When I talk about my book A Planet of Viruses, people often ask me if there are any viruses that are actually good for you. In an Ebola-obsessed age, it may be hard to imagine how the answer could be yes. But–yes! Or, at least, possibly yes. In my New York Times column this week, I write about a provocative new study that suggests a virus can play the same nurturing role as the microbiome, encouraging the growth of a healthy gut and a robust immune system. Check it out.