Bacteremia is the presence of bacteria in the bloodstream. Bacteremia occurs for a few hours after many surgical procedures and may also occur with infections such as tonsillitis.

In people with abnormal heart valves, due to a congenital defect or to scarring from previous rheumatic fever, the bacteria may cause endocarditis (inflammation of the heart lining and valves). If bacteremia affects a person whose immune system has been compromised by illness or a major surgical operation, sepsis and septic shock may follow.