Disinfection is the reduction in the number of bacteria, viruses, or fungi to a desired concentration. Sterilization, or the complete elimination of all microorganisms, is generally not needed or in most cases not possible.

Disinfection and sterilization are essential for ensuring that medical and surgical instruments do not transmit infectious pathogens to patients. Because sterilization of all patient-care items is not necessary, health-care policies must identify, primarily on the basis of the items’ intended use, whether cleaning, disinfection, or sterilization is indicated.