In 2020, an invisible germ—a virus—wholly upended our lives. We’re most familiar with the viruses that give us colds or Covid-19. But viruses also cause a vast range of other diseases, including one disorder that makes people sprout branch-like growths as if they were trees. Viruses have been a part of our lives for so long that we are actually part virus: the human genome contains more DNA from viruses than our own genes. Meanwhile, scientists are discovering viruses everywhere they look: in the soil, in the ocean, even in deep caves miles underground. Fully revised and updated, with new illustrations and a new chapter about coronaviruses and the spread of Covid-19, this third edition of Carl Zimmer’s A Planet of Viruses pulls back the veil on this hidden world. It presents the latest research on how viruses hold sway over our lives and our biosphere, how viruses helped give rise to the first life-forms, how viruses are producing new diseases, how we can harness viruses for our own ends, and how viruses will continue to control our fate as long as life endures.