The Pathology of Viral Infections

If you were to ask, "Biologically speaking, what are humans made of?", almost everyone would reply "Human cells and molecules, of course." This seemingly logical answer, however, does not truly capture the diversity of the human organism. Over the past couple of decades scientists have discovered that humans are a collective of cohabitating human, bacteria, and fungi cells along with countless numbers of viruses. Collectively, these microorganisms are referred to as the microbiome (Lederberg and McCray, The Scientist 15:8, 2001). The most recent estimates suggest the biological material from these microorganisms makes up as much as half of every human. Considering the size of the microbiome, it is not surprising that humans share an intimate relationship with viruses since they will be found wherever life exists.