Which condition is described as a systemic inflammatory response triggered by infection?

Sepsis is a life-threatening condition characterized by a systemic inflammatory response to infection. When bacteria, viruses, or fungi invade the bloodstream, the body responds with an overwhelming inflammatory response that can lead to widespread tissue damage and organ failure. This process is driven by the immune system's release of various chemical mediators, which can result in increased vascular permeability, changes in blood flow, and ultimately, shock.

In contrast, pulmonary embolism is a blockage in a pulmonary artery often caused by blood clots, not primarily due to a systemic infection. Pneumonia is an infection of the lungs that can lead to localized inflammation rather than a systemic response; while it can contribute to sepsis in severe cases, it is not described as a systemic inflammatory response in itself. Chronic obstructive pulmonary disease (COPD) is primarily a respiratory disease characterized by airflow limitation and chronic inflammation, but it is not directly triggered by infection in the same way sepsis is. Thus, sepsis is specifically defined by its systemic nature and the body's aggressive response to infectious agents.