Legionnaires' Disease Associated with a Hospital Water System: A Cluster of 24 Nosocomial Cases

Abstract

Over 10 mo. 24 cases of Legionnaires'' disease pneumonia occurred among patients admitted to an Iowa [USA] hospital, most of whom were immunosuppressed. Eleven patients died. Twenty-one were admitted to a recently completed hospital addition, 16 of these to a new hematology-oncology unit. Legionella pneumophila serogroup 1 was isolated from the patients, water outlets and hot water in the new addition. Water quality variables in the hospital addition were adequate. Shock chlorination, temporary elevation of the hot water temperature and continuous chlorination of hospital water decreased the frequency of isolation of Legionella. Water use by patients in the hematology-oncology unit was restricted until the water was free of Legionella. The incidence of Legionnaires'' disease decreased. Indirect evidence supports a hypothesis of water-borne disease in this cluster of cases. Current variables of acceptable water potability may not guarantee water free of L. pneumophila.