病毒是什么？
What is a virus?
流行性感冒，埃博拉病毒，普通感冒，艾滋病毒，麻疹。
Influenza. Ebola. The common cold. HIV/AIDS. Measles.
病毒会导致上述疾病，或者更多。有些很严重，有些则不然。不论怎样，病毒都是我们生活中的一部分。
Viruses cause these diseases - and many more. Some are serious. Others, not so much. For better or worse, viruses are part of life.
要知道病毒虽然寄居在我们身上并不意味着它就是活的，这可能会令很多人大吃一惊。病毒仅在宿主的细胞内进行复制。它的宿主可能是动物、植物，也可能是细菌、真菌等等。
It surprises many people to learn that viruses "live" in us but aren't technically alive. Viruses can replicate only inside the cells of their host. A host can be an animal, plant, bacterium or fungus.
通常我们会把病毒与它的另一个家庭成员-细菌混淆，其区别就是病毒小得多多了。病毒身穿蛋白质外套，内含脱氧核糖核酸或核糖核酸。每一个分子充当着一本说明书。其遗传信息为细胞提供指导，告诉他们什么时候该做什么。
Viruses are sometimes confused with another family of germs: bacteria. But viruses are much, much smaller. Think of a virus as a tiny package jacketed in a protein covering. Inside is either DNA or RNA. Each molecule serves as an instruction book. Its genetic information provides instructions that tell a cell what to make and when to make it.
当病毒侵入细胞内时，它会给该细胞发送一个简单的信号：复制更多的病毒！
When a virus infects a cell, it sends that cell a simple message: Make more viruses.
在这个意义上，病毒就变成了一名劫持犯，它闯入细胞，迫使其按指令行事。最终宿主细胞死掉，吐出新病毒攻击更多细胞，这就是病毒入侵细胞的整个过程。
In that sense, this virus is a hijacker. It breaks into a cell. Then it makes the cell do its bidding. Eventually, that host cell dies, spewing new viruses to attack more cells. That is how viruses sicken a host.
（顺便提一下，电脑病毒不是真正的病毒，他是一种软件，一种计算机指令。然而与真实病菌类似的是，电脑病毒也会入侵主机内部并将其劫持。）
(By the way, a computer virus isn't a real virus. It's a type of software, meaning computer instructions. Like a real virus, however, a computer virus can infect - and even hijack - its host computer.)
身体可以自行清除许多病毒，但有些病毒表现的像一个巨大挑战。能对抗病毒的药物是存在的，叫做抗病毒药。他们以不同的方式起作用，比如有的会阻止病毒侵入宿主细胞内。有的会中断病毒复制。
The body can rid itself of many viruses on its own. Other viruses may present too big a challenge. Medicines to treat viruses exist. Called antivirals, they work in different ways. Some, for example, block the entry of a virus into a host cell. Others interrupt the virus as it attempts to copy itself.
总之，病毒很难对付，那是因为它们寄生在你的细胞内部，增加了药物使用困难。（还需注意的是抗生素可能不会对病毒起什么作用）
In general, viruses can be hard to treat. That's because they live inside your cells, which shelter them from medicines. (It's also important to note that antibiotics don't work on viruses.)