An outbreak of Pneumocystis carinii pneumonia at a pediatric hospital.

Eleven cases of Pneumocystis carinii pneumonia were diagnosed during a 3 1/2-year period at a pediatric hospital where this infection had never been identified previously despite appropriate studies. The incidence of infection was 3.0, 7.4, and 4.2 cases per 1,000 patient months in children being treated for acute leukemia, neuroblastoma, and rhabdomyosarcoma, respectively. The outbreak coincided with increased intensity of chemotherapy for these malignancies. Ten of the patients had received four or more chemotherapeutic agents within three months of the onset of infection. Because no exogenous source of the epidemic was found, latent endogenous infection activated by immunosuppression was presumed to be the ultimate cause of the outbreak. Increased intensity of chemotherapy may result in P carinii outbreaks and may be an indication for anti-Pneumocystis prophylaxis with trimethoprim/sulfamethoxazole in patients at risk.