Legionnaires' disease associated with a hospital water system. A five-year progress report on continuous hyperchlorination
Helms, C.M.; Massanari, R.M.; Wenzel, R.P.; Pfaller, M.A.; Moyer, N.P.; Hall, N.
JAMA 259(16): 2423-2427
1988
ISSN/ISBN: 0098-7484 PMID: 3352131 Document Number: 310353
In 1981, sixteen cases of nosocomial legionellosis occurred among 456 patients admitted to a new hematology-oncology unit (35 per 1000 admissions). Monoclonal antibody typing and restriction endonuclease plasmid analysis identified a unique strain (09,04) of Legionella pneumophila serogroup 1 isolated from both patients and water outlets. Continuous hyperchlorination of the hot and cold water began in January 1982, and chlorine levels of 3 to 5 mg/L have been maintained most recently. Water samples have been consistently negative for Legionella for more than five years. Four sporadic cases of nosocomial legionellosis have occurred in the hematology-oncology unit during the same period (one per 1000 admissions) associated with a different strain of L pneumophila serogroup 1 (09,00). The environmental reservoir(s) of L pneumophila serogroup 1 in these cases has not been identified. Levels of trihalomethanes (potential carcinogens) were high (greater than 100 micrograms/L) when chlorine levels of hot water exceeded 4 mg/L. Some corrosion damage to the water distribution system has occurred: the average number of leaks per month increased steadily from zero in 1982 to 5.2 in 1986. The chlorinator installation costs were +75,800, and annual operation expenses were +12,500. Continuous hyperchlorination is a promising but still experimental technique for control of nosocomial legionellosis. In our experience, epidemic disease has been controlled, but sporadic cases have continued to occur.