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Both hitch a ride in on protein on our cell membranes called angiotensin converting enzyme 2 or ACE2.
这两种物质都利用了细胞膜上的一种叫做血管紧张素转换酶2或ACE2的蛋白质。
Normally, these enzymes play a big role in maintaining blood pressure, so they're found on a lot of cells,
通常情况下，这些酶在维护血管方面起了很大作用，所以很多细胞中都有这种酶，
especially ones in your respiratory system. And both viruses use a specific protein to grab onto ACE2.
尤其是呼吸系统中的细胞。两种病毒都使用一种特殊的蛋白质来抓住ACE2。
It's called the spike protein because, well, it looks like a spike sticking out of the surface of the virus.
它被称为刺突蛋白，因为，它看起来像一个从病毒表面伸出来的刺突。
But what differs between the SARS virus, SARS-CoV-1, and this virus is how well they stick to ACE2.
但SARS病毒SARS-CoV-1和这种病毒的不同之处在于它们粘附在ACE2上的方式。
Researchers estimate that this newer coronavirus binds ten times more tightly to human ACE2s.
研究人员认为，新型冠状病毒与人类ACE2s的结合要紧密十倍。
And that's probably because it has a number of changes to the part of the spike that actually binds with the enzyme.
这可能是因为，它在与酶结合的部分有一些变化。
In fact, about half of the amino acids in this particular region differ between the two viruses.
实际上，这个特定区域中，有一半的氨基酸在两种病毒之间是不同的。
This matters because the better a virus is at binding to its receptor, the fewer viruses you need to infect a cell.
这很重要，因为病毒与受体结合得越好，感染细胞所需的病毒就越少。
And ultimately, that may mean the infectious dose is actually lower for this virus than SARS or other respiratory viruses.
最终，这可能意味着这种病毒感染剂量比SARS或其他呼吸道病毒要低。
If so, that could also help explain why people can spread this virus before they're really ill, and why it can travel in smaller droplets.
如果是这样，那么或许能够帮助解释为什么人们在生病前就能传播这种病毒，以及为什么这种病毒可以在小液滴中传播。
It's back to that numbers game—if it takes fewer viruses to infect someone,
这又回到了数字游戏——如果感染一个人需要更少的病毒，
then even small exposures to the virus are more likely to get someone sick.
那么即使是很小的病毒接触也更有可能使人生病。
But there may also be other things helping to lower the infectious dose, too.
但是还有很多其他方面帮助降低了感染剂量。
Like, there's a small chunk added to the spike protein that experts think might make it more infection-ready from the get-go.
比如，有一小块病毒被添加到刺突蛋白中，专家认为这可能会让它从一开始就更容易感染。
In other viruses, similar additions seem to make them more dangerous.
在其他病毒中，类似附加物似乎会让它们变得更加危险。
So this is one of the leads scientists are eagerly following up on to figure out how this virus spreads so easily.
因此，这是科学家们迫切想要弄清楚这种病毒是如何如此轻易地传播的主要原因之一。
Even still, the infectious dose is just part of the story. To fully understand why this virus can replicate so well,
尽管如此，感染剂量只是故事的一部分。要完全理解为什么这种病毒可以迅速复制，
scientists also need to understand everything that happens after it's pulled into the cell.
科学家们还需要了解它被拉入细胞后发生的一切。
So far, what's clear is that, like other coronaviruses, this virus hijacks a process called endocytosis.
到目前为止，可以确定的是，像其他冠状病毒一样，这种病毒劫持了一个叫做内吞作用的过程。
This is when a cell's membrane folds inward, creating a little bubble that carries in proteins and other stuff it can digest for parts.
这是指细胞膜向内折叠，形成一个小气泡，里面含有蛋白质和其他可以消化的物质。
SARS-CoV-2 can hitch a ride in these bubbles and use them as a one-way ticket to the cell's protein factories.
SARS-CoV-2可以搭上这些气泡的顺风车，把它们当作前往细胞蛋白质工厂的单程车票。
Then, instead of being digested, it breaks out—putting its genome right where it will be translated and copied to make new viruses.
然后，它没有被消化，而是分解出它的基因组，在那里它将被转译和复制，以制造新的病毒。
It's possible the new coronavirus can do all this more efficiently than other viruses—at least, it seems to in some cultured cells.
在这一方面，这种新型冠状病毒可能比其他病毒更高效——至少，在一些人工培养的细胞中是这样。
That could help explain how it's able to copy itself so quickly. But again, this is more of a lead than a conclusion at this point.
这可以帮助解释它如何能复制得如此迅速。但这只是引论而不是结论。
Finally, if all that's not enough, the new virus might replicate faster and spread from people who aren't sick
最终，如果这还不够，这种新型病毒可能会复制更快，并从没有患病的人身上传播，
because it's also better at evading the immune system. For example, its spike protein has extra binding sites for sugars
因为它也能更好地避开免疫系统。例如，其刺突蛋白有额外的糖结合位点，
which could help "hide" important parts that the immune system would normally recognize.
可以帮助隐藏免疫系统通常可以辨别的重要部分。
But also, the virus's genome contains the blueprints for about two dozen proteins that aren't directly involved in building new viruses.
但是这种病毒的基因组中含有大约24种蛋白质的蓝图，这些蛋白质与制造新病毒没有直接关系。
Many of these probably help it dodge the cell's virus detectors —but we don't know a whole lot about them yet.
其中许多可能帮助它避开细胞的病毒探测器——但我们对它们还不是很了解。
What we do know is that there are nearly 400 specific differences between the proteins of SARS-CoV-1 and SARS-CoV-2,
我们所知道的是，SARS-CoV-1和SARS-CoV-2的蛋白质之间存在近400个特异性差异，
most of which are in these other proteins. So there's a lot more to look at. So, we don't know all of the reasons this virus is so contagious.
其中大部分存在于这些其他蛋白质中。所以要发现的还有很多。我们不知道这种病毒传染性极强的所有原因。
But we do know enough to follow up on some promising leads. And doing that won't just help answer the question in the title of this video.
但我们确实掌握了足够的信息来跟进一些有希望的线索。这样做不仅有助于回答视频题目中的问题。
It'll also help doctors hunt down the most effective treatments and point researchers towards the best vaccine targets.
还将帮助医生寻找最有效的治疗方法，并为研究人员指出最佳的疫苗靶点。
So, really, understanding what makes this virus so infectious will help us figure out how best to defeat it.
所以，理解是什么让这种病毒如此具有传染性，将帮助我们找到最好的战胜它的方法。
One way to sharpen the reasoning skills that get us to answers is to study logic.
提高我们寻找答案的推理能力的一个方法就是学习逻辑。
Because logic is not just something for Mr. Spock to go on about --it's a whole discipline that forms the basis for mathematical reasoning.
因为逻辑不仅仅是Spock先生所研究的东西——还是构成数学推理基础的一门完整的学科。
Brilliant offers an introductory course on logic, and if you like it, you can also take Logic part II.
Brilliant提供逻辑学入门课程，如果你喜欢，你也可以选修逻辑学第二部分。
Brilliant's courses in math, computer science, engineering, and more all aim to help you hone your scientific thinking skills.
Brilliant的数学、计算机科学、工程学等课程都旨在帮助你磨练科学思维能力。
So if you're interested in sharpening your mind, the first 200 people to sign up at Brilliant.org/SciShow will get 20% off the annual Premium subscription.
所以，如果你想让自己的思维更敏捷，前200名注册用户可以享受20%的年费优惠。
