“Over the years of the podcast, we have often struggled with questions of why: why pathogens act the way they do, why certain people get sick while others don’t, or why we know little about some diseases. This episode is no exception – sepsis certainly inspires many “whys”. But for perhaps the first time on the pod, we find ourselves grappling not only with “why?” but also with “what?”. What, indeed, is sepsis? Ask a dozen doctors and you may get a dozen different answers. Our first goal for this episode is to sift through the various definitions of sepsis and what we know about its pathology to get a firm handle on this deadly consequence of infection. We then turn our sights to a thrilling period of sepsis history – Joseph Lister and his carbolic acid spray – before attempting to address the status of sepsis around the world today. By the end of the episode, your picture of sepsis may not be crystal clear, but hopefully the edges are a little less blurry.