The discovery of viruses: advancing science and medicine by challenging dogma.

The discovery of viruses in the final years of the nineteenth century represented the culmination of two decades of work on tobacco mosaic disease by three botanical scientists. Eventually their discovery led to a paradigm shift in scientific thought, but it took more than 20 years to appreciate its implications because it was inconsistent with the prevailing dogma of the time-Koch's postulates. Although these 'rules' were actually conceived of as guidelines upon which to establish microbial causality and their implementation resulted in many new discoveries, they also had the unintended effect of limiting the interpretation of novel findings. However, by challenging existing dogma through rigorous scientific observation and sheer persistence, the investigators advanced medicine and heralded new areas of discovery.