Cryptosporidiosis in patients at a large teaching hospital.

In 1984, all stool samples submitted to a microbiology laboratory (n = 2,197) from a predominantly hospital-based population were examined for Cryptosporidium oocysts after Ziehl-Neelsen staining, but only 0.5% were positive. We suggest that in low-incidence areas, individual laboratories examine stool samples for this organism only in immunosuppressed patients and those in whom symptoms persist.