A nosocomial infection - also called infection can be defined as An infection occurring in a patient in a hospital or other health care facility in whom the infection was not present or incubating at the time of admission. This includes infections acquired in the hospital but appearing after discharge, and also occupational infections among staff of the facility. Patient care is provided in facilities which range from highly equipped clinics and technologically advanced university hospitals to front-line primary health centers with only basic facilities. Despite progress in public health and hospital care, infections continue to develop in hospitalized patients, and may also affect hospital staff. Many factors promote infection among hospitalized patients: decreased immunity among patients the increasing variety of medical procedures and invasive techniques creating potential routes of infection and the transmission of drug-resistant bacteria among crowded hospital populations, where poor infection control practices may facilitate transmission.