Medical staff are confronted on a daily basis with the risk of viral or bacterial contamination through contact with blood or other biological fluids. Contamination with the HIV or hepatitis B and C viruses constitutes a major preoccupation for healthcare workers.

The term Blood Exposure Accidents (BEAs) applies to "any percutaneous exposure or exposure via damaged skin or mucous membranes to blood or a blood-soiled biological liquid".

Blood Exposure Accidents can thus be subdivided into two groups :

•  Percutaneous Injuries (PIs) which typically involve a needle-stick injury or skin cut. PIs in general (and those involving hollow needles in particular) are considered to be the most serious BEAs in terms of viral transmission.

•  Mucous Membrane and non-intact Skin Exposures (MMSEs) , which can occur due to splashes or via insufficiently protective equipment (latex gloves, etc.).