The periods of remission can last from weeks to years."
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Springer - Mimics of Ulcerative Colitis...
"Infectious colitides such as Clostridia difficile, hemorrhagic E. coli, Campylobacter, Aeromonas, and Salmonellosis can often present as severe ulcerative colitis. Other infectious pathogens, which also need to be included in the differential diagnoses, include Amebiasis, Shigellosis, Cytomegalovirus, and Rotavirus.