In June 2012, scientists around the world simultaneously published a series of papers spearheaded by the US National Institutes of Health’s Human Microbiome Project (HMP) that characterized the fundamentals of the microbiome in healthy individuals (3). By definition, the microbiome includes all microbes in the human body: bacteria, viruses, and fungi. Most initial HMP research, however, focused on bacteria because there is a standardized and thorough protocol for isolating and characterizing bacterial genes from the slurry of DNA in human feces or saliva swabs. Viruses, in contrast, have so far been the forgotten siblings of the microbiome family. But a growing cadre of researchers argues that the human virome is probably at least as important to human health as our bacterial inhabitants.