Nosocomial Legionnaires' disease uncovered in a prospective pneumonia study.

Most hospitals have yet to record a case of nosocomial legionnaires' disease; the importance of isolation of Legionella pneumophila in the water system of such an institution is unclear. We undertook a prospective pneumonia study in tandem at a veterans hospital where legionnaires' disease was known to be endemic and a community teaching hospital where legionnaires' disease had never been documented. Legionella serological tests were performed on all patients with pneumonia; selective culture media and direct fluorescent antibody testing for Legionella were made readily available. Simultaneous environmental surveys for Legionella were performed. At the community hospital, we discovered that 64% of sites in the water distribution system yielded L pneumophila and that 14.3% of nosocomial pneumonias were legionnaires' disease. The epidemiologic implications of these findings are discussed. Options concerning case detection and eradication measures in the face of hospital water contamination with L pneumophila are presented.