Potable water as a source for legionellosis.

Several lines of evidence have been examined in attempts to implicate potable water as a source for legionellosis. Success has been mixed. The strongest evidence has been the similarity of strains recovered from patients and from potable water and the cessation of outbreaks following institution of measures to eradicate Legionella from potable water systems. Epidemiologic efforts to identify the effective mode of exposure to water (e.g. ingestion) have been remarkably unsuccessful. Although L pneumophila can clearly be acquired on occasion from potable water, the proportion of cases traceable to this source is unknown, as is the role of potable water as a source of infection by other Legionellae. Hyperchlorination, raising hot water temperatures to greater than 55 degrees C, and replacing rubber gaskets are useful methods for controlling outbreaks of legionellosis traced to potable water systems but are not yet justified as routine preventative methods in the absence of such an outbreak.