Cryptosporidiosis: an unrecognized cause of diarrhea in elderly hospitalized patients.

Human infection with Cryptosporidium species has been increasingly noted in the past decade. We conducted a broad-based longitudinal review in a community setting and found that a Cryptosporidium species was detected in one-third of the specimens screened over a 5-year period. Thirty-six patients were identified, comprising three distinct clinical groups: persons with human immunodeficiency virus (HIV) infection (18 patients); young, otherwise healthy persons (5 patients); and, surprisingly, chronically ill elderly persons (13 patients). In six (46%) of the 13 elderly patients, both Cryptosporidium and Clostridium difficile toxin was identified, suggesting that Cryptosporidium may be a copathogen in some instances of nosocomial diarrhea. Acquisition in an institutional setting was suspected for nine (69%) of the elderly and three (17%) of the HIV-infected patients. Elderly patients with chronic illnesses constitute a newly recognized category of persons at risk for cryptosporidial infection. In this group cryptosporidiosis may be far more common than previously recognized, may be acquired institutionally, and can mimic and occur with Clostridium difficile-associated diarrhea.