When a virus attacks your body, your body works hard to get rid of it.

当病毒攻击你的身体时，你的身体会努力摆脱它。

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You catch a cold when a virus infects your upper respiratory system.

当上呼吸系统感染了病毒，人就会得感冒。

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They may be harmless, but you never know when a virus might be attached and ready to pounce.

他们可能没有什么威胁，但是你也无法预料什么时候会有病毒携带甚至准备袭击你的电脑。

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He says the companies that make vaccines cannot really do much when they have a virus that does not grow well.

VOA: special.2009.11.24

The other thing that it does is that when a virus is inside these cells making its proteins, some of those proteins get processed or digested into small fragments that are themselves antigens.

HC的另一项作用是,当病毒在细胞内表达蛋白时,一些蛋白被加工,或者,分解成小片段而成为抗原

耶鲁公开课 - 生物医学工程探索课程节选

And they did that by intentionally infecting calves, by harvesting their skin when they were at a certain point of the disease, and by isolating the virus from the skin of the calves.

他们有意感染很多小牛,当小牛疾病发展到一定程度,就收割牛皮,然后把病毒从牛皮里分离出来

耶鲁公开课 - 生物医学工程探索课程节选

Botnets start when a virus infects a computer, either through spam or an infected web page.

BBC: Two million US PCs recruited to botnets

For example, hives are sometimes blamed on a certain food when a virus was the actual cause, he added.

NPR: Study: Food, Skin Allergies Increasing In Children

When a virus infects a computer with a throttle, a huge backlog of requests develops within a few seconds.

ECONOMIST: A new way of thwarting viral epidemics on computers