Risk of Cryptosporidium parvum transmission between hospital roommates

of a patient with Cryptosporidium infection. No patients with Cryptosporidium were identified among the 37 exposed roommates, and 1 case was identified among the 37 unexposed room- mates. The risk ratio for chronic diarrhea was 0.80 (95% confidence interval (CI), 0.23-2.75) and for death was 1.04 (95% CI, 0.75-1.44). These results suggest that isolation of adult patients with Cryptosporidium diarrhea is not necessary to prevent roommate-to-roommate transmis- sion of Cryptosporidium. Infection with Cryptosporidium parvum causes prolonged and severe diarrhea in immunodeficient persons. It is estimated that the annual rate of Cryptosporidium infection is 5%-10% among patients with AIDS (1), and patients with low CD4 cell counts have greatly increased risk (2). Hospitalized AIDS patients with chronic cryptosporidial diarrhea may contaminate the hospital room in which they are located, posing a potential risk of trans- mission to other persons with advanced AIDS. Although stud- ies have been performed that show the nosocomial transmission of Cryptosporidium (3, 4), the risk of disease associated with sharing a hospital room with a patient who has diarrhea at- tributable to Cryptosporidium has not been quantified. Highly active antiretroviral therapy (HAART) is the only effective treatment for cryptosporidiosis in persons infected with HIV. In our hospital, HAART was not administered until late 1996. Before 1996, cryptosporidiosis was seen in 5%210% of patients with AIDS, and hospitalized patients with Crypto- sporidium posed a potential risk for transmission of the disease to their hospital roommates. In the Grady Memorial Hospital Special Immunity Service (GMH SIS ward), the roommates of patients with Cryptosporidium infection were likely to have ad