Sporadic Community-Acquired Legionnaires' Disease and Contaminated Domestic Hot Water Supplies

Abstract

Domestic water supply, and particularly electric hot water systems, have been associated with Legionella colonization, and potential clinical implications have been suggested. In an effort to establish a link between sporadic legionellosis and hot water system colonization, patients hospitalized with documented sporadic community-acquired legionellosis (CAL) at Maisonneuve-Rosemont hospital in Monteral, Canada, were prospectively investigated. Only three culture-confirmed cases of CAL were established during the 30-month prospective epidemiological surveillance study. An epidemiological link between those patients' pneumonia and their contaminated home hot water tank was established in only one patient. The first water samples from this patient's home were obtained 45 days after the patient's admission to the hospital. Additional water samples from the hot water tank taken 14 weeks after the patient's admission showed a persistence in the system of the same isolate, underlying the long-term sustained colonization of contaminated hot water systems. Debilitation by chronic alcoholism and smoking, as well as recent plumbing repair and frequent exposures to aerosols generated from the shower head, likely played predominant physiopathological roles in the patient's acquisition of Legionnaires' disease. A study by the authors focused on severe CAL that required hospitalization and found a very low incidence linked to contaminated hot water tanks. Individual risk factors (i.e., smoking, age, chronic lung diseases) and immunoincompetence rather than environmental factors likely represent the major contributing factors in the acquisition of severe sporadic Legionnaires' disease.