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Even though they're widely infected with notoriously deadly viruses,
尽管它们被众所周知的致命病毒广泛感染，
they don't actually seem to get sick from them. The virus can be found in their bodies, but they don't have any symptoms.
但它们似乎并没有因此而生病。它们身体中可以找到这些病毒，但是它们没有出现任何症状。
As for how that's possible? Well, we still have more questions than answers,
至于其中原因？我们现在对此的问题比答案要多，
but researchers have discovered a few evolutionary quirks about bat immune systems that help make that happen.
但是研究人员发现了一些关于帮助蝙蝠不生病的免疫系统的进化怪癖。
In part, that's because active viral infections in bats tend to be pretty short-lived, thanks to their hypervigilant interferon production systems.
在某种程度上，这是因为蝙蝠体内活跃的病毒感染往往是相当短暂的，这要归功于它们高度警惕的干扰素生产系统。
Remember how we said DNA damage is a signal of infection?
还记得我们说过DNA损伤是感染的信号吗？
That's because viruses try to reprogram cells to create copies of themselves. But cells aren't sitting ducks during this process.
这是因为病毒试图重新编程细胞来复制自己。但在这个过程中，细胞不会坐以待毙。
In addition to calling out for help—which is that whole inflammation bit we discussed—cells have an internal defense mechanism.
除了寻求帮助——就是我们讨论的整个炎症反应——细胞拥有一种外部的防御机制。
They can make a protein called interferon alpha, which activates genetic and chemical tools that reduce the virus' ability to multiply and spread.
它们可以制造一种被称为干扰素alpha的蛋白质，激活减少病毒复制和传播能力的基因和化学工具。
Every other mammal we know of switches their interferon system on when an infection occurs.
我们多知道的每一种其他哺乳动物都会在发生感染时启动它们的干扰素系统。
But genomic studies suggest bat cells always have their interferon alpha genes activated!
但基因组研究表明，蝙蝠细胞总是会激活它们的干扰素基因！
This drastically cuts down the time it takes to react when a virus is present, so it allows bats to nip the infection in the bud before it becomes a full-blown disease.
这彻底缩短了发现病毒时所需的反应时间，所以它使蝙蝠能够在疾病全面爆发之前将感染扼杀在萌芽状态。
And—of course—there's more. All mammalian cells contain an enzyme called ribonuclease L
当然，不止这些。所有的哺乳动物细胞都含有一种叫做核糖核酸酶L的酶，
which, when activated, chops up viral RNA to stop a pathogen from spreading.
当这种酶被激活时，它会切断病毒RNA以阻止病原体的传播。
But, in us and most other mammals, activating this enzyme takes a complex chain of steps—so it's not super quick.
但是在人类和大部分哺乳动物体内，激活这种酶需要一些列复杂的步骤——所以不是特别快。
But bats, on the other hand, can activate it directly with interferons, drastically speeding up infection containment.
但在另一方面，蝙蝠可以直接用干扰素激活它，极大加快了对感染的控制。
Scientists also think this fast activation of ribonuclease L helps bats outsmart viruses
科学家还认为快速激活核糖核酸酶L帮助蝙蝠
that have evolved to inhibit the enzyme before it can be switched on—something HIV does in humans, for example.
在启动这种酶前就能击败那些进化来抑制这种酶的病毒——比如HIV就是这样。
So basically, when bats do get viruses, they're able to quickly clear them out for the most part.
所以基本上，当蝙蝠感染病毒时，它们能迅速清除大量病毒。
They can still fall prey to at least a few, like the rabies virus. And even quick suppression of a virus can mean it stays around in a group of bats.
它们仍然会成为至少几种病毒的猎物，比如狂犬病毒。即使病毒被迅速抑制，也意味着它会留在一群蝙蝠中。
Bats tend to huddle close together when they roost. Plus, they fly around in the same areas as bats from other colonies,
蝙蝠在栖息时往往挤作一团。另外，它们和其他群体的蝙蝠在同一区域飞行，
and they're constantly spraying snot and saliva everywhere when they echolocate.
当它们回声定位时，它们会不停地四处喷射鼻涕和唾液。
So there's a good chance that, during that window when a bat has a virus that is actively replicating, it will spread it to another bat.
所以很有可能，在这段时间里，当一只蝙蝠体内有一种正在积极复制的病毒时，它会把病毒传染给另一只蝙蝠。
That means even if each bat only hosts a virus for a short time, it can linger in the population. And even this probably isn't the full picture.
这意味着即便每一只蝙蝠只在短时间内携带一种病毒，它也可以在种群中逗留。甚至这可能还不是全部。
Mathematical models indicate that, by themselves, bats' social habits don't completely explain why they host so many viruses.
数学模型表明，蝙蝠的社交习性本身并不能完全解释它们为什么会携带这么多病毒。
Instead, research suggests that the viruses themselves have figured out how to lie dormant and undiscovered—like in the bats' lungs, spleens, or intestines.
相反，研究表明病毒本身已经找到了如何潜伏且不被发现的方法——比如在蝙蝠的肺部、脾脏或肠道中。
And then, when the bat gets stressed—like when it's roused from hibernation—that stress temporarily dampens its anti-virus systems,
然后，当蝙蝠受到压力时——比如从冬眠中醒来时——这种压力会暂时抑制它的反病毒系统，
allowing any hidden viruses to emerge. This leads to another period of increased viral replication and shedding.
让任何隐藏的病毒出现。这导致了另一段时期的病毒复制和传播。
So again, the bat can transfer the infection to other animals.
所以，蝙蝠可以把感染传染给其他动物。
Then, its antiviral systems get back up to speed, and the viruses are eliminated or driven back into hiding.
然后，它的抗病毒系统恢复正常，病毒被消灭或被赶回隐藏起来。
Still, even when a virus is replicating and being shed, bats generally don't seem sick—not like a person would with the same virus.
尽管如此，即使病毒在复制和传播，蝙蝠通常也不会生病——不像人感染了同一种病毒。
And that's likely because their inflammation-dampeners are still running.
这可能是因为它们的消炎装置还在运转。
So, they're still suppressing a lot of the immune response that would make them noticeably sick.
所以它们仍然会抑制很多会让它们明显生病的免疫反应。
And that may also be why viruses that are deadly to us aren't lethal to them.
这可能也是为什么对人类如此致命的病毒，对它们却是不致命的。
It turns out that the most severe symptoms of illnesses like MERS and Ebola,
结果证明大疾病，最严重的疾病症状，如中东呼吸综合症和埃博拉病毒，
the symptoms usually responsible for their lethality aren't caused by what the virus itself does to the body.
通常导致其致命性的症状并不是由病毒本身对人体造成的。
Instead, they're the result of the destructive, catastrophic inflammation the virus triggers.
相反，它们是病毒引发的破坏性、灾难性炎症的结果。
This includes an extreme systemic reaction called a cytokine storm,
这包括一种被称为“细胞因子风暴”的极端系统反应，
where an over-release of pro-inflammatory signaling proteins turns a person's own immune system into their worst enemy.
在这种反应中，促炎信号蛋白的过度释放会把一个人的免疫系统变成他们最大的敌人。
And some researchers think that our aggravated inflammatory response may actually be
一些研究人员认为我们恶化的炎症反应实际上可能是
because these viruses have evolved to dodge the super-refined immune systems of bats.
因为这些病毒已经进化到可以避开蝙蝠超精细的免疫系统。
Basically, they evolved to survive in a host that constantly and aggressively attacks their ability to replicate.
基本上，它们是为了在一个不断攻击它们复制能力的宿主中生存而进化的。
So when that assault is suddenly weaker in a new host,
因此，当这种攻击在一个新宿主体内突然减弱时，
they go wild and produce a lot of little virus babies that send the host's immune system into panic mode.
它们就会失控，产生大量的小病毒宝宝，让宿主的免疫系统进入恐慌模式。
This kind of overreaction can also happen to bats. It's just not usually in response to viruses.
这种过度反应也会发生在蝙蝠身上，只是通常不是对病毒产生反应。
Instead, it seems like their unique immune system may leave them vulnerable to non-viral invaders.
相反，它们的特别免疫系统可能使它们容易受到非病毒入侵。
The most infamous example of this is White Nose Syndrome, a fungal pathogen which has devastated bat populations in North America.
最臭名昭著的例子就是白鼻综合症，这是一种真菌病原体，已经摧毁了北美的蝙蝠种群。
Some researchers think the bats' dampening of inflammation —especially during hibernation—makes it easy for the fungus to infect the bat.
一些研究人员认为，蝙蝠对炎症的抑制——尤其是在冬眠期间——使得真菌很容易感染蝙蝠。
Then, once the bat awakes, it's immune system does react—only,
一旦蝙蝠醒来，它们的免疫会有所反应——
it goes too far, which can lead to the bat developing a life-threatening form of systemic inflammation.
只是反应太过严重，会导致蝙蝠发展成一种危及生命的全身性炎症。
So, basically, the reason they die from white nose is similar to why we die from viruses like MERS and Ebola.
所以它们死于白鼻子的原因和我们死于中东呼吸综合症和埃博拉病毒的原因是一样的。
That may mean that the key to saving bats from this fungus (and us, from the deadly viruses they carry) may lie in further research on bats.
这或许意味着将蝙蝠从这种真菌（以及我们，从它们携带的致命病毒）中拯救出来的关键在于对蝙蝠的进一步研究。
And also, if we're being selfish, we have a lot of other diseases characterized by inflammation, like heart disease and diabetes.
而且，如果我们自私的话，我们还有很多其他的以炎症为特征的疾病，比如心脏病和糖尿病。
So studying their inflammation system may lead to treatments for our chronic conditions.
所以研究它们的炎症系统可能有助于治疗我们的慢性疾病。
And the same goes for studies on the ways that bats keep viruses at bay.
对蝙蝠如何防范病毒的研究也是如此。
Right now, we only have effective antiviral drugs for about 10 of the more than 200 viruses that can infect humans, and very few broad-spectrum antivirals.
目前，我们只有大约10种有效的抗病毒药物，而能感染人类的病毒超过200种，广谱抗病毒药物非常少。
If we can discover more of bats' tricks, we might be able to use them to develop therapies against the diseases they host and other dangerous viruses.
如果我们可以发现蝙蝠的更多秘密，我们或许能够用它来帮助我们研发针对它们所携带的疾病和其他危险病毒的疗法。
Plus, all this research might help us live longer. Many researchers think bats' immunological adaptations are also behind some of their other superpowers,
另外，这些研究或许能帮助我们更加长寿。很多研究人员认为蝙蝠的免疫系统适应能力也是它们其他超能力的原因，
like how they seem to rarely get cancer, or how they live incredibly long lives for animals of their size.
比如它们似乎很少得癌症，或者就它们这种体型的动物而言，它们如何活得如此之久。
Usually, little animals live fast and die young. But Brandt's bats can live for over 40 years even though they only weigh 4 to 8 grams!
通常，小动物寿命短，死得早。布氏鼠耳蝠体重只有4到8克，但它们可以活40多年！
So instead of looking at bats as species zero, we should think of them as flying keys to longevity and resilience.
所以我们不应该把蝙蝠视为零物种，而应该把它们视为长寿和恢复力的飞行钥匙。
And in the end, they're going to be our allies in health, not our enemies.
最后，它们将成为我们健康的盟友而不是敌人。
Speaking of allies, before we go, we'd like to thank our patrons on Patreon.
说到盟友，结束本期节目前骂我们想要感谢我们赞助人。
It takes a lot of people to make long, complex episodes like this come to life,
制作像这样的长而复杂的情节需要很多人，
and we can only bring all those people together because of the support of our patron community. So, thank you!
因为我们的赞助人团体的支持，我们才能把所有这些人聚集在一起。所以谢谢大家！
And if you want to learn more about joining this awesome group of people who help keep SciShow running, you can learn more at Patreon.com/SciShow.
如果你想了解如何加入我们，帮助本节目的继续运营，你可以登陆Patreon.com/SciShow了解更多。
