sepsis is a very dangerous disease that occurs when an infection goes wrong. normally the immune system of the body is able to fight the germs and overcome the infection, but in sepsis something goes wrong. the pathogen was at some point able to get into the blood or tissues. the term sepsis is frequently used to refer to septicemia (blood poisoning). septicemia is only one type of sepsis. bacteremia specifically refers to the presence of bacteria in the bloodstream (viremia and fungemia are the terms used for viruses and fungi). a sepsis is a medical emergency, as it can put the life in danger, if it is not acted on.