This document discusses surgical site infections (SSIs). It begins by providing some historical context on efforts to reduce SSIs dating back to the 19th century. It then notes that while medicine has advanced, SSIs remain a leading cause of morbidity and mortality. The document goes on to discuss the epidemiology of SSIs, including common pathogens and outcomes like increased costs and mortality. It covers diagnosis of SSIs and challenges in diagnosing infections involving implants. The rest of the document discusses pathogenesis of SSIs from both endogenous and exogenous sources, as well as risk factors including patient characteristics, procedural factors, and postoperative issues.