Viruses are the world's most abundant life form, and now, when humanity is in the midst of a close encounter with their immense power, perhaps the most feared. But do we understand viruses? Possibly the most enigmatic of living things, they are sometimes not considered a life form at all. Everything about them is extreme, including the reactions they evoke. However, for every truism about viruses, the opposite is also often true. So complex and diverse...