Control of Legionella in Plumbing Systems

Legionellae are bacteria that have been identified as the cause of legionellosis. Based on a rate of about 1.2 cases of legionellosis/10,000 persons/yr (Foy et al. 1979), more than 25,000 cases of this disease are estimated to occur annually within the U.S. These cases are caused primarily by one of 23 currently recognized species of the genus Legionella. Most cases of legionnaires’ disease, the pneumonia form of legionellosis, have developed in persons who were immunosuppressed or appeared to be more susceptible because of an underlying illness, heavy smoking, alcoholism, or age (i.e., more than 50 years old). In contrast, although legionnaires’ disease has developed in some healthy persons, outbreaks involving healthy persons have been limited to the milder, nonpneumonia form of the disease called Pontiac fever.