The genome has been mapped. The systems studied. Everything is known. Just like theworld, they tell themselves. The mysteries have all been solved. There is nothing that could possibly lurk beyond what humans can apprehend. They are wrong. When a virus slips its way into a body, sometimes that body reacts in unexpected ways. It marshals all its defenses and attacks; after all, the virus does not mean well—and then, sometimes, even when the intruder is gone, it keeps attacking. It doesn’t even remember why. […]