The world is full of undiscovered viruses. They’re in the air we breathe, the ground we walk on, and they’re inside our bellies. For this last episode of the season, we’re exploring the mysteries of the microbes that have us surrounded. First we meet Portland State University virologist Ken Stedman, who made a wild discovery that changed what we thought a virus could be. Then, Shiraz Shah from the Copenhagen University Hospital Gentofte explains how viruses that colonize our guts during infancy may affect our health for the rest of our lives.