Example: Asymptomatic colonization with Clostridium difficile . Clostridium difficile diarrhea (CDAD) is the most common nosocomial diarrhea, prolonging hospitalization and for some patients leading to colectomy or death. . Patients are typically exposed to CD in a hospital setting, but may also become exposed in the community . After exposure, an estimated 2/3 patients become asymptomatic carriers. There is a concern that asymptomatic colonization may play a greater role in spreading CD infection than previously thought . A large, multi-centre Canadian study examined the risk of asymptomatic colonization at admission to hospital. They also examined various risk factors for asymptomatic colonization, including patient and pathogen characteristics (Kong et al, Am J Inf Control, 2015)