Hospital medicine is a medical specialty that exists in some countries as a branch of family medicine or internal medicine, dealing with the care of acutely ill hospitalized patients. Physicians whose primary professional focus is caring for hospitalized patients only while they are in the hospital are called hospitalists. Originating in the United States, this type of medical practice has extended into Australia and Canada. The vast majority of physicians who refer to themselves as hospitalists focus their practice upon hospitalized patients. Hospitalists are not necessarily required to have separate board certification in hospital medicine.