A surgical site infection is an infection that occurs in the wound created by an invasive surgical procedure. There are three main types of SSI: superficial incisional, deep incisional, and organ/space. Risk factors include patient comorbidities, local wound factors, and microbial factors such as wound class. Prevention focuses on pre-op skin preparation and antibiotics, aseptic technique during surgery, and clean wound care post-op. Severe infections can progress to sepsis, severe sepsis, and multiple organ dysfunction syndrome if not properly treated.