这就是为什么许多病毒，如麻疹，只会使我们生病一次。
This is why many viruses, such as measles, make us ill only once.
它也试图找出我们对生病怎样反应，为什么这样反应。
It also tries to figure out how and why we respond to sickness.
Ellison说道，“我们的生物学是进化的权衡结果，所以了解这些历史和过程中的冲突可以帮助医学家们理解为什么我们会生病以及我们怎样才能保持健康。”
Our biology is the result of many evolutionary tradeoffs, and understanding these histories and conflicts can really help the physician understand why we get sick and what we might do to stay healthy.
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