Actions taken to prevent an undesired effect or outcome. In the health care context, “precautions” usually refers to measure taken to prevent the transmission of disease to a patient who is particularly vulnerable to infection because their immune system has broken down (such a patient is called a “compromised host”), or from a patient with an especially communicable disease. In the past, individual patients were designated as requiring special precautions, which were then taken only with respect to those patients. Gowns and gloves were worn in the patient’s room, for example, and visitors were strictly limited. With the advent of AIDS, however, universal precautions have been instituted.