- An extreme immune response to infection that can lead to tissue damage, organ failure, or death if not treated right away. Sepsis occurs when chemicals released by the body into the bloodstream to fight an infection trigger inflammation, blood clots, and leaky blood vessels throughout the body. This reduces blood flow and the amount of oxygen and nutrients to the body’s tissues and organs. Bacterial infections are the most common cause of sepsis, but it can also be caused by other types of infections. Signs and symptoms may include fever or very low body temperature, chills, fast heart rate, rapid or trouble breathing, warm or sweaty skin, confusion, and severe pain. Sepsis can occur in anyone with an infection, but is more common in older adults, infants, pregnant women, or people who are in the hospital or who have a weakened immune system, chronic medical condition, or severe injury or illness.