An iatrogenic illness or condition has been inadvertently caused by a medical test or procedure. This can be unexpected reactions to medications, accidental exposure to pathogens, or reactions to medical procedures or equipment. For instance, it is not uncommon to contract a staph infection in a hospital despite all the cleaning, disinfectants, gloves and sterile gowns that hospitals depend on. Infections may arise from a combination of the omnipresence of staph bacteria and the low resistance to infection that many patients have.