1) The presence of pathogenic microorganisms or their toxins in tissues or in the blood. Systemic disease caused by the spread of the microorganisms via the circulating blood is commonly called SEPTICEMIA. (From Stedman, 25th ed)

2) Invasion of the bloodstream by virulent microorganisms (as bacteria, viruses, or fungi) from a focus of infection that is accompanied by acute systemic illness -- called also blood poisoning.