Carl Zimmer: Planet of Viruses

Consider these facts from Carl Zimmer's book, A Planet of Viruses: If you put all the viruses in the ocean on a scale, they would equal the weight of 75 million blue whales. And if you lined up all those viruses end to end, “they would stretch out past the nearest 60 galaxies.”

In 17th century England, Zimmer writes, cures for the rhinovirus, or the common cold, included a blend of gunpowder and eggs and fried cow dung and suet. Today, he says, doctors have little more to offer a person that...