Life-threatening organ failure caused by a dysregulated host response, often to an infection.

In informal use, sepsis often refers to a bloodstream bacterial infection (BSI), and the term is sometimes used synonymously with septicaemia.

More than 19 million cases of sepsis and 5 million sepsis-related deaths are estimated to occur each year, most of them in low- and middle-income countries. Sepsis causes nearly half a million deaths in the newborn period each year. Globally, antimicrobial resistance contributes to one-third of neonatal sepsis deaths.