A pathogen is a disease-causing agent. Bloodborne pathogens are organisms, such as viruses and bacteria that are carried in human blood. These organisms can cause illness, and in some cases death, after entering the blood stream of an individual.
Illnesses caused by most bloodborne pathogens is relatively rare: The human body uses a variety of defenses, including the skin, dense cellular material, the lymph system, and a complex disease-fighting network of cells within the blood itself to protect the bloodstream against any invasions from the outside. However, if the infected blood of one individual directly enters the bloodstream of another individual, the infection can be transmitted.
Potentially infectious human body fluids include blood, semen, vaginal secretions, urine, feces, vomit, saliva, and any body fluids containing or suspected of containing blood.