如果这种病毒能够通过空气传播，或者如果一名感染者在不知情的情况下进入了人口密集的地区，那么埃博拉可能已经成为一种全球流行病。

If the virus had been capable of spreading through the air, or if one infected person had unknowingly entered a large population center, Ebola might have become a worldwide epidemic.

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在房屋内，充满煤烟的空气会导致可怕的呼吸道感染。

Inside homes, the sooty air causes terrible respiratory infections.

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空气传染不分疆界，并且会感染更多的人。

It will stop at no border, and it will infect much greater Numbers of people.

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But it can be acquired in the air, from patients that are from- from other individuals that are infected.

天花会通过空气传播,通过病人和其他感染者呼出的空气传播

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