowleri はアメーバだ

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

    核を持つ微生物であり 地球上で最小の生物の一つだ

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

    アメーバは、細菌や他の生物を丸のみして細断する 獰猛なハンターだ

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

    他のアメーバと同様、Naegleria fowleri は 生存のために変形できる

  • it also feels happy in pipes, swimming poolsfountains or spas when they are not properly  

    ほとんどの場合、Naegleria fowleri は栄養体で

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


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


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

    本来の生息場所は淡水で 池、川、湖、温水などだが

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

    残念ながら、居心地のいい場所には パイプ、プール、噴水、温泉などもある

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


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

    水温が高いほど 盛んに繁殖していく

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


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

    アメーバと遭遇する可能性が 最大になるのだ

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


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

    特に温暖な地域では数百万人が 定期的に接触しており

  • as it is not really looking for troubleit just wants to eat a few bacteria.  


  • Instead it is greeted by your natural defensesUnfortunately for humans, Naegleria fowleri  

    まあ概ね問題はなく 感染せずに飲み込むことすら可能だ

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

    アメーバに汚染された水を泳いだり潜ったりして 水が鼻の高さまでくると、事態は悪化する

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

    湖の水一滴には何百万という ウイルス、細菌、アメーバがいるが

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


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

    だが Naegleria fowleri は違う

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

    夏の一日を楽しむ無防備な犠牲者の鼻を拡大し 何が起きるか見てみよう

  • that actually sparks its interest: Nerve cells.

    第一に、アメーバは望んで あなたの鼻に入ったのではない

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

    細菌を少し食べたいだけで トラブルは求めていないのに

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


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

    困ったことに、Naegleria fowleri はなぜか 免疫系のレーダーを潜り抜けるのが非常にうまい

  • releasing various messenger chemicals and  recognizing them via specific receptors.  

    例えば鼻の内側は 粘膜に覆われ

  • One of the most important of  these chemicals is acetylcholine.

    含まれる化学物質は侵入者を殺すか気絶させ 免疫細胞へ警告する

  • Through sheer evolutionary bad  luck, Naegleria fowleri happens to  

    だが Naegleria fowleri は特に困らない

  • have receptors that recognize acetylcholine.  

    落ち着いて景色を眺めつつ この試練に少しイラつく程度だ

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


  • So as your olfactory nerve cells do their jobusing plenty of acetylcholine to talk to the  

    この微生物は 興味をかきたてるものに出会う

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


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

    鼻は嗅覚神経細胞の 巨大ネットワークで満ち

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

    外界の分子を拾い、その情報を 脳内の嗅覚中枢である嗅球に伝える

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

    神経細胞は任務遂行のために 様々な伝達物質を出し

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


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

    特に重要な伝達物質が アセチルコリンだ

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


  • Your brain.

    Naegleria fowleri は偶然にも アセチルコリン受容体を持っており

  • This process can take between one and nine days  

    その伝達物質に強く惹きつけられる 光に蛾が集まるように

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

    嗅覚神経細胞が働くとき 脳への伝達に多量のアセチルコリンが使われ

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

    Naegleria fowleri が 組織に侵入するのだ

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


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

    狂気の特攻隊員である好中球が 攻撃を始める

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


  • so their pieces can be eagerly  consumed. But Naegleria fowleri  

    アメーバは大型の戦士で 強敵との戦いに馴れているので

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

    好中球はアメーバに群がり 身体に穴をあける化学物質を吐いたり

  • develop up to a dozen suckers called food cupsthat look like giant eerie mouths. The amoebae  

    身体の一部を切り取って 食い荒らしたりして殺す

  • engage your brain cells, suck them in and  rip largebitesout of them while they  

    だがアメーバの進路に変更はなく 好中球の攻撃でもたついても

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

    嗅覚神経に沿って 目的地に向かい続ける

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


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

    このプロセスには1~9日かかり その間はたぶん、何も気づかない

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

    しかしそれも嗅覚の中枢であり 脳の入り口である嗅球にたどり着くまでの話だ

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


  • They waste no time and attack the amoebausing all the weapons available to them,  

    魅力的なアセチルコリンを わざわざ放出している

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

    Naegleria fowleri は大虐殺を始め 様々な攻撃分子を猛烈に放出する

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

    分子の一部は、接触した細胞に穴を空ける小型爆弾で 破片にむしゃぶりつける

  • Naegleria fowleri can actually fight backitself attacking and killing many immune cells.

    ここで、このアメーバは増殖を始め いよいよバケモノじみていく

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

    食欲が暴走し、巨大で不気味な 口のような吸盤が1ダースほど作られる

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

    アメーバはあなたの生きた脳にとりつき 吸い込み、嚙みちぎっていく

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

    事態は急速にエスカレートし 死に至る病が発症する

  • usually slows enemies down does nothingas the amoeba actually thrives in the heat.  

    大虐殺を受け、好中球、好酸球、ミクログリアが 何百万と感染組織に侵入する

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

    問題は、免疫系は本来危険なもので 慎重には戦わないことだ

  • A disastrous chain reaction is taking place.  

    森の中の狼を殺すのに 森を焼き払うようなもので

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


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

    ただちに免疫系は攻撃を始める 化学兵器から直接の捕食まで、あらゆる手段でだ

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

    好中球は自爆し 致死的な化学兵器を含むバリアを張る

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


  • It all begins pretty vaguely, a headache, fever,  

    Naegleria fowleri も反撃でき 多くの免疫細胞を攻撃し死滅させる

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

    免疫系は全てを侵略者にぶつけるが 無駄に終わる

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

    侵入者を殺せる小さなタンパク爆弾 「補体系」も容易に無効化される

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

    超兵器のはずの抗体も ただ壊されるか飲み込まれる

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


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


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

    その間もアメーバは増殖し、戦い続け あなたの脳を食い荒らしていく

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


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

    戦闘モードの免疫細胞は 炎症を生じさせる

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

    その結果、血管から大量の体液が 感染部位に流れ込む

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

    決着が遅れるほど さらに体液が脳に流れ込んでいくのだ

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

    ここで人間は 症状の急激な悪化を感じる

  • been a few hundred cases in the last few decadesYou are way more likely to drown in a pool than  

    まずは漠然とした症状の 頭痛、発熱、吐き気、嘔吐から始まり

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

    脳内の戦闘が激化すると 症状も深刻化する

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


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

    脳は強く膨張するが 頭蓋に囲まれ広がれないため

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

    呼吸などを制御する脳幹が 圧迫され機能しなくなる

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

    通常、1週間以内に 患者は死亡する

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

    このアメーバの感染者の97%が 同じ運命をたどる

  • - Oh hey, who are you?

    ほぼ全てのケースで 感染に気付くころには

  • It is me, your existential dread!

    すでに脳内は苛烈な戦闘中で 手遅れなことがほとんどだ

  • - Uhm, ok.


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


  • - Could you not please.

    淡水で生活するアメーバが 人間の免疫系に見事に対処できる理由についてだ

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

    では、この恐るべき殺人アメーバを どれだけ警戒すべきか?

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


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

    Naegleria fowleri は明らかに極めて致死的だし 感染は真の恐怖だが

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


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

    プールで感染するより 溺れる可能性の方が高い

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


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

    しっかり掴まり 防御の第一線を通過する必要もある

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

    結局、Naegleria fowleri は 悪魔でも公衆衛生上の巨大リスクでもない

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

    ただ毎年、不幸な人々が 相手をさせられている

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


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


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

    Naegleria fowleri は水たまりや池 たまにプールにいる脅威の怪物のままだ

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

    基本的には細菌への脅威だが 極めて稀に、人間に牙をむくのだ

A war has been going on for billions of years  that breeds well armed monsters, who struggle with  



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