Sepsis is a life-threatening condition that occurs when an infecting agent -- such as bacteria, virus, or fungus -- gets into a person's bloodstream. The infection activates the entire immune system, which then sets off a chain reaction of events that can lead to uncontrolled inflammation in the body. This whole-body response to infection produces changes in temperature, blood pressure, heart rate, white blood cell count, and breathing. More severe forms of sepsis can also cause organ dysfunction or shock. Sepsis requires immediate medical care. Follow the links below to find WebMD's comprehensive coverage about how sepsis is contracted, what it looks like, how to treat it, and much more.