Not only is the human body covered inside and out with bacteria, it is also home to a large number of viruses. "But, truth be told, a lot of viruses we harbor don't make us sick. They may even make us healthy. You'd think they'd be worth getting to know. But they're mostly a mystery to us," writes Carl Zimmer at The Loom. He notes, though, that researchers are beginning to try to solve that mystery.