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People have been scared of rabies for thousands of years,
几千年来，人们对狂犬病一直十分忌惮，
many times depicting their fear in drawings and carvings of menacing dogs.
很多时候，他们都将这种恐惧表现在了绘有或画有一脸凶相的恶狗的绘画或雕刻作品上。
But rabies is scary for more reasons than just a painful bite.
然而，狂犬病之所以可怕，不仅仅是因为被咬那一口很疼。
Because once the virus is inside us, it not only destroys our body, but damages our mind,
还因为狂犬病毒一旦进入我们体内，不仅会破坏我们的身体，还会损害我们的大脑，
and it can happen fast, or lay dormant for years before fatally attacking.
而且，它既可以发生得很快，也可以潜伏数年，直到对你发出致命一击。
So how exactly do we get from a dog bite to a complete behavioral change to...death?
问题是，从被狗咬到行为彻底转变再到……死亡，这中间究竟发生了什么？
The virus that causes rabies is spread through saliva,
原来，引发狂犬病的病毒会通过唾液进行传播，
so the most common way to contract rabies is through an animal bite,
因此，感染狂犬病最常见的方式就是动物咬伤，
most likely from a dog, bat, raccoon, skunk or fox.
其中最为常见的又数被狗、蝙蝠、浣熊、臭鼬或狐狸咬伤。
There have been a few, rare cases of transmission through infected organ donors and an even rarer instance of a lab accident,
尽管的确存在少数罕见的，被感染的器官捐赠者进行传播的病例，也存在更为罕见的，因为实验意外传播的案例，
but for the most part it comes down to a bite from a rabid animal.
但大多数情况下都是通过被狂犬病动物咬伤进行传播的。
So even though it’s a virus that can infect and kill humans, it’s studied considerably in veterinary labs.
所以，即使这是一种可以感染并致死人类的病毒，狂犬病研究主要还是在兽医实验室里进行。
OK. I am Dr. Susan Moore.
好的。我是苏珊·摩尔医生。
I'm the laboratory director of the rabies laboratory at Kansas State University,
现任堪萨斯州立大学狂犬病实验室主任，
part of the veterinary diagnostic lab within the vet school here.
我们实验室是我们学校兽医学院兽医诊断实验室的一部分。
We are the largest rabies serology laboratory in the world.
也是世界上最大的狂犬病血清学实验室。
So the rabies virus is in the family lyssavirus, lyssa means rage really.
狂犬病毒是狂犬病毒属这一分类下的一种病毒，lyssa的本意是愤怒。
So that kind of tells you what this group of viruses are capable of.
这基本上也就告诉了你这类病毒的能力。
And what they’re capable of is causing a very quick and painful death caused by the virus making its way into your brain.
它们的能力就是进入你大脑的病毒能造成非常迅速却也十分痛苦的死亡。
It's a neurotropic virus.
狂犬病毒是一种嗜神经病毒。
So that means it's preferentially going to infect neural tissue or neural cells.
意思就是它会优先感染神经组织或神经细胞。
So when it gets injected into the skin or the muscle, it's not going to replicate all that well
也就是说，当它被注入皮肤或肌肉时，它并不会复制得很厉害，
but all it needs to do is replicate enough that it can get to that neuromuscular junction
但它只需要复制足够数量，使其能到达神经肌肉接点就行，
where it can go from the muscle cells into the central nervous system.
以为只要能做到这一点，它就可以从肌肉细胞进入中枢神经系统。
Now, at this point you’d think your immune system would kick in, recognize this dangerous intruder and destroy it.
此时，你可能会觉得你的免疫系统会被激活，识别这个危险的入侵者并将其摧毁。
But, your immune system doesn’t see it.
问题是，你的免疫系统是看不到狂犬病毒的。
This is thought to be because the virus replicates slowly in the muscle tissue, slow enough not to cause any alarm.
人们认为，这是因为病毒在肌肉组织中复制缓慢，慢到不会触发任何警报。
This gives it a chance to reach the nervous system,
所以就给了狂犬病毒到达神经系统的机会，
where it hitches a ride up to the brain and slips through the blood brain barrier.
在那里，它就能搭上便车进入大脑，穿过血脑屏障。
It’s behind this shield where the rabies virus can flourish while still being able to hide from our immune system,
狂犬病毒就是在这道屏障之后获得大量繁殖的机会，同时避开我们的免疫系统的，
because the blood brain barrier evolved to keep dangerous or harmful things out.
因为血脑屏障进化的结果就是会将危险或有害的东西拒之门外。
But sometimes that includes immune cells.
但有时免疫细胞也在它们的屏蔽清单之上。
In fact, if T cells do get past the blood brain barrier,
事实上，即便T细胞真的通过了血脑屏障，
the rabies virus has evasion techniques where it actually kills the T cells that are coming in.
狂犬病毒也有躲避技术，能够杀死已经突破血脑屏障的T细胞。
As the virus replicates in the brain, it starts to mess with the brain’s cellular proteins, causing neural dysfunction.
病毒在大脑中开始复制之后，就会开始扰乱大脑的细胞蛋白，导致神经功能出现障碍。
This is where certain symptoms of rabies start and how you can tell the infection has fully set in.
这时，狂犬病的某些症状就会开始显现出来，你也可以判断你已经彻底被感染了。
Once the infection has fully set in,
一旦被彻底感染，
it will start traveling back out through the nerves into innervated organs, hair follicles.
病毒就会通过神经离开大脑，回到由神经支配的器官，毛囊。
But again, particularly through to the salivary glands so that it could be transmitted out.
但主要还是会回到唾液腺，因为这样它就可以往其他宿主身上传播了。
These neurological symptoms also help the virus transfer to a new host.
下面这些神经症状也有助于病毒转移到新的宿主身上。
Hypersalivation ensures there is enough rabies-infected saliva in the optimal transmission location, your mouth.
唾液分泌过多可以确保最佳的传播位置，也就是你的口腔内有足够多被狂犬病感染的唾液。
And hydrophobia, or trouble swallowing, ensures that it stays there.
恐水症和吞咽困难则可以确保唾液始终留在你的口腔内。
In animals, the aggression can result in an attack on another animal or a human.
被感染动物产生的攻击性会引发它们对另一只动物或人类的攻击。
Put all three of those together and you have a very effective way to ensure the rabies virus is passed on.
这三种症状结合到一起就有了确保狂犬病毒得以传播的有效方式。
Saliva is the way that rabies is transmitted.
唾液是狂犬病传播的途径。
The way the virus is adapted, it is not in blood. It's not in body fluids.
狂犬病毒适应宿主的方式不是通过血液，也不是通过体液。
So it has to find a way to be transmitted effectively, right, to perpetuate its existence.
所以它必须找到一种有效传播的方式，能让它永远存在的方式。
Now, this neurological damage caused by the infection is the thing that finally tips off the immune system.
这时，这种由感染引起的神经损伤终于能激活免疫系统了。
However, at this point it’s too late.
但太晚了。
Even though your immune system is finally going after the virus, it has already spread throughout the body.
即便你的免疫系统终于要对付这种病毒了，问题是这时候病毒已经扩散到你的全身了。
After that you have to remember this period is pretty short.
然后，你要记住，这段时间很短。
There's just a couple days because then it'll progress into a coma and then death which is usually due to some kind of organ failure.
一般只有几天的时间，因为它会让你进入昏迷状态，然后死去，通常是以某种器官衰竭的形式。
But a bite from a rabid animal doesn’t always mean certain death.
但是，被感染了狂犬病的动物咬一口并不意味着你就一定会死。
People who have been exposed to the rabies virus can get a series of shots that can boost the immune system and fight off the virus,
接触过狂犬病毒的人可以注射一系列疫苗来增强免疫系统，击退病毒，
you just need to get to it before it reaches the brain.
你只需要在它到达大脑之前接种疫苗即可。
So surviving rabies is all about timing and the location where you get bit.
所以，战胜狂犬病完全取决于时间和你被咬的位置。
Where you get bit. It plays a big role.
被咬的位置也非常重要。
So since the virus has to travel through the nerve system, the closer, and get to the brain, the closer that bite is to the brain, the better for the virus.
既然病毒必须穿过神经系统……越靠近……然后进入大脑，所以咬到的地方离大脑越近，对病毒就越有利。
Bats are a danger for that reason that it's going to be biting probably around your head or your hands.
正因为如此，蝙蝠就显得很危险，因为它可能会咬到你的头或手。
But also you don't notice a bat bite because the teeth are so small and they are so small.
而且你即便是被蝙蝠咬了，也很有可能没注意到，因为它们的牙齿很小，而且它们本身就很小。
Maybe...You have a bat on your shoulder and you don't know it.
也许……它落在了你肩上，你都浑然不知。
You just looked on your shoulder, didn't you?
你看你肩膀了，是不是?
